武汉大学计算机学院：《多媒体技术及应用》 Chapter 6 Integrated and Differentiated Services

Chapter 6 Integrated and Differentiated Services 6.0 Introduction o New additions to Internet increasing traffic High volume client/server application Web ● Graphics d Real time voice and video I Need to manage traffic and control congestion ◆ TEFT standards Integrated services Collective service to set of traffic demands in domain Limit demand reserve resources a Differentiated services Classify traffic in groups Different group traffic handled differently

1 Chapter 6 Integrated and Differentiated Services 6.0 Introduction New additions to Internet increasing traffic ◼ High volume client/server application ◼ Web  Graphics ◼ Real time voice and video ◼ Need to manage traffic and control congestion IEFT standards ◼ Integrated services  Collective service to set of traffic demands in domain ◼ Limit demand & reserve resources ◼ Differentiated services  Classify traffic in groups  Different group traffic handled differently

6.1 Integrated Services Architecture(ISA) o IPv4 header fields for precedence and type of service usually ignored O ATM only network designed to support TCP, UDP and real-time traffic t May need new installation Add functionality to routers ce(Qos)within TCP/IF o Need to support Quality of serv Means of requesting Qos

2 6.1 Integrated Services Architecture (ISA) IPv4 header fields for precedence and type of service usually ignored ATM only network designed to support TCP, UDP and real-time traffic ◼ May need new installation Need to support Quality of Service (QoS) within TCP/IP ◼ Add functionality to routers ◼ Means of requesting QoS

6.1.1 Internet traffic 1. Elastic e Can adjust to changes in delay and throughput o E.g. common TCP and UDP application t E-Mail-insensitive to delay changes e FTP-User expect delay proportional to file size Sensitive to changes in throughput SNMP-delay not a problem, except when caused by congestion .Web(http)TelNet-SenSitivEtodelay o Not per packet delay -total elapsed time E. g. web page loading time For small items, delay across internet dominates For large items it is throughput over connection o Need some Qos control to match to demand

3 6.1.1 Internet Traffic 1. Elastic Can adjust to changes in delay and throughput E.g. common TCP and UDP application ◼ E-Mail – insensitive to delay changes ◼ FTP – User expect delay proportional to file size  Sensitive to changes in throughput ◼ SNMP – delay not a problem, except when caused by congestion ◼ Web (HTTP), TELNET – sensitive to delay Not per packet delay – total elapsed time ◼ E.g. web page loading time ◼ For small items, delay across internet dominates ◼ For large items it is throughput over connection Need some QoS control to match to demand

6.1 1 Internet Traffic 2. Inelastic o Does not easily adapt to changes in delay and throughput Real time traffic ◆ Throughput Minimum may be required Delay 中Eg. stock trading o Jitter- Delay variation More jitter requires a bigger buffer E.g. teleconferencing requires reasonable upper bound ◆ Packet loss

4 6.1.1 Internet Traffic 2. Inelastic Does not easily adapt to changes in delay and throughput ◼ Real time traffic Throughput ◼ Minimum may be required Delay ◼ E.g. stock trading Jitter - Delay variation ◼ More jitter requires a bigger buffer ◼ E.g. teleconferencing requires reasonable upper bound Packet loss

3. Inelastic traffic problems o Difficult to meet requirements on network with variable queuing delays and congestion Need preferential treatment o Applications need to state requirements t Ahead of time(preferably)or on the fly Using fields in IP header Resource reservation protocol o Must still support elastic traffic u Deny service requests that leave too few resources to handle elastic traffic demands 5

5 3. Inelastic Traffic Problems Difficult to meet requirements on network with variable queuing delays and congestion Need preferential treatment Applications need to state requirements ◼ Ahead of time (preferably) or on the fly ◼ Using fields in IP header ◼ Resource reservation protocol Must still support elastic traffic ◼ Deny service requests that leave too few resources to handle elastic traffic demands

6.1.2 ISA Approach o Provision of Qos over IP o Sharing available capacity when congested ◆ Router mechanisms Routing Algorithms Select to minimize delay i Packet discard Causes TcP sender to back off and reduce load ◆ Enahnced by IsA 6

6 6.1.2 ISA Approach Provision of QoS over IP Sharing available capacity when congested Router mechanisms ◼ Routing Algorithms  Select to minimize delay ◼ Packet discard  Causes TCP sender to back off and reduce load Enahnced by ISA

Flow o IP packet can be associated with a flow Distinguishable stream of related IP packets t From single user activity Requiring same Qos h E. g. one transport connection or one video stream Unidirectional t Can be more than one recipient ●Ⅳ Multicast Membership of flow identified by source and destination IP address, port numbers, protocol type IPv6 header flow identifier can be used but isnot necessarily equivalent to ISA flow

7 Flow IP packet can be associated with a flow ◼ Distinguishable stream of related IP packets ◼ From single user activity ◼ Requiring same QoS ◼ E.g. one transport connection or one video stream ◼ Unidirectional ◼ Can be more than one recipient  Multicast ◼ Membership of flow identified by source and destination IP address, port numbers, protocol type ◼ IPv6 header flow identifier can be used but isnot necessarily equivalent to ISA flow

ISA Functions ◆ Admission control For Qos, reservation required for new flow Gv RSVP used ◆ Routing algorithn Base decision on Qos parameters ◆ Queuing discipline Take account of different flow requirements ◆ Discard policy Manage congestion Me leet Qos

8 ISA Functions Admission control ◼ For QoS, reservation required for new flow ◼ RSVP used Routing algorithm ◼ Base decision on QoS parameters Queuing discipline ◼ Take account of different flow requirements Discard policy ◼ Manage congestion ◼ Meet QoS

6.1.3 ISA Implementation in Router ◆ Background Functions Routing Reservation Admission Manage Protocol(s) Protocol Control ment Agent Traffic Routing Database Control Database ◆ Forwarding Classifier Packet oos queuing functions Route Scheduler Selection +best-effort queuing

9 6.1.3 ISA Implementation in Router Background Functions Forwarding functions

ISA Components-Background Functions o Reservation Protocol RSVP ◆ Admission control ◆ Management agent Can use agent to modify traffic control database and direct admission control ◆ Routing protocol 10

10 ISA Components – Background Functions Reservation Protocol ◼ RSVP Admission control Management agent ◼ Can use agent to modify traffic control database and direct admission control Routing protocol