An overview of active components in an IP Network

This article gives an overview of the most popular active components in an IP Network – The Network Switches and Routers. This article discusses why they are exciting in a network, what is their use, how and where they are deployed and an outline of the features supported by them. 

Why are network switches and Routers exciting?

¤ A network switch connects the various devices within a LAN network so that they could communicate between each other and share the network resources between them.
¤ A router on the other hand, connects disparate networks so that devices from one network can share data and information with the devices from another network. For example, router connects the devices from a LAN network within an organization to a WAN network (eg. Internet) outside the organization.

An overview of Network Switches:

A network switch is a hardware device with various LAN ports that joins/connects multiple computers and network peripherals within a Local Area Network (LAN).

Switches work on Layer 2 and some of them can work on Layer 3 also.

Computers and other devices from a network can connect with a switch at a specific bandwidth available with the switch (and supported by the passive components). Common switches connect at 10 Mbps/ 100 Mbps/ 1000 Mbps – one of these three speeds and they auto negotiate between them and the computers to connect at the best speeds possible. Switches are shared resources and the bandwidth reduces as the number of concurrent connections to the switch increases.

Common switches come with 4/8/12/16/24/48 Ports and they can be cascaded with one another (they can be stacked one over another to form a very big switch).

Some switches support POE (Power over Ethernet) in some of its ports or all the ports so that POE enabled devices like IP Phones, Wireless Access Points etc. can get both data and power(electrical) through the same port/cable that they connect to the network switch.

Some switches enable VLAN – Virtual LAN to be created with its ports so that a group of the ports are designated as separate network and is isolated from another group of ports. This is required to reduce the loss of bandwidth due to continuous broadcasting from certain network devices and also for security – as users from one network cannot access the other.

Switches also support SNMP (Simple Network Management Protocol) in order to view the network statistics as seen by the switch like link status of each port, the volume of traffic received by each port, errors in each port if any etc.

An overview of Router:

A router is a device that forwards network traffic (data packets) among disparate networks. A router is in between two networks like LAN-LAN or LAN-WAN or LAN-Internet etc. and connect the users and devices of one network to another. It also makes sure that the traffic that is not meant to a device within a network does not get into the network. Sometimes, it also performs the translations of different protocols between two networks.

Router functions in the Layer-3 of the OSI model and some switches can also do the functions of a Router.

Routers use IP header information (where the source address and destination address are specified) and routing tables to determine the best path to forward the packets. They also sometimes communicate between them to find out the best possible route between any two hosts using protocols like ICMP. A routing table contains information like which connections lead to particular group of addresses and priorities and rules to be used for the connection.

Typically, a router in an organization is used to connect the LAN with the internet connection provided by the ISP. It has an IP network interface where the leased lines/VPN connections from the service provider can be terminated, it has a ISDN connectivity for connecting an ISDN line from telecom provider for a backup to the IP Leased lines, additionally it may also have PRI/TI and some specialized ports for different types of connectivity.

Routers prevent the traffic moving moving from one computer to another within the LAN network from going outside the network and also prevents the traffic which is not intended to reach the particular network from entering into the network. It can also be configured to enable security settings to prevent some attacks like Denial of Service (DOS) attacks.

You can also have a look at a more recent post of mine on active and passive components of a computer network with an architecture diagram in this link.