RFC 2124 (rfc2124) - Page 3 of 21
Cabletron's Light-weight Flow Admission Protocol Specification Version 1
Alternative Format: Original Text Document
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