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Tough question on planning for WAN network
- Thread starter penghon
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- Thread starter
- #3
er.....getting a T1, E1 in my part of the world is tough enough...let alone E3 or T3...
where can i find the hardcore stuff that calculates right down to the bits of traffic, how much traffic generated by multiple PCs thro the switch and router out via a single WAN link...etc.etc..
where can i find the hardcore stuff that calculates right down to the bits of traffic, how much traffic generated by multiple PCs thro the switch and router out via a single WAN link...etc.etc..
Penghon,
What your asking is impossible for anyone to answer. You need to find out specifically what applications are being used, how often they are being used and if they are bursty or do they have steady traffic. In a lot of networks today, most traffic patterns are bursty. Which makes it even tougher to find out how much bandwidth or pipe you need. If it was me, I'd make a best guess as to how many hosts are going to be using my network, then I'd choose my bandwidth according to that.
For example, if I had an office of 25 hosts, I'd start them out with a 512k line. If after the installation, I find out they are bogging down the connection then I'll upgrade them to a T1. See where I'm going with this?
Tough question to pinpoint exact bandwidth before it's even implemented.
"I can picture a world without war. A world without hate. A world without fear. And I can picture us attacking that world, because they'd never expect it."
- Jack Handey, Deep Thoughts
What your asking is impossible for anyone to answer. You need to find out specifically what applications are being used, how often they are being used and if they are bursty or do they have steady traffic. In a lot of networks today, most traffic patterns are bursty. Which makes it even tougher to find out how much bandwidth or pipe you need. If it was me, I'd make a best guess as to how many hosts are going to be using my network, then I'd choose my bandwidth according to that.
For example, if I had an office of 25 hosts, I'd start them out with a 512k line. If after the installation, I find out they are bogging down the connection then I'll upgrade them to a T1. See where I'm going with this?
Tough question to pinpoint exact bandwidth before it's even implemented.
"I can picture a world without war. A world without hate. A world without fear. And I can picture us attacking that world, because they'd never expect it."
- Jack Handey, Deep Thoughts
to expand on what ipkonfig said...
to start out it's kind of a try-and=see situation. the best you can do is find out all the products that will use the WAN link, see if the software developers can give you a bandwidth estimate per user on each application, then calculate how many concurrent users you will have at one time. Then you can make the best estimate for a pipe size.
after that, using prodcuts like Cicso Netflow in combination with something like NetQoS ( can give you statistics on how much traffic is being used by each application. Another idea would be to use something like a FlukeNetworks WGA or INA ( which can give you the top applications and top protocols by host. There is an available WAN vision option to see the affect on the WAN as well as the LAN. Of course this is a significant capital investment as well, but the benefits of products like that are almost limitless.
to start out it's kind of a try-and=see situation. the best you can do is find out all the products that will use the WAN link, see if the software developers can give you a bandwidth estimate per user on each application, then calculate how many concurrent users you will have at one time. Then you can make the best estimate for a pipe size.
after that, using prodcuts like Cicso Netflow in combination with something like NetQoS ( can give you statistics on how much traffic is being used by each application. Another idea would be to use something like a FlukeNetworks WGA or INA ( which can give you the top applications and top protocols by host. There is an available WAN vision option to see the affect on the WAN as well as the LAN. Of course this is a significant capital investment as well, but the benefits of products like that are almost limitless.
- Thread starter
- #6
Hehe, at least I am correct to say that this question is indeed tough to answer. Maybe if i were to have these constraints:
1) 3 transmit packets per workstation for one application, size is 100KB each, meaning 3*100KB = 300KB = 1600Kb.
2) Internally network is 10BaseT Ethernet
3) 1 receive packet of 100KB (or 800Kb)on request,
4) Response time to retrieve is to be less than 2 seconds
Total no. of workstations can be in a range of 4 to 10.
With the information above, is there a simple rule of thumb to gauge how big a WAN pipe is required?
1) 3 transmit packets per workstation for one application, size is 100KB each, meaning 3*100KB = 300KB = 1600Kb.
2) Internally network is 10BaseT Ethernet
3) 1 receive packet of 100KB (or 800Kb)on request,
4) Response time to retrieve is to be less than 2 seconds
Total no. of workstations can be in a range of 4 to 10.
With the information above, is there a simple rule of thumb to gauge how big a WAN pipe is required?
- Thread starter
- #7
JRollinson
Technical User
Once you have got a basic idea of the bandwidth you will require it may be worth asking your connectivity provider for a service that has a basic guaranteed bandwidth along with a higher "burst" figure.
Over a relatively short period you will be able to ascertain real world requirements using reports on usage which should be available from the provider.
Then you can adjust the guaranteed bandwidth level to suit your actual needs.
In our locale (UK) this is a fairly standard offering.
In your proposed configuration I wouldn't worry too much about what the switches will queue. They are very unlikely to be the point at which bottlenecks will occur. The router however is a different story, it is here that you may want to configure traffic prioritisation and QoS. If you have applications that are very sensitive to latency etc then you can configure the router to prioritise this traffic across the WAN link. If this is a requirement make sure your connectivity provider will support it.
JR
There is a light at the end of the tunnel!............It5 is a flamethrower ;-)
Over a relatively short period you will be able to ascertain real world requirements using reports on usage which should be available from the provider.
Then you can adjust the guaranteed bandwidth level to suit your actual needs.
In our locale (UK) this is a fairly standard offering.
In your proposed configuration I wouldn't worry too much about what the switches will queue. They are very unlikely to be the point at which bottlenecks will occur. The router however is a different story, it is here that you may want to configure traffic prioritisation and QoS. If you have applications that are very sensitive to latency etc then you can configure the router to prioritise this traffic across the WAN link. If this is a requirement make sure your connectivity provider will support it.
JR
There is a light at the end of the tunnel!............It5 is a flamethrower ;-)
ISDN or Cable Modem and they'll be fine, if you are implementing a WAN link that you haven't ever had before,....are new applications being installed that require a WAN connection, or what this decided just because the cost of WAN is going down and the term is being used loosely. Sounds like a very small office and nothing more a Cable connection or ISDN is needed. If you are using specific applications for the WAN side of the house, then what about redundancy (doubt the client is that concerned as their business doesn't sound Internet Intensive....just thoughts.)
If it's a WAN in place, refer to your Design steps and take benchmarks using a LAN sniffer, filter it by IP address, and trace one application at a time. At least you'll get a guess before you implement anything that may change current production.
I use this for much larger work, but it might help you gain a perspective on your "current" bandwidth utilization. Simplify it to meet just the bandwidth metrics as this is for overall network performance metrics.
Reference book I used to make this document, Designing Cisco Networks | ISBN: 1-57870-105-8
I hope this helps. As JRollinson said, I don't think you have to worry about QoS, at worst you may just restrcit Internet access except for the ports and protocols used by the applications in question.
I still say you won't need anything more than a simple high speed connection, unless the applications were the reason for the WAN decision, and then maybe still.
I hope any of this helps you.....Good Luck
If it's a WAN in place, refer to your Design steps and take benchmarks using a LAN sniffer, filter it by IP address, and trace one application at a time. At least you'll get a guess before you implement anything that may change current production.
I use this for much larger work, but it might help you gain a perspective on your "current" bandwidth utilization. Simplify it to meet just the bandwidth metrics as this is for overall network performance metrics.
Reference book I used to make this document, Designing Cisco Networks | ISBN: 1-57870-105-8
I hope this helps. As JRollinson said, I don't think you have to worry about QoS, at worst you may just restrcit Internet access except for the ports and protocols used by the applications in question.
I still say you won't need anything more than a simple high speed connection, unless the applications were the reason for the WAN decision, and then maybe still.
I hope any of this helps you.....Good Luck
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