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To access the contents, click the chapter and section titles.
Oracle Performance Tuning and Optimization
Network Protocols Several very popular network protocols are in use today, including TCP/IP, SPX/IPX, Banyan Vines, AppleTalk, and NetBIOS. This chapter focuses on the two most-popular network protocols: TCP/IP and SPX/IPX. TCP/IP has been in use since the early days of computer networking and is probably the most popular of the network protocols. The network protocol is responsible for the network communication between the different nodes in the network. The network protocol defines how the messages are sent, who receives them, and how or if the data is routed to other machines or networks. The network protocol is also the determining factor about what other applications or protocols can be layered on top of it. TCP/IP TCP/IP (Transmission Control Protocol/Internet Protocol) is the most popular network protocol in use today; it runs on virtually every computer system and operating system. As do the hardware devices, the network protocol wraps the data within a structure called an IP packet. This packet contains information such as the machines IP address, the address of the machine the packet is being sent to, and routing information. TCP/IP has an addressing protocol used to facilitate routing of IP packets. The address is in the form www.xxx.yyy.zzz and is a standard. Typically, the first three sets of numbers www.xxx.yyy are used to identify the subnet on which the machine is located; the final numbers zzz are used to uniquely identify the computer system. Each of the sets of numbers is 8 bits and is known as an octet. For machines on the Internet, the first two octets are registered and are unique to your corporation. The last two octets are available for your own use. Having two octets allows you to divide your network into subnets. A subnet is an individual isolated portion of your network. SPX/IPX SPX/IPX is a network protocol designed by Novell to support the NetWare operating system. Because NetWare was originally designed around file and print services, it required a high-speed network subsystem. As such, the SPX/IPX protocols are very lightweight and high performance. Even though it was originally designed for file and print services, SPX/IPX works very well with SQL*Net. Not only does it provide compatibility with the NetWare server, it is a high-performance network transfer protocol. If you operate in a NetWare network, you can easily take advantage of SPX/IPX by using Oracle and SQL*Net as well as NetWare directory services. SummaryAs you have seen, the performance of the network can be affected by hardware and software inefficiencies as well as the load on the network. Probably the most common problem is the one caused by overloading the network. With every type of network, only a certain amount of data can be simultaneously transferred before the network is overloaded. When an Ethernet network gets extremely busy, you see a large number of collisions. These collisions cause the network to retransmit the data, wasting CPU and network cycles. As you get closer to the limits of the network, you generate more and more collisions. When you add traffic to a Token Ring network, you see a slowdown caused by the amount of time it takes for the token to return to your system. The more machines on the network that need to transmit data, the more delays you see before it is your turn again. In summary, the act of exceeding a fixed load causes most network performance problems. The next chapter looks at some of the ways you can avoid or reduce these problems.
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