High Speed Networks and High Speed Networks and InternetsInternets:: Multimedia Multimedia

Transportation and Quality of Transportation and Quality of ServiceService

Meejeong Lee

ObjectivesObjectivesWhat is required to transport

– Large volumes of traffic– With different QoS requirements– Over networks operating at very high data ra

tes

The Need for Speed and QoSThe Need for Speed and QoS

Emergence of high-speed LANs– Explosive growth of processing power of

personal computers– Network computing– Examples of requirements that calls for HSL

Centralized server farms Power workgroups High-speed local backbone

– Examples of HSL: Fast Ethernet, Gigabit Ethernet, High speed wireless LAN, ATM LAN

The Need for Speed and QoSThe Need for Speed and QoS

Corporate Wide Area Networking needs– Intranet computing among dispersed

employees– Internet access with graphical

interfaces– Huge volumes of data with

unpredictable traffic patterns

The Need for Speed and QoSThe Need for Speed and QoS

Digital electronics– Digital Video Disk (DVD)

Huge storage capacity and vivid quality PC games and educational software with more

video New crest of traffic over the Internet and intranets

as the material is incorporated into web sites

– Digital still camera Convenience for use in networks Dramatic growth in the amount of on-line image

and video traffic

The Need for Speed and QoSThe Need for Speed and QoS

QoS on the Internet– Internet and IP were designed to provide be

st-effort delivery service– With tremendous increase in traffic volume,

and the introduction of new real-time, multimedia, and multicasting application, the traditional Internet services are woefully inadequately

The Need for Speed and QoSThe Need for Speed and QoS

QoS requirements of Internet applications– Elastic traffic

Email, file transfer, network management, interactive applications(rlogin, web access)

– Inelastic traffic Voice and video Throughput, delay, delay variance, packet loss

– Figure 0

Figure 0. A Comparison of Application Delay Sensitivity and Criticality in an Enterprise [ CROL00]

QoS in IP NetworksQoS in IP Networks

Design requirements– Control congestion– Provide low delay– Provide high throughput– Support QoS– Provide fair service

QoS in IP NetworksQoS in IP Networks Two complementary architectures

– Integrated services– Differentiated services

Protocols for QoS support– RSVP: support the IS architecture by enabling the r

eservation of resources in a datagram environment– MPLS: framework for labeling traffic and routing ba

sed on traffic flows– RTP: transport level support for real-time applicatio

n

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

Tools for controlling congestion in IP-based internet– Routing algorithm– Packet discard

ISA approaches– Admission control– Routing algorithm– Queueing discipline– Discard policy

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

ISA components– Background functions

Reservation protocol Admission control Management agent Routing protocol

– Main task: forwarding of packets Classifier and route selection Packet scheduler

– Figure1

Figure 1. Integrated Services Architecture Implemented in Router

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

ISA services– Guaranteed

Assured capacity level or data rate Specified upper bound on the queueing delay through the netw

ork No queueing losses

– Controlled load Approximates the behavior with the best-effort service under u

nloaded conditions No specified upper bound on the queueing delay, but suppose

d to impose almost no queueing delay Almost no queueing loss

– Best effort

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

Traffic description: Tspec

Figure 2. Token Bucket Scheme

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

Queueing discipline– FIFO

No special treatment for higher priority or delay sensitivity

Inefficiency when smaller packets are queued behind a long packet

Greediness is not punished– Figure 3

Figure 3. FIFO and Fair Queuing

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

Queueing discipline– Fair Queueing– Processor Sharing– Bit-Round Fair Queueing– Generalized Processor Sharing– Weighted Fair Queueing

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

Discard policy– Random Early Detection (RED) design goals

Congestion avoidance Global synchronization avoidance Avoidance of bias against bursty traffic

Integrated Services Integrated Services Architecture (ISA)Architecture (ISA)

RED algorithm (Figure 4)

if avg < THmin

queue packetelse if Thmin <= avg <THmax

Calculate probability Pa

with probability Pa

discard packet else with probability 1-Pa

queue packetelse if avg >= THmax

discard packet

Figure 4. RED Buffer

Differentiated Services Differentiated Services (DS)(DS)

DS configuration and operation:

Figure 5. DS Domains

Differentiated Services Differentiated Services (DS)(DS)

Per-Hop Behavior (PHB)– Expedited Forwarding PHB: appears

to the end points as a point-to-point connection or leased line

– Assured Forwarding PHB: a service superior to best-effort