RE: BFD echo mode

["Nobo Akiya (nobo)" <[e-mail]>]

 
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.

Thanx,
Nobo