VLAN Trunking Protocol is used by Cisco switches to exchange VLAN information. In VTP, synchronization of VLAN information, such as VLAN ID or VLAN name can be done with switches inside the same VTP domain.

VTP domain is a group of trunked switches with the matching VTP settings such as domain name, password and VTP version. All switches present in the same VTP domain share their VLAN information with each other.

For better understanding of VTP, consider an example network with 50 switches. Without VTP, if we want to create a VLAN on each switch, you should manually enter VLAN configuration commands on every switch. But when comes to VTP, it enables you to create the VLAN only on a single switch. That Particular switch can propagate information about the VLAN to every other switch on the network and cause other switches to create it. Similarly, if we delete a VLAN, the change is automatically transmitted to every other switch inside the same domain.

VTP share VLANs information through VTP messages. VTP messages can only be transmitted through the trunk connections. So we need to establish trunk connection between switches. VTP messages are transmitted as layer 2 multicast frames.VTP does not publicize information about which switch ports are assigned to which VLAN.

Related – VDC vs VLAN

VLAN Trunking Protocol VERSIONS:

There are three versions in VTP

• Version 1
• Version 2
• Version 3

Among the three, Version 3 is most popular and has following features –

• Enhanced authentication
• Support for extended VLANs (1006 to 4094). It also support for private VLAN
• VTP mode off that disables VTP
• Backward compatibility with VTP V1 and V2

VLAN Trunking Protocol (VTP) MODES:

VTP can be configured in four different modes

1. VTP Server Mode
2. VTP Client Mode
3. VTP Transparent Mode
4. VTP Off Mode

VTP Server Mode:

• VLANs can be created, modified, and deleted in VTP server and configuration parameters, such as VTP version and VTP pruning can also be specified for the entire VTP domain.
• VTP servers publicize their VLAN configuration to other switches in the same VTP domain and synchronize their VLAN configuration with other switches based on advertisements received over trunk links.
• VTP server is the default mode.
• Saves Configuration in NVRAM

VTP Client Mode:

• VTP clients are similar to the VTP servers. The only difference is that we cannot create, change, or delete VLANs on a VTP client.
• Doesn’t save Configuration in NVRAM

VTP Transparent Mode:

• VTP transparent switches do not take part in VTP.
• VTP transparent switch does not publicize its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements, but transparent switches forward VTP advertisements that they receive from trunk ports.
• In addition to supporting private VLANs in client and server modes, VTP version 3 also supports creating extended-range VLANs in client or server mode

VTP Off Mode:

It is similar to the transparent mode. The only difference is that a switch using this mode will not forward received VTP updates. It is supported only in VTP Version3.

Configuration Revision Number:

• Vlan Trunking Protocol switches use a pointer called the VTP configuration Revision Number to notify the most recent information.
• Configuration revision number is zero (0) when VTP advertisement process starts.
• When modification is made on a VTP server, the revision number is incremented by one before the advertisement is sent.

How to add a new switch into the existing VLAN Trunking Protocol Domain

• While adding a switch to an existing VTP domain, make sure that the switch VTP Revision number is 0 before adding it to a network.
• Reform the switches VTP mode to transparent and then change the mode back to server.
• VTP domain name should be changed to a fake name (a nonexistent vtp domain), and then change the VTP domain back to original name.
• Remove the Vlan .Dat file inside the flash and reload it.

VLAN Trunking Protocol (VTP) CONFIGURATION

There are some prerequisites for VTP to transmit VLAN information between switches.

• Switches which are to be VTP configured should be with the same domain name and same version.
• There must be one server switch among the switches.
• Authentications like Password should match if applied.

Below is a sample lab setup showcasing VTP Server, Client and transparent mode for Switch1, Switch2 and Switch3 respectively.

Configuration of VTP Server Mode in Switch 1

Configuration of VTP Client Mode in Switch 2

Configuration of VTP Transparent Mode in Switch 3

Below is the VTP mode after configuring the mode as server in Switch1.   

Below is the  information of VTP mode after configuring the mode as client in Switch2.

Below is the information of VTP mode after configuring the mode as transparent in Switch3.

VLAN 10 & VLAN 20 configuration on switch 1.

Showing the information about VLANs in Switch 1 use “show vlan brief” command.

Showing the information about VLANs in Switch 2.

Note: As per the output, VLAN 10 & VLAN 20 are created in switch 1. Henceforth, VLAN 10 & VLAN 20 are also created in Switch2 by automatically (by VTP) because Switch 1 is VTP server, Switch 2 is VTP Client.

Information about VLAN 10 & VLAN 20 in Switch 3.

Note: As per the output, no VLANs are created automatically in switch 3, because Switch 3 is VTP transparent.

Related – VTP Interview Q&A

Before understanding Message Switching, let’s explore the basic types of switching.

Switching is an important mechanism that provides communication between different networks or different computer(s) and manages the data flow between the two end points. There are three types of switching techniques –

• Circuit switching
• Packet switching
• Message switching.

For Details – Network Switching & its Types

Here we will discuss Message Switching.

Message Switching

It is a switching method that was developed as an alternative to Circuit switching before the advent of Packet Switching. Message switching is a connectionless technique in which the entire message is routed from the source node to the destination node by one hop at a time, called hop-by-hop system. The distinctive features of message switching are:

Store and Forward network: The message is not discarded in case of non availability of the next hop. Rather, it is stored in a queue  and is  retransmitted when the required route is available .This is called store and forward network.

Message delivery: The entire information is wrapped in a single message and transferred from the source to the destination node as a “message” with a definite destination address in the header.

The Process of Message Switching

In Message switching, each message is regarded as an individual unit. Destination address is added to the message by the sender node and the message is delivered entirely to the next available intermediate switching node. The intermediate node stores the message and after doing the requisite checks like destination address, transmission errors etc. , delivers the message to the next available intermediate node. The process continues with the store and forward technique until the message reaches its destination.

Below diagram represents the delivery of two separate messages, MSG1 and MSG2 from the same source using different routes to reach the same destination ( Message Switching) −

Advantages

• As the communication channels are shared by the network devices, it ensures better bandwidth usage.
• It helps in reducing the network congestion due to store and forward method. Switching nodes can store the messages incase of unavailability of the communication channel, thus helping in reducing the traffic congestion.
• It can send messages of unlimited sizes.
• Out of order packets or lost packets does not affect Message Switching unlike Packet Switching.
• The transfer rate of the sender and the receiver need not to be the same as the message can be stored by the nodes.

Disadvantages

• Each intermediate switching node requires large storage capacity as the message is to stored at each intermediate node.
• This Store and forward method also causes delay, rendering it unsuitable for real time applications like video conferences.

FAQs Related to the Topic

• What is the difference between Message Switching and Packet Switching ?
• In message switching, a complete message is passed across the network, while in packet switching it is broken into units called packets.
• Which switching technique can be used in real time, Circuit Switching or message Switching
• Circuit Switching can be used in real–time as the communication channel is dedicated which ensures a steady rate of data transfer essential for real time applications. Message Switching is not suitable for real time applications as its store-and-forward technique causes delay.
• What is the difference between Message Switching and Circuit Switching?
• In Circuit Switching, a dedicated physical connection is established between two devices while in message switching is a connectionless switching techniques based on store and forward mechanism.
• Where is Message Switching used?
• Message switching is used for electronic mail and telex transmission. However, majority of message switching links have been replaced by packet/circuit switching.
• What are the key features of Message Switching?
• The key features of message switching are: store-and-forward mechanism and hop-by-hop system.

To explore more questions related to Network Switching, please read our e-book on Switching Interview Q&A

MD5 and CRC are 2 of most commonly used hashing algorithms, infact while comparing files and including other use cases. In this article. We will understand both the concepts of hashing algorithm and how one scores over the other.

Errors and Error detection

When bits are transmitted over the physical media, they get corrupted due to interference and network problems. The corrupted bits changes from 0 to 1 or 1 to 0, data being received by the receiver and are called errors.

Error detection techniques are responsible for checking any error has occurred or not in the frame that has been transmitted.

In this error detection technique the sender needs to send some additional bits along with the data bits. The receiver will check based upon the additional redundant bits. If it finds data is identical, it removes the redundant bits and pass the message to the upper layers.

There are three main categories for detecting errors:

Cyclic redundancy check (CRC)

• CRC is based on binary division.
• In CRC, a sequence of redundant bits, known as cyclic redundancy check bits, are appended to the tip information of knowledge of information unit so the ensuing data unit becomes precisely dividable.
• At the destination, the incoming information unit is split by identical variety. In this step there is no remainder, the data unit is assumed to be correct and therefore accepted.
• A remainder indicates that the info unit has been broken in transit and so should be rejected.

Steps Involved

Error detection victimization CRC technique involves below enlisted steps-

Step-01: Calculation of CRC at Sender Side

At sender side,

• A string of n 0’s is appended to the info unit to be transmitted.
• Here, n is one but the amount of bits in CRC generator.
• After division, the rest therefore obtained is termed as CRC.
• It may be noted that CRC additionally consists of n bits.

Step-02: Appending CRC to Data Unit

At sender side,

• The CRC is obtained once the binary division.
• The string of n 0’s appended to the info unit earlier is replaced by the CRC remainder.

Step-03: Transmission to Receiver

The fresh fashioned code word (Original information CRC) is transmitted to the receiver.

Step-04: Checking at Receiver Side

At receiver side,

• The received code word is divided with identical CRC generator.
• After division remainder will check.

The following two cases are possible- 

If remainder is zero meaning no error receiver accepts the info. If remainder is none zero receiver reject information it suggests that some error occurred.

Introduction to MD5 Algorithm

The MD5 hash function was originally designed for use as a secure cryptographic hash algorithm for authenticating digital signature, data integrity and detect unintentional data corruption.

MD5 message digest algorithmic program is the fifth version of the Message Digest algorithmic program, that developed by Ron Rivest to provide 128 bit message digest. MD5 produces the message that is digest through 5 steps i.e. padding, append length and divide input into 512 bit blocks.

How does the MD5 Algorithm works?

MD5 produces output of 128-bit hash. This secret writing of input of any size into hash values undergoes five steps and every step has it’s a predefined task.

Step1: Append Padding Bits

• Padding suggests that adding additional bits to the initial message. Therefore in MD5 original message is cushiony such its length in bits is congruent to 448 modulo 512.

Overall bits are sixty four less being a multiple of 512 bits length. Padding is finished, though the length of the initial message is already congruent to 448 modulo 512.

• Padding is done even if the length of the original message is already congruent to 448 modulo 512. In padding bits, the only first bit is 1 and the rest of the bits are 0.

Step 2: Append Length

After padding, 64 bits are inserted at the end which is used to record the length of the original input. Modulo 2^64.

Step 3: Initialize MD buffer

A four-word buffer (A, B, C, D) is employed to reason the values for the message digest.

Here A, B, C, D are 32- bit registers and are initialized within the following means.

Step 4: Processing message in 16-word block

MD5 uses the auxiliary functions that take the input as 3 32-bit variety and produces a 32-bit output and these functions use logical operators like OR, XOR, NOR.

The content of 4 buffers are mixed with the input auxiliary buffer and sixteen rounds are performed victimization sixteen basic operations.

Output

Buffer A, B, C, D contains the MD5 output beginning with lower bit A and ending with higher bit D.

Example
Input: This is an article about the cryptography algorithm
Output: e4d909c290dfb1ca068ffaddd22cbb0

Key Highlights CRC Vs MD5

• It performs at data link layer and transmission layer of OSI model. It checks sequence of redundant bits at sender and receiver side. If remainder is zero then no error if non-zero then some error.
• MD5 is 128 bit hash algorithm to generate password. It is easy to generate and compare hash value.

Virtualization in IT systems has helped Network estate immensely. 2 technologies which have helped networking across various segments are VLAN and VDC. While VLAN is short for Virtual Local Area Network, VDC means Virtual device contexts. VLAN divides the network into separate logical areas at the Layer 2 level and each VLAN is considered an individual broadcast domain. VDCs allows the switches to virtualize physical chassis.

In VLAN, unicast, broadcast and multicast packets are forwarded and flooded only to end stations in that VLAN. VLAN is considered a logical network and packets destined for stations that do not belong to the same VLAN (different subnet) must be forwarded through a router or Layer 3 device or entity.

VDC, presents itself as a unique device to connected users within the framework of that physical switch. VDC behaves as a separate logical entity within the switch, maintaining its own unique set of running software processes/configuration.

Virtual Device Contexts (VDCs)

The NX-OS supports Virtual Device Contexts (VDCs) feature, allowing the partitioning of a single physical Nexus 7000/7700 device into multiple logical devices i.e. Separate Management plane, Data plane and Control plane. This logical separation provides the following benefits:

• Administrative and management separation.
• Failure domain isolation from other VDCs.
• Address, VLAN, VRF, and VPC isolation.

Resource that can be shared in VDC –

• Single instance of the kernel which supports all of the processes and VDC.
• Hardware which can be shared i.e. Supervisor modules, Fabric modules, Power supplies, Fan trays, CMP, CoPP and hardware SPAN resources.

Resource that cannot be shared in VDC –

• CPU, Memory, TCAM Resources such as the FIB, QoS, and Security ACL.
• L2 Protocol i.e. VLAN, STP, LACP, UDLD and others.
• L3 Protocol i.e. Routing, VRF, PIM, SNMP and others.

VDC License requirement

To Create VDC, an advance license is required on Nexus switch. License is associated with serial number of chassis. Cisco provide 120 days grace period for trial.

Number of VDCs supported –

Number of VDC support depends on supervisor engine in Nexus chassis.

• Nexus 7000 Supervisor 1 supports 4 VDCs.

• Nexus 7000 Supervisor 2 supports 4+1 admin VDCs.
• Nexus 7000 Supervisor 2E supports 8+1 admin VDCs.
• Nexus 7700 Supervisor 2E supports 8+1 admin VDCs.
• Nexus 7700 Supervisor 3E supports 8+1 admin VDCs.

Types of VDC

Default VDC – VDC1 is said to be default. It is used for management of all VDC in Nexus. At first login in nexus switch user will be in default VDC. Default VDC is created by NX-OS boot up. In Default VDC, we can create/update/delete other non-default VDCs and allocate resources such as interface, memory to non-default VDC.

Admin VDC – It is created from initial configuration wizard. No resources is allocated to Admin VDC since it is not made to handle user data traffic. It is used for managing other VDCs and nexus chassis.  Default VDC has been replaced with Admin VDC in SUP2/SUP2E with NX-OS 6.1. Default and Admin VDC cannot exist at the same time. VDC 1 can be either configured as default or Admin. We can convert to admin VDC by using this command #System admin VDC.

Non-Default VDC – It can be created from Admin or Default VDC. Changes made on non-default VDC does not affect other VDCs. Each VDC have its own configuration file. Non-default VDC is used to handle user data traffic as interfaces can be allocated to it.

Storage VDC, It is used when SAN function is implemented in Nexus. Two different types of interfaces are assigned ie FCOE and shared interface.

Creating VDC

Hostname#conf t

Hostname(config)#vdc  (name) > Creates a VDC and enters the VDC configuration mode.

Hostname(config-vdc)#allocate interface ethernet slot/port > Allocates one interface to the VDC.

Initializing VDC

Hostname#switchto vdc vdc-name  > Switches to the VDC.

Hostname-NewVDC#show vdc current-vdc > Displays the current VDC number.

Verifying VDC

Hostname#show running-config {vdc | vdc-all} > Displays the VDC information in the running configuration.

Hostname#show vdc [vdc-name] > Displays the VDC configuration information.

Hostname#show vdc detail > Displays the detailed information about many VDC parameters.

Hostname#show vdc current-vdc > Displays the current VDC number.

Hostname#show vdc membership [status] > Displays the VDC interface membership information.

Hostname#show resource > Displays the VDC resource configuration for the current VDC.

Related – VDC vs VRF

Virtual Local Area Network (VLAN)

Virtual LAN (VLAN), divides the network logically on layer 2 (data link layer). VLANs also divide broadcast domain. It allows hosts to be grouped in a same broadcast domain even if they are not connected to the same switch. Two types of VLAN membership methods are Static and Dynamic.

In a Static VLAN, VLAN is manually created and then VLAN is assigned to respective switch ports. It is also called port-based VLAN. The port association with the VLAN does not change until the administrator changes the port assignment. End user device becomes the member of VLAN based on the physical switch port to which they are connected.

In a Dynamic VLAN, when a port is configured as dynamic, it receives VLAN information from VMPS server based on the MAC address. It reduces overhead of network administrator. When a workstation is connected to a switch port the switch queries a database to establish VLAN membership. VLAN database of a VLAN Membership Policy Server (VMPS) server is updated by administrator.

VLAN ranges

• VLAN 0, 4095: Reserved range.
• VLAN 1: Default or native VLAN of switches. By default, all switch ports are assigned in VLAN 1. This VLAN cannot be deleted/modified.
• VLAN 2 – 1001: Normal VLAN range. We can create/modify/delete these VLANs.
• VLAN 1002 – 1005: Reserved for FDDI and token rings. These VLAN can’t be deleted.
• VLAN 1006 – 4094: Extended range of VLAN.

Functions of VLAN

1. VLANs increases the number of broadcast domains possible in a LAN by grouping various hosts with similar functions.
2. Virtual LANs provide mechanism for making logical groups of end devices, though they are on different networks.
3. Implementing VLANs reduces the security risks significantly, as the number of hosts connected on a broadcast domain decreases. This is done by configuring a separate VLAN for only the hosts with the sensitive information.
4. VLAN offers flexible networking models which group different users based on their departments (job/function), rather than just physical locations of that network.
5. Changing users/hosts on a VLAN is easy. All it needs is a new port level configuration. If a user wants to move from one VLAN to another, a new port needs to be configured on the desired VLAN.

Related – VLAN Interview Questions

Comparison

1. A VDC virtualizes the device itself by segregating a single physical device into multiple logical devices. In case of VLAN, network is divided in a network switch on Layer 2 network.
2. VDCs have Separate Administrative and management domains. In VLAN, we have separate broadcast domains.
3. VDC feature is available on Nexus 7K only. In case of VLAN, this feature is available on every switch.
4. Advance Services License is required to enable VDC feature set. VLAN doesn’t require any License to be enabled.
5. An external connection needs to be made between ports of VDC to perform internal VDC (VDC to VDC) communication. In VLAN, SVI needs to be created to communicate between different network subnet.

VDC vs VLAN: Comparison Table

S.no.	VDC	VLAN
1	A VDC virtualizes the device by segregating a single physical device as multiple logical devices.	A VLAN divides network in a network switch.
2	Separate Administrative and management domains for each VDC.	VLANs have separate broadcast domain.
3	Feature available on Nexus 7K only.	VLAN feature is available on every switch.
4	Advance Services License required to enable VDC.	VLAN doesn’t require any License to be enabled
5	An external connection needs to be made between ports of VDC to perform internal VDC (VDC to VDC) communication.	VLAN SVI needs to be created to communicate between different network subnet.
6	Used in case of multi-tenant environment or when separate security Zone are required	Used to limit broadcasts and when multiple department or groups with separate security control
7	Scope limited to Data Center environment	Scope is very wide and VLANs can be seen in Data Centers, small to large offices and even Service provider networks.

Conclusion

Both VDCs and VLANs are an integral part of a LAN network, and IT solutions would be incomplete without using atleast one of them. Virtualization is used by both discussed concepts where VDC came to fore pretty recently, VLAN has been there for quite long. VDC divides the physical chassis into multiple logical chassis, whereas VLAN divides physical switch network into logical parts.

Download the difference table here.

All devices part of a network can connect and communicate with each other. However, when we try to put logic around the communication between these devices, the key query that always arises in our mind that how one device will uniquely identify and send data to the other device in the network. This can be possible only with the help of the MAC and IP addresses. MAC address is assigned to the NIC card by the manufacturer. IP address is a number assigned to the workstation’s NIC in a network.

We will follow below key sections during the course of this post to illustrate on MAC address and IP Address –

1. Definition
2. Key Differences
3. Comparison Chart
4. Conclusion

Definition

What is MAC Address?

MAC (Media Access Control) address uniquely defines a hardware interface called MAC Address. MAC address is unique and assigned by the manufacturer and is programmed in the ROM of network interface card (NIC). MAC address is a 48-bit hexadecimal address. The format of a MAC address is xx:xx:xx:yy:yy:yy, where xx:xx:xx is a 3-byte address of the manufacturer. On the other hand, yy:yy:yy is a serial number of NIC card. Notable is that MAC address will change if NIC is replaced. MAC address works at the data link layer of OSI model. ARP (Address Resolution Protocol) is a protocol which does IP to MAC address mapping and henceforth is used to get MAC address of a device.

What is IP Address?

Internet Protocol (IP) address is an address which is allocated to every single computer. It is an address that is used to classify every node in the network. IP address provides the network node a location, so that it can connect with other nodes or networks. IP address is 32 bit, Version four of IP protocol. A newer version is IPv6 and it is 128 bit. IP address can be statically and dynamically assigned to a device.

• Static IP address – This will never change, and can be considered a perpetual internet address.
• Dynamic IP address – This is a provisional address that is allocated each time a computer or device connects to the network.

IPv4(Internet Protocol Version 4): IPv4 is a 32-bits address. This address is available in decimal form along with dots (.) in between. For Example – 192.168.1.1. The header field of the IPv4 is 20 bytes, and the checksum bits are present in the header for error control. The IPsec support (for security feature) is optional in IPv4. It supports a datagram up to size 576 bytes. The IPv4 addressing can be used for Multicasting and Broadcasting the data packets.

IPv6(Internet Protocol Version 6): IPv6 is a 128-bits address. This address is available in hexadecimal form along with semi-colons(:) in between. For Example: 2FFE:F300:0213:AB01:0132:7289:2134:ABDC. The header field of the IPv6 is 40 bytes, but the checksum bits are not present in the header file. The IPsec support (for security feature) is mandatory in IPv6. It supports a packet size of up to 1280 bytes. The IPv6 addressing can not be used for broadcasting.

Related – IPv4 vs IPv6

IP address classes

• Class A 0.0.1 to 126.255.255.254
• Class B 1.0.1 to 191.255.255.254
• Class C 0.1.1 to 223.255.254.254
• Class D 0.0.0 to 239.255.255.255. It is reserved for multicast groups.
• Class E 240.0.0.0 to 254.255.255.254. It is reserved for future use, or research and development purposes.

Key Differences

• MAC address uniquely identifies a device, whereas an IP address uniquely defines a device connection to a network.
• MAC address is 48 bit long hexadecimal whereas IP address has two versions, IPv4 a 32-bit address and IPv6 a 128-bit address.
• MAC address is assigned by the manufacturer. On the other hand, IP address is assigned by the network administrator.
• ARP obtains MAC address whereas RARP obtains IP address.
• MAC Address operates in the data link layer whereas IP Address operates in the network layer.
• MAC Address of computer cannot be changed with time and environment whereas IIP Address modifies with the time and environment.
• MAC Address can’t be found easily by third party whereas IP Address can be found by third party.

Comparison Table : MAC Address vs IP Address

S.No.	MAC ADDRESS	IP ADDRESS
1	MAC Address is a 6 byte hexadecimal address.	IP Address is either 4 byte (IPv4) or 6 byte (IPv6) address.
2	ARP is used to get MAC address of device.	RARP used to get IP of device.
3	NIC Card’s Manufacturer provides the MAC Address.	Network administrator or Internet Service Provider (ISP) provides IP address.
4	MAC Address is the physical address of computer.	IP Address is the logical address of the computer.
5	MAC Address operates in the data link layer of OSI model.	IP Address operates in the network layer of OSI model.
6	MAC Address helps in simply identifying the device.	IP Address identifies the connection of the device on the network.
7	MAC Address of computer cannot be changed with time and environment to it is fixed.	IP Address modifies with the time and environment and it is not fixed.
8	MAC Address can’t be found by third party.	IP Address can be found by third party.

Conclusion

MAC and IP address both are equally required when a device communicate with another device in a network.

Download the difference table here.

Continue Reading:

Ways to find MAC Address of Remote Computers

For a better understanding of IP Address, please watch our related video:

A Network Bridge is a networking device principally operating at the data link layer (Layer 2) of the OSI model with filtering/forwarding/segmentation capabilities to work in a collision domain and a broadcast domain. On the other hand, Router is an internetworking device operating at the network layer (Layer 3) of the OSI model. A router is attached to two or more networks and forwards packets from one network to another and works in many broadcast domains. Let’s discus on features, highlights and comparison of both devices.

1. Features of Bridge and Router
2. Key highlights Bridge vs Router
3. Comparison Chart
4. Conclusion

Features of a Network Bridge

A bridge is a networking device for connecting two segments of a network and transmitting data between them. Bridge operate in both the physical and the data link layers of OSI model. There is a compulsion of using identical protocols for the segments to communicate. The primary use of a bridge is to send, filter, or flood any arriving frame which is depending on the MAC address of that specific frame.

Bridges forward Packets using the software. Thus bridges are software-based. Bridged network fragments collision domains, but do not fragment broadcast domains, instead forward all broadcasts.

Types of  Network bridges

• Simple Bridge- A simple bridge connects two segments and contains a table that limits the addresses of all the stations included in each of them.
• Multiport Bridge is employed when we want to link more than two LANs, and each table is containing the physical addresses of stations approachable through the particular port.
• Transparent Bridge performs its bridging functions and it’s also creates own table of station addresses.

Related – Network Bridge vs Repeater

Features of Router

 Unlike a bridge, if a router receives a packet that is not destined for a connected client, it will forward that packet onward. Routers depend on a routing table in order to know the next destination if it is outside the pool of addresses that the router is maintaining.

A router will have a WAN interface along with a LAN interface. The WAN connection is for all traffic outside of the router’s pool, and the LAN connection is for local clients. A router is located at any gateway — where one network meets another — including each point of presence on the internet

Key highlights of difference between Network Bridge and Router

• Routers are not transparent to the end stations. In contrast, Bridges are transparent to the end stations and does not rely on the protocol.
• In a bridge, frames are forwarded on the basis of the MAC address of the frame. As against, Router checks logical address (i.e., IP address) of the packets.
• The router can work on more than broadcast domain while Bridge can work on a single broadcast domain.
• Bridge functions at Data link layer while router operates at the Network layer of the OSI model.
• The bridge can relay frame from one segment to another whereas Router store and forward packets.

Comparison Chart 

Below table illustrates difference between Router and Bridge –

KEY TERMS	ROUTER	BRIDGE
Objectives	Router main objective is to connect various networks.	Bridge main objective is to connect various LANs.
Layer	Router works in Network Layer.	Bridge works in Data Link Layer.
Address	Router scans device’s IP Address.	Bridge scan device’s MAC Address.
Routing Table	Router uses routing table.	Bridge do not use routing table
Domain	Router works on more than single broadcast domains.	Bridge works on a single broadcast domain.
Ports	Router has more than two ports . Router devices are used to connect the LAN and WAN links.	Bridge has only two ports.
Transparency	Routers do not provide station transparency.	Bridges are protocol independent and transparent to the end stations.
Data Format	Router sends data in form of packets.	Bridge also sends data in form of packets.

Download the difference table here.

While working on networking concepts, network engineers may face challenge in understanding how Network Bridge and repeater are different and their working principles.

In this article, we will touchbase on both the devices and compare their functionalities –

Bridge is a networking device operating at the data link layer (Layer 2) of the OSI model with filtering/forwarding/segmentation capabilities to work in a collision domain and a broadcast domain.

Repeater is an electronic device which just regenerates the attenuated signals to its original wave form. It is a hardware device used to extend a local area network. Repeaters operate on layer One of OSI model. It regenerates the weak signal and increases the range of the network. Functionality of the network remains unchanged by the use of repeater. Bridge can be used as a repeater also. Let’s now deep dive on features and highlights of both devices.

1. Features of Bridge and Repeater
2. Key highlights Bridge Vs Repeater
3. Comparison Chart
4. Conclusion

Features of Repeater:

As signal travels along a network cable (or any other medium of transmission), they degrade because of wire’s resistance power and become distorted and lost its own original wave pattern that is called attenuation. If a cable is long enough it makes signal amplitude loss after a certain distance depends on medium.

A Repeater regenerates the signal to travel longer distances cable over a network. Repeaters operate on layer One of OSI model. A repeater regenerates the received signals and then re-transmits the regenerated (or conditioned) signals on other segments.

Repeater cannot operate between two different protocol like token ring and Ethernet.  In other words, repeaters do not translate anything it only understand the electrical signal wave form amplitude.

Related – Network Bridge

Features of Bridge:

A Bridge can join segments or work group LANs. A bridge can create logical networks. For example, it can control flooding of data from one network segment to another by creation of logical network.

Below is an arrangement which describes the bridge operation –

Usage of Bridges:

Bridges simply pass all protocols along the network. Because bridge has capability to allow traffic of multiple protocols, it mainly depends on sender and receiver to communicate on same protocol.

A bridge operates on the rule that each workstation has its own address. A bridge forwards the packets based on the hardware address of the particular destination node.

When frame arrives at port of bridge it will record it in its MAC address table with incoming port number and hardware address. Firstly it will broadcast with in same to get detail of destination node with help of ARP. The output gets added in table with destination MAC address and port number The bridge will then use this MAC table to forward traffic  unicast in next transfer.

Key highlights : Network Bridge Vs Repeater

1. In a bridge, frames are forwarded on the basis of the MAC address. As against, Repeater do not understand any frames/packet/bits.
2. Bridges can work on a single broadcast network segment while repeater can forward all segment traffic.
3. Bridge functions at Data link layer while repeater operates at the physical layer of the OSI model.
4. Bridge expands the limit of network segments while repeater can extend cable length in network.

Comparison Table

KEY TERMS	BRIDGE	REPEATER
Operation	Bridge operates at the data link layer of OSI Model.	Repeater operates at physical layer of OSI Model.
Packet	The complete frames is understood by bridge.	Repeater do not understand complete frame
Address	Destination address is used in the bridge to determine where to forward a frame.	Repeater are not able to recognize the destination address.
Domain	In the network, if collision occurs in the one segment, it is not forwarded to another segment	Repeater forwards the collision from one segment to another, which causes the same issue to occur on all other segments in the network.
Networks	Bridge connects two networks in a well organized manner.	Repeater expands the limit of the signals in the network.
Filtering	Filtering of the packets in network is achieved by the bridge.	Repeater cannot performs packet filtering.
Economical	Bridges are relatively expensive and used to extend a LAN.	Repeater is also used to extend a LAN, but comparably economical than the bridge.

Conclusion

Repeater use to extend wire length or to regenerate the attenuated signals. On other hand Bridge is used for segmentation of network (LAN) logically.

Download the difference table here.

A good and reliable network can help you in running a business operation seamlessly. That is the reason why a professionally reliable network always come with certain vital features that ensure unflinching results as per the given command. One such trusted feature is the network switch.

A network switch helps in controlling and guiding the flow of the network traffic and currently accessible in two distinctive forms, i.e. physical switches and virtual switches.

 Introduction

Here, we are going to shed some light over the physical switch vs virtual switch distinction and try to find out which can turn out to be the finest choice for your business needs among the two. First and foremost, let us have a glance over what both the varieties of switches are all about.

A physical switch is basically a tangible device that one can touch and feel, guiding the flow of the network traffic by basically forwarding the data packets to the designated device that leads to a well enabled range of networking functions in exchange. Physical Network switch is an individual entity which connects to physical devices like router, firewall, Physical switch, Server etc.

On the other hand, virtual switches function as intangible software that enable the network components, such as virtual machines to interact with each other. They are identical to the physical switches over one aspect that they function in an isolated manner without sharing the resources with one another. Virtual switches are used for connecting Virtual environments (VMs) to other VMs and also establish connections with physical networks.

Physical Switch vs Virtual Switch:

The following table would help you define the line of difference between the physical and virtual switches and reach onto to the inference of making the finest choice-

Conclusion

It is utterly true that both physical and virtual switches have their own merits and demerits. So in order to make a prudent physical switch vs virtual switch decision, it is suggestive to evaluate the system configuration and whether it is conducive merely to hardware switch terminals or could be expanded to virtual switch contours. If you are seeking better bandwidth capacity and would like to assess each data packet before passing them through the terminal then virtual switches are recommend. Rest of the aspects can function seamlessly in either case.

Related – VMware Distributed Switch vs Standard Switch

Network Topology refers to the physical or logical layout of a network. Hub and spoke or star topology is a site-to-site  Wide Area Network (WAN) topology. In this type of topology, we have a central device, called the hub, that is connected to multiple other devices named as the spokes.

Large enterprises have multiple business offices at different geographical locations globally. So, in that case we can use Hub and spoke topology, where business office (i.e. main office) act as a hub while other offices(branches) act as spokes. All the spoke sites are connected to each other via hub site. So, basically the network communication between any two spoke sites travel through the hub inevitably.

USES

• Hub and spoke topology can be used in a frame-relay network.
• It is also used with other protocols e.g DMVPN.

ADVANTAGE

• The main advantage of hub and spoke technology is that it is cost effective.
•  It is relatively easy to set up and maintain.

DISADVANTAGES

• WAN network topology may cause communication time lags.
• WAN network topology also has redundancy issues.
• Hub is a single point of failure, if the main office network fails, entire enterprise network communication may fail.

Watch this video for better understanding of Topologies:

In any IT setup, Network Engineer is the key and fundamental resource responsible for setup of network infrastructure on which all the services like Security, voice, wireless, messaging and Internet are made accessible. A network engineer is a technology expert who is highly skilled and trained in maintaining the connectivity of. Network engineering includes being responsible for formulating, implementing and executing all the computer networks within an organization.

Additionally, a network engineer plays crucial role in ensuring all the systems are functioning properly as instructed. The fundamental goal of a network engineer is to provide the maximum network to the organization with the security. Sometimes, organizations have to hire global network engineers across the countries depending on network complexity and an administration’s requirement. Their responsibility is to take care of technological advancements throughout the firm. This international network of engineers proves cost-effective for the organization.

Related – Why Cisco certification is important?

Key responsibilities of a network engineer include: 

• Router and Switch configuration
• Auditing in IP addresses.
• Arranging scheduled upgrades.
• Investigating faults in the network.
• Improving the efficiency of current networks
• Upgrading network equipment and data servers.
• Designing and implementing new network solutions.
• Linking with service desk engineers and project managers.
• Maintaining IT security systems and administering firewalls.
• Solving network problems and maximize network performance.

Skills required for network engineer:

Network Engineer job description should include the following skills and qualities:

Technical skills

A network engineer needs to:

• Understand the technical demands of their employer’s business
• Detailed knowledge of network protocols and services such as TCP/IP, DNS, proxy and DHCP.
• Well-known networking knowledge of protocols, devices, commands, topologies, techniques and best practices.
• Ability of handling network vulnerabilities.

Soft Skills

In addition to the technical knowledge and skills required of a network engineer, there are few of soft skills that will help in this career. These include

• Problem-solving and being a team player.
• Excellent communication skills are required as they have to communicate with the relevant parties – network engineers often report to business leaders, so the ability to communicate information confidently, clearly, and professionally is essential for them.
• Candidate must have multi-tasking skills and the ability to do various jobs at one time.
• Each and every organization gives more importance to time management, the candidate must adhere to the policies of the organization and the candidate should be able to complete the tasks on time.
• Excellent troubleshooting skills needed because troubleshooting requires experience and patience. The candidate must possess both to become a Network design engineer (Expert level).
• Network engineers are flexible enough as they often work on schedule time so as not to interrupt the work schedule of employees who need to be online at regular hours.

How to gain the essential network engineering skills?

Network engineering is an exciting, challenging field. But you can’t get there on your own. You require proper degree programme and you may specialize even further in the course of your networking career.

IT certifications and training courses are a great way to supplement on-the-job training.

Related – New Cisco Certifications in 2020

With networking training courses, you will learn about information security, operating systems, network administration and programming essentials. Depending on the organization, they may also require specific certifications or training courses.

An industry known certification is CCNA Routing &Switching. This certification also equips a professional network engineer with the knowledge and abilities required to work on Cisco products or any other networking vendor device. Another well know networking certification is Comptia A+ and network+.

Working and detection

CRC works with a simple technique. Whenever the data is to be transmitted, a computed amount of check bits are appended to the data. These bits are also called checksum. Once it is assigned to the data, the data is then transited to the destination. The checksum is also maintained at the destination side.

Upon receiving the data in the destination, it is checked for all the errors using those checksum. The goal is to ensure that checksum of the received data is same as the checksum received. If there are any mathematical data changes, a negative acknowledgment is sent. Hence, the data is re transmitted and hence the user receives the correct data.

If we see the technical side, the data receivers, first of all, will check the value of the data. It is done by looking for the remainder of the content’s polynomial division. Using this procedure, it is confirmed whether the data is transmitted as it was, or there is error occurred in between the data transmission.

Real-life example

Let’s talk about the real-time example of the CRC working. As we have seen above, CRC is also used in hard drive. There is a checksum allocated to each and every block in the hard drive. Whenever a hard drive is connected with the computer, the computer will first check the checksum of each of these blocks. If there are any issues with these blocks and checksum is not matched, a negative acknowledgment is sent and the CRC is reported.

In such cases, a computer can identify if the whole block is corrupted or any particular file is corrupt.  This generally happens when the system crashes or files we are transferring are incomplete or corrupted. Also, if there are more amount of bugs in the file, it will show an error while computing the checksum and hence you will not be able to check the files.

The CRC design will totally depend on the length of the block. If the hard disk has more space, the blocks are also of a bigger size. Hence, the CRC design is made accordingly. In the same way, the protection features and resources will depend on the block. Moreover, the performance and the speed of the CRC detection will totally depend on the model. Therefore, if the standard model is used, the performance will also increase. Generally, a small-size storage device won’t need more speed as it can easily be completed in less amount of time.

Related – MD5 vs CRC

More about CRC

The CRC technique is not new and is being implemented from last many years. It was first invented in 1961 by a W. Wesley Peterson. It was developed by Comité Consultatif International Telegraphique et Telephoniquealso known as CCITT. First of all, it was a simple technique which was implemented in the hardware unit to check if there are any errors. Wesley came to know that errors can easily be analyzed mathematically and hence the technique was introduced.

The whole technique works on mathematics and more precisely on Binary division. Therefore, it is also known as Polynomial code checksum. First of all, the binary division is done of the polynomial function and once it is found, the remainder is taken into consideration to check it further.

Since then the technique is implemented wherever possible. Later on, the same technique was also implemented in the re-writable CD/DVD to ensure the copied materials and files are error-free. Now, it is used in almost every storage device and also on many other devices where there are chances of errors. The model of the CRC is different depending on the device it is implemented.

There is a difference between bridging and routing. In routing, there are more than one networks which run independently but they can communicate with one another. However, in the bridging, the concept is totally different. Here, the two networks are bridged together in order to work s  a single network. Here the two networks can’t operate and function as a different network.

When talking about the OSI model, the bridging is performed in the data link layer, i.e layer 2.

The bridge can be done either using the cables or you can also do it without cables via wireless. If the computers are connected via wireless, it is called a wireless bridge.

Data in the Network bridge

The bridge is used to transfer the frame from one to another. The bridge maintains MAC where the addresses are stored.  This is the a major feature which is not present in the repeaters and hubs.  Some people also call bridge as Layer 2 switches.

Working of a Network Bridge

A Bridge is generally used in a local area network. This is because they can eventually flood and clog into a large network. Also, it is far easy to transfer the data to all the nodes just in case they don’t know about the MAC address of the destination node.

A bridge is used for the connection of one or more device where the network is passed. Using the bridge, one or more network can behave as a single network.

The working of the bridge is simple; the frame is directly sent to all the different nodes that are connected using it.

If there are any problems occurred in the bridge, and the frame received is meant for the segments that are on the same network then the node is then discarded. In this way, the conflict that occurs is solved easily.

On the same hand, if the bridge received any frame where the MAC address is correct and the frame is meant to be sent to the connected network then in such cases, the frame is transferred without any issues.

Related – Bridge vs Router

Types of Network bridges

There are various kinds of bridges where the bridging is done. In each of the working is almost the same. However, there is a small difference seen.

• Transparent bridging: Here, when the bridging is being done and the frame is about to be transferred. If the table shows empty and there is no MAC address found, the bridge will send the frame to each and every node present.
• Simple Bridge: It is the regular bridging where the two network segments are connected to each other. The transfer is done a frame by frame to decide whether the selected frame has to be transferred to the other network or not.
• Multi-port Bridging: Here, the process is almost the same as a simple bridge, It stores the frame, decides and then forwards it. The only difference here is that there is an additional Bridge that will decide where the traffic is forwarded.

Shortest path bridging

SPB known as Shortest Path Bridging is a standard that is stated in IEEE 802.1. Here, computer network technology decides the shortest path to send any frame. This also enables multipath routing. There are various techniques used to decide the shortest path for the bridge mechanism. This replaces the older spanning tree protocols and making it faster to choose the paths.

How does it work?

When the local area network obtains information from a workstation, it identifies the data to a particular VLAN from which it originated. That process is known as explicit tagging. The originating VLAN can also be identified through a process called implicit tagging.  The implicit tagging method does not use tags but identifies the source VLAN based on the port on which the data was acquired. However, tagging can be found on information such as MAC (media access control) area of source network address as well as a combination of various fields. Thus VLANs are categorized according to the method used.

Despite the tagging method, the procedure remains the same. In a port tagging method, the filtering database indicates which belong identify with a particular VLAN. The bridges maintain the database and contain similar information in their databases. The bridge initially determines where the data is to send based on normal LAN processes. After determining the recipient of the data, the bridges then determine whether the VLAN identifier is to be supplementary to the information. In cases where the recipient device has no information on the VLAN identifier, the brides send the data without the id.

Related –VLAN vs Subnet

Why do we need a VLAN?

The configuration of a VLAN becomes essential when one has an extensive network that is creating traffic. It enables the user to apply extra security to a communication network and at the same time simplifies the relocation and expansion of a network device. Consequently, it has a higher exposure to viruses since many computers are using a similar network, increasing the risk of spreading the virus. Though the VLAN has a bunch of benefits, many use it unconsciously because the systems they are using have configured them already.

Related – VLAN vs VXLAN

Switching is the important mechanism that provides communication between different endpoints or different computers and manages the data flow between the two end points. There are three types of switching techniques –

• Circuit switching
• Packet switching
• Message switching

In this previous post we discussed Circuit Switching. In this post we will discuss Packet Switching.

Packet switching is a switching method in which data  is transferred in the form of small broken pieces of variable lengths. These broken pieces of data are called as packets. The data is transferred in the form of packets, transmitted to the network line and  reassembled at the destination making a complete file.

Thus, Packet Switching method uses Store and Forward technique. Each hop will store the packet and then forward the packets to the next host destination.

Types of Packet Switching

There are two types of packet switching :

• Virtual Circuit Packet Switching
• Datagram Packet Switching

VC Packet Switching:

VC Packet Switching is an approach in which a logical path or virtual circuit connection is done between sender and receiver. VC stands for Virtual Circuit. Thus, a predefined route is created and all packets will follow these predefined paths. In this logical connection, all routers or switches are provided with a unique Virtual Circuit ID to uniquely identify the virtual connections. It also has the same three-phase protocol used in circuit switching – Setup Phase, Data Transfer Phase and Tear down Phase. WAN, ATM, frame relay and telephone networks use virtual circuit approach.

In this diagram, four users connected with a four-switch network are showing  data flow in Virtual circuit mode. The four switches are connected with each other and share the communications path with each other. To transfer data from USER A to the USER D, a predefined route is established, that passes from USER A to  S1 to S2 to S3 and then finally to USER D. In this predefined route  S1, S2, S3 are provided with a unique Virtual Circuit ID to identify the virtual connection, so the data is bound by the predefined path and could not choose another route.

Datagram Packet Switching:

In Datagram packet switching each packet has all the necessary information like Source address, destination address etc. So each packet is treated independently. They can choose different routes for transmitting data inside the network. There is no predefined route. So, the packets can be received in any sequence at the destination. Packets in this approach are called datagrams. Datagram approach can cause the datagrams to reach the destination out of order. Additional end system protocols need to be configured, to secure guaranteed packet receiving. This mode of packet switching, doesn’t involve setup, transfer and teardown phase.

In this diagram, again four users are connected with a switch- network , and  data is transferred from USER A  to USER D. The data contains two packets (or datagrams) – a and b. In Datagram Packet Switching, PACKET a & PACKET b choose different  paths to reach the final destination i.e. USER D.

PACKET a :

USER A – S1 – S4 – S3 – USER D

PACKET b :

USER A – S1- S5 – S3 – USER D

The different paths can be chosen depending on the delay time and congestion on other paths.

FAQs

• Is Packet Switching still in use?
• Yes, Packet switching is used in the Internet and most local area networks.  Newer mobile phone technologies (e.g., GSM, LTE) also use packet switching.
• Which switching method is most secure?

Switching is an important mechanism that provides communication between different networks or different computer(s) and manages the data flow between the two end points. There are three types of switching techniques –

• Circuit switching
• Packet switching
• Message switching.

Here we will discuss Circuit switching.

Circuit switching

It is a switching method in which a dedicated physical path is formed between two points in a network i.e. between the sending and the receiving devices. These dedicated paths are created by a set of switches connected by physical links. Circuit switching is the simplest method of data communication that has a fixed data rate and both the subscribers need to operate at this fixed rate.

Phases Of Circuit switching Communication

It has basically three phases :

Establishment or Setup Phase  –

A dedicated circuit or path is established between the sender and receiver before the actual data transfer. End-to-End addressing  i.e. source address and destination address, is required for creating a connection between two  physical devices.

Data Transfer Phase –

Data transfer only starts after the setup phase is completed and a physical, dedicated path is established. The data flow is continuous and there may be periods of silence in data transmitting. Generally all internal connections are made in duplex form. The switches use time slot (TDM) or the occupied band (FDM) to route the data from the sender to the receiver and no addressing method is involved.

TDM (Time Division Multiplexing) and FDM (Frequency Division Multiplexing) are types of multiplexing techniques that are used to transmit multiple signals over a single channel. In FDM, multiple signals are transmitted by occupying different frequency slots while in TDM, the signals get transmitted in multiple time slots.

Disconnect or Teardown Phase –

When one of the subscribers (either the sender or the receiver) needs to disconnect, a disconnect signal is sent to each switch to release the resource and break/disconnect the connection.

Example

One of the major example of Circuit Switching is the Plain Old Telephone System (POTS).

Advantages of Circuit Switching

1. The data rate is fixed and dedicated as the connection is established using dedicated physical path.
2. Once the circuit is established, there is no waiting time and the data transmission delay is negligible.
3. Since a dedicated path is established, it is a good choice for continuous transmission over a long duration.

Disadvantages of Circuit Switching 

1. Since the connection is dedicated it cannot be used for any other data transmission even if the channel is free.
2. It is inefficient in terms of utilization of the system resource. As it is allocated for the entire conversation, we can’t use the resource for other connection.
3. More bandwidth is required for the dedicated channels .
4. Establishment of physical links between senders and receivers takes huge time prior to the actual data transfer.

FAQs :

• Is circuit switching faster than packet switching?
• Packet switching is faster than Circuit switching. Packet switching is more efficient as all the bandwidth can be used at once and it doesn’t have to deal with a limited number of connections that may not be using all that bandwidth.

Lets explore the differences between the two.

Virtual PortChannel (vPC)

vPC allows two separate physical switches (Nexus series) to appear as a single logical switch to a downstream device (like a server or another switch) by combining their links into a single PortChannel. It is used in Cisco Nexus switches (data center environments).

Features of vPC

• Multi-Chassis EtherChannel: Enables a server/switch to bundle links across two Nexus switches.
• No STP Blocking: All links are active (no blocked ports).
• Independent Control Planes: Each switch maintains its own management plane.
• Used with: FEX (Fabric Extenders), servers, storage, and other switches.

How vPC Works

Two Nexus switches form a vPC domain and synchronize using vPC peer-keepalive and vPC peer-link. A downstream device (e.g., a server) connects to both switches via a PortChannel, thinking it’s connected to a single switch.

Use Cases for vPC

• Data center server connectivity (active-active links).
• Storage networks (SAN/NAS dual-homed connections).
• Avoiding STP bottlenecks in Layer 2 networks.

Virtual Switching System (VSS)

VSS combines two physical Catalyst switches (6500/6800 series) into a single logical switch with one control plane. It is used in Cisco Catalyst switches (enterprise/core networks).

Features of VSS

• Single Logical Switch: Two switches act as one (single management IP, single STP instance).
• Simplified Management: One configuration applies to both switches.
• Active/Standby Supervisor: One switch controls forwarding (the other is standby).
• Used with: Core/distribution layer switches.

How VSS Works

Two Catalyst switches are connected via Virtual Switch Link (VSL). One switch becomes the active supervisor, handling all control plane functions. Downstream devices see them as a single switch.

Use Cases for VSS

• Enterprise core/distribution layer redundancy.
• Campus networks requiring simplified STP and high availability.
• Reducing network complexity (single logical switch).

Comparison Table: VPC vs VSS

Continue Reading:

What is a virtual Switch?

VSS vs STACK

Network Switching works at Layer 2 (Data Link Layer) of OSI model. Switching is a process of receiving frame from one incoming port (ingress) and then forwarding it to as desired destination (egress).

Types of Network Switching

Switching is of 3 types –

• Circuit Switching
• Message Switching
• Packet Switching

Circuit switching 

It is a switching method in which a dedicated physical path is formed between two points in a network i.e. between the sending and the receiving devices. These dedicated paths are created by a set of switches connected by physical links. Circuit switching is the simplest method of data communication that has a fixed data rate and both the subscribers need to operate at this fixed rate.

Message Switching

It is a switching method that was developed as an alternative to Circuit switching before the advent of Packet Switching. Message switching is a connectionless technique in which the entire message is routed from the source node to the destination node by one hop at a time, called hop-by-hop system. The distinctive features of message switching are:

Store and Forward network: The message is not discarded in case of non availability of the next hop. Rather, it is stored in a queue  and is  retransmitted when the required route is available .This is called store and forward network.

Message delivery: The entire information is wrapped in a single message and transferred from the source to the destination node as a “message” with a definite destination address in the header.

Packet switching

It is a switching method in which data  is transferred in the form of small broken pieces of variable lengths. These broken pieces of data are called as packets. The data is transferred in the form of packets, transmitted to the network line and  reassembled at the destination making a complete file.

Thus, Packet Switching method also uses Store and Forward technique. Each hop will store the packet and then forward the packets to the next host destination.

There are two types of packet switching :

• Virtual Circuit Packet Switching: VC Packet Switching is an approach in which a logical path or virtual circuit connection is done between sender and receiver. VC stands for Virtual Circuit.
• Datagram Packet Switching: In Datagram packet switching each packet has all the necessary information like Source address, destination address etc. So each packet is treated independently. Packets in this approach are called datagrams.

Related – Network Switching Basics

FAQs Related to Network Switching