COSC 85 OSI and TCP/IP Protocol PDF

COSC 85 OSI and TCP/IP Protocol Marc Elvin D. Cerezo College of Engineering and Information Technology Instructor / Professor  OSI Model OSI Model or Open Systems Interconnection is a conce...

COSC 85 OSI and TCP/IP Protocol Marc Elvin D. Cerezo College of Engineering and Information Technology Instructor / Professor  OSI Model OSI Model or Open Systems Interconnection is a conceptual framework used to describe the functions of a networking system. The OSI Model uses layers to give visual description of what is going on with a particular networking system. It consists of 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. College of Engineering and Information Technology  OSI Model College of Engineering and Information Technology Figure 1. OSI Model  Brief History of OSI Model International Standards Organization (ISO) was established in 1947, dedicate to worldwide agreement on international Standards. An ISO standard that covers all aspects of network communication is the Open Systems Interconnection Model (OSI). It was first introduced in the late 1970s. College of Engineering and Information Technology  Application Layer (Layer 7) Application layer is used by Network Applications. The application layer enables the user to access the network. It provides user interfaces and support for services. Network Services 1. File Transfer – FTP (File Transfer Protocol) 2. Web Surfing – HTTP/S (Hypertext Transfer Protocol) 3. Emails – SMTP (Simple Mail Transfer Protocol) 4. Virtual Terminals – TELNET College of Engineering and Information Technology  Presentation Layer (Layer 6) Presentation Layer receives data from applications layer. These data are in the form of numbers or characters. Presentation layer is concerned with the syntax and semantics of the information exchanged between two systems. College of Engineering and Information Technology  Presentation Layer (Layer 6) Translation – converts data to binary format for the machine to understand. DFPLXMANWIO 100110101101 546513289123 Because different computers use different encoding systems, the presentation layer at the sender-dependent format changes the information into a common format and vice versa. College of Engineering and Information Technology  Presentation Layer (Layer 6) Data Compression – reduces the number of bits that are used to represent the original data. DFPLXMANWIO 100110101101 10100110 546513289123 Encryption – enhances the security of the data. Secure Sockets Layer (SSL) is used in the encryption and decryption of the data. College of Engineering and Information Technology  Session Layer (Layer 5) Session layer helps in setting up and managing connection enabling sending and receiving of data followed by termination of connections or sessions. Session layer keeps track of the files being downloaded. For instance, a web browser that contains videos and text files. These text and videos are separated on the web server. Once the user request for it, the web browser will open a separate session College to the of Engineering and web to download each file. Information Technology  Session Layer (Layer 5) Synchronization – the session layer allows a process to add checkpoints, or synchronization points, to a stream of data. Dialog control – it allows the communication between two processes to take place in either half-duplex or full-duplex mode. College of Engineering and Information Technology  Session Layer (Layer 5) Authentication – a process of verifying the user. A session is established between server and the computer once the user is authenticated. Authorization – a process used by server to determine if the user have the permission to access a file or a site. College of Engineering and Information Technology  Transport Layer (Layer 4) Transport layer is responsible for process-to- process delivery of the entire message. The transport layer provides enhancements to the services of the network layer. Its main tasks is to ensure that data sent from one computer arrives reliably, in the correct sequence and without errors at the receiving computer. College of Engineering and Information Technology  Transport Layer (Layer 4) Segmentation – data received from session layer is divided into small data units called segments. Data Data Data Data Units Units Units Each segments contains a source and destination port and sequence number College of Engineering and Information Technology  Transport Layer (Layer 4) In Flow Control, transport layer controls the amount of data transmitted to a level that the receiver can process. For instance, we have a mobile phone that is connected to a server. The server can process data up to 100 mbps while the mobile phone can only process 10 mbps. 100mbps 10mbps College of Engineering and Information Technology  Transport Layer (Layer 4) In Error Control, if some data units never arrive the destination, transport layer uses Automatic Repeat Request schemes to retransmit the lost or corrupted data. Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Connection-Oriented Transmission Connectionless Transmission Gives feedback, therefore data that is No Feedback whether data is really lost can be retransmitted. delivered or not Internet surfing, Emails, FTP, etc. Streaming, Music, Gaming, Voice calls, DNS, etc. College of Engineering and Information Technology  Network Layer (Layer 3) Network layer works for the transmission of received data segment from one computer to another located in different networks. Packets Network 1 Network 2 Segments IP1 IP2 IP1 IP2 Sender Receiver College of Engineering and Information Technology  Network Layer (Layer 3) Logical Addressing – IP addressing (IPv4 or IPv6) is done in network layer. Every computer in a network has a unique IP Address. It assigns sender and receiver IP Addresses to each segment so that each data packet can reach the correct destination. College of Engineering and Information Technology  Network Layer (Layer 3) Routing is a method of moving data packet from source to its destination. It is based on the logical address format of the logical addressing. Path determination is a method which choosing the best possible path for data delivery from source to destination. OSPF (Open Shortest Path First), BGP (Border Getaway Protocol), IS-IS (Intermediate System to Intermediate System) College of Engineering and Information Technology  Data Link Layer (Layer 2) Data Link layer receives packet from network layer which contains IP addresses of sender and receiver. There are two kinds of addressing: Logical Addressing – is done at network layer where sender and receiver’s IP Addresses are assigned to each data packet. Physical Addressing – is done at data link layer where MAC addresses of both devices are assigned to received the data packet. College of Engineering and Information Technology  Data Link Layer (Layer 2) Framing – the data link layer divides the stream of bits received from the network layer into manageable data units called frames. Flow Control – the data link layer imposes a flow control mechanism to avoid overwhelming the receiver. College of Engineering and Information Technology  Data Link Layer (Layer 2) Error Control – adding mechanism to detect and retransmit damaged or lost frames. Access Control – data link protocols are necessary to determine which device has control over the link at any given time. College of Engineering and Information Technology  Physical Layer (Layer 1) Physical Segment Layer Data Transport Layer converts the Packet binaries into Src IP Dst IP Segment Network Layer signals (either Frame Src MAC 1 Dst MAC 2 Packet Data Link Layer electrical, radio or Sequence of Binary Bits BITs optical) Converted College of Engineering and Media Signals Information Technology  Physical Layer (Layer 1) Physical Characteristics of interfaces and medium – physical layer defines the interface between the device and the transmission medium. It also defines the type of transmission medium. Representation of bits – physical layer data consists of a stream of bits with no interpretation. To be transmitted, bits must be encoded into signals, electrical or optical. College of Engineering and Information Technology  Physical Layer (Layer 1) Data Rate – the physical layer defines the duration of a bit, which is how long it lasts. Synchronization of bits – the sender and the receiver clocks must be synchronized. Line configuration – concerned with the connection of devices to the media. College of Engineering and Information Technology  Physical Layer (Layer 1) Physical Topology – it defines how devices are connected to make a network. Transmission mode – it defines the direction of transmission between two devices. College of Engineering and Information Technology