Re: BFD LSP Ping

[Vishwas Manral <vishwas.ietf at gmail.com>]

Hi Nitin,

BFD MPLS LSP is not changing anything in BFD other than what is
specified like - no echo and demand mode.

So I am assuming the TTL check is still the same for a single hop
session, and we can do the auth algorithm for the same.

I think we should for correctness and simplicity use Multihop sessions
in both directions.

Thanks,
Vishwas

On Wed, Oct 28, 2009 at 11:08 AM, Nitin Bahadur <nitinb at juniper.net> wrote:
>
> I'm not sure if the TTL check is mandatory/required for BFD MPLS.
>
> Thanks
> Nitin
>
>> -----Original Message-----
>> From: rtg-bfd-bounces at ietf.org [mailto:rtg-bfd-bounces at ietf.org] On Behalf
>> Of Vishwas Manral
>> Sent: Wednesday, October 28, 2009 10:58 AM
>> To: rtg-bfd at ietf.org
>> Cc: Kireeti Kompella; Rahul Aggarwal
>> Subject: BFD LSP Ping
>>
>> Hi,
>>
>> I noticed a basic issue with BFD LSP ping with a a TTL processing in a
>> Uniform Model LSP.
>>
>> The draft states that:
>>
>>
>>    The BFD control packet sent by the ingress LSR MUST be a UDP packet
>>    with a well known destination port 3784 [BFD-IP] and a source port
>>    assigned by the sender as per the procedures in [BFD-IP].
>>
>> A single hop session verifies the TTL is 255. However the TTL in the
>> IP header is changed at the Egress before the IP header handling
>> because we are using hte uniform model. I think the easiest and the
>> best way for this would be to use Multihop sessions in both
>> directions.
>>
>> Do let me know if I am missing something?
>>
>> Thanks,
>> Vishwas
>