ATCP TCP for Mobile Ad Hoc Networks By

ATCP : TCP for Mobile Ad Hoc Networks By Jian Liu and Suresh Singh Presented By Harkirat Singh 10/15/2021 CS 510 Internet Routing 1

Motivation n n Wire. Less Network is Different from Wire. Line Network Ad Hoc Network - Node Mobility - Network Partition 10/15/2021 CS 510 Internet Routing 2

Mobility Example: s s a a d d b s d 10/15/2021 b s T+5 T+20 d CS 510 Internet Routing s d 3

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 ECT 1 10/15/2021 (SYN) ECN-Echo flg 0, CWR flg 1 CE 1 ECN-Echo flg 1 CS 510 Internet Routing 4

Dynamic Source Routing <1, 2> <1> Src 1 <1> 2 <1> 7 5 3 <1, 3, 5, 7> 2 <1, 3, 5> <1, 3> 4 Src 1 6 <1, 4, 6> Dest 5 8 Dest. <1, 4> 8 3 <1, 4, 6> 6 4 <1, 4, 6> Route Discover – Route Record 10/15/2021 7 Propagation of Route Reply with Route Record CS 510 Internet Routing 5

TORA-Route Creation (-, -) 2 Src. 1 (-, -) 7 Dst 8 (0, 0). Src 1 (0, 3) 5 (-, -) 3 (-, -) 4 (0, 1) (0, 3) (-, -) 7 2 6 5 (0, 3) 3 4 (-, -) Dst (0, 0) 8 (0, 2) 6 (0, 1) (0, 2) (-, -) QRY packet 10/15/2021 UPD pkt – height updates CS 510 Internet Routing 6

TCP in Ad Hoc Network n n High Bit Error Rate (BER) Route Recomputation Network Partition Multipath Routing 10/15/2021 CS 510 Internet Routing 7

Goal n n High BER – retransmit lost pkt Route Recomputation & Transient Partition - stop transmitting Multipath Routing – No congestion control Maintain TCP’s congestion control 10/15/2021 CS 510 Internet Routing 8

ATCP Functioning n n 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! 10/15/2021 CS 510 Internet Routing 9

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 TCP transmits a pkt 10/15/2021 CS 510 Internet Routing ATCP Retransmits segments in TCP’s buffer 10

Data flow - TCP/ATCP/IP stack data TCP_input() TCP_output() ATCP_input() ATCP_output() ipintr() ip_output() data 10/15/2021 CS 510 Internet Routing 11

Flowchart for function atcp_input() 10/15/2021 CS 510 Internet Routing 12

Flowchart for function atcp_output() 10/15/2021 CS 510 Internet Routing 13

Performance study n n n n 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 – 5 sec Partition – 5 minutes and last for 1 min. Packet reordering – 25 seconds 10/15/2021 CS 510 Internet Routing 14

Bit Error - Performance Sequence number Time (seconds) 10/15/2021 Time (seconds) CS 510 Internet Routing 15

Congestion Window Size Bit Error, Congestion Window Index 10/15/2021 Index CS 510 Internet Routing 16

Transfer time (second) Congestion and Partition Performance hop by hop delay(ms) Congestion 10/15/2021 hop by hop delay(ms) Partition CS 510 Internet Routing 17

Overall Performance 10/15/2021 CS 510 Internet Routing 18

Conclusion n n End-to-End TCP semantics are maintained ATCP is transparent ATCP does not interfere with TCP’s congestion control behavior ATCP improves performance by onethird ECN as standard - WIP 10/15/2021 CS 510 Internet Routing 19

References n n n RFC 2481 http: //wwwnrg. ee. lbl. gov/floyd/ecn. html draft-ietf-manet-tora-spec-02. txt draftietf-manet-tora-spec-02. txt 10/15/2021 CS 510 Internet Routing 20