Subject: RE: LSP-ping

From: Shahram Davari <[email-masked]>
Date: Tue, 17 Jul 2001 12:57:01 -0700

George,

My scheme still works in the scenarios that you mentioned. Becasue the
egress LSR sends ICMP-ping toward the ingress LSR (not necessarily through any LSP)
, the same way that it sends the ICMP-Echo toward the ingress LSR. So both the ICMP-Echo (of the forward LSP) and the ICMP-ping of the reverse direction travel over the same 
path, which may or may not include some LSPs. The end result is that the ingress LSR
checks to see whether it is receiving any ICMP-ping from the egress LSR, and if so,
the reverse path (be it an LSP or anything else) is fine.

-Shahram

> -----Original Message-----
> From: George Swallow [mailto:[email-masked]]
> Sent: Tuesday, July 17, 2001 3:38 PM
> To: Shahram Davari
> Cc: 'Ping Pan'; [email-masked]'; [email-masked]
> Subject: Re: LSP-ping 
> 
> 
> > The ingress LSR should know which LSP is the reverse LSP.
> 
> Huh???  There may be no LSP directly from the egress LSR back to the
> ingress.  
> 
> Suppose we have a tunnel from A to D  A->B->C->D
> 
> D may have no tunnel to A but one to either B or C.  or D could have
> no tunnels but C has one to either B or A.  Or B could have a tunnel
> back to A.  Or the IP routed path in the reverse direction is not
> symmetric and the reply could be lost going down a tunnel from G to Q.
> 
> ...George
> 
> ==================================================================
> George Swallow       Cisco Systems                   (978) 244-8143
>                      250 Apollo Drive
>                      Chelmsford, Ma 01824
>