Re: AToM header

Hi Brian

Yes it do make sense, thanks a lot for clarification.

On Sat, Apr 27, 2013 at 12:55 AM, Brian McGahan <bmcgahan_at_ine.com> wrote:

> You essentially have two layer 2 headers, an outer layer 2 header and an
> inner layer 2 header. The inner layer 2 header is the one that you are
> tunneling. It could be Ethernet, Frame Relay, ATM, PPP, etc. This is why
> it's considered "Any Transport" over MPLS. So suppose your network looks
> like:
>
> CE1 -- PE1 -- MPLS CORE -- PE2 -- CE2
>
> Let's assume that the links between the CEs and the PEs are T1s
> running PPP, and the MPLS core is running Ethernet (10/40/100G, etc.) CE1
> pings CE2, and when the frame leaves CE1 and is encapsulated into MPLS by
> PE1 the packet would look like:
>
> Ethernet | MPLS | PPP | IP | ICMP | ECHO
>
> The outer Ethernet header is just normal Ethernet. The MPLS
> header is where your transport and VPN pseudowire labels are, along with
> the control word. The PPP and the rest of the payload is what's being
> tunneled. From CE1 and CE2's perspective, they look like they're on the
> same layer 2 segment, but it's actually a virtual circuit (hence "pseudo"
> wire) that runs over the MPLS network.
>
> Make sense?
>
> Brian McGahan, CCIE #8593 (R&S/SP/Security), CCDE #2013::13
> bmcgahan_at_INE.com
>
> Internetwork Expert, Inc.
> http://www.INE.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> vishal bhugra
> Sent: Friday, April 26, 2013 4:37 AM
> To: CCIE GroupStudy; Online Study List
> Subject: AToM header
>
> Hello experts
>
> While studying the MPLS I came across the AToM. It states that AToM is
> basically to provide layer 2 connectivity to customer. When reading the
> data plane communication of the AToM the explanation given is while packet
> comes to ingress PE, it will put 2 labels on it VC label and tunnel label.
>
>
> *Now my Query are as :-
>
> 1) MPLS is 2.5 shim header. How can I say label over L2 Frame ?
>
> *
> *2) Control Word is a 32 bit field inserted between layer and VC label,
> again how this is possible based on my above query ?*
>
>
>
>
> --
> Thanks&regards
>
> Vishal
> +91 8587900305
>
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> Thanks&regards
>
> Vishal
> +91 8587900305
>
> Best way to predict the future ..... is to create it
>
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-- 
Thanks&regards
Vishal
+91 8587900305
Best way to predict the future ..... is to create it
Blogs and organic groups at http://www.ccie.net