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Re: Linux implementation of MPLS

  • From: Sundeep Singh <singh0de@ee.iitb.ac.in>
  • Date: Sun, 19 Sep 2004 11:24:35 +0530 (IST)
  • cc: sudeepg@cse.iitb.ac.in, mpls-ops@mplsrc.com
  • Resent-Date: Sun, 19 Sep 2004 02:38:42 -0400

On Sat, 18 Sep 2004, M.V. Padmini wrote:

> Well, the debate may not end so soon after all!!
>
> First of all, when i meant unique labels - i meant it for a complete LSR
> and among all LSRs not confinig to the ingress.
>
> The idea i had in mind was - keep all edges of the graph unique - ur done.
If u can ensure that EVERY downstream LSR distributes UNIQUE label binding 
to their upstream peers for each FEC, then ofcourse, u r correct in saying 
that their will be no need of "per interface label-space".

> But this will lead to exhausting the labels very soon.
Not very soon!! u have (2^20)-1 UNIQUE labels to choose from...

hope the debate is now put to rest :)

--Sundeep.

> If u look at it
> carefully, you may need to keep the labels unique only between two
> adjacent sets of input and output labels.  Never the less, by putting in
> the label space, you are trying to build a heirarchical structure of
> labels.
>
> Does that make sense or am i off track?
>
>> 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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>>>>>
>>>>>
>>>>> ____________________________________________
>>>>> ERNET Project
>>>>> Dept. of Computer Science and Engineering
>>>>> IIT Delhi
>>>>> New Delhi - 110 016
>>>>>
>>>>> Phone: +(91)-11-2659 6009
>>>>>
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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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>
>
> ____________________________________________
> ERNET Project
> Dept. of Computer Science and Engineering
> IIT Delhi
> New Delhi - 110 016
>
> Phone: +(91)-11-2659 6009
>
>

-- 
Sundeep.

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