Netgear DG834 Instructions d'exploitation télécharger pdf (Page 54)

Reference Manual for the Model DG834 ADSL Firewall Router

4-12 Protecting Your Network

Order of Precedence for Rules

As you define new rules, they are added to the tables in the Rules menu, as shown in Figure 4-8:

Figure 4-8: Rules table with examples

For any traffic attempting to pass through the firewall, the packet information is subjected to the

rules in the order shown in the Rules Table, beginning at the top and proceeding to the default rules

at the bottom. In some cases, the order of precedence of two or more rules may be important in

determining the disposition of a packet. The Move button allows you to relocate a defined rule to a

new position in the table.

Services

Services are functions performed by server computers at the request of client computers. For

example, Web servers serve Web pages, time servers serve time and date information, and game

hosts serve data about other players’ moves. When a computer on the Internet sends a request for

service to a server computer, the requested service is identified by a service or port number. This

number appears as the destination port number in the transmitted IP packets. For example, a packet

that is sent with destination port number 80 is an HTTP (Web server) request.

The service numbers for many common protocols are defined by the Internet Engineering Task

Force (IETF) and published in RFC1700, “Assigned Numbers.” Service numbers for other

applications are typically chosen from the range 1024 to 65535 by the authors of the application.

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Netgear DG834 Instructions d'exploitation Page 54