An introduction to TCP and its modeling By

An introduction to TCP and its modeling By: Amin Pour. Rostami

Internet Protocol (IP) n n Unreliable Best-Effort End-to-End Data-link protocols

IP Protocol stack n n fragmentation time-to-live type-of-service Datagram length 4 -bit Version 4 -bit Header length 8 -bit Type of service 16 -bit Total length 3 -bit Flags 13 -bit Fragment offset 16 -bit Identification 8 -bit Time to live 8 -bit Protocol 16 -bit Header checksum 32 -bit Source IP address 32 -bit Destination IP address Options Data

Transmission Control Protocol (TCP) n n n Multiplexed Duplex Connection-oriented Reliable Flow-controlled Byte-stream

TCP Protocol Stack 16 -bit Source port number 16 -bit Destination port number 32 -bit Sequence number 32 -bit Acknowledgement number 4 -bit Header length Reserved (6 bits) U R G A C K P S H P S T S Y N 16 -bit TCP checksum F I N 16 -bit Window size 16 -bit Urgent pointer options data

Flow Control n Open-Loop n n n source RTT λ Conflicting requirements Traffic descriptors Peak and average rates Linear bounded arrival processes µ B 0 Closed-Loop n … First generation (match sending rate to destination service rate) On-Off Stop-and-Wait Static window Second generation( match sending rate to destination and network service rate) State measurement Choice of control Point of control Explicit Dynamic window End-to-End Implicit Dynamic rate Hop-by-Hop sink

Flow Control n Closed-loop Cntd. Explicit Implicit Dynamic window Dynamic rate End-to-End De. Cbit ATM Forum EERC TCP-Tahoe TCP-Reno TCP-Vegas NETBLT Packet-pair Hop-by-Hop Credit-based Mishra/Kanakia -----------------------

TCP Flow Control n TCP-Tahoe n n TCP-Reno n n n Selective ACKs TCP-Vegas n n Detects losses using both timeouts and three duplicate ACKs Timeout -> Tahoe Fast retransmit ->congestion-avoidance->continues even if ACKs received Exponential back-off TCP-SACK n n Detects losses using timeouts Decreases the flow control window to 1 Ssthresh = , slow-start, congestion-avoidance … Described later D-

TCP-Reno modelling Congestion avoidance Fast retransmit Slow start Exponential backoff

TCP-Vegas Modelling n Adaptive scheme