CODEWITHSUNDEEP
httpnetwork-programmingfirewall
mur
mur

Reputation: 933

How does firewall handle incoming http traffic to a browser?

when a browser sends a request to a web server, the web server has to send a response. from what i have understood from reading so far, the server than dispatches the packets of response data with dest-port/dest-ip parts being the client browser's.

1) If the above is right, than doesn't it mean that the browser has to always be listening to a port for incoming traffic from the server?

2) And if the client is listening for incoming connections on a port, isn't that a security concern?

3) If 2 is right, than how are most corporate firewalls for employees be configured? (seeing as they probably need to browse the net) - a quick overview, details unnecessary.

Upvotes: 0

Views: 3118

Answers (1)

CodeCaster
CodeCaster

Reputation: 151604

doesn't it mean that the browser has to always be listening to a port for incoming traffic from the server?

No. Layman's explanation: a browser initiates a TCP connection to the web server. This connection is recognized by source ip and port, dest ip and port and protocol by all intermediate level 3 machines (e.g. routers, firewalls).

In a TCP connection, one party listens (the web server) while the other party connects (the browser). Traffic can flow over this connection in both directions, until either party (or intermediate machine) closes the connection.

Corporate firewalls allow outbound connections over port 80 (and 443), so their employees can browse the web over HTTP(S). The data the server returns is sent over the connection initiated by the client.

Of course if an outside attacker knows of a connection, they can send packets with a spoofed IP, so they can send data pretending to be the server. Those packets will be dropped if anything is wrong, like the sequence number, so they won't end up in the user's browser.

Upvotes: 3

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