The MPLS WG Archive

[Eric Gray <eric.gray@sandburst.com>]

Yu,

    Hello.  Please see my earlier answer on this subject at:

    http://cell.onecall.net/mhonarc/mpls/2001-Mar/msg00009.html

    If this does not clear up your questions below, let me know.

Thanks!
--
Eric Gray

You wrote:

> Hi, everybody,
>
> Here are some questions about MPLS LDP State Machine.
> Can someone give me explanation?
> Thanks in advance.
>
> 1. Trigger Control Block is discribed unclearly in "LDP State Machine"(draft-ietf-mpls-ldp-state-04.txt).
> (1)what is it on earth?
> (2)what is its function?
> (3)what information does it contain?
> (4)how does it operation?
> (5)how does it interwork with LSP control block?
>
> 2.Next Hop Control Block is discribed unclearly in "LDP State Machine"(draft-ietf-mpls-ldp-state-04.txt).
>    I have the same questions about Next Hop Control Block as 1.
>
> 3.Next Hop Control Block = Next Hop Trigger Control Block ?
>
> In draft-ietf-mpls-ldp-state-04.txt,
> -------------------------------------------
> 3.2.1 LSP Control Block
>
>    For each LSP, an LSP Control Block is defined which may contain the
>    following information:
>      - Upstream Label Request ID (assigned by the upstream LSR),
>                 which is the 'Message Id' in the Label Request Message
>                 received from the upstream LSR.
>      - Downstream Label Request ID (assigned by this LSR itself),
>                 which is 'Message Id' in the Label Request Message sent to
>                 the     downstream LSR.
>      - Upstream LDP Identifier
>      - Downstream LDP Identifier
>      - State
>      - FEC
>      - Upstream Label (assigned by this LSR)
>      - Downstream Label (assigned by the downstream LSR)
>      - Trigger Control Block Pointer, (Only used at the ingress LSR
>                 of a LSP) that points to the control block that triggers
>                 setting up this LSP or tearing down this LSP.
>      - Next Hop Control Block Pointer, which points to the control
>        **********************
>                 block which is used for switching over to a better LSP.
> ---------------------------------------------------------------------
>   Is Next Hop Control Block = Next Hop Trigger Control Block?
>
>             Yu Wang
>             wangyu7707@263.net