Re: MPLS / Switching Method on Non Cisco Devices

What you are saying definitely makes sense and I think I did hurry a bit in
replying to your earlier message. But I still have got a few doubts,
 As you said CEF is cisco's way of doing MPLS forwarding , do you have an
idea if there are similar switching methods that are proprietary to other
vendors and required for MPLS functioning in them. Also, as it appears from
your email, MPLS can be achieved through normal hardware switching
mechanisms then why this dependency on CEF. If it is because of the well
known advantages that CEF has over other switching methods then does that
mean Cisco routers have an upper hand when it comes to MPLS on Cisco v/s
Non-Cisco devices or is it that everyone has got their own type of "Express
Forwarding" devised.

I hope I am not getting confused with things here !

Ravi

On Wed, Jan 13, 2010 at 7:47 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:

> I guess my message was not clear for you.
> (WAN?) encapsulation has all to do with MPLS being hardware friendly
> for switching, irrespective of the platform.
> CEF is a way to do hardware lookup of a large size routing key
> (destination IP) in a hierarchical structure (FIB).
> CEF mostly underutilized for MPLS, although the one size fits all
> way of using it for IP & MPLS at the same time works ok.
> Also, IP is as fast as MPLS from a switching standpoint in cisco's
> implementation AFAIK, and that is currently underadvertised because
> it shadows one of MPLS's perceived benefits.
>
> Again, my point of view.
> -Carlos
>
> Ravi Singh @ 13/01/2010 10:37 -0300 dixit:
> > Ahh..a reply finally ;-) .. Thanks Carlos .. however, my query is more
> > oriented towards the switching method utilized for MPLS in Non-Cisco
> routers
> > (Juniper etc .) rather than on the WAN encapsulation type or device
> > used..for example a cisco router would build a LFIB and LIB using CEF ,
> but
> > since non-cisco routers do not use CEF, do they build the same data
> > structures and if their packet switching method is similar to CEF which
> > builds FIB and adjacency tables..
> >
> > Thanks for your reply again,
> >
> > Ravi
> >
> > On Wed, Jan 13, 2010 at 1:18 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar
> >wrote:
> >
> >> Well, it seems that conceptual things are not very attractive as topics.
> >> (just some pepper to the mix :)
> >>
> >> CEF is cisco's way to do it, but in general, MPLS is hardware friendly
> >> no matter what way you do it, because it has a fixed size fixed position
> >> small label that can be used to determine where the frame/packet should
> >> go in constant time.
> >> ATM has a even better constant size frame (cell), but at the cost of
> >> forcing SAR (segmentation and reassembly) on upper stack.
> >> FR/ATM switches usually specify how many *bits* they can read in
> >> hardware to switch traffic, I guess nowadays MPLS-able switches should
> >> do the whole label.
> >>
> >> As to who decides the label, there are two alternatives to when it is
> >> done but always the link receiver is the one. Frame mode allows for it
> >> to be determined up front, usually when the FEC is created.
> >> Cell mode does it on-demand, to economize the number of circuits
> >> that are mapped to them. (label mapped to VPI/VCI)
> >>
> >> My understanding at least, hope it helps.
> >> -Carlos
> >>
> >> Ravi Singh @ 6/01/2010 8:52 -0300 dixit:
> >> > Greetings Everyone ,
> >>> From all the MPLS material I have read, I understand the dependency of
> >> CEF
> >>> on MPLS . However, just out of interest, I would like to know what
> >> switching
> >>> methods do the non-Cisco equipment utilize for MPLS functioning. I
> tried
> >>> finding the information on the web but could not get any valuable info.
> >>> I know nothing about Juniper or any other non-cisco equipment for that
> >>> matter but I am just curious to know how different is the switching
> >>> behaviour in these devices when compared to Cisco. So I am really not
> >>> looking for detailed technical stuff but just a clarity on who takes
> the
> >>> care of the label assignment in such a case.
> >>>
> >>> Cheers,
> >>> Ravi
> >>>
> >>>
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> >>>
> >> --
> >> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
> >
> >
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> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

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Received on Wed Jan 13 2010 - 22:22:05 ART