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Integrated-Service versus Differentiated-Service Networks. 許蒼嶺 教授 國立中山大學 電機工程學系. Department of Electrical Engineering Computer Networking Lab National Sun Yat-Sen University Prof. Tsang-Ling Sheu. Outline. Integrated Services Traffic Model RSVP Differentiated Services
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Integrated-Service versus Differentiated-Service Networks 許蒼嶺 教授 國立中山大學 電機工程學系 Department of Electrical Engineering Computer Networking Lab National Sun Yat-Sen UniversityProf. Tsang-Ling Sheu
Outline • Integrated Services • Traffic Model • RSVP • Differentiated Services • Architectures • Traffic Classes and DSCP • Queuing Disciplines • Survey of Papers
Quality of Services • Over-Provisioning • Priority Queuing • Per-Flow : Integrated Service, Intserv [RFC1633] • Per-Class : Differentiated Services, Diffserv [RFC2475]
Integrated Services • Resource ReSerVation Protocol • Controlled-Load Service - RFC 2212 • Guaranteed Service - RFC 2211
Integrated Services • Modules in Integrated-Service Traffic Model • Admission Control • Determine if QoS Request Should be Granted • Traffic Classifier • Map Packets/Flows to Service Classes • Packet Scheduler • Forward Packets Based on Service Classes
IntServ Traffic Model Router Host RSVP Reservation Routing Protocols RSVP Reservation Admission Control Classifier Packet Scheduler Classifier Packet Scheduler IP Data Flow
Integrated Services • Guaranteed Services • For Delivering Real-Time Applications • Provides an Assured Level Services • Bandwidth • End-to-End Delay Bound • No Queuing Loss • Controlled-Load Services • Service Equivalent to Best-Effort Flows
RSVP Issues • RSVP only Suits for Long-Duration Applications • Too Expensive for WWW Transfers • RSVP only Suits for Small-Size Networks • Leads to too many Link States and Signaling Traffic • RSVP Requires Application Supports • Knowledge of Application QoS • QoS API
DiffServ Issues • Scaling • Pushes Complex Forwarding Operations to Boundary Routers • Control and management • Rely on New Configuration or Management Protocols • Bandwidth Broker (BB) • Suits for a Small-Size Network • Distributed BB • Billing and Accounting • Based on Negotiated Traffic Profiles
Management and Billing Priority Levels IP Addresses TCP Ports Video Conf. FTP Telnet WWW SMTP BBS SNMP Time of Day
Bandwidth Broker BandwidthBroker Interior Routers Packets Out Packets In Boundary Router Boundary Router
Diffserv – PHB Group • DF (Default Forwarding, Best-Effort) • DSCP : 000000 • EF (Expedited Forwarding) • DSCP : 101110 • AF (Assured Forwarding) • DSCP : 4 Class, 3 Drop Precedence
First-Come-First-Serve (FCFS) • Simplest Queue • Packet will be dropped when queue is full • Rear or front dropping
Priority Queue (PQ) • Packets with higher-priority will always be sent first • Starvation in lower-priority queue
Round-Robin (RR) 7 4 1 8 5 2 6 9 3
Weighted Round Robin (WRR)M. Katevenis, IEEE Journal on Selected Areas in Communications, 1991 • General case of Round Robin • More weight with higher-priority class
Weighted Fair Queue (WFQ)A. Demers, SIGCOMM’ 89 • Provide fairness in variable-length IP packets • Packets sent by the order of estimated completion time
Deficit Round Robin (DRR)M. Shreedhar, IEEE/ACM Transactions on Networking, 1996 • WFQ is not easy to be implemented, O(logP) • DRR • Round Robin fashion, O(1) • Use Quantum instead of Weight • Use Deficit Counter to provide fairness
Token Bucket (TB) • Leaky Bucket:Traffic Shaping • Token Bucket:Shaping with more burst tolerance
Random Early Detection (RED) Minimum Threshold (Minth) Maximum Threshold (Maxth) Average Queue Size (avg) Marking Probability (Pmax)
Random Early Detection(RED)S. Floyd, IEEE/ACM Transactions on Networking, 1993 • Random drop or mark packets before buffer overflow
RED with In/Out Bit (RIO)D. D. Clark, IEEE/ACM Transactions on Networking, 1998 • Different marking probability for In/Out packet
RED with In/Out bit (RIO) In Packet : Minimum Threshold (Minth_in) Maximum Threshold (Maxth_in) Average Queue Size (avg_in) Marking Probability (Pmax_in) Out Packet : Minimum Threshold (Minth_out) Maximum Threshold (Maxth_out) Average Queue Size (avg_total) Marking Probability (Pmax_out)
Proportional DiffServC. Dovrolis, IEEE Network, 1999 • Absolute DiffServ (WRR, DRR) • Use static resource reservation instead of dynamic resource reservation • Proportional DiffServ (WTP, DWFQ, PLQ) • Provide QoS differentiation between traffic classes • Predictable: • High-priority class must have better or the same QoS as low- priority class • Controllable • Provide a time tuning knob to adjust the differentiation between classes
Waiting Time Priority (WTP)C. Dovrolis, IEEE/ACM Transactions on Networking, 2000 • General case of Time-Dependent Priorities [L. Kleinrock, Queuing Systems, 1976] • Delay Proportional Parameter δi • Active(Busy) Set B(t) • Normalized Head Waiting Time • Packet with the most waiting time will be sent first
Probabilistic Longest Queue (PLQ)Jung-Shian Li, GLOBECOMM’01
PQ with EF Token Bucket • EF PHB has the highest priority • Use a Token Bucket to limit EF maximum bit rate
Priority Queue with Quantum (PQWQ) • Provide fairness between PHBs • Use counters for all PHBs in order to limit bytes sent in one round • Quantum values will be added to counters after one round • Provide low delay to EF PHB • EF PHB has the highest priority • If counter is enough, higher priority PHB will be sent first in one round • Avoid the delay by Round Robin fashion
Diffserv Potential Problems • Ineffectual End-to-End QoS guarantee • Unfair bandwidth sharing • Packets only dropped at congested links when congestion
Various Diffserv Architectures • Packet-Marking Engine (PME)[Wu-Chang Feng, 1999] • Feedback Controlled Diffserv[Hungkei Chow, 1999] • Diffserv in MPLS[Y. Bernt, 2000] • RSVP in Diffserv[I. Andrikopoulos, 1999]
Packet-Marking Engine (PME) • New Packet-Marking Engine • TCP-like algorithm and Modified TCP congestion control • Dynamic Marking probability (mprob) • Adv : • TCP-friendly algorithms • Adative packet marking to improve end-to-end throughput • Traffic fairness • Disadv : • 1-bit priority for packet marking • Support TCP traffic only • Update network interface in host/nodes
Feedback Controlled Diffserv • New FC-DS nodes • Probe/Report control packet • Adaptvie QoS • Adv : • Current network status report • Adative traffic conditioning • Fair network resources allocation • Disadv : • Upgrade DS nodes to support FC scheme • More processing complexity in FC-DS ingress nodes • Extra processing of probe control packets
PHB DSCP Field SAI Field Description EF 101110 0xxxxxx Increase weight for WRR EF 101110 1xxxxxx Decrease weight for WRR AF Old DSCP New DSCP Change to new DSCP BE 000000 0xxxxxx Increase weight for WRR BE 000000 1xxxxxx Decrease weight for WRR 6-Bit SAI Field
CU value Packet Type 00 Normal Data Packet 10 Normal Control Packet 01 Congested Data Packet 11 Congested Control Packet 2-Bit CU Field
Conclusions • Integrated Services • Per flow QoS • RSVP • DiffServ Architectures • Per Class QoS • Traffic Classification • Queuing and Scheduling • WRR, WFQ, DRR, Token Bucket, Proportional Delay, etc. • MPLS and DiffServ