There are two main models in the way we describe the transfer and the information flow between users on a network. They are the OSI model and the TCP/IP Stacks or protocol.
We will be going through the diagram or model shown here. As you can see the Osi model has 7 Layers while TCP/IP stacks only have 4 layers.
We will start by outlining the Layers of the OSI and TCP/IP Model. We will READ GENERAL COMPARISON>>>>
The Session Layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e. a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. In case of a connection loss this protocol may try to recover the connection. AppleTalk was actually a session level protocol, as well as netbios, which for the hackers among us is a wonderful entry point to old windows 2000, and 2003 servers.
The Presentation Layer is responsible for the delivery and formatting of information to the application layer for further processing or display. The Presentation Layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in form of datagrams or packets between hosts. The idea is that the application layer should be able to point at the data to be moved, and the Presentation Layer will deal with the rest. Encryption is typically done at this level too, although it can be done on the Application , Session , Transport , or Network Layers; each having its own advantages and disadvantages.
In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications across an Internet Protocol (IP) network. Application Layer methods use the underlying Transport Layer protocols to establish host-to-host connections.In the OSI model, the definition of its Application Layer is narrower in scope, explicitly distinguishing additional functionality above the Transport Layer at two additional levels, the Session Layer and the Presentation Layer . OSI specifies strict modular separation of functionality at these layers and provides protocol implementations for each layer. Telnet, FTP, DNS, and DHCP are all network protocols that operate at the Application Layer.
In computer networking , the Transport Layer provides end-to-end communication services for applications. Transport layers are contained in both the TCP/IP model ( RFC 1122 ), [2] which is the foundation of the Internet , and the Open Systems Interconnection (OSI) model of general networking.
The most well-known transport protocol is the Transmission Control Protocol (TCP). It lent its name to the title of the entire Internet Protocol Suite , TCP/IP . It is used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions. TCP is the more complex protocol, due to its stateful design incorporating reliable transmission and data stream services.
Another port we use is 5405 whch is the connection point for NetSupport. Ports are essentially a place where a service is running and listening for traffic, how we handle these ports and the configuration on them help determine security, outside scope of this class.
All of our Routers use Layer3 or the Internet layer to operate. Routers function by using routing table and identifying the destination and routing it accordingly. This is just one step in the packing and unpacking of network packets
The data link layer devices such as the Switch operate there. Switches operate by making a connection to another device using the Mac address of said device. All network devices have a MAC Address. This is the unique physical identifier on a network. No two Mac addresses are supposed to be the same, however there are rare instances where they can be duplicated as each manufacturer gets a block of around 16 million. A hub operates at the physical layer. All a hub does is make a physical connection. It does not make any sort of connection between devices so all traffic is broadcasted to everyone on the network. This is extremely inefficient and hubs are for the most part phased out of networks as they create large amounts of congestion.
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