UDP/TCP/IP Protocol Architecture

 

Ø      Overall Picture of the TCP/UDP/IP protocols

Ø      Protocol Headers

Ø      Overview of TCP  

Ø      State Transition Diagram

Ø      Connection end-points

Ø      Buffering

Ø      Overview of UPD

Ø      Standard Services and Protocol Usage

 

 


Ø Overall Picture of the TCP/UDP/IP protocols:

 

 

 


Ø Protocol Headers:

 

IP  ,   UDP  ,   TCP   &   Encapsulation

 

 

 

 

    Encapsulation

 

 


Ø Overview of TCP:

 

à      Reliability: Requires ACK & Retransmission.

It dynamically computes RTT for estimating how long to wait for ACKs: 

millisecs for LANs, seconds WANs.

 

à      Sequence Numbers: To detect packet loss, reordering and duplicate removal.

 

à      Flow Control: Tell peer exactly how many bytes it is willing to accept

                          (receiver buffer called window).

à      Full Duplex: send and recv data in both directions.

 

à      Connection Establishment: 3-way handshake

 

à   Options: Each synch segment contains:

§  MSS Option: maximum segment size (the maximum amount of data it is willing to accept in each TCP segment).

§  Window Scale Option: maximum window is 65,535 bytes,

it can be scaled (left-shifted) by 0-14 bits providing a maximum of 65,535x2**14 byte (one gigabyte).

à   Connection Termination: Requires 4 segments

 


Ø State Transition Diagram:

 

 

 

ê   

ê  Watching the Packets: Packet exchange for TCP Connection

ê   

 

 

Time-Wait state: (around 2 minutes)

 

ü To allow old duplicate segments to expire in the Network.

ü The end that performs the active close is the one that goes through TIME-WAIT state in order to ACK the final FIN.

 

 

 


Ø     Connection end-points:

 

ü  Port numbers: 16 bit integers (65,535).

 

ü  Socket Pair:    four_tuple    < localIP,   localPort,     foriegnIP,   foriegnPort >

 

ü  Concurrent servers:  listen, connect and accept ,

2nd Client:                                                                                            

 


Ø Buffering: 

 

Buffer Sizes and Limitations:

ü MTU: Maximum Transmission Unit (Ethernet 1500 bytes).

ü Path MTU: smallest MTU in a path.

ü If IP datagram exceeds MTU it is fragmented & reassembled at the final destination.

ü If DF (Do't fragment) bit is set, ICMP is returned

(this is the basis for the path MTU discovery).

ü IP with 576 bytes will not be fragmented.

ü TCP MSS is = (interface MTU - header lengths).

 

TCP Output: 

        Return from write means: reuse application buffer,

but data may still be in  the socket buffer of sender and it does not mean the peer got it.

 

 

 

 

 


Ø Overview of UPD:

 

ü Simple.

ü Connectionless.

ü Unreliable.

UDP Output: 

       No buffering, packets are copied directly into the datalink output queue.

 

 

 

 

 


Ø Standard Services and Protocol Usage:

 

Standard Internet Services:

Sample  (More details at: /etc/services)

 

 

 

Protocol Usage by Common Internet Applications:

Examples