A REDUCED SERVICE-SET ARCHITECTURE FOR THE INTERNET

Transcription

1 A REDUCED SERVICE-SET ARCHITECTURE FOR THE INTERNET Gunnar Karlsson KTH Teleinformatics Kista, Sweden

2 Contents Background Network quality of service Background for our work A reduced service-set architecture Simplified guaranteed service Controlled-load service Summary September 4, 2000 KTH Teleinformatics 2

3 Network quality of service Internet quality today Varies with the traffic load in the network No guarantees, only a best effort Congestion (overload) occurs New applications require quality of service guarantees IP telephony Video conference Playback of music and video September 4, 2000 KTH Teleinformatics 3

4 Degradations Delay caused by propagation processing buffering Information (packet) loss caused by full buffers addressing errors September 4, 2000 KTH Teleinformatics 4

5 Human requirements Quality requirements for humans One-way delays below 150 ms unnoticeable for conversations Video and audio not more than 80 ms apart for lip synch Information loss difficult to quantify Visibility or audibility of loss Quality of source material Cost of network service September 4, 2000 KTH Teleinformatics 5

6 Background for our work Moving functionality from network towards hosts The original Internet philosophy Network forwards packets, hosts responsible for reliability No connection states in the network At most aggregate reservations kept in routers Quality by combination of error and traffic controls One quality level per service class Augmented when needed by error-control coding Packet-scale buffering Reduces delay and jitter Packet loss is the main degradation September 4, 2000 KTH Teleinformatics 6

7 The reduced service set Service architecture with three classes Simplified guaranteed service with lightweight signaling Controlled-load with admission control based on end-to-end measurements Best effort with separation of batch and stream data Scheduling Non-work conserving for GS and CLS Work conserving for BE September 4, 2000 KTH Teleinformatics 7

8 Simplified guaranteed service Fixed-rate bound and reshaping gives additive reservation state No change in delay bounds and Less buffering compared to token-bucket descriptor (RFC 2212) Connection states in access router; aggregates in interior routers September 4, 2000 KTH Teleinformatics 8

9 Service-specific signaling Add and subtract rates to reserve and rescind capacity Reservation state held in shared variable Deterministic quality guarantees No loss of packets Guaranteed maximum delay September 4, 2000 KTH Teleinformatics 9

10 Controlled-load service Prevent congestion by means of admission control Trade packet loss for call blocking: still best effort Restricted peak rate to ensure good statistical multiplexing Quality is improved by means of errorcontrol coding September 4, 2000 KTH Teleinformatics 10

11 Admission control Based on probes from sender to receiver (or exit router) No need for measurements and decision making in interior routers No need for network signaling No reservation state kept in routers September 4, 2000 KTH Teleinformatics 11

12 Configuration Fixed capacity partition for the service Needed on all network links Unused capacity available to best-effort traffics Two service priorities within partition HI LO C cls C link C cls Available to other traffics Used by CLS traffic September 4, 2000 KTH Teleinformatics 12

13 The measurement procedure Constantrate probe S Probe sent at low priority Admission decision R Measurement Data sent at high priority September 4, 2000 KTH Teleinformatics 13

14 CLS performance Constant rate probes at 5 and 10 Mb/s One-packet buffer per node Ongoing sessions Packet-scale buffering only On-off Markov source with average rate 1.8 Mb/s Average on and off periods 7.2 ms (45 packets) and 12.8 ms, respectively for 5 Mb/s peak rate 3.6 ms and 16.4 ms, respectively for 10 Mb/s peak rate September 4, 2000 KTH Teleinformatics 14

15 45 Mb/s link capacity, probe and session loss September 4, 2000 KTH Teleinformatics 15

16 Relation between probe loss and session loss September 4, 2000 KTH Teleinformatics 16

17 Acceptance probability 150 Mb/s link, 5 Mb/s peak rate, 100 byte packets September 4, 2000 KTH Teleinformatics 17

18 Summary Simplified guaranteed service with lightweight signaling Additive reservation state Controlled-load service without signaling QoS provided jointly by admission and error controls Measurement-based admission control administered from network edges Best-effort September 4, 2000 KTH Teleinformatics 18