[j-nsp] Application of L2 VPN in Real World Scenario

[Guy Davies]

Hi Simon,

Your statement that there is a separate routing table for each p2p
link is not quite true.  With l2vpn (as opposed to l2circuit - aka
martini) there is a single routing-table for each collection of p2p
links associated with a single group of customer sites which belong to
a single l2vpn.  You may create a full mesh or a partial mesh
(including hub/spoke) between all the sites in the l2vpn.

Each site may have multiple logical connections over a single physical
connection into the SP network (e.g. VLANs or DLCIs).  Each of these
links is associated with one logical link at one remote site and
traffic arriving at the PE on that logical link is transported
straight to that remote PE and out of the far interface.  There is
usually some translation of DLCI or VLAN-id in this process.

l2vpn uses BGP to exchange label information and for auto-discovery of
PEs which are members of the same VPN.

l2circuit uses directed LDP for the exchange of label information and
(in JUNOS AFAIK) doesn't have an auto-discovery mechanism for
neighbours.  Each l2circuit is a true p2p circuit.

If you have a small setup, then l2circuit is likely the less complex
to setup.  As you grow the number of circuits and the complexity of a
mesh, then l2vpn (with its autodiscovery) becomes much more easy to
manage (IMHO).

Rgds,

Guy

2008/7/16 Simon Chen <simonchennj at gmail.com>:
> I have to jump in, since I am also interested :-)
>
> My question is, what do you think the cost/benefit of L2VPN over VPLS?
> It seems that L2VPN is restricted to point-to-point and there is a
> separate vrf (and a routing table) for each link, while VPLS maintains
> a single vrf and routing table. Have you guys thought about using
> VPLS? Or is there any problems with it? Maybe scalability?
>
> thanks.
> -Simon
>
> On Wed, Jul 16, 2008 at 7:55 AM, Farhan Jaffer <bandhani at gmail.com> wrote:
>> Hi Abhi,
>>
>> We are providing connectivity over MPLS cloud for customers on
>> Ethernet via L2 VPN, by separate VLAN IDs.
>>
>> Other type of L2 VPNs are also there & deployed in many n/ws.
>>
>> -FJ
>>
>>
>> On Wed, Jul 16, 2008 at 4:21 PM, Abhi <vyaaghrah-eng at yahoo.com> wrote:
>>> Hi Everybody
>>>
>>> I have been the the JNCIS book and preparing for the exam to i came across the L2 VPNS section. Finding it difficult to identify the real world application of such L2 vpns using FR and ATM.
>>>
>>> Can anyone explain me where these are used and why.
>>>
>>> Thanks
>>>
>>>  regards
>>> abhijeet.c
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