10.3 Hardware Considerations


10.3 Hardware Considerations

There are several hardware-based techniques you can consider to minimize the effect of images on LAN performance. Those techniques include LAN segmentation, upgrading LAN adapter cards to obtain a higher throughput for servers storing images, upgrading your LAN infrastructure to a new and higher bandwidth capable network, and using LAN switches. Because the use of LAN switches is the focus of Chapter 11, we focus our attention on the first three hardware-based techniques in the remainder of this chapter.

10.3.1 LAN Segmentation

A simple subdivision of a LAN into two or more segments connected by bridges may create more problems than it solves when working with images. To understand why this situation can occur, consider Figure 10.12, which shows two LAN segments interconnected through the use of a bridge, with one segment connected to a gateway that provides access to a mainframe for users connected to both network segments.

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Figure 10.12: LAN Segmentation

If a user on either segment accesses an image application on server B, the transmission of the image can adversely affect users on both segments. In addition, depending on the size of the image and other user activity occurring on segment B, the additional bandwidth used by the image could delay an in-progress mainframe session to the point where it times out. If you can segregate images to server A and have a minimal number of users on segment B requiring access to server A, you can reduce and possibly eliminate the possibility of session timeouts. If you can place all users requiring access to image-based applications on one segment and inter-LAN traffic is primarily time-insensitive electronic mail, you could minimize the effect of image applications on segment B users. However, because many if not most LAN users typically require access to a mixture of applications, it may not be possible to perform the previously mentioned segmentation. Instead, you may have to consider an alternative hardware approach, such as upgrading LAN adapter cards, upgrading your LAN infrastructure, or acquiring LAN switches.

10.3.2 Upgrading Adapter Cards

One of the key bottlenecks hindering network performance is the adapter card used in workstations and servers. For example, the data transfer capability of 10BASE-T Ethernet network interface cards (NICs) can easily vary from 300,000 bytes/sec to over 600,000 bytes/sec. If you do not know the transfer rate of your adapter, you can consider running a predefined test. To do so you should create a large file on your network server and download it to a workstation when you are the only user on the network. By clocking the transfer time and using that time as a divisor to the file size transferred, you can obtain a viable estimate of the NIC's maximum transfer rate. Then, if that rate appears low in comparison to the capability of other NICs, you should consider replacing server and workstation NICs for users who work with images. Because the replacement of NICs is significantly less costly than other hardware alternatives, you might consider placing this option at the top of your hardware list. Readers are referred to Section 6 in Chapter 13 for additional information concerning the performance of network adapter cards.

10.3.3 Upgrading the LAN Infrastructure

Although the title of this section can be considered applicable to the previous sections in this chapter, the author is using it here in the context of upgrading an existing LAN infrastructure to a new and higher bandwidth capable network. This hardware solution might involve replacing a 10BASE-T network by a 100BASE-T, or a Token Ring network by an ATM network and obviously represents the most costly method for handling images. In fact, due to the cost associated with upgrading an entire existing LAN, it should normally be considered as a last resort, with the use of intelligent switching hubs normally providing a more economical method to support the effect of images being transported on LANs. Thus, readers are referred to Chapter 11 for detailed information concerning the operation and utilization of intelligent switches.




Enhancing LAN Performance
Enhancing LAN Performance
ISBN: 0849319420
EAN: 2147483647
Year: 2003
Pages: 111
Authors: Gilbert Held

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