Internet DRAFT - draft-tarapore-mboned-multicast-cdni
draft-tarapore-mboned-multicast-cdni
MBONED Working Group Percy S. Tarapore
Internet Draft Robert Sayko
Intended status: BCP AT&T
Expires: April 27, 2015 Greg Shepherd
Toerless Eckert
Cisco
Ram Krishnan
Brocade
October 27, 2014
Multicasting Applications Across Inter-Domain Peering Points
draft-tarapore-mboned-multicast-cdni-07.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.......4
3. Inter-domain Peering Point Requirements for Multicast..........5
3.1. Native Multicast..........................................5
3.2. Peering Point Enabled with GRE Tunnel.....................7
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 Interconnection Transport and Security Guidelines14
4.2. Routing Aspects and Related Guidelines...................15
4.2.1 Native Multicast Routing Aspects..................15
4.2.2 GRE Tunnel over Interconnecting Peering Point.....16
4.2.3 Routing Aspects with AMT Tunnels.....................16
4.3. Back Office Functions - Billing and Logging Guidelines...19
4.3.1 Provisioning Guidelines...........................19
4.3.2 Application Accounting Billing Guidelines.........20
4.3.3 Log Management Guidelines.........................21
4.3.4 Settlement Guidelines.............................21
4.4. Operations - Service Performance and Monitoring Guidelines22
4.5. Client Reliability Models/Service Assurance Guidelines...24
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5. Security Considerations.......................................25
6. IANA Considerations...........................................25
7. Conclusions...................................................25
8. References....................................................26
8.1. Normative References.....................................26
8.2. Informative References...................................26
9. Acknowledgments...............................................26
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 sSeveral multicast protocols are 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 BCP is independent of the choice of multicast protocol; it
focuses solely on the implications for the inter-domain peering
points.
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.
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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 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.
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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.
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) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | 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 (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:
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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
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:
o Dual homing for peering points between domains is recommended
as a way to ensure reliability with full BGP table visibility.
o 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.
o 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.
o 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.
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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
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.
o GRE tunnels are typically configured manually between peering
points to support multicast delivery between domains.
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o 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).
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) \
/ \ / \
| +----+ | | |
| | | +------+ | | +------+ | +----+
| | 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
Figure 2 - AMT Interconnection between AD-1 and AD-2
Advantages of this configuration:
o Highly efficient use of bandwidth in AD-1.
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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:
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) \
| +----+ | | |
| | | +------+ | | | +----+
| | 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.
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| | +----+
| | AS |------>| AR |-|-------->||AR|------------->|AR|-|-->|EU/G|
| | | +------+ | I1 ||1 | I2 |2 | |I3 +----+
\ +----+ / \+--+ +--+ /
\ / \ /
\ / \ /
------------------- -------------------
(Note: Diff-marks for the figure have been removed to improve
viewing)
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
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 Interconnection Transport and Security Guidelines
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.
o Number of Peering Points
o Peering Point Addresses and Locations
o Connection Type - Dedicated for Multicast delivery or shared
with other services
o Connection Mode - Direct connectivity between the two AD's or
via another ISP
o 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, BGMP, and
MBGP.
o Bandwidth Allocation - If shared with other services, then
there needs to be a determination of the share of bandwidth
reserved for multicast delivery.
o QoS Requirements - Delay/latency specifications that need to be
specified in an SLA.
o AD Roles and Responsibilities - the role played by each AD for
provisioning and maintaining the set of peering points to
support multicast delivery.
From a security perspective, it is expected that normal/typical
security procedures will be followed by each AD to facilitate
multicast delivery to registered and authenticated end users. Some
security aspects for consideration are:
o Encryption - Peering point links may be encrypted per agreement
if dedicated for multicast delivery.
o Security Breach Mitigation Plan - In the event of a security
breach, the two AD's are expected to have a mitigation plan for
shutting down the peering point and directing multicast traffic
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over alternated peering points. It is also expected that
appropriate information will be shared for the purpose of
securing the identified breach.
4.2. Routing Aspects and Related Guidelines
The main objective for multicast delivery routing is to ensure that
the End User receives the multicast stream from the "most optimal"
source [INF_ATIS_10] which typically:
o Maximizes the multicast portion of the transport and minimizes
any unicast portion of the delivery, and
o Minimizes the overall combined network(s) route distance.
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 to be:
o Scalable
o Avoid/minimize new protocol development or modifications, and
o Be robust enough to achieve high reliability and automatically
adjust to changes/problems in the multicast infrastructure.
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, but that is entirely an implementation issue.
4.2.1 Native Multicast Routing Aspects
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:
o Appropriate information is obtained by the EU client who is a
subscriber to AD-2 (see Use Case 3.1). This is usually done via
an appropriate file transfer - this file is typically known as
the manifest file. It contains instructions directing the EU
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client to launch an appropriate application if necessary, and
also 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 file may also contain
alternate delivery information such as specifying the unicast
address of the stream.
o The client uses the join message with S,G to join the multicast
stream [RFC2236].
To facilitate this process, the two AD's need to do the following:
o Advertise the source id(s) over the Peering Points
o Exchange relevant Peering Point information such as Capacity
and Utilization (Other??)
4.2.2 GRE Tunnel over Interconnecting Peering Point
If the interconnecting peering point is not multicast enabled and
both ADs are multicast enabled, then a simple solution is to
provision a GRE tunnel between the two ADs - 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.
The two AD's need to follow the same process as described in 4.2.1
to facilitate multicast delivery across the Peering Points.
4.2.3 Routing Aspects with AMT Tunnels
Unlike Native (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 meet:
o Find the closest AMT relay to the end-user that also has
multicast connectivity to the content source and
o Minimize the AMT unicast tunnel distance.
There are essentially two components to the AMT specification:
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o 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 endpoint within the
unicast-only network.
o AMT Gateway (GW): The Gateway will reside on an on 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 endpoint 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.
The simplest AMT Use Case (section 3.3) involves peering points that
are not multicast enabled between two multicast enabled ADs. 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 ADs can coordinate and advertise special AMT Relay
Anycast addresses with each other - though they may alternately
decide to simply provision Relay addresses, though this would not be
a optimal solution in terms of scalability.
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.
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. An example of a basic delivery
via an AMT Multicast process for these two Use Cases is as follows:
o The manifest file is obtained by the EU client application. This
file 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
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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 manifest file 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.
o Using the information in the manifest file, 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.
o 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.
o 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.)
o 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.
o The AMT Gateway uses that unicast IP address to initiate a three-
way handshake with the AMT Relay.
o AMT Gateway provides "S,G" to the AMT Relay (embedded in AMT
protocol messages).
o 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.
o AMT Relay encapsulates the multicast stream into the tunnel
between the Relay and the Gateway, providing the requested content
to the EU.
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Note: Further routing discussion on optimal method to find "best AMT
Relay/GW combination" and information exchange between AD's to be
provided.
4.3. Back Office Functions - Billing and Logging Guidelines
Back Office refers to the following:
o Servers and Content Management systems that support the delivery
of applications via multicast and interactions between ADs.
o Functionality associated with logging, reporting, ordering,
provisioning, maintenance, service assurance, settlement, etc.
4.3.1 Provisioning Guidelines
Resources for basic connectivity between ADs Providers need to be
provisioned as follows:
o Sufficient capacity must be provisioned to support multicast-based
delivery across ADs.
o Sufficient capacity must be provisioned for connectivity between
all supporting back-offices of the ADs as appropriate. This
includes activating proper security treatment for these back-
office connections (gateways, firewalls, etc) as appropriate.
o Routing protocols as needed, e.g. configuring routers to support
these.
Provisioning aspects related to Multicast-Based inter-domain
delivery are as follows.
The ability to receive requested application via multicast is
triggered via the manifest file. Hence, this file must be provided
to the EU regarding multicast URL - and unicast fallback if
applicable. AD-2 must build manifest and provision capability to
provide the file to the EU.
Native multicast functionality is assumed to be available in across
many ISP backbones, peering and access networks. If however, native
multicast is not an option (Use Cases 3.4 and 3.5), then:
o 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).
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o 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).
o 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.
o DNS across each AD must be provisioned to enable a client GW to
locate the optimal AMT Relay (i.e. longest multicast path and
shortest unicast tunnel) with connectivity to the content's
multicast source.
Provisioning Aspects Related to Operations and Customer Care are
stated as follows.
Each AD provider is assumed to provision operations and customer
care access to their own systems.
AD-1's operations and customer care functions must have visibility
to what is happening in AD-2's network or to the service provided by
AD-2, sufficient to verify their mutual goals and operations, e.g.
to know how the EU's are being served. This can be done in two ways:
o Automated interfaces are built between AD-1 and AD-2 such that
operations and customer care continue using their own systems.
This requires coordination between the two AD's with appropriate
provisioning of necessary resources.
o AD-1's operations and customer care personnel are provided access
directly to AD-2's system. In this scenario, additional
provisioning in these systems will be needed to provide necessary
access. Additional provisioning must be agreed to by the two AD-2s
to support this option.
4.3.2 Application Accounting Billing Guidelines
All interactions between pairs of ADs can be discovered and/or be
associated with the account(s) utilized for delivered applications.
Supporting guidelines are as follows:
o A unique identifier is recommended to designate each master
account.
o AD-2 is expected to set up "accounts" (logical facility generally
protected by login/password/credentials) for use by AD-1. Multiple
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accounts and multiple types/partitions of accounts can apply, e.g.
customer accounts, security accounts, etc.
4.3.3 Log Management Guidelines
Successful delivery of applications via multicast between pairs of
interconnecting ADs requires that appropriate logs will be exchanged
between them in support. Associated guidelines are as follows.
AD-2 needs to supply logs to AD-1 per existing contract(s). Examples
of log types include the following:
o Usage information logs at aggregate level.
o Usage failure instances at an aggregate level.
o Grouped or sequenced application access
performance/behavior/failure at an aggregate level to support
potential Application Provider-driven strategies. Examples of
aggregate levels include grouped video clips, web pages, and sets
of software download.
o Security logs, aggregated or summarized according to agreement
(with additional detail potentially provided during security
events, by agreement).
o Access logs (EU), when needed for troubleshooting.
o Application logs (what is the application doing), when needed for
shared troubleshooting.
o Syslogs (network management), when needed for shared
troubleshooting.
The two ADs may supply additional security logs to each other as
agreed to by contract(s). Examples include the following:
o Information related to general security-relevant activity which
may be of use from a protective or response perspective, such as
types and counts of attacks detected, related source information,
related target information, etc.
o Aggregated or summarized logs according to agreement (with
additional detail potentially provided during security events, by
agreement)
4.3.4 Settlement Guidelines
Settlements between the ADs relate to (1) billing and reimbursement
aspects for delivery of applications, and (2) aggregation,
transport, and collection of data in preparation for the billing and
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reimbursement aspects for delivery of applications for the
Application Provider. At a high level:
o AD-2 collects "usage" data for AD-1 related to application
delivery to End Users, and submits invoices to AD-1 based on this
usage data. The data may include information related to the type
of content delivered, total bandwidth utilized, storage utilized,
features supported, etc.
o AD-1 collects all available data from partner AD-2 and creates
aggregate reports pertaining to responsible Application Providers,
and submits subsequent reports to these Providers for
reimbursements.
o AD-1 may convey charging values or charging rules to the AD-2,
proactively or in response to a query, especially in cases where
these may change.
o AD-2 may convey prices/rates to AD-1, proactively or in response
to a query, especially in cases where these may change.
o Usage data may be collected per end user or on an aggregated
basis; the method of collection will depend on the application
delivered and/or the agreements with the source provider. In all
cases, usage volume is expected to be in terms of delivered packet
bits or bytes.
4.4. Operations - Service Performance and Monitoring Guidelines
Service Performance refers to monitoring metrics related to
multicast delivery via probes. The focus is on the service provided
by AD-2 to AD-1 on behalf of all multicast application sources
(metrics may be specified for SLA use or otherwise). Associated
guidelines are as follows:
o Both AD's are expected to monitor, collect, and analyze service
performance metrics for multicast applications. AD-2 provides
relevant performance information to AD-1; this enables AD-1 to
create an end-to-end performance view on behalf of the
multicast application source.
o Both AD's are expected to agree on the type of probes to be
used to monitor multicast delivery performance. For example,
AD-2 may permit AD-1's probes to be utilized in the AD-2
multicast service footprint. Alternately, AD-2 may deploy its
own probes and relay performance information back to AD-1.
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o In the event of performance degradation (SLA violation), AD-1
may have to compensate the multicast application source per SLA
agreement. As appropriate, AD-1 may seek compensation from AD-2
if the cause of the degradation is in AD-2's network.
Service Monitoring generally refers to a service (as a whole)
provided on behalf of a particular multicast application source
provider. It thus involves complaints from End Users when service
problems occur. EU's direct their complaints to the source provider;
in turn the source provider submits these complaints to AD-1. The
responsibility for service delivery lies with AD-1; as such AD-1
will need to determine where the service problem is occurring - its
own network or in AD-2. It is expected that each AD will have tools
to monitor multicast service status in its own network.
o Both AD's will determine how best to deploy multicast service
monitoring tools. Typically, each AD will deploy its own set of
monitoring tools; in which case, both AD's are expected to
inform each other when multicast delivery problems are
detected.
o AD-2 may experience some problems in its network. For example,
for the AMT Use Cases, one or more AMT Relays may be
experiencing difficulties. AD-2 may be able to fix the problem
by rerouting the multicast streams via alternate AMT Relays. If
the fix is not successful and multicast service delivery
degrades, then AD-2 needs to report the issue to AD-1.
o When problem notification is received from a multicast
application source, AD-1 determines whether the cause of the
problem is within its own network or within the AD-2 domain. If
the cause is within the AD-2 domain, then AD-1 supplies all
necessary information to AD-2. Examples of supporting
information include the following:
o Kind of problem(s)
o Starting point & duration of problem(s).
o Conditions in which problem(s) occur.
o IP address blocks of affected users.
o ISPs of affected users.
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o Type of access e.g., mobile versus desktop.
o Locations of affected EUs.
o Both AD's conduct some form of root cause analysis for
multicast service delivery problems. Examples of various
factors for consideration include:
o Verification that the service configuration matches the
product features.
o Correlation and consolidation of the various customer
problems and resource troubles into a single root service
problem.
o Prioritization of currently open service problems, giving
consideration to problem impact, service level agreement,
etc.
o Conduction of service tests, including one time tests or a
series of tests over a period of time.
o Analysis of test results.
o Analysis of relevant network fault or performance data.
o Analysis of the problem information provided by the customer
(CP).
o Once the cause of the problem has been determined and the
problem has been fixed, both AD's need to work jointly to
verify and validate the success of the fix.
o Faults in service could lead to SLA violation for which the
multicast application source provider may have to be
compensated by AD-1. Subsequently, AD-1 may have to be
compensated by AD-2 based on the contract.
4.5. Client Reliability Models/Service Assurance Guidelines
There are multiple options for instituting reliability
architectures, most are at the application level. Both AD's should
work those out with their contract/agreement and with the multicast
application source providers.
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Network reliability can also be enhanced by the two AD's by
provisioning alternate delivery mechanisms via unicast means.
5. Security Considerations
DRM and Application Accounting, Authorization and Authentication
should be the responsibility of the multicast application source
provider and/or AD-1. AD-1 needs to work out the appropriate
agreements with the source provider.
Network has no DRM responsibilities, but might have authentication
and authorization obligations. These though are consistent with
normal operations of a CDN to insure end user reliability, security
and network security
AD-1 and AD-2 should have mechanisms in place to ensure proper
accounting for the volume of bytes delivered through the peering
point and separately the number of bytes delivered to EUs.
If there are problems related to failure of token authentication
when end-users are supported by AD-2, then some means of validating
proper working of the token authentication process (e.g., back-end
servers querying the multicast application source provider's token
authentication server are communicating properly) should be
considered. Details will have to be worked out during implementation
(e.g., test tokens or trace token exchange process).
6. IANA Considerations
7. Conclusions
This Best Current Practice document provides detailed Use Case
scenarios for the transmission of applications via multicast across
peering points between two Administrative Domains. A detailed set of
guidelines supporting the delivery is provided for all Use Cases.
For Use Cases involving AMT tunnels (cases 3.4 and 3.5), 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. Section 4.3 provides an overview of one method that
finds the optimal Relay-Gateway combination via the use of an
Anycast IP address for AMT Relays.
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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
[INF_ATIS_10] "CDN Interconnection Use Cases and Requirements in a
Multi-Party Federation Environment", ATIS Standard A-0200010,
December 2012
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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