/
auth48-rfc8313-diff.html
2212 lines (1759 loc) · 191 KB
/
auth48-rfc8313-diff.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<html><head><title>wdiff rfc8313.original rfc8313.txt</title></head><body>
<pre>
<strike><font color='red'>MBONED Working Group</font></strike>
<strong><font color='green'>Internet Engineering Task Force (IETF)</font></strong> P. Tarapore, Ed.
<strike><font color='red'>Internet-Draft</font></strike>
<strong><font color='green'>Request for Comments: 8313</font></strong> R. Sayko
<strike><font color='red'>Intended status:</font></strike>
<strong><font color='green'>BCP: 213 AT&T
Category:</font></strong> Best Current Practice <strike><font color='red'>AT&T
Expires: May 3, 2018</font></strike> G. Shepherd
<strong><font color='green'>ISSN: 2070-1721</font></strong> Cisco
T. Eckert, Ed.
Huawei
R. Krishnan
SupportVectors
<strike><font color='red'>October 30,</font></strike>
<strong><font color='green'>December</font></strong> 2017
Use of Multicast <strike><font color='red'>Across Inter-Domain</font></strike> <strong><font color='green'>across Inter-domain</font></strong> Peering Points
<strike><font color='red'>draft-ietf-mboned-interdomain-peering-bcp-14</font></strike>
Abstract
This document examines the use of <strike><font color='red'>Source Specific</font></strike> <strong><font color='green'>Source-Specific</font></strong> Multicast (SSM)
across inter-domain peering points for a specified set of deployment
scenarios. The <strike><font color='red'>objective is</font></strike> <strong><font color='green'>objectives are</font></strong> to <strong><font color='green'>(1)</font></strong> describe the setup process for
multicast-based delivery across administrative domains for these
scenarios and <strong><font color='green'>(2)</font></strong> document supporting functionality to enable this
process.
Status of This Memo
This <strike><font color='red'>Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working</font></strike> <strong><font color='green'>memo</font></strong> documents <strong><font color='green'>an Internet Best Current Practice.
This document is a product</font></strong> of the Internet Engineering Task Force
(IETF). <strike><font color='red'>Note that other groups may also distribute
working documents as Internet-Drafts. The list</font></strike> <strong><font color='green'>It represents the consensus</font></strong> of <strike><font color='red'>current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid</font></strike> <strong><font color='green'>the IETF community. It has
received public review and has been approved</font></strong> for <strike><font color='red'>a maximum</font></strike> <strong><font color='green'>publication by the
Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of RFC 7841.
Information about the current status</font></strong> of <strike><font color='red'>six months</font></strike> <strong><font color='green'>this document, any errata,</font></strong>
and <strong><font color='green'>how to provide feedback on it</font></strong> may be <strike><font color='red'>updated, replaced, or obsoleted by other documents</font></strike> <strong><font color='green'>obtained</font></strong> at <strike><font color='red'>any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 3, 2018.</font></strike>
<strong><font color='green'>https://www.rfc-editor.org/info/rfc8313.</font></strong>
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of Inter-domain Multicast Application Transport . . 5
3. Inter-domain Peering Point Requirements for Multicast . . . . 6
3.1. Native Multicast . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>7</font></strike> <strong><font color='green'>6</font></strong>
3.2. Peering Point Enabled with GRE Tunnel . . . . . . . . . . 8
3.3. Peering Point Enabled with <strike><font color='red'>an</font></strike> AMT - Both Domains Multicast
Enabled . . . . . . . . . . . . . . . . . . . . <strong><font color='green'>. . . . .</font></strong> 10
3.4. Peering Point Enabled with <strike><font color='red'>an</font></strike> AMT - AD-2 Not Multicast
Enabled . . . . . . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>12</font></strike> <strong><font color='green'>11</font></strong>
3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels <strike><font color='red'>Through</font></strike> <strong><font color='green'>through</font></strong>
AD-2 . . . . . . . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>14</font></strike> <strong><font color='green'>13</font></strong>
4. Functional Guidelines . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>16</font></strike> <strong><font color='green'>15</font></strong>
4.1. Network Interconnection Transport Guidelines . . . . . . 16
4.1.1. Bandwidth Management . . . . . . . . . . . . . . . . 16
4.2. Routing Aspects and Related Guidelines . . . . . . . . . 18
4.2.1. Native Multicast Routing Aspects . . . . . . . . . . 19
4.2.2. GRE Tunnel over Interconnecting Peering Point . . . . 19
4.2.3. Routing Aspects with AMT Tunnels . . . . . . . . . . 20
4.2.4. Public Peering Routing Aspects . . . . . . . . . . . 22
4.3. <strike><font color='red'>Back Office</font></strike> <strong><font color='green'>Back-Office</font></strong> Functions - Provisioning and Logging
Guidelines . . . . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>23</font></strike> <strong><font color='green'>24</font></strong>
4.3.1. Provisioning Guidelines . . . . . . . . . . . . . . . 24
4.3.2. <strike><font color='red'>Interdomain</font></strike> <strong><font color='green'>Inter-domain</font></strong> Authentication Guidelines . . . . . . . <strike><font color='red'>.</font></strike> 25
4.3.3. <strike><font color='red'>Log Management</font></strike> <strong><font color='green'>Log-Management</font></strong> Guidelines . . . . . . . . . . . . . . 26
4.4. Operations - Service Performance and Monitoring
Guidelines . . . . . . . . . . . . . . . . . . . . . . . 27
4.5. Client Reliability <strike><font color='red'>Models/Service</font></strike> <strong><font color='green'>Models / Service</font></strong> Assurance Guidelines <strike><font color='red'>.</font></strike> 29
4.6. Application Accounting Guidelines . . . . . . . . . . . . 29
5. Troubleshooting and Diagnostics . . . . . . . . . . . . . . . <strike><font color='red'>29</font></strike> <strong><font color='green'>30</font></strong>
6. Security Considerations . . . . . . . . . . . . . . . . . . . <strike><font color='red'>30</font></strike> <strong><font color='green'>31</font></strong>
6.1. DoS <strike><font color='red'>attacks</font></strike> <strong><font color='green'>Attacks</font></strong> (against <strike><font color='red'>state</font></strike> <strong><font color='green'>State</font></strong> and <strike><font color='red'>bandwidth)</font></strike> <strong><font color='green'>Bandwidth)</font></strong> . . . . . . . . <strike><font color='red'>30</font></strike> <strong><font color='green'>31</font></strong>
6.2. Content Security . . . . . . . . . . . . . . . . . . . . 32
6.3. Peering Encryption . . . . . . . . . . . . . . . . . . . 34
6.4. Operational Aspects . . . . . . . . . . . . . . . . . . . <strike><font color='red'>34</font></strike> <strong><font color='green'>35</font></strong>
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . <strike><font color='red'>35</font></strike> <strong><font color='green'>36</font></strong>
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37
9. <strike><font color='red'>Acknowledgments . . . . . . . . .</font></strike> <strong><font color='green'>References</font></strong> . . . . . . . . . . . . . . <strike><font color='red'>37
10. Change log [RFC Editor: Please remove]</font></strike> . . . . . . . . . . . 37
<strike><font color='red'>11.</font></strike>
<strong><font color='green'>9.1. Normative</font></strong> References . . . . . . . . . . . . . . . . . . <strong><font color='green'>37
9.2. Informative References</font></strong> . . . . . . . <strike><font color='red'>39
11.1. Normative References</font></strike> . . . . . . . . . . <strong><font color='green'>39
Acknowledgments</font></strong> . . . . . . . . <strike><font color='red'>39
11.2. Informative References</font></strike> . . . . . . . . . . . . . . . . . <strike><font color='red'>40</font></strike> <strong><font color='green'>39</font></strong>
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . <strike><font color='red'>41</font></strike> <strong><font color='green'>40</font></strong>
1. Introduction
Content and data from several types of applications (e.g., live video
streaming, software downloads) are well suited for delivery via
multicast means. The use of multicast for delivering such content or
other data offers significant savings <strong><font color='green'>in terms</font></strong> of utilization of
resources in any given administrative domain. End <strike><font color='red'>user</font></strike> <strong><font color='green'>User (EU)</font></strong> demand
for such content or other data is growing. Often, this requires
transporting the content or other data across administrative domains
via inter-domain peering points.
The <strike><font color='red'>objective</font></strike> <strong><font color='green'>objectives</font></strong> of this <strike><font color='red'>Best Current Practices</font></strike> document <strike><font color='red'>is</font></strike> <strong><font color='green'>are</font></strong> twofold:
o Describe the technical process and establish guidelines for
setting up multicast-based delivery of application content or
other data across inter-domain peering points via a set of
use
<strike><font color='red'>cases.</font></strike> <strong><font color='green'>cases (where "Use Case 3.1" corresponds to Section 3.1,
"Use Case 3.2" corresponds to Section 3.2, etc.).</font></strong>
o Catalog all required <strong><font color='green'>exchanges of</font></strong> information <strike><font color='red'>exchange</font></strike> between the
administrative domains to support multicast-based delivery. This
enables operators to initiate necessary processes to support
inter-domain peering with multicast.
The scope and assumptions for this document are as follows:
o Administrative Domain 1 (AD-1) sources content to one or more <strike><font color='red'>End
Users (EUs)</font></strike> <strong><font color='green'>EUs</font></strong>
in one or more Administrative Domain 2 <strike><font color='red'>(AD-2).</font></strike> <strong><font color='green'>(AD-2) entities.</font></strong> AD-1 and
AD-2 want to use IP multicast to allow <strike><font color='red'>supporting</font></strike> <strong><font color='green'>support for</font></strong> large and
growing EU <strike><font color='red'>populations</font></strike> <strong><font color='green'>populations,</font></strong> with <strong><font color='green'>a</font></strong> minimum amount of duplicated
traffic to send across network links.
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> This document does not detail the case where EUs are
originating content. To support that additional service, it is
recommended <strike><font color='red'>to use</font></strike> <strong><font color='green'>that</font></strong> some method (outside the scope of this
document) <strong><font color='green'>be used</font></strong> by which the content from EUs is transmitted
to the application in AD-1 <strike><font color='red'>that this document refers to as the
multicast source</font></strike> and <strike><font color='red'>let it</font></strike> <strong><font color='green'>AD-1 can</font></strong> send out the traffic as
IP multicast. From that point on, the descriptions in this
document apply, except that they are not complete because they
do not cover the transport or operational aspects of the leg
from <strong><font color='green'>the</font></strong> EU to AD-1.
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> This document does not detail the case where AD-1 and AD-2 are
not directly connected to each other <strike><font color='red'>but only</font></strike> <strong><font color='green'>and are instead connected</font></strong>
via one or more
<strike><font color='red'>AD-3 (transit providers).</font></strike> <strong><font color='green'>other ADs (as opposed to a peering point) that
serve as transit providers.</font></strong> The cases described in this
document where tunnels are used between AD-1 and AD-2 can be
applied to such scenarios, but SLA ("Service Level Agreement") <strike><font color='red'>control</font></strike>
<strong><font color='green'>control,</font></strong> for
<strike><font color='red'>example</font></strike> <strong><font color='green'>example,</font></strong> would be different. <strike><font color='red'>Other additional</font></strike> <strong><font color='green'>Additional</font></strong> issues
will likely exist as well in such scenarios. This <strong><font color='green'>topic</font></strong> is
<strong><font color='green'>left</font></strong> for further study.
o For the <strike><font color='red'>purpose</font></strike> <strong><font color='green'>purposes</font></strong> of this document, the term "peering point" refers
to a network connection ("link") between two administrative
network domains over which traffic is exchanged between them.
This is also referred to as a Network-to-Network Interface (NNI).
Unless otherwise noted, <strike><font color='red'>the peering point</font></strike> <strong><font color='green'>it</font></strong> is assumed <strike><font color='red'>to be</font></strike> <strong><font color='green'>that the peering point is</font></strong> a
private peering point, where the network connection is a
physically or virtually isolated network connection solely between
AD-1 and AD-2. The other case is that of a broadcast peering
<strike><font color='red'>point</font></strike>
<strong><font color='green'>point,</font></strong> which is a common option in public Internet Exchange Points
<strike><font color='red'>(IXP).</font></strike>
<strong><font color='green'>(IXPs).</font></strong> See Section <strike><font color='red'>4.2.2</font></strike> <strong><font color='green'>4.2.4</font></strong> for more <strike><font color='red'>details about that option.</font></strike> <strong><font color='green'>details.</font></strong>
o <strike><font color='red'>Administrative Domain 1 (AD-1)</font></strike> <strong><font color='green'>AD-1</font></strong> is enabled with native multicast. A peering point exists
between AD-1 and AD-2.
o It is understood that several protocols are available for this
<strike><font color='red'>purpose</font></strike>
<strong><font color='green'>purpose,</font></strong> including <strike><font color='red'>PIM-SM</font></strike> <strong><font color='green'>Protocol-Independent Multicast - Sparse Mode
(PIM-SM)</font></strong> and <strike><font color='red'>Protocol Independent</font></strike> <strong><font color='green'>Protocol-Independent</font></strong> Multicast -
<strike><font color='red'>Source Specific</font></strike> <strong><font color='green'>Source-Specific</font></strong>
Multicast (PIM-SSM) [RFC7761], <strong><font color='green'>the</font></strong> Internet Group Management
Protocol (IGMP) [RFC3376], and Multicast Listener Discovery (MLD)
[RFC3810].
o As described in Section 2, the source IP address of the <strong><font color='green'>(so-called
"(S,G)")</font></strong> multicast stream in the originating AD (AD-1) is known.
Under this condition, <strong><font color='green'>using</font></strong> PIM-SSM <strike><font color='red'>use</font></strike> is <strike><font color='red'>beneficial</font></strike> <strong><font color='green'>beneficial,</font></strong> as it allows
the receiver's upstream router to <strike><font color='red'>directly</font></strike> send a <strike><font color='red'>JOIN</font></strike> <strong><font color='green'>join</font></strong> message <strong><font color='green'>directly</font></strong> to
the source without the need <strike><font color='red'>of invoking</font></strike> <strong><font color='green'>to invoke</font></strong> an intermediate Rendezvous
Point (RP). <strike><font color='red'>Use</font></strike> <strong><font color='green'>The use</font></strong> of SSM also presents an improved threat
mitigation profile against attack, as described in [RFC4609].
Hence, in the case of inter-domain peering, it is recommended <strike><font color='red'>to use</font></strike> <strong><font color='green'>that</font></strong>
only SSM
<strike><font color='red'>protocols;</font></strike> <strong><font color='green'>protocols be used;</font></strong> the setup of <strike><font color='red'>inter- domain</font></strike> <strong><font color='green'>inter-domain</font></strong> peering for
ASM (Any-Source Multicast) is <strike><font color='red'>not in</font></strike> <strong><font color='green'>out of</font></strong> scope for this document.
o The rest of <strike><font color='red'>the</font></strike> <strong><font color='green'>this</font></strong> document assumes that PIM-SSM and BGP are used
across the peering <strike><font color='red'>point</font></strike> <strong><font color='green'>point,</font></strong> plus <strike><font color='red'>AMT</font></strike> <strong><font color='green'>Automatic Multicast Tunneling (AMT)
[RFC7450]</font></strong> and/or <strike><font color='red'>GRE</font></strike> <strong><font color='green'>Generic Routing Encapsulation (GRE),</font></strong> according to
<strike><font color='red'>scenario.</font></strike>
<strong><font color='green'>the scenario in question.</font></strong> The use of other protocols is beyond
the scope of this document.
o <strike><font color='red'>An Automatic Multicast Tunnel (AMT) [RFC7450]</font></strike> <strong><font color='green'>AMT</font></strong> is <strike><font color='red'>setup</font></strike> <strong><font color='green'>set up</font></strong> at the peering point if either the peering point or
AD-2 is not multicast enabled. It is assumed that an AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong>
will be available to a client for multicast delivery. The
selection of an optimal AMT relay by a client is out of scope for
this document. Note that <strong><font color='green'>using</font></strong> AMT <strike><font color='red'>use</font></strike> is necessary only when native
multicast is unavailable in the peering point (Use Case 3.3) or in
the downstream administrative domain (Use Cases <strike><font color='red'>3.4,</font></strike> <strong><font color='green'>3.4</font></strong> and 3.5).
o <strike><font color='red'>The</font></strike> <strong><font color='green'>It is assumed that the</font></strong> collection of billing data is <strike><font color='red'>assumed to be</font></strike> done at the
application level and is not considered to be a networking issue.
The settlements process for <strike><font color='red'>end user</font></strike> <strong><font color='green'>EU</font></strong> billing and/or inter-provider
billing is out of scope for this document.
o Inter-domain network connectivity troubleshooting is only
considered within the context of a cooperative process between the
two domains.
This document also attempts to identify ways by which the peering
process can be improved. Development of new methods for improvement
is beyond the scope of this document.
2. Overview of Inter-domain Multicast Application Transport
A multicast-based application delivery scenario is as follows:
o Two independent administrative domains are interconnected via a
peering point.
o The peering point is either multicast enabled (end-to-end native
multicast across the two domains) or <strike><font color='red'>it is</font></strike> connected by one of two
possible tunnel types:
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> A <strike><font color='red'>Generic Routing Encapsulation (GRE) Tunnel</font></strike> <strong><font color='green'>GRE tunnel</font></strong> [RFC2784] allowing multicast tunneling across the
peering point, or
<strike><font color='red'>o An Automatic Multicast Tunnel (AMT)</font></strike>
<strong><font color='green'>* AMT</font></strong> [RFC7450].
o A service provider controls one or more application sources in
AD-1 <strike><font color='red'>which</font></strike> <strong><font color='green'>that</font></strong> will send multicast IP packets via one or more (S,G)s
(multicast traffic <strike><font color='red'>flows,</font></strike> <strong><font color='green'>flows;</font></strong> see Section 4.2.1 if you are unfamiliar
with IP multicast). It is assumed that the service being provided
is suitable for delivery via multicast <strike><font color='red'>(e.g.</font></strike> <strong><font color='green'>(e.g.,</font></strong> live video streaming
of popular events, software downloads to many <strike><font color='red'>devices, etc.),</font></strike> <strong><font color='green'>devices)</font></strong> and that
the packet streams will <strong><font color='green'>be</font></strong> carried by a suitable multicast
transport protocol.
o An <strike><font color='red'>End User (EU)</font></strike> <strong><font color='green'>EU</font></strong> controls a device connected to AD-2, which runs an
application client compatible with the service provider's
application source.
o The application client joins appropriate (S,G)s in order to
receive the data necessary to provide the service to the EU. The
mechanisms by which the application client learns the appropriate
(S,G)s are an implementation detail of the <strike><font color='red'>application,</font></strike> <strong><font color='green'>application</font></strong> and are out
of scope for this document.
The assumption here is that AD-1 has ultimate responsibility for
delivering the <strike><font color='red'>multicast based</font></strike> <strong><font color='green'>multicast-based</font></strong> service on behalf of the content
source(s). All relevant interactions between the two domains
described in this document are based on this assumption.
Note that <strike><font color='red'>domain 2</font></strike> <strong><font color='green'>AD-2</font></strong> may be an independent network domain <strike><font color='red'>(e.g.:</font></strike> <strong><font color='green'>(e.g., a</font></strong> Tier 1
network operator domain). Alternately, <strike><font color='red'>domain 2</font></strike> <strong><font color='green'>AD-2</font></strong> could also be an
<strike><font color='red'>Enterprise</font></strike>
<strong><font color='green'>enterprise</font></strong> network domain operated by a single customer of AD-1. The
peering point architecture and requirements may have some unique
aspects associated with <strike><font color='red'>the Enterprise case.</font></strike> <strong><font color='green'>enterprise networks; see Section 3.</font></strong>
The <strike><font color='red'>Use Cases</font></strike> <strong><font color='green'>use cases</font></strong> describing various architectural configurations for <strike><font color='red'>the</font></strike>
multicast <strike><font color='red'>distribution</font></strike> <strong><font color='green'>distribution,</font></strong> along with associated <strike><font color='red'>requirements is</font></strike> <strong><font color='green'>requirements, are</font></strong>
described in <strike><font color='red'>section</font></strike> <strong><font color='green'>Section</font></strong> 3. <strike><font color='red'>Unique aspects related to the Enterprise
network possibility will be described in this section.</font></strike> Section 4 contains a comprehensive list of
pertinent information that needs to be exchanged between the two
domains in order to support functions to enable <strike><font color='red'>the</font></strike> application
transport.
<strike><font color='red'>Note</font></strike>
<strong><font color='green'>3. Inter-domain Peering Point Requirements for Multicast
The transport of applications using multicast requires</font></strong> that <strike><font color='red'>domain 2 may be an independent network domain (e.g., Tier 1
network operator domain). Alternately, domain 2 could also</font></strike> <strong><font color='green'>the
inter-domain peering point</font></strong> be <strike><font color='red'>an
Enterprise network domain operated by</font></strike> <strong><font color='green'>enabled to support such</font></strong> a <strike><font color='red'>single customer.
The Use Cases describing various architectural configurations</font></strike> <strong><font color='green'>process.
This section presents five use cases</font></strong> for <strike><font color='red'>the</font></strike> <strong><font color='green'>consideration.
3.1. Native Multicast
This use case involves end-to-end native</font></strong> multicast <strike><font color='red'>distribution along with associated requirements is
described in Section 3. The peering point architecture and
requirements may have some unique aspects associated with the
Enterprise case. These unique aspects will also be described in
Section 3. Section 4 contains a comprehensive list of pertinent
information that needs to be exchanged between the two domains in
order to support functions to enable the application transport.
3. Inter-domain Peering Point Requirements for Multicast
The transport of applications using multicast requires that the
inter-domain peering point is enabled to support such a process.
There are five Use Cases for consideration in this document.
3.1. Native Multicast
This Use Case involves end-to-end Native Multicast between the two
administrative domains and the</font></strike> <strong><font color='green'>between the two
administrative domains, and the</font></strong> peering point is also native
multicast
<strike><font color='red'>enabled - see</font></strike> <strong><font color='green'>enabled. See</font></strong> Figure 1.
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | AS |------>| BR |-|---------|->| BR |-------------|-->| EU |
| | | +------+ | I1 | +------+ |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AD = Administrative Domain <strike><font color='red'>(Independent Autonomous System)</font></strike> <strong><font color='green'>(independent autonomous system)</font></strong>
AS = <strike><font color='red'>Application</font></strike> <strong><font color='green'>multicast</font></strong> (e.g., <strike><font color='red'>Content) Multicast</font></strike> <strong><font color='green'>content) Application</font></strong> Source
BR = Border Router
I1 = AD-1 and AD-2 <strike><font color='red'>Multicast Interconnection</font></strike> <strong><font color='green'>multicast interconnection</font></strong> (e.g., <strike><font color='red'>MBGP)</font></strike> <strong><font color='green'>MP-BGP)</font></strong>
I2 = AD-2 and EU <strike><font color='red'>Multicast Connection</font></strike> <strong><font color='green'>multicast connection</font></strong>
Figure 1: Content Distribution via <strike><font color='red'>End to End</font></strike> <strong><font color='green'>End-to-End</font></strong> Native Multicast
Advantages of this <strike><font color='red'>configuration are:</font></strike> <strong><font color='green'>configuration:</font></strong>
o Most efficient use of bandwidth in both domains.
o Fewer devices in the path traversed by the multicast stream when
compared to an <strike><font color='red'>AMT enabled</font></strike> <strong><font color='green'>AMT-enabled</font></strong> peering point.
From the perspective of AD-1, the one disadvantage associated with
native multicast <strike><font color='red'>into</font></strike> <strong><font color='green'>to</font></strong> AD-2 instead of individual unicast to every EU in
AD-2 is that it does not have the ability to count the number of
<strike><font color='red'>End Users</font></strike> <strong><font color='green'>EUs</font></strong>
as well as the transmitted bytes delivered to them. This information
is relevant from the perspective of customer billing and operational
logs. It is assumed that such data will be collected by the
application layer. The <strike><font color='red'>application layer</font></strike> <strong><font color='green'>application-layer</font></strong> mechanisms for generating
this information need to be robust enough <strike><font color='red'>such</font></strike> <strong><font color='green'>so</font></strong> that all pertinent
requirements for the source provider and the AD operator are
satisfactorily met. The specifics of these methods are beyond the
scope of this document.
Architectural guidelines for this configuration are as follows:
a. Dual homing for peering points between domains is recommended as
a way to ensure reliability with full BGP table visibility.
b. If the peering point between AD-1 and AD-2 is a controlled
network environment, then bandwidth can be allocated accordingly
by the two domains to permit the transit of <strike><font color='red'>non- rate adaptive</font></strike> <strong><font color='green'>non-rate-adaptive</font></strong>
multicast traffic. If this is not the case, then the multicast
traffic must support <strike><font color='red'>rate-adaption (see [BCP145]).</font></strike> <strong><font color='green'>congestion control via any of the mechanisms
described in Section 4.1 of [BCP145].</font></strong>
c. The sending and receiving of multicast traffic between two
domains is typically determined by local policies associated with
each domain. For example, if AD-1 is a service provider and AD-2
is an enterprise, then AD-1 may support local policies for
traffic delivery to, but not traffic reception from, AD-2.
Another example is the use of a policy by which AD-1 delivers
specified content to AD-2 only if such delivery has been accepted
by contract.
d. <strike><font color='red'>Relevant</font></strike> <strong><font color='green'>It is assumed that relevant</font></strong> information on multicast streams
delivered to <strike><font color='red'>End Users</font></strike> <strong><font color='green'>EUs</font></strong> in AD-2 is <strike><font color='red'>assumed to be</font></strike> collected by available capabilities
in the application layer. The precise nature and formats of the
collected information will be determined by directives from the
source owner and the domain operators.
3.2. Peering Point Enabled with GRE Tunnel
The peering point is not native multicast enabled in this <strike><font color='red'>Use Case.</font></strike> <strong><font color='green'>use case.</font></strong>
There is a <strike><font color='red'>Generic Routing Encapsulation Tunnel</font></strike> <strong><font color='green'>GRE tunnel</font></strong> provisioned over the peering point. See
Figure 2.
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ +---+ | (I1) | +---+ |
| | | +--+ |uBR|-|--------|-|uBR| +--+ | +----+
| | AS |-->|BR| +---+-| | +---+ |BR| -------->|-->| EU |
| | | <strike><font color='red'>+--+ <.......|........|........>+--+</font></strike> <strong><font color='green'>+--+<........|........|........>+--+</font></strong> |I2 +----+
\ +----+ / I1 \ /
\ / GRE \ /
\ / Tunnel \ /
------------------- -------------------
AD = Administrative Domain <strike><font color='red'>(Independent Autonomous System)</font></strike> <strong><font color='green'>(independent autonomous system)</font></strong>
AS = <strike><font color='red'>Application</font></strike> <strong><font color='green'>multicast</font></strong> (e.g., <strike><font color='red'>Content) Multicast</font></strike> <strong><font color='green'>content) Application</font></strong> Source
uBR = unicast Border Router - not necessarily multicast <strike><font color='red'>enabled</font></strike> <strong><font color='green'>enabled;</font></strong>
may be the same router as BR
BR = Border Router - for multicast
I1 = AD-1 and AD-2 <strike><font color='red'>Multicast Interconnection</font></strike> <strong><font color='green'>multicast interconnection</font></strong> (e.g., <strike><font color='red'>MBGP)</font></strike> <strong><font color='green'>MP-BGP)</font></strong>
I2 = AD-2 and EU <strike><font color='red'>Multicast Connection</font></strike> <strong><font color='green'>multicast connection</font></strong>
Figure 2: Content Distribution via GRE Tunnel
In this case, <strike><font color='red'>the</font></strike> interconnection I1 between AD-1 and AD-2 in Figure 2 is
multicast enabled via a <strike><font color='red'>Generic Routing Encapsulation
Tunnel (GRE)</font></strike> <strong><font color='green'>GRE tunnel</font></strong> [RFC2784] between the two <strike><font color='red'>BR</font></strike> <strong><font color='green'>BRs</font></strong> and
encapsulating the multicast protocols across it.
Normally, this approach is <strike><font color='red'>choosen</font></strike> <strong><font color='green'>chosen</font></strong> if the uBR <strike><font color='red'>physcially</font></strike> <strong><font color='green'>physically</font></strong> connected to
the peering link <strike><font color='red'>can</font></strike> <strong><font color='green'>cannot</font></strong> or should not be enabled for IP multicast.
This approach may also be beneficial if <strong><font color='green'>the</font></strong> BR and uBR are the same <strike><font color='red'>device,</font></strike>
<strong><font color='green'>device</font></strong> but the peering link is a broadcast domain <strike><font color='red'>(IXP),</font></strike> <strong><font color='green'>(IXP);</font></strong> see <strike><font color='red'>Figure 6.</font></strike>
<strong><font color='green'>Section 4.2.4.</font></strong>
The routing configuration is basically unchanged: <strike><font color='red'>Instead</font></strike> <strong><font color='green'>instead</font></strong> of <strong><font color='green'>running</font></strong>
BGP
<strike><font color='red'>(SAFI2)</font></strike> <strong><font color='green'>(SAFI-2) ("SAFI" stands for "Subsequent Address Family
Identifier")</font></strong> across the native IP multicast link between AD-1 and
AD-2, BGP <strike><font color='red'>(SAFI2)</font></strike> <strong><font color='green'>(SAFI-2)</font></strong> is now run across the GRE tunnel.
Advantages of this configuration:
o Highly efficient use of bandwidth in both domains, although not as
efficient as the fully native multicast <strike><font color='red'>Use Case.</font></strike> <strong><font color='green'>use case (Section 3.1).</font></strong>
o Fewer devices in the path traversed by the multicast stream when
compared to an <strike><font color='red'>AMT enabled</font></strike> <strong><font color='green'>AMT-enabled</font></strong> peering point.
o Ability to support partial and/or incremental IP multicast
deployments in <strike><font color='red'>AD- 1</font></strike> <strong><font color='green'>AD-1</font></strong> and/or AD-2: <strike><font color='red'>Only</font></strike> <strong><font color='green'>only</font></strong> the <strike><font color='red'>path(s)</font></strike> <strong><font color='green'>path or paths</font></strong> between
<strong><font color='green'>the</font></strong> AS/BR (AD-1) and <strong><font color='green'>the</font></strong> BR/EU (AD-2) need to be multicast
enabled. The uBRs may not support IP multicast or enabling it
could be seen as operationally risky on that important edge <strike><font color='red'>node</font></strike> <strong><font color='green'>node,</font></strong>
whereas dedicated BR nodes for IP multicast may <strong><font color='green'>(at least
initially)</font></strong> be more <strike><font color='red'>acceptable at least
initially.</font></strike> <strong><font color='green'>acceptable. The</font></strong> BR can also be located such
that only parts of the domain may need to support native IP
multicast <strike><font color='red'>(e.g.:</font></strike> <strong><font color='green'>(e.g.,</font></strong> only the core in AD-1 but not edge networks
towards <strong><font color='green'>the</font></strong> uBR).
o GRE is an existing technology and is relatively simple to
implement.
Disadvantages of this configuration:
o Per Use Case 3.1, current router technology cannot count the
number of <strike><font color='red'>end users</font></strike> <strong><font color='green'>EUs</font></strong> or the number <strong><font color='green'>of</font></strong> bytes transmitted.
o <strong><font color='green'>The</font></strong> GRE tunnel requires manual configuration.
o The GRE <strong><font color='green'>tunnel</font></strong> must be established prior to <strike><font color='red'>stream starting.</font></strike> <strong><font color='green'>starting the stream.</font></strong>
o The GRE tunnel is often left pinned up.
Architectural guidelines for this configuration include the
following:
Guidelines (a) through (d) are the same as those described in
Use Case 3.1. Two additional guidelines are as follows:
e. GRE tunnels are typically configured manually between peering
points to support multicast delivery between domains.
f. It is recommended that the GRE tunnel (tunnel server)
configuration in the source network <strike><font color='red'>is</font></strike> <strong><font color='green'>be</font></strong> such that it only
advertises the routes to the application sources and not to the
entire network. This practice will prevent unauthorized delivery
of applications through the tunnel <strike><font color='red'>(e.g.,</font></strike> <strong><font color='green'>(for example,</font></strong> if <strong><font color='green'>the</font></strong>
application <strike><font color='red'>- e.g.,
content -</font></strike> <strong><font color='green'>(e.g., content)</font></strong> is not part of an <strike><font color='red'>agreed</font></strike> <strong><font color='green'>agreed-upon</font></strong>
inter-domain partnership).
3.3. Peering Point Enabled with <strike><font color='red'>an</font></strike> AMT - Both Domains Multicast Enabled
<strike><font color='red'>Both</font></strike>
<strong><font color='green'>It is assumed that both</font></strong> administrative domains in this <strike><font color='red'>Use Case</font></strike> <strong><font color='green'>use case</font></strong> are <strike><font color='red'>assumed to be</font></strike>
native multicast enabled here; however, the peering point is not.
The peering point is enabled with <strike><font color='red'>an Automatic Multicast Tunnel.</font></strike> <strong><font color='green'>AMT.</font></strong> The basic configuration is
depicted in Figure <strike><font color='red'>2.</font></strike> <strong><font color='green'>3.</font></strong>
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ +---+ | I1 | +---+ |
| | | +--+ |uBR|-|--------|-|uBR| +--+ | +----+
| | AS |-->|AR| +---+-| | +---+ |AG| -------->|-->| EU |
| | | <strike><font color='red'>+--+ <.......|........|........>+--+</font></strike> <strong><font color='green'>+--+<........|........|........>+--+</font></strong> |I2 +----+
\ +----+ / AMT \ /
\ / Tunnel \ /
\ / \ /
------------------- -------------------
AD = Administrative Domain <strike><font color='red'>(Independent Autonomous System)</font></strike> <strong><font color='green'>(independent autonomous system)</font></strong>
AS = <strike><font color='red'>Application</font></strike> <strong><font color='green'>multicast</font></strong> (e.g., <strike><font color='red'>Content) Multicast</font></strike> <strong><font color='green'>content) Application</font></strong> Source
AR = AMT Relay
AG = AMT Gateway
uBR = unicast Border Router - not multicast <strike><font color='red'>enabled
otherwise AR=uBR (AD-1), uBR=AG</font></strike> <strong><font color='green'>enabled;
otherwise, AR = uBR (AD-1) and uBR = AG</font></strong> (AD-2)
I1 = AMT <strike><font color='red'>Interconnection</font></strike> <strong><font color='green'>interconnection</font></strong> between AD-1 and AD-2
I2 = AD-2 and EU <strike><font color='red'>Multicast Connection</font></strike> <strong><font color='green'>multicast connection</font></strong>
Figure 3: <strike><font color='red'>-</font></strike> AMT Interconnection between AD-1 and AD-2
Advantages of this configuration:
o Highly efficient use of bandwidth in AD-1.
o AMT is an existing technology and is relatively simple to
implement. Attractive properties of AMT include the following:
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> Dynamic interconnection between <strike><font color='red'>Gateway-Relay</font></strike> <strong><font color='green'>the gateway-relay</font></strong> pair across
the peering point.
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> Ability to serve clients and servers with differing policies.
Disadvantages of this configuration:
o Per Use Case 3.1 (AD-2 is native multicast), current router
technology cannot count the number of <strike><font color='red'>end users</font></strike> <strong><font color='green'>EUs</font></strong> or the number of bytes
transmitted to all <strike><font color='red'>end users.</font></strike> <strong><font color='green'>EUs.</font></strong>
o Additional devices (AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> and <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> pairs) may be introduced
into the path if these services are not incorporated <strike><font color='red'>in</font></strike> <strong><font color='green'>into</font></strong> the
existing routing nodes.
o Currently undefined mechanisms for the AG to automatically select
the optimal AR.
Architectural guidelines for this configuration are as follows:
Guidelines (a) through (d) are the same as those described in
Use Case 3.1. In addition,
e. It is recommended that AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> and <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> pairs be configured
at the peering points to support multicast delivery between
domains. AMT tunnels will then configure dynamically across the
peering points once the <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> in AD-2 receives the <strike><font color='red'>(S, G)</font></strike> <strong><font color='green'>(S,G)</font></strong>
information from the EU.
3.4. Peering Point Enabled with <strike><font color='red'>an</font></strike> AMT - AD-2 Not Multicast Enabled
In this AMT <strike><font color='red'>Use Case, the second administrative domain</font></strike> <strong><font color='green'>use case,</font></strong> AD-2 is not multicast enabled. Hence, the
interconnection between AD-2 and the
<strike><font color='red'>End User</font></strike> <strong><font color='green'>EU</font></strong> is also not multicast
enabled. This <strike><font color='red'>Use Case</font></strike> <strong><font color='green'>use case</font></strong> is depicted in Figure <strike><font color='red'>3.</font></strike> <strong><font color='green'>4.</font></strong>
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / <strike><font color='red'>(Non</font></strike> <strong><font color='green'>(Not</font></strong> Multicast \
/ \ / Enabled) \ N(large)
| +----+ +---+ | | +---+ | <strike><font color='red'>#EU</font></strike> <strong><font color='green'># EUs</font></strong>
| | | +--+ |uBR|-|--------|-|uBR| | +----+
| | AS |-->|AR| +---+-| | +---+ ................>|EU/G|
| | | <strike><font color='red'>+--+ <.......|........|...........</font></strike> <strong><font color='green'>+--+<........|........|...........</font></strong> |I2 +----+
\ +----+ / N x AMT\ /
\ / Tunnel \ /
\ / \ /
------------------- -------------------
AS = <strong><font color='green'>multicast (e.g., content)</font></strong> Application <strike><font color='red'>Multicast</font></strike> Source
uBR = unicast Border Router - not multicast <strike><font color='red'>enabled,
otherwise</font></strike> <strong><font color='green'>enabled;
otherwise,</font></strong> AR = uBR (in <strike><font color='red'>AD-1).</font></strike> <strong><font color='green'>AD-1)</font></strong>
AR = AMT Relay
EU/G = Gateway client embedded in EU device
I2 = AMT <strike><font color='red'>Tunnel Connecting</font></strike> <strong><font color='green'>tunnel connecting</font></strong> EU/G to AR in AD-1 through <strike><font color='red'>Non-Multicast
Enabled AD-2.</font></strike>
<strong><font color='green'>non-multicast-enabled AD-2</font></strong>
Figure 4: AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway
This <strike><font color='red'>Use Case</font></strike> <strong><font color='green'>use case</font></strong> is equivalent to having unicast distribution of the
application through AD-2. The total number of AMT tunnels would be
equal to the total number of <strike><font color='red'>End Users</font></strike> <strong><font color='green'>EUs</font></strong> requesting the application. The
peering point thus needs to accommodate the total number of AMT
tunnels between the two domains. Each AMT tunnel can provide the
data usage associated with each <strike><font color='red'>End User.</font></strike> <strong><font color='green'>EU.</font></strong>
Advantages of this configuration:
o Efficient use of bandwidth in AD-1 <strike><font color='red'>(The</font></strike> <strong><font color='green'>(the</font></strong> closer <strong><font color='green'>the</font></strong> AR is to <strong><font color='green'>the</font></strong>
uBR, the more efficient).
o Ability <strike><font color='red'>for</font></strike> <strong><font color='green'>of</font></strong> AD-1 to introduce <strike><font color='red'>IP multicast based</font></strike> content delivery <strong><font color='green'>based on IP
multicast,</font></strong> without any support by network devices in AD-2: <strike><font color='red'>Only</font></strike> <strong><font color='green'>only
the</font></strong> application side in the EU device needs to perform AMT gateway
library functionality to receive traffic from <strong><font color='green'>the</font></strong> AMT relay.
o Allows <strike><font color='red'>for</font></strike> AD-2 to "upgrade" to Use Case 3.5 (see <strike><font color='red'>below)</font></strike> <strong><font color='green'>Section 3.5)</font></strong> at a
later <strike><font color='red'>time</font></strike> <strong><font color='green'>time,</font></strong> without any change in AD-1 at that time.
o AMT is an existing technology and is relatively simple to
implement. Attractive properties of AMT include the following:
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> Dynamic interconnection between <strike><font color='red'>Gateway-Relay</font></strike> <strong><font color='green'>the AMT gateway-relay</font></strong> pair
across the peering point.
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> Ability to serve clients and servers with differing policies.
o Each AMT tunnel serves as a count for each <strike><font color='red'>End User</font></strike> <strong><font color='green'>EU</font></strong> and is also able to
track data usage (bytes) delivered to the EU.
Disadvantages of this configuration:
o Additional devices (AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> and <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> pairs) are introduced
into the transport path.
o Assuming multiple peering points between the domains, the EU
<strike><font color='red'>Gateway</font></strike>
<strong><font color='green'>gateway</font></strong> needs to be able to find the "correct" AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in AD-1.
Architectural guidelines for this configuration are as follows:
Guidelines (a) through (c) are the same as those described in
Use Case 3.1. <strong><font color='green'>In addition,</font></strong>
d. It is necessary that proper procedures <strike><font color='red'>are</font></strike> <strong><font color='green'>be</font></strong> implemented such that
the AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> at the <strike><font color='red'>End User</font></strike> <strong><font color='green'>EU</font></strong> device is able to find the correct AMT <strike><font color='red'>Relay</font></strike>
<strong><font color='green'>relay</font></strong> for each (S,G) content stream. Standard mechanisms for
that selection are still subject to ongoing work. This includes
<strong><font color='green'>the</font></strong> use of anycast gateway addresses, anycast DNS names, <strong><font color='green'>or</font></strong>
explicit configuration that <strike><font color='red'>is mapping</font></strike> <strong><font color='green'>maps</font></strong> (S,G) to a relay <strike><font color='red'>address</font></strike> <strong><font color='green'>address;</font></strong> or
letting the application in the EU/G provide the relay address to
the embedded AMT gateway function.
e. The AMT <strike><font color='red'>tunnel</font></strike> <strong><font color='green'>tunnel's</font></strong> capabilities are expected to be sufficient for
the purpose of collecting relevant information on the multicast
streams delivered to <strike><font color='red'>End Users</font></strike> <strong><font color='green'>EUs</font></strong> in AD-2.
3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels <strike><font color='red'>Through</font></strike> <strong><font color='green'>through</font></strong> AD-2
<strike><font color='red'>This is</font></strike>
<strong><font color='green'>Figure 5 illustrates</font></strong> a variation of Use Case <strike><font color='red'>3.4 as follows:</font></strike> <strong><font color='green'>3.4:</font></strong>
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / <strike><font color='red'>(Non</font></strike> <strong><font color='green'>(Not</font></strong> Multicast \
/ +---+ \ (I1) / +---+ Enabled) \
| +----+ |uBR|-|--------|-|uBR| |
| | | +--+ +---+ | | +---+ +---+ | +----+
| | AS |-->|AR|<........|.... | +---+ |AG/|....>|EU/G|
| | | +--+ | ......|.|AG/|..........>|AR2| |I3 +----+
\ +----+ / I1 \ |AR1| I2 +---+ /
\ / <strike><font color='red'>single</font></strike> <strong><font color='green'>Single</font></strong> \+---+ /
\ / AMT Tunnel \ /
------------------- -------------------
uBR = unicast Border Router - not multicast <strike><font color='red'>enabled
otherwise AR=uBR</font></strike> <strong><font color='green'>enabled;
otherwise, AR = uBR</font></strong> (AD-1) or <strike><font color='red'>ubr=AGAR1</font></strike> <strong><font color='green'>uBR = AGAR1</font></strong> (AD-2)
AS = <strong><font color='green'>multicast (e.g., content)</font></strong> Application Source
AR = AMT Relay in AD-1
AGAR1 = AMT Gateway/Relay node in AD-2 across <strike><font color='red'>Peering Point</font></strike> <strong><font color='green'>peering point</font></strong>
I1 = AMT <strike><font color='red'>Tunnel Connecting</font></strike> <strong><font color='green'>tunnel connecting</font></strong> AR in AD-1 to <strike><font color='red'>GW</font></strike> <strong><font color='green'>gateway</font></strong> in AGAR1 in AD-2
AGAR2 = AMT Gateway/Relay node at AD-2 <strike><font color='red'>Network Edge</font></strike> <strong><font color='green'>network edge</font></strong>
I2 = AMT <strike><font color='red'>Tunnel Connecting Relay</font></strike> <strong><font color='green'>tunnel connecting relay</font></strong> in AGAR1 to <strike><font color='red'>GW</font></strike> <strong><font color='green'>gateway</font></strong> in AGAR2
EU/G = Gateway client embedded in EU device
I3 = AMT <strike><font color='red'>Tunnel Connecting</font></strike> <strong><font color='green'>tunnel connecting</font></strong> EU/G to AR in AGAR2
Figure 5: AMT Tunnel Connecting AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>Gateways</font></strong> and Relays
Use Case 3.4 results in several long AMT tunnels crossing the entire
network of AD-2 linking the EU device and the AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in AD-1
through the peering point. Depending on the number of <strike><font color='red'>End Users,</font></strike> <strong><font color='green'>EUs,</font></strong> there is
a likelihood of an unacceptably high amount of traffic due to the
large number of AMT tunnels <strike><font color='red'>-</font></strike> <strong><font color='green'>--</font></strong> and unicast streams <strike><font color='red'>-</font></strike> <strong><font color='green'>--</font></strong> through the
peering point. This situation can be alleviated as follows:
o Provisioning of strategically located AMT nodes in <strike><font color='red'>AD-2</font></strike> AD-2. An
AMT node comprises co-location of an AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> and an AMT <strike><font color='red'>Relay.</font></strike> <strong><font color='green'>relay.</font></strong>
No change is required by <strike><font color='red'>AD-1</font></strike> <strong><font color='green'>AD-1, as</font></strong> compared to <strong><font color='green'>Use Case</font></strong> 3.4. This
can be done whenever AD-2 <strike><font color='red'>seems</font></strike> <strong><font color='green'>sees</font></strong> fit <strike><font color='red'>(too</font></strike> <strong><font color='green'>(e.g., too</font></strong> much traffic across
<strong><font color='green'>the</font></strong> peering <strike><font color='red'>point.</font></strike> <strong><font color='green'>point).</font></strong>
o One such node is <strike><font color='red'>at</font></strike> <strong><font color='green'>on</font></strong> the AD-2 side of the peering point <strike><font color='red'>(node</font></strike> <strong><font color='green'>(AMT node</font></strong>
AGAR1 in <strike><font color='red'>above Figure).</font></strike> <strong><font color='green'>Figure 5).</font></strong>
o <strike><font color='red'>Single</font></strike> <strong><font color='green'>A single</font></strong> AMT tunnel established across <strong><font color='green'>the</font></strong> peering point linking
<strong><font color='green'>the</font></strong> AMT
<strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in AD-1 to the AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> in <strike><font color='red'>the</font></strike> AMT node AGAR1
in AD-2.
o AMT tunnels linking AMT node AGAR1 at <strong><font color='green'>the</font></strong> peering point in AD-2 to
other AMT nodes located at the edges of AD-2: e.g., AMT tunnel I2
linking <strong><font color='green'>the</font></strong> AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in AGAR1 to <strong><font color='green'>the</font></strong> AMT <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> in AMT
node AGAR2 <strike><font color='red'>in
Figure 4.</font></strike> <strong><font color='green'>(Figure 5).</font></strong>
o AMT tunnels linking <strong><font color='green'>an</font></strong> EU device (via <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>a gateway</font></strong> client embedded in
<strong><font color='green'>the</font></strong> device) and <strong><font color='green'>an</font></strong> AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in <strong><font color='green'>an</font></strong> appropriate AMT node at <strong><font color='green'>the</font></strong>
edge of AD-2: e.g., I3 linking <strong><font color='green'>the</font></strong> EU <strike><font color='red'>Gateway</font></strike> <strong><font color='green'>gateway</font></strong> in <strong><font color='green'>the</font></strong> device to <strong><font color='green'>the</font></strong>
AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in AMT node AGAR2.
o In the <strike><font color='red'>most simple</font></strike> <strong><font color='green'>simplest</font></strong> option (not shown), AD-2 only deploys a single
AGAR1 <strong><font color='green'>node</font></strong> and lets <strong><font color='green'>the</font></strong> EU/G build AMT tunnels directly to it.
This setup already solves the problem of replicated traffic across
the peering point. As soon as there is <strong><font color='green'>a</font></strong> need to support more AMT
tunnels to <strong><font color='green'>the</font></strong> EU/G, then additional AGAR2 nodes can be deployed
by AD-2.
The advantage <strike><font color='red'>for</font></strike> <strong><font color='green'>of</font></strong> such a chained set of AMT tunnels is that the total
number of unicast streams across AD-2 is significantly reduced, thus
freeing up bandwidth. Additionally, there will be a single unicast
stream across the peering point instead <strike><font color='red'>of</font></strike> <strong><font color='green'>of,</font></strong> possibly, an unacceptably
large number of such streams per Use Case 3.4. However, this implies
that several AMT tunnels will need to be dynamically configured by
the various AMT <strike><font color='red'>Gateways</font></strike> <strong><font color='green'>gateways,</font></strong> based solely on the (S,G) information
received from the application client at the EU device. A suitable
mechanism for such dynamic configurations is therefore critical.
Architectural guidelines for this configuration are as follows:
Guidelines (a) through (c) are the same as those described in
Use Case 3.1. <strong><font color='green'>In addition,</font></strong>
d. It is necessary that proper procedures <strike><font color='red'>are</font></strike> <strong><font color='green'>be</font></strong> implemented such that
the various AMT <strike><font color='red'>Gateways</font></strike> <strong><font color='green'>gateways</font></strong> (at the <strike><font color='red'>End User</font></strike> <strong><font color='green'>EU</font></strong> devices and the AMT nodes in
AD-2) are able to find the correct AMT <strike><font color='red'>Relay</font></strike> <strong><font color='green'>relay</font></strong> in other AMT nodes
as appropriate. Standard mechanisms for that selection are still
subject to ongoing work. This includes <strong><font color='green'>the</font></strong> use of anycast
gateway addresses, anycast DNS names, or explicit configuration
that <strike><font color='red'>is mapping</font></strike> <strong><font color='green'>maps</font></strong> (S,G) to a relay address. On the EU/G, this mapping
information may come from the application.
e. The AMT <strike><font color='red'>tunnel</font></strike> <strong><font color='green'>tunnel's</font></strong> capabilities are expected to be sufficient for
the purpose of collecting relevant information on the multicast
streams delivered to <strike><font color='red'>End Users</font></strike> <strong><font color='green'>EUs</font></strong> in AD-2.
4. Functional Guidelines
Supporting functions and related interfaces over the peering point
that enable the multicast transport of the application are listed in
this section. Critical information parameters that need to be
exchanged in support of these functions are enumerated, along with
guidelines as appropriate. Specific interface functions for
consideration are as follows.
4.1. Network Interconnection Transport Guidelines
The term <strike><font color='red'>"Network Interconnection Transport"</font></strike> <strong><font color='green'>"network interconnection transport"</font></strong> refers to the
interconnection points between the two <strike><font color='red'>Administrative Domains.</font></strike> <strong><font color='green'>administrative domains.</font></strong> The
following is a representative set of attributes that <strike><font color='red'>will need to be
agreed to between</font></strike> the two
administrative domains <strong><font color='green'>will need to agree on</font></strong> to support multicast
delivery.
o Number of <strike><font color='red'>Peering Points.</font></strike> <strong><font color='green'>peering points.</font></strong>
o Peering <strike><font color='red'>Point Addresses</font></strike> <strong><font color='green'>point addresses</font></strong> and <strike><font color='red'>Locations.</font></strike> <strong><font color='green'>locations.</font></strong>
o Connection <strike><font color='red'>Type</font></strike> <strong><font color='green'>type</font></strong> - Dedicated for <strike><font color='red'>Multicast</font></strike> <strong><font color='green'>multicast</font></strong> delivery or shared with
other services.
o Connection <strike><font color='red'>Mode</font></strike> <strong><font color='green'>mode</font></strong> - Direct connectivity between the two <strike><font color='red'>AD's</font></strike> <strong><font color='green'>ADs</font></strong> or via
another ISP.
o Peering <strike><font color='red'>Point Protocol Support</font></strike> <strong><font color='green'>point protocol support</font></strong> - Multicast protocols that will be
used for multicast delivery will need to be supported at these
points. Examples of <strong><font color='green'>such</font></strong> protocols include <strike><font color='red'>eBGP</font></strike> <strong><font color='green'>External BGP (EBGP)</font></strong>
[RFC4760] <strike><font color='red'>and MBGP</font></strike> <strong><font color='green'>peering via MP-BGP (Multiprotocol BGP) SAFI-2</font></strong> [RFC4760].
o Bandwidth <strike><font color='red'>Allocation</font></strike> <strong><font color='green'>allocation</font></strong> - If shared with other services, then there
needs to be a determination of the share of bandwidth reserved for
multicast delivery. See <strike><font color='red'>section</font></strike> <strong><font color='green'>Section</font></strong> 4.1.1 below for more details.
o QoS <strike><font color='red'>Requirements</font></strike> <strong><font color='green'>requirements</font></strong> - Delay and/or latency specifications that need
to be specified in an SLA.
o AD <strike><font color='red'>Roles</font></strike> <strong><font color='green'>roles</font></strong> and <strike><font color='red'>Responsibilities</font></strike> <strong><font color='green'>responsibilities</font></strong> - <strike><font color='red'>the</font></strike> <strong><font color='green'>The</font></strong> role played by each AD for
provisioning and maintaining the set of peering points to support
multicast delivery.
4.1.1. Bandwidth Management
Like IP unicast traffic, IP multicast traffic carried across <strike><font color='red'>non-
controlled</font></strike>
<strong><font color='green'>non-controlled</font></strong> networks must comply <strike><font color='red'>to Congestion Control Principles</font></strike> <strong><font color='green'>with congestion control
principles</font></strong> as described in [BCP41] and <strong><font color='green'>as</font></strong> explained in detail for UDP
IP multicast in [BCP145].
Non-controlled networks (such as the Internet) are <strike><font color='red'>those</font></strike> <strong><font color='green'>networks</font></strong> where
there is no policy for managing bandwidth other than best effort with
<strong><font color='green'>a</font></strong> fair share of bandwidth under congestion. As a simplified rule of
thumb, complying <strike><font color='red'>to</font></strike> <strong><font color='green'>with</font></strong> congestion control principles means <strike><font color='red'>to reduce</font></strike> <strong><font color='green'>reducing</font></strong>
bandwidth under congestion in a way that is fair to competing <strike><font color='red'>competing</font></strike>
(typically TCP) <strike><font color='red'>flow</font></strike> <strong><font color='green'>flows</font></strong> ("rate adaptive").
In many instances, multicast content delivery evolves from <strike><font color='red'>intra-
domain</font></strike>
<strong><font color='green'>intra-domain</font></strong> deployments where it is handled as a controlled network
service and <strike><font color='red'>of</font></strike> <strong><font color='green'>does</font></strong> not <strike><font color='red'>complyng to</font></strike> <strong><font color='green'>comply with</font></strong> congestion control principles. It
was given a reserved amount of bandwidth and admitted to the network
so that congestion never occurs. <strike><font color='red'>Therefore</font></strike> <strong><font color='green'>Therefore,</font></strong> the congestion control
issue should be given specific attention when evolving to an <strike><font color='red'>interdomain</font></strike>
<strong><font color='green'>inter-domain</font></strong> peering deployment.
In the case where end-to-end IP multicast traffic passes across the
network of two ADs (and their subsidiaries/customers), both ADs must
agree on a consistent <strike><font color='red'>traffic management</font></strike> <strong><font color='green'>traffic-management</font></strong> policy. <strike><font color='red'>If</font></strike> <strong><font color='green'>If,</font></strong> for <strike><font color='red'>example</font></strike> <strong><font color='green'>example,</font></strong>
AD-1 sources <strike><font color='red'>non congestion aware</font></strike> <strong><font color='green'>non-congestion-aware</font></strong> IP multicast traffic and AD-2
carries it as <strike><font color='red'>best effort</font></strike> <strong><font color='green'>best-effort</font></strong> traffic across links shared with other
Internet traffic <strike><font color='red'>and subject</font></strike> <strong><font color='green'>(subject</font></strong> to <strike><font color='red'>congestion,</font></strike> <strong><font color='green'>congestion),</font></strong> this will not work: <strike><font color='red'>Under</font></strike> <strong><font color='green'>under</font></strong>
congestion, some amount of that traffic will be dropped, <strong><font color='green'>often</font></strong>
rendering the remaining packets <strike><font color='red'>often</font></strike> as <strike><font color='red'>undecodeable</font></strike> <strong><font color='green'>undecodable</font></strong> garbage clogging up
the network in <strike><font color='red'>AD-2 and</font></strike> <strong><font color='green'>AD-2;</font></strong> because this <strong><font color='green'>traffic</font></strong> is not congestion aware,
the loss does not reduce this rate. Competing traffic will not get
their fair share under congestion, and EUs will be <strike><font color='red'>frusted</font></strike> <strong><font color='green'>frustrated</font></strong> by <strong><font color='green'>the</font></strong>
extremely bad quality of both their IP multicast <strong><font color='green'>traffic</font></strong> and other <strike><font color='red'>(e.g.:</font></strike>
<strong><font color='green'>(e.g.,</font></strong> TCP) traffic. Note that this is not an IP multicast
technology <strike><font color='red'>issue,</font></strike> <strong><font color='green'>issue</font></strong> but <strong><font color='green'>is</font></strong> solely a
<strike><font color='red'>transport/application layer</font></strike> <strong><font color='green'>transport-layer / application-layer</font></strong>
issue: <strike><font color='red'>The</font></strike> <strong><font color='green'>the</font></strong> problem would <strike><font color='red'>equally</font></strike> <strong><font color='green'>just as likely</font></strong> happen if AD-1 <strike><font color='red'>would</font></strike> <strong><font color='green'>were to</font></strong> send <strike><font color='red'>non-rate adaptive</font></strike>
<strong><font color='green'>non-rate-adaptive</font></strong> unicast <strike><font color='red'>traffic,,</font></strike> <strong><font color='green'>traffic --</font></strong> for <strike><font color='red'>example</font></strike> <strong><font color='green'>example,</font></strong> legacy IPTV
video-on-demand <strike><font color='red'>traffic</font></strike> <strong><font color='green'>traffic,</font></strong> which <strike><font color='red'>typically</font></strike> is <strong><font color='green'>typically</font></strong> also <strike><font color='red'>non
congestion</font></strike> <strong><font color='green'>non-congestion</font></strong>
aware. <strike><font color='red'>Because</font></strike> <strong><font color='green'>Note that because</font></strong> rate adaption in IP unicast video is
commonplace today <strike><font color='red'>because</font></strike> <strong><font color='green'>due to the availability</font></strong> of ABR (Adaptive <strike><font color='red'>Bitrate Video),</font></strike> <strong><font color='green'>Bitrate)
video,</font></strong> it is very unlikely <strike><font color='red'>for</font></strike> <strong><font color='green'>that</font></strong> this <strike><font color='red'>to</font></strike> <strong><font color='green'>will</font></strong> happen <strike><font color='red'>though</font></strike> in reality with IP
unicast.
While the rules for traffic management apply whether <strike><font color='red'>or not</font></strike> IP multicast is
tunneled or not, the one feature that can make AMT tunnels more
difficult is the unpredictability of bandwidth requirements across
underlying links because of the way they can be used: <strike><font color='red'>With</font></strike> <strong><font color='green'>with</font></strong> native IP
multicast or GRE tunnels, the amount of bandwidth depends on the
amount of <strike><font color='red'>content,</font></strike> <strong><font color='green'>content --</font></strong> not the number of EUs <strike><font color='red'>-</font></strike> <strong><font color='green'>--</font></strong> and is therefore easier
to plan for. AMT tunnels terminating in <strike><font color='red'>EU/G</font></strike> <strong><font color='green'>the EU/G,</font></strong> on the other <strike><font color='red'>hand</font></strike> <strong><font color='green'>hand,</font></strong>
scale with the number of EUs. In the vicinity of the AMT <strike><font color='red'>relay</font></strike> <strong><font color='green'>relay,</font></strong> they
can introduce <strong><font color='green'>a</font></strong> very large amount of replicated
<strike><font color='red'>traffic</font></strike> <strong><font color='green'>traffic,</font></strong> and it is
not always feasible to provision enough bandwidth for all possible <strike><font color='red'>EU</font></strike>
<strong><font color='green'>EUs</font></strong> to get the highest quality for all their content during peak
utilization in such setups <strike><font color='red'>-</font></strike> <strong><font color='green'>--</font></strong> unless the AMT relays are very close to
the EU edge. <strike><font color='red'>Therefore</font></strike> <strong><font color='green'>Therefore,</font></strong> it is also recommended <strike><font color='red'>to use</font></strike> <strong><font color='green'>that</font></strong> IP multicast
rate adaptation <strong><font color='green'>be used,</font></strong> even inside controlled <strike><font color='red'>networks</font></strike> <strong><font color='green'>networks,</font></strong> when using
AMT tunnels directly to <strong><font color='green'>the</font></strong> EU/G.
Note that rate-adaptive IP multicast traffic in general does not mean
that the sender is reducing the <strike><font color='red'>bitrate,</font></strike> <strong><font color='green'>bitrate</font></strong> but rather that the EUs that
experience congestion are joining to a <strike><font color='red'>lower bitrate</font></strike> <strong><font color='green'>lower-bitrate</font></strong> (S,G) stream of
the content, similar to <strike><font color='red'>adaptive bitrate</font></strike> <strong><font color='green'>ABR</font></strong> streaming over TCP.
<strike><font color='red'>Migration</font></strike> <strong><font color='green'>Therefore, migration</font></strong>
from <strike><font color='red'>non rate-adaptive</font></strike> <strong><font color='green'>a non-rate-adaptive bitrate</font></strong> to <strike><font color='red'>rate adaptive</font></strike> <strong><font color='green'>a rate-adaptive</font></strong> bitrate in IP
multicast <strike><font color='red'>does therefore</font></strike> <strong><font color='green'>will</font></strong> also change the dynamic (S,G) join behavior in the <strike><font color='red'>network</font></strike>
<strong><font color='green'>network,</font></strong> resulting in potentially higher performance
<strike><font color='red'>requirement</font></strike> <strong><font color='green'>requirements</font></strong> for
IP multicast protocols (IGMP/PIM), especially on the last hops where
dynamic changes occur (including AMT <strike><font color='red'>gateway/relays):
In non rate-adaptive</font></strike> <strong><font color='green'>gateways/relays): in non-rate-
adaptive</font></strong> IP multicast, only "channel change" causes state change, <strong><font color='green'>but</font></strong>
in rate-adaptive <strike><font color='red'>also the</font></strike> <strong><font color='green'>multicast,</font></strong> congestion <strike><font color='red'>situation</font></strike> <strong><font color='green'>also</font></strong> causes state change.
Even though not fully specified in this document, peerings that rely
on GRE/AMT tunnels may be across one or more transit ADs instead of
an exclusive (non-shared, L1/L2) path. Unless those transit ADs are
explicitly contracted to provide other than "best effort" transit for
the tunneled traffic, the <strong><font color='green'>tunneled</font></strong> IP multicast traffic <strike><font color='red'>tunneled</font></strike> must be
rate adaptive <strong><font color='green'>in order</font></strong> to not violate <strike><font color='red'>BCP41</font></strike> <strong><font color='green'>BCP 41</font></strong> across those
transit ADs.
4.2. Routing Aspects and Related Guidelines
The main objective for multicast delivery routing is to ensure that
the <strike><font color='red'>End User</font></strike> <strong><font color='green'>EU</font></strong> receives the multicast stream from the "most optimal" source <strike><font color='red'>[INF_ATIS_10]</font></strike>
<strong><font color='green'>[INF_ATIS_10],</font></strong> which typically:
o Maximizes the multicast portion of the transport and minimizes any
unicast portion of the delivery, and
o Minimizes the overall combined <strike><font color='red'>network(s)</font></strike> route <strike><font color='red'>distance.</font></strike> <strong><font color='green'>distance of the network(s).</font></strong>
This routing objective applies to both <strike><font color='red'>Native</font></strike> <strong><font color='green'>native multicast</font></strong> and AMT; the
actual methodology of the solution will be different for each.
Regardless, the routing solution is <strike><font color='red'>expected:</font></strike> <strong><font color='green'>expected to:</font></strong>
o <strike><font color='red'>To be</font></strike> <strong><font color='green'>Be</font></strong> scalable,
o <strike><font color='red'>To avoid</font></strike> <strong><font color='green'>Avoid</font></strong> or minimize new protocol development or modifications, and
o <strike><font color='red'>To be</font></strike> <strong><font color='green'>Be</font></strong> robust enough to achieve high reliability and <strong><font color='green'>to</font></strong> automatically
adjust to changes and problems in the multicast infrastructure.
For both <strike><font color='red'>Native</font></strike> <strong><font color='green'>native</font></strong> and AMT environments, having a source as close as
possible to the EU network is most desirable; therefore, in some
cases, an AD may prefer to have multiple sources near different
peering points. However, that is entirely an implementation issue.
4.2.1. Native Multicast Routing Aspects
Native multicast simply requires that the <strike><font color='red'>Administrative Domains</font></strike> <strong><font color='green'>administrative domains</font></strong>
coordinate and advertise the correct source address(es) at their
network interconnection peering <strike><font color='red'>points(i.e., border routers).</font></strike> <strong><font color='green'>points (i.e., BRs).</font></strong> An example of
multicast delivery via a <strike><font color='red'>Native Multicast</font></strike> <strong><font color='green'>native multicast</font></strong> process across two <strike><font color='red'>Administrative Domains</font></strike>
<strong><font color='green'>administrative domains</font></strong> is as <strike><font color='red'>follows</font></strike> <strong><font color='green'>follows,</font></strong> assuming that the
interconnecting peering points are also multicast enabled:
o Appropriate information is obtained by the EU <strike><font color='red'>client</font></strike> <strong><font color='green'>client,</font></strong> who is a
subscriber to AD-2 (see Use Case 3.1). This information is in the
form of <strike><font color='red'>metadata</font></strike> <strong><font color='green'>metadata,</font></strong> and it contains instructions directing the EU
client to launch an appropriate application if necessary, as well
as additional information for the application about the source
location and the group (or stream) <strike><font color='red'>id</font></strike> <strong><font color='green'>ID</font></strong> in the form of <strike><font color='red'>the "S,G"</font></strike> <strong><font color='green'>(S,G)</font></strong> data.
The "S" portion provides the name or IP address of the source of
the multicast stream. The metadata may also contain alternate
delivery <strike><font color='red'>information</font></strike> <strong><font color='green'>information,</font></strong> such as specifying the unicast address of
the stream.
o The client uses the join message with <strike><font color='red'>S,G</font></strike> <strong><font color='green'>(S,G)</font></strong> to join the multicast
stream [RFC4604]. To facilitate this process, the two <strike><font color='red'>AD's</font></strike> <strong><font color='green'>ADs</font></strong> need to
do the following:
<strike><font color='red'>o</font></strike>
<strong><font color='green'>*</font></strong> Advertise the source <strike><font color='red'>id(s)</font></strike> <strong><font color='green'>ID(s)</font></strong> over the <strike><font color='red'>Peering Points.
o</font></strike> <strong><font color='green'>peering points.
*</font></strong> Exchange <strong><font color='green'>such</font></strong> relevant <strike><font color='red'>Peering Point</font></strike> <strong><font color='green'>peering point</font></strong> information <strike><font color='red'>such</font></strike> as <strike><font color='red'>Capacity</font></strike> <strong><font color='green'>capacity</font></strong>
and <strike><font color='red'>Utilization.
o</font></strike> <strong><font color='green'>utilization.
*</font></strong> Implement compatible multicast protocols to ensure proper
multicast delivery across the peering points.
4.2.2. GRE Tunnel over Interconnecting Peering Point
If the interconnecting peering point is not multicast enabled and
both <strike><font color='red'>AD's</font></strike> <strong><font color='green'>ADs</font></strong> are multicast enabled, then a simple solution is to
provision a GRE tunnel between the two <strike><font color='red'>AD's -</font></strike> <strong><font color='green'>ADs;</font></strong> see Use Case <strike><font color='red'>3.2.2.</font></strike> <strong><font color='green'>3.2
(Section 3.2).</font></strong> The termination points of the tunnel will usually be
a network engineering <strike><font color='red'>decision,</font></strike> <strong><font color='green'>decision</font></strong> but generally will be between the <strike><font color='red'>border
routers</font></strike> <strong><font color='green'>BRs</font></strong>
or even between the <strike><font color='red'>AD 2 border router</font></strike> <strong><font color='green'>AD-2 BR</font></strong> and the <strike><font color='red'>AD 1</font></strike> <strong><font color='green'>AD-1</font></strong> source (or source access
router). The GRE tunnel would allow end-to-end native multicast or
AMT multicast to traverse the interface. Coordination and
advertisement of the source IP <strike><font color='red'>is</font></strike> <strong><font color='green'>are</font></strong> still required.
The two <strike><font color='red'>AD's</font></strike> <strong><font color='green'>ADs</font></strong> need to follow the same process as <strong><font color='green'>the process</font></strong> described
in <strong><font color='green'>Section</font></strong> 4.2.1 to facilitate multicast delivery across the <strike><font color='red'>Peering Points.</font></strike> <strong><font color='green'>peering
points.</font></strong>
4.2.3. Routing Aspects with AMT Tunnels
Unlike <strike><font color='red'>Native Multicast</font></strike> <strong><font color='green'>native multicast</font></strong> (with or without GRE), an AMT <strike><font color='red'>Multicast</font></strike> <strong><font color='green'>multicast</font></strong>
environment is more complex. It presents a <strike><font color='red'>dual layered</font></strike> <strong><font color='green'>two-layered</font></strong> problem
<strike><font color='red'>because</font></strike>
<strong><font color='green'>in that</font></strong> there are two criteria that should be simultaneously met:
o Find the closest AMT relay to the <strike><font color='red'>end-user</font></strike> <strong><font color='green'>EU</font></strong> that also has multicast
connectivity to the content source, and
o Minimize the AMT unicast tunnel distance.
There are essentially two components <strike><font color='red'>to</font></strike> <strong><font color='green'>in</font></strong> the AMT <strike><font color='red'>specification</font></strike> <strong><font color='green'>specification:</font></strong>