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When calculating the load for a network, Data leaving the pc is always going to be less than the data from the internet and servers. So is it safe to assume that if you work out the load with data coming to the PC you will produce valid network design?

I have another question in relation to duplex media. Assume the links between the PC and Switch are running at near full capacity 900Mbps Switch to the PC, and 900Mbps out of the pc towards the switch.

With this switch: Prosafe GS728TPS 24 port - 48 auto-sensing RJ45 ports – rated at 1 Gigabit

Would it be able to handle 900Mbps to the pc and 900Mbps from the pc to the switch concurrently?

Below is a diagram to help picture what i'm trying to ask questions about:

Diagram Network

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  • What do the bit rates with the arrows next to the Ethernet connections indicate? The desired available bit rate in that direction? Or maybe the measured bit rate? – Todd Wilcox Apr 8 '15 at 15:35
  • Measured could fluctuate but that's peak load. – Nphot Apr 8 '15 at 15:37
  • Does the one PC in the diagram represent a typical PC on this network or does it represent that the network only has a single PC on it? If it is meant to be a typical example, how many actual PCs does it represent? – Todd Wilcox Apr 8 '15 at 15:38
  • Leme change up the diagram a little to one thats more suitable – Nphot Apr 8 '15 at 15:42
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    Where is the 660 Mbps coming out of the server going? It's not going to the Internet or the PC. – Todd Wilcox Apr 8 '15 at 15:58
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For your first question:

So is it safe to assume that if you work out the load with data coming to the PC you will produce valid network design?

I'm going to say "No" because there are too many other factors that could affect the overall performance. Typically when you start putting a lot of devices on an Ethernet switch, it's actually the backplane speed that becomes an important factor. That measures the maximum total data that can be going through the switch. If you have several different servers and clients, then each one can take a piece of that backplane up to the maximum link speed of the slowest link, so the more links you have the more hit you can put on the backplane.

With just one server and lots of clients, usually you want to maximize the speed of the link the server has to the switch. Rarely are clients connected on too slow a link.

Second question:

Would it be able to handle 900Mbps to the pc and 900Mbps from the pc to the switch concurrently?

In short, "Yes". A PC connected to a 1 Gbps full-duplex port can recieve up to 1 Gbps from the switch at the same time it is sending up to 1 Gbps to the switch. Sometimes network card drivers or other problems on the PC (or less likely, the switch) can prevent actually acheiving these numbers, but that is what full-duplex operation is meant to allow.

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  • Im working with a set of fixed numbers for an assignment, the data going to the server and the internet will always be much much less than than whats coming from the internet and server towards the PC. Thanks I would add plenty of overhead it was just to understand if a media is full duplex will the switch be too. – Nphot Apr 8 '15 at 15:52
  • Would that change how you would consider planning capacity? – Nphot Apr 8 '15 at 15:53
  • I'm not sure I understand your question about what would change how I plan capacity... I guess if I weren't planning capacity for a business network using Ethernet switches that would change how I plan. – Todd Wilcox Apr 8 '15 at 15:57
  • Data coming from servers and from the internet will always be more than the data being sent out towards the servers and internet. So if i plan a network around the data send from the servers to the pc's and from the internet to the pc's would that produce a valid network design? – Nphot Apr 8 '15 at 16:00
  • I don't think I'm the right person to answer that question. In my world a valid network design means two things: 1) It passes traffic reliably and 2) it fits in the budget. Usually in terms of capacity it's whatever we can afford, because if we're not using it now we will in the future - that's how I do capacity planning. First I allocate dollars to a reasonable amount of reliability and then any dollars left over go to buying as much capacity as possible. When the purchase order comes through that's how I know it's "valid". – Todd Wilcox Apr 8 '15 at 16:05

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