LDP State Machine
RFC 3215
Network Working Group C. Boscher
Request for Comments: 3215 P. Cheval
Category: Informational Alcatel
L. Wu
Cisco
E. Gray
Sandburst
January 2002
LDP State Machine
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document provides state machine tables for ATM (Asynchronous
Transfer Mode) switch LSRs. In the current LDP specification, there
is no state machine specified for processing LDP messages. We think
that defining a common state machine is very important for
interoperability between different LDP and CR-LDP implementations.
We begin in section 1 by defining a list of terminologies. Then in
section 2, we propose two sets of state machine tables for ATM switch
LSRs that use downstream-on-demand mode, one method can be used for
non-vc merge capable ATM LSRs, while the other one can be used for
the vc-merge capable ATM LSRs. In section 3, we provides a state
machine for downstream unsolicited mode ATM LSRs.
We focus on the LDP state machines and the associated control blocks
used for establishing and maintaining LSPs. We do not describe state
machines for the "LDP controller" that is in charge of LDP session
initialization, address mapping messages management, routing
interface, etc. that is defined in the LDP specification.
Even though the state machines in this document are specific for
ATM-LSR, they can be easily adapted for other types of LSRs.
Boscher, et al. Informational [Page 1]
RFC 3215 LDP State Machine January 2002
Table Of Contents
1. Terminology ................................................... 4
2. State Machine for Downstream-on-Demand Mode ................... 4
2.1 An LSR's Behavior in the Case of a Next Hop Change ........... 4
2.2. ATM Switch LSR with No VC-merge Capability .................. 5
2.2.1 LSP Control Block .......................................... 5
2.2.2 States ..................................................... 7
2.2.3 Events ..................................................... 8
2.2.4 State Transitions .......................................... 9
2.2.5 State Machine .............................................. 10
2.2.5.1 State -- "IDLE" .......................................... 10
2.2.5.2 State -- "RESPONSE_AWAITED" .............................. 13
2.2.5.3 State -- "ESTABLISHED" ................................... 16
2.2.5.4 State -- "RELEASE_AWAITED" ............................... 21
2.2.6 Handling the Next Hop Change ............................... 23
2.2.6.1 Next Hop Trigger Control Block ........................... 24
2.2.6.2 States ................................................... 24
2.2.6.3 Events ................................................... 24
2.2.6.4 State Transition for next hop change ..................... 25
2.2.6.5 State Machine ............................................ 25
2.2.6.5.1 State -- "IDLE" ........................................ 25
2.2.6.5.2 State -- "NEW_NH_RETRY" ................................ 27
2.2.6.5.3 State -- "NEW_NH_RESPONSE_AWAITED" ..................... 28
2.2.7 LDP Related Message Handling ............................... 29
2.3. ATM Switch LSR with VC-merge ................................ 31
2.3.1 VC-merge ................................................... 31
2.3.2 Control Block .............................................. 31
2.3.3 State Machines for Downstream-on-demand Mode ............. 34
2.3.3.1 State of the Upstream LSP Control Block's State Machine
for Downstream-on-demand Mode ............................ 34
2.3.3.2 Events of the Upstream LSP Control Block's State Machine
for Downstream-on-demand Mode ............................ 35
2.3.3.3 State Transitions of the Upstream LSP Control Block's State
Machine for Downstream-on-demand Mode .................... 36
2.3.3.4 Upstream LSP Control Block's State Machine
for Downstream-on-demand Mode ............................ 37
2.3.3.4.1 State -- "IDLE" ........................................ 37
2.3.3.4.2 State -- "RESPONSE_AWAITED" ............................ 39
2.3.3.4.3 State -- "ESTABLISHED" ................................. 42
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