Re: BFD echo mode

[David Ward <[e-mail]>]

Nobo -

On Nov 27, 2008, at 3:41 AM, Nobo Akiya (nobo) wrote:

>
> Hello Vishwas.
>
> Couple of add-on comments, for single-hop.
>
>> Seeing some vendor documentation it seems they use a seperate
>> port for the echo mode - as the source and the destination
>> address.
>
> I hope vendors aren't using different udp dest port for echo packets.
>
> http://tools.ietf.org/html/draft-ietf-bfd-v4v6-1hop-08 Sec4.1.
>
> BFD Echo packets MUST be transmitted in UDP packets with destination
> UDP port 3785 in an IPv4 packet.
>
>> Can the asusmption that the echo mode packet is a BFD packet
>> be made (so the BFD source / dest packet identifiers can be
>> used)? The base BFD spec seems to state the content of the
>> packet need not be specified as the packet is just looped back.
>
> BFD echo packets can be identified by UDP dest port 3785.
> Data beyond UDP header is not specified, and that's left up to  
> vendors.
>
>> So I can see how we could look an IP packet in the case of
>> Single Hop (by having the MAC Destination Address of the
>> peer) but having IP address and destination the same (as of
>> the source).
>
> I don't think there's anything that specifies that dest & src  
> addresses
> must be the same. For dest addresses tho, it maybe easier to
> demultiplex if dest address is the outgoing interface.


DW: there is nothing in the spec that says the addrs have to be the  
same.


-DWard

>
> Thanx,
> Nobo
>