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Introduction To Protocols

Posted in Network Protocols

In the networking and communications area, a protocol is the formal specification that defines the procedures that must be followed when transmitting or receiving data. Protocols define the format, timing, sequence, and error checking used on the network.

In plain english, the above means that if you have 2 or more devices e.g computers which want to communicate, then they need a common "Protocol" which is a set of rules that guide the computers on how and when to talk to each other.

The way this "defenition" happens in computer land is by the RFC's (Requests For Comments) where the IETF (a group of enginners with no life) make up the new standards and protocols and then the major vendors (IBM, Cisco, Microsoft, Novell) follow these standards and implement them in their products to make more money and try to take over this world !

There are hundreads of protocols out there and it is impossible to list them all here, but instead we have included some of the most popular protocols around so you can read up on them and learn more about them.

The table below shows the most popular TCP/IP protocols. The OSI model is there for you to see which layer each of these protocols work at.

One thing which you should keep in mind is that as you move from the lower layers (Physical) to the upper layers (Applications), more processing time is needed by the device that's dealing with the protocol.

          osi-tcp-ip     protocols-osi

Following are the protocols analysed on Firewall.cx:

UDP Protocol - Header

Posted in Network Protocols

This article covers the UDP protocol. We examine the structure of the UDP header, the protocols that use UDP as a transport plus a lot more.

Some common protocols which use UDP are: DNS, TFTP, ARP, RARP and SNMP.

When people refer to "TCP/IP" remember that they are talking about a suite of protocols, and not just one (as most people think). TCP/IP is NOT one protocol. Please see the Protocols section for more information.

The User Datagram Protocol (UDP) is defined by IETF RFC768

File Transfer Protocol - FTP

Posted in Network Protocols

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File transfer is among the most frequently used TCP/IP applications and it accounts for a lot of the network traffic on the Internet. Various standard file transfer protocols existed even before the Internet was available to everyone and it was these early versions of the file transfer software that helped create today's standard known as the File Transfer Protocol (FTP). Most recent specifications of the protocol are listed in RFC 959.


Trivial File Transport Protocol - TFTP

Posted in Network Protocols

TFTP is a file transport protocol and its name suggests it's something close to the FTP protocol (File Transfer Protocol), which is true .. to a degree. TFTP isn't very popular because it's not really used on the Internet because of its limitations which we'll explore next.


The Protocol

TFTP's main difference from FTP is the transport protocol it uses and the lack of any authentication mechanisim. Where FTP uses the robust TCP protocol to establish connections and complete the file transfers, TFTP uses the UDP protocol which is unsecure and has no error checking built in to it (unless they have implemented some type of error checking in the program you are using to transfer files), this also explains why you are more likely to find TFTP in a LAN, rather than a WAN (Wide Area Network) or on the Internet.

IPSec - Internet Protocol Security

Posted in Network Protocols

IPSec is one of the new buzz words these days in the networking security area. It's becoming very popular and also a standard in most operating systems. Windows 2000 fully supports IPSec and that's most probably where you are likely to find it. Routers these days also support IPSec to establish secure links and to ensure that no-one can view or read the data they are exchanging.

When the original IP (Internet Protocol) specification was created, it didn't really include much of a security mechanisim to protect it from potential hackers. There were 2 reasons they didn't give IP some kind of security. First was because back then (we are talking around 30 years ago) most people thought that users and administrators would continue to behave fairly well and not make any serious attempts to compromise other people's traffic. Second reason was because the cryptographic technology needed to provide adequate security simply wasn't widely available and in most cases not even known about!


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