A Differentiated Services Architecture for the Internet.ppt
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1、A Differentiated Services Architecture for the Internet,References- K. Nichols, V. Jacobson, L. Zhang- D. Clark, J. WroclawskiPresented by Liping Zhang,Overview,Introduction Two different service types: implementation and problems Two-bit differentiated services architecture Problems with end-end ba
2、ndwidth allocation based on level of marked traffic Discussion,Introduction,Why do we need differentiated services?Different usersDifferent applications Service allocation For example, one goal of assured service is to allocate the bandwidth of the Internet to different users in a controlled way dur
3、ing periods of congestion,How to describe a service,What is provided to the customer E.g., 1 Mbps, continuously available To where is this service provided A single destination A group All nodes on local provider Everywhere Level of assurance provided to service What level of performance uncertainty
4、 can user tolerate,Two distinct service types,Assured service D. Clark Premium service V. Jacobson,Assured service,Provide different levels of best-effort service at times of network congestion Expected capacity “In” packets unlikely to be dropped “Out” packets - no assurance Queuing Best effort,Mec
5、hanism for assured service,Host,First-hop,Counter,Counter,Out- and in- dropper,RIO scheme, packetsare treated preferentially,Marking packets according to the service profile,RIO algorithm,RED - Random Early Detection Packets dropped with low but increasing probability as queue grows; instead of wait
6、ing until it is full and dropping all new packets RIO Run two RED algorithms for “in” and “out” with different dropping frequencies,Premium service,Fundamentally different Internet best effort service - high priority traffic has its own queue in routers Shaped, hard-limited to provisioned peak rate
7、No bursts are injected into net Virtual wire, available whenever needed Regular flow pattern, no queuing Shared, with best-effort,Mechanism for premium service,Host,First-hop,Intra-network,Router,H-Q: premium, no droppingL-Q: best effort, dropping on congestion,Two-bit differentiated services archit
8、ecture,Deploying both services More bits available in IP header, why not both Forwarding path mechanisms Leaf routers Input interface: a traffic profile Output interface: two queues (HQ, LQ) Intermediate routers Only have forwarding function Border routers A Profile Meter at the input interface,Traf
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