17-01-2013, 04:33 PM
Addressing the network IPv4
Addressing.ppt (Size: 1.45 MB / Downloads: 46)
3 types of address
Every network has:
Network address – the first one
Broadcast address – the last one
Host addresses – everything in between
Classless addressing
Any suitable prefix can be used
We (and devices) need to know what the prefix is.
More flexible, less wasteful.
Unicast, Multicast, Broadcast
Unicast – a message addressed to one host
Broadcast – a message addressed to all hosts on a network. Uses network’s broadcast address or 255.255.255.255 locally
Multicast – a message addressed to a group of hosts. Uses an address starting 224 - 239
Public IP addresses
Routed over the Internet
Master holder is IANA
Assigned to regional registries and then to ISPs
ISPs allocate them to organisations and individual users
Use is strictly controlled as duplicate addresses are not allowed
Special addresses
0.0.0.0 “all addresses” in default route. Hosts cannot be given addresses starting 0.
127.0.0.1 is loopback. Hosts cannot be given addresses starting 127.
240.0.0.0 and higher – reserved for experimental purposes.
169.254.0.0 - 169.254.255.255 local only
192.0.2.0 to 192.0.2.255 for teaching
Network address translation
A large number of hosts on a network use private addresses to communicate with each other.
The ISP allocates one or a few public addresses.
NAT allows the hosts to share the public addresses when they want to use the Internet
Addressing hosts
Static addressing – address is configured by an administrator
Servers, printers, routers, switches need static addresses
Dynamic addressing – address is allocated automatically by DHCP by leasing addresses from a pool
Dynamic addressing is best for workstations
Subnetting 192.168.1.0/24
Every time you borrow another bit you:
Double the number of subnets
Halve the size of the subnets
Each subnet has a network address, a broadcast address, and everything in between is a host address.
Here are some ways of visualising the process.
IPv6
Development started in 1990s because of concerns about IPv4 addresses running out
A whole new protocol suite – not just layer 3
Uses 128-bit hierarchical addressing, written using hexadecimal
Simpler header
Integrated security – authentication, privacy
Quality of service mechanisms