quality of service issues in multi-service wireless internet links
DESCRIPTION
Quality of Service Issues in Multi-Service Wireless Internet Links. George Xylomenos and George C. Polyzos Department of Informatics Athens University of Economics and Business Athens 10434, Greece [email protected] http://dias.aueb.gr/~gcp/ Tel.: +30-1-8203-650, Fax: +30-1-8203-325. Outline. - PowerPoint PPT PresentationTRANSCRIPT
Quality of Service Issuesin Multi-Service
Wireless Internet Links
George Xylomenos and George C. PolyzosGeorge Xylomenos and George C. Polyzos
Department of InformaticsAthens University of Economics and Business
Athens 10434, Greece
http://dias.aueb.gr/~gcp/Tel.: +30-1-8203-650, Fax: +30-1-8203-325
Outline
Motivation Wireless systems and Internet applications TCP throughput degradation UDP and real-time application issues Proposed approaches
Flexible Link Layer Internet Protocol (FLLIP) Multi-protocol, adaptive, QoS/DS aware solution Goals, architecture, implementation Implicit and explicit service selection
Conclusion
Modern Wireless Systems
Opportunities and issues Digital wireless systems
Cellular, PCS, 3G Wireless LANs LEO/MEO Satellites, LMDS
Mobility Internet protocols: designed for networks that were
Wired: low error rate TCP: loss congestion
Fixed: no mobility, no handoffs Physical layer solutions
Inflexible: one size fits all
Internet Applications and Protocols
Conventional data exchange applications Usually TCP based Error intolerance Delay tolerance Jitter intolerance (TCP)
Interactive and real-time applications Often UDP based (plus RTP) Often multipoint (IP Multicast) Some error tolerance Delay intolerance
Proposed Approaches
Indirect TCP violation of semantics (not end-to-end anymore)
Snoop TCP works well only in the direction towards the mobile
Modifications to TCP Compatibility: usually both ends need to be updated End-to-end retransmissions for a local problem Not multi-protocol: useless for non TCP applications
Conventional link-layer schemes Inflexible: one service only Irrelevant for some protocols/applications
Simulation Experiments
One and two wireless link scenarios Exponential intervals between errors
0.8-5.9% frame loss rates (1 Kbyte frames) TCP: 100 Mbyte file transfer UDP: Voice activated CBR video (1 Mbps) Each test repeated 30 times
PHY
LL
IP
TCP/UDP
Wireless Host A
PHY
LL
IP
Base Station A
10Mbps1ms
PHY
LL
IP
PHY
LL
IP
TCP/UDP
Wireless Host BBase Station B
2Mbps3ms
2Mbps3ms
TCP/UDP
Flexible Link Layer Internet Protocol (FLLIP)
Address the problem at its source Local solution to a local problem
Compatible with Internet protocols & architecture IP and higher layers unchanged
Aware of QoS requirements Implicitly or explicitly
Per stream or class QoS differentiation Fully or mostly reliable
Dynamic adaptation to stream/class mix Variable bandwidth allocation
Dynamic adaptation to channel conditions
FLLIP Architecture
Multiple link layer modules Packet classifier
Protocol, TCP/UDP ports IP ToS, DS field
Per class load measurements Incoming bandwidth allocations
Service class specific processing Isolation between services
Frame scheduler (SCFQ) Enforces incoming bandwidth allocations
Frame SchedulerMAC
Packet Classifier
Service BService A
Protocol Port DS
SCFQ Frame Scheduler
TimeStamper
Sorted Heap
SCFQ Frame Scheduler
Rate Table Virtual Tim
e
Enforces incoming allocations Protects services Encourages efficiency
Self-clocked fair queueing (SCFQ) Efficient, simple, fair One queue per class Heap sort
Service Selection
Implicit QoS specification Assigns applications to services Protocol and TCP/UDP port fields No changes to Internet protocols and applications Immediate applicability
Explicit QoS specification Assigns traffic classes to services QoS provision
Integrated Services, RSVP QoS differentiation
Differentiated Services More flexible
Heuristic Packet Classifier
Implicit QoS specification
TOS
Hashing Function
Lookup Table
Packet Classifier
Protocol
Service Measurements
Source Port (TCP/UDP) Destination Port (TCP/UDP)
IPv4 Packet Mask
Differentiated Services Packet Classifier
Explicit QoS specification Dynamic service selection
Traffic Class
Hashing Function
Lookup Table
Packet Classifier
IPv6 Packet Mask
Service Measurement and Mobility Feedback
Service selection Standard metrics Refinement
Adaptive applications
Mobility
Adaptive Mobility Aware Transport Transport Layer
Network Layer
Standard Measurements and Signals
Hardware/Firmware Physical Layer
Adaptive Mobility Aware Application Application Layer
Application Metrics
Protocol Metrics
Link Layer
Service Metrics
Link Specific Metrics
CBQ RSVP
Vertical Handoffs
Horizontal Handoffs
Mobility Hint Signals
Link Specific Signals
Mobile IP
Conclusions
TCP performance severely impacted by wireless losses TCP is not the only concern
Real-time multimedia over UDP New applications and protocols
Link layer enhancements Fast local recovery Customized to underlying link
Wireless links: natural choice to introduce QoS support Differentiated servicesbecause Bandwidth is scarce and expensive Link performance is variable and unpredictable