RFC 1953 (rfc1953) - Page 2 of 20
Ipsilon Flow Management Protocol Specification for IPv4 Version 1
Alternative Format: Original Text Document
RFC 1953 IFMP Specification May 1996
4.5 Error Message............................................17
References........................................................19
Security Considerations...........................................19
Authors' Addresses................................................19
1. Introduction
The Ipsilon Flow Management Protocol (IFMP), is a protocol for
instructing an adjacent node to attach a layer 2 label to a specified
IP flow. The label allows more efficient access to cached routing
information for that flow and it allows the flow to be switched
rather than routed in certain cases.
If a network node's upstream and downstream links both redirect a
flow at the node, then the node can switch the flow at the data link
layer rather than forwarding it at the network layer. The label
space is managed at the downstream end of each link and redirection
messages are sent upstream to associate a particular flow with a
given label. Each direction of transmission on a link is treated
separately.
If the flow is not refreshed by the time the lifetime field in the
redirect message expires, then the association between the flow and
the label is discarded. A flow is refreshed by sending a redirect
message, identical to the original, before the lifetime expires.
Several flow types may be specified. Each flow type specifies the
set of fields from the packet header that are used to identify a
flow. There must be an ordering amongst the different flow types
such that a most specific match operation may be performed.
A particular flow is specified by a flow identifier. The flow
identifier for that flow gives the contents of the set of fields from
the packet header as defined for the flow type to which it belongs.
This document specifies the IFMP protocol for IPv4 on a point-to-
point link. The definition of labels, and the encapsulation of
flows, are specified in a separate document for each specific data
link technology. The specification for ATM data links is given in
[ENCAP].
2. Flow Types
A flow is a sequence of packets that are sent from a particular
source to a particular (unicast or multicast) destination and that
are related in terms of their routing and any logical handling policy
they may require.
Newman, et. al. Informational