Bilbo
01-28-2000, 04:54 PM
What are TCP and UDP in the ipchains and masquerading arena? Do I need both of them, or should I choose just one? I've got IP masquerading running on my box at home connected to a cable modem. I get great download speeds from my server, but on my other machines, it slows to a crawl. I have the latest drivers for the cards, I can ping everything under the sun, but the performace across the network sucks. Please help? If you don't know the answer, can you tell me which config files you would begin altering?
twist
01-28-2000, 05:19 PM
Slowness with IPChains on a fast link.. hmmm. How many rules do you have?? How fast is the machine itself? CPU/RAM? LoadAVG? Kernel Version?
TCP (From www.whatis.com) (http://www.whatis.com))
TCP (Transmission Control Protocol) is a method (protocol) used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.
For example, when an HTML file is sent to you from a Web server, the Transmission Control Protocol (TCP) program layer in that server divides the file into one or more packets, numbers the packets, and then forwards them individually to the IP program layer. Although each packet has the same destination IP address, it may get routed differently through the network. At the other end (the client program in your computer), TCP reassembles the individual packets and waits until they have arrived to forward them to you as a single file.
TCP is known as a connection-oriented protocol, which means that a connection is established and maintained until such time as the message or messages to be exchanged by the application programs at each end have been exchanged. TCP is responsible for ensuring that a message is divided into the packets that IP manages and for reassembling the packets back into the complete message at the other end. In the Open Systems Interconnection (OSI) communication model, TCP is in layer 4, the Transport Layer.
UDP (from www.whatis.com) (http://www.whatis.com))
UDP (User Datagram Protocol) is a communications method (protocol) that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP) and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP. The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.
UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact.
In the Open Systems Interconnection (OSI) communication model, UDP, like TCP, is in layer 4, the Transport Layer.
Bilbo
01-28-2000, 05:24 PM
I used the ruleset from http://www.ecst.csuchico.edu/~dranch/LINUX/TrinityOS-files/rc.firewall-trinityos (customized for my machine)
It's a fairly large file, but I've removed all the extraneous comments for a stripped down version. Are we on the same page here? Is there something I'm missing?
[This message has been edited by Bilbo (edited 28 January 2000).]