Fundamental Network Components

We know that what is network and how to categorize them, in this tutorial we are going to look about networking media and components. So do you mean by networking components? Does it devices like end hosts; no networking components are the specialized devices that are used to interconnect the devices.

In this tutorial we are going to look about

• HUB
• MAU
• Bridge

In the above figure shows a simple topology where data is transmitted through physically and by air so that is known as media. Switch, routers and wireless access point are the components from above figure.
Switch is Layer 2 (L2) devices which have intelligent frame forwarding decision based on physical address, end devices are connected to the switch then switch will learn the mac address burned in to the NIC of the devices. By this way switch learns the unique mac address of connected devices and build the mac address table in which it will have mac address and port to which the devices are connected.
Router is Layer 3 (L3) devices make forwarding decision based on the logical address. We can discuss more about logical address in upcoming posts. It provides flexibility and scalability because we can connect to outside network.

Basic Network Components

In this we are going to discuss about some legacy networking components such as hub, MAU, bridge.

Hubs

Hubs are the older devices used in the Ethernet in order to connect server, end devices etc...Hub can be thought as a multiport repeater. Repeater are devices used to amplify signals in between them, it is two port devices. It doesn't make forwarding decisions; it’s called bit splitter because if it receives any signal in port it will transmit that data to all ports. It has a collision domain; collision domain is an area on Ethernet where collision occurs. Having Single collision domain will degrade the performance of the network. It has one broadcast domain; is the area of an Ethernet network where a broadcast will be propagated.

 Hub’s incapable of processing L2 and L3 information, so it doesn't work on physical and logical addresses. If the receive a frame in one port it will transmit to all ports so if two devices transit simultaneously collision will occur. From above figure it’s clear that how hub’s transmit data; since it is functioning like this security is the main problem i.e. if anyone using packet capture he can get all data.
Since Hub’s are useful it also had drawbacks that are broadcast storms and collisions. Hub operates in half duplex, means it can transmit or receive at a time. Since it’s working in half duplex it uses CSMA/CD (Carrier Sense Multi Access/ Collision Detection) carrier sense means all terminal devices will be watching the channel in order to transmit if it’s free. End devices only transmit only if the link is idle.

If two devices think that channel is free then they transmit at same time then it will end in collision, from above figure if pc and laptop transmit same time it will end in collision if collision occurred the transmitted device will send 32-bit jam sequence then all device is aware of collision, then the collide frames will be discarded. So the devices wait for random back-off timer in order to reduce further collisions.

If pc and laptop ends in collision it will sends 32-bit jam sequence and send random back-off timer for both device so we can say that 10ms for pc and 20ms for laptop. So by this random back-off timer pc will transmit first and after that laptop will use the channel.  It has only one collision domain and if we attach more devices collision will increases.

MAU

Media Access Unit (MAU) it is used to interconnect server and terminal devices and MAU is used in token ring network and not in Ethernet. As you know MAU is similar to HUB it don’t make frame forwarding decisions; it will pass token to all devices connected to their ports.MAU operates logically as ring topology and star as physically. Collision domain doesn't apply here because it logical token is passing through the devices, only device having token will transmit it but it have one broadcast domain.

Bridge

Bridge is predecessor to switch; have intelligent frame forwarding decision based on physical address, end devices are connected to the switch then switch will learn the mac address burned in to the NIC of the devices, this way switch learns the unique mac address of connected devices and build the mac address table in which it will have mac address and port to which the devices are connected, all this done by the software embedded to it. Thus bridge is slower compared to switch and have lesser port density .Switch does this job by using special circuit known as Application Specific Integrated Circuits (ASIC) .

The main advantage of bridge was it can separate collision it means it can have as such collision domain as per ports. Thus collision in one side of the bridge will not interfere with the communication of other ports.
Now we have looked in to some basic network components in next post we can look about media through which data propagates.

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About Jas Jashim

Jas Jashim Author and Founder of ccnaguru.com.He is electronics and communication engineer by education, working in networking field.Started this blog as an hobby to help you in ccna studies.

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