Cisco Systems RJ-45-to-AUX manual Network Design

To improving network performance, switches must address three issues:

∙They must stop unneeded traffic from crossing network segments.

∙They must allow multiple communication paths between segments.

∙They cannot introduce performance degradation.

Routers are also used to improve performance. Routers are typically attached to switches to connect multiple LAN segments. A switch forwards the traffic to the port on the switch to which the destination device is connected, which in turn reduces the traffic to the other devices on the network. Information from the sending device is routed directly to the receiving device. No device other than the router, switch, and end nodes sees or processes the information.

The network now becomes less saturated, more secure, and more efficient at processing information, and precious processor time is freed on the local devices. Routers today are typically placed at the edge of the network and are used to connect WANs, filter traffic, and provide security. See Figure 1.3.

Figure 1.3: Routers and switches

Like bridges, switches perform at OSI Layer 2 by examining the packets and building a forwarding table based on what they hear. Switches differ from bridges by helping to meet the following needs for network designers and administrators:

∙Provide deterministic paths

∙Relieve network bottlenecks

∙Provide deterministic failover for redundancy

∙Allow scalable network growth

∙Provide fast convergence

∙Act as a means to centralize applications and servers

∙Have the capacity to reduce latency

Network Design

When designing or upgrading your network, you need to keep some basic rules of segmenting in mind. You segment your network primarily to relieve network congestion and route data as quickly and efficiently as possible. Segmentation is often necessary to satisfy the bandwidth requirements of a new application or type of information that the network needs to support. Other times, it may be needed due to the increased traffic on the segment or subnet. You should also plan for increased levels of network usage or unplanned increases in network population.

Some areas you need to consider are the types of nodes, user groups, security needs, population of the network, applications used, and the network needs for all the interfaces on the network. When designing your network, you should create it in a hierarchical manner. Doing so provides you with the ability to easily make additions to your network. Another important consideration should be how your data flows through the network.

For example, let’s say your users are intermingled with your servers in the same geographical location. If you create a switched network in which the users’ data must be switched through a number of links to another geographical area and then back again to create a connection between the users and file servers, you have not

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