Networking Devices and Network Components

Networking devices are products used to connect networks. As computer networks grow in size and complexity, so do the networking devices used to connect them.

However, all networking devices share one or more common purposes.

1. They allow a greater number of nodes to be connected to the network. A node is an endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be processors, controllers, or workstations. Nodes vary in routing and other functional capabilities; they can be interconnected by links, and they serve as control points in the networks. Node is sometimes used generically to refer to any entity that can access a network and is frequently used interchangeably with device.
2. They increase the distance over which a network can extend.
3. They localize traffic on the network.
4. They can merge existing networks.
5. They isolate network problems so that the problems can be diagnosed more easily.

The following networking devices broadly used in network.

1. Repeaters
2. Hubs
3. Bridges
4. Switches
5. Routers
6. Gateways
7. Modems
8. Network Interface Card (NIC)

Read more

Network Support | IPCONFIG

When you run ipconfig at the Windows command line you see a display like this:

ipconfig Command

ipconfig [/? | /all | /release [adapter] | /renew [adapter]]

• /?  -- Display help message.
• /all  -- Display full configuration information.
• /release  -- Release the IP address for the specified adapter.
• /renew  -- Renew the IP address for the specified adapter.

The default is to display only the IP address, subnet mask and default gateway for each adapter bound to TCP/IP.

For Release and Renew, if no adapter name is specified, then the IP address leases for all adapters bound to TCP/IP will be released or renewed.

Read more

Networking Device | Network Interface Adapters (NIC)

A network interface card is used to connect a computer to an Ethernet network. The card provides an interface to the media.

The network interface adapter (called network interface card, or NIC, installed in a computer's expansion slot) is the component that provides the link between a computer and the network of which it is a part. This may either by using an external transceiver or through an internal integrated transceiver mounted on the network interface card PCB. The card usually also contains the protocol control firmware and  Ethernet Controller needed to support the Medium Access Control (MAC) data link protocol used by Ethernet. Every computer must have an adapter that connects to the system’s expansion bus and provides a connection to the network medium.

Functions of Network Interface Adapter:

Network interface adapters perform a variety of functions that are crucial to getting data to and from the computer over the network. These functions are as follows:

• Data encapsulation
• Signal encoding and decoding
• Data transmission and reception
• Data buffering
• Serial/parallel conversion
• Media access control

Read more

Networking Device | Modems

Modem is any type of data communications equipment (DCE) that enables digital data transmission over the analog Public Switched Telephone Network (PSTN). The term “modem” (which actually stands for “modulator/demodulator") is usually reserved for analog modems, which interface, through a serial transmission connection such as the RS-232 interface, with data terminal equipment (DTE) such as computers. The modem converts the digital sign coming from the computer into an analog signal that can be carried Over a Plain Old Telephone Service (POTS) line. The term “digital modem” is sometimes used for ISDN terminal adapters, but this is something of a misnomer because no signal modulation actually takes place.

Modems generally have two interfaces:

• An RS232 serial transmission interface for Connecting to the DTE, usually the computer
• An RJ-11 telephone interface for connecting to the 4-wire PSTN telephone outlet in the local loop connection
• The USB Modem is a compact external modem that interfaces with computer via a USB port. The modem is ideal for Apple users who own a computer without an internal modem and use a dial-up connection to connect to the internet. The modem can connect at speeds of up to 56 kbps using the V.92 protocol. Its compact form factor makes it ideal for notebook computer Users who find themselves on the road and need to dial-in to an office network or for home users who simply need to add an unobtrusive modem to their computer.

Modem types include the following:

• Internal modems, which are Installed as interface cards inside the computer and might use some of the machine’s CPU processing power for functions such as encoding and data compression.
• External modems, which are generally more expensive and connect to the serial port on the computer using a DB9 or DB25 connector. External modems are useful when several users need to share a modem.
• PCMCIA modems, which are credit-cards-sized modems for laptop computers used by mobile workers.
• Voice/data/fax modems, which can be used for file transfer, sending voice mail using associated software.

Read more

Networking Device | Gateways

Gateway is a broad category of network component that allow communication between different networking architectures and different protocols. Gateways generally operate at the higher levels of the Open Systems Interconnection (OSI) reference model for networking. They are commonly  connectivity between two different protocol stacks that might different systems. Examples include the following:

• E-mail gateways for example, a gateway that receives Simple Mail Transfer Protocol (SMTP) e-mail, translates it into a standard X.400 format, and forwards it to its destination.
• Gateway Service for NetWare acts as a gateway between the Common Internet File System (CIFS) protocol used on Windows networks and the NetWare Core Protocol (NCP) used on NetWare networks. CIFS, formerly known as SMB, is the native file-sharing protocol in Microsoft Windows 2000. When this gateway is enabled, Windows network clients can access NetWare services through the Gateway Service for NetWare gateway located on the Windows 2000 Server.
• Gateways between a Systems Network Architecture (SNA) host and computers on a TCP/IP network, such as the one provided by Microsoft SNA Server.
• A packet assembler/disassembler (PAD) that provides connectivity between a local area network (LAN) and an X.25 packet-switching network.

A gateway is usually a dedicated device or a set of services running on a dedicated computer. Gateways are essentially devices that direct network traffic in some fashion and translate that information.

Read more

Networking Device | Routers

Routers are another type of inter-networking device. As you learned earlier, bridges are primarily used to connect segments of a network. Routers are used to connect separate networks and to access the internet.

Routers provide end-to-end routing by passing data packets and routing traffic between different networks based on network protocol or Layer 3 information. Routers have the ability to make decisions about the best path for delivery of data on the network (like your mobile phone GPS system which help you find the efficient path). The problem of excessive broadcast traffic can be solved by using a router because routers do not forward broadcast frames unless specifically told to do so.

Difference Between Routers and Switches:
Routers differ from bridges in several respects. First, bridging occurs at Layer 2, the data link layer, whereas routing occurs at Layer 3, the network layer of the OSI reference model. Second, bridges use physical or MAC addresses to make data forwarding decisions. Routers use a different addressing scheme that occurs at Layer 3 to make forwarding decisions. They use network-layer addresses, which are referred to as Internet Protocol (IP), or logical addresses, rather than MAC addresses. Because IP addresses are implemented in software and refer to the network a device is located on, sometimes these Layer 3 addresses are referred to as protocol addresses or network addresses. Physical, or MAC, addresses are usually assigned by the NIC manufacturer and are hard-coded into the NIC. IP addresses, on the other hand, are usually assigned by the network administrator.

For routing to be successful, each network must have a unique network number, this unique network number is incorporated into the IP address assigned to each device attached to the network.

Read more

Networking Device | Switches

Switches operate in data-link (Layer-2) layer,which has largely replaced the bridge in the modern network, and which replacing routers in many instances as well. A switch is a box with multiple cable jacks in it that looks a lot like a hub. In fact, some manufacturers have hubs and switches of various sizes that are identical in appearance, except for their markings. The difference between a hub and a switch is that while a hub forwards every incoming packet out through all of its ports, a switch forwards each incoming packet only to the port that provides access to the destination system.

Switches essentially convert the LAN from a shared network medium to a dedicated one If you have a small network that uses a switch instead of a hub, each packet takes a dedicated path from the source computer to the destination, forming a separate collision domain for those two computers. Switches still forward broadcast messages to all of their ports, but not unicasts and multicasts. No systems receive packets destined for other systems, and no collisions occur during unicast transmissions because every pair of computers on the network has what amounts to a dedicated cable segment connecting them. Thus, while a bridge reduces unnecessary traffic congestion on the network, a switch all but eliminates it.

Another advantage of switching is that each pair of computers has the full bandwidth of the network dedicated to it. A standard Ethernet LAN using a hub might have 20 or more computers sharing the same I 0 Mbps of bandwidth. Replace the hub with a switch, and every pair of computers has its own dedicated 10 Mbps channel. This can greatly improve the overall performance of the network without the need for any workstation modifications at all. In addition, some switches provide ports that operate in Full-duplex mode, which means that two computers can send traffic in both directions at the same time using separate wire pairs within the cable. Full-duplex operation can effectively double the throughput of a 10 Mbps network to 20 Mbps.

Read more

Networking Device | Bridges

Bridges operate at Layer 2, the data link layer, of the OSI reference model and are not required to examine upper-layer information. Therefore, a bridge eliminates unnecessary traffic and minimizes the chances of collisions occurring on a network by dividing it into segments and filtering traffic based on the station or MAC address.

Bridges filter network traffic by only looking at the MAC address. Therefore they can rapidly forward traffic representing any network-layer protocol. Because bridges only took at MAC addresses, they are not concerned with protocols. Consequently, bridges are only concerned with passing packets, or not passing packets based on their destination MAC addresses. The following are the important properties of bridges:

In other language,
Bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received.
Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived.

1. They are more intelligent than hubs-that is, they can analyze incoming packets and forward (or drop) them based on addressing information.
2. They collect and pass packets between two network segments.
3. They control broadcasts to the network.
4. They maintain address tables.

Read more

Networking Device | Hubs

On a LAN, every workstation is connected to the network by means of some sort of transmission medium. Usually, each file server has only one NIC. Therefore, it would be impossible to connect every workstation directly to the file servers. To solve this problems, LANs may use hubs, which are common networking devices.

The term hub is used instead of repeater when referring to the device that serves as the center of a network.The following are the most important properties of hubs:

1. They amplify signals.
2. They propagate signals through the network.
3. They do not require filtering.
4. They do not require path determination or switching.
5. They are used as network concentration points.

Hubs can also be understood to be hardware devices that contain multiple independent but connected modules of network equipment.In a LAN, where hubs act as multiport repeaters, they sometimes referred to as a concentrators. In such cases, hubs are used to split the networking media or provide for multiple connections.

The disadvantage of using a hub is that it cannot filter network traffic. Filtering generally refers to a process or device that screens network traffic for certain characteristics, such as source address, destination address, or protocol, and determines whether to forward or discard that traffic based on the established criteria. On a hub, data arriving at one port is sent out on all other ports. Consequently, a hub passes data to all other sections or segments of a network, regardless of whether the data needs to go there or not.

How it's work?

When data enters the hub through any of its ports, the hub amplifies the signal and transmits it out through all of the other ports. This enables a star network to have a shared medium, even though each computer has its own separate cable The hub relays every packet transmitted by any computer on the network to all of the other computers, and amplifies the signals. The maximum segment length for a UTP cable on an Ethernet network is 100 meters. A segment is defined as the distance between two communicating computers. However, because the hub also functions as a repeater, each of the cables connecting a computer to a hub port can be up to 100 meters long, allowing a segment length of up to 200 meters when one hub is inserted in the network.

Read more

Networking Device | Repeaters

Like networking media, repeaters are networking devices that exist at Layer 1, the physical layer, of the OSI reference model.

To begin understanding how a repeater works, it is important to first understand that as data leaves a source and goes out over the network, it is transformed into either electrical or light impulses that pass along the networking media. These impulses are referred to as signals. When signals first leave a transmitting station, they are clean and easily recognizable. However, the longer the cable length, the weaker and more deteriorated the signals become as they pass along the networking media.

For example, specifications for Category 5 twisted-pair Ethernet cable establish the maximum distance that signals can travel along a network as 100 meters. If a signal travels beyond that distance, there is no guarantee that a NIC will be able to read the signal. A repeater can provide a simple solution if this problem exists.

Using Repeaters to increase the Extent of the Network

Repeaters can increase the distance over which a network can extend so that signals will not become unrecognizable to devices receiving them on the network. Repeaters take in weakened signals, clean them up, amplify them and send them on their way along the network, thereby increasing the distance over which a network can operate.

Using Repeaters to Increase the Number of Network Nodes

In networking a common problem is that there are too many devices connected to a network. Signals become weaker and more deteriorated when there are too many devices attached to a network because each device attached to e network causes the signal to degrade slightly. Moreover, because a signal has to pass by too many stations or nodes, it can become so weak that it is unrecognizable to devices receiving it. However, a repeater can provide a simple solution if this problem exists as mentioned in the previous section.

Read more