A Differentiated Services Architecture for the Internet.ppt

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

9、fic flow from end-host to ISP,Host,First-hop Router,Internal Router,Border Router,Border Router,ISP,Company A,1,2,3,Forwarding path primitives,General classifier In leaf routers, transport-level signature matching Bit-pattern classifier Performs a two-way decision based on bit-pattern Bit setter A-

10、and P-bits must be set or cleared in several places Priority queues Shaping token bucket At the leaf router for Premium traffic Policing token bucket At border router, for both P and A services,Block diagram of leaf router input functionality,Packet Classifier,ClearA&Pbits,Forwarding Engine,Marker N

11、,Marker 1,Arriving packet,Best Effort,Flow1,Flow N,Markers to implement the two different services,Wait for token,Test if token,Set A bit,Set P bit,Packet Input,Packet Input,Y,N,Router output interface for two-bit architecture,Low-priority,High-priority,P-bit set?,If A-bit set? Inc a_cnt,RIO queue m

12、anagement,If A-bit set?dec a_cnt,No,Border router input interface Profile Meters,Is packetmarked ?,Token available ?,Clear A bit,Token Available,Drop Packet,Forwarding Engine,N,N,Y,Y,P set,A set,Not marked,Passing configuration information,Request to the leaf router Average rate, burst, service type

13、 (P or A) Ways of passing the message RSVP, SNMP, network administrator Authenticating the sender,Architectural framework for marked traffic allocation,Preconfiguring of usage profiles is practical Paying for level of service that is always available Allocation follows organizational hierarchies Eac

14、h organization must be responsible for its DM Only bilateral agreements work,Bandwidth Brokers (BB),Roles Allocating and controlling bandwidth shares Responsibilities Parcel out a regions marked traffic allocation and set up the leaf routers within the local domain Managing messages sent across boun

15、daries to adjacent region BBs,Examples,A statically configured example with no BB message exchanged A statically configured example with BB messages exchanged Dynamic allocation and additional mechanism,RSVP and BBs,Existing bilateral relations between BBs of adjacent trust regions are necessary for

16、 resource allocation A few bits in the packet header are used to mark the service class RSVP resource setup: hop-by-hop Use RSVP between two adjacent ISPs (BB1/BR1 and BB2/BR2),Discussion,Extensibility of the current 2-bit architecture Service allocation for multicast Who should request the service Sender or receiver Deployment issues Security issues,2-bit differentiated services architecture,Providing Controlled-Load and Guaranteed service P service for C-L serviceA constrained case of C-L service P service for G service The service model of P service fits G service model,