Subject: Re: [TICTOC] FW: 1588 over MPLS draft

From: [email-masked]
Date: Mon, 19 Jul 2010 17:39:06 +0800

Hi Yaakov and all,
If GAL is used, the encapsulation is different from the current one. It 
may be: GAL -> Forward label -> ACH.... 
Then the compatibility should be considered:
1. It would be possible PE will treat "forward label" as ACH header.
2. It would be best if there is a way to identify PTP message type only 
through PTPA.

If the encapsulation is GAL -> ACH -> Forward label, I think it is also 
impossible.

BR
Lizhong

Stewart and all, 

Indeed, the limited number of reserved labels was the main drawback of the 
"reserved label" approach when I first raised it.

The other possibility of this sort was a special CoS bit combination,
but there are no universally defined CoS (yet).

So, are we back to the GAL ? 

If so, there are still at least 4 options :
1) define a new protocol type (plenty of openings in THAT registry!)
2) put 1588 packet into an ACH TLV
3) use IPv4 protocol type with 1588 over UDP/IP but mark it in some other 
way (e.g., reserved field)
4) define a new first nibble (0010 ?)  <ugh!>

Y(J)S

-----Original Message-----
From: tictoc-bounces at ietf.org [mailto:tictoc-bounces at ietf.org] On 
Behalf Of Stewart Bryant
Sent: Friday, July 16, 2010 00:04
To: tictoc at ietf.org
Subject: Re: [TICTOC] FW: 1588 over MPLS draft

  Reserved labels are very much a utility of last resort. There are only 
16 of them to last us the whole life of MPLS, so that should only be 
used when there is no other method.

It is not a good idea to probe the network to discover a capability, it 
is far better to know it through a property of  the routing protocol. 
That way you can match the path to the set of capable LSRs.

Stewart

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