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Help with Estimating Bandwidth

By SG-1 ·
Hi all,
Our Co. is in need of upgrading the network as it will be expanding. Currently we use a NetWare Server & Win98 Workstations. Been the most experienced, it was asked of me to determine the current bandwidth and future bandwidth required. The budget doesn't allow for pro. consultation. There are ~30 employees in HQ, with another ~30 in 3 regional offices. Only HQ is presently networked. With an existing Client base of ~1,000. The upgrade will also include a website with an interactive office layout planner. New equipment & Cat5e or 6 will be used in the network of HQ & the 3 regional offices (with VPN in upgrade for mobile Sales staff).
Possible WAN connections/services available (e.g., ISDN, ADSL, ATM, etc.) considering bandwidth, performance, security, cost, etc..
Replies ASAP with help on websites, course of actions, additional suggestions, etc. are greatly appreciated.
Thank you kindly in advance.

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by Oldefar In reply to Help with Estimating Band ...

You are dealing with systems ? clients, servers, the communications links, and the applications. Without a system approach, you will have performance issues.

Here is a list of actions I recommend.
1)Identify current and planned applications.
2)Identify a short list of user types (example, managers, sales, admin staff).
3)Identify for each user type the key tasks done with each current or planned application. You want the frequency of the task (daily, weekly, monthly, end of quarter). Make sure you include all critical tasks.
4)Now you need to measure each task as a network load. For this, you at least need a packet capture tool that will allow you to look at source, destination, payload, and time stamp. For better results, script the user actions required to complete the task.
5)With all tasks measured, you can determine client time, server time, and network time to complete each task. You also have network load for the task. If you can run the task both with and without VPN, so much the better since VPN will impact payload and duration.

For a latency factor, ping from the source segment to the destination segment and record the round trip time.
6)The sizing factor is first set by user type, then by the daily tasks, weekly tasks, monthly tasks, and end of quarter tasks. This sets you per user forecast of daily traffic. Multiply by number of each type of user and sum. You will have to consider peak loads based on the tasks. Example ? everyone comes in at 8 AM so the tasks associated with logging in occur then ? load times number of users.
7)You can determine the time distribution of a task by looking at the times and directions of packets. Compute the wire time of each packet (packet size/slow segment Kbps), add latency, and the remainder of the time will be either client or server depending on who was sending and who was responding.

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by Oldefar In reply to

Knowing the current and forecasted load and the performance parameters will lead you to proper bandwidth and latency constraints.

Regarding the type of WAN circuits - this has to be considered in context. Some areas will not have all the possible circuit options.

Other considerations include outsourcing the public Web site. This can reduce the external security issues for the proposed Intranet.

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by Chris910 In reply to Help with Estimating Band ...

Just a comment from the Peanut Gallery.

With a project of this size You need to consider the cost of making an error due to lack of experience. Oldfar has pretty much nailed down what you need to look into with the exception of future growth. But if your experience is limited it will pay you big dividends to to hook up with a knowlegable consultant to help guide you in your planning even if you don't utilize them for the actual implementation.

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by Mike Mullins In reply to Help with Estimating Band ...

I would guess you were looking for how to actually calculate, not postulate. Here's a guideline.

If you are interested in the bandwidth required to run a web server, you can assume that each 64kbps (kilobits per second) of bandwidth can handle between seven and ten simultaneous requests depending upon the size of the content that you are delivering. If you are handling only HTTP clients, expect a similar bandwidth requirement as a Web server serving static pages. That leaves you with estimating the number of simultaneous connections and to get your total inbound web requirement. If you estimate 30 simultaneous inbound web sessions (with 50% growth, this number become 45) and multiply that time 64kbps. You end up with a requirement for 320kbps.

Outbound web/mail/ftp requirement is more or less the same with thirty users you can anticipate that half of them (15) will be accessing an external network at any given time. However, we'll plan for 50% growth and that number becomes (22.5) will require 64kbps or 1440kbps.

Application Bandwidth Requirement
Video Conferencing 384 Kbps
Web Surfing 64Kbps
Remote Access 64Kbps

Multiply the service times the Number of Simultaneous Users equals Total Bandwidth Required.

Basically, you're looking at a T-1 (1536 kbps of user data up and downstream. The other 8 kbps is required for framing information (overhead), adding up to 1544 kbps). Ensure that your service provider conditions the line for data only or you'll lose an additional 1 bit per every 8 bits for RBS (Robbed Bit Signaling) and end up with maximum 1344kbps connection.

And finally this is a synchronous connection, so the speed goes both ways.
Good Luck,

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by DarinR In reply to Help with Estimating Band ...

Here's where you finally get to take advantage.. alittle.. of the vendor
Request some help from 2-3 local isps, lan set-up companies...
they can evaluate your needs, wants and current uses much more easily and quickly, as they do this on a regular basis....
We did this and lo and behold we were paying to much...we even switched to a local mid-sized network provider and now have more bandwidth, pay less, and have a better level of service

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