Re: BFD echo mode

["Vishwas Manral" <[e-mail]>]

Dave,

Sounds good. So what you are saying is that adaptive timer support
needs to be there? Is the understanding correct.

-Vishwas

On Sun, Nov 30, 2008 at 11:50 AM, David Ward <[e-mail]> wrote:
> Additional congestion control isn't necessary if an implementation takes
> into consideration the adaptive timer support. This is if an implementer
> believes that BFD configuration would be set by an operator such that the
> already inconsequential amount of data being sent actually causes
> congestion. BFD should not be run over TCP due to overhead or UDP-lite due
> to lack of widespread deployment.
>
> -DWard
>
> On Nov 30, 2008, at 1:14 PM, Vishwas Manral wrote:
>
>> Hi Dave,
>>
>> Agree to what you say.
>>
>> I was also thinking of congestion control considerations to be put
>> into BFD for the Multi-hop case. The draft does not talk about it and
>> because BFD works on very short duration Hello's it may need to be TCP
>> friendly in some cases.
>>
>> Do let me know what you think?
>>
>> Thanks,
>> Vishwas
>>
>> On Thu, Nov 27, 2008 at 7:45 AM, David Ward <[e-mail]> wrote:
>>>
>>> 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
>>>>
>>>
>>>
>
>