I started working on a project that requires some experience in routing that I do not have.
We want to have 2 different networks that are physically in the same building to talk to each other. That is basically what we need to do in a few words.
Now there are some requirements: These 2 networks will have users ( about 10 ) on network1 and file servers on network2 Users have been used to be connected onto the file servers directly through 1Gb switches before( they were on network2 before ). But because of a company split up, we are putting some users into network1. Until the company really splits up they will still have to get access to the file servers.
I have been looking at different products, but also have been trying to see if we could contain prices. I do not know the Cisco products well enough to know which series I should use ( I've only setup small offices using routers and firewalls for broadband connection ).
My question is : What would be the appropriate Cisco series we should look at to allow these 10 users to access their files at a decent speed ( meaning they won't see much difference with what they had before) their files are usually about 10 MB word/excel documents.
I am sorry I should have had notify that I don't necessarely need these people to have 1Gb speed. However, what I am wondering then is: if a router has for example 2 interfaces at 100BaseT, does that mean that the time it will take for a packet to go from a network to another one will be pretty much the same as the time it would take for a packet to go through a 100 BaseT switch ?
I assume not, but would that speed difference ( between a switch and router ) be divided by 2, by 10, by 50 ? ( approximately )
Routing, as far as I remember, requires de-encapsulating and re-encapsulating a bunch of data that a switch doesn't do ( since a switch works at layer2 ). The process of encapsulating, takes CPU and time. But I do not know how to compare this time with a network switch.
With a network as small as 10 users, a Cisco 800 series router is as far as I'd venture. (Though I don't think they have a Gigabit model yet.) I doubt the latency on a 100Mb router interface will be noticeable.
Additionally, since the set-up is temporary and you mentioned keeping the price down, another home router should even do the trick.
The Cisco 3550 and 3750 route and switch at the same speeds. These days, the routing speed for "multilayer switches" or "Layer 3 switches" is often fairly close to the layer 2 switching speed on the same switch.
You might find the summary information useful at
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example it shows that on the Cisco 85x series of routers, the routing performance for short (64 byte) packets is 5.12 megabits per second. As an estimate, you would expect about 20 times that throughput for full-sized TCP packets (i.e., it is limited mostly by the number of packets per second, not by their size.) Depending on the access pattern, the performance might or might not be a noticable difference compared to the gigabit they are getting now.
Thank you very very much, this is a very interesting link you sent me there !
Your example about the 85x series is perfect.
"hack.bac" suggests staying to the lowest level of the Cisco series (
800 ).
Reading the PDF
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( Router Perf ). It seems that they will really get a 5.12 Mbits throughput out of that little 85x device. It is pretty much as fast as cable modem download speed if I am correct ( well at least in some part of the US ) :) Could this be a good example to explain my manager ( who wants to go with the cheapest way ) that the 800 series will be really slow whenever these users are going to start accessing word or PDF documents that could be sometimes 10 to 15 MBytes ?
I am really sorry about all these questions, but I am supposed to design the network for this setup but I do not want to end up having to redo everything because after the first day of work, people complain about speed. Unfortunately ( and I'm sure you guys have been in these situations ) management wants to go with the cheapest way.
The 5.12 Mbit/s is the rate assuming 64 byte packets. For your purposes, you need to get an estimate of the average packet size for whatever file transfer protocol the users will be using to access the files (e.g., SMB or Novell Netware or HTTP). SMB over NETBIOS does not (if I remember correctly) use full sized IP packets; I believe that SMB over IP (port 443) is more efficient. HTTP does use full size packets to send the chunks of data, once the negotiation of what to send how is completed.
Historically, people have noticed that packet distributions tend to be bimodal -- that is, the majority of packets tend to be < 256 bytes, but with another peak in the 1000 to 1500 byte range, with relatively little in the middle. But that's long-term packet counts, and short packets are usually associated with interactive work such as ping or ARP or telnet -- situations in which what is important to people is latency rather than throughput. Something like an 800 series router is going to have a higher latency than a Cisco multilayer switch, but it would depend a lot on the network load and people's expectations as to whether that higher latency would make a noticable difference.
Considering connection setup times, if you are using something like HTTP to transfer the files, you are probably going to average
-roughly- 1 1/3 kilobytes of payload per packet. 15 megabytes divided by 1 1/3 kilobytes .. call it 11000 packets. At 10000 packets per second (the rated 850 performance), that would be about 1.1 seconds to transfer the file; it would probably take longer for Acroread to load the file. 10000 packets per second at
1500 bytes per packet would slightly exceed 100 megabits/second, so the transfer might take slightly longer (especially if the hosts have not been tuned for a high receive window and so on.)
The slowest of the 3750 series, the -24TS, forwards at 6.5 Mpps, about 650 times faster than the 850 -- which means that the limiting factor if you were to connect through one of those would be the line rate (e.g., 100 megabits/second). As we saw above, though, the line rate is fairly close to 100 megabits/second if you are using nearly full packets on the 850 router, so the 3750 would only start to be an advantage if you realistically have contention with multiple people trying to grab those 10-15 megabyte files simultaneously; in such a situation, gigabit to the fileserver would permit multiple hosts to be served at 100 megabits/second.
But we need to take a step back and look at your security. You are talking about the company splitting up, which implies that over time you are likely to want to interpose security between the VLANs. The
850 is going to slow down noticably if you put security on it; the Cat
3750 switch family is relatively limited in the kinds of security you can activate, but has a lot more horsepower. Next question to ask is whether the 850 supports VLANs. And the answer to that is NO -- but the 870 series does; it is about 2 1/2 times faster and so would have more headroom if you decided to activate the firewall features.
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