RE: BFD LSP Ping

["Reshad Rahman (rrahman)" <rrahman at cisco.com>]

It's not clear to me either why the single-hop UDP port is used if TTL check isn't needed. I agree that it seems to make more sense to use multihop in both directions.

Regards,
Reshad.

-----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 2:26 PM
To: Nitin Bahadur
Cc: Kireeti Kompella; rtg-bfd at ietf.org; Rahul Aggarwal
Subject: Re: BFD LSP Ping

Hi Nitin,

Also thinking of it if we do not care about the TTL we can use
Multihop in such a case. Thats the only big difference between the
functionality provided my a Multihop versus a single hop session.

Thanks,
Vishwas

On Wed, Oct 28, 2009 at 11:22 AM, Vishwas Manral <vishwas.ietf at gmail.com> wrote:
> 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
>>
>