Providing DiffServ Quality of Service in b Networks

Transcription

1 Laboratoire LSR Logiciels Systèmes Réseaux Software, Systems, Networks Providing DiffServ Quality of Service in b Networks Andrzej Duda LSR-IMAG Joint work with J. Antonio García-Macías, Franck Rousseau, Gilles Berger-Sabbatel, Leyla Toumi

2 Overview Introduction DiffServ QoS mechanisms QoS over WLAN Performance measurements Conclusions and perspectives 2

3 End-to-end DiffServ architecture Mobile Hosts PHB Access Router Host Access Network Edge Router PHB Core Routers SLA PHB Service Level Agreement Edge Router Access Router Mobile Hosts 3

4 DiffServ service classes Two types of applications interactive (games, interactive distributed simulations, VoIP, device control) delay, jitter elastic (data transfer) sustained throughput Traffic classes EF (Expedited Forwarding) short delay, small jitter AF (Assured Forwarding) minimal sustained throughput BE (Best Effort) 4

5 DiffServ - Edge router Classification, metering, marking 5

6 DiffServ - Core router Queue management and scheduling EF: high priority AF, BE: WFQ - Weighted Fair Queueing Traffic shaping 6

7 DiffServ QoS over b: wireless LAN nominal bandwidth of 11 Mb/s ISM band at 2.4 GHz shared radio channel PCF access method not implemented DCF access method - CSMA/CA similar to Ethernet, important overhead channel access probability equal for all hosts 7

8 802.11b performance 8

9 QoS over b WLAN DCF access method - CSMA/CA proportion of usable bandwidth depends on the number of hosts Fact 1: to support QoS, we need to limit the number of hosts in a cell 9

10 QoS over b WLAN Channel quality degrades with the distance deferral behavior: degrade to 5.5, 2, or 1 Mb/s nominal bandwidth measured bandwidth 11 Mb/s, 11 Mb/s 5 Mb/s 11 Mb/s, 1 Mb/s 0.84 Mb/s Fact 2: to support QoS, we need to limit the geographical span of a cell (accept only hosts that transmit at 11 Mb/s) 10

11 QoS over b WLAN What kind of QoS over b WLAN? Statistical differentiation using DiffServ priority and WFQ scheduling, traffic shaping Fact 3: to support QoS, we need to limit the rate of traffic sources 11

12 Hierarchial QoS management Edge Router QOS_POLICY Access Router Access Router DiffServ mechanisms 2.QOS_CONFIG wireless channel wireless channel 3.QOS_CONFIG DiffServ mechanisms 1.QOS_REQUEST 12

13 Local QoS management In-band signaling protocol QOS_REQUEST in each IPv6 packet Flow Label or header extension 64 Kb/s increments QOS_REQUEST in hand-off request QOS_CONFIG modifes parameters of DiffServ mechanisms maximum EF rate maximum AF/BE rate AF weight for WFQ 13

14 Local QoS management Bandwidth allocation x EF = Σ x i,ef r EF r(m) C x AF = Σ x i,af r AF r(m) C x BE = Σ x i,be r BE r(m) C r EF + r AF + r BE = 1 - δ r(m) C: usable bandwidth if m hosts in a cell δ: safety margin 14

15 Global QoS management Out-of-band signaling protocol QOS_POLICY to define QoS policy of an Access Router - reserve bandwidth in all cells in the cells on a given path in the cells on a frequent path in the neighbor cells in one cell 15

16 Measurement set-up Access Router RTT test server EF class, UDP data netperf server BE class, TCP ACKs wireless channel RTT test client EF class, UDP data netperf client BE class, TCP data Mobile Host 16

17 QoS performance Experiment 1 (QoS disabled) mobile host with 2 sources UDP, EF class 300 Kb/s TCP, BE class greedy, tries to gain as much as possible no QoS, FIFO queueing 17

18 Throughput, no QoS 18

19 Delay (RTT), no QoS 19

20 QoS performance Experiment 2 (QoS enabled) mobile host with 2 sources UDP, EF class 300 Kb/s TCP, BE class greedy, limited to 2.4 Mb/s DiffServ scheduling, priority to EF 20

21 Throughtput, QoS enabled 21

22 Delay (RTT), QoS enabled 22

23 Measurement set-up Access Router RTT test server EF class, UDP data netperf server BE class, TCP ACKs wireless channel RTT test client EF class, UDP data netperf client BE class, TCP data Mobile Host Mobile Host 23

24 QoS performance Experiment 3 (QoS enabled) 2 mobile hosts with 1 source UDP, EF class 300 Kb/s TCP, BE class greedy, limited to 2.4 Mb/s DiffServ scheduling, priority to EF 24

25 Throughtput, QoS enabled 25

26 Delay (RTT), QoS enabled 26

27 Conclusion Extending DiffServ to wireless LANs basis for Wireless Mobile Internet - efficient hot-spots First encouraging results DiffServ mechanisms for providing QoS over b statistical QoS for priority flows How to extend to ad-hoc networks? election of a bandwidth controller that manages resources in its zone 27

28 Current and future work Need more experiments and measurements statistical QoS good enough for time critical flows (VoIP, MP3 and video streaming)? efficiency of dynamic QoS management - reaction to changing situation Consider other QoS models similar to Asymmetric Best Effort (ABE) two classes: short delay, large bandwidth 28