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