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RE: BFD UDP ports

"Nobo Akiya (nobo)" <nobo@cisco.com> Fri, 05 December 2008 07:45 UTC

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Subject: RE: BFD UDP ports
Date: Thu, 04 Dec 2008 23:43:23 -0800
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Thread-Topic: BFD UDP ports
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From: "Nobo Akiya (nobo)" <nobo@cisco.com>
To: Nitin Bahadur <nitinb@juniper.net>, Vishwas Manral <vishwas.ietf@gmail.com>, David Ward <dward@cisco.com>, Dave Katz <dkatz@juniper.net>
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Hello Vishwas, Nitin.

> 
> On 12/4/08 12:30 PM, "Vishwas Manral" <vishwas.ietf@gmail.com> wrote:
> 
> > Hi
> > 
> > 1. I am a bit confused about using the same BFD destination port for
> > IPv4 and IPv6. Shouldn't we have different port numbers? I realized 
> > that even RIP which uses UDP uses different ports for IPv4 and IPv6.
> > Using the same port can be an issue in a few heavily used OS. Has 
> > anyone implemented BFD for IPv6?
> 
> Using the same port should be for v4 & v6 should be fine. I 
> know of at least
> 1 implementation ;-)
> 
> Thanks
> Nitin
> 

I know of another implementation which same dest port is used for v4 &
v6 =)

> 2. As BFD source port is not used for packet replies and as 
> the Source address/ ifindex may be a unique identifier for a 
> source, do we need not have the condition which states 
> "source port number SHOULD be unique among all BFD sessions 
> on the system". Can we downgrade this condition to a may?

I tripped over this requirement as well, and I agree that measurement of
the
wording strength is a bit confusing.

One soft correction on your statement is that source port MAY be used as
a
demultiplexing *aid*.

http://tools.ietf.org/html/draft-ietf-bfd-v4v6-1hop-08 Sec4.1:

   An implementation MAY use the UDP port source number to aid in
   demultiplexing incoming BFD Control packets, but ultimately the
   mechanisms in [BFD] MUST be used to demultiplex incoming packets to
   the proper session.

Thanx,
Nobo

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