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