Справочное Руководство для Netopia r3100-u

Firewall: a component or set of components that restrict 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.

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

Filter Set: A grouping of individual filter rules.

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 datastream (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). RFC 793 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 re transmit the data. RFC 768 is the specification for UDP.

And there are many more por ts defined in the Assigned Addresses RFC.

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