Monitoring Network Activity

  • Article

Applies To: Windows Server 2003, Windows Server 2003 with SP1

The primary functions of IIS 6.0 are to establish connections for clients, to receive and interpret requests, and to deliver files — all as quickly as possible. The pace at which these vital functions are performed depends, in large part, on two factors: the effective bandwidth of the link between the server and the network, and the capacity of this link and the server to support network resources.

The speed of the network interfaces also affects the pace. Some servers have two or more network interfaces, which are frequently called front-end and back-end servers. Front-end servers are client-accessible Web servers that run application server software, such as IIS, to handle traffic coming from the Internet. Front-end servers can add a layer of protection for your back-end servers, which include database servers, file servers, domain controllers, and WINS servers. Different interfaces do not necessarily run at the same speed. This is the case, for example, if a Web server is connected to a database server by means of a private network.

If more bandwidth is needed, the network must be upgraded or — in the case of shared-resource networks such as Ethernet — the network must be broken into subnets.

Bandwidth and Capacity

The main purpose of most Web servers is to manage input/output (I/O): Requests come in, and pages go out. Handling I/O requires a certain amount of bandwidth and other server resources as well. In addition to IIS 6.0, network I/O involves TCP/IP, which is implemented by Windows Server 2003 TCP/IP.

Network capacity is measured, in part, by the number of connections that the server establishes and maintains. Bandwidth is measured in several ways:

  • By the rate at which bytes are transferred to and from the server.

  • By the rate at which the server sends data packages, which include frames, packets, segments, and datagrams.

  • By the rate at which the server sends and receives files.

Effective bandwidth varies widely and depends upon the transmission capacity of the link, the server configuration, and the server workload. The values for a single server also change as it operates in response to demand and to competition for shared network resources.

To ensure that your network has sufficient bandwidth and capacity for the network activity it must support, monitor the following performance indicators:

  • Data transmission rates at the different Open Systems Interconnection (OSI) layers, because the components that transmit data reside in different layers.

  • File transfer rates, because a Web page often requires multiple file transfers.

  • TCP connections, because a plateau in connections established, or increases in connection failures and connection resets, can indicate insufficient bandwidth.