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UNIT 30: Protocols Table of Contents
UNIT 30: Protocols
1.0 Introduction
The Internet Protocol (IP) had its origin in UNIX a networking as it developed in the 1970s. Today, IP has become a standard mechanism for network operating systems (NOS) to communicate with each other. In its simplest form, a protocol is an agreed upon set of rules. Protocols can be defined in one of three ways; standard, public and private.
A standard protocol is defined as a protocol whose specification is published and known to the public but controlled by a standard body. A public protocol is defined as a protocol whose specification is published and known to the public but controlled by a private organisation. A private protocol is defined as a protocol whose use and specification are controlled by a private organisation.
2.0 Objectives
At the end of this unit you should be able to:
Identify an IP address;
Identify the IP address sub-divisions;
Explain the use of Network numbering (address);
Explain Subnetting.
3.1 Internet Protocol Basic Addressing
An IP address contains a full four bytes (32 bits) of data. For readability purposes, humans typically work with IP addresses in a decimal notation that uses periods to separate each byte (also known as an octet). For example, the IP address
00001010 00000000 00000000 00000001 often appears in the equivalent string representation:
10.0.0.1
IP addresses can be sub-divided into classes. The values of the leftmost four (4) bits of an address determine its class. All "Class A" addresses, for example, have the leftmost bit set to zero, but each of the remaining 31 bits may be set to either "0" or"!" independently (as represented by an 'X' in these bit positions):
Oxxxxxxx xxxxmx xxxxxxxx xxxxxx,vc
From this rule it follows that Class A addresses include all values in the range
-0.0.0.0" to "127.255.255.255".
Class B addresses must have the leftmost bit set to one, and the next bit set to zero, but all other bits may vary:
10xxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
And so it follows that Class B addresses fall in the range from "128.0.0.0" to "191.255.255.255".
Similarly, Classes C. D. and E addresses set the second, third, and fourth bit (respectively) to one.
Table III summarizes the overall breakdown of all IP addresses into this class system.
Table III: Summary of Breakdown of all IF Address into class system.
Class Leftmost bits Start address Finish address
A Om 0.0.0.0 127.255.255.255
B 10)o( 128.0.0.0 191.255.255.255
C 110x 192.0.0.0 223.255.255.255
D 1110 224.0.0.0 239.255.255.255
E 1111 240.0.0.0 255.255.255.255
Exercise 1
List the subclass of an IP address and explain their differences.
Nearly all of the Class A and Class B IPv4 address domains have already been assigned to large organisations. Addresses in the Classes D and E ranges have been reserved for special purposes by the IP administrative authorities. (The terms "Class D" and "Class E." while technically correct, do not appear much in practice). Effectively this leaves only Class C address range available for public consumption.
3.2 Domain Naming and Registration
Names offer a more convenient, easily-remembered way to uniquely identify computers on the network than IP addresses alone. The domain name system (DNS) used across the Internet assigns names to individual IF addresses and performs the mapping (translation from name to address) on demand as needed. The term domain naming refers to the structure of the naming system: names and addresses are organized in a hierarchy and maintained in a distributed fashion across the Internet.
Activity 1
Next time you sit down at a computer, see if you can determine its IP address and domain name.
Names and adresses on the public Internet must be registered with an accredited registrar. For nodes in the ".com," ".net," and ".org" domains, the Internet Corporation for Assigned Names and Numbers (ICANN) oversees registrations. Registered names and addresses must be renewed periodically, and should a dispute occur between two parties over ownership of a given name, such as in trademarking, ICANN's Uniform Domain-Name Dispute-Resolution Policy (URDP) can be invoked.
Exercise 2
What is the advantage of using domain names rather than IP address?
3.3 IPv4 and IPv6
The IP system in widespread use today is also known as IPv4 ("version four"). A newer system, 1Pv6 ("version six" -- version five was essentially skipped), exists now in small deployments and should replace IPv4 in years to come. IPv6 improves the addressing system by supporting up to 128 - bit instead of 32-bit addresses, and it adds additional features for performance and privacy.
IPv4 can only represent a finite number of computers on the Internet - approximately 4,294,967,296, or 2 raised to the 32nd power. At the time IP was conceived, this number was perfectly reasonable.
but with the explosive growth of the Web and networked computing generally, a time may come in the not-too-distant future when the IPv4 address space will be exhausted. Thanks to technologies
like Network Address Translation (NAT), computers can use virtual addressing analogous to the way network operating systems use virtual memory, but it remains unclear if these relatively recent technology developments will adequately conserve IP space.
Exercise 3
Explain the limitation of Internet Protocol version four.
The Internet protocol version four has a limitation of being only able to represent a finite number of computers on the internet.
3.4 Subnetting
Subnets allow network traffic between hosts to be segregated based on the network's configuration.
In IP networking, traffic takes the form of packets. IP subnets improve network security and performance to some degree by organizing hosts into logical groups.
3.4.1 Subnet Masks
Probably the most easily recognizable aspect of subnetting is the "mask." Just je IP addresses, subnet masks contain four bytes (32 bits) and usually appear in the same "dotte ecimal" notation.
For example, a very common subnet mask in its binary representation will usually be shown in the equivalent, more human - readable form.
11111111111111111111111100000000 255.255.255.0
Exercise 4
Explain the importance of Subnetting.
As indicated above. subnetting allows network traffic between hosts to be segregated based on the network configuration.
3.4.2 Masking Rules
A subnet mask neither serves as an IP address nor does it exist independently from them. Instead, subnet masks must be applied to IP addresses. Masking a full IP address has the effect of splitting it into two parts -- an -extended network address" and a host address.
For a subnet mask to be valid, its leftmost bits must be set to one; a mask of all zeros 00000000 00000000 00000000 00000000
is invalid. In addition, its rightmost bits must be set to zero; the mask of all ones 11111111111111111111111111111111111
is likewise invalid. In other words, all valid subnet masks contain two parts: the all-ones left side (the extended network portion) and the all-zeros right side (the host portion).
3.4.3 Subnetting in Practice
An extended network address includes the basic network address as well as additional bits that represent the "subnet number." Used in conjunction with a network address, a subnet number supports a two-level, "extended" addressing scheme recognized in a standard way by implementations of IP.
Taken together, the extended network address with the host address actually produces a three -level scheme.
Consider the following real-world example. A small business plans to use the "192.168.1.0"
network for its internal (intranet) hosts. The human resources department wants their computers to be on a controlled part of this network because they store payroll information and other sensitive employee data. But because this is a Class C network, its default subnet mask of "255.255.255.0"
will allow all computers to be peers on the network by default.
The first four bits of 192.168.1.0 -- 1100 -- place this network in the Class C range and also fix the length of the network address at 24 bits. To subnet this network, more than 24 bits must be set to one on the left side of the subnet mask. For instance, the 25-bit mask "255.255.255.128" creates a two-subnet network as follows.
Table IV: Two -Su bn et Netwo rk Network address
(24 bits)
Subnet number
(1 bit) Exten ded
Network
Host address range
11000000 10101000 0
192.168.1.0 192.168.1.1-
00000001 192.168.1.127
11000000 10101000 1 192.168.1.128 192.168.1.129-
00000001 192.168.1.255
For every additioal bit set to one in the mask, another bit becomes available in the subnet number to index additional subnets. A two-bit subnet number can support up to four subnets, a three-bit number supports up to eight. and so on.
3.5 Private Networks
The governing bodies that administer the Internet Protocol have identified certain networks as reserved for internal use. In general, intranets that use these networks can reduce the difficulty in administering their IP configuration and Internet access. These three networks, along with their default masks, are listed below.
T abl e V : T h r ee N etw o r k s w i th th ei r D ef au lt M ar ks Network address Def au lt mask
10.0.0.0 255.0.0.0
172.16.0.0 255.240.0.0
192.168.0.0
255.255.0.0
3.6 Network Numbering
Computer networks consist of individual segments of network cable. The electrical properties of cabling limit the useful size of any given segment such that even a modestly-sized local-area network (LAN) will require several of them. Gateway devices like routers and bridges connect these segments together although not in a perfectly seamless way.
Besides partitioning through the use of cable, subdividing of the network can also be done at a higher level. Subnets support "virtual" network segments that partition the traffic flowing through the cable rather than the cables themselves. The subnet configuration often matches the segment layout one-to-one, but subnets can also subdivide a given network segment.
3.7 Network Addresses
Even without subnetting, hosts on the Internet (or any other IP network) are uniquely identified on a network by something called the network number. (Multi-homed nodes, that contain multiple network adapters, can belong to multiple networks). Network numbering allows a group of hosts (peers) to communicate efficiently with each other; these may be computers located in the same facility or all computers used by a workgroup, for example.
Network numbers look very much like IP addresses, but the two should not be confused. In the absence of subnetting. some "default" networks can be derived immediately from host IP addressing and its class structure. Consider the host IP address 10.0.0.1, for example, an address commonly used on private networks. Because it is a Class A address, with no subnetting employed, its leftmost by (eight bits) by default refer to the network address (10), and all other bits remain set at zero (10.0.0.0). Thus, 10.0.0.0 is the network number corresponding to IP address 10.0.0.1.
In this scheme, the part of the IP address that does not refer to the network refers instead to the host address (literally, the unique identifier of the host on that network). In this example, the host address becomes "0.0.0.1" or simply "1". Also note that a network address becomes a reserved address that should not be assigned to any actual host. Hosts like 10.0.0.1 may use the 10.0.0.0 address for special purposes, and having a live host at that location could cause conflicts.
The table below illustrates the numbering scheme for Classes A, B, and C networks. Although the same scheme can apply to Classes D and E networks, those address ranges have been reserved for other purposes and should be discussed separately.
Table VI: Numbering Scheme for Classes of Networks
Class Host address range Network address Default mask
A 0.0.0.0- 127.255.255.255 x.0.0.0 255.0.0.0
B 128.0.0.0 - 191.255.255.255 x.x.0.0 255.255.0.0
C 192.0.0.0 - 223.255.255.255 x.x.x.0 255.255.255.0
n general, a network address uses the leftmos byte of its hosts' addressing if the hosts fall within the Class A range, the leftmost two bytes for hosts in Class B. and the leftmost three bytes for hosts in Class C. This algorithm is applied in practice with the use of a network mask. The above table shows the decimal representation of the default network masks that is commonly used by network operating systems. The decimal value "255" corresponds to one byte that has all bits set to one (11111111).
4.0 Conclusion
Class A and Class B address domains have already been assigned to large organisations. While Addresses in the Classes D and E ranges have been reserved for special purposes by the IP administrative authorities, leaving only Class C address ranges available for public consumption.