OBJECTIVES : TO FAMILIRIZE IN COMPUTER NETWORKING AND INSTALLING A SMALL NETWORK.

APPRATUS : CAT 5 cables

Cable clips

Hub

Two computers with a working NIC

Crimp tool

Blade and a scissor

PROCEDURE :

MAKING A PATCH CABLES

1. The cable was skinned off approximately 3 cm from jacket or slightly more.

2. Each pair was Un-twisted, and each wire was straightened between the fingers.

3. The wires were placed in the order of one of the two diagrams shown below (568B or 568A). All of the wires were brought together, until they were touched.

4. The wiring sequences were rechecked with the diagram, at this point.

5. The grouped (and sorted) wires were hold together tightly, between the thumb, and the forefinger.

6. All of the wires were cut at a perfect 90 degree angle from the cable at 1.5 cm from the end of the cable jacket. This was a very critical step. If the wires were not cut straight, they may not all make contact. A pair of scissors was used for this purpose.

7. Conductors should be at a straight 90 degree angle, and be 1.5 cm long, prior to insertion into the connector.

8. The wires were inserted into the connector, prior to insert the connector was turned pins facing up.

9. All of the wires were pushed moderately hard to assure that they have reached at the end of the connector. Assured that the cable jacket goes into the back of the connector by about 4mm.

10. The connector was place into a crimp tool, and squeezed hard so that the handle reaches its full swing.

11. The process was repeated on the other end. For a straight through cable, the same wiring was used. For a "crossover" cable, wire one end 568A, and the other end 568B.

12. Two straight cables and one cross cable were completed.

DIRECTLY CONNECT TWO PCS

1. The power was turned “ON” on two PCs.

2. One cross cable was taken and firmly inserted to the Ethernet port of one PC then other side to the other PC.

3. If all connections were ok network interface cards became active.

4. Two separate IP numbers were set on TCP/IP properties dialog boxes on each computers then “apply” button was clicked.

5. My network places window was opened and the name of the other computer can be seen.

6. Some files on both computers were shared and then accessed through other computer.

CONNECT TWO PCS WITH A NETWORK

1. A hub was taken and power was supplied.

2. A cross cable was connected across the wall outlet and the hub, flashing LEDs indicates that the hub is activating and sharing its information.

3. Two straight cables were connected across the hub and two PCs.

4. TCP/IP properties window was opened on both computers and, obtain IP address automatically was selected to obtain IP address through a DHCP server.

5. If needed DNS addresses can be assigned to connect internet via an ISP.

6. Some test files were shared among computers to demonstrate the file sharing.

DISCUSSION:

There is a distinction made between networking and internetworking. Networking is the process and methodology applied to connecting multiple computers so that they are able to exchange information. Internetworking is the process and methodology applied to connecting multiple networks, regardless of their physical topologies and distance. Internetworking has evolved with the rapid growth and change in networking. Because of this, the basic building blocks and reference models for networking are also used and applied to internetworking.

Internetworks evolved from necessity. In the early days of computing (the 1950s and 1960s), internetworks did not exist. Computers were autonomous and proprietary. In the late 1960s, however, the United States Department of Defense (DOD) became interested in academic research being done on a packet-switched wide area network design. "Packet" referred to a small bundle of data. "Switched" referred to the use of a routing system similar to the switch-based telephone system. And "wide area network" (WAN) meant that the network would extend over sites that were physically distant from each other.

Challenges involving in internetworking are mainly two;

They are

Interconnectivity the means of transporting information between the computers, inclusive of the physical media, the data packaging mechanism, and the routing between multiple network equipment pieces from the starting node until reaching the destination node.

Interoperability the methodology applied to make data understandable to computers that use proprietary or simply different computer operating systems and languages.

Networks did not become prevalent in corporations until the 1980s when the personal computer (PC) became popular. After companies realized that sharing hard disk space on some of the earliest file servers enabled employees to share data easily and further boosted productivity, they implemented networks on a large scale. They created LANs (Local Area Networks) and then connected them into WANs (Wide Area Networks). After the Internet went commercial in the early 1990's, corporations began to connect to it as well.

The International Organization for Standardization (ISO) created the OSI model and released it in 1984 in order to provide a network model for vendors such that their products would interoperate on networks. The OSI reference model provides a hierarchical tool for understanding networking technology, as well as a basis for current and future network developments.

This model also takes into account the interconnectivity and interoperability challenges faced by the DARPA project engineers. The way that the OSI model answered these challenges was through a seven-layer protocol suite model, illustrated in Figure 1-1. By dividing the model into layers, the capability to interoperate and interconnect became manageable, since each layer was self-contained, not relying on the operating system or other factors. The layered approach benefited vendors, too, since they only needed to concentrate development efforts on the layers that their own product used, and could rely on the existing protocols at other layers. Not only are development costs kept to a minimum, but marketability is increased, since the product works with other vendors' products.

The model describes how each layer communicates with a corresponding layer on the other node. At the first node, the end user creates some data to be sent to the other node, such as an e-mail. At the application layer, an application header is added to the data. The presentation layer adds its own header to the data received from the application layer. Each layer adds its own header to the data received from the layer above. However, at lower layers, the data is broken up into smaller units and headers added to each of the units. For instance, the transport layer will have smaller datagram, the network layer will have packets, and the data link layer will have frames. The physical layer handles the data in a raw bit stream. When this bit stream is received at the destination, the data is reassembled at each layer, and the headers of each layer discarded, until the e-mail is readable by the end user.

The physical layer, or layer 1, defines the actual mechanical specifications and electrical data bit stream. This includes the voltage level, the voltage changes, and the definition of which voltage level is a "1" and which is a "0." The data rate of transmission, the maximum distances and even physical connectors are all included in this level.

The data link layer, or layer 2, is also known as the link layer. It consists of two sub layers, the upper level being the Logical Link Control (LLC), and the lower level being the Media Access Control (MAC). Hardware addresses are actually MAC addresses in the data link layer. The physical address is placed here, since the physical layer handles only raw bit stream functions. The data is broken into small "frames" at this layer.

The physical and data link layers are usually implemented together in hardware/software combination solutions. Examples include hubs, switches and network adapters, and their applicable software drivers, as well as the media or cables used to connect the network nodes. The remaining layers are usually implemented in software only.

The data link layer consists of two sub layers: Logical Link Control (LLC) and Media Access Control (MAC). The MAC sub layer determines the address for the hardware at that layer. This address is network independent, such that wherever the hardware is "plugged in" to the internetwork, it would have the same MAC address, regardless of the network address. The vendor usually assigns the MAC address. In the Ethernet scheme, a series of Ethernet MAC addresses are assigned to a vendor, who then assigns a different address to each interface produced. An Ethernet MAC address consists of 12 digits. The first six digits (the Organizationally Unique Identifier or OUI) are the unique number assigned to the vendor by the IEEE, and the remaining six digits are the series. As a result, each network interface card will have a different MAC address on any given LAN or WAN.

Networking itself is the capability to share data between two nodes. Being able to simply locate the nodes on the network is one of the most basic and important functions in networking. The network layer not only provides a unique node address, but also a unique network address. This enables the routing of data between networks.

Layer 3, or the network layer, is where addressing is most important. When applying the OSI reference model to the IP protocol suite, IP (Internet Protocol) would be at layer 3. The IP addressing scheme determines the network that a node is on and the logical node address on the network. The logical node address is often the same as the MAC address in other protocols, although it is not in IP. This is dealt with on the lower data link layer (layer 2). Note that in Novell IPX, for instance, the MAC address is used for the network-layer node address without modification.

A network layer address is also called a logical address or software address. Network layer addresses are hierarchical, and provide both the network and the node address. A router can easily separate the addresses to be sent on a particular interface by simply looking at the initial network portion of the address-the network address. When the packet reaches the destination network, the node address portion is used to locate the specific station.

Certain addresses in the IP address space have been reserved for special purposes, and are not normally allowed as host addresses. The rules for these reserved addresses are as follows:

The network address portion of an IP address can not be set to "all binary ones" or "all binary zeros"

The subnet portion of an IP address can not be set to "all binary ones" or "all binary zeros"

The host address portion of an IP address can not be set to "all binary ones" or

"all binary zeros"

The network 127.x.x.x can not be used as a network address

Network Addresses

When all the bits in the host portion of an IP address are set to zero, it indicates the network, rather than a specific host on that network. These types of entries are often found in routing tables, since routers control traffic between networks, not individual hosts.

In a subnetted network, setting the host bits to zero would indicate the specific subnet. Also, the bits allocated for the subnet may not be all zeros, since this would refer to the network address of the parent network.

Lastly, the network bits cannot be all zeros, since zero is not an allowed network address, and is used to indicate an "unknown network or address".

Loopback Address

The network address 127.x.x.x has been designated as a local loopback address. The purpose of this address is to provide a test of the local host's network configuration. Using this address provides an internal loopback test of the protocol stack, as opposed to using the host's actual IP address, which would require a network connection.

Local Broadcast

When all the bits in an IP address are set to ones, the resulting address, 255.255.255.255, is used to send a broadcast message to all hosts on the local network. This configuration at the network-layer is mirrored by a corresponding hardware address that is also all ones. Generally this hardware address will be seen as FFFFFFFFFFFF. Routers do not usually pass these types of broadcasts unless specifically configured to do so.

All-Hosts Broadcast

If we set all the host bits in an IP address to ones, this will be interpreted as a broadcast to all hosts on that network. This is also called a directed broadcast, and can be passed by a router if configured to do so. Sample all-host broadcast addresses would look like 132.100.255.255 or 200.200.150.255.

All-Subnets Broadcast

Another type of directed broadcast can be achieved by setting all the subnet address bits to ones. In this case, a broadcast would be propagated to all subnets within a network. All-subnets broadcasting are rarely implemented in routers.

CLASSES OF IP ADDRESSES

The class of an IP address can be determined by looking at the first (most significant) octet in the address. The bit pattern associated with the highest-order bits determines the address class. The bit patterns also define the range of decimal values for the octet that are associated with each address class.

Class A

With a Class A address, eight bits are allotted to the network address, and 24 bits to host addresses. If the highest bit in the first octet is a zero (0), the address is a Class A address. This corresponds to possible octet values of 0-127. Of these, both zero and 127 have reserved functions, so the actual range is 1-126. There are only 126 possible networks that are Class A, since only eight bits are reserved for the network address, and the first bit must be a zero. However, with 24 bits available for host numbers, each network can have 16,777,213 hosts.

Class B

With a Class B address, 16 bits are allotted to the network address, and 16 bits to host addresses. A Class B address is characterized by a bit pattern of 10 at the beginning of the first octet. This corresponds to values from 128-191. Since the first two bits are pre-defined, there are actually 14 bits available for unique network address, so the possible combinations yield 16,383 networks, with each network accommodating 65,533 hosts.

Class C

Class C addresses allocate 24 bits to the network address, leaving 8 bits for host addresses. A Class C address will have a bit pattern of 110 leading the first octet, which corresponds to decimal values from 192-223. With a Class C address, only the last octet is used for host addresses, which limits each network to a maximum of 254 hosts per network. Since there are 21 bits available for unique network numbers (three bits are already preset to 110), there are 2,097,151 possible networks.

Class D

Class D addresses have a bit pattern that begins with 1110. This translates into octet values from 224-239. These addresses are not used for standard IP addresses. Instead, a Class D address refers to a group of hosts, who are registered as members of a multicast group. A multicast group is similar to an e-mail distribution list. Just as you can address a message to a group of individuals using a distribution list name, you can send data to a group of hosts by using a multicast address. Multicasting requires special routing configuration; it is not forwarded by default.

Class E

If the first four bits of the first octet are 1111, the address is a Class E address. These are addresses that start with 240-254. This class of address is not used for conventional IP addresses. This address class is sometimes referred to as the experimental or research class.

The bulk of our discussion will focus on address Classes A, B, and C, since these are the classes used for routine IP addressing. Table 3-1 summarizes the characteristics of address classes.

Address Class	Bit Pattern in the first octet	Range of Addresses
Class A	0xxxxxxx	1-126
Class B	10xxxxxx	128-191
Class C	110xxxxx	192-223
Class D	1110xxxx	224-239
Class E	1111xxxx	240-254

Table 1 IP Address Ranges, Classes, and Bit Patterns

An IP address cannot exist without an associated subnet mask. The subnet mask defines how many of the 32 bits that make up an IP address are used to define the network or the network and associated subnets. The binary bits in the subnet mask form a filter that only passes that portion of the IP address that should be interpreted as the network address. The process by which this is done is called bitwise ANDing. Bitwise ANDing is a logical operation performed on each bit in the address, and the corresponding mask bit. The results of the AND operation is as follows:

1 and 1 = 1

1 and 0 = 0

0 and 0 = 0

So the only time this operation yields a 1 value is when both input values are a 1.

PURPOSE OF SUBNETTING

On a single network, the amount of traffic is proportional to the number of hosts, and the sum of the traffic generated by each host. As the network increases in size, this traffic may reach a level that overwhelms the capacity of the media, and network performance starts to suffer. In a wide-area network, reducing unnecessary traffic on the WAN links is also a major issue.

In looking at such problems, it is typical to discover that groups of hosts tend to communicate routinely with each other, and communicate less frequently outside their group. These groupings may be dictated by common usage patterns of network resources, or may be imposed by geographic distances that necessitate slow WAN links between LANs. By using subnets, we can segment the network, thus isolating the groups' traffic from each other. To communicate between these segments, a means must be provided to forward traffic from one segment to another.

One solution to this problem is to isolate the network segments using a bridge between them. A bridge will learn which addresses reside on each side of itself by looking at the MAC address, and will only forward packets that need to cross network segments. This is a quick and relatively inexpensive solution, but lacks flexibility. For example, a bridge would get confused if it found that it could reach a given address on either side of itself. This makes it generally impossible to build redundant pathways using bridges. Bridges also pass broadcasts.

A more robust solution is to use routers that direct traffic between networks, by using tables that associate network destinations with specific ports on the router. Each of these ports is connected to the source network, the destination network, or some intermediate network that leads to the ultimate destination. By using routers, we can define multiple pathways for data, enhancing the fault tolerance and performance of the network.

One solution to addressing in a routed network might be to simply give each network segment a different network address. This would work in an isolated network, but would not be desirable if the network were connected to the outside world. To connect to the Internet, we must have a unique network address, which must be assigned by a regulating agency. These network addresses are in great demand, and in scarce supply. We also increase the complexity of routing data from the public network to our internal networks if we don't have a common point of entry via a single network address.

To gain the economy and simplicity of a single network address, yet provide the capability to internally segment and route our network, we use subnetting. From the standpoint of external routers, our network would then appear as a single entity. Internally, however, we can still provide segmentation through subnets, and use internal routers to direct and isolate traffic between subnets. The following section will discuss the role of the subnet mask in defining subnets.

In choosing a subnet, the chief consideration is how many subnets we will need to support. The challenge, of course, is balancing the number of subnets with the maximum number of hosts per subnet. There are only 32 bits available for network, subnet and host portions of the address. If we choose a subnet mask that offers more subnets that we need, this will reduce the potential hosts we can support.

The other consideration in choosing the mask is to remember the restriction on subnet values that are all zeros, or all ones. This most often causes problems with a number like 31 subnets. While this is less than the 32 combinations we could achieve with five subnet bits, it would represent an illegal bit combination, since it would be all ones. We must therefore use six bits, which yields up to 62 available subnets.

SUPERNETTING

Part of RFC 791 standard established the address classes and classful addressing. Implied in classful addressing is the assumption that we know what the default subnet mask is based on the first octet of the address. However, prior to RFC 791, an earlier RFC (760) had proposed an IP address format that was not class-based. Address classes were considered a good idea in 1982, since the class assumptions eliminated having to send masking information with an IP address, but since we are now running out of registered IP addresses, the classes have become a serious problem.

The only available addresses that have not been assigned are the Class C addresses. Since a Class C network can only support 254 hosts, large organizations wishing to have a registered address may request multiple contiguous Class C addresses, and integrate them into a single entity using a process called supernetting. It is also sometimes referred to as classless interdomain routing (CIDR).

What supernetting does is to remove bits from the default mask, starting at the rightmost bits and working to the left.

IP: The Next Generation

IP addressing is at a crossroads. The explosive growth of the Internet has caused a crisis with existing IP address formats. The only registered IP addresses that can be obtained right now are Class C addresses. As we have learned, these have severe limitations in terms of the maximum number of hosts supported, which has led to creative approaches such as supernetting.

The longer-term solution is to revamp the whole specification for IP addressing. The proposed solution is called IP version 6 or Ipv6 for short. The format for version 6 IP addresses will move from the present 32-bit address to an address format of 128 bits. This will be represented as 32 hexadecimal digits, expressed as shown in this example: A923.FF23.BA56.34F3.

Unfortunately, this address format is not compatible with existing IP addresses. Ipv6 will probably be implemented first with external IP addresses on the Internet, which would then be routed through gateways to internal networks that continue to use the existing 32-bit address format

ADDRESS MAPPING

Host name to address mapping is a process that allows user-friendly names for network hosts, rather than having to specify them by their IP address. When we use these types of names, some method must be provided to convert from the names to the actual IP addresses. This would typically involve using a mapping file or table, and/or a server called a Domain Name Service (DNS) server.

When an address has been resolved from a host name, a router keeps that information in a local cache. This way it can avoid re-submitting the resolution request to the DNS server again later.