Network Hubs In Information Technology – In a previous post, I described every bit and byte of the Ethernet protocol. In this post, you’ll learn about two network devices, how they work, and how hackers can use that knowledge.
Before describing network devices, consider a network without special network devices. That is, a network that uses classic Ethernet, where all computers are connected by a single cable.
Network Hubs In Information Technology
In this case, if computer A sends a message to another computer, such as B, the message is sent over a common cable and all devices receive it.
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With Ethernet classic, if A sends a message to B – all devices (except A) receive this message (Source: Brief)
First, congestion – all network frames are received by all computers. Let’s say A wants to send a frame to B. C also sees this frame and realizes that it is not intended for its address and therefore discards it. This process takes time and resources. Of course, the same process happens with machine D.
Second, privacy – if C sees every message sent from A to B and vice versa, that means privacy is broken. Instead, we have a network where only A and B see the messages sent between them.
Third, extensibility – this network is not really extensible. We estimate that up to 10 computers can be connected to this cable. What if you need to add another computer? You will have to replace the entire cable. It is expensive and inconvenient.
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Well, the person who has to replace the cable is probably I.T. the person — you know, the one who makes sure everything runs smoothly on your network and is rarely noticed until something bad happens (at least when you’re in an organization big enough to have IT people).
To be clear, we LOVE I.T. man We want them to have a good life, we don’t want them running around buying cables all the time.
Fourth, meetings – suppose A wants to send a message to B and C wants to send a message to D. Simultaneously, both can start transmission and the messages will be delivered.
In this case, we have a mistake – very similar to the case when two people start talking at the same time, and it is impossible to understand one or the other.
Get Ready For Smart Spokes And Dumb Hubs
Fifth, this network structure can lead to starvation – say A transmits a frame. If other stations want to avoid collisions, they will refrain from sending data. But now machine A can continue transmitting forever, thus taking the entire frequency band for itself and not allowing any other station to speak. This is called hunger.
A device that only solves the problem of expansion is called a hub. A hub is a device with multiple ports to which individual Ethernet cables connect:
An Ethernet hub is a device with multiple ports, each connected to a single Ethernet cable (Source: Short)
So now instead of a multi-port cable with many computers connected to it, we have a single hub and each computer is connected by a single cable. This makes I.T. a person’s life becomes much easier.
Case Study: Network Hub Failure
The center simply accepts the received pulse and multiplies it, that is, sends it to all other ports. For example, if A sends a frame to B, the hub will send that frame to B, C, and D—all ports except A’s port.
The hub does not understand Ethernet and knows nothing about MAC addresses. To a hub, all bits are just bits transmitted over the wire, and those bits must reach all the other ends.
A hub simply takes a bitstream and multiplies it to all ports except the source port (Source: Brief)
Now, if you need to add a new computer to the network, you can simply connect to the hub.
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What happens if the hub runs out of ports? No problem, we’ll connect it to another hub like this:
However, at least with classical centers, all other problems remain. Since all computers receive frames sent from A to B, there is no privacy, the network is congested, collisions can occur, and the network is prone to starvation.
What we really need is a device that, when A sends a frame to B, forwards that frame to B and only B. This device is called a switch.
If all stations are connected via a switch and A sends a frame to B, only B receives it.
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With a switch, if A sends a message to B, only B will receive it (Source: Brief)
Note that this means that all issues are indeed resolved. Devices will not be overloaded because each frame will only reach the appropriate recipients. There are no privacy issues since, apart from the switch, only A and B will see the frame. The network can be easily expanded by adding additional switches if needed.
A switch can avoid collisions because each connection between the switch and the endpoint is a single collision domain, meaning the switch will not avoid sending more than one frame in the same stream at the same time.
Likewise, there will be no starvation since B and C can communicate with each other while A is sending data. Although A continues to send frames destined for the entire network, it is a broadcast address, this change can allow messages sent by other hosts to be forwarded between them.
Important Network Devices » Networkustad
Let’s say we just bought a new switch and connected it to the network. A sends a frame destined for B. How does the switch know where B’s computer is?
One option would be to configure the switch manually. That is, have a mapping table between the MAC address and the corresponding port and have someone manually configure this table.
, we usually mean I.T. man And, well, we LOVE I.T. People We would not like to do this boring job every time.
Also, I don’t know about you, but most people usually don’t have I.T. person’s home every time they connect a device to their network.
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Another option would be to send a special message from the switch to each port, and then the endpoints will respond with their MAC addresses. The main disadvantage here is that we now have to notify all devices about the changes. We need to change the behavior of the devices to respond to this special message.
It would be much better if the change was just transparent – no endpoint would need to know it was there, but it would still do its job.
Consider this network with a new switch that has been added to the network. The switch maintains a table mapping a MAC address to a physical port. This table is empty.
When a switch joins a new network, the MAC address to physical port mapping table is empty (Source: Brief)
Considerations For A Hub And Spoke Model When Deploying Infrastructure In The Cloud
The switch understands Ethernet and can look at the frame header and read the source address. Since the source address is mapped to “A” and since the message was sent from physical port 2, the switch adds the mapping of A’s MAC address and port number 2 to its table.
When machine A sends a frame, the switch examines the frame, reads the source address, and binds it to the corresponding physical port (Source: short)
But what will change with the frame? Currently, the switch doesn’t know where B is, so it just multiplies the frame and sends it to all ports, just like the hub does. So for now all B, C and D are getting a frame.
Since the switch table does not contain an entry for B, the frame destined for B is actually sent to all ports except the source port – just as a hub would (Source: Brief description)
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Next, A sends another message to B. The switch sees it and already knows that A’s MAC address is connected to port number 2. It doesn’t know B yet, so this frame is also sent to all the other ports
C now sends the frame to A. The switch saves the source address and adds the mapping between C’s MAC address and port number 5 to its table.
After receiving a frame from C, the switch analyzes its header, extracts the source address and associates it with the corresponding physical port – port number 5 (Source: Short)
This time, because the frame is intended for MAC address A, and because the switch knows that address, the frame can be forwarded to port number 2 and only port number 2. Yes! 👏🏻👏🏻👏🏻
D Link Easysmart 8 Port Gigabit Poe Switch
B now sends a message to C. The switch maps port number 7 to B’s MAC address, which appears in the source address field.
So, in general, a switch uses the source address field of Ethernet frames to dynamically learn what addresses are behind each port.
And now the question is for you: is it possible to match two different addresses with one
