Subject: BFD LSP Ping

From: Vishwas Manral <[email-masked]>
Date: Wed, 28 Oct 2009 10:58:05 -0700

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

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From: Nitin Bahadur <[email-masked]>
Date: Wed, 28 Oct 2009 11:08:22 -0700

I'm not sure if the TTL check is mandatory/required for BFD MPLS.

Thanks
Nitin 

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf
> Of Vishwas Manral
> Sent: Wednesday, October 28, 2009 10:58 AM
> To: [email-masked]
> Cc: Kireeti Kompella; Rahul Aggarwal
> Subject: BFD LSP Ping
> 
> Hi,
>

---

From: Vishwas Manral <[email-masked]>
Date: Wed, 28 Oct 2009 11:22:43 -0700

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

---

From: Vishwas Manral <[email-masked]>
Date: Wed, 28 Oct 2009 11:26:09 -0700

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

---

From: "Reshad Rahman (rrahman)" <[email-masked]>
Date: Wed, 28 Oct 2009 19:09:02 -0400

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: [email-masked] [mailto:[email-masked]] On Behalf Of Vishwas Manral
Sent: Wednesday, October 28, 2009 2:26 PM
To: Nitin Bahadur
Cc: Kireeti Kompella; [email-masked]; Rahul Aggarwal
Subject: Re: BFD LSP Ping

Hi Nitin,

Thanks,
Vishwas