Network Working Group R.R. Chodorek
Internet Draft AGH Univ. of Science and Technology
Intended status: Standards Track February 7, 2017
Expires: August 7, 2017
Multiple multicast addressing architecture
draft-chodorek-6man-multigroup-multicast-addr-04
Abstract
This document introduces a new class of IPv6 multicast addresses
called "multiple multicast". We define multiple multicast as a set
of multicast addresses belonging to one multicast session.
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Table of Contents
1. Introduction ................................................ 2
2. Conventions used in this document ........................... 2
3. Multiple multicast addressing ............................... 3
4. Usage of multiple multicast addressing ...................... 3
4.1. Multimedia layered multicast ........................... 4
4.2. Multimedia conference systems .......................... 4
4.3. Multiple content from the one sender ................... 4
4.4. Routers ................................................ 4
5. Security Considerations ..................................... 4
6. IANA Considerations ......................................... 5
7. References .................................................. 5
7.1. Normative References ................................... 5
7.2. Informative References ................................. 5
1. Introduction
Multimedia services can use multiple multicast streams [ITU2009]
which form one multicast session. These services have been provided
using several multicast groups or one multicast group and user level
filtering. For services which have been provided using several
multicast groups this document introduces the new class of IPv6
multicast addresses called "multiple multicast". We define a
multiple multicast as a set of multicast addresses belonging to one
multicast session. Multicast addresses which belong to the one
multiple multicast address follow the same multicast tree. It allows
for identical propagation parameters for each transmitted stream
belonging to one multicast session. It also simplifies multicast
routing and the management of multiple multicast streams.
The new class of IPv6 multicast addresses expands the current IPv6
multicast addressing architecture [RFC4291].
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
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3. Multiple multicast addressing
The new class of IPv6 multicast addresses expands the unicast-
prefix-based IPv6 multicast address [RFC7371][RFC3306].
The group ID is divided into two fields (Figure 1). The first one is
session ID (20 bits). The second one is stream ID (12 bits).
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 20 | 12 |
+--------+----+----+----+----+------+---------+---------+--------+
|11111111|ff1 |scop|ff2 |rsvd| plen | network | session | stream |
| | | | | | | prefix | ID | ID |
+--------+----+----+----+----+------+---------+---------+--------+
Figure 1 New class of IPv6 multicast address
+-+-+-+-+
ff2 (flag field 2) is a set of 4 flags: |r|r|G|r|
+-+-+-+-+
where:
o "r" bits is for future assignment and MUST each be set to 0,
o G = 1 indicates a multigroup multicast address.
The new class of IPv6 addresses will be indicated by bit G in the
ff2 (flag field 2). If a new multicast session is created a new
session ID is generated. If within the specified session a new
stream is required then a new stream ID is generated.
A value of 0 is reserved for the field session ID. There is also a
value of 0 reserved for the field stream ID.
4. Usage of multiple multicast addressing
There are two main benefits to using multiple multicast addressing:
multimedia layered multicast (hierarchical coding) and multimedia
conference systems [ITU2009]. It is also possible to use the
proposed addressing scheme in large multicast multimedia streaming
services. This addressing scheme simplifies multicast routing and
the management of multiple multicast streams.
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4.1. Multimedia layered multicast
A multimedia layered multicast hierarchically encodes multimedia
content into complementary layers and these are transmitted through
the network as separate multicast groups. Using the new addressing
scheme if a sender wants to send a layered multicast to recipients
they must first allocate a new session ID for all streams (layers).
Each layer is allocated a new stream ID. In a typical allocation
scheme for layered transmission the base layer will have the stream
ID set to a value of 1.
4.2. Multimedia conference systems
For the multimedia content of a conference two (audio, video) or
more (audio, video and additional data) multicast streams will be
created. Each of the conference participants will have one session
ID created and for each stream a stream ID is allocated. Typically:
base audio stream ID = 1, video stream ID = 2 and additional data
will have stream IDs with higher numbers.
4.3. Multiple content from the one sender
One IPTV service platform operator can sends multiple TV streams
(e.g. different TV channels or two or more channels that offer the
same content but in different resolutions and/or formats). In IPTV
SSM multicast is desired. According to [RFC 3306] the SSM address
sets plen = 0 and sets network prefix = 0. In the proposed
addressing scheme for all transmitted content the service provider
allocates the session ID. For each TV stream the service provider
allocates one or more stream IDs.
4.4. Routers
Routers must recognize multiple multicast addressing. For each
session ID the router builds one common delivery tree (common
multicast delivery tree is essential to provide multicast-based
congestion avoidance [Cho2004]). If a user wants to receive a new
stream with a selected stream ID the router must enable forwarding
for it. If a user does not need a specified stream the router must
disable the stream for the specified stream ID.
5. Security Considerations
The same security considerations as those discussed in [RFC3306] are
to be taken into account.
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6. IANA Considerations
This document does not require any action from IANA.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC7371] Boucadair, M., and Venaas, S., "Updates to the IPv6
Multicast Addressing Architecture", RFC 7371, September
2014.
7.2. Informative References
[ITU2009] ITU-T, "Multicast functions in next generation networks",
ITU-T Recommendation Y.2017, 2009.
[Cho2004] Chodorek, A., and Chodorek, R.R., "Multigroup
Communication Using Active Networks Technology", 3rd
International Conference on Network Control and
Engineering for QoS, Security and Mobility (Net-Con 2004),
pp. 315-326, 2004.
Authors' Addresses
Robert R. Chodorek
AGH Univ. of Science and Technology
Al. Mickiewicza 30
30-059 Krakow
Poland
Email: chodorek@agh.edu.pl
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