RFC 2124 (rfc2124) - Page 3 of 21

Cabletron's Light-weight Flow Admission Protocol Specification Version 1

RFC 2124                          LFAP                       March 1997


2.  Message Flows

   Initiating message flows between CCE and FAS entities always
   originate at the switch.  Therefore, the switch is the point at which
   connectivity is originated.  The CCE must have IP reachability using
   some approach described elsewhere (e.g.  [1577] or [LANE]) and an IP
   address for the FAS must be preconfigured at the switch CCE.  The CCE
   establishes TCP connectivity using the registered port number - ###.

   As shown below, Flow Admission Request (FAR) messages are sent by a
   switch's Call Control Entity (CCE) to the Flow Admission Service
   (FAS). These messages are sent when a flow is about to be set up by
   the switch and contain specific information relating to the flow -
   such as flow identifier, source/destination and qualifying
   information about the flow - that may be required to determine the
   admissibility of the flow and any operating policies that apply to
   the flow if it is admitted.

   The FAS responds with a Flow Admission Acknowledge (FAA) message (to
   the CCE) with a status indicating connection admissibility and any
   operating policy information that applies to the flow.  If a FAA
   message contains mandatory operating policies that the switch CCE
   does not understand, the switch would abort the flow using the Flow
   Admission Update (FAU) message.

    ,--------------------.            ,--------------------.
    |        FAS         |            |       Switch       |
    |                    |            |        CCE         |
    `--+----+----+-------'            `------+-----+----+--'
     ^ | ^  ^ |  ^ |  ^ ^              ^ ^  ^ |  ^ |  | ^ |
     | | |  | |  | |  | |     AR       | |  | |  | |  | | |
     | | |  | |  | |  | '--------------' |  | |  | |  | | |
     | | |  | |  | |  |       ARA        |  | |  | |  | | |
     | | |  | |  | |  '------------------'  | |  | |  | | |
     | | |  | |  | |          FUA           | |  | |  | | |
     | | |  | |  | `------------------------' |  | |  | | |
     | | |  | |  |            FUN             |  | |  | | |
     | | |  | |  `----------------------------'  | |  | | |
     | | |  | |               FCR                | |  | | |
     | | |  | `----------------------------------' |  | | |
     | | |  |                 FCA                  |  | | |
     | | |  `--------------------------------------'  | | |
     | | |                    FAU                     | | |
     | | '--------------------------------------------' | |
     | |                      FAA                       | |
     | `------------------------------------------------' |
     |                        FAR                         |
     `----------------------------------------------------'



Amsden, et. al.              Informational