Network and Computing Services

Network Switches

Network switches integrate intelligent network services with advanced network technologies to strengthen integrity and performance. A quality network switch provides enhanced functionality and intelligence to help organizations simplify and automate complex tasks while supporting new applications and business requirements.

Most enterprise organizations find that providing information to external customers and internal users in a timely and reliable manner is a significant challenge. Failure to meet this challenge can result in slow or unreliable information systems, which can lead to loss of business; conversely, fast and reliable systems can create significant competitive advantage. Information systems also need to adapt to changing requirements such as changes in product lines, office locations, customers’ purchasing habits, technology evolution, and acquisition of other organizations. In other words, organizations require agile information systems that can grow with time and not impose restraints on growth in the future.

At the heart of an information system is the computer network. Routers and switches are two critical components in the network; proper selection of these key devices helps ensure that the network provides fast and reliable service and can adapt to fast changing needs. High levels of reliability are also required as customers become more dependent on critical services such as online purchasing and rapid delivery of purchased products. Poor reliability can lead to loss of customer goodwill and potential business; conversely, good reliability helps ensure customer retention.

Higher returns are being demanded of the investments in IT infrastructure all the time; therefore, overall costs need to be controlled. A well-designed network, with properly placed routers and switches, can help reduce the operational costs and improve the availability, manageability, reliability, and utilization of expensive resources such as telephone links.

The Network Backbone

A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model. Network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately. By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth and offers generally excellent performance.

Switches are used to link segments of a network and allow data to move between these segments. All switches operate at layer 2 of the OSI model and examine layer 2 addresses; for example, layer 2 address for Ethernet is the MAC address. Some switches also provide additional functions such as virtual local area networks (VLANs) and layer 3 switching.

Switches, like hubs, have multiple ports and link a device to another device. However, they examine the destination MAC address of the incoming frames and send it only to the port of the destination device, instead of sending it to every port. Data does not flood the network and thus the load on the network is reduced. A switch can be suitably configured to examine the incoming frames and prevent forwarding of packets that are in error, for example after a collision. Therefore, a switch can be a termination point in a collision domain.

As the switch price (per port) dropped considerably, it became a norm to attach a single device to each port. This is known as “switched” Ethernet rather than the “shared” Ethernet provided by hubs. With only one active device per port there can be no collisions, so network performance is improved and devices can also run in full duplex to achieve even higher throughput.

The switching process is done in hardware at wire-speed with effectively no latency. The switch learns the MAC address of each device and its corresponding port, but before it discovers this address, it has to flood the network by sending the frame to every port. Additionally, broadcast messages also have to be copied to every port and this can have a significant impact in a large network. Switches do not terminate a broadcast domain and therefore the network should be designed to reduce the spread of broadcasts.

Because most users want to communicate with a limited group of servers and associates, any broadcast traffic usually needs to be sent just within that group. One method of reducing the broadcast traffic is to provide a switch for each group and then link them together with a router because a router does not transmit broadcasts. Another method is to use VLANs on the switch.

A VLAN is a group of devices that are configured (using management software) to communicate as if they were attached to the same wire, when in fact they are located on a number of different physical LAN segments. A broadcast from one member of the VLAN only goes to other members of the same VLAN thereby reducing the spread of broadcast traffic

Ethernet implementations of network switches is most common. Mainstream Ethernet network switches support either 10 Mbps, 100 Mbps (Megabit), or 10/100/1000 Mbps (Gigabit) Ethernet standards.

Different models of network switches support differing numbers of connected devices. Most consumer-grade network switches provide eight, sixteen, twenty-four, or forty-eight connections for Ethernet devices. Switches can be connected to each other via daisy chaining, allowing for progressively larger number of devices to join the same LAN.

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