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What are Legacy Network Components?

Legacy Network Components

If you’re working on an older network it’s been around for a while you might come up some older, some legacy network components. Let’s take a few moments that make sure you understand that the function of some of these components. For example, we’ve got a hub which would be used in older ethernet network. We’ve got a media access unit (MAU) then you might find older token ring networks. And we also have a bridge which is the predecessor to the modern-day ethernet switch.

Hub:

legacy network components
       Legacy Network Components

An ethernet hub is an early ethernet device, a legacy device that used to be used quite a bit to interconnected things like clients and servers. One of the important characteristics to know about the Hub is that it doesn’t make the forwarding decision. It’s not analyzing any sort of Mac address or IP addresses not analyzing anything in order to make forwarding decisions. In fact, sometimes it’s simply referred as a Bit Spitter or it takes bits and on one of its ports and just repeats them out of the other ports. Hub used in early ethernet networks and the competition back to this time was a token ring that was the other predominant technology. Hub only has a single collision domain all of the ports on this device belongs to single collision domain.

Scenario:

Referred to below diagram. If a pc want to transmit on this shared ethernet network what it’s going to do is use an approach called CSMA-CD carrier sense multiple access with collision detection. It’s going to listen to the network to see if anybody’s talking at the moment. Because we can only have one packet at a time on this shared ethernet segment and if it concludes that the coast is clear it can transmit. But let’s say that the pc and the laptop there are simultaneously listening to see if the coast is clear. And they hear the same period of silence what’s going to happen they might transmit at about the same time. Resulting in their two packets colliding that’s known as a collision. The packets are corrupted they have to be retransmitted but remember what CSMA-CD stand for the CD stands for collision detection.

The devices can detect that a collision occurred and they can retransmit. It’s not going to scale on larger networks because we only have a single collision domain. We also have a single broadcast domain. A broadcast packet is a packet that is sent out to all of the workstations. All of the ethernet devices on a subnet and the hub is going to take a broadcast in on one port and repeated out all of the other ports. It’s not separating broadcast domains, it’s not separating collision domains. In fact all of the ports going to the same broadcast domain and to the same collision domain.

MAU:

legacy network components
            Legacy Network Components

MAU( media access unit) a media access unit is on number second in the list of legacy network components which is much like a hub could be used to interconnect clients, servers and other network devices. But instead of being used on an ethernet network. It was used on the token ring network. Similar to the hub a MAU does not make forwarding decisions. It simply does token passing a token that arrives on one interface is going to be sent out of the next interface. It’s going to return and it’s going to be sent out of the next interfaces. Logically even though it looks like star typology but what’s happening inside of the MAU is that it is the logical ring topology.

There is a token that is circulating around all of the device connected to into the MAU. As a result, this was used in the early token ring network. We had a single collision domain with token ring. In token passing, a device that accesses to the media is more deterministic. When you receive the token it’s your return to transmit on the network. As a result, there’s not the issue of collisions that we had with a hub so there’s no collision domain. However, there is a single broadcast domain. If a broadcast is sent by one of these devices it’s going to be seen by the other devices there was nothing blocking the broadcast.

Bridge:

legacy network components
     Legacy Network Components

A bridge is a present number third in the list of legacy network components. A bridge is going to separate a network into different collision domain. If a bridge has two ports as early bridge used that would give us two collision domains. We don’t  have a hub connected to each of the bridge ports and the hubs themselves they’re in their own collision domain. If a collision occurred because a laptop and a pc on one hub sent packets at the same time. And they collided that would impact everybody off of that bridge port. But it would not impacts devices connected to the other bridge port. Unlike a MAU, unlikely the hub a bridge does intelligently make forwarding decisions.

Mechanism:

It’s going to learn as it these frames flow through the network. And then it’s going to learn the Mac address 48-bit address that’s burned into these network devices. It’s going to know that the laptop with this 48-bit Mac resides of port number 1 and this file server or with other Mac address. That resides the port number two then later on after it populates this Mac table if it receives a frame that’s a destined for the specific destination Mac. It’s got to consult it’s Mac table and realized that, this Mac I learned in earlier.

A bridge is really the predecessor of the modern-day ethernet switch. Because like a bridge and ethernet switch which is going to separate our network into different collision domains. Each port on an ethernet switch isn’t its own collision domain and just like a bridge and ethernet switch which is going to make forwarding decisions based on Mac address information like a bridge one of the big difference he’s though is performance.

ASIC:

Back in the mid-80s and early 90s, when bridges were more popular a bridge made it’s forwarding decision. While an ethernet switch has special circuitry called ASIC (applications specific integrated circuits). That going to allow the switch to make forwarding decisions and in real time and so it’s significantly better performance wise than a bridge. This bridge has two ports, therefore, this specific bridge has two collision domains. But what about broadcasts can broadcast traverse the bridge? Yes, in fact, we need a router, a router is going to separate broadcast domains a bridge doesn’t. That means that are broadcast sent from pc off of one of our bridge port. It’s going to be seen by all of the other device use off of that same bridge port. In addition to all of the device is connected to the other bridge ports we’re not blocking broadcasts with a bridge.

Bottom Line of all Legacy Network Components:

Hub:

  1. Interconnects clients, servers and other network devices.
  2. Does not make forwarding decision
  3. Also known as Bit Spitter
  4. Used in Ethernet networks
  5. One Collision domain
  6. One broadcast domain

MAU:

  1. Interconnects client, servers and other network devices
  2. Does not make forwarding decision
  3. Used in token ring networks
  4. Collision domain doesn’t apply here
  5. One broadcast domain

Bridge:

  1. Separates network into collision domains
  2. Makes forwarding decision based on Mac address
  3. The predecessor to the Ethernet switch
  4. Two collision domains
  5. One broadcast domain

This is all about the legacy network components find out more about Transmission Media in Computer Networks.

Summary
What are legacy network components?
Article Name
What are legacy network components?
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This article is about legacy network components like Hub, Bridge, and MAU.
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Learn Computer Networking
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