Information Technology Reference
In-Depth Information
Internet would not have evolved so quickly and possibly would not have occurred at all. TCP
and IP are excellent protocols as they are simple and can be run over any type of network,
on any type of computer system.
The Internet is often confused with the World Wide Web (WWW), but the WWW is only
one application of the Internet. Others include electronic mail (the No.1 application), file
transfer, remote login and so on.
The amount of information transmitted over networks increases by a large factor every
year. This is due to local area networks, wide area networks and of course, traffic over the
Internet. It is currently estimated that traffic on the Internet doubles every 100 days and that
three people join the Internet every second. This means an eightfold increase in traffic over a
whole year. It is hard to imagine such growth in any other technological area. Imagine if
cars were eight times faster each year, or could carry eight times the number of passengers
each year (and of course roads and driveways would have to be eight times larger each
year).
23.16 Additional material
23.16.1 Assigned Internet protocol numbers
Table 23.5 outlines the values that are used in the protocol field of the IP header.
Table 23.5
Assigned Internet protocol numbers
Value
Protocol
Value
Protocol
0
Reserved
18
Multiplexing
1
ICMP
19
DCN
2
IGMP (Internet group management)
20
TAC monitoring
3
Gateway-to-gateway
21-62
4
CMCC gateway monitoring message
63
Any local network
5
ST
64
SATNET and backroom EXPAK
6
TCP
65
MIT subnet support
7
UCL
66-68
Unassigned
8
EGP (exterior gateway protocol)
69
SATNET monitoring
9
Secure
70
Unassigned
10
BBN RCC monitoring
71
Internet Packet core utility
11
NVP
72-75
Unassigned
12
PUP
76
Backroom SATNET monitoring
13
Pluribus
77
Unassigned
14
Telenet
78
WIDEBAND monitoring
15
XNET
79
WIDEBAND EXPAK
16
Chaos
80-254
Unassigned
17
User datagram
255
Reserved
23.16.2 Options field in an IP header
The options field in an IP header is an optional field which may or may not appear in the
header, and is also variable in length. It is a field which must be implemented by all hosts
and gateways. There are two classes of option:
