Some questions about network devices

[Carlos1010]

Hi all,

So I have some questions about hubs and other network devices because I have been looking into them today.

 

First lets just say you have a hub, and you are alone on your network therefore you are only sending packets outside to the internet and not on your LAN, will this make a difference then having a router?

 

Second, when I watched these videos talking about network devices they also talked about sharing data on the LAN, so are you saying that when sending a email to a person in the same network as you, the packet doesn't go out the hub? It stays inside and with the MAC address gives the data to the person you whom to send it to? (I really don't understand are his Local network sharing they are talking about when referring to these devices) 

 

Thirdly, what's up with these MAC addresses, I literally only learned after looking on the web that it's something your network device uses when it tries to connect to another device on the same network. Is this even true? A good link to a page you think can give a better explanation would be awesome!

 

Lastly, can someone point to me a link to a video (yeah not a article lol) about all these cables that connect like DSL,fiber and another one? I really don't get what it is, is it the cable that's connects the router to the modem or is it the cable that connects to your PC? And also which one are faster and the advantages and disadvantages of each one. 

 

Thanks in advanced and any help is much appreciated. Sorry for the amount of questions, I need a second source to help me! Have a awesome day!

[_JohnB330ci]

From what I know, Mac Addresses are used as Identification signatures on your LAN, similar to IPv4 Addresses. It allows for communication between devices to be more secured, easier and smoother.

[Eniqmatic]

1 - A hub cannot route to the internet. Think of a hub as a dumb device. When a packet is sent and received at a hub, the hub will actually transmit data to all active/connected links till it gets a reply.

2 - Your example isn't valid because the type of email your talking about requires connectivity to a mail server - traditionally found on the internet. Perhaps if you ran your own internal mail server this might work but even then.

4 - Can you please rephrase/reword better?

[Lurick]

22 minutes ago, SherifsDog22 said:

From what I know, Mac Addresses are used as Identification signatures on your LAN, similar to IPv4 Addresses. It allows for communication between devices to be more secured, easier and smoother.

No.

 

A MAC address is used to tell Device 1 how to get to Device 2, the MAC address is stripped off at every hop and the destination address becomes the source and the new destination is that of the next device. A MAC address does nothing for security, faster communication, or anything else. It is literally how a packet gets from point A to B at Layer 2 when there is no Layer 3 information (IP Addresses) used by the switch.

[mariushm]

A hub takes whatever it receives on one network port, and sends this data to all the other network ports without making any changes. It's a dumb device, like a signal splitter. The devices at the end of the cables connected in those network ports just throw away the information if they don't need it.  

 

Switches are smarter, they memorize the address of the devices at the end of network cables plugged in their ports. When your computer's network card sends data packets to the router, the router looks inside the data packets to see to which network address the packets are dedicated for and determines on which switch port that network address is located and sends the data packets only on that port.

 

If you have a hub and several computers copying data between them, the hub will be much slower than a switch.

 

A router creates a connection to a remote location (the ISP) and also creates a connection to a switch (inside the router) to which local computers are connected.  The router acts as a man in between the switch and the ISP.

The switch side of the router determines if the communication is between computers in the local network (just move the data packets between network ports) or not.  If it's communication meant for outside local network, the switch passes the data packets to the router section of the router.

 

The router looks up at the data packets, looks inside to determine which computer sent these data packets and then edits them to make it look like the router itself requested that data. This way, no matter how many computers request data from Internet, the ISP sees only one device requesting data, the router.  When the ISP replies back with data, the router remembers that this reply is meant for a particular computer in the local network, so it sends back the data packets to the switch side and then the switch side sends the data packets just to that network port that needs to receive them.

 

A MAC address is an unique code assigned to the network card, in theory there's no two network cards out there with the same MAC address. It's how switches determine and remember which network card sent data packets to it, and how it knows where to return data.

 

The ISP sends data to your house through one of several cables, each with their pros and cons. The ISP takes the data and encodes it in a specific way that's best suited for the medium (the optical fiber, the TV cable, the copper wires in the phone cable). When the signal reaches your house, something has to convert this signal to a more universal standardized way, and this is done by a MODEM (short for MOdulator and DEModulator).  Nowadays, most boxes you receive from the ISP are a combination of this modem, plus a network switch which makes it possible to have those network ports in the back of the box, and often a wireless network card which acts as an access point, so that devices in your house (computers and phones and so on) can connect to the internet without wires. 

 

The modem section of this box  decodes the data coming through various types of wires and makes it available as data formatted to go through a standard network cable. This data is moved into the "router" part of the box which makes the connections between this modem and the switch and optionally also to the wireless network side of the box.

The router manages all the computers and devices connected to the box (either through network cables or wireless through the wireless network card) and determines if the data packets have to go outside the local network and if so, it edits the data packets to make it look like they're all coming from the router itself and pass them along to the modem side to be encoded and sent through whatever cable the ISP uses.

 

fiber optic is expensive but there's no signal degradation for long distances (even 20-50km). Converters from fiber optic to regular ethernet are kind of expensive (usually at least $40-50 and you need two, one on both ends, that's why it's not so commonly used. Splicing equipment (to connect two ends of optical fiber to make a longer optical fiber, or to put connectors at the end of the fiber) is also expensive and training people to do it is also expensive.

ISPs often prefer to have fiber up to some place in a neighborhood (or at the top of an apartment building) and have a converter there which converts the signal coming through optical fiber and encodes it to go through TV cable to each apartment because tv cable is much cheaper and cable modems are also much cheaper.

 

DSL connections are cheap for the ISP because the copper wires are usually already in place, installed a long time ago for telephones. The infrastructure is already in place.  The downside is the signal degrades and maximum speeds depend on how close you are to a "node" of the telephone network. If you're 100 meters from the node you may get 50 mbps download speed, if you're 1000 meters away you may only reach a maximum of 10 mbps.

 

There's loads more that could be said, your questions are really too general, way too much information to say in a post

 

[_JohnB330ci]

2 hours ago, Lurick said:

No.

 

A MAC address is used to tell Device 1 how to get to Device 2, the MAC address is stripped off at every hop and the destination address becomes the source and the new destination is that of the next device. A MAC address does nothing for security, faster communication, or anything else. It is literally how a packet gets from point A to B at Layer 2 when there is no Layer 3 information (IP Addresses) used by the switch.

Well rip, meh;_

[Guest]

11 hours ago, Carlos1010 said:

Hi all,

So I have some questions about hubs and other network devices because I have been looking into them today.

 

First lets just say you have a hub, and you are alone on your network therefore you are only sending packets outside to the internet and not on your LAN, will this make a difference then having a router?

 

Second, when I watched these videos talking about network devices they also talked about sharing data on the LAN, so are you saying that when sending a email to a person in the same network as you, the packet doesn't go out the hub? It stays inside and with the MAC address gives the data to the person you whom to send it to? (I really don't understand are his Local network sharing they are talking about when referring to these devices) 

 

Thirdly, what's up with these MAC addresses, I literally only learned after looking on the web that it's something your network device uses when it tries to connect to another device on the same network. Is this even true? A good link to a page you think can give a better explanation would be awesome!

 

Lastly, can someone point to me a link to a video (yeah not a article lol) about all these cables that connect like DSL,fiber and another one? I really don't get what it is, is it the cable that's connects the router to the modem or is it the cable that connects to your PC? And also which one are faster and the advantages and disadvantages of each one. 

 

Thanks in advanced and any help is much appreciated. Sorry for the amount of questions, I need a second source to help me! Have a awesome day!

• Network hubs - these were the precursor to current switching and were a simple electrical device designed to send the electrical impulse they received out to every other port. This caused three issues - large broadcast domains, numerous collision domains and sole control.
  • Broadcast domains - these are an area of a network that can be addressed by a switch/hub/router. The issue with broadcast domains is that they can lead to very heavy traffic as the majority of ports don't need the information they send out. In a modern network these are only used when a switch or router is learning the devices that are connected.
  • Collision domains are an electrical issue - because the hub didn't differentiate between each port connected it meant that it would send a signal down to each connected device - if that connected device was trying to transmit at the same time, you'd end up with a collision which lead to packet loss. Technology was introduced to allow time outs between a client and switching device however it still gave packet loss and thus latency/delay in communication. Collision domains still exist in modern switching however instead of every port being addressed by a switch, each port is individually addressed allowing for simultaneous connections which leads me into the 3rd issue.
  • Sole control - a hub was dumb so thus if one device was trying to transmit, all other devices on the connected hub would have to shut up and wait their turn. This leads to higher latency & slow response time.
• Hubs are different to switches and routers. Hubs are a layer 1 device meaning they're entirely dumb and don't use any identifiers, switches use MAC or physical addresses and routers operate at the IP layer.
• For sharing data between two clients on the same LAN, the data doesn't always need to go back to the switch. If the two clients are on the same subnet meaning their IP's are in the same range (10.0.0.5 and 10.0.0.7), generally they don't have to communicate to the router.
  • This is because the switch that they're connected to will have what's called an ARP table (MAC address table) of all connected clients as does the client that the packet is coming from. What this means is that HOST A will send out a packet saying My IP is 10.0.0.5, my MAC is XYZ, my destination is 10.0.0.7, their MAC is WYX - The switch will go Oh, hi,  that MAC address is in my ARP table and is located on interface 3.  The switch builds this ARP table by examining every incoming port and tying the MAC address listed as the source to the port it comes in on. Eg, in that example 10.0.0.5's packet came in on eth2 so the switch will note that any packets destined for HOST A can be sent to eth2. If a switch doesn't have an entry for the MAC address in the destination in its config, it will send the packet to all ports including the uplink to the router.
    • The router will then look at the source & destination IP's of the packet and work in a similar fashion- sending the packet out the interface it knows an IP address is associated with.

This is a very basic explanation of the way switching and routing works as you can have L3 switches and VLAN's however hopefully you get the gist of it.

 

I would strongly recommend taking a look at the OSI model and understanding the differences between especially the first 3 layers.

[U.Ho]

20 hours ago, Lurick said:

No.

 

A MAC address is used to tell Device 1 how to get to Device 2, the MAC address is stripped off at every hop and the destination address becomes the source and the new destination is that of the next device. A MAC address does nothing for security, faster communication, or anything else. It is literally how a packet gets from point A to B at Layer 2 when there is no Layer 3 information (IP Addresses) used by the switch.

Almost there, but not quite.

 

The MAC address is stripped off at every hop, but the destination address does not become the source, since the destination address points to the routing devices' interface for the network the packet came from. A MAC address for the interface for the next network gets added as source MAC instead.

This could actually be pretty important to understand if you're getting into networking.

 

A switch keeps track of which MAC address is behind which port on the switch by adding source MAC/port pairs from incoming packets to its MAC address table (or FIB or CAM table). This could be thought of as a sort of "layer 2 routing table", although it doesn't quite perform the same way.

[U.Ho]

20 hours ago, Lurick said:

No.

 

A MAC address is used to tell Device 1 how to get to Device 2, the MAC address is stripped off at every hop and the destination address becomes the source and the new destination is that of the next device. A MAC address does nothing for security, faster communication, or anything else. It is literally how a packet gets from point A to B at Layer 2 when there is no Layer 3 information (IP Addresses) used by the switch.

Almost there, but not quite.

 

The MAC address is stripped off at every hop, but the destination address does not become the source, since the destination address points to the routing devices' interface for the network the packet came from. A MAC address for the interface for the next network gets added as source MAC instead.

This could actually be pretty important to understand if you're getting into networking.

 

A switch keeps track of which MAC address is behind which port on the switch by adding source MAC/port pairs from incoming packets to its MAC address table (or FIB or CAM table). This could be thought of as a sort of "layer 2 routing table", although it doesn't quite perform the same way.

[Carlos1010]

22 hours ago, Eniqmatic said:

1 - A hub cannot route to the internet. Think of a hub as a dumb device. When a packet is sent and received at a hub, the hub will actually transmit data to all active/connected links till it gets a reply.

2 - Your example isn't valid because the type of email your talking about requires connectivity to a mail server - traditionally found on the internet. Perhaps if you ran your own internal mail server this might work but even then.

4 - Can you please rephrase/reword better?

So you cannot go to google with a hub nor a switch? So are hubs only used for sharing files on the same network? 

[mariushm]

Hubs are not used anymore at all, only switches. Like we all said in this thread, switches are smart and can move data from one port to just another port in the switch, while switches take data from one port and just dump it on all other ports, expecting the devices at the end of each port to throw away what it's not meant for them.

 

Hubs were much cheaper and easier to fabricate as integrated circuits at the beginning (less logic, less transistors, less processing power because of no need to decode the data packets, extract the source and destination addresses from the packets and memorize them to keep track of source network ports and destination network ports)

Today, they're basically extinct, because switches are very cheap, and very easy to manufacture.

 

No, you can't go to an external network with a hub or a switch, both only send data packets between the network ports. There has to be something connected to the switch which then routes the data packets to the ISP (a server, or a router)

Here's for example how the box that my isp gives me works ( cable internet) :

 

TV cable goes in the box into the cable modem part of the box.  The cable modem inside the box decodes the signal and splits it into a digital telephone line (which is made available in the back as phone jacks) and network data (internet)

The network signal goes into the router processor which is the link between what goes into my house and the outside world (the modem which encodes and decodes the data on the tv cable)

The router is then connected to two separate parts, the network switch which makes it possible to have 4 network jacks on the back of the box, and the wireless network card which makes it possible to connect my printer through wireless, my phone, my laptop and so on.

Both devices connected to network ports or through wireless part are like they're connected to a switch, so if I want to transfer data between my laptop on wireless and my computer connected through cable, the box is smart enough to determine that and the data doesn't go outside my house but it's just passed between the wireless card and the switch. Only data packets meant to go outside the local network are passed to the "router" part of the box which processes the data packets and sends them to the cable modem part of the box and then to the ISP.