Instructor: Sam Nanavaty TCP/IP protocol

Instructor: Sam Nanavaty Version – Allows for the evolution of the protocol IHL (Internet header length) – Length of header in 32 bit words. Minimum value is 5 (i.e., 20 bytes) Type of Service (TOS) – Specifies reliability, throughput, delay and precedence Total length – total datagram length in bytes Identification: Seq. # taken together with source/dest addr and user protocol makes this datagram unique for the time it remains on the internet. Flags: 2 bits defined (more bit and don’t fragment bit) Fragment offset: Where in the datagram does this fragment belong (in 64 bit units) TTL: How long in seconds is this datagram allowed to live on the internet P| P| P|D| T| R| 0| 0 Type Of service (8)

Instructor: Sam Nanavaty Protocol: Identifies the next higher level protocol that must receive this datagram Header checksum: error checking (note that header values may change enroute and thereby routers would re-compute the checksum. Source IP address and Destination IP address: 4 byte address each. Options: Options specified by the sender Padding: ensure that datagram header is a multiple of 32 bit in length (4 bytes multiple) Data: Maximum length is that includes the header.

Instructor: Sam Nanavaty TRANSMISSION CONTROL PROTOCOL Connection oriented USER DATAGRAM PROTOCOL Connectionless INTERNET PROTOCOL FTPFTP TELNETTELNET HTTPHTTP Well Known Ports <=1023 custom Defined Ports TFTPTFTP SNMPSNMP NNSNNS

Instructor: Sam Nanavaty SOURCE PORT (16)DESTINATION PORT(16) SEQUENCE NUMBER (32) ACKNOWLEDGEMENT NUMBER (32) Data Offset (4) Res (6)FLAGS (6)WINDOW (16) CHECKSUM (16)URGENT POINTER (16) OPTIONS + PADDING (VARIABLE) Sequence # - Seq # of first data octet in the segment Ack # - (used in piggybacked ack) Seq # of next data octet that TCP expects to receive Data Offset - number of 32 bit words in the TCP Header

Instructor: Sam Nanavaty SOURCE PORT (16)DESTINATION PORT(16) SEQUENCE NUMBER (32) ACKNOWLEDGEMENT NUMBER (32) Data Offset (4) Res (6)FLAGS (6)WINDOW (16) CHECKSUM (16)URGENT POINTER (16) OPTIONS + PADDING (VARIABLE) FLAGS (this is a 6 bit field): URG: When urgent data is present, this bit is set to notify receiving appln. ACK: Acknowledgment number valid flag PSH: Application may force TCP to send out existing data w/o further wait RST: abort connections SYN: Used to initiate a new connection FIN: Terminate connection

Instructor: Sam Nanavaty SOURCE PORT (16)DESTINATION PORT(16) SEQUENCE NUMBER (32) ACKNOWLEDGEMENT NUMBER (32) Data Offset (4) Res (6)FLAGS (6)WINDOW (16) CHECKSUM (16)URGENT POINTER (16) OPTIONS + PADDING (VARIABLE) Window: number of data bytes beginning with the one indicated in the acknowledgment # field which the sender of this segment is willing to accept Checksum: for Error checking Urgent Pointer: Points to last octet in the sequence of urgent data Options: Example, max segment size that will be acceptable

Instructor: Sam Nanavaty SYN ACK SYN/ACK Initial Seq # I A Initial Seq # I B, ACK set Ack # = I A + 1 AB Seq # = I A +1, ACK set Ack# = I B +1 TCP connection using 3 way handshake

Instructor: Sam Nanavaty Source Port (16)Destination Port (16) Length (16)Check sum (16) Total length of UDP header is 8 octets UDP has no flow control mechanism UDP provides no error correction UDP Header