Title: LDP autodiscovery Slide 1
1IETF63 ParisL2VPN WG LDP Autodiscovery
LDP-based Autodiscoverydraft-stein-ldp-auto-00.t
xtjoint work with Simon Delord
2Access Network Architecture
MPLS-enabled Access Network
Core Network
there may also be combined multiservice access
nodes
3Access Network Characteristics
ACCESS NETWORK simple tree (or ring)
topology (may be redundant links) limited BW
limited computational power 1000s of access
nodes no BGP, may not be IGP LDP for access LSP
setup
CORE NETWORK rich topology huge BW strong
computational power smaller number of routers BGP
LDP
4MS-VPLS
access network
core B
access network
core A
access network
core C
access network
MS-VPLS supported by MS-PWs
PE not in Vset
PE in Vset
PE joining Vset
5Service Discovery
- network elements and links (in both access and
core networks) - are relatively static (perhaps add or change 1 or
2 elements per day) - hence network discovery is not an operational
burden - manual provisioning of LDP sessions between PEs
is reasonable - services are by their nature dynamic
- (perhaps add several users per day to each set of
services) - manual provisioning of services is a logistical
nightmare - for scalability need service discovery
- when BGP is available (i.e. in core network)
- it can be used for autodiscovery of all types
- when only LDP is available
- need to have an LDP-based technique
6Autodiscovery possibilities
- central server holding Vset (single point of
failure) - each PE in Vset periodically advertises the fact
(very chatty) - PW wanting to join Vset sends label mapping to
all PEs - (thousands of un-necessary mapping messages and
perhaps bindings) - PE wanting to join Vset inquires and initiates PW
setup - (w/o central server needs to send inquiry
messages and collect responses - and then one PE needs to initiate setup of
many MS-PWs) - PE wanting to join Vset announces (join messages)
- and Vset members initiate PW setup
7JOIN Message
core B
core A
core C
NB SPE used for JOIN message is not necessarily
used by PW
8PW Setup
core B
core A
core C
PW setup uses whatever MS-PW mechanism PWE3
decides upon