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This chapter is from the book

This chapter is from the book

System Area Network Cards

As processing needs become ever greater and demands on server availability increase, single-server systems are giving way to server clusters. In a server cluster, systems can share storage and processing power and are fault tolerant; that is, if a system in the cluster fails, one of the other systems in the cluster can take over for it and continue processing.

This level of functionality requires many things. It needs operating systems that are capable of being clustered and applications that can do the same. It also requires that the systems in the cluster be able to talk to each other. That's where system area network cards come in.

System area network cards are used in clustered systems to facilitate communication between the devices in the cluster. Figure 3.27 shows how system area network cards are used.

Figure 3.27 How system area network cards are used.

If only two systems are in the cluster, they can be connected directly by a cable. If the cluster has more than two systems, a specialized hub is required.

REVIEW BREAK

Network Devices Summary

The information in this chapter is very important for the Network+ exam. To summarize our coverage of network devices, we have placed some of the key points about each device in Table 3.3. You should learn this information well.

Table 3.3 NETWORK DEVICES SUMMARY

Device

Function/Purpose

Key Points

Hub

Connects devices on a twisted-pair network.

A hub does not perform any tasks besides signal regeneration.

Switch

Connects devices on a twisted-pair network.

A switch forwards data to its destination by using the MAC address embedded in each packet.

Bridge

Divides networks to reduce overall network traffic.

A bridge allows or prevents data from passing through it by reading the MAC address.

Router

Connects networks together.

A router uses the software-configured network address to make forwarding decisions.

Gateway

Translates from one data format to another.

Gateways can be hardware or software based. Any device that translates data formats is called a gateway.

CSU/DSU

Translates digital signals used on a LAN to those used on a WAN.

CSU/DSU functionality is sometimes incorporated into other devices, such as a router with a WAN connection.

Network card

Enables systems to connect to the network.

Network interfaces can be add-in expansion cards, PCMCIA cards, or built-in interfaces.

ISDN terminal adapter

Connects devices to ISDN lines.

ISDN is a digital WAN technology often used in place of slower modem links. ISDN terminal adapters are required to reformat the data format for transmission on ISDN links.

System area network card

Used in server clusters to provide connectivity between nodes.

System area network cards are high-performance devices capable of coping with the demands of clustering applications.

WAP

Provides network capabilities to wireless network devices.

A WAP is often used to connect to a wired network, thereby acting as a link between wired and wireless portions of the network.

Modem

Provides serial communication capabilities across phone lines.

Modems modulate the digital signal into analog at the sending end and perform the reverse function at the receiving end.


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