The TCP/IP Protocol Suite: IP

Derek Bridge

Department of Computer Science,
University College Cork

The TCP/IP Protocol Suite: IP

Aims:

The Internet Protocol (IP)

IP datagrams

Each IP datagram will consist of two parts:

Class exercise: Why include the address of the source?

Time To Live (TTL)

Class exercise: Why is the datagram discarded? How does this relate to our previous lecture?

IP addresses

IP addresses

Network identifier (network id, network prefix)
A certain number of bits, starting from the left, identifies the network to which the host is attached
Host identifier (host id)
The remainder of the bits identify the host on the network

The dividing line between the two varies from network to network

E.g. 227.82.157.177/20 means the first 20 bits are network id

Class exercise:Why have mobile devices proved problematic?

IP address registration

IP addresses used to be handed out by a single, central organisation, the Internet Assigned Number Authority (IANA)

A hierarchy of Internet registries

Assigning IP addresses to hosts

Static IP address assignment
Each host is manually configured with its IP address, which does not change for as long as the host uses this network
Dynamic IP address assignment
A computer connected to the network (often the local router) has a pool of IP addresses. It allocates them to hosts on an as-needed basis

Class exercise:Why do you think dynamic assignment has become ever more commonplace?

Delivering a datagram

[Diagram illustrating the delivery of a datagram.] Diagram of datagram delivery from The TCP/IP Guide by Charles M. Kozierok

Choosing the next router

Choosing the next router

[Diagram illustrating the routing of a datagram.] Diagram of datagram routing from The TCP/IP Guide by Charles M. Kozierok

IPv4 and IPv6

My journey across the Internet by A. Packet

[Diagram illustrating the delivery of a packet.] Diagram of packet delivery from The TCP/IP Guide by Charles M. Kozierok