Predicting the Impact of Modifying, Adding, or Removing Network Services

All network services require a certain amount of network resources in order to function. The amount of resources required depends on the exact service being used. Before implementing or removing any service on a network, it is very important to understand the impact that these services can have on the entire network. To provide some idea of the demands various services place on the network, this section outlines some of the most common network services and the impact their addition, modification, or removal might have on the network and clients.

Adding, Modifying, or Removing DHCP

DHCP automatically assigns TCP/IP addressing to computers when they join the network and automatically renews the addresses before they expire. The advantage of using DHCP is the reduced number of addressing errors, which makes network maintenance much easier.

One of the biggest benefits of using DHCP is that the reconfiguration of IP addressing can be performed from a central location, with little or no effect on the clients. In fact, you can reconfigure an entire IP addressing system without the users noticing. As always, a cost is associated with everything good, and with DHCP, the cost is increased network traffic.

You know what the function of DHCP is and the service it provides to the network, but what impact does the DHCP service have on the network itself? Some network services can consume huge amounts of network bandwidth, but DHCP is not one of them. The traffic generated between the DHCP server and the DHCP client is minimal during normal usage periods.

The bulk of the network traffic generated by DHCP occurs during two phases of the DHCP communication process: when the lease of the IP address is initially granted to the client system and when that lease is renewed. The entire DHCP communication process takes less than a second, but if there are a very large number of client systems, the communication process can slow down the network.

For most network environments, the traffic generated by the DHCP service is negligible. For environments in which DHCP traffic is a concern, you can reduce this traffic by increasing the lease duration for the client systems, thereby reducing communication between the DHCP client and the server.

If the DHCP service has to be removed, it can have a significant impact on network users. All client systems require a valid IP address to get onto the network. If DHCP is unavailable, each client system would need to be configured with a static IP address. Because DHCP IP addressing is automatic and does not assign duplicate IP addresses, as sometimes happens with manual entries, DHCP is the preferred method of network IP assignment.

If DHCP is added to a network, all client systems will need to be configured to use DHCP. In a Windows environment, this is as easy as selecting a radio button to use DHCP. If client systems are not configured to use the DHCP server, they will not be able to access the network.

Adding, Modifying, or Removing WINS

WINS is used on Microsoft networks to facilitate communications between computers by resolving NetBIOS names to IP addresses. Each time a computer starts, it registers itself with a WINS server by contacting that server over the network. If that system then needs to contact another device on the network, it can contact the WINS server to get the NetBIOS name resolved to an IP address. If you are thinking about not using WINS, you should know that the alternative is for computers to identify themselves and resolve NetBIOS names to IP addresses via broadcasts. Broadcasts are inefficient because all data is transmitted to every device on the network segment. Broadcasts can be a significant problem for large network segments. Also, if a network has more than one segment, you cannot browse to remote segments because broadcasts are not typically forwarded by routers, which will eliminate this method of resolution.

Because WINS actually replaces the broadcast communication on a network, it has a positive impact on network resources and bandwidth usage. This does not mean that WINS does not generate any network trafficjust that the traffic is more organized and efficient. The amount of network traffic generated by WINS clients to a WINS server is minimal and should not have a negative impact in most network environments.

WINS server information can be entered manually into the TCP/IP configuration on a system, or it can be supplied via DHCP. If the WINS server addresses change and the client configuration is being performed manually, each system needs to be reconfigured with the new WINS server addresses. If you are using DHCP, you need to update only the DHCP scope with the new information.

Removing WINS from a network increases the amount of broadcast traffic and can potentially limit browsing to a single segment unless another method of resolution (such as the use of the statically maintained LMHOSTS file) is in place.

Adding, Modifying, or Removing DNS

The function of DNS is to resolve hostnames to IP addresses. Without such a service, network users would have to identify a remote system by its IP address rather than by its easy-to-remember hostname.

Name resolution can be provided dynamically by a DNS server, or it can be accomplished statically, using the HOSTS file on the client system. If you are using a DNS server, the IP address of the DNS server is required. DNS server addresses can be entered manually, or they can be supplied through a DHCP server.