Internet Engineering Task Force C.Y. Lee
INTERNET DRAFT Nortel
24 March 1998
PIM-SM over ATM and Proxy PAR
<draft-leecy-pimsm-atm-00.txt>
Status of This Memo
This document is an Internet Draft, Internet Drafts are working
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Abstract
This document describes how PIM-SM [PIM-SM, PIM] operates in ATM
networks in the presence of Proxy PAR. [PPAR, OSPF_PPAR]. The
mechanisms described allow for simpler, more efficient and
cost-effective network designs.
2. Scope
2.1 Scoping PIM-SM over Proxy PAR
PIM-SM over Proxy PAR [PPAR] is scoped to prevent information
from being flooded unnecessarily throughout the ATM network.
In this document, the PAR advertisement for PIM-SM would be
limited to PIM-SM scope only (level 60 only as shown in Figure 1).
These advertisements may be propagated to the BGMP scope (level 40
in Figure 1) but the purpose and mechanism is beyond the scope of
this document.
+-+
| | PNNI peer group # PPAR capable @ PNNI capable * Router
+-+ switch switch
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Level 40 - BGMP
+---------------------------+
| |
| |
| @ ---- @ ---- @ |
| | | |
+----- | ----------- | -----+
| |
Level 60 - PIM-SM | | Level 60 - PIM-SM
+------------- | ---+ +-- | --------------+
| | | | | |
R1* ------#-P1------@ | | @---------P3-#------- * R3
| | | | | |
R2* ------#-P2------+ | | +---------P4-#------- * R4
| | | |
+-------------------+ +-------------------+
Figure 1: Scoping PIM-SM and BGMP over Proxy PAR (ATM Topology)
(Modified for IP multicasting from [PPAR])
2.2 Model
This document describes 2 different models for PIM-SM over ATM.
The first, Model A is the same model described in [INTRALIS]. The
document [INTRALIS] requires that "each router within a LIS knows IP
and ATM addresses of all other routers within the LIS" but the
mechanism to obtain this information is not specified. Section A of
this document describes how Proxy PAR can be used by PIM-SM routers
to auto discover their peers in a LIS (Logical IP Subnet) [IPOA].
The second Model B (FFS now), described in Section B is based on
[INTRALIS], with the following differences:
- this section describes multicasting over ATM within a PIM-SM
routing domain
- the mechanisms proposed in this section do not require a priori fully
meshed distribution (point-to-multipoint) VC to exist among the routers
in a LIS.
- LIJ (Leaf Initiated Join) [AF-UNI] is used to setup point to
multipoint VCs.
3. Section A
3.1 Auto Configuring PIM-SM routers
Each PIM-SM router in a LIS is configured with its own IP address,
mask, and router priority. This configuration information is
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bound to a local ATM end point address and registered by the router
(Proxy PAR client) to the Proxy Server. Proxy PAR server detection
is described in [ILMIDET]. The Proxy PAR server then flood the
registered router information. A router may query the server to get
information about other routers in the ATM cloud. Once the
configuration information about each PIM-SM router in the LIS is learned
via Proxy PAR, the shared distribution VCs described in
[INTRALIS] may be setup.
In PIM-SM a DR router is elected on a multi-access network using
the Hello mechanism, the router with the largest network address
assumes the role of DR. (With Hello extensions [HELLO_EXT], the Router
with the highest priority will be elected).
When PIM-SM is run over Proxy PAR the exchange of these Hellos to
elect a DR may be replaced by Proxy PAR advertisements.
3.2 Service Definition of PIM-SM routers
Each router register configuration information for each
NSAP (ATM address) in the UNI Service IG. Within each UNI Service IG,
a router register its routing protocol service, PIM-SM in this case,
in the UNI IPv4 Service Definition IG and the PIM-SM specific
configuration parameters in the UNI PIM-SM IPv4 Service Definition IG
as shown in the figures below.
This IG is then registered with the Proxy PAR server at the appropriate
scope. If any of the parameters in the IG is changed, the client must
reregister the new parameters with the Proxy PAR server.
A - UNI Service IG
B - UNI IPv4 Service Definition IG
C - UNI PIM-SM IPv4 Service Definition IG
<---------------------------- A -------------------------------->
<------- B ---------> .... <----- B ------->
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | C | ..... | C | .... | C | .... | C | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: PNNI IG (Information Groups) used by PIM-SM over Proxy PAR
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=784 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP instance | Padding |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Service Mask |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: UNI IPv4 Service Definition IG
(Note: The UNI IPv4 Service Definition IG is reproduced here from [AF-PPAR]
to illustrate its use)
Type IG Type
IP Instance The IP instance PIM-SM is registered for
IP Address The IP address or IP address prefix PIM-SM is
registered for
IP Address Mask Contiguous mask fo the IP address/prefix.
Service Mask Bitmask of registered services, Bit 11 = PIM-SM
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=804 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: UNI PIM-SM Service Definition IG
Type 804
Length Length of IG
Priority Used for DR election
4. Section B
Editor's Note:
This section is FFS.
If the RP for the group in the multicast routing domain can
be determined by querying the DNS as proposed in [STATIC_MCAST],
Proxy PAR may be used to discover the DNS server in the ATM network.
The only requirement is that a least one DNS server must be located
within or attached to the ATM network.
Using DNS to locate the RP reduces the amount of routing control
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information (BSR and C-RP advertisements) that must be flooded
in the WAN and reduces the number of VCs required among routers.
If a VC to the upstream router does not yet exist :
A PIM-SM Join to an upstream router is preceeded by a LIJ to
the upstream router :
1) if using a group shared point to multipoint VC, (224.0.0.1) is
specified as the connection idenfifier in the LEAF SETUP MESSAGE.
2) if requiring a dedicated group specific point to multipoint VC
[INTRALIS], Group specific Joins can be communicated to the upstream
router using ATM LIJ, Leaf Initiated Join (specifying the IP
multicast address as the LIJ connection identifier to the upstream
router which is the root of the pt-mpt VC.
In both cases, the ATM address of the upstream router may be obtained
from Proxy PAR and must be specified in the LEAF SETUP MESSAGE.
Note that LIJ to (224.0.0.1) is only setup if the LIJ VC does not
exist.
The upstream router will then establish a LIJ to the
(224.0.0.1) to the downstream router. This will allow the PIM-SM Join
to be sent to the upstream router. The need to establish a VC to the
downstream router is either implicit in the connection identifier
and/or additonal signalling information may be defined (eg B-LLI).
The above procedures do not require a priori fully meshed distribution
(point-to-multipoint) VC to exist among the routers in a LIS.
The rules concerning eg. "Switching to a Source-Rooted Tree,
Adding New Members to a Source-Rooted Tree, Handling the Packet
Relection Problem" specified in [INTRALIS] still apply here.
VC management relating to VC establishment and tear-down, VC sharing.
will be discussed in more detail in the next version of the draft.
5. Acknowledgments
Comments and contributions from Tony Przygienda and Patrick Droz
are included in this work. Tony Przygienda suggested the use of LIJ
to setup point to multipoint VC. The use of Join to setup VC was
first proposed in [INTRALIS]. Thanks to Ahmed Helmy and Dave Thaler
for clarifying the details of PIM-SM.
6. Security Consideration
Security issues are not discussed in this memo.
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References
[AF-PPAR] T. Przygienda and P. Droz. Proxy PAR Specification.
ATM Forum 97-0495, 97-0705, 97-0882, July 1997.
[PPAR] T. Przygienda and P. Droz.
Proxy PAR, Internet Draft, November 1997
[OSPF_PPAR] T. Przygienda and P. Droz.
OSPF over ATM and Proxy PAR, Internet Draft, October 1997
[AF-ILMI] ATM-Forum. Interim Local Management Interface (ILMI)
Specification 4.0. ATM Forum 95-0417R8, June 1996.
[AF-PNNIV1] ATM-Forum. Private Network-Network Interface Specification
Version 1.0. ATM Forum af-pnni-0055.000, March 1996.
[AF-UNI] ATM-Forum. Private Network-Network Interface Specification
Version 4.0. ATM Forum af-sig-0061.000, July 1996.
[AF-PNNIV2] ATM-Forum. Private Network-Network Interface Specification
Version 2.0. ATM Forum LTD-PNNI-02.00 December 1997.
[PIMSM] Estrin, Farinacci, Helmy, Thaler, Deering, Handley,
Jacobson, Liu, Sharma, and Wei.
Protocol independent multicast-sparse mode (PIM- SM):
Specification. Internet Draft, September 1996.
[INTRALIS] D. Farinaccci, D. Meyer, Y. Rekhter
Intra-LIS IP multicast among routers over ATM using
Sparse Mode, Internet Draft, 1997
[STATIC_MCAST] M. Ohta, J. Crowcroft Static Multicast,
Internet Draft, March 1998
[PAR] R. Callon and al. An Overview of PNNI Augmented Routing.
ATM Forum 96-0354, April 1996.
[OPAQUE] R. Coltun and J. Heinanen. Opaque LSA in OSPF.
Internet Draft, 1997.
[AF-MIPAR] R. Coltun, T. Przygienda, and S. Shew.
MIPAR: Minimal PNNI Augmented Routing.
ATM Forum 96-0838, June 1996.
[ILMI] M. Davison. Simple ILMI-Based Server Discovery.
Internet Draft, 1997.
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[IPOA] M. Laubach. Classical IP and ARP over ATM,
RFC 1577. January 1994.
[SIG_IPOA] ATM Signalling Support for IP over ATM,
RFC 1755, February 1995.
[OSPF94] J. Moy. OSPFv2, RFC 1583. March 1994.
[DEMAND] J. Moy. Extending OSPF to Support Demand Circuits,
RFC 1793. April 1995.
[OSPF98] J. Moy. OSPFv2, RFC 2178. July 1997.
[MARS] G. Armitage. Support for Multicast over UNI 3.0/3.1
based ATM Networks, RFC 2022. November 1996.
Authors' Addresses
Cheng-Yin Lee
Nortel
PO Box 3511, Station C
Ottawa, ON K1Y 4H7
Canada
leecy@nortel.ca
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