From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Tue May 11 2004 - 13:25:38 GMT-3
At 5:25 PM +0300 5/11/04, Dan wrote:
>This draft sound so much like atm LANE? I dont know why the don't
>just use LANE and adapt it to ethernet ;)
Well, in a manner of speaking, there is an equivalent. You may have
heard of MPLS being called "ATM without cells", and that's not a bad
term -- it removes some of the overhead of ATM, can use more flexible
standard IP routing, and can carry Ethernet payloads.
So Ethernet-over-MPLS is functionally equivalent to LANE. There are
lots of variants that can apply, especially when bandwidth isn't a
constraint, such as Ethernet in PPP over L2TP over almost anything,
including ATM and MPLS.
>
>
>On Tue, 11 May 2004 10:20:23 -0400, Howard C. Berkowitz
><hcb@gettcomm.com> wrote:
>
>>At 1:00 PM +0530 5/11/04, Sachin Shenoy wrote:
>>>Hi,
>>>
>>>I was wondering if trunking over WAN is possible ...
>>>What I mean by that is
>>>
>>>
>>> Serial Link
>>> SW1----R1<------------->R2--SW2
>>>
>>>Is it possible to trunk VLANs from SW1 to SW2 ???
>>>(So LAN IP ranges for VLANs on SW1 and SW2 will be the same !)
>>
>>In certain, restricted, cases, usually requiring gigabit or faster
>>transmision media, yes. See such things as Private VLAN Service
>>(more the IETF term) and QinQ encapsulation (although the latter
>>is not a WAN protocol, but the distinction between LAN and WAN is
>>less and less useful). It's also possible using MPLS.
>>
>>Why do you consider this a good idea? It has potential scalability
>>issues, for example, involving both absolute delay greater than
>>expected by LAN devices. Another scalability issue is that
>>uncontrolled growth at both locations may cause the safe number of
>>devices in a broadcast domain to be exceeded.
>>
>>I've been asked to do this many times, on the basis that "layer 2
>>is simpler." At a certain level of scaling, it is not. In
>>general, in the circumstance you describe, I'd route between the
>>sites without overwhelming evidence to the contrary. I can even
>>keep VLAN numbers consistent at both sites.
>>
>>Unfortunately, studying for the CCIE lab overempasizes lots of
>>things that may be possible, but not a good idea in the real world.
>>
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>
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