WAN Protocols

What are WAN Protocols?

WAN Protocols are the standardised method of sending data between computers. The protocol will determine how the data is compressed, the error checking to be used, how the sending device will indicate that all data is sent, how the receiving device will declare it’s received everything.

The WAN protocols are found in The Internet Protocol Suite. They are shown below in the diagram showing where they lie in the 4 layer TCP/IP Model. Sometimes, the TCP/IP protocol will be extended to include the physical layer also, but this is fairly uncommon and all protocols will work over all medias.

Just like the OSI model, each protocol must pass the data down the layers to send out information and then send up the layer to receive information. So for example, the File Transfer Protocol will pass its data down to TCP which will pass it down to IT, which will pass it down to Ethernet which will place it on a physical media such as coaxial cable.

To receive the data back, it must travel back through the stacks back to FTP. Each of the protocols on each stack will have its own set of tasks that it must carry out before sending the data on. Using this set group of protocols ensures that computers are capable of communicating between each other and therefore allows compatibility across devices. It is only when manufacturers stray away from these set protocols that compatibility problems will occur.

Figure 1 The Protocols and their Relationship with the TCP/IP Model

The OSI Model

The TCP/IP Protocol suite does not directly map to the OSI model as TCP/IP relies on four layers and the OSI model uses 7. The top three layers of the OSI model map straight to the Application, Presentation and the Session layers of the TCP/IP Suite. Most of the protocols mentioned on this information sheet are found at the application layer of the OSI model; FTP, HTTP, SNMP, Telnet are all found here.

The transport layer, containing UTP and TCP is the same on both models. The network layer is the actual Internet Protocol, as well as a few older alternatives such as X.25.

The data link layer is the same and are the protocols controlling the actual transfer onto the physical line – which is the physical layer that does not appear on the TCP/IP model as it does not ‘care’ about the physical hardware.

The TCP/IP Model ‘squishes’ the top three layers of the OSI Model onto a single layer.

Figure 2 Protocols and their Relationships with the OSI Model

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The transport layer, containing UTP and TCP is the same on both models. The network layer is the actual Internet Protocol, as well as a few older alternatives such as X.25.

The TCP/IP Model ‘squishes’ the top three layers of the OSI Model onto a single layer.

Figure 2 Protocols and their Relationships with the OSI Model

Evaluation of Protocols

Almost all of the protocols of the past couple of decades are still in use in one way or another. Many have gained popularity as they surpass the capabilities of their older equivalents and some are a lot less common than they used to be. As the uses of WANs become more complicated, so must the protocols being used to provide the services expected. In general, older versions of protocols have been phased out and replaced by updated versions with new capabilities for the WANs they are placed on.

HTTP is the standard method of transferring all sorts of webpage across the web. To do this it must reach across to servers to ask for data and then present it using whatever protocol the page is displayed in. For example, a HTML page must be displayed in HTML. A page linking to a zip file will require an unzip based program to handle it.

FTP is an unsecured method of transferring files across the network. It is not considered a good method for secure documents to be sent as any security that has been added can very easily be decrypted and the contents can easily be viewed. All information sent along with the file, for example: passwords or destination are not encrypted and are sent in standard text. This means that anybody with access to the network could pull the file down and check its contents. It sends the file without checking with the other computer if the entire file has been received. Some clients will add an extra level on top of the FTP file that can calculate and check for file completion but this has to be enforced by both clients and is infrequently used. FTP is not really suitable for regular business situations. FTP replaces Simple File Transfer Protocol.

Telnet is a method of connecting two computers together via a remote connection. Usually, the connection is aimed at a headless server. Once the connection is established using Telnet software, the user has access as though they are in front of that computer. SSH has vastly replaced Telnet because of its security problems across networks that are untrusted. Telnet is frequently used in troubleshooting situations where the required software is not available on both computers. Telnet is generally not used so much by businesses anymore as it has been superseded by SSH in most secure network situations.

SMTP is a text based protocol where everything in the email is bundled together and sent. The email is sent to a remote server which ‘pushes’ the email down to the specific DNS. It relies on DNS to find the correct domain name for the recipient and then filters to find the correct username at that domain. As it is a push protocol and not a pull protocol like POP3 or IMAP, it usually requires other protocols to work alongside it. SMPT does not however, have a successor and is considered a staple protocol in the TCP/IP Protocol family.

SNMP is the network management protocol. It relies on a systems being managed by other systems. A piece of software called an agent runs on the user computers and this sends information back to the managing systems via SNMP. The system is designed to monitor available resources and to keep a check on how the users’ computers are acting. When this protocol was first developed i.e. SNMPv1, its role was simple – just to simply monitor the network. It included no security or integrity to ensure that the data being requested was from the correct computers and hadn’t been tampered with in transit apart from an unencrypted password and so was constantly criticized for its security problems. SNMPv2 improved slightly on this issue, and enhanced security was also added. The ability to talk between two managing systems also added the ability to check the integrity of the data being sent as it was possible to check past behaviour against new behaviour.

The newest version, SNMPv3 which was released in 2004, adds this extra layer of security for management’s piece of mind. This means that it is the securest version to date and is therefore considered industry standard with all old versions being deemed obsolete.

NNTP is the standard protocol for reading and posting Usenet submissions. The last update was in 2006 and this further improved the protocol and ensures that it stays the standard method of accessing newsgroups. This protocol is popular with the types of businesses that require access the news posting sites – these are particularly popular with computing based businesses. The IMAP protocol is capable only reading and so is not a viable alternative.

X.25 is a packet switching protocol that predates IP. It is still found in situations where an extremely reliable system is required such as EPOS systems that allow businesses to take debit and credit cards. It is also popular in the developing world where it the cheapest and most reliable method of connecting to the internet. It is much slower than IP as it requires all of its packets to be received before moving the packets again.