The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

The LSP-ID defined in Y.1711 is essentially a combination of LSP-ID + Tunnel-ID
as defined in RSVP-TE.  

In the current version of Y.1711, 4 bytes are assigned to this. However the current version of Y.1711 sets the first 2 octets of this field to zero for future use. Therefore two methods are possible:

1) Compress the LSP-ID + Tunnel-ID in to 2 bytes 

2) You could use the first 2 octets, and encode the 2-byte RSVP-TE LSP-ID in the first 2 octets of Y.1711 LSP-ID and encode the 2-byte RSVP-TE Tunnel-ID in the last 2 octets of Y.1711 LSP-ID.

Just a question, isn't it possible to change the LSP by changing the Tunnel-ID, rather than LSP-ID?

-Shahram

> -----Original Message-----
> From: George Swallow [mailto:swallow@cisco.com]
> Sent: Wednesday, November 06, 2002 10:18 AM
> To: David Allan
> Cc: George Swallow; Der-Hwa Gan; Gray, Eric; mpls@UU.NET;
> swallow@cisco.com
> Subject: Re: Decreasing TE-LSP bandwidth, "interoperability 
> issue" (fwd)
> 
> 
> 
> > I was envisioning a case where a bandwidth change was not a 
> separate tunnel
> > setup, the LSP ID changed without any interruption or change in the
> > conntectivity of the path . If there is build the new then 
> tear down the
> > old, then there is no gap in any monitoring case.
>  
> If you change the LSP-ID, that changes the sender-template.  Ipso
> facto a new setup.
> 
> > As for TTSI, it's simply a node specific LSP Identifier 
> that allows for an
> > IPv4/v6 LSR ID and 32 bits for an LSP identifier. The 
> assumption is that the
> > originating LSR most usefully administers LSP-IDs 
> independently of the
> > individual control protocol used. The initial draft of 
> Y.1711 was focused on
> > P2P ER-LSPs which meant RSVP-TE or CR-LDP, hence the 
> stipulation that the
> > first two bytes of the LSP-ID were padded with zeros to 
> align with LSP-ID as
> > defined in the signalling protocols. If there is a problem 
> with this, it is
> > not leaping out at me....
> 
> As we use it, an (RSVP-TE) LSP-ID is *only* unique to the tunnel.  We
> just use it as an instance number and increment it when we reroute or
> change bandwidth.  If I setup five tunnels they will have five
> different tunnel-IDs, but they can *all* have the same LSP-ID.
> 
> To uniquely identify a TE-Tunnel LSP. you need *all* of the fields in
> the session and sender-template objects.  That why we carry those in
> LSP ping.
> 
> ...George
> 
> ==================================================================
> George Swallow       Cisco Systems                  (978) 497-8143
>                      250 Apollo Drive
>                      Chelmsford, Ma 01824
>