Cisco Systems RJ-45-to-AUX manual Unshielded Twisted−Pair Cable

bridged networks. To resolve the issue, your network administrator may even upgrade your PC to a faster CPU or more RAM. This allows your PC to generate more input/output (I/O), increasing the saturation on the network. In this type of environment, every data packet is sent to every machine, and each station has to process every frame on the network.

The processors in the PCs handle this task, taking away from the processing power needed for other tasks. Every day, I visit users and networks with this problem. When I upgrade them to a switched network, it is typically a weekend job. The users leave on Friday with their high−powered Pentiums stacked with RAM acting like 486s. When they come back Monday morning, we hear that their computers boot up quickly and run faster, and that Internet pages come up instantly.

In many cases, slow Internet access times were blamed on the users’ WAN connections. The whole time, the problem wasn’t their WAN connections—it was their LAN saturated to a grinding halt with frames from every interface on the network.

When network performance gets this bad, it’s time to call in a Cisco consultant or learn how to implement switching. Either way, you are reading this book because you are very interested in switching or in becoming Cisco certified. Consider yourself a network hero of this generation in training.

To fix the immediate problems on your 10BaseT network with Category 3 or Category 4 cabling, you might need to upgrade to Category 5 cabling and implement a Fast Ethernet network. Then you need to ask yourself, is this only a temporary solution for my network? What types of new technologies are we considering? Are we going to upgrade to Windows 2000? Will we be using Web services or implementing Voice Over IP? Do we have any requirements for using multicast, unicast, video conferencing, or CAD applications? The list of questions goes on. Primarily, you need to ask yourself if this is a temporary solution or one that will stand the test of time.

Unshielded Twisted−Pair Cable

Category 3 unshielded twisted−pair (UTP) is cable certified for bandwidths of up to 10Mbps with signaling rates of up to 16MHz. Category 4 UTP cable is cable certified for bandwidths of up to 16Mbps with signaling rates up to 20MHz. Category 4 cable is classified as voice and data grade cabling. Category 5 cabling is cable certified for bandwidths of up to 100Mbps and signaling rates of up to 100MHz. New cabling standards for Category 5e and Category 6 cable support bandwidths of up to 1Gbps.

In many cases, network administrators don’t realize that implementing a switched network will allow your network to run at almost wire speed. Upgrading the backbone (not the wiring), eliminating the data collisions, making the network segments smaller, and getting those users off hubs and bridges is the answer. In terms of per−port costs, this is usually a much cheaper solution. It’s also a solution you can grow with. Of course, a 100Mbps network never hurts; but even a switched 10BaseT network that has been correctly implemented can have almost the same effect of providing your network with increased performance.

Network performance is usually measured by throughput. Throughput is the overall amount of data traffic that can be carried by the physical lines through the network. It is measured by the maximum amount of data that can pass through any point in your network without suffering packet loss or collisions.

Packet loss is the total number of packets transmitted at the speed of the physical wire minus the number that arrive correctly at their destination. When you have a large percentage of packet losses, your network is functioning less efficiently than it would if the multiple collisions of the transmitted data were eliminated.

The forwarding rate is another consideration in network throughput. The forwarding rate is the number of packets per second that can be transmitted on the physical wire. For example, if you are sending 64−byte packets on a 10BaseT Ethernet network, you can transmit a maximum of about 14,880 packets per second.

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