The MPLS WG Archive

["Satoru Matsushima" <satoru@japan-telecom.co.jp>]

Hi all,

According to draft-ietf-mpls-label-encaps-08.txt,

> 2.4.3. IP-dependent rules

>   We define the "IP TTL" field to be the value of the IPv4 TTL field,
>   or the value of the IPv6 Hop Limit field, whichever is applicable.
>
>   When an IP packet is first labeled, the TTL field of the label stack
>   entry MUST BE set to the value of the IP TTL field.  (If the IP TTL
>   field needs to be decremented, as part of the IP processing, it is
>   assumed that this has already been done.)
>
>   When a label is popped, and the resulting label stack is empty, then
>   the value of the IP TTL field SHOULD BE replaced with the outgoing
>   TTL value, as defined above.  In IPv4 this also requires modification
>   of the IP header checksum.

but this section had continue following.

>   It is recognized that there may be situations where a network
>   administration prefers to decrement the IPv4 TTL by one as it
>   traverses an MPLS domain, instead of decrementing the IPv4 TTL by the
>   number of LSP hops within the domain.

I think that is very useful for VPNs, but this section had not consider
this situations.

Could somebody tell me the behavior of "ingress|egress LSR/LER" on 
this situations?

Thanks in advance.


--
Satoru Matsushima