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Re: Linux implementation of MPLS

  • From: Sundeep Singh <singh0de@ee.iitb.ac.in>
  • Date: Sat, 18 Sep 2004 00:16:16 +0530 (IST)
  • cc: sudeepg@cse.iitb.ac.in, mpls-ops@mplsrc.com
  • Resent-Date: Fri, 17 Sep 2004 15:38:08 -0400

Hi,

I feel label-space will be important even if u assign unique labels to 
FECs at the ingress LSR. Imagine thie scenario wherein,

FECs A, B, C are assigned labels (1,2,3) uniquely by the ingress...

At the next LSR, these labels are swapped (1,2,3)->(2,2,3), then in 
this case the information provided by the label-space would be 
important for swapping at the next LSR. (althou i am not really sure 
whether the swapping (1,2,3)->(2,2,3) is really valid !!)

--Sundeep.


On Fri, 17 Sep 2004, M.V. Padmini wrote:

> Hi sudeep,
>
> Well, we are talking of a static routing scenario here.  When we alreadly
> know the LSR, where where is the need to use the label space info?  (well
> pardon me since i have still not read the doc. completely!).  Since the
> labels on the LSRs are unique, there is no question of messing up.  Well,
> as far as the simple routing is concerned, unique label for every FEC
> should work fine.  May be its required in some other cases i.e. Tunnel
> etc.  Am not sure.  The other reason could be not to run out of labels!!
>
> - Padmini
>
>
>> Hi Padmini,
>>   We are also in the process of creating a MPLS test-bed in IITB. I
>> guess
>> the notion of lablespace is to identify the interface that the labels
>> come  from (as you have rightly said), but this concept is useful in
>> processing  at the hop on the basis of interfaces that it come from,
>> rather than  trying and identifying each and individual labels and then
>> processing.  Labelspaces can make some processing fast.
>>
>>   As far as a small test-bed is considered, it doesn't make a difference
>> to
>> use or not to use labelspaces.
>>
>>   I have successfully traversed ping packets using MPLS on my test-bed.
>> But
>> ssh and other application packets seem not to work as of now. Lets see.
>> Efforts are on :)
>>
>> ciao,
>> Sudeep
>>
>>
>> On Fri, 17 Sep 2004, M.V. Padmini wrote:
>>
>>>
>>> We are in the process of implementing a Test bed for MPLS using linux
>>> boxes.  Having gone through the mplsadm literature, they seem to be
>>> using two parameters (label, labelspace) to be associated with each
>>> Interface for an FEC.  The labelspace is supposed to identify the
>>> interface (from which it came) where the labels could be same (labels
>>> coming from different interfaces).
>>>
>>> Is there a need to do this?  If you enforce the uniqueness of the
>>> label wrt to a FEC, dont u think that there is no requirement for a
>>> labelspace. Am i missing something?
>>>
>>> Thanks in advance.
>>>
>>>
>>>> Abhishek Mittal wrote:
>>>>> 6> Fix up the MTU size
>>>>
>>>> After upgrading to a newer IOS on the Catalyst yesterday, I just
>>>> added MPLS IP to the 12k router again --- works fine now (with 1512
>>>> as MTU on all used interfaces) ...
>>>>
>>>> -gg
>>>>
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>> --
>>
>> When a great leader's work is done, people say "we did it ourselves".
>> -Tao
>>
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>
> ____________________________________________
> ERNET Project
> Dept. of Computer Science and Engineering
> IIT Delhi
> New Delhi - 110 016
>
> Phone: +(91)-11-2659 6009
>
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-- 
Sundeep.

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