A network interface card (NIC) is a circuit board or card that is installed in a computer so that it can be connected to a network. A network interface card provides the computer with a dedicated, fulltime connection to a network.
Personal computers and workstations on a local area network ( LAN ) typically contain a network interface card specifically designed for the LAN transmission technology.

A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing.
When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s. Technically, transceivers must combine a significant amount of the transmitter and receiver handling circuitry e.g. transponders, transverters, and repeaters.

100BASE-TX to 100BASE-FX transceiver

In telecommunications, a repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances. It is a generic term that refers to several different types of devices
– a telephone repeater is an amplifier in a telephone line
– an optical repeater is an optoelectronic circuit that amplifies the light beam in a optical fibre cable
– a radio repeater is a radio receiver and transmitter that retransmits a radio signal.
– A broadcast relay station performs an analogous role in broadcast radio and television.

A broadcast relay station performs an analogous role in broadcast radio and television

• In general, a hub is the central part of a wheel where the spokes come together.
• It is common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

• An Ethernet hub, active hub, network hub, repeater
hub, multiport repeater, or simply hub is a device for connecting multiple Ethernet devices together and making them act as a single network segment.
• It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the physical layer(layer 1) of the OSI model.
• Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision. In addition to standard 8P8C ("RJ45") ports, some hubs may also come with a BNC or Attachment
Unit Interface (AUI) connector to allow connection to legacy 10BASE2 or 10BASE5 network segments.

What Hubs Do
• Hubs and switches serve as a central connection for all of your network equipment and handles a data type known as frames. Frames carry your data. When a frame is received, it is amplified and then transmitted on to the port of the destination PC.
• In a hub, a frame is passed along or "broadcast" to every one of its ports. It doesn't matter that the frame is only destined for one port.
• The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination.
• This places a lot of traffic on the network and can lead to poor network response times.

• As a network product, a hub may include a group of modem cards for dial-in users, a gateway card for connections to a local area network (for example, an Ethernet or a token ring), and a connection to a line.

• In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street.
• A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).
• A network bridge is a network device that connects multiple network segments. In the OSI model, bridging is performed in the first two layers, below the network layer. There are four types of network bridging technologies:
– simple bridging,
– Multiport bridging,
– learning or transparent bridging, and
– source route bridging.

• A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect.
• Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as RIP, BGP, ICMP to communicate with each other and configure the best route between any two hosts.

• A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node
• A routing table is a set of rules, often viewed in
table format, that is used to determine where data packets travelling over an Internet Protocol (IP) network will be directed. All IP-enabled devices, including routers and switches, use routing tables.

Avaya ERS 8600 Router

Types of Routers
There are several types of routers in the market.
• Broadband Routers
• Broadband routers can do different types of things. Broadband routers can be used to connect computers or to connect to the Internet.
• If you connect to the internet through phone and using Voice over IP technology (VOIP) then you need broadband router.
These are often a special type of modem (ADSL) that will have both Ethernet and phone jacks.
• Wireless Routers
• Wireless routers create a wireless signal in your home or office. So, any PC within range of Wireless routers can connect it and use your Internet.
• In order to secure your Wireless routers, you simply need to come secure it with password or get your IP address. Then, you'll log on into your router with the user ID and passwords will that come with your router.
Other Type of Router
• Edge Router
• This type of router are placed at the edge of the ISP network, the are normally configured to external protocol like BGP
(Border gateway protocol) to another BGP of other ISP or large organisation.
• Subscriber Edge Router
• This type of router belongs to an end user (enterprise) organization. It’s configured to broadcast external BGP to it’s provider’s AS(s)
• Inter-provider Border Router
• This type of router is for Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers' ASes.
• Core Router
• A router that resides within the middle or backbone of the LAN network rather than at its periphery. In some instances , a core router provides a stepdown backbone , interconnecting the distribution routers from multiple building of a campus (
LAN), or Large enterprise Location (WAN). They tend to be optimized for a high brandwidth.

• CISCO
• AVAYA
• SIEMENS
• HEWLET PACKARD
• NETGEAR
• D-LINK
• SONY
• DELL
• INTEL
• APPLE
• INTRASYS
• HUWAI
• ASUS
Wireless Routers
• LINKSYS
• ASUS
• NETGEAR
• APPLE
• TP-LINK
• D-LINK
• INTEL
• IBM
• DELL
• TOSHIBA
• SIEMENS

• A router is connected to two or more data lines from different networks (as opposed to a network switch, which connects data lines from one single network).
• When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.

• A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host
(end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes.
• In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.

• When the networks that must be connected are using completely different protocols from each other, a powerful and intelligent device called a gateway is used.
• A gateway is a device that can interpret and translate the different protocols that are used on two distinct networks.
• Gateways comprise of software, dedicated hardware or a combination of both. Gateway operate through all the seven layers of the OSI model.
• A gateway can actually convert data so that it works with an application on a compute on the other side of the gateway e.g. a gateway can receive e-mail message in one format and convert them into another format.
• Gateways can connect systems with different communication protocols, languages and architecture. For example, IBM networks using Systems
Network Architecture (SNA) can be connected to LANs using a gateway.

Types of Gateways
• Host Gateways
• LAN Gateways
• Electronic Mail Gateways
• Firewall
• Proxy servers
• NAT (Network Address Translation)
• Voice/Media Gateways
• Payment gateway

• A switch is a device which provides bridging functionally with greater efficiency. A switch acts as a multiport bridge to connect devices or segments in a LAN.
• Switch enables dedicated access
• Eliminates collisions and increases capacity
• Supports multiple conversations at the same time
• The switch has a buffer for each link to which it is connected.
When it receives a packet, it stores the packet in the buffer of the receiving link and checks the address to find the outgoing link.

• If the outgoing link is free, the switch sends the frame to that particular link.
• Switches are of two types :
1. Store and forward switch
2. Cut – through switch
• A store – and – forward switch stores the frame in the input buffer until the whole packet has arrived.
• A cut-through switch, forwards the packet to the output buffer as soon as the destination address is received.

• Concept of a switch is shown in Figure. As shown in the Figure a frame arrives at port 2 and is stored in the buffer.
• The CPU and the control unit, using the information in the frame consult the switching table to find the output port. The frame is then sent to port 5 for transmission.
• Routing switches use the network layer destination address to find the output link to which the packet should be forwarded.

• The switches can be of two types namely the layer two switches (L2) and the layer three(L3) switches.
• A two layer switch performs at the physical and data link layer.
• The two layer switch is basically a bridge . It has many ports and it is designed to allow better performance.
• A bridge with few ports can connect a few LANs together. But a bridge with many ports will be able to allocate a unique port to each station. Thus each station will have its own separate identity.
• Therefore there is no competing traffic and so there are no collisions.

• Traditional network switches operate at Layer 2 of the OSI model while network routers operate at Layer 3. This often leads to confusion over the definition and purpose of a Layer 3 switch.
• A Layer 3 switch is a specialized hardware device used in network routing. Layer 3 switches technically share much in common with traditional routers. Both can support the same routing protocols .
Both inspect incoming packets and make dynamic routing decisions based on the source and destination addresses inside.
• Both types of boxes share a similar physical appearance.
• Purpose of Layer 3 Switches
• Layer 3 switches were conceived as a technology to improve network routing performance on large local area networks
(LANs) like corporate intranets or VLANs
• The key difference between Layer 3 switches and routers lies in the hardware internals.

• A switch works at Layer 2 of the OSI model
(data-link). It is a LAN device that can also be called a multi-port bridge. A switch switches
Ethernet frames between Ethernet devices.
Switches do not care about IP addresses nor do they even examine IP addresses as the frames flow through the switch. However, unlike a hub that just duplicates data and sends it out all ports, switches keep a bridge forwarding table that shows what MAC addresses have been seen on what port.

• A Layer 3 switch works much like a router because it has the same IP routing table for lookups and it forms a broadcast domain. However, the "switch" part of
"Layer 3 switch" is there because:
• The layer 3 switch looks like a switch. It has 24+
Ethernet ports and no WAN interfaces.
• The layer 3 switch will act like a switch when it is connecting devices that are on the same network.
• The layer 3 switch is the same as a switch with the router's IP routing intelligence built in.
• The switch works very quickly to switch or route the packets it is sent.
• In other words, the Layer 3 switch is really like a highspeed router without the WAN connectivity.

Sr
No
Hub Switch
1 It is a broadcast device.
It is a point to point device.
2 It operates at physical layer. It operates at datalink layer.
3 It is not an intelligent device.
4 It simply broadcasts the incoming packet.
It is an intelligent device.
It uses switching table to find the correct destination.
5 It cannot be used as a repeater.
It can be used as a repeater.
6 Not a sophisticated device.
It is a sophisticated device.
7 Not very costly.
Costly.

• It is a device which is used to connect two different networking media. For example connection between a shielded cable and twisted pair can be achieved through the media converter.
• Figure shows the media converter.
• Various functions performed by a media converter are as follows :
• Connect two different types of wiring systems without adding to the repeater count.
• Connect two 10 Base T or 100 Base TX networks in different buildings using fiber-optic cable.
• To integrate a mix of cabling which includes UTP cabling, thin net fiber optic cable, thick net etc.

• A firewall is a system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both.
• In computing, a firewall is a network securitysystem that monitors and controls the incoming and outgoing network traffic based on predetermined security rules.
• Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Sr.
No.
Parameter Router
1 Layer in OSI model Network layer
2 Operation Connect two more network or
Bridge
Physical or data link
Regeneration, check
MAC address
3 Types Distance vector, Link state
Transparent,
Routing
4 Principle of working Uses hardware and software
5 Used for Connecting networks
Uses tables relating the addresses and ports
Connecting computers