MBONED Working Group Percy S. Tarapore
Internet Draft Robert Sayko
Intended status: BCP AT&T
Expires: April 21, 2014 Greg Shepherd
Toerless Eckert
Cisco
Ram Krishnan
Brocade
October 21, 2013
Multicasting Applications Across Inter-Domain Peering Points
draft-tarapore-mboned-multicast-cdni-04.txt
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Abstract
This document examines the process of transporting applications via
multicast across inter-domain peering points. The objective is to
describe the setup process for multicast-based delivery across
administrative domains and document supporting functionality to
enable this process.
Table of Contents
1. Introduction...................................................3
2. Overview of Inter-domain Multicast Application Transport.......3
3. Inter-domain Peering Point Requirements for Multicast..........5
3.1. Native Multicast..........................................5
3.2. Peering Point Enabled with GRE Tunnel.....................6
3.3. Peering Point Enabled with an AMT - Both Domains Multicast
Enabled........................................................8
3.4. Peering Point Enabled with an AMT - AD-2 Not Multicast
Enabled........................................................9
3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels Through
AD-2..........................................................11
4. Supporting Functionality......................................13
4.1. Network Transport and Security Guidelines................14
4.2. Routing Aspects and Related Guidelines...................14
4.3. Back Office Functions - Billing and Logging Guidelines...14
4.4. Operations - Service Performance and Monitoring Guidelines14
4.5. Reliability Models/Service Assurance Guidelines..........14
4.6. Provisioning Guidelines..................................14
4.7. Client Models............................................14
4.8. Addressing Guidelines....................................14
5. Security Considerations.......................................15
6. IANA Considerations...........................................15
7. Conclusions...................................................15
8. References....................................................15
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8.1. Normative References.....................................15
8.2. Informative References...................................15
9. Acknowledgments...............................................15
1. Introduction
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 applications offers significant
savings for utilization of resources in any given administrative
domain. End user demand for such applications is growing. Often,
this requires transporting such applications across administrative
domains via inter-domain peering points.
The objective of this Best Current Practices document is twofold:
o Describe the process and establish guidelines for setting up
multicast-based delivery of applications across inter-domain
peering points, and
o Catalog all required information exchange between the
administrative domains to support multicast-based delivery.
While there are several multicast protocols available for use, this
BCP will focus the discussion to those that are applicable and
recommended for the peering requirements of today's service model,
including:
o Protocol Independent Multicast - Source Specific Multicast
(PIM-SSM) [RFC4607]
o Internet Group Management Protocol (IGMP) v3 [RFC4604]
o Multicast Listener Discovery (MLD) [RFC4604]
This document therefore serves the purpose of a "Gap Analysis"
exercise for this process. The rectification of any gaps identified
- whether they involve protocol extension development or otherwise -
is beyond the scope of this document and is for further study.
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.
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o 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:
o A Generic Routing Encapsulation (GRE) Tunnel [RFC2784]
allowing multicast tunneling across the peering point, or
o An Automatic Multicast Tunnel (AMT) [IETF-ID-AMT].
o The application stream originates at a source in Domain 1.
o An End User associated with Domain 2 requests the application.
It is assumed that the application is suitable for delivery via
multicast means (e.g., live steaming of major events, software
downloads to large numbers of end user devices, etc.)
o The request is communicated to the application source which
provides the relevant multicast delivery information to the EU
device via a "manifest file". At a minimum, this file contains
the {Source, Group} or (S,G) information relevant to the
multicast stream.
o The application client in the EU device then joins the
multicast stream distributed by the application source in
domain 1 utilizing the (S,G) information provided in the
manifest file. The manifest file may also contain additional
information that the application client can use to locate the
source and join the stream.
It should be noted that the second administrative domain - domain 2
- may be an independent network domain (e.g., Tier 1 network
operator domain) or it could also be an Enterprise network operated
by a single customer. The peering point architecture and
requirements may have some unique aspects associated with the
Enterprise case.
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. A
comprehensive list of pertinent information that needs to be
exchanged between the two domains to support various functions
enabling the application transport is provided in section 4.
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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 three possible Use Cases for consideration.
3.1. Native Multicast
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.
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | CS |------>| BR |-|---------|->| BR |-------------|-->| EU |
| | | +------+ | I1 | +------+ |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AD = Administrative Domain (Independent Autonomous System)
CS = Content Multicast Source
BR = Border Router
I1 = AD-1 and AD-2 Multicast Interconnection (MBGP or BGMP)
I2 = AD-2 and EU Multicast Connection
Figure 1 - Content Distribution via End to End Native Multicast
Advantages of this configuration are:
o Most efficient use of bandwidth in both domains
o Fewer devices in the path traversed by the multicast stream
when compared to unicast transmissions.
From the perspective of AD-1, the one disadvantage associated with
native multicast into AD-2 instead of individual unicast to every EU
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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.
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 non-
rate adaptive multicast traffic. If this is not the case, then
it is recommended that the multicast traffic should support
rate-adaption.
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.
d. 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.
3.2. Peering Point Enabled with GRE Tunnel
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) [RFC2784] and encapsulating the multicast
protocols across the interface. The routing configuration is
basically unchanged: Instead of BGP (SAFI2) across the native IP
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multicast link between AD-1 and AD-2, BGP (SAFI2) 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 Use Case.
o Fewer devices in the path traversed by the multicast stream
when compared to unicast transmissions.
o Ability to support only partial IP multicast deployments in AD-
1 and/or AD-2.
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 end users or the number bytes transmitted.
o GRE tunnel requires manual configuration.
o GRE must be in place prior to stream starting.
o GRE 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.
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 is such that it only
advertises the routes to the content sources and not to the
entire network. This practice will prevent unauthorized
delivery of content through the tunnel (e.g., if content is not
part of an agreed CDN partnership).
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3.3. Peering Point Enabled with an AMT - Both Domains Multicast
Enabled
Both administrative domains in this Use Case are assumed to be
native multicast enabled here; however the peering point is not. The
peering point is enabled with an Automatic Multicast Tunnel. The
basic configuration is depicted in Figure 2.
------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Multicast Enabled) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | CS |------>| AR |-|---------|->| AG |-------------|-->| EU |
| | | +------+ | I1 | +------+ |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
AR = AMT Relay
AG = AMT Gateway
I1 = AMT Interconnection between P-CDN and S-CDN
I2 = S-CDN and EU Multicast Connection
Figure 2 - 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:
o Dynamic interconnection between Gateway-Relay pair across
the peering point.
o Ability to serve clients and servers with differing
policies.
Disadvantages of this configuration:
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o Per Use Case 3.1 (AD-2 is native multicast), current router
technology cannot count the number of end users or the number
bytes transmitted.
o Additional devices (AMT Gateway and Relay pairs) may be
introduced into the path if these services are not incorporated
in the existing routing nodes.
o Currently undefined mechanisms to select the AR from the AG
automatically.
Architectural guidelines for this configuration are as follows:
Guidelines (a) through (d) are the same as those described in Use
Case 3.1.
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.
3.4. Peering Point Enabled with an AMT - AD-2 Not Multicast Enabled
In this AMT Use Case, the second administrative domain AD-2 is not
multicast enabled. This implies that the interconnection between AD-
2 and the End User is also not multicast enabled as depicted in
Figure 3.
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------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Non-Multicast \
/ \ / Enabled) \
| +----+ | | |
| | | +------+ | | | +----+
| | CS |------>| AR |-|---------|-----------------------|-->|EU/G|
| | | +------+ | | |I2 +----+
\ +----+ / \ /
\ / \ /
\ / \ /
------------------- -------------------
CS = Content 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.
Figure 3 - AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway
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.
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:
o Dynamic interconnection between Gateway-Relay pair across
the peering point.
o Ability to serve clients and servers with differing
policies.
o Each AMT tunnel serves as a count for each End User and is also
able to track data usage (bytes) delivered to the EU.
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Disadvantages of this configuration:
o Additional devices (AMT Gateway and Relay pairs) are introduced
into the transport path.
o Assuming multiple peering points between the domains, the EU
Gateway needs to be able to find the "correct" AMT Relay 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.
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.
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.
3.5. AD-2 Not Multicast Enabled - Multiple AMT Tunnels Through AD-2
This is a variation of Use Case 3.4 as follows:
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------------------- -------------------
/ AD-1 \ / AD-2 \
/ (Multicast Enabled) \ / (Non-Multicast \
/ \ / Enabled) \
| +----+ | |+--+ +--+ |
| | | +------+ | ||AG| |AG| | +----+
| | CS |------>| AR |-|-------->||AR|------------->|AR|-|-->|EU/G|
| | | +------+ | I1 ||1 | I2 |2 | |I3 +----+
\ +----+ / \+--+ +--+ /
\ / \ /
\ / \ /
------------------- -------------------
(Note: Diff-marks for the figure have been removed to improve
viewing)
CS = Content 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
Figure 4 - AMT Tunnel Connecting AD-1 AMT Relay and EU Gateway
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:
o 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).
o 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.
o 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
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I2 linking AMT Relay in AGAR1 to AMT Gateway in AMT node AGAR2
in Figure 4.
o 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.
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.
Architectural guidelines for this configuration are as follows:
Guidelines (a) through (c) are the same as those described in Use
Case 3.1.
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.
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.
4. Supporting Functionality
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.
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4.1. Network Transport and Security Guidelines
4.2. Routing Aspects and Related Guidelines
4.3. Back Office Functions - Billing and Logging Guidelines
4.4. Operations - Service Performance and Monitoring Guidelines
4.5. Reliability Models/Service Assurance Guidelines
4.6. Provisioning Guidelines
In order to find right relay there is a need for a small/light
implementation of an AMT DNS in source network.
4.7. Client Models
4.8. Addressing Guidelines
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5. Security Considerations
(Include discussion on DRM, AAA, Network Security)
6. IANA Considerations
7. Conclusions
8. References
8.1. Normative References
[RFC2784] D. Farinacci, T. Li, S. Hanks, D. Meyer, P. Traina,
"Generic Routing Encapsulation (GRE)", RFC 2784, March 2000
[IETF-ID-AMT] G. Bumgardner, "Automatic Multicast Tunneling", draft-
ietf-mboned-auto-multicast-13, April 2012, Work in progress
[RFC4604] H. Holbrook, et al, "Using Internet Group Management
Protocol Version 3 (IGMPv3) and Multicast Listener Discovery
Protocol Version 2 (MLDv2) for Source Specific Multicast", RFC 4604,
August 2006
[RFC4607] H. Holbrook, et al, "Source Specific Multicast", RFC 4607,
August 2006
8.2. Informative References
9. Acknowledgments
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Authors' Addresses
Percy S. Tarapore
AT&T
Phone: 1-732-420-4172
Email: tarapore@att.com
Robert Sayko
AT&T
Phone: 1-732-420-3292
Email: rs1983@att.com
Greg Shepherd
Cisco
Phone:
Email: shep@cisco.com
Toerless Eckert
Cisco
Phone:
Email: eckert@cisco.com
Ram Krishnan
Brocade
Phone:
Email: ramk@brocade.com
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