Am I right?

[Carlos1010]

Hi all,

Im just going to tell you guys some stuff and can you tell me if im correct.

 

A hub is a device that when giving a packet, it distributes to the whole network automatically. 

 

A switch is the smarter brother of a hub and it soon learns not to give the data to all the devices on the network and learns every IP of every device on the network eventually. 

 

A router is only device of these three that lets devices connect to other networks on the internet.

 

What's a modem used for then? (QUESTION)

 

I might be adding some further question to this thread so if your interested, dont be shy do follow this post for further questions if interested. 

 

Thanks in advanced!

[ARikozuM]

@Electronics Wizardy @leadeater

[done12many2]

4 minutes ago, Carlos1010 said:

A hub is a device that when giving a packet, it distributes to the whole network automatically. 

 

Yep. 

 

4 minutes ago, Carlos1010 said:

 

A switch is the smarter brother of a hub and it soon learns not to give the data to all the devices on the network and learns every IP of every device on the network eventually. 

 

Yes again.

 

4 minutes ago, Carlos1010 said:

 

A router is only device of these three that lets devices connect to other networks on the internet.

 

Yes again.  You're on it tonight!  Think of it as a switch with LAN and WAN.  LAN for your side of a network and WAN for outside of your network (internet).

 

4 minutes ago, Carlos1010 said:

What's a modem used for then? (QUESTION)

 

A modem converts the digital traffic of your LAN network to an analog signal that travels via some type of analog cable like copper phone wires or coax cable.

[Carlos1010]

2 minutes ago, done12many2 said:

A modem converts the digital traffic of your LAN network to an analog signal that travels via some type of analog cable like copper phone wires or coax cable.

So pretty much its the thing that makes you connect to the internet? 

[2FA]

Hubs are Layer 1 devices.

 

Switches are Layer 2 or 3 devices depending on the individual switch.

 

Routers are Layer 3 devices.

 

A modem, short for modulator demodulator, is used to modulate and demodulate digital signals such as packets into an analog signal across a transport medium. Essentially it encodes the digital signal into a sine wave and decodes a sine wave into a digital signal. 

 

[mariushm]

modem is short for modulator - demodulator , it's a device that converts the signal from a format to another,for example from ethernet cable to coaxial cable and backwards, or from ethernet cable to phone line (dsl, adsl, vdsl, isdn are different types of encodings of data as they go through phone lines to ISP)  or optical fiber (well, technically optical fiber is digital, so you won't say a modem but rather converter)

 

and a minor correction... switch doesn't use IP but rather MAC address. A network card can have multiple IP addresses assigned to it, the switch won't care about them but as the data packes are sent by the network card through the cable, each packet has the ethernet address stored inside the packet and the switch reads it and memorizes it.  See https://en.wikipedia.org/wiki/Ethernet_frame

[done12many2]

8 minutes ago, Carlos1010 said:

So pretty much its the thing that makes you connect to the internet? 

 

Yes.  Depending on the type of internet that you subscribe to, you may or may not need a modem.  

 

Most cable and DSL services require them.  That whole digital to analog thing.

 

If you are on fiber, you'll have an ONT (Optical Network Unit), which is usually a box mounted on the outside of your house.  This box converts the digital signal from the fiber into analog to and from your house, if necessary.  It only has to convert to analog if the wiring in your house is something like copper or coax.  If you choose to run ethernet from the WAN on your router directly to the ONT, there's no digital/analog conversion.

[2FA]

26 minutes ago, Carlos1010 said:

A switch is the smarter brother of a hub and it soon learns not to give the data to all the devices on the network and learns every IP of every device on the network eventually.

Also, a Layer 2 switch works off of MAC addresses and a Layer 3 switch works off of IP addresses.

[2FA]

2 minutes ago, mariushm said:

switch doesn't use IP but rather MAC address

That is true for a Layer 2 switch but many new switches these days are Layer 3 and work off of IP addresses.

[Carlos1010]

First thanks for all your responses, I clearly understand now!

Secondly, why do computer on a network sometimes are physically connected to each other? I mean like, can tyou just sent a email to the other person through wifi? Also your probably going to say that they are usually tied to a file server of some sort. Can't the file server be connected to a PC through wifi? Thanks.

[Guest]

10 minutes ago, Carlos1010 said:

First thanks for all your responses, I clearly understand now!

Secondly, why do computer on a network sometimes are physically connected to each other? I mean like, can tyou just sent a email to the other person through wifi? Also your probably going to say that they are usually tied to a file server of some sort. Can't the file server be connected to a PC through wifi? Thanks.

What do you mean exactly? You mean direct communications? Sometimes this is possible however it is generally not done as it requires setup to be done on both clients whereas if there's a router involved, the router handles the communication protocols and the clients are automatically given their IP's.

[mariushm]

Computers are connected directly between them for the fastest possible transfer speed and lowest latency possible. Often, there is one computer that has a web server running on it, and this computer is connected to the Internet through one network card. A second computer is not connected to the internet but is connected to the first computer to a second network card on the first computer which makes this communication between the two computers private and fast, not accessible from the Internet.  This second computer could have a database server running on it and respond to requsts from the web server. 

You can write programs / applications that work as servers of some sort (ftp server, http server, DirectConnect, newsgroup server ) on one computer and as clients on another computer and without having the computers connected to internet you can transfer information between computers.

I often set up a ftp server software on one computer and then start a ftp client on a second computer, to quickly transfer files between the two computers using an easy and logical interface.

In the same way, if a person runs a particular messaging software on their computer, and you have the same messaging software on your computer, then it could be possible to send a message directly to that user through wifi, through local networks, and so on, without need of internet connection. Have a look at something like lan messenger http://lanmsngr.sourceforge.net/  or squiggle http://squiggle.codeplex.com/

 

Other services like email  technically can be made to function without internet access but it's very difficult.  Email in particular relies on domain names, it would be a bit difficult to have an email address that looks like carlos @ 1.2.3.4   Since email addresses have a domain, when an email is sent the program sending the mail needs internet connection to retrieve the DNS records and figure out the mail server associated with that domain in the email address. There can be multiple email servers associated with one domain, it's not always just one.

Email is actually quite complex, lots of things are happening in the background which nowadays are fairly hidden by modern mail services (through web interfaces as gmail or hotmail or yahoo have), and these make things harder to understand by beginners (but easier to use)

here's a couple of very simplified descriptions of how email works : https://www.visiondesign.com/how-does-email-work-a-simple-illustrated-explanation/ and http://www.howtogeek.com/56002/htg-explains-how-does-email-work/

[Electronics Wizardy]

2 hours ago, Carlos1010 said:

Hi all,

Im just going to tell you guys some stuff and can you tell me if im correct.

 

A hub is a device that when giving a packet, it distributes to the whole network automatically. 

 

A switch is the smarter brother of a hub and it soon learns not to give the data to all the devices on the network and learns every IP of every device on the network eventually. 

 

A router is only device of these three that lets devices connect to other networks on the internet.

 

What's a modem used for then? (QUESTION)

 

I might be adding some further question to this thread so if your interested, dont be shy do follow this post for further questions if interested. 

 

Thanks in advanced!

P2 Yes

 

P3 Depends on the switch. A level 2 will use Mac adresses  and a level 3 will use IP

 

P4 For most uses yes, but a level 3 switch can as well

 

P5 converts the ISP's signal from the street to the rj45(normally) in your home

[U.Ho]

A hub is a device that when giving a packet, it distributes to the whole network automatically. 

- No. It distributes to all connected ports. Not the whole network.

 

A switch is the smarter brother of a hub and it soon learns not to give the data to all the devices on the network and learns every IP of every device on the network eventually. 

- No. A switch doesn't deal with network layer ie. IP addresses. A switch learns the MAC addresses of connected hosts and other L3 network devices (router or other gateway mainly) and distributes packets using that information. The first time it hears of a MAC address, it distributes the packet to all ports and whichever port gives an answer gets an entry in the CAM table (or mac address table or whatever, there are many names for it) for that MAC address.

 

A router is only device of these three that lets devices connect to other networks on the internet.

- Yes. There are L3 switches that also do routing, but then again they route so they're kind of routers too. Firewalls can route too in most cases. But that's not one of the three devices.

 

What's a modem used for then? (QUESTION)

- A modem (short for modulator - demodulator) can be thought of as an analogue to digital converter of a kind. I'm not going to go deep into that since I'm a bit rusty on that department, but knowing what it's short for hopefully helps you understand.

[U.Ho]

7 hours ago, Electronics Wizardy said:

 

P3 Depends on the switch. A level 2 will use Mac adresses  and a level 3 will use IP

For switching purposes there's a CAM table that has only mac addresses connected to switch interfaces.

Saying a L3 switch uses IP addresses for switching is incorrect. Switching is a layer 2 operation and can not use IP addresses. L3 switch can route with IP addresses but that's not switching. There are separate ASICs doing these operations.

[Adyn]

8 hours ago, Carlos1010 said:

First thanks for all your responses, I clearly understand now!

Secondly, why do computer on a network sometimes are physically connected to each other? I mean like, can tyou just sent a email to the other person through wifi? Also your probably going to say that they are usually tied to a file server of some sort. Can't the file server be connected to a PC through wifi? Thanks.

It has been mentioned above in relation to the different layers that devices operate at these layers are part of the network OSI model (table from wikipedia below).

 

OSI Model
Layer		Protocol data unit (PDU)	Function[3]
Host layers	7. Application	Data	High-level APIs, including resource sharing, remote file access
	6. Presentation		Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
	5. Session		Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes
	4. Transport	Segment (TCP) / Datagram (UDP)	Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing
Media layers	3. Network	Packet	Structuring and managing a multi-node network, including addressing, routingand traffic control
	2. Data link	Frame	Reliable transmission of data frames between two nodes connected by a physical layer
	1. Physical	Bit	Transmission and reception of raw bit streams over a physical medium

 

So when you for example email the other person even though it is on the same wifi network it does not communicate directly with the other user. With wifi the physical and data link layer are handled by the wireless aspect of the connection but it behaves exactly the same as the above table. Wireless is great for flexibility and mobility but not so good for bandwidth and performance hence using hard wiring. 

 

Source:http://microchip.wikidot.com/wifi:80211-osi

802.11 is a set of data link and physical layer protocols.

Data Link Layer (MAC):
Responsible for reliable link-to-link data transfer

• Channel access (CSMA/CA)
• Addressing
• Frame Validation (management, data, control frames)
• Error detection
• Security Mechanisms

Physical (PHY) Layer:
Responsible for putting bits “on the air”

 

[Emmien]

All wireless access points actually have a switch in, but instead devices on ports, there are devices on WiFi.

 

 

Ethernet cables are faster and more reliable than WiFi. In an office, it is easier and faster to run wires to each work station, than have each on WiFi. Many offices started using computers and Ethernet before WiFi, and the existing cabling can be used still today for fast transfer speeds, which are more reliable than WiFi. Where ever possible, use a cable.

 

There is also optical fiber, which is light travelling down a flexible piece of plastic. This can carry speeds up to 100 gigabits, which is over 10 gigabytes a second.