Date post: | 07-Apr-2018 |
Category: |
Documents |
Upload: | sampadakathare |
View: | 242 times |
Download: | 0 times |
of 26
8/4/2019 ETX & other routing metrics
1/26
Click to edit Master subtitle style
4/21/12
metricsReferences :-
1. D. De Couto, D. Aguayo, J. Bicket, R. Morris, AHigh Throughput Path Metric for Multi-HopWireless Routing, ACM Mobicom Conference,(September 2003)
2. R. Draves, J. Padhye, B. Zill, Comparisons ofroutingmetrics for static multi-hop wireless networks, in:ACM Annual Conference of the Special Interest
Groupon Data Communication (SIGCOMM), August2004,pp. 133?44
8/4/2019 ETX & other routing metrics
2/26
4/21/12
Link-quality Metrics
Hop count shortest path in terms ofhops
Per-Hop Round trip time round tripdelay seen by unicast probesbetween neighbouring nodes
Per-Hop Packet pair delay delaybetween a pair of back-to-backprobes to a neighbouring node
Expected Transmission count lossrate of broadcast ackets between
8/4/2019 ETX & other routing metrics
3/26
4/21/12
Hop Count
Advantage
Simplicity
Least overhead Disadvantage
Does not take packet loss or bandwidth
into account
8/4/2019 ETX & other routing metrics
4/26
4/21/12
Per-hop RTT
Advantage
Measures queueing delay if node is busy
Measures delay due to channelcontention
Takes into account delay due to lossylinks
Avoid highly loaded or lossy links
Disadvantage
Load-dependent route instability
8/4/2019 ETX & other routing metrics
5/26
4/21/12
Per-hop Packet pair delay
Advantage
Channel contention
Also considers the link bandwidth Disadvantage
Not completely immune to self-
interference
8/4/2019 ETX & other routing metrics
6/26
4/21/12
ETX
Considers the packet loss ratios inboth directions of each wireless link.
Accounts for :- Wide range of link loss ratios
Links with asymmetric loss ratios
Interference between successive hops ofmulti-hop paths
8/4/2019 ETX & other routing metrics
7/26
4/21/12
The metric
ETX = 1/ (Df * Dr)
Df forward delivery ratio
Dr reverse delivery ratio Assumptions
Link-layer retransmissions
Fixed transmit power level Points to consider
Does not reflect how busy a link is
Unfair load-handling leads to incorrect results
8/4/2019 ETX & other routing metrics
8/26
4/21/12
Deliver ratio from X to Y
= (# packets received by Y) / ( # packetssent by X)
Loss ratio = 1 (Delivery ratio)
8/4/2019 ETX & other routing metrics
9/26
4/21/12
Hop Count vs Best path
8/4/2019 ETX & other routing metrics
10/26
4/21/12
ETX vs Hop-countthroughput
8/4/2019 ETX & other routing metrics
11/26
4/21/12
ETX throughput for largepackets
8/4/2019 ETX & other routing metrics
12/26
4/21/12
ETX throughput with hightransmit power
8/4/2019 ETX & other routing metrics
13/26
4/21/12
Accuracy of linkmeasurements
8/4/2019 ETX & other routing metrics
14/26
4/21/12
8/4/2019 ETX & other routing metrics
15/26
4/21/12
Suggested improvements
Predictions of loss ratios for differentpacket sizes
Handling of networks with links thatrun at variety of bit-rates
8/4/2019 ETX & other routing metrics
16/26
4/21/12
Long-lived TCP connections
Throughput comparison
8/4/2019 ETX & other routing metrics
17/26
4/21/12
No. of paths per TCPtransfer
8/4/2019 ETX & other routing metrics
18/26
4/21/12
Median path length
8/4/2019 ETX & other routing metrics
19/26
4/21/12
Impact of path-length on
the throughput
8/4/2019 ETX & other routing metrics
20/26
4/21/12
HOP
8/4/2019 ETX & other routing metrics
21/26
4/21/12
ETX
8/4/2019 ETX & other routing metrics
22/26
4/21/12
RTT
8/4/2019 ETX & other routing metrics
23/26
4/21/12
PktPair
8/4/2019 ETX & other routing metrics
24/26
4/21/12
Variability of TCP throughput
8/4/2019 ETX & other routing metrics
25/26
4/21/12
8/4/2019 ETX & other routing metrics
26/26
4/21/12
Conclusion
ETX fairs very well with stationarynodes in a number of aspects ascompared to other link-quality
metrics RTT & PktPair perform poorly
because they are load-sensitive &
hence subject to self-interference