Friday, 25 September 2015

Internet Protocols

User Datagram Protocol (UDP):- UDP is a connectionless transport layer protocol. The term connectionless means it does not create virtual circuit before start transfer data or it does not send SYN and Ack packets. UDP does not sequence the segments and does not care in which order the segments arrive at the destination. Because of this, it’s referred to as an unreliable protocol.UDP is very fast than TCP but not reliable. So where we need speed to transfer data we use UDP Ex. VOIP, for reliable communication we use TCP.

Port Numbers:- All protocols have a predefined port number on which they receive data or packets. To send data there must be both port number for source and destination, Source port assign randomly or dynamically but destination port number always be well known. Ports from 0 to 1023 are well known ports.

Internet Layer Protocol
  1. IP
  2. ARP
  3. ICMP
  4. Proxy ARP
IP  :-  IP receives segments from the Host-to-Host layer and fragments them into datagram’s  if necessary. IP then reassembles datagram’s back into segments on the receiving side. Each datagram is assigned the IP address of the sender and of the recipient. Each router that receives a datagram makes routing decisions based on the packet’s destination IP address.

TTL:- The time to live  is set into a packet when it is originally generated. If it doesn’t get
to where it wants to go before the TTL expires, This stops IP packets from  looking for a destination        .

Protocol:-  Port of upper-layer protocol. Also supports Network layer protocols.

Header checksum: - Cyclic redundancy check (CRC) on header only.

Source IP Address: - 32-bit IP address of Source Device.

Destination IP address: - 32-bit IP address of the destination device.

IP options:- Used for network testing, debugging, security.

Data:- After the IP option field will be the upper-layer data.

ARP:- Address Resolution Protocol is used to resolve MAC address from IP address. If IP doesn’t find the destination host’s hardware address in the ARP cache, it uses ARP to find MAC.

ICMP:- Internet control messaging protocol is a management and messaging protocol for IP.

Proxy ARP:- Proxy ARP can actually help machines on a subnet reach remote subnets without configuring routing or even a default gateway. Proxy Using ARP will definitely increase the amount of traffic on your network segment, and hosts will have a larger ARP table than usual in order to handle all the IP-to-MAC address mappings 
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