Computers "talk" together using a set of
languages called protocols. Network protocols are as different
as spoken languages around the world. Now a question might be,
"what's the standard protocol that all computers talk?"
Unfortunately, there is not a single protocol standard that all
computers use, but there are a few common ones that most computers
can use. The primary protocol for connectivity on the Internet
is called TCP/IP. However, many company networks may use a combination
of protocols in order to more efficiently operate and control
the network.
TCP/IP
The primary protocol used on the Internet and on
UNIX based networks is TCP/IP. The actual address component is
IP. There has been one protocol version in use for the last 18
years, called IPv4. The maximum limit of addresses available on
any one network is over 16 million, but only 127 of these networks
numbers exist. However, there are some numbers that are not actually
available due to limitations in the overall numbering system of
IPv4. Every device connecting to an Intranet and/or the Internet
must have a unique address or conflicts will occur that can cause
data replies to be directed to the wrong address. In 1991the IETF
formed a committee to design a new numbering system that would
allow for many more numbers, while still being backward compatible
to IPv4. This new IP numbering scheme is called IPv6 and is in
the final stages of testing and should become a standard soon.
Any network requiring connection to the Internet
needs a valid assigned IP address. The actual controlling body
that assigns the valid IP addresses is called the InterNIC. Although
it looks like a lot of addresses could be used, the actual limit
of assigned addresses is about to be reached, this is why the
IETF formed the IPng committee to design a more robust address
scheme. In addition, many companies with assigned numbers are
not directly connected to the Internet causing many valid addresses
to not be in use directly on the Internet, thereby being a partial
factor in the current address shortage. Recently, the InterNIC
started assigning contiguous blocks of addresses to Internet Service
Providers (ISPs), and then the ISP assigns an address to their
subscribers.
IPv4
IPv4 uses a 32 bit number, represented by four 8-bit
bytes (or octets) in dotted decimal notation. The address is broken
down into two parts: the first is called the "network"
address and the second is called the "host" address.
X.X.X.X is the basic layout, where each X equals a decimal number
between 0-255 or hex 00-FF. There are also certain "class"
numbers used and denoted in the first octet. The class designation
defines how many actual host addresses are available in that specific
network number. Network address 127 and all Class D addresses
are reserved for specific use. The chart below indicates the numbering
layout.
| ||||||
| 1-127 | 127 | 16777214 | net.host.host.host | 255.0.0.0 | 45.1.87.62 | |
| 128-191 | 16384 | 65534 | net.net.host.host | 255.255.0.0 | 154.165.12.48 | |
| 192-223 | 2097152 | 254 | net.net.net.host | 255.255.255.0 | 205.168.25.49 |
In order for an Intranet to have more host addresses than might
normally be available with the IP address assigned, an additional
addressing scheme, called subnetting, can be used.
With subnets, the host portion of an IP address is partitioned
into a subnet number and a 'real' host number on that subnet.
The IP address is now defined as net.subnet.host. Routers outside
of the Intranet do not interpret separately the subnets and host
partitions of the overall IP address. Routers inside the Intranet
and connected to the subnets use a 32 bit subnet mask that identifies
the extension bits. In the net.subnet.host address, the subnet.host
portion contains a number of bits to determine the actual address.
The network administrator allocates bits within a subnet address
and assigns values to the subnet and host addresses. The chart
below indicates some subnet mask numbering schemes.
| Subnet Mask | Number of Subnets | Number of Hosts | |
| 255.255.128.0 | 2 | 32766 | |
| 255.255.192.0 | 4 | 16382 | |
| 255.255.224.0 | 8 | 8190 | |
| 255.255.240.0 | 16 | 4094 | |
| 255.255.248.0 | 32 | 2046 | |
| 255.255.252.0 | 64 | 1022 | |
| 255.255.254.0 | 128 | 510 | |
| 255.255.255.0 | 256 | 254 | |
| 255.255.255.128 | 512 | 126 | |
| 255.255.255.192 | 1024 | 62 | |
| 255.255.255.224 | 2048 | 30 | |
| 255.255.255.240 | 4096 | 14 | |
| 255.255.255.248 | 8192 | 6 | |
| 255.255.255.252 | 16384 | 2 | |
| 255.255.255.128 | 2 | 126 | |
| 255.255.255.192 | 4 | 62 | |
| 255.255.255.224 | 8 | 30 | |
| 255.255.255.240 | 16 | 14 | |
| 255.255.255.248 | 32 | 6 | |
| 255.255.255.252 | 64 | 2 |
IPv6
IPv6 (formerly IPng) uses a 128 bit number, represented by eight
16-bit sections, further represented by hexadecimal numbers (0-9,
A-F). The address layout is: XXXX.XXXX.XXXX.XXXX.XXXX.XXXX.XXXX. XXXX, an example might be: 5F03:2500:CFB5:D700:0000:0260:8C6C:9A9C.
However, there is a shorthand feature in IPv6 that allows for
leading zero's to be truncated, so the above example would actually
be represented by: 5F03:2500:CFB5:D700::260:8C6C:9A9C.
Many new features and enhancements are designed into IPv6. Some
of these are: enhanced addressing capabilities, namely from 32
bits (IPv4) to 128 bits; authentication and privacy capabilities,
extensions to support these security features; flow labeling capability,
a new quality-of-service (QOS) feature providing for special handling
of data. Although the capabilities of IPv6 will be significantly
better than the present IPv4, there are many tests still in process
and many products will require extensive software rewrites in
order to allow IPv6 to interoperate with IPv4. Router software,
DNS applications, client protocol stacks, TCP/IP applications,
will all be required to update to IPv6 as well as a general understanding
of the IPv6 protocol addressing scheme by network administrators
will be required.
There is a test network available on the Internet, called the
6bone, which vendors and ISPs are currently in process of conducting
stress tests. Although the IPv6 protocol is being tested, it may
be a year or two before most of the products are commercially
available. Before a company tries to implement IPv6, it is highly
recommended that they acquire the IPv6 products and connect to
the 6bone and participate in the IPv6 tests, to ensure proper
operation before introducing the products in their production
Intranet.
Glossary:
IETF Internet Engineering Task Force
InterNIC Internet Network Information Center
IP Internet Protocol
IPng IP Next Generation
IPv4 IP version 4
IPv6 IP version 6
ISP Internet Service Provider
NIC Network Interface Card
TCP Transmission Control Protocol
TCP/IP Internet Protocol/Transmission Control Protocol
Copyright © 1997 Jeffrey L. Carrell. All Rights Reserved.
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