This article constitutes section 1, part C, chapter 2 of the CIW Website design manager course and briefly covers: an Networking Protocols.
The OSI/RM (Open Systems Interconnection Reference Model) is not a protocol. It is a standard providing the concepts that most protocols adhere to. The OSI/RM comprise seven layers as shown below. It is essential to know this model well.
|Application||7||The interface to the end user in an OSI environment - supports file transfers, network management and other services|
|Presentation||6||Responsible for providing useful transformations on data to support a standardised application interface and general communications services. For example, it converts text from American Standard Code for Information Exchange (ASCII) format to Extended Binary Coded Decimal Interchange Code (EBCDIC).|
|Session||5||Establishes, manages and terminates connections (sessions) between cooperating applications. Also adds traffic flow information.|
|Transport||4||Provides reliable, transparent transport between end points (the source and destination hosts). Also supports end-to-end error recovery and flow control.|
|Network||3||Organises data into datagrams, or packets. Forwards and routes datagrams to their destinations.|
|Data Link||2||Provides reliable data transfer across the physical link. Frames are transmitted with the necessary synchronisation, error control, and flow control. In short, it prepares the information so that it can be placed on the transmission medium, such as copper wire.
In the IEEE 802 series of LAN standards, the data link layer is divided into two sublayers: The Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The LLC is responsible for error and flow control, and the MAC layer is responsible for placing the data on the transmission medium.
|Physical||1||Concerned with transmission of unstructured bit stream over a physical link. Responsible for the mechanical, electrical and procedural characteristics to establish, maintain and deactivate the physical link.|
A packet is a fixed piece of information sent across the network. It consists of three elements: A Header, The Data, A Trailer. The packer creation process begins with layer 7 of the OSI/RM model and, as the packet traverses the model, each layer adds it’s own header snippet. At the receiving end, as the packet traverse the OSI model each layers strips out it’s header. This allows each layer at the source and destination to communicate.
Some protocols require that a session be established before communication can begin. These are known as Stateful. Others that do not require a session are known as connectionless or stateless.
CRC A Cyclic Redundancy Check is a mathematical calculation that allows the receiving computer to verify that the received packet is valid.
Transport Layer Protocols
The transport layer provides reliable data delivery. Protocols used at this layer include:
- Transmission Control Protocol (TCP)
- Sequenced Packet Exchange Protocol (SPX)
- Appletalk Transaction Protocol (ATP)
Network Layer Protocols
Network Protocols provide addresses used on a network and rules for particular networks. Network protocols include:
- Internet Protocol (IP)
- Internetwork Packet Exchange (IPX)
- Datagram Delivery Protocol (DDP)
TCP/IP is a collection or suite of protocols combing the Transmission Control Protocol, Internet Protocol, User Datagram Protocol, Internet Control Message Protocol and Address Resolution Protocol amongst others.
TablePress Side Effects
The above table has been created using the WordPress plugin TablePress. This plugin works a treat but, I have observed one thing with it.
Absolutely nothing to do with the post content. But, whilst editing this post it has been noted that Yoast SEO has a feature. It does not consider the table content while optimising the content score. The TablePress table stores the table content in the database rather than physically in the post.
The table is populated with data only when the post is rendered for display.
The networking ins-and-outs tend not to be visible to most Internet users. The whole point, I suppose, is that networking is something we all use without knowing and without needing to know.