Half-Duplex Multicast Distribution Trees(draft-brockners-ldp-half-duplex-mp2mp-00.txt)

IETF 68, March 2007

Frank Brockners (fbrockne@cisco.com)

IJsbrand Wijnands (ice@cisco.com)

Ali Sajassi (sajassi@cisco.com)

Problem Statement/Motivation

“Client”

“Client”

“Client”

“Server”

“Server”

C1

C2

C3

S1

S2

• Some deployment scenarios (e.g. residential wholesale) require transparent and efficient multicast transport from a few sources to many receivers

• Set of Leaf-LSRs is devided into two non-overlapping sets– Servers– Clients

• While “Servers” should be able to communicate to all “Clients” and to each other, “Clients” should not be able to communicate with each other but only to “Servers”

“Client”

“Client”

“Client”

“Server”

“Server”

C1

C2

C3

S1

S2

Data sent by a Server reaches all other Servers and Clients.

Data sent by a Client reaches all Servers but not the other clients.

MPLS

MPLS

XX

Solution Objectives

• Simple Configuration and Operation– Provisioning of a new leaf LSR should not require manual

configuration changes on any LSR but on the leaf LSR– Automatic setup of the forwarding behavior between client and

servers (no manual configuration requirements on non-leaf LSRs)• Scalable Implementation

– Limit the amount of state

Classic Solution Approach

• Combine P2MP LSPs and MP2P LSPs– One P2MP LSP per Server (rooted at Server)

• Server to Clients and other Servers communication– One MP2P LSP per Server

• Client to Server communication• Each client connects to N x P2MP LSPs and N x MP2P

LSPs (with N being the number of Servers)• Requires Send/Receive Operations across multiple LSPs

for a single Service Instance (due to combination of multiple LSPs)

• Addition of a Server requires configuration changes on all other Clients and Servers

Half-Duplex Multipoint Distribution Trees

• Leverage draft-ietf-mpls-ldp-p2mp-02.txt– Define extensions to draft-ietf-mpls-ldp-p2mp-02.txt while

keeping the “spirit” (i.e. nomenclature, basic principles)– HD-MP2MP as a new “deployment example”

• Combine Two LSPs (i.e. Combine two Trees)– “Client Tree”: All Clients to Servers– “Server Tree”: All Servers to Clients and Servers

• Leverage P2MP FEC – 4 new FEC types– Similar to MP2MP – but this time we need to be able to

differentiate the origin of the traffic (Server or Client)• Client-Upstream, Client Downstream• Server-Upsteam, Server Downstream

Tree Construction Overview

• Tree construction principles similar to draft-ietf-mpls-ldp-p2mp-02.txt for MP2MP– HD-MP2MP is build as a collection of

label states– Receiver Driven – towards Root LSR – Trees are constructed concurrently

(upstream label map triggers downstream label map)

– Transit and Root LSRs merge upstream and downstream state to optimized forwarding as well as half-duplex behavior

– “Opaque Value” only interpreted by leaf LSRs

Z

U

R

S3 C2

R

C1S1

S2

Next Steps

• Authors appreciate feedback from the WG

• Add example to the draft to help readability