Справочное Руководство для Netopia r6100

Filter rule: A filter set is comprised of individual filter rules.

Filter set: A grouping of individual filter rules.

Firewall: A component or set of components that restricts access between a protected network and the Internet 
or between two networks.

Host: A workstation on the network.

Packet: Unit of communication on the Internet.

Packet filter: Packet filters allow or deny packets based on source or destination IP addresses, TCP or UDP 
por ts, or the TCP ACK bit.

Port: A number that defines a par ticular type of ser vice.

All IP packets contain the same basic header information, as follows:

This header information is what the packet filter uses to make filtering decisions. It is impor tant to note that a 
packet filter does not look into the IP data stream (the User Data from above) to make filtering decisions.

TCP: Transmission Control Protocol. TCP provides reliable packet deliver y and has a retransmission 
mechanism (so packets are not lost). RFC793 is the specification for TCP.

UDP: User Datagram Protocol. Unlike TCP, UDP does not guarantee reliable, sequenced packet deliver y. If data 
does not reach its destination, UDP does not retransmit the data. RFC768 is the specification for UDP.

There are many more por ts defined in the Assigned Addresses RFC. The table that follows shows some of these 
por t assignments.

Source IP Address

163.176.132.18

Destination IP Address

163.176.4.27

Source Por t

2541

Destination Por t

80

Protocol

TCP

ACK Bit

Yes

DATA

User Data