Network Programming Eddie Aronovich mail eddieamta ac il

Network Programming Eddie Aronovich mail: eddiea@mta. ac. il

How did it started ?

How can we write communication ? 4 Application Program Interface (API) – Sockets – TLI (Transport Layer Interface) 4 System calls 4 Library functions

What is it for ? Communication systems provides 3 services: – Information & resource Sharing – Distance gapping – Backup abilities

Fundamentals 4 Server - An entity which gives services 4 Client - An entity which requests services 4 Transport layer - To transfer the data

The 7 layers model

The 7 Layer model in real life

TCP Lecture. III

Transmission Control Protocol rfc 793 4 Reliability 4 Sequenced data transfer 4 Flow control 4 Full duplex

TCP Header Source port number (16 bit) Dest port number (16 bit) Sequence number (32 bit) Acknowledgement number (32 bit) FIN SYN RST PSH ACK F. F. U (6 bit) URG Header length (4 bit) TCP Checksum (16 bit) Window size (16 bit) Urgent Pointer (16 bit) Options Data

Ack & Flow control 4 Acknowledgements are sent by byte. 4 The acks can be sent for group of packets (but should arrive before time out of first packet). 4 Window size is used for flow control and is controlled by receiver.

How connection starts ? connect(); connect returns…. SYN j SYN k, ACK j+1 listen(); accept returns…. ACK k+1 Connection Established

How we do it in C ? Server Client socket(); bind(); listen(); accept(); {New file descriptor is given} connect();

Ending Sessions Passive close (FIN arrives) Vs. Active close FIN M ACK M+1 FIN N ACK N+1