Re: [mpls-linux-general] How do you want to use TC with MPLS?

[Olivier D. <Oli...@rd...>]

Hi Steven,

Steven Van den Berghe wrote:

> Hi Jim,
> 
> First of all, the label/exp classification to a diffserv per hop behaviour must be
> done in every node (not only the ingress).
> Now, about our diffserv approach, what we currently (read as experimental) do is:
> 
> * ingress node
>     netfilter ==refence to label/exp==> mpls_output ==fixed label/exp mapping to
> tc_index ==> Queueing/scheduling
> (sorry Jim, we're bypassing all your hard work on getting the labels attached to
> routing entries and go direct from iptables classification to mpls_output)
> The "direct iptables"-approach  has only been written last week, and is currently
> under test.


Just a point of clarification. Do you bypass the ip stack at ingress or 
LSR node ? In the first case, how do you handle all the normal ip stuff 
ie. ip header checking/integrity, destination adresse checking and the 
fragmentation in case of the packet become to big after adding a label ?

We have envisage to bypass this part of ip stuff - going directly from 
iptable to mpls_output (in a similar way the iptable mirror function 
call directly ip_route_output_slow). We had let down this option because 
of all the ip stack stuff included the fragmentation.

Regards,

Olivier


> 
> *core node
>     mpls_input==> mpls_output ==fixed label/exp mapping to tc_index ==>
> Queueing/scheduling
> 
> The mapping from label/exp to tc_index is done in sch_dsmark (a pseudo scheduler
> that was originally used to set tc_index based on the dscp field in the
> IP-header).
> dsmark is however no requirement (you could use u32 classifiers, ....), but it
> allows to have a uniform diffserv configuration for a combination of mpls and
> 'normal' ip traffic.
> 
> Hope this helps,
> Steven
> 
> "James R. Leu" wrote:
> 
> 
>>Hello all,
>>
>>I'm working on testing some of the feature I've added recently, and I just
>>realized I have no idea how anyone would use them.  So I'm asking all of you
>>how do you want to use the features of TC with MPLS?  Are the feature provided
>>by iptables more apt for being used with MPLS?
>>
>>One way I know people want to use TC and MPLS is with respect to
>>DiffServ.   Using the DSCP to determine which LSP (L-LSP) or which EXP/LSP
>>(E-LSP) a packet should be sent with, then mapping the LSP or EXP/LSP
>>back to a DSCP at egress.  But what about the LSRs?  Don't they need to
>>do special queuing?  How does TC accomplish special queing without MPLS?
>>How should it work with MPLS?
>>
>>Thanks,
>>Jim
>>
>>PS Yes Olivier, I'm now starting to catch up with you, soon I'll understand why
>>your iptables work is so useful :-)
>>
>>PPS Please Steven respond and explain how you made your DiffServ stuff work
>>
>>--
>>James R. Leu
>>jl...@mi...
>>
>>_______________________________________________
>>mpls-linux-general mailing list
>>mpl...@li...
>>https://lists.sourceforge.net/lists/listinfo/mpls-linux-general
>>
> 
> --
> Steven Van den Berghe
> ste...@in...
> Workgroup Broadband Communication Networks
> Department Information Technology
> Ghent University - Belgium
> Phone:  +32 (0)9 267 35 86 | Fax  :  +32 (0)9 267 35 99
> *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
> DiffServ over MPLS for Linux: http://dsmpls.atlantis.rug.ac.be
> *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
> Application has reported a 'Not My Fault' in module
> KRNL.EXE in line 0200:103F
> 
> 
> *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
> 
> 
> 
> 
> _______________________________________________
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> mpl...@li...
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> 
> 


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