1 / 36

Functions (Responsibilities) of Layers 1. Physical Layer

Functions (Responsibilities) of Layers 1. Physical Layer To carry a bit stream over a physical medium. It deals with the mechanical and electrical specifications of the interface and transmission medium. Bit Steam. Bit Steam. Functions of physical layer

hbarr
Télécharger la présentation

Functions (Responsibilities) of Layers 1. Physical Layer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Functions (Responsibilities) of Layers 1. Physical Layer • To carry a bit stream over a physical medium. • It deals with the mechanical and electrical specifications of the interface and transmission medium. Bit Steam Bit Steam

  2. Functions of physical layer • Physical characteristics of interfaces and medium: characteristics of Interface between devices and types of transmission media. • Representation of bits: It encodes the bit stream into electrical or optical signal. • Data rate: Transmission rate, number of bits sent each second. • Synchronization of bits: Sender and the receiver clocks must be synchronized. • Line configuration: Connection of devices to the media. Point-to-point or multipoint connection. • Physical topology: How devices are connected to make a network? • Transmission mode: It defines direction of the transmission between two devices. Ex. Simplex , half-duplex or full duplex mode).

  3. 2. Data Link Layer • The data link layer takes a datagram and encapsulated it in a packet called frame. Functions of Data Link Layer • Framing: Data received from network layer the manageable unit is called frame. • Physical addressing : Adds header to the frame defines sender and receiver. • Flow control: Difference between data transmission. • Error control: Data link layer adding mechanism to detect and retransmit damaged or lost frames. • Access control: Multiple links are connected to same link.

  4. 3. Network Layer • Responsible for the source-to-destination delivery of a packet, possibly across multiple networks (links). Functions of Network Layer • Logical addressing: The network layer adds a header to the packet coming from the upper layer, includes the logical address of the sender and receiver. • Routing: Network layer route or switch the packets to its final destination in an internetwork.

  5. 4. Transport Layer • Transport layer is responsible for process-to-process delivery of entire message. Functions of Transport Layer • Service-point addressing (Port addressing): Computer performs several operations simultaneously. • Segmentation and reassembly: Message is divided into segments. • Each segment contains a sequence number which enables transport layer to reassemble at destination. • Connection control: Transport layer performs connectionless and connection oriented services with the destination machine. • Flow control: Transport layer performed end to end flow control while data link layer performs it across the link. • Error control: Transport layer ensures error free transmission. (error means damage, loss or duplication)

  6. 5. Session Layer • The session layer is the network dialog controller. • It establishes, maintains, and synchronizes the interaction among communicating systems. Functions of Session layer • Dialog Control: The session layer is network dialog controller, ie, it establish and synchronizes the interaction between Communication system. • Synchronization: Session layer adds synchronization points into stream of data.

  7. 6. Presentation layer • The presentation layer deals with syntax and semantic of the information being exchanged between two systems. Functions of Presentation layer • Translation: Two systems are usually exchanging information in the form of character string, number and so on. • Different computer uses different encoding systems. • The presentation layer maintains interoperability between the two encoding systems.

  8. Encryption: To carry sensitive information, a system must be able to ensure privacy. • Encryption means to transforms the original information to another form. • Decryption is a reverse process. • Compression: Compression is a technique of reducing number of bits required to represent the data. • Data compression is important in transmission of multimedia such as text, audio and video. 7. Application Layer • It provides user interface and other supporting services such as e-mail, remote file access, file transfer and sharing databases.

  9. Responsibility of Application Layer • Network virtual terminal: It is a software version of physical terminal that allows a user to log onto a remote host. • File Transfer, Access and Management (FTAM): FTAM allows user to access files in remote hosts, to retrieve files and to manage files in remote computer. • Mail Services: E-mail forwarding, storage are the services under this category. • Remote log-in: A user canlog into a remote computer and access the resources of that computer. • Directory services: This services include access for distributed database and global information.

  10. Services • The Hypertext Transfer Protocol (HTTP) is a vehicle for accessing the World Wide Web (WWW). • The Simple Mail Transfer Protocol (SMTP) is the main protocol used in electronic mail (e-mail) service. • The File Transfer Protocol (FTP) is used for transferring files from one host to another. • The Terminal Network (TELNET)and the Simple Network Management Protocol (SNMP) is used by an administrator to manage the Internet at global and local levels.

  11. TCP/IP PROTOCOL SUITE • The TCP/IP protocol suite is made of Five layers: Physical, Data link, Network, Transport, and Application. .

  12. TCP/IP PROTOCOL SUITE • The TCP/IP reference model is a set of protocols that allow communication across multiple networks. • It is a hierarchical protocol made up of interactive modules. • The term hierarchical means that each upper level protocol is supported by the services provided by one or more lower level protocols. • The original TCP/IP protocol suite was defined as four software layers built upon the hardware. • Today, however, TCP/IP is thought of as a five-layer model.

  13. Layers in the TCP/IP Protocol Suite • To better understand the duties of each layer, we need to think about the logical connections between layers. • Figure 2.6 shows logical connections in our simple internet.

  14. TCP/IP Protocol Suite

  15. The three top most layers in the OSI model, however, are represented in TCP/IP by a single layer called the Application layer (Session, Presentation and Application layer). • At the Transport layer, TCP/IP defines three protocols: Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Stream Control Transmission Protocol (SCTP). • At the Network layer, the main protocol defined by TCP/IP is the Internetworking Protocol (IP). • Internet layer also called Network layer. • Host to network layer is also called Physical and Data link layer.

  16. Encapsulation and De-capsulation • One of the important concepts in protocol layering in the Internet is encapsulation / de-capsulation.

  17. Encapsulation at the Source Host At the source, we have only encapsulation. • 1. At the application layer, the data to be exchanged is referred to as a message. • The message is passed to the transport layer. • 2. The result is the transport-layer packet, which is called the segment(in TCP) and the user datagram(in UDP). • The transport layer then passes the packet to the network layer. • 3. The network layer takes the transport-layer packet as data and adds its own header contains the addresses of the source and destination hosts. • The packets are called a datagram passes the packet to the data-link layer. • 4. The data-link layer takes the network-layer packet as data and adds its own header, which contains the link-layer addresses of the host or the next hop (the router). • The result is the link-layer packet, which is called a framepassed to the physical layer for transmission.

  18. De-capsulation and Encapsulation at the Router At the router, both de-capsulation and encapsulation because the router is connected to two or more links. • 1. After the set of bits are delivered to the data-link layer, this layer de-capsulatesthe datagram from the frame and passes it to the network layer. • 2. The network layer only inspects the source and destination addresses in the datagram header and to find the next hop to which the datagram is to be delivered. • 3. The data-link layer of the next link encapsulates the datagram in a frame and passes it to the physical layer for transmission.

  19. Addressing • The figure shows, there is a relationship between the layer, the address used in that layer, and the packet name at that layer.

  20. Addresses in the TCP/IP protocol suite

  21. Four levels of addresses are used in an internet employing the TCP/IP protocols: Physical (link) addresses, Logical (IP) addresses, Port addresses, and Specific addresses.

  22. URL: Here FOUR parts http://172.16.17.20:8080/Result/IMCA http – Protocol 172.16.17.20– IP Address 8080– Service (http) /Result/IMCA– Path and Filename

  23. Addressing • Each address is related to a specific layer in the TCP/IP architecture. • At the transport layer, addresses are called Port numbers, and these define the application-layer programs at the source and destination. • Port numbers are local addresses that distinguish between several programs running at the same time. • At the network-layer, IP address the addresses are global, with the whole Internet as the scope. • A network-layer address uniquely defines the connection of a device to the Internet. • The link-layer addresses, sometimes called MAC addresses, are locally defined addresses, each of which defines a specific host or router in a network (LAN or WAN).

  24. Multiplexing (Many to One) and Demultiplexing(One to Many) • The TCP/IP protocol suite uses several protocols at some layers, we have multiplexing at the source and demultiplexing at the destination. • Multiplexing in this case means that a protocol at a layer can encapsulate a packet from several next-higher layer protocols (one at a time); • Demultiplexing means that a protocol can decapsulate and deliver a packet to several next-higher layer protocols (one at a time).

  25. Multiplexing (Many to One) and Demultiplexing (One to Many)

  26. THE OSI MODEL • Almost three-fourths of the countries in the world are represented in the ISO. • An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. • It was first introduced in the late 1970s. ISO is the organization; OSI is the model. • An open system is a set of protocols that allows any two different systems to communicate. • The purpose of the OSI model is to show how to facilitate communication between different systems.

  27. Summary of OSI Layers

  28. OSI versus TCP/IP • When we compare the two models, we find that two layers, session and presentation, are missing from the TCP/IP protocol suite. • The application layer in the suite is usually considered to be the combination of three layers in the OSI model. TCPI/P and OSI model

  29. Services • 21: File Transfer Protocol (FTP) • 22: Secure Shell (SSH) • 23: Telnet remote login service • 25: Simple Mail Transfer Protocol (SMTP) • 53: Domain Name System (DNS) service • 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web • 110: Post Office Protocol (POP3) • 119: Network News Transfer Protocol (NNTP) • 123: Network Time Protocol (NTP) • 143: Internet Message Access Protocol (IMAP) • 161: Simple Network Management Protocol (SNMP) • 194: Internet Relay Chat (IRC) • 443: HTTP Secure (HTTPS)

  30. ALL THE BEST

More Related