OK, I give. What's the diff among a switch, hub, and a router?

[tewetzel]

Right now at my folk's we have a cable modem hooked to a hub, which then feeds their machine (Win2k Pro) and my machine (WinXP Pro). This is used purely for internet access. Well, I keep hearing people scream that I shouldn't use a hub. Especially w/ our recent internet access problem, I posted on another site and *everybody* badmouthed the hub. Most everybody said, "Ditch ZoneAlarm and the hub, get a router w/ a hardware firewall." They went on to recommend a "Barracuda" which can be had for around $50 they said.

Why is this? Feel free to give the super-techie answer. If I still don't understand I'll ask for the layman answer.

[Kansaidan]

Hub: Generally no intelligence. Used to attach several boxes to one pipeline, SO BANDWIDTH IS SHARED. For example, 100MB pipeline funneled into a 10 port hub gives each port, and therefore system, 10MB.

Switch: More intelligence. Offers DEDICATED bandwidth to each port. In scenario above, instead of 10MB to each port, a switch will allocate 100MB to each system or more depending on duplex.

Router: Very intelligent. Makes intelligent forwarding decisions based upon network IP address and other factors, all of which are configurable. Routers are used to define networks and sub-networks, and are the workhorse that allow the Internet to function. Routers are at the top of the heirarchy, which means they generally carry backbone highspeed traffic. However, switches carry this traffic also, and routers are used at the small office and home level, too.

This is very general. Are you confused now?

[tewetzel]

So you're saying that rocky road is better than chocolate chip?

OK, that makes sense. So what problems might one run into when using a hub in my configuration?

[paras]

Lemme try to get it across to you.

All devices need to work on some address scheme and some way to transmit data packets.

I will take typical situations. There is something called the OSI model which is basically a structure defined to help provide guidelines to developers (both software and hardware) so that they do not have to worry about how their stuff will work with different technologies and implemenatations. This OSI model has 7 layers that start at the physical layer (all the hardware used for connecting like hubs, cable, connectors, etc.) and ends at the top with application layer (applications like Outlook Express, MS Word, etc.).

They just need to decide what functionality they want it to have. This gives the whole systems and communications thing a modular approach. Practically it means that if Intel decides to design and build an Ethernet Network Interface Card (NIC), they do not have to worry about how MS Word will interact with that card when you try to open a file across a network or how your email program will get the email across. They just need to make sure that their product fits all specifications for that particular layer. It is like as if you were working in a big organization and you were just in charge of the inventory. You just need to make that table at the end of what is there in the inventory. How it affects sales, how the organization will refill the inventory, project sales, purchase, etc. is not your concern.

Now with addresses. I will take only the most commonly used addressing schemes/types. The function of addresses is to be able to identify nodes (computers) or hosts on the network/internetwork. There are Internet Protocol (IP) addresses which are part of the whole TCP/IP bandwagon. IP works at Layer 3 of that OSI model. It is hierarchial in nature. Which means there are different Classes of IP addresses. Some are reserved. Some are used to identify hosts that are accessible by public (like web server that host sites like www.google.com etc.). Some IP are reserved for private use which means that they are not on the public network (internet). And still, some are used for special purposes. One of those purposes I will address later when I tell you about your own network.

Then there are MAC addresses which are basically hardware addresses. These are burnt into the network card (or network interface to be more specific). In fact, each network card in the whole world has a unique MAC address. (however, there are ways to spoof this too). The first half of this address is the manufacturer ID (and is assigned to him by an international body that controls this) and the second half is like the serial number of the particular piece which is assigned by the manufacturer. This addressing is a flat scheme. Which means that there are no classes or types. This address works at the Data Link layer which is layer 2 of the OSI model.

Note that the OSI has a down-to-top layer structure, which means that layer 1 (physical) is at the bottom and layer 7 (applicaiton) is right at the top.

The computer name that you assign is specific only to a local network and is not recognized anywhere outside it.

Now, no matter what, ultimately all address have to be resolved to the MAC address for the data packets to be sent to the next intermediate device on the network and finally to the destination.

With this rather confusing background, I will proceed now to try and explaint he difference betweent hub, switch and router.

A hub is a layer 1 device. Which means that it cannot make any decisions. If it receives any data packet on one port, it will simply forward it to all ports on the hub. All devices connected to it will see it but only that one to which the packet has been addressed, will retain it and the open it to check the contents, etc.

A switch is a layer 2 device and therefore uses MAC addresses. It can make some decisions. For example, if I have 4 PCs connected to a switch and PC1 starts a "conversation" with PC3, then the switch will create a virtual circuit between its ports to which PC1 and PC3 are connected. Thus the 2 communicating devices have dedicated bandwidth. Now suppose this PC3 was your ISPs server that connects you to the internet and all you internet traffic goes through it. Guess what would happen? The same. All decisions that a switch are based on MAC addresses. Whenever a switch receives a packet, it looks at the destination MAC address and then looks up its table and sees which of its ports has that MAC address connected to it and simply forwards the packet to that port only.

A router is a layer 3 (network layer) device. It works with IP addresses. It is a more intellegent and definitely expensive device. What a router does is when it receives a packet, it sees the destination IP address. Then it looks up its table to see which path is the best to send the packet through. (On the internet or any internetwork, there can be more than 1 way to reach the same destination). It then puts its own MAC address in the source MAC address field (it can do this because the MAC address is its own and therefore it does not have to be checked against a table or processed or anything) and it sends it across to the next router in the path. That router will take a look and operate in the same way till the packet finally reaches the destination. What this means is that the destination IP address always remains the same but the source MAC address keeps changing.

It is a lot confusing if you have not studied it and there may be many questions that you have that will come up. But we can leave that aside for now because it is a rather deeper study than I have been able to put here.

Now let is come to your network

Typically in the cable modem scenario, you would have got IP addresses from your ISP. Most ISPs allow only 1 IP address to access the internet via the cable modem (even if they give you more than 1). This is to make you have the cable modem on only 1 computer. If you want to use another computer, you have to pay for the use of another IP. However, there are ways to mask that you are using only 1 IP. This can be done by a router.

From your other post, I figure that the problem there was firewalling programs and address resolutions not working.

Coming back to you main question. Why are hubs not recommended?

This is the case. With hubs, you can end up with having problems like yours because the configuration is gets messed up. Your computers are open for others to see. Your ISP may not support use of 2 computers with 1 IP address etc.

It works with a hub but can get screwed up like it did in your case. And from my experience, especially when using firewalling programs. Like it happened just a few days back with one of my clients trying to use Norton Antivirus 2002.

The best setup from experience is to have a broadband sharing routers (I got a Linksys for my client) and configure it with the 1 IP that the ISP allows. But I enabled DHCP on the router so that the clients could get their IPs and be able to access the internet through the same cable modem connection and even see each other. Now the network is not open for others to see and yet has internet connection sharing as well as LAN connectivity.

If you need any clarifications, do post back.

Have a nice day.

[tewetzel]

OK, that all makes sense. Thanks. Don't think I wanna go any deeper at this point. lol

One question I still have though: How can it work fine for 2yrs in that configuration and suddenly c**p out?

Also, FYI, I'm also running NAV 2002. It's been okay on my PC (WinXP Pro), but for a long while the auto-protect on the Win2k box has been broken (stays disabled and says it can't start it up when I try to enable it). But that's another story...

[tewetzel]

What do you think is the best router for my configuration, and where is a good place to shop for it? -tew

[paras]

Excuse my language but they say s**t happens.

There is a logical and technical reason for it to have happened. However, to be able to explain it at this point is not possible. It was the same thing with this client. Everything working fine for a long time and one day it c**ps out. Of course, in his case the Norton did it. In your case it could be possible that with multiple firewalling programs like zone alarm and norton etc. at some point the routing and connectivity got corrupted.

[tewetzel]

OK, that makes sense.

Which of these looks better for me:

SMC Barricade SMC7004VBR

SMC Barricade SMC7004ABR

[paras]

There was another thing that makes a big difference between a router and a hub that completely slipped my mind because to me that is very obvious and I kicked myself for it!

It is this way. Communication can be either half-duplex, full-duplex or simplex. What are these? Half duplex means that the link can send and receive over the same channel but not simultaneously. It can either send and then receive or vice versa, but not together. Full-duplex is where the link can send and receive data simultaneously. And simplex is the link can either send data or receive data (like a one-way street). If it is configured and negotiated for send operation, it will not be able to receive at any point during the communication session.

Now practically, this is what it means. If you have full-duplex, it works faster and if you have half-duplex it is slower. Most modern network cards are full-duplex 100Mbps. However, a hub is a half-duplex device. So if you put a hub anywhere in the line of comunication, the whole show becomes slower. If you have a router, it is most likely full-duplex and so when the whole communication channel works, it works at full-duplex (unless some other protocol forces a half-duplex or simplex communciation for whatever purposes of the developer - although this is not usually done except for in specific required cases). Thus, the router should increase your speed of internet access.

Now I took a look at those 2 models you proposed. We basically need DHCP capability (what they list as Dynamic IP), NAT & TCP/IP.

Both routers have these capabilities. The difference is that the model SMC7004ABR provides for more LAN network features than the SMC7004VBR router. One such feature difference is that with the SMC7004ABR you can plug in a printer to the router and share it for the LAN. Pretty attractive and if I wanted those features and had a couple of tenners extra, I would buy SMC7004ABR. However, if all those features are not needed, then we can talk about SMC7004VBR which has basically been designed for broadband sharing and it will also give all regular network capability for the LAN.

Bottom line.

If I want extra features above broadband internet connection sharing and LAN go for SMC7004ABR.

If I do not want too much on features but enough for LAN and broadband internet connection sharing go for SMC7004VBR.

[tewetzel]

Thanks for the advice! -tim

[paras]

Welcom sir.

It would be good if you could post on this forum how you ultimately configure your setup with all those firewalling software details included. Would help a bloke who needed some information and assistance.

Have a nice day.

[tewetzel]

Originally posted by paras
It would be good if you could post on this forum how you ultimately configure your setup with all those firewalling software details included. Would help a bloke who needed some information and assistance.

I sure will.

[Newt]

To answer your "which SMC router" question, the difference is the ABR has
One DB-9 port for PSTN/ISDN connection
One DB-25 printer port
and costs $18 more. If you need the ports, pay the extra but if you don't, no need to spend the extra. Both will do an identical job of handling your PC network.

However, I didn't see either one list NAT or DHCP and if they do not have those features, I'd suggest Linksys, DLink, Netgear router/switches which are in the same price range.

No NAT will mean you have to pay for an IP address for each PC. NAT means you only need pay for one IP address to run up to 254 PCs connected to the internet thru the router.

No DHCP means you have to set the networking parameters on each PC or let the ISP do it if they have DHCP.

[Moridin]

Nice explanation of the differences between hubs, routers, and switches pasas. I have just one thing to add. The primary reason routers are used (home networks notwithstanding) in networks is to connect different types of networks. For example as long as you stick to Ethernet, you can use switches to connect all your devices. Routers are insensitive to the underlying transmission protocol. That means they can relay data from an Ethernet LAN, to an ATM WAN, another router could then relay messages from the ATM WAN to a token Ring LAN. The Ethernet switch could not on its own talk to either of these two networks as the underlying layer 1 and 2 protocols are different. The only way to connect computers of differing networks such as these is a router (or higher level device like a Gateway.)

[DocDon]

Dear Paras,

Very clear description of the differences between hubs, switches and routers!

With your permission, I'd like to keep it as a reference article in my consulting business. Proper attribution will be given.

This is the type of post I love to see!