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Re: TTL value of VPN Label at the Ingress

  • From: "Daipayan Kar Choudhuri" <daipayan@deccanetworld.com>
  • Date: Fri, 13 Feb 2004 11:01:54 +0530
  • Organization: Deccanet Designs
  • Resent-Date: Fri, 13 Feb 2004 01:09:21 -0500
  • To: "Kumar S" <ps2kumar@yahoo.com>, "mplsrc" <mpls-ops@mplsrc.com>

 
Hi Shailender,
                       Thanks for your mail . For normal MPLS forwarding the IP TTL is copied in the MPLS header after decrementing it by one. My question is who should carry this TTL value in case of L3VPN ,the IGP label or the VPN Label ?
 
Regards,
Daipayan
 
----- Original Message -----
From: Kumar S
Sent: Saturday, February 07, 2004 5:07 PM
Subject: Re: [MPLS-OPS]: TTL value of VPN Label at the Ingress

Hi Daipayan,
Unlike L2 VPN TTL need to be propagated through MPLS core incase of L3 VPN. TTL value of the IP field has to be copied to the MPLS label during label imposition at the ingress router as is the case of normal MPLS path.
 
The reason why RFC specifically says 2 is added in TTL field to the VC label in case of L2 VPN is L2 VPN is a pseudo wire service between customer edge devices and is emulating some layer 2 service. But this is not the case with L3 VPNs where L3 routing in the core is always assumed by Customer.
 
Regards
Shailender
 
Daipayan Kar Choudhuri <daipayan@deccanetworld.com> wrote:
Hi all ,
           I have a query regarding the VPN Label value for L3VPN . What should be the TTL value for the VPN label at the ingress PE ?  As I understand from the martini draft for L2 Transport  the TTL value of the VC label is set to 2 at the ingress but RFC 2547 does not discuss about the TTL value of the VPN Label at the ingress . Please throw some light on this.
 
Regards,
Daipayan
 

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