1. ATCP : TCP for Mobile Ad Hoc Networks
11/10/2018
ATCP : TCP for Mobile Ad Hoc Networks
By Jian Liu and Suresh Singh
Presented By Harkirat Singh
11/10/2018
CS 510 Internet Routing

2. Motivation WireLess Network is Different from WireLine Network
Ad Hoc Network
- Node Mobility
- Network Partition
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CS 510 Internet Routing

3. Mobility Example: s s a a d d b b s s s T+5 T+20 d d d 11/10/2018
CS 510 Internet Routing

4. Explicit Congestion Notification
By S.Floyd and Team
Active queue management with RED
RED can drop a packet or set a bit
ECN-Echo flg 1, CWR flg 1 (SYN)
ECN-Echo flg 0, CWR flg 1
ECT CE 1
ECN-Echo flg 1
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CS 510 Internet Routing

5. Dynamic Source Routing
<1,3,5,7>
<1,2> 7 7
<1> 2 2
Dest 5 5
Dest.
<1,3,5>
Src 8 8
<1>
Src 1 3 1 3
<1,3>
<1,4,6> 6 6 4
<1,4,6> 4
<1>
<1,4,6>
<1,4>
<1,4,6>
Route Discover – Route Record Propagation of Route Reply
with Route Record
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CS 510 Internet Routing

6. TORA-Route Creation QRY packet UPD pkt – height updates (0,3) (0,1)
(-,-)
(-,-) 7
Dst 7 2
(0,0) 2
Dst 5 5
(0,0) 8 8
(0,3)
(0,2) .
(-,-)
(-,-)
Src
Src. 1 3 1 3
(0,3)
(-,-) 6 6 4 4
(0,1)
(-,-)
(0,2)
(-,-)
QRY packet UPD pkt – height updates
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CS 510 Internet Routing

7. TCP in Ad Hoc Network High Bit Error Rate (BER) Route Recomputation
Network Partition
Multipath Routing
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CS 510 Internet Routing

8. Goal High BER – retransmit lost pkt
Route Recomputation & Transient Partition - stop transmitting
Multipath Routing – No congestion control
Maintain TCP’s congestion control
11/10/2018
CS 510 Internet Routing

9. ATCP Functioning States – Normal, congested, loss and disconnected
Lossy Channel – ATCP loss state and TCP Persist state
Disconnected – ICMP destination unreachable, TCP in persist state and ATCP in disconnected state
Congested – ECN flag, ATCP in congested state and do nothing!
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CS 510 Internet Routing

10. State transition diagram
Receive “Destination Unreachable”
ICMP, CWND 1
Receive dup ACK
or pkt from receiver
TCP sender put
in persist state
Receive ECN
New
Ack
RTO
About to
Expire OR
3 dup ACKs
ATCP
Retransmits
segments in
TCP’s buffer
TCP transmits a pkt
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CS 510 Internet Routing

11. Data flow - TCP/ATCP/IP stack
TCP_input()
TCP_output()
ATCP_input()
ATCP_output()
ipintr()
ip_output()
data
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CS 510 Internet Routing

12. Flowchart for function atcp_input()
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CS 510 Internet Routing

13. Flowchart for function atcp_output()
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CS 510 Internet Routing

14. Performance study Five Pentium PCs, each with two Ethernet cards
Emulate wireless in IP, 32 Kbps channel
Bit error rate 10(-5)
Random hop-by-hop delay
Network congestion – 5sec
Partition – 5 minutes and last for 1 min.
Packet reordering – 25 seconds
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CS 510 Internet Routing

15. Bit Error - Performance
Sequence number
Time (seconds)
Time (seconds)
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16. Bit Error, Congestion Window
Congestion Window Size
Index
Index
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CS 510 Internet Routing

17. Congestion and Partition Performance
Transfer time (second)
hop by hop delay(ms) hop by hop delay(ms)
Congestion Partition
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CS 510 Internet Routing

18. Overall Performance
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CS 510 Internet Routing

19. Conclusion End-to-End TCP semantics are maintained ATCP is transparent
ATCP does not interfere with TCP’s congestion control behavior
ATCP improves performance by one-third
ECN as standard - WIP
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CS 510 Internet Routing

20. References RFC 2481 http://www-nrg.ee.lbl.gov/floyd/ecn.html
draft-ietf-manet-tora-spec-02.txt draft-ietf-manet-tora-spec-02.txt
11/10/2018
CS 510 Internet Routing