Routers -vs- Switches? 17
poochie asks "I'm currently in high school taking the Cisco first year course (semester 1 and 2). We're messing around with routers, and I'm starting to get the idea that routers are being outdated. We're learning switches next semester, but from what our instructor says, switches are just more specific to a LAN. In my mind, they seem more versatile in that they actually control their own ports, rather than having a router which is configured to support lans with switches on them, which have to be configured anyway, and make everything more confusing. I dunno about the purpose or the limitations of each, but from what I see, routers make life difficult for small networks. So I guess my question is twofold: Could anyone list resources on the Web about information on routers vs switches, and does anyone see switches taking over routers/hubs in the future, and making network administration a lot easier? "
ask "The Internet company" (Score:1)
Cisco has a smegload of documentation online [cisco.com]. It's mostly product-specific, but some very good general information can also be found.
Here' s the answer [cisco.com] to your question.
and then, just beneath thatThis reminds me of the OSI Seven-Layer Burrito. Unfortunately, it appears to have vanished from the internet. c'est la vie.
Re:ask "The Internet company" (Score:1)
The term "Switch" is abused (Score:4)
A switch is a circuit oriented device. A switch such as the 4E, 5E, or DMS receives a connection initiation and responds by connecting an physical source port to a physical destination port. Everything coming into the source port goes right out the destination port.
The so called layer 2 and 3 switches are nothing of the kind. They receive individual packets or frames and examine them and decide which output port each should be sent to. I don't care whether they're examining the IP address, MAC address, or some other "tag". The function they're doing is routing.
I will grudgingly grant you the term Ethernet switch because each port on an Ethernet switch is connected to a device with a specific MAC address. You can sort of pretend that each Ethernet frame is a mini call and the switch is establishing a circuit from source to destination for the duration of a single frame.
A layer 3 switch is really a router. I don't care how many ASICs it has, it looks at each packet and sends it in the general direction of its destination based on information derived from routing protocols.
Re:The term "Switch" is abused (Score:1)
-Aaron
Re:High school? (Score:1)
I was happy to get Pascal *and* AP Pascal. Networking OS? Not on the Apple IIe.
-sid
Re:The term "Switch" is abused (Score:1)
But, to be more informative, and to relate to the original question, routers will not be replaced by switches (read: bridges). Bridges theoretically have to know the address of every device addressable on their network (read: broadcast domain) Routers deal with layer 3 protocols which have (or at least should have) hierachical addressing. They do not have to keep a forwarding table for every device, only one for every subnetwork, network, or supernet. The current internet has on order of 80K routes. That stretches the capabilities of some routers. I know of few devices that could keep a forwarding table of a billion addresses (one quarter of the IPv4 address space.... which is running out.) and do anything usefull with it. What will happen (and is happening) is that routing functions will begin to be integrated with switching functions.
The way Cisco's "Layer 3 Switches" currently do things is this: The switch is connected to a Route Processor, usually a 7000 series router or an RSP blade. If a packet comes in that is destined for the MAC of the router, it's layer 3 destination is examined and placed into a "flow." When that packet comes back out of the router, that "flow" is completed, and further packets from the same port with the same destination get sent out the port that the original packet went out of, rewritten slightly to reflect what would have happened if it had gone through the router. This increases speed in two ways. First, the packet didn't have to put up with the latency in the router. Two, it only had to traverse the backplane once. There are tradeoffs, of course, but it is a nifty technology. Note, however, that you still need a router in this scenario. And when you don't need a router, it's because your switch is acting like a really stupid (but really fast) router.
Re:High school? (Score:1)
Re:High school? (Score:1)
Re:The term "Switch" is abused (Score:1)
Re:The term "Switch" is abused (Score:1)
Networking info (Score:1)
Re:High school? (Score:1)
Re:High school? (Score:1)
Re:High school? (Score:1)
They've had some pretty stunning technology classes for a while, including classes in web design (a 4 trimester sequence!), and of course CS which they teach in C++. More recently (since I graduated), I'm told they have added classes in Cisco, complete with a lab that has about a dozen routers.
Their home page is http://www.bergen.org/AAST [bergen.org]
Re:The term "Switch" is abused (Score:2)
ATM will take over eventually -- very eventually (Score:1)
check out the Fore Systems site at www.marconi.com.
ATM takes the best features of circuit based
and TDM networks and combines them with cell relay.
It is definitely the more intelligent solution,
however it won't be ubiquitus until all the brute
force methods people are using to speed up WAN
(like IP/WDM) eventually start failing to deliver
guaranteed Quality of Service as consuption increases.
See if you can find the "ATM academy" section of Fore's pages (seems it has moved since I was last there.)
Re:ask "The Internet company" (Score:1)