The MPLS-OPS Archive

["Piotr Marecki" <p.marecki@swiat.pl>]

>----- Original Message ----- 
>From: "Puddinhead Wilson" <puddinghead_wilson007@yahoo.co.uk>
>To: <mpls-ops@mplsrc.com>
>Sent: Saturday, January 08, 2005 5:59 AM
>Subject: RE: [MPLS-OPS]: Re: Layer 2 MPLS VPN
>

>
>
>Some questions:
>> Some thoughts on this thread -
>>
>> LDP signaling provides more flexibility for VPLS
>> because it allows different characteristic setting
>> per PW such as:
>> .
>> -1. QoS setting - e.g., different PWs can have
>> different reserved BW and if needed the BW can be
>> adjusted dynamically (based on time of day). Also
>> congestion management requires feedback for a PtP
>> link
>>
>
>LDP? CRLDP? or RSVP-TE? there is no qos term in LDP I
>have seen.

There are two diffrent ways of signalling VPLS - with control plane served
by LDP (
draft-ietf-l2vpn-vpls-ldp-05.txt ) or BGP
(draft-ietf-l2vpn-vpls-bgp-03.txt).Both documents
describe how to distribute and set-up PWE's between PE's without many
constraints on underlying
transport technology.That's it , transport tunnels may be IP based ( GRE )
or MPLS LSP's ( LDP
or RSVP-TE). You are talking about tunnel set-up in response to post  about
signalling pros and cons.

>>  3. OAM: It is important to be able to check the
>> health status of each PW separately because one PW
>> may affect the status of the whole set (Emulated
>> VLAN)
>
>In the implementation of LDP I have seen for L2VPNs,
>LDP just carries the end point identifiers, more like
>map this vlan to this label, map this  port to this
>"group" and each PE then assigns the group a label.
>RSVP-TE is still the preferred way to setup LSPs to
>the PE loopbacks.

Again , LDP as well as BGP based VPLS can have RSVP tunnels - it is
irrelevant.What is important here
is fact that in LDP based solution works through setting up targeted
sessions and exchanging FEC elements
carrying information about VC labels.This procedure is inherently
point-to-point which could help ( as some
ppls argue ) to have better ( fine grained) control over PW ( since specific
attributes to one PW can be exchanged in p2p fashion).
In contrast , in BGP based solution PE "broadcasts" blocks of usable label
for CE link ( label offset , base and range ) from which other
PE's  chose appropriate label. As you can see , in BGP solution there is no
room for signalling PW specific attributes - information
is shared by all "interested" PE's.


>>
>> 4. Data-plane failure: there can be scenarios where
>> an operator may want to reset a PW (bring down and
>> up). In such cases, a new label is desired to be
>> assigned (in case there is an issue with the label
>> itself). This is inherently done with LDP protocol;
>> whereas with BGP protocol and label-block scheme the
>> same label gets assigned over and over again.
>
>I dont know about the "label block" schemes, I never
>did really understand it. could someone clarify it?

It refers to BGP based solution - all is explained in draft :)


best regards ,

Piotr Marecki
Netia S.A

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