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Switch Uplink & bandwidth question

In article , AcCeSsDeNiEd wrote: :Hi have a switch called A on level/floor A. :Some of it's ports are directly connected to some of our servers and end-users.

:Now, we are also branching out to the floor below us. :I figured to cut costs/time we will uplink a single port from switch A to another Swtich called 'B' :located in floor B.

:Question is, will the performace/speed of users in floor B be slow in accessing the servers on :switch B? Will it result in users B having to share the bandwidth of the single uplink? (e.g :100mbits/100 users)?

Will everything be in the same VLAN? Will everything be in the same IP subnet? If the answer to both is Yes, then the users on switch B will not need to any of the bandwidth of the uplink when they are connecting to servers that are also on switch B. Similarily, the users on switch A will not need to use any of the bandwidth of the uplink when they are connecting to servers that are also on switch A.

If you have users on switch B who are connecting to systems on switch A, or users on switch A who are connecting to servers on switch B, or if different subnets or VLANs are involved and there is only one router (attached to either one of the switches), then all the active connections will share the single link. Whether that is a problem or not will depend upon how much traffic is going over the link.

There are a couple oi issues of varying importance to keep in mind:

- If your users are all using the same nameserver, then the DNS traffic will have to cross the uplink for one of the two groups. Once the IP of the destination system has been determined, user traffic will only have to cross the uplink to get to the appropriate server if the server is on the other floor from the user.

- If you are using NETBIOS, then you should be aware that NETBIOS uses broadcasts, and those broadcasts are going to cross the uplink. Broadcasts are an important part of NETBIOS resource locking, so you can't just filter the broadcasts without unwanted effects. [Well, without -more- unwanted effects, considering it is NETBIOS we're talking about.]

- Internet traffic is going to end up crossing the uplink for one of the two floors, depending where your WAN router is.

- If your filesystem backup device is on the other floor than the device being backed up, then the backup traffic will cross the uplink. Backups can often be automatically scheduled for hours when users won't be working, and so would not interfere with user traffic, but if you have any kind of decent backup device, your backup speeds are going to be limited by the speed of the network. If you have large filesystems, then you might find [as we do] that -user- traffic may rarely need more than the equivilent of 10 Mb/s, but that server-to-server traffic, or especially backups will use the full available bandwidth of the uplink for long periods (generating lots of alarms on whatever program you are using to monitor the health of your network...)

Reply to
Walter Roberson
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Hi folks, I have a fairly simple question (I think it is).

Hi have a switch called A on level/floor A. Some of it's ports are directly connected to some of our servers and end-users.

Now, we are also branching out to the floor below us. I figured to cut costs/time we will uplink a single port from switch A to another Swtich called 'B' located in floor B.

We might end up with 100 over users in floor B in the new future.

Question is, will the performace/speed of users in floor B be slow in accessing the servers on switch B? Will it result in users B having to share the bandwidth of the single uplink? (e.g

100mbits/100 users)?

Thanks

To e-mail, remove the obvious

Reply to
AcCeSsDeNiEd

In article , AcCeSsDeNiEd wrote: :Yes, same VLAN, same subnet, no router between the 2 floors. :From your post so I presume that's bad news for me? :The single uplink will be shared among the users?

Yes.

:Our applications are a file server and oracle database(blobs) which :consists of lots of .pdf scanned files that users consistently access. :So I presumed it was going to be a problem for a 100-base uplink to the :lower floor.

I suggest looking at the server port utilization on the current switch, via a tool such as MRTG. If you find that the port isn't being heavily used now, then it won't be a problem just because you move users.

In -some- instances, load sharing can be effectively dealt with by prioritizing some traffic over others. For example, if the PDF files had ftp:// url's instead of http:// then you could lower the priority on ftp traffic relative to http, so that web pages still showed up quickly but the longer ftp transfers might be slowed to prevent link overload. With a modern switch such as the 2950/3550/3750 family, you can put in fairly fine-grained QoS (in increments as low as 8 Kb/s) to prevent one type of traffic from "hogging" the connection.

:I think I'll start investing into giga-lan (1000) then. :One of our cisco switches has an optical module for gig-lan. Could look :into that too.

That suggests to me that your existing server is only connected at 100 Mb. Will users just be -moving- to the new floor, or will you be getting a lot of -new- users? If they are just moving, then a 100 Mb link from switch A to the server would be the bottleneck [because it would be shared between the users of A and B and no amount of making the uplink faster would help a slow switchserver connection.]

:Any other suggestions? Thanks

A proxy server placed on floor B might help noticably.

My guess is that no matter what you do, you are going to have to put in new risers between the two floors. If that is the case, then the greatest part of the expense is in labour -- the cost of Cat5e or even fibre is small compared to getting in a certified installer. So don't put in just one link, put in several, and if you put in copper now because that's what your switches support, then -also- put in fibre because that's what your next switch will support and that's what you are going to need for 10 gigabit ethernet down the road. Once you have several copper ports in place, you can multiply your bandwidth by using what Cisco would call FastEtherChannel to bind together up to 8 FastEthernet ports to act as a single higher-capacity link. [If you are not planning on Cisco switches, then the feature to look for is LACP, Link Access Control Protocol]. You can do the same think with fibre ports by the way.

You may have heard that fibre is much more expensive, and if you are buying in small quantities then it certainly is -- but the bulk of the cost is in the connectors! If you look at fibre patch cable prices, you will find that the cost of the cable from most places works out as -roughly- $US 50 plus about $1 per metre [prices very a great deal depending on the manufacturer and the retailer. For example, you know that if you buy from Black Box that you should expect to pay 3 times as much as if you could manage to find a different supplier.] If you are getting fibre installed and the run is not straightforward so you cannot effectively use a pre-made cable length, then though you can buy spools of fibre for quite reasonable amounts, you need a professional installer for sure, as the equipment to install connectors or splice fibre is rather specialized.

Reply to
Walter Roberson

Hi there thanks for the help Walter.

Actually I made a typo. It should have been:

"Question is, will the performace/speed of users in floor B be slow in accessing the servers on switch A?"

Should have been 'A' not 'B'. Sorry.

Yes, same VLAN, same subnet, no router between the 2 floors. From your post so I presume that's bad news for me? The single uplink will be shared among the users?

Our applications are a file server and oracle database(blobs) which consists of lots of .pdf scanned files that users consistently access. So I presumed it was going to be a problem for a 100-base uplink to the lower floor.

I think I'll start investing into giga-lan (1000) then. One of our cisco switches has an optical module for gig-lan. Could look into that too.

Any other suggestions? Thanks

another Swtich called 'B'

accessing the servers on

single uplink? (e.g

To e-mail, remove the obvious

Reply to
AcCeSsDeNiEd

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