It's some device keeping track of another device or a connection. Ex: When I'm in a forum with my username and password,and accidentally exit the internet browser. After two minuts i re-open the same URL or typed the forum address. I will enter the forum without re-typing my username and password, because it remembered them. It's like cookie.
The weaknesses of static (or stateless) packet filters and stateful packet filters are different in a few ways. Stateless packet filters frequently block SYN scans of networks, but .... Stateless packet filters. (cf. iptables connection tracking), cf. state vs. stateless discussion. confounded application layer protocols like FTP, H323 Because of the nature of connection tracking and state awareness, stateful packet filters are vulnerable to resource exhaustion and deliberate attempts to trip rate-limiting features.
Context-dependent access control
It means that the connection to the Internet is not consistant. This may be caused by a loose wire or other connection, some other hardware problem, or if your connection is shared, there may be enough traffic going through the connection that your machine isn't able to maintain a solid connection to a machine outside of the network.
Connection-Oriented means that when devices communicate, they perform handshaking to set up an end-to-end connection. Connection-Oriented systems can only work in bi-directional communications environments. Connection-less means that no effort is made to set up a dedicated end-to-end connection. Walkie-talkies, or Citizens Band radios are a good examples of connection-less communication.
Depending on what kind of data is being uploaded, either connection could be faster than the other.
Stateful Inspection. A stateful inspection firewall uses a technique known as stateful packet filtering to keep track of communication channels. This is different when compared to basic firewalls. Once the packet and connection has been sent, a normal firewall will not remember the communication channel, whereas the stateful inspection firewall will. This also proves useful to protect connectionless communication protocols.
stateful packet filtering
Stateful inspection works at Network Layer . Many Thanks, Chinmoy Roy
stateful packet inspection
Stateful firewalls use session-based rules to control traffic. The disadvantage of a stateful firewall is that it can be vulnerable to Denial of Service (DoS) attacks if a lot of new connections are opened very fast.
cisco
The method you are referring to is called SPI - Stateful Packet Inspection. A firewall employing SPI is commonly called a stateful firewall.
The weaknesses of static (or stateless) packet filters and stateful packet filters are different in a few ways. Stateless packet filters frequently block SYN scans of networks, but .... Stateless packet filters. (cf. iptables connection tracking), cf. state vs. stateless discussion. confounded application layer protocols like FTP, H323 Because of the nature of connection tracking and state awareness, stateful packet filters are vulnerable to resource exhaustion and deliberate attempts to trip rate-limiting features.
Stateful packet inspection
Context-dependent access control
dynamic state tables
logs stateful inspection