Wednesday, 3 February 2021

Network Switch

What is Network Switch?

The network switch is a Data Link layer device (Layer 2) and it is an intelligent device. It works with physical addresses that are MAC addresses, fixed bandwidth, flooding, and unicast. It has one broadcast and the number of collision domains depends upon the number of ports and it maintains a MAC table.

External Switch

Types of Switches

  • Manageable switches
  • Unmanageable switches

Manageable switches

On a manageable switch, IP addresses can be assign and configurations can be made. It has a console port and it allows for greater control over it. It allows you to configure and monitor the settings of LAN. Manage switches have some major security benefits, such as the ability to monitor and control the network to shut down active threats and protection for data.

Unmanageable switches

On an Unmanageable switch, IP addresses cannot be assigned, and configuration cannot be made, as there is no console port. It allows plug and plays devices immediately into the network. It allows you to connect Ethernet devices with a fixed configuration in this you can not make any changes. Unmanageable Switches have very basic security. They’re secured by ensuring you have no vulnerabilities from system to system, which accessories like a lockable port cover can ensure no-one is tampering with the device directly.

Difference between Bridge and Switch

Bridge

Switch

Bridges are software based

Switches are hardware based

Bridges have low port density

Switches have high port density

Generally used for connecting two different topology (Segments)

Generally used for connecting single topology (Segment)

Switching Modes

Switching modes are used for forwarding packets in different modes and different parts of the frame such as source MAC address, destination MAC address, user's data, preamble, and frame check sequence (FCS). There are three types of switching modes.

Types of Switching Modes

  1. Store and Forward
  2. Fragment Free
  3. Cut Through

Store and Forward

It is a telecommunication technique, where information is store in a buffer until the entire frame has arrived and then forward later to the destination or intermediate stations.

  • A default switching method for distribution layer switches
  • Latency- High
  • Error Checking – Yes

Store and Forward Flow Chart

Fragment Free

It is a technique, where it partially addresses the problem by assuring that collision fragments are not forwarded. It holds the frame until the first 64 bytes are read from the source to detect a collision before forwarding. This is only useful if there is a chance of a collision on the source port.

  • It is also refer to as Modified Cut-Through
  • A default switching method for access layer switches.
  • Latency – Medium
Error Checking – 64 bytes of frame

Fragment free Flow Chart


Cut-Through

It is a method for packet switching systems, wherein the switch starts forwarding a frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed. It is uses in Ethernet because the frame check sequence appears at the end of the frame, the switch is not able to verify the integrity of an incoming packet before forwarding it. A cut-through switch will forward corrupted packets, whereas a store and the forward switch will drop them.

Cut Through Flow Chart

CRC - Cyclic Redundancy Check

What is Latency?

Latency is the total time taken for a Frame to pass through the switch. Latency depends on the switching mode and the hardware capabilities of the switch.

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