Tag Switching Architecture Overview

Qingfeng Zhuge

Fangxia Li

Xin Jiang

Topic Organization

• Part I Tag Switching Architecture

-- Qingfeng Zhuge

• Part II Tag Switching with Multicast, QoS and Flexible Routing

-- Xin Jiang

• Part III Tag Switching Application (ATM)

-- Fangxia Li

Switching

• Data packet forwarding

• Resource competition, allocation and release along the data flow path

Why Tag Switching

• Higher forwarding performance

• Scaling properties of internet routing system

• Flexible traffic control

• Support evolution to accommodate new and emerging requirement

Tag Switch– A Multi-Protocol Solution

• Combine network-layer routing with label-swapping forwarding

• Supply flexibility and rich functionality by routing

• Supply simplicity and high performance by label-swapping forwarding

• A multi-layer integration solution with routers, switches as peer network devices

Tag Switching Architecture

Two components:forwarding and control

• Forwarding component

-- forward packets based only on tags

-- no redundant network-layer header analysis

Cont.

• Control component

-- a set of software modules used to distribute and maintain the tag information inside a tagged network domain

-- different module support different routing protocol

Forwarding component-- a table look-up structure

• FIB – a condensed form of routing table, reside in cache

• TIB – tags allocated locally for each entry in FIB

• TFIB – constructed by both FIB and TIB to implement tag binding

Forwarding component mechanism

• Table look-up

• Replace the incoming packet’s tag by outgoing tag and interface information

• Tag encapsulation

Advantages of forwarding component

• Compared to conventional longest match forwarding

• Independent of forwarding granularity

• Independent of network-layer protocols

• A TFIB per switch or per interface or mix of both

Control component

• Create tags

• Complete the binding between a tag and network-layer routes

• Distribute the tag binding information among tag switches

Control component implementation

• Piggy-backing an existing control protocol

• By special protocol, such as TDP in tag switching

Advantages of control component

• Simplify the overall system behavior

• Reduce traffic load

• Support multiple network-layer routing protocol

• Support variety of forwarding granularities: unicast, multicast, flexible routing, QoS routing, RSVP session

Tag distribution mechanisms

• Downstream

• Downstream on demand

• Upstream

Dependencies and constraints

• FIB must be get from routing protocol, such as OSPF, BGP

• Must support conventional network-layer routing protocol on edge and maybe also some fraction of the tagged network.

• Must implement a mechanism for tag distribution

Observation

• Tags less than routes in FIB

• Tag allocation is driven by control traffic rather and data traffic

• Need header analysis and flow classification only on tagged network edge

• Decrease the overall complexity and traffic load in the network