RFC 1953 (rfc1953) - Page 2 of 20

Ipsilon Flow Management Protocol Specification for IPv4 Version 1

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