Subject: Different UDP dest ports

From: Glen Kent <[email-masked]>
Date: Thu, 1 Apr 2010 06:01:33 +0530

Hi,

What is the motivation for having different UDP dest ports for
directly connected IP nexthops (3784) and multhop paths (4784) in BFD?

What do we lose by using just one, say 3784?

Glen

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From: "Shahram Davari" <[email-masked]>
Date: Wed, 31 Mar 2010 17:35:25 -0700

Hi,

The receiver needs to check the IPTTL=255 for 1hop, and the only way to differentiate between 1hop and multi-hop is by using different UDP dest port #.

-Shahram 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Glen Kent
Sent: Wednesday, March 31, 2010 5:32 PM
To: [email-masked]
Subject: Different UDP dest ports

Hi,

Glen

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From: Glen Kent <[email-masked]>
Date: Thu, 1 Apr 2010 06:09:36 +0530

Hi Shahram,

So the sender should be intelligent enough to use dst port 4784 if it
knows that the packet is being sent on a multihop path. Fair enough.
What happens if i need to send a packet destined to the system IP or
the loopback IP of a directly connected router? Should i use 3784 or
4784?

Glen

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From: "Shahram Davari" <[email-masked]>
Date: Wed, 31 Mar 2010 17:44:48 -0700

Hi Glen,

The loopback (12/8) address can't appear on a wire unless it is encapsulated in an IP or MPLS tunnel.
For directly attached routers you can use either 1hop (3784) or Multi-hop (4784). But for non-directly attached router you need to use Multi-hop.

Regards,
Shahram

-----Original Message-----
From: Glen Kent [mailto:[email-masked]] 
Sent: Wednesday, March 31, 2010 5:40 PM
To: Shahram Davari
Cc: [email-masked]
Subject: Re: Different UDP dest ports

Hi Shahram,

Glen

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From: Glen Kent <[email-masked]>
Date: Thu, 1 Apr 2010 06:18:45 +0530

Hi Shahram,

By loopback i did not mean 12/8 but was alluding to IP interfaces that
are not tied to a particular physical port. They could have any
logical routable IP address

Glen

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From: Vishwas Manral <[email-masked]>
Date: Wed, 31 Mar 2010 18:04:22 -0700

Hi Glen,

In my view when in doubt you should use the Multihop port.

Thanks,
Vishwas