Re: BFD confusion

Hey Abraham

So in a broadcast multi access networks, the neighbour should send four
separate unicast packets to the nieghbors to set up a BFD session. Because
BFD uses unicast session with all its neighbours , So it should send a
unicast packet to every one in a broadcast multi aces snetowrk
Am i right ?

Yes i got the Discriminator logic in BFD.

So BFD echoes the BFD data packets with its neighbors. So whether BFD is a
control palne protocol or a dat aplane protocol

As per the RFC , BFD has the tendency to work on both control plane and data
palce.

In which cases it works in Data plane and in which case it is a control
plane protocol.

Cheers mate

On Fri, Jul 1, 2011 at 4:00 PM, Abraham, Tharak <tharakabraham_at_gmail.com>wrote:

> 1. If its application specific anything above 1024 is accepted.
> But numbers available in drafts are 3784/3785 (single hop and multihop
> again should vary)
>
> 2. Unicast
>
> 3. Correct. Two fields named "My Discriminator" and "Your Discriminator"
> works in such a way that the local discriminator is sent in the My
> Discriminator field in the BFD Control packet, and is echoed back in the
> Your Discriminator field of packets sent from the remote end. Discriminator
> value identifies each session, and must be unique among all BFD sessions on
> the system.
>
> Best Regards,
> Tharak Abraham Luke
>
>
> On Fri, Jul 1, 2011 at 3:38 PM, HEMANTH RAJ <hemanthrj_at_gmail.com> wrote:
>
>> Hey Abraham,
>>
>> Thanks for ur explanation. I still have some more questions
>>
>> 1.So now BFD runs over UDP , BFD uses which port numbers to communicate.
>>
>> 2. In the BFD packet, the destination address is a multicast address or a
>> unicast address. ie I am asking about the BFD hellos.
>>
>> 3. In the discriminator field. FOr example if it is broadcast mulit acess
>> network , there are 4 four neighbors in the same interface, So it maintains
>> a unique discriminator for each neighbor, Am i getting it right.?? Correct
>> me i f i am wrong
>>
>> So in point to point mode , there should be no discriminator field right?
>>
>>
>> On Fri, Jul 1, 2011 at 3:07 PM, Abraham, Tharak <tharakabraham_at_gmail.com>wrote:
>>
>>> Hemanth,
>>>
>>> 1. Discriminator fields are used to uniquely identify multiple BFD
>>> sessions between the same pair or sessions w.r.t Multiaccess networks. I
>>> hope i needn't explain multiplexing and demultiplexing.
>>>
>>> 2. BFD runs on top of the [ UDP+IP+L2 ]
>>>
>>> 3. BFD is generally specified under an interface and hence will take the
>>> primary ip add of the interface.
>>> It doesn't form adjacency like the hello protocols used in ospf/eigrp but
>>> generally works based on echoing.The source and dest ip would be the same
>>> but L2 address would be of the neighbor.
>>>
>>> You may also tie the BFD process with the existing routing protocol too.
>>>
>>> Sorry if it sounds confusing but Implementation w.r.t BFD mode always
>>> depends ;)
>>>
>>>
>>> Best Regards,
>>> Tharak Abraham Luke
>>>
>>>
>>> On Fri, Jul 1, 2011 at 1:04 PM, HEMANTH RAJ <hemanthrj_at_gmail.com>wrote:
>>>
>>>> Hi guys
>>>> I am reading BFD RFC and i am not able to get some points in it
>>>>
>>>> 1. What is the use of Discriminator field in BFD Control ?. It says it
>>>> is
>>>> used to demultiplex control plane packets to their neighbor . i cant
>>>> understand what is called as demultiplex control plane packets to the
>>>> neighbors
>>>>
>>>> 2. BFD works on which layer . Is it a Layer 2 encapsulation or L3
>>>> encapsulation . or it s a L2.5 encapsulation.
>>>>
>>>> 3. Which address that BFD uses to communicate with its neighbor? RFC
>>>> says it
>>>> is application specific and i am not getting the point exactly ?
>>>>
>>>>
>>>> Can some one shed some light on it ?
>>>>
>>>>
>>>>
>>>> --
>>>> Problems arise because we talk,problems are not solved because we don't
>>>> talk
>>>> So good or bad talk to your affectionate one's freely.
>>>>
>>>> Yours Friendly,
>>>> H P HEMANTH RAJ
>>>> CCIE#28593 (R&S)
>>>> Cisco Systems
>>>>
>>>>
>>>> Blogs and organic groups at http://www.ccie.net
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> Problems arise because we talk,problems are not solved because we don't
>> talk So good or bad talk to your affectionate one's freely.
>>
>> Yours Friendly,
>> H P HEMANTH RAJ
>> CCIE#28593 (R&S)
>> Cisco Systems
>>
>>
>

-- 
Problems arise because we talk,problems are not solved because we don't talk
So good or bad talk to your affectionate one's freely.
Yours Friendly,
H P HEMANTH RAJ
CCIE#28593 (R&S)
Cisco Systems
Blogs and organic groups at http://www.ccie.net