[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Nits]

Versions: 00 01 02 03 04 05 06 draft-irtf-samrg-common-api

Network Working Group                                       M. Waehlisch
Internet-Draft                                      link-lab & FU Berlin
Intended status: Informational                               TC. Schmidt
Expires: April 22, 2010                                      HAW Hamburg
                                                        October 19, 2009


             A Common API for Transparent Hybrid Multicast
                   draft-waehlisch-sam-common-api-00

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on April 22, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   Group communication services are most efficiently implemented on the
   lowest layer available.  This document describes a common multicast



Waehlisch & Schmidt      Expires April 22, 2010                 [Page 1]

Internet-Draft              Common Mcast API                October 2009


   API that serves the requirements of data distribution and maintenance
   for multicast and broadcast on a middleware abstraction layer,
   suitable for transparent underlay and overlay communication.
   Additionally, it describes the application of this API in current
   Internet multicast routing protocols.

Requirements Language

   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].


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Hybrid Multicast API  . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Abstract Data Types . . . . . . . . . . . . . . . . . . . . 4
     4.2.  Send/Receive Calls  . . . . . . . . . . . . . . . . . . . . 4
     4.3.  Service Calls . . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Deployment Use Cases  . . . . . . . . . . . . . . . . . . . . . 5
     5.1.  DVMRP . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     5.2.  PIM-SM  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     5.3.  PIM-SSM . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     5.4.  BIDIR-PIM . . . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

















Waehlisch & Schmidt      Expires April 22, 2010                 [Page 2]

Internet-Draft              Common Mcast API                October 2009


1.  Introduction

   Group communication is implemented on different layers.  To allow for
   a comprehensive development of applications and group services a
   common API is required, which provides calls to transmit and receive
   multicast data as well as a consistent view on multicast states.
   This document describes an abstract group communication API.  A
   specific implementation description with respect to operating systems
   or programming languages is out-of-scope of this document.

   The aim of this API is twofold: An application programmer should be
   able to implement group-oriented data distribution independent of the
   underlying delivery mechanisms (e.g. native IP multicast or
   application layer multicast).  Receivers require an interface to
   subscribe and leave a multicast group.  Multicast sources send data
   to a group address.  This group address relies on a specific
   namespace.  The API should reflect the flexiblity in choosing an
   appropriate namespace.

   Additionally, the multicast API should provide internal interfaces to
   request current multicast states at the host.  Multiple multicast
   protocols may run in parallel on a single host.  These protocols may
   interact together.


2.  Terminology

   Inter-domain Multicast Gateway:  An Inter-domain Multicast Gateway
      (IMG) transparently forwards data between IP layer and overlay
      multicast.


3.  Overview

   The API consists of up and down calls.  The down calls can be
   implemented in a middleware that delegates those to overlay or
   underlay:














Waehlisch & Schmidt      Expires April 22, 2010                 [Page 3]

Internet-Draft              Common Mcast API                October 2009


   *-------*     *-------*
   | App 1 |     | App 2 |
   *-------*     *-------*
       |             |
   *---------------------*
   |   Middleware        |
   *---------------------*
        |          |
   *---------*     |
   | Overlay |     |
   *---------*     |
        |          |
        |          |
   *---------------------*
   |   Underlay          |
   *---------------------*


4.  Hybrid Multicast API

4.1.  Abstract Data Types

   Namespace  describes the domain-specific context in which the
      applications operate.

   Address  is any kind of address in underlay (e.g.  IPv4, IPv6) or
      overlay (e.g.  SIP, hash-based ID).

   Mode  denotes the layer on which the corresponding call will be
      effective.  This may be unspecified to leave the decicision at the
      group communication stack.

4.2.  Send/Receive Calls

   init(in Namespace n)  This call is implemented

   join(in Address a, in Mode m)  This operation initiates a group
      subscription.  Depending on the mode, this may result in an IGMP/
      MLD report.

   leave(in Address a, in Mode m)  This operation results in an
      unsubscription for the given address.

   send(in Address a, in Mode m, out Message msg)







Waehlisch & Schmidt      Expires April 22, 2010                 [Page 4]

Internet-Draft              Common Mcast API                October 2009


   receive(in Address a, in Mode m, out Message msg)

4.3.  Service Calls

   groupSet(out Address[] g, in Mode m)  This operation returns all
      registered multicast groups.  The information can be provided by
      group management or routing protocols.  The return values
      distinguish between sender and listener states.

   neighborSet(out Address[] a, in Mode m)  This function can be invoked
      to get the set of multicast routing neighbors.

   designatedHost(out Bool b, in Address a)  This function returns true,
      if the host has the role of a designated forwarder or querier.
      Such an information is provided by almost all multicast protocols
      to handle packet duplication, if multiple multicast instances
      serve on the same subnet.

   updateListener(out Address g, in Mode m)  This upcall is invoked to
      inform a group service about a change of listener states for a
      group.  This is the result of receiver new subscriptions or
      leaves.  The group service may call groupSet to get updated
      information.

   updateSender(out Address g, in Mode m)  This upcall should be
      implemented to inform the application about source state changes.
      Analog to the updateListener case, the group service may call
      thereupon groupSet.


5.  Deployment Use Cases

   This section describes the application of the defined API to
   implement an IMG.

5.1.  DVMRP

   An arbitrary DVMRP [RFC1075] router will not be informed about new
   receivers, but will learn about new sources immediately.  The concept
   of DVMRP does not provide any central multicast instance.  Thus, the
   IMG can be placed anywhere inside the multicast region, but requires
   a DVMRP neighbor connectivity.  The group communication stack used by
   the IMG is enhanced by a DVMRP implementation.  New sources in the
   underlay will be advertised based on the DVMRP flooding mechanism and
   received by the IMG.  Based on this the updateSender() call is
   triggered.  The relay agent initiates a corresponding join in the
   native network and forwards the received source data towards the
   overlay routing protocol.  Depending on the group states, the data



Waehlisch & Schmidt      Expires April 22, 2010                 [Page 5]

Internet-Draft              Common Mcast API                October 2009


   will be distributed to overlay peers.

   DVMRP establishes source specific multicast trees.  Therefore, a
   graft message is only visible for DVMRP routers on the path from the
   new receiver subnet to the source, but in general not for an IMG.  To
   overcome this problem, data of multicast senders will be flooded in
   the overlay as well as in the underlay.  Hence, an IMG has to
   initiate an all-group join to the overlay using the namespace
   extension of the API.  Each IMG is initially required to forward the
   received overlay data to the underlay, independent of native
   multicast receivers.  Subsequent prunes may limit unwanted data
   distribution thereafter.

5.2.  PIM-SM

   The Protocol Independent Multicast Sparse Mode (PIM-SM) [RFC4601]
   establishes rendezvous points (RP).  These entities receive listener
   and source subscriptions of a domain.  To be continuously updated, an
   IMG has to be co-located with a RP.  Whenever PIM register messages
   are received, the IMG must signal internally a new multicast source
   using updateSender().  Subsequently, the IMG joins the group and a
   shared tree between the RP and the sources will be established, which
   may change to a source specific tree after a sufficient number of
   data has been delivered.  Source traffic will be forwarded to the RP
   based on the IMG join, even if there are no further receivers in the
   native multicast domain.  Designated routers of a PIM-domain send
   receiver subscriptions towards the PIM-SM RP.  The reception of such
   messages invokes the updateListener() call at the IMG, which
   initiates a join towards the overlay routing protocol.  Overlay
   multicast data arriving at the IMG will then transparently be
   forwarded in the underlay network and distributed through the RP
   instance.

5.3.  PIM-SSM

   PIM Source Specific Multicast (PIM-SSM) is defined as part of PIM-SM
   and admits source specific joins (S,G) according to the source
   specific host group model [RFC4604].  A multicast distribution tree
   can be established without the assistance of a rendezvous point.

   Sources are not advertised within a PIM-SSM domain.  Consequently, an
   IMG cannot anticipate the local join inside a sender domain and
   deliver a priori the multicast data to the overlay instance.  If an
   IMG of a receiver domain initiates a group subscription via the
   overlay routing protocol, relaying multicast data fails, as data are
   not available at the overlay instance.  The IMG instance of the
   receiver domain, thus, has to locate the IMG instance of the source
   domain to trigger the corresponding join.  In the sense of PIM-SSM,



Waehlisch & Schmidt      Expires April 22, 2010                 [Page 6]

Internet-Draft              Common Mcast API                October 2009


   the signaling should not be flooded in underlay and overlay.

   One solution could be to intercept the subscription at both, source
   and receiver sites: To monitor multicast receiver subscriptions
   (updateListener()) in the underlay, the IMG is placed on path towards
   the source, e.g., at a domain border router.  This router intercepts
   join messages and extracts the unicast source address S, initializing
   an IMG specific join to S via regular unicast.  Multicast data
   arriving at the IMG of the sender domain can be distributed via the
   overlay.  Discovering the IMG of a multicast sender domain may be
   implemented analogously to AMT [I-D.ietf-mboned-auto-multicast] by
   anycast.  Consequently, the source address S of the group (S,G)
   should be built based on an anycast prefix.  The corresponding IMG
   anycast address for a source domain is then derived from the prefix
   of S.

5.4.  BIDIR-PIM

   Bidirectional PIM [RFC5015] is a variant of PIM-SM.  In contrast to
   PIM-SM, the protocol pre-establishes bidirectional shared trees per
   group, connecting multicast sources and receivers.  The rendezvous
   points are virtualized in BIDIR-PIM as an address to identify on-tree
   directions (up and down).  However, routers with the best link
   towards the (virtualized) rendezvous point address are selected as
   designated forwarders for a link-local domain and represent the
   actual distribution tree.  The IMG is to be placed at the RP-link,
   where the rendezvous point address is located.  As source data in
   either cases will be transmitted to the rendezvous point address, the
   BIDIR-PIM instance of the IMG receives the data and can internally
   signal new senders towards the stack via updateSender().  The first
   receiver subscription for a new group within a BIDIR-PIM domain needs
   to be transmitted to the RP to establish the first branching point.
   Using the updateListener() invocation, an IMG will thereby be
   informed about group requests from its domain, which are then
   delegated to the overlay.


6.  IANA Considerations

   This document makes no request of IANA.


7.  Security Considerations

   This draft does neither introduce additional messages nor novel
   protocol operations.  TODO





Waehlisch & Schmidt      Expires April 22, 2010                 [Page 7]

Internet-Draft              Common Mcast API                October 2009


8.  Acknowledgements

   TODO


9.  References

9.1.  Normative References

   [RFC1075]  Waitzman, D., Partridge, C., and S. Deering, "Distance
              Vector Multicast Routing Protocol", RFC 1075,
              November 1988.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              October 1999.

   [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, October 2002.

   [RFC3810]  Vida, R. and L. Costa, "Multicast Listener Discovery
              Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC4601]  Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

   [RFC4604]  Holbrook, H., Cain, B., and B. Haberman, "Using Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Protocol Version 2 (MLDv2) for Source-
              Specific Multicast", RFC 4604, August 2006.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, October 2007.

9.2.  Informative References

   [I-D.ietf-mboned-auto-multicast]
              Thaler, D., Talwar, M., Aggarwal, A., Vicisano, L., and T.
              Pusateri, "Automatic IP Multicast Without Explicit Tunnels
              (AMT)", draft-ietf-mboned-auto-multicast-09 (work in
              progress), June 2008.




Waehlisch & Schmidt      Expires April 22, 2010                 [Page 8]

Internet-Draft              Common Mcast API                October 2009


Authors' Addresses

   Matthias Waehlisch
   link-lab & FU Berlin
   Hoenower Str. 35
   Berlin  10318
   Germany

   Email: mw@link-lab.net
   URI:   http://www.inf.fu-berlin.de/~waehl


   Thomas C. Schmidt
   HAW Hamburg
   Berliner Tor 7
   Hamburg  20099
   Germany

   Email: schmidt@informatik.haw-hamburg.de
   URI:   http://inet.cpt.haw-hamburg.de/members/schmidt































Waehlisch & Schmidt      Expires April 22, 2010                 [Page 9]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/