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[MPLS] LDP GR query

  • From: little_star@huawei.com
  • Date: Thu, 19 Oct 2006 08:46:37 +0800

Title: $B6uGr(B
Hello Ramesh Huliyar,
You said,
Now, coming to the case where the 2 LSR are helper router (this is identified during LDP Session establishment where Reconnect timer is set to zero), then the moment LSR comes to know (usually by hello hold time expire) its neighbor is down, LDP session is brought down and it will not enter GR mode.

 
I think,the Reconnect timer is used for next restart,not used for this time

RFC 3478

2. LDP Extension

Setting the FT Reconnect Timeout to 0 indicates that the sender of

   the TLV will not preserve its forwarding state across the restart,

   yet the sender supports the procedures, defined in Section 3.3,

   "Restart of LDP communication with a neighbor LSR" of this document,

   and therefore could take advantage if its neighbor to preserve its

   forwarding state across the restart.

 

If the LSR set the Reconnect Timeout to 0 and send this TLV to it's neighbour,it's neighbour will not help the LSR resume when the LSR restart next time.

 

 

Lixing wang
 
 
 
----- Original Message -----
Sent: Tuesday, October 17, 2006 4:28 PM
Subject: Re: [MPLS] LDP GR query

Hello Lixing Wang,

As I had mentioned earlier, when there is a link failure (in this case, it is identified using BFD), the LDP session is removed and hence RTA and RTB will delete the lsp and reestablish the session. BFD can provide failure detection on any kind of  path between systems, including direct physical links, virtual  circuits, tunnels, MPLS LSPs, multihop routed paths, and   unidirectional links (so long as there is some return path, of  course.) So here even though the link failure is not occuring on the connected interface, BFD can identify the link failure.

Now, coming to the case where the 2 LSR are helper router (this is identified during LDP Session establishment where Reconnect timer is set to zero), then the moment LSR comes to know (usually by hello hold time expire) its neighbor is down, LDP session is brought down and it will not enter GR mode.

Regards
Ramesh Huliyar
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