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Chapter 9

Layer 4 PDU : Segment , Datagram

Segmenting Data and Reassembling Segments

Tracking Individual Conversations

Identifying the Applications

Transport layer protocols : TCP ve UDP

TCP : reliable (ACK), resend lost data, delivers data in sequenced order. connection-oriented protocol. flow control. (20 byte overhead)

UDP : unreliable (best-effort delivery protocol), fast, low overhead, does not send lost data, no ack, delivers data as it arrives. (8 byte overhead), connectionless, no flow control,

Port Numbers  
2 tür port numaraları kullanılır. source port ve destination port. 0 - 65535 arasındadır.

0 - 1023 : Well known (common)  ports
1024 - 49151 : Registered ports
49152 - 65535 : Dynamic or Private Ports

PC>netstat

tcp 80 : http
tcp 443 : https
tcp 20-21 : ftp
tcp 22 : ssh
tcp 23 : telnet
tcp 25 : smtp
tcp&udp 53 : dns
tcp 110 : pop3
tcp 143 : imap
udp 67-68 : dhcp
udp 69 : tftp
tcp 3389 : rdp

socket = ip address + port number    >    192.168.1.100:80