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Memory in a Core Switch

By epj ·
What is the significance of RAM or SDRAM in a Core switch box? Is there a standard saying that this amount of memory should be installed in a core switch?

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Memory in a Core Switch

by McKayTech In reply to Memory in a Core Switch

The usual primary significance of RAM in a switch is that it is used to create buffers for incoming data when the packets arrive faster than the switch can handle them. With insufficient RAM, packets will be dropped because a buffer cannot be allocated, and that will cause re-sends which lead to congestion which leads to user complaints about network slowness.

The secondary significance of RAM is that each successive revision of the switch operating system (IOS in the case of Cisco) usuallyrequires more RAM so quite often you have to do a hardware memory upgrade before you can do the software/firmware upgrade.

There is no general standard that I know of, but each manufacturer should publish a recommendation and I know that Cisco does that for it's switches. There is a published minimum for each level of software and also some general recommendations related to network size. One of my Catalyst5500 core switches currently has 32meg of RAM and that is proving to be far too small to support the 800 users of our system. The replacement core switches (6509) will have 128/256meg of RAM.

paul

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Memory in a Core Switch

by epj In reply to Memory in a Core Switch

The question was auto-closed by TechRepublic

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Memory in a Core Switch

by Kevin Anderson In reply to Memory in a Core Switch

When you connect a server to a Switch at 100 meg, and have 15 desktops connected at 10 megs each, it is possible for the desktops to send data at a rate of 150 megs/sec which is faster than the server can recieve over a 100 meg connection. When this happens, the switch will hold the extra data in a Buffer until it can send the data on to the server once the line is able to carry it.

Please understand that that this is a gross oversimplification.

Basically, If you have a busy network, you'll need more RAM. If you have a lethargic network, then you may not need very much at all.

Another explanation. You have 5 friends over playing in the back yard. You have 5 baseballs. If each friend has one, and throws it at the same time, then you are overwhelmed and will likely hit nothing. On the other hand, if the first guy throws, and the rest wait until you're ready for the next ball, and they continue throwing one at a time, then you'll hit everything. Same with your network. The switch will decide to hold stuff on your behalf. If there isn't enough RAM, then it can't hold it. (in the above example, this would happen when the 11th ball was introduced at the same time for your 5 friends. Add friends, they can hold more balls. Add ram, and the switch can hold more packets.)

Enjoy.
Kev.

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Memory in a Core Switch

by epj In reply to Memory in a Core Switch

The question was auto-closed by TechRepublic

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Memory in a Core Switch

by epj In reply to Memory in a Core Switch

This question was auto closed due to inactivity

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