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draft-ietf-mboned-interdomain-peering-bcp-12.xml
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draft-ietf-mboned-interdomain-peering-bcp-12.xml
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<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY RFC2784 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2784.xml">
<!ENTITY RFC3376 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3376.xml">
<!ENTITY RFC3810 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3810.xml">
<!ENTITY RFC4760 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4760.xml">
<!ENTITY RFC4604 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4604.xml">
<!ENTITY RFC4609 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4609.xml">
<!ENTITY RFC7450 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7450.xml">
<!ENTITY RFC7761 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7761.xml">
<!ENTITY I-D.ietf-mboned-mtrace-v2 SYSTEM "https://xml2rfc.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-mboned-mtrace-v2.xml">
]>
<rfc submissionType="IETF" docName="draft-ietf-mboned-interdomain-peering-bcp-12" category="bcp" ipr="pre5378Trust200902"><?rfc compact="yes"?>
<?rfc text-list-symbols="ooo*+-"?>
<?rfc sortrefs="no"?>
<?rfc symrefs="yes"?>
<?rfc strict="yes"?>
<?rfc toc="yes"?>
<front>
<title abbrev="Multicast Across Inter-Domain Peering Points">Use of Multicast Across Inter-Domain Peering Points</title>
<author role="editor" fullname="Percy S. Tarapore" initials="P.S." surname="Tarapore">
<organization>AT&T</organization>
<address><phone>1-732-420-4172</phone><email>tarapore@att.com</email>
</address>
</author>
<author fullname="Robert Sayko" initials="R." surname="Sayko">
<organization>AT&T</organization>
<address><phone>1-732-420-3292</phone><email>rs1983@att.com</email>
</address>
</author>
<author fullname="Greg Shepherd" initials="G." surname="Shepherd">
<organization>Cisco</organization>
<address><email>shep@cisco.com</email>
</address>
</author>
<author role="editor" fullname="Toerless Eckert" initials="T." surname="Eckert">
<organization abbrev="Futurewei Technologies">Futurewei Technologies Inc.</organization>
<address><email>tte@cs.fau.de</email>
</address>
</author>
<author fullname="Ram Krishnan" initials="R." surname="Krishnan">
<organization>SupportVectors</organization>
<address><email>ramkri123@gmail.com</email>
</address>
</author>
<date day="27" month="October" year="2017"/>
<workgroup>MBONED Working Group</workgroup>
<abstract><t>
This document examines the use of Source Specific Multicast (SSM)
across inter-domain peering points for a specified set of deployment
scenarios. The objective is to describe the setup process for
multicast-based delivery across administrative domains for these
scenarios and document supporting functionality to enable this
process.</t>
</abstract>
</front>
<middle>
<section title="Introduction" anchor="section-1"><t>
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/data offers significant savings of utilization of resources
in any given administrative domain. End user demand for such
content/data is growing. Often, this requires transporting the
content/data across administrative domains via inter-domain peering
points.</t>
<t>The objective of this Best Current Practices document is twofold:
<list style="symbols">
<t>Describe the technical process and establish guidelines for
setting up multicast-based delivery of application content/data
across inter-domain peering points via a set of use cases.</t>
<t>Catalog all required information exchange between the
administrative domains to support multicast-based delivery.
This enables operators to initiate necessary processes to
support inter-domain peering with multicast.</t>
</list>
</t>
<t>The scope and assumptions for this document are stated as follows:
<list style="symbols">
<t>For the purpose of this document, the term "peering point"
refers to an interface between two networks/administrative
domains over which traffic is exchanged between them. A
Network-Network Interface (NNI) is an example of a peering
point.</t>
<t>Administrative Domain 1 (AD-1) is enabled with native
multicast. A peering point exists between AD-1 and AD-2.</t>
<t>It is understood that several protocols are available for this
purpose including PIM-SM and Protocol Independent Multicast -
Source Specific Multicast (PIM-SSM) <xref target="RFC7761"/>, Internet Group
Management Protocol (IGMP) <xref target="RFC3376"/>, and Multicast Listener
Discovery (MLD) <xref target="RFC3810"/>.</t>
<t>As described in <xref target="section-2"/>, the source IP address of the
multicast stream in the originating AD (AD-1) is known. Under
this condition, PIM-SSM use is beneficial as it allows the
receiver's upstream router to directly send a JOIN message to
the source without the need of invoking an intermediate
Rendezvous Point (RP). Use of SSM also presents an improved
threat mitigation profile against attack, as described in
<xref target="RFC4609"/>. Hence, in the case of inter-domain peering, it is
recommended to use only SSM protocols; the setup of inter-
domain peering for ASM (Any-Source Multicast) is not in scope
for this document.</t>
<t>AD-1 and AD-2 are assumed to adopt compatible protocols. The
use of different protocols is beyond the scope of this
document.</t>
<t>An Automatic Multicast Tunnel (AMT) <xref target="RFC7450"/> is setup at the
peering point if either the peering point or AD-2 is not
multicast enabled. It is assumed that an AMT Relay 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 AMT use is necessary only when native
multicast is unavailable in the peering point (Use Case 3.3) or
in the downstream administrative domain (Use Cases 3.4, and
3.5).</t>
<t>The collection of billing data is assumed to be done at the
application level and is not considered to be a networking
issue. The settlements process for end user billing and/or
inter-provider billing is out of scope for this document.</t>
<t>Inter-domain network connectivity troubleshooting is only
considered within the context of a cooperative process between
the two domains.</t>
</list>
</t>
<t>Thus, the primary purpose of this document is to describe a scenario
where two AD's interconnect via a a peering point with each other.
Security and operational aspects for exchanging traffic on a public
Internet Exchange Point (IXP) with a large shared broadcast domain
between many operators, is not in scope for this document.
</t>
<t>
It may be possible to have a configuration whereby a transit domain
(AD-3) interconnects AD-1 and AD-2. Such a configuration adds
complexity and may require manual provisioning if, for example, AD-3
is not multicast enabled. This configuration is out of cope for this
document; it is for further study.</t>
<t>
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.</t>
</section>
<section title="Overview of Inter-domain Multicast Application Transport" anchor="section-2">
<t>A multicast-based application delivery scenario is as follows:
<list style="symbols">
<t>Two independent administrative domains are interconnected via a peering point.</t>
<t>The peering point is either multicast enabled (end-to-end
native multicast across the two domains) or it is connected by
one of two possible tunnel types:
<list style="symbols">
<t>A Generic Routing Encapsulation (GRE) Tunnel <xref target="RFC2784"/>
allowing multicast tunneling across the peering point, or</t>
<t>An Automatic Multicast Tunnel (AMT) <xref target="RFC7450"/>.</t>
</list>
</t>
<t>A service provider controls one or more application sources in
AD-1 which will send multicast IP packets for one or more
(S,G)s. It is assumed that the service being provided is
suitable for delivery via multicast (e.g. live video streaming
of popular events, software downloads to many devices, etc.),
and that the packet streams will be part of a suitable
multicast transport protocol.</t>
<t>An End User (EU) controls a device connected to AD-2, which
runs an application client compatible with the service
provider's application source.</t>
<t>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
application, and are out of scope for this document.</t>
</list>
</t>
<t>
The assumption here is that AD-1 has ultimate responsibility for
delivering the multicast based service on behalf of the content
source(s). All relevant interactions between the two domains
described in this document are based on this assumption.</t>
<t>
Note that domain 2 may be an independent network domain (e.g., Tier
1 network operator domain). Alternately, domain 2 could also be an
Enterprise network domain operated by a single customer. The peering
point architecture and requirements may have some unique aspects
associated with the Enterprise case.</t>
<t>
The Use Cases describing various architectural configurations for
the multicast distribution along with associated requirements is
described in section 3. Unique aspects related to the Enterprise
network possibility will be described in this section. <xref target="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.</t>
</section>
<section title="Inter-domain Peering Point Requirements for Multicast" anchor="section-3">
<t>
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.</t>
<section title="Native Multicast" anchor="section-3.1">
<t>
This Use Case involves end-to-end Native Multicast between the two
administrative domains and the peering point is also native
multicast enabled - Figure 1.</t>
<figure title="- Content Distribution via End to End Native Multicast" anchor="ref-content-distribution-via-end-to-end-native-multicast"><artwork><![CDATA[
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | AS |------>| BR |-|---------|->| BR |-------------|-->| EU |
| | | +------+ | I1 | +------+ |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AD = Administrative Domain (Independent Autonomous System)
AS = Application (e.g., Content) Multicast Source
BR = Border Router
I1 = AD-1 and AD-2 Multicast Interconnection (e.g., MBGP)
I2 = AD-2 and EU Multicast Connection
]]></artwork>
</figure>
<t>Advantages of this configuration are:
<list style="symbols">
<t>Most efficient use of bandwidth in both domains.</t>
<t>Fewer devices in the path traversed by the multicast stream when
compared to an AMT enabled peering point.</t>
</list>
</t>
<t>
From the perspective of AD-1, the one disadvantage associated with
native multicast into 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
End Users 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 application layer mechanisms for
generating this information need to be robust enough such 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.</t>
<t>Architectural guidelines for this configuration are as follows:
<list style="letters">
<t>Dual homing for peering points between domains is recommended
as a way to ensure reliability with full BGP table visibility.</t>
<t>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 non-
rate adaptive multicast traffic. If this is not the case, then
it is recommended that the multicast traffic should support
rate-adaption.</t>
<t>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.</t>
<t>Relevant information on multicast streams delivered to End
Users in AD-2 is assumed to be 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.</t>
<t>The interconnection of AD-1 and AD-2 should, at a minimum,
follow guidelines for traffic filtering between autonomous
systems <xref target="BCP38"/>. Filtering guidelines specific to the multicast
control-plane and data-plane are described in section 6.</t>
</list>
</t>
</section>
<section title="Peering Point Enabled with GRE Tunnel" anchor="section-3.2">
<t>
The peering point is not native multicast enabled in this Use Case.
There is a Generic Routing Encapsulation Tunnel provisioned over the
peering point. In this case, the interconnection I1 between AD-1 and
AD-2 in Figure 1 is multicast enabled via a Generic Routing
Encapsulation Tunnel (GRE) <xref target="RFC2784"/> and encapsulating the multicast
protocols across the interface. The routing configuration is
basically unchanged: Instead of BGP (SAFI2) across the native IP
multicast link between AD-1 and AD-2, BGP (SAFI2) is now run across
the GRE tunnel.</t>
<t>Advantages of this configuration:
<list style="symbols">
<t>Highly efficient use of bandwidth in both domains, although not
as efficient as the fully native multicast Use Case.</t>
<t>Fewer devices in the path traversed by the multicast stream
when compared to an AMT enabled peering point.</t>
<t>Ability to support only partial IP multicast deployments in AD-
1 and/or AD-2 (the two Border Routers in Figure 1 do not need
to be the two "unicast" domain border routers; instead they can
be anywhere in AD-1 and AD-2).</t>
<t>GRE is an existing technology and is relatively simple to
implement.</t>
</list>
</t>
<t>Disadvantages of this configuration:
<list style="symbols">
<t>Per Use Case 3.1, current router technology cannot count the
number of end users or the number bytes transmitted.</t>
<t>GRE tunnel requires manual configuration.</t>
<t>The GRE must be established prior to stream starting.</t>
<t>The GRE tunnel is often left pinned up.</t>
</list>
</t>
<t>
Architectural guidelines for this configuration include the
following:</t>
<t>
Guidelines (a) through (d) are the same as those described in Use
Case 3.1. Two additional guidelines are as follows:</t>
<t><list hangIndent="3" style="hanging">
<t hangText="e.">
GRE tunnels are typically configured manually between peering
points to support multicast delivery between domains.</t>
<t hangText="f.">
It is recommended that the GRE tunnel (tunnel server)
configuration in the source network is 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 (e.g., if application - e.g.,
content - is not part of an agreed inter-domain partnership).</t>
</list></t>
</section>
<section title="Peering Point Enabled with an AMT - Both Domains Multicast Enabled" anchor="section-3.3">
<t>
Both administrative domains in this Use Case are assumed to be
native multicast enabled here; however, the peering point is not.</t>
<t>
The peering point is enabled with an Automatic Multicast Tunnel. The
basic configuration is depicted in Figure 2.</t>
<figure title="- AMT Interconnection between AD-1 and AD-2" anchor="ref-amt-interconnection-between-ad-1-and-ad-2"><artwork><![CDATA[
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | AS |------>| AR |-|---------|->| AG |-------------|-->| EU |
| | | +------+ | I1 | +------+ |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AR = AMT Relay
AG = AMT Gateway
I1 = AMT Interconnection between AD-1 and AD-2
I2 = AD-2 and EU Multicast Connection
]]></artwork>
</figure>
<t>Advantages of this configuration:
<list style="symbols">
<t>Highly efficient use of bandwidth in AD-1.</t>
<t>AMT is an existing technology and is relatively simple to
implement. Attractive properties of AMT include the following:
<list style="symbols">
<t>Dynamic interconnection between Gateway-Relay pair across
the peering point.</t>
<t>Ability to serve clients and servers with differing
policies.</t>
</list>
</t>
</list>
</t>
<t>Disadvantages of this configuration:
<list style="symbols">
<t>Per Use Case 3.1 (AD-2 is native multicast), current router
technology cannot count the number of end users or the number
of bytes transmitted to all end users.</t>
<t>Additional devices (AMT Gateway and Relay pairs) may be
introduced into the path if these services are not incorporated
in the existing routing nodes.</t>
<t>Currently undefined mechanisms for the AG to automatically
select the optimal AR.</t>
</list>
</t>
<t>Architectural guidelines for this configuration are as follows:</t>
<t>
Guidelines (a) through (d) are the same as those described in Use
Case 3.1. In addition,</t>
<t><list hangIndent="3" style="hanging">
<t hangText="e.">
It is recommended that AMT Relay and Gateway 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 Gateway in AD-2 receives the
(S, G) information from the EU.</t>
</list></t>
</section>
<section title="Peering Point Enabled with an AMT - AD-2 Not Multicast Enabled" anchor="section-3.4">
<t>
In this AMT Use Case, the second administrative domain AD-2 is not
multicast enabled. Hence, the interconnection between AD-2 and the
End User is also not multicast enabled. This Use Case is depicted in
Figure 3.</t>
<figure title="- AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway" anchor="ref-amt-tunnel-connecting-ad-1-amt-relay-and-eu-gateway"><artwork><![CDATA[
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Non-Multicast \
/ \ / Enabled) \
| +----+ | | |
| | | +------+ | | | +----+
| | AS |------>| AR |-|---------|-----------------------|-->|EU/G|
| | | +------+ | | |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AS = Application Multicast Source
AR = AMT Relay
EU/G = Gateway client embedded in EU device
I2 = AMT Tunnel Connecting EU/G to AR in AD-1 through Non-Multicast
Enabled AD-2.
]]></artwork>
</figure>
<t>
This Use Case 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 End Users 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 End User.</t>
<t>Advantages of this configuration:
<list style="symbols"><t>Highly efficient use of bandwidth in AD-1.</t>
<t>AMT is an existing technology and is relatively simple to
implement. Attractive properties of AMT include the following:
<list style="symbols"><t>Dynamic interconnection between Gateway-Relay pair across
the peering point.</t>
<t>Ability to serve clients and servers with differing
policies.</t>
</list>
</t>
<t>Each AMT tunnel serves as a count for each End User and is also
able to track data usage (bytes) delivered to the EU.</t>
</list>
</t>
<t>Disadvantages of this configuration:
<list style="symbols">
<t>Additional devices (AMT Gateway and Relay pairs) are introduced
into the transport path.</t>
<t>Assuming multiple peering points between the domains, the EU
Gateway needs to be able to find the "correct" AMT Relay in AD-1.</t>
</list>
</t>
<t>Architectural guidelines for this configuration are as follows: </t>
<t>
Guidelines (a) through (c) are the same as those described in Use
Case 3.1.</t>
<t><list hangIndent="3" style="hanging">
<t hangText="d.">
It is recommended that proper procedures are implemented such
that the AMT Gateway at the End User device is able to find the
correct AMT Relay in AD-1 across the peering points. The
application client in the EU device is expected to supply the (S,
G) information to the Gateway for this purpose.</t>
<t hangText="e.">
The AMT tunnel capabilities are expected to be sufficient for
the purpose of collecting relevant information on the multicast
streams delivered to End Users in AD-2.</t>
</list>
</t>
</section>
<section title="AD-2 Not Multicast Enabled - Multiple AMT Tunnels Through AD-2" anchor="section-3.5">
<t>This is a variation of Use Case 3.4 as follows:</t>
<figure title="- AMT Tunnel Connecting AMT Relay and Relays" anchor="ref-amt-tunnel-connecting-amt-relay-and-relays"><artwork><![CDATA[
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Non-Multicast \
/ \ / Enabled) \
| +----+ | |+--+ +--+ |
| | | +------+ | ||AG| |AG| | +----+
| | AS |------>| AR |-|-------->||AR|------------->|AR|-|-->|EU/G|
| | | +------+ | I1 ||1 | I2 |2 | |I3 +----+
\ +----+ / \+--+ +--+ /
\ / \ /
\ / \ /
------------------- -------------------
AS = Application Source
AR = AMT Relay in AD-1
AGAR1 = AMT Gateway/Relay node in AD-2 across Peering Point
I1 = AMT Tunnel Connecting AR in AD-1 to GW in AGAR1 in AD-2
AGAR2 = AMT Gateway/Relay node at AD-2 Network Edge
I2 = AMT Tunnel Connecting Relay in AGAR1 to GW in AGAR2
EU/G = Gateway client embedded in EU device
I3 = AMT Tunnel Connecting EU/G to AR in AGAR2
]]></artwork>
</figure>
<t>
Use Case 3.4 results in several long AMT tunnels crossing the entire
network of AD-2 linking the EU device and the AMT Relay in AD-1
through the peering point. Depending on the number of End Users,
there is a likelihood of an unacceptably large number of AMT tunnels
- and unicast streams - through the peering point. This situation
can be alleviated as follows:</t>
<t><list style="symbols"><t>Provisioning of strategically located AMT nodes at the edges of
AD-2. An AMT node comprises co-location of an AMT Gateway and
an AMT Relay. One such node is at the AD-2 side of the peering
point (node AGAR1 in Figure 4).</t>
<t>Single AMT tunnel established across peering point linking AMT
Relay in AD-1 to the AMT Gateway in the AMT node AGAR1 in AD-2.</t>
<t>AMT tunnels linking AMT node AGAR1 at peering point in AD-2 to
other AMT nodes located at the edges of AD-2: e.g., AMT tunnel
I2 linking AMT Relay in AGAR1 to AMT Gateway in AMT node AGAR2
in Figure 4.</t>
<t>AMT tunnels linking EU device (via Gateway client embedded in
device) and AMT Relay in appropriate AMT node at edge of AD-2:
e.g., I3 linking EU Gateway in device to AMT Relay in AMT node
AGAR2.</t>
</list>
</t>
<t>
The advantage for 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 of 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 Gateways 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.</t>
<t>Architectural guidelines for this configuration are as follows:</t>
<t>
Guidelines (a) through (c) are the same as those described in Use
Case 3.1.</t>
<t><list hangIndent="3" style="hanging">
<t hangText="d.">
It is recommended that proper procedures are implemented such
that the various AMT Gateways (at the End User devices and the AMT
nodes in AD-2) are able to find the correct AMT Relay in other AMT
nodes as appropriate. The application client in the EU device is
expected to supply the (S, G) information to the Gateway for this
purpose.</t>
<t hangText="e.">
The AMT tunnel capabilities are expected to be sufficient for
the purpose of collecting relevant information on the multicast
streams delivered to End Users in AD-2.</t>
</list>
</t>
</section>
</section>
<section title="Functional Guidelines" anchor="section-4"><t>
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.</t>
<section title="Network Interconnection Transport and Security Guidelines" anchor="section-4.1">
<t>
The term "Network Interconnection Transport" refers to the
interconnection points between the two Administrative Domains. The
following is a representative set of attributes that will need to be
agreed to between the two administrative domains to support
multicast delivery.</t>
<t><list style="symbols"><t>Number of Peering Points.</t>
<t>Peering Point Addresses and Locations.</t>
<t>Connection Type - Dedicated for Multicast delivery or shared
with other services.</t>
<t>Connection Mode - Direct connectivity between the two AD's or
via another ISP.</t>
<t>Peering Point Protocol Support - Multicast protocols that will
be used for multicast delivery will need to be supported at
these points. Examples of protocols include eBGP <xref target="RFC4760"/> and
MBGP <xref target="RFC4760"/>.</t>
<t>Bandwidth Allocation - If shared with other services, then
there needs to be a determination of the share of bandwidth
reserved for multicast delivery. When determining the
appropriate bandwidth allocation, parties should consider use
of a multicast protocol suitable for live video streaming that
is consistent with Congestion Control Principles <xref target="BCP41"/>.</t>
<t>QoS Requirements - Delay/latency specifications that need to be
specified in an SLA.</t>
<t>AD Roles and Responsibilities - the role played by each AD for
provisioning and maintaining the set of peering points to
support multicast delivery.</t>
</list>
</t>
</section>
<section title="Routing Aspects and Related Guidelines" anchor="section-4.2">
<t>
The main objective for multicast delivery routing is to ensure that
the End User receives the multicast stream from the "most optimal"
source <xref target="INF_ATIS_10"/> which typically:</t>
<t><list style="symbols"><t>Maximizes the multicast portion of the transport and minimizes
any unicast portion of the delivery, and</t>
<t>Minimizes the overall combined network(s) route distance.</t>
</list>
</t>
<t>
This routing objective applies to both Native and AMT; the actual
methodology of the solution will be different for each. Regardless,
the routing solution is expected:</t>
<t><list style="symbols"><t>To be scalable,</t>
<t>To avoid/minimize new protocol development or modifications,
and</t>
<t>To be robust enough to achieve high reliability and
automatically adjust to changes/problems in the multicast
infrastructure.</t>
</list>
</t>
<t>
For both Native 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.</t>
<section title="Native Multicast Routing Aspects" anchor="section-4.2.1">
<t>
Native multicast simply requires that the Administrative Domains
coordinate and advertise the correct source address(es) at their
network interconnection peering points(i.e., border routers). An
example of multicast delivery via a Native Multicast process across
two Administrative Domains is as follows assuming that the
interconnecting peering points are also multicast enabled:</t>
<t><list style="symbols"><t>Appropriate information is obtained by the EU client who is a
subscriber to AD-2 (see Use Case 3.1). This information is in
the form of metadata 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) id in the form of the
"S,G" data. The "S" portion provides the name or IP address of
the source of the multicast stream. The metadata may also
contain alternate delivery information such as specifying the
unicast address of the stream.</t>
<t>The client uses the join message with S,G to join the multicast
stream <xref target="RFC4604"/>. To facilitate this process, the two AD's need to do the following:
<list style="symbols"><t>Advertise the source id(s) over the Peering Points.</t>
<t>Exchange relevant Peering Point information such as Capacity
and Utilization.</t>
<t>Implement compatible multicast protocols to ensure proper
multicast delivery across the peering points.</t>
</list>
</t>
</list>
</t>
</section>
<section title="GRE Tunnel over Interconnecting Peering Point" anchor="section-4.2.2">
<t>
If the interconnecting peering point is not multicast enabled and
both AD's are multicast enabled, then a simple solution is to
provision a GRE tunnel between the two AD's - see Use Case 3.2.2.
The termination points of the tunnel will usually be a network
engineering decision, but generally will be between the border
routers or even between the AD 2 border router and the AD 1 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 is still required.</t>
<t>
The two AD's need to follow the same process as described in 4.2.1
to facilitate multicast delivery across the Peering Points.</t>
</section>
<section title="Routing Aspects with AMT Tunnels" anchor="section-4.2.3">
<t>
Unlike Native Multicast (with or without GRE), an AMT Multicast
environment is more complex. It presents a dual layered problem
because there are two criteria that should be simultaneously met:</t>
<t><list style="symbols">
<t>Find the closest AMT relay to the end-user that also has
multicast connectivity to the content source, and</t>
<t>Minimize the AMT unicast tunnel distance.</t>
</list></t>
<t>There are essentially two components to the AMT specification</t>
<t><list style="hanging">
<t hangText="AMT Relays:">These serve the purpose of tunneling UDP multicast
traffic to the receivers (i.e., End-Points). The AMT Relay will
receive the traffic natively from the multicast media source and
will replicate the stream on behalf of the downstream AMT
Gateways, encapsulating the multicast packets into unicast
packets and sending them over the tunnel toward the AMT Gateway.
In addition, the AMT Relay may perform various usage and
activity statistics collection. This results in moving the
replication point closer to the end user, and cuts down on
traffic across the network. Thus, the linear costs of adding
unicast subscribers can be avoided. However, unicast replication
is still required for each requesting End-Point within the
unicast-only network.</t>
<t hangText="AMT Gateway (GW):"> The Gateway will reside on an End-Point - this
may be a Personal Computer (PC) or a Set Top Box (STB). The AMT
Gateway receives join and leave requests from the Application
via an Application Programming Interface (API). In this manner,
the Gateway allows the End-Point to conduct itself as a true
Multicast End-Point. The AMT Gateway will encapsulate AMT
messages into UDP packets and send them through a tunnel (across
the unicast-only infrastructure) to the AMT Relay.</t>
</list>
</t>
<t>
The simplest AMT Use Case (section 3.3) involves peering points that
are not multicast enabled between two multicast enabled AD's. An AMT
tunnel is deployed between an AMT Relay on the AD 1 side of the
peering point and an AMT Gateway on the AD 2 side of the peering
point. One advantage to this arrangement is that the tunnel is
established on an as needed basis and need not be a provisioned
element. The two AD's can coordinate and advertise special AMT Relay
Anycast addresses with each other. Alternately, they may decide to
simply provision Relay addresses, though this would not be an
optimal solution in terms of scalability.</t>
<t>
Use Cases 3.4 and 3.5 describe more complicated AMT situations as
AD-2 is not multicast enabled. For these cases, the End User device
needs to be able to setup an AMT tunnel in the most optimal manner.
There are many methods by which relay selection can be done
including the use of DNS based queries and static lookup tables
<xref target="RFC7450"/>. The choice of the method is implementation dependent and
is up to the network operators. Comparison of various methods is out
of scope for this document; it is for further study.</t>
<t>
An illustrative example of a relay selection based on DNS queries
and Anycast IP addresses process for Use Cases 3.4 and 3.5 is
described here. Using an Anycast IP address for AMT Relays allows
for all AMT Gateways to find the "closest" AMT Relay - the nearest
edge of the multicast topology of the source. Note that this is
strictly illustrative; the choice of the method is up to the network
operators. The basic process is as follows:</t>
<t><list style="symbols"><t>Appropriate metadata is obtained by the EU client application. The
metadata contains instructions directing the EU client to an
ordered list of particular destinations to seek the requested
stream and, for multicast, specifies the source location and the
group (or stream) ID in the form of the "S,G" data. The "S"
portion provides the URI (name or IP address) of the source of the
multicast stream and the "G" identifies the particular stream
originated by that source. The metadata may also contain alternate
delivery information such as the address of the unicast form of
the content to be used, for example, if the multicast stream
becomes unavailable.</t>
<t>Using the information from the metadata, and possibly information
provisioned directly in the EU client, a DNS query is initiated in
order to connect the EU client/AMT Gateway to an AMT Relay.</t>
<t>Query results are obtained, and may return an Anycast address or a
specific unicast address of a relay. Multiple relays will
typically exist. The Anycast address is a routable "pseudo-address" shared among the relays that can gain multicast access to
the source.</t>
<t>If a specific IP address unique to a relay was not obtained, the
AMT Gateway then sends a message (e.g., the discovery message) to
the Anycast address such that the network is making the routing
choice of particular relay - e.g., closest relay to the EU. (Note
that in IPv6 there is a specific Anycast format and Anycast is
inherent in IPv6 routing, whereas in IPv4 Anycast is handled via
provisioning in the network. Details are out of scope for this
document.)</t>
<t>The contacted AMT Relay then returns its specific unicast IP
address (after which the Anycast address is no longer required).
Variations may exist as well.</t>
<t>The AMT Gateway uses that unicast IP address to initiate a three-
way handshake with the AMT Relay.</t>
<t>AMT Gateway provides "S,G" to the AMT Relay (embedded in AMT
protocol messages).</t>
<t>AMT Relay receives the "S,G" information and uses the S,G to join
the appropriate multicast stream, if it has not already subscribed
to that stream.</t>
<t>AMT Relay encapsulates the multicast stream into the tunnel
between the Relay and the Gateway, providing the requested content
to the EU.</t>
</list>
</t>
</section>
</section>
<section title="Back Office Functions - Provisioning and Logging Guidelines" anchor="section-4.3">
<t>
Back Office refers to the following:</t>
<t><list style="symbols">
<t>Servers and Content Management systems that support the delivery
of applications via multicast and interactions between AD's.</t>
<t>Functionality associated with logging, reporting, ordering,
provisioning, maintenance, service assurance, settlement, etc.</t>
</list>
</t>
<section title="Provisioning Guidelines" anchor="section-4.3.1">
<t>
Resources for basic connectivity between AD's Providers need to be
provisioned as follows:</t>
<t><list style="symbols">
<t>Sufficient capacity must be provisioned to support multicast-based
delivery across AD's.</t>
<t>Sufficient capacity must be provisioned for connectivity between
all supporting back-offices of the AD's as appropriate. This
includes activating proper security treatment for these back-
office connections (gateways, firewalls, etc) as appropriate.</t>
<t>Routing protocols as needed, e.g. configuring routers to support
these.</t>
</list>
</t>
<t>
Provisioning aspects related to Multicast-Based inter-domain
delivery are as follows.</t>
<t>
The ability to receive requested application via multicast is
triggered via receipt of the necessary metadata. Hence, this
metadata must be provided to the EU regarding multicast URL - and
unicast fallback if applicable. AD-2 must enable the delivery of
this metadata to the EU and provision appropriate resources for this
purpose.</t>
<t>
Native multicast functionality is assumed to be available across
many ISP backbones, peering and access networks. If, however, native
multicast is not an option (Use Cases 3.4 and 3.5), then:</t>
<t><list style="symbols">
<t>EU must have multicast client to use AMT multicast obtained either
from Application Source (per agreement with AD-1) or from AD-1 or
AD-2 (if delegated by the Application Source).</t>
<t>If provided by AD-1/AD-2, then the EU could be redirected to a
client download site (note: this could be an Application Source
site). If provided by the Application Source, then this Source
would have to coordinate with AD-1 to ensure the proper client is
provided (assuming multiple possible clients).</t>
<t>Where AMT Gateways support different application sets, all AD-2
AMT Relays need to be provisioned with all source & group
addresses for streams it is allowed to join.</t>