A Distributed MARS Service Using SCSP
Network Working Group J. Luciani
Request for Comments: 2443 Bay Networks
Category: Experimental A. Gallo
A Distributed MARS Service Using SCSP
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document describes a method for distributing a MARS service
within a LIS. This method uses the Server Cache Synchronization
Protocol (SCSP) to synchronize the MARS Server databases within a
LIS. When SCSP is used to synchronize the caches of MARS Servers in
a LIS, the LIS defines the boundary of an SCSP Server Group (SG).
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in .
The MARS is an extended analog of the ATMARP Server introduced in
. It provides the necessary connection and addressing services
required by layer 3 multicast services over ATM. There are three
basic elements to the MARS model. First, the MARS Server which
manages and distributes layer 3 group membership information to the
LIS. Second, MARS Clients which register with and query a single MARS
Server for layer 3 multicast information. Third, MCS Clients which
register with a single MARS Server and provide layer 3 multicast
forwarding services for a LIS.
Both MARS Clients and MCS Clients explicitly register with the MARS
Server before exchanging layer 3 multicast information. During the
registration process MARS Clients are place on the Cluster Control VC
Luciani & Gallo Experimental [Page 1]
RFC 2443 MARS Service Using SCSP November 1998
(CCVC) and MCS Clients are placed on the Server Control VC (SCVC).
Both the CCVC and SCVC are then used to propagate layer 3 multicast
updates to the clients which make up a LIS. During the registration
process MARS Clients are also assigned a unique Cluster Member ID
(CMI) which is used to identify reflected packets in the presence of
In the Distributed MARS Model there MAY be multiple MARS Servers in a
given LIS, and since any MARS Server within the LIS MUST be able to
provide layer 3 multicast information about any multicast group
within the LIS, there MUST be a method by which to synchronize
multicast information across all MARS Servers within the LIS.
The Server Cache Synchronization Protocol (SCSP) solves the
generalized server synchronization/cache-replication problem for
distributed databases, and thus SCSP MAY be applied to the MARS
Server database synchronization problem within a LIS. When SCSP is
used to synchronize the caches of MARS Servers in a LIS, the LIS
defines the boundary of and SCSP Server Group (SG).
SCSP is defined in two parts: the protocol independent part and the
client/server protocol specific part. The protocol independent part
is specified in  whereas this document will specify the
client/server protocol specific part where the MARS Server is the
All MARS Servers belonging to a LIS are said to belong to a Server
Group (SG). A SG is identified by, not surprisingly, its SGID which
is contained in a field in all SCSP packets. All SCSP packets contain
a Protocol ID (PID) field as well. This PID field is set to 0x0003 to
signify that SCSP is synchronizing MARS Server databases as opposed
to synchronizing some other protocol's databases. (see Section
B.2.0.1 of  for more details). In general, PIDs for SCSP will be
assigned by IANA upon request given that a client/server protocol
specific specification has been written. In the case of MARS Servers,
the client/server protocol specific specification was written at the
same time as SCSP, and thus a PID=0x0003 was assigned in .
SCSP places no topological requirements upon a MARS Server SG.
Obviously, however, the resultant graph of MARS Servers must span the
set of MARS Servers being synchronized. For more information about
the client/server protocol independent part of SCSP, the reader is
encouraged to see .
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