Subject: Re: PW Transport LSP nature

From: Luca Martini <[email-masked]>
Date: Mon, 15 Nov 2004 10:20:02 -0700

Shahram Davari wrote:

>Hi,
>
>Is it safe to assume that the Transport LSP can't be in Uniform-mode?
>The reason that I think this is true, is that a Transport LSP should not have
>the restriction of setting its TTL=2 (same as the Interworking Label). Also a Transport
>LSP can carry many PWs, that could have different CoS and possibly TTL.
>
>  
>
true, but when the PSN label is popped, the TTL is always decreased , 
and copied down. Hence setting the PW label TTL=2 does not do much 
unless the PEs are adjacent. Anyway setting the TTL=2 was removed from 
the spec almost 2 years ago.

>BTW, why is the TTL of IW label set to 2 rather than 1? Is it because of PHP?
>
>  
>
it was set to 2 for the adjacent PE case only. If the PEs are adjacent , 
then there is no "PSN label", and setting the TTL=2 could prevent the 
packet from being mis-switched .... This was the thought behind the 
original design.
2 is the lowest value you can set the TTL , otherwise the TTL will 
expire before the packet is forwarded out the attachment circuit.
Look at rfc3032

Luca

>Thanks,
>-Shahram
>
>_______________________________________________
>pwe3 mailing list
>[email-masked]
>https://www1.ietf.org/mailman/listinfo/pwe3
>
>  
>

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From: Stewart Bryant <[email-masked]>
Date: Mon, 15 Nov 2004 21:18:01 +0000

> the spec almost 2 years ago.

Have you got a reference to the list discussion where this was
descided?

The latest that I can find is

http://www1.ietf.org/mail-archive/web/pwe3/current/msg04219.html

where the TTL=2 was agreed.

- Stewart

---

From: Luca Martini <[email-masked]>
Date: Mon, 15 Nov 2004 17:50:35 -0700

Stewart,

No I can't remember exactly which e-mail. This was a long time ago. If 
you really thing we need to find out I can go through the SCCS version 
database of the draft source, and find out which is the first version 
that dropped it. This will take some time  as there are 118 versions in 
it ..... So I would rather not look ...;-)

Luca

Stewart Bryant wrote:

>> unless the PEs are adjacent. Anyway setting the TTL=2 was removed 
>> from the spec almost 2 years ago.
>>
>
>

---

From: Stewart Bryant <[email-masked]>
Date: Tue, 16 Nov 2004 08:57:24 +0000

> it ..... So I would rather not look ...;-)

It's not the SCCS version that we need, it's the PWE3 WG email that
agreed the change that we need. I know that the change went into arch 
at -04, but I can't find anything that said take it out again and for
what reason.

- Stewart