internet addresses. universal identifiers universal communication service - communication system...
TRANSCRIPT
Internet Addresses
Universal Identifiers
• Universal Communication Service - Communication system which allows any host to communicate with any other host– Name : what an object is– Address : where it is– Route : how to get there
IP Address
• Unique 32-bit address
IP Classes
IP Classes
Layers
TCP/IP vs OSI
OOpen SSystem IInterconnect
• The layers of the OSI model provide a framework for understanding networking.
• The OSI model is not a protocol, but rather a reference model (abstract structure) that describes the functions and interactions of various data communication protocols.
OSI Stack
• Layers 5 through 7, the "higher" layers, are concerned with communication between applications.
• Layers 1 through 4, the "lower" layers, are concerned with transmitting raw data between computers.
Physical Layer
• The Physical Layer deals with transmitting and receiving bits
across a physical medium. • Includes the following types of
hardware devices that send and receive signals over each type of physical medium:– Network interface cards
(NICs)
– Fiber optic transceivers
– Radio transceivers
– Modems
Physical Layer (cont.)
• Concerned only with transmitting and receiving physical signals that represent data bits.
• Demo
• Most error detection and all error correction are the responsibility of higher layers.
Data Link Layer
• The Data Link Layer deals with frames over a single physical link. A Data Link Layer address is the unique address built into a NIC.
• It uses the signaling services of the Physical Layer below it.
• To Layer 3 above, it provides the service of addressing a message to a device located across a single physical transmission path.
Data Link Layer (cont.)
• Network Layer handles data in units called "packets.“
• Network Layer passes a packet to the Data Link Layer, which encapsulates the packet by placing a header and trailer around it (frame).
• Frame header includes the unique NIC addresses of the sending and receiving nodes.
• Frame trailer contains error-checking information
Data Link Layer (cont.)
• Network Layer handles data in units called "packets.“
• Network Layer passes a packet to the Data Link Layer, which encapsulates the packet by placing a header and trailer around it (frame).
• Frame header includes the unique NIC addresses of the sending and receiving nodes.
• Frame trailer contains error-checking information
Data Link Layer (cont.)Transmitting Node
• Accepts data packets of arbitrary length from the Network Layer.
• Accepts the address of an adjacent node to which it is to transmit the data.
• Adds sequence information to the frame in case they get out of sequence during error recovery.
• Adds error detection and correction codes to the frames.
• Does not send frames to the Physical Layer at a faster rate than the receiving Data Link Layer process can handle them.
Data Link Layer (cont.)Receiving Node
• Receives bits passed up from the Physical Layer and interprets groups of bits as frames.
• Checks each frame for errors and takes corrective measures if necessary.
• Handles problems, such as missing frames, through handshaking with its peer process.
• Puts the frames back in the correct sequence to reconstruct the packet.
• Passes each decapsulated packet up to the Network Layer.
• Demo
Network Layer
• The Network Layer deals with packets.
• Responsible for transmitting data packets between source and destination nodes that may not be connected by the same physical link
• Message may pass through an "intermediate node." Network Layer's job is to use intermediate nodes to transmit a packet to its destination.
• Demo
Transport Layer
• The Transport Layer carries messages between processes (remember - multi-tasking).
• Transport Layer addresses are process addresses called "port numbers."
• The lowest layer in which peer software processes at either end of a connection carry on a conversation.
• Demo
Transport Layer (cont.)Services
• Addressing– deliver data to a specific process within a node.
• Connection management– responsible for establishing and releasing
connections between processes. – During data transfer, processes on both hosts
communicate to verify that data is being received without errors or loss.
– When communication is complete, the peer processes terminate the connection to free up resources for other processes.
• Flow Control and Buffering– responsible for ensuring that the receiving node
has enough memory buffers to store the incoming data
– data is not transmitted faster than the receiving node can accept it.
Session Layer
• Where a conversation starts and stops
• The rules of the conversation are agreed upon.
• Facilitates a step-by-step interaction or session between two entities.– Example - an interactive user session
begins with a user logging on to the computer and ends with the user logging off.
Session Layer (cont.)Electronic Conversation
• Parties first agree to talk to one another.
• They (usually) do not talk simultaneously.
• Divide the conversation into parts.
• End the conversation in an orderly fashion.
Presentation Layer
• The process concerned with how data is presented on the computer and represented inside the computer.
• The "representation" layer.– deals with the format of stored computer
information.
• Three main services:– Data representation
– Data security
– Data compression
Presentation Layer (cont.)Services
• Data Representation - resolves differences between different types of encoding systems.– Byte ordering within integers
– Character coding (EBCDIC and ASCII)
– Format of floating point numbers
– Boolean
• Data Security - encrypts and decrypts data– Authentication
– data encryption
• Data Compression - reduces the number of bytes that must be transmitted by translating the data into a more efficient form that requires less storage.
Application Layer
• Includes some programs that interact directly with users, and some that provide services to user applications.
• USENET newsgroups
• File transfer and access
• Virtual terminals
• Web browsers and servers