THÔNG TIN TÀI LIỆU
Packet Switching, Layer Models and Protocol Suites Outline Circuit vs packet switching Layered tasks Internet protocol suites ISO's OSI model End-to-End Communication Direct communication Most basic form of communication TX RX GND TX RX GND Serial Port Internet communication Communication is performed over the Internet Internet Internet Comm - App's Viewpoint Two network applications should interact as if they were directly connected write read App App A Internet B But what's going on underneath? What is inside the "cloud"? Circuit vs Packet Switching Dedicated circuits Circuit switching Telephone switches establish circuits for communication Packet switching Data are put into packets Each stamped with source and destination addresses Routers know where to forward packets telephone switch Packet Router Layered Tasks Computer networks are complex systems Tasks involve varieties of hardware and software components, and protocols Networking task is divided into several subtasks, or layers Real World Example Communication between managers of two companies Communicate What Actually Happens Communication takes place thru many layers Logical communication Secretary: types a letter Delivery boy: drops the letter Secretary: reads and reports the message Delivery boy: takes the letter Postal truck Post office: Processes and routes the letter Internet Layer Model The Internet Protocol Stack User Application Layer Software Transport Layer Network Layer Data Link Layer Physical Layer Hardware Transmission Medium 12 Application Layer Responsible Responsible for for providing providing services services to to the the user user The only layer to interact with user Data Application Layer SMTP HTTP Data Data Logical communication FTP H5 to Transport SMTP HTTP Data FTP H5 from Transport 13 Network Layer Data 1.1 5.7 1.1 1.1, 1.1,1.2, 1.2,6.1, 6.1,5.7, 5.7, are arelogical logical addresses addresses 1.2 Network R1 6.1 6.6 Network 6.3 R3 R2 Router 5.2 3.3 5.7 3.8 Network Network 18 Data Link Layer Responsible Responsible for for transmitting transmitting frames frames from from one one node node to to the the next next Duties/services Framing Physical addressing Flow control (hop-to-hop) Error control (hop-to-hop) Access control 19 Data Link Layer from Network to Network Data Data Link Layer T2 Data (frame) to Physical Data H2 T2 Data H2 from Physical 20 Data Link Layer A3, A3,3B, 3B,82, 82,9F, 9F, are arephysical physicaladdresses addresses Data 9F T2 Data 3B 9F 82 A3 A3 H2 21 Data Link Layer Data 1.15.7 1.1 97 1.2 32 Data 1.15.7 97 25 Network 25 R1 6.1 79 12 Network Data 1.15.7 79 62 6.6 6.3 62 R3 R2 5.2 54 88 3.3 3.8 Network Data 1.15.7 54 74 5.7 74 Network 22 Physical Layer Responsible Responsible for for transmitting transmitting individual individual bits bits from from one one node node to to the the next next Duties/services Physical characteristics of interfaces and media Representation of bits Data rate (transmission rate) Synchronization of bits 23 Physical Layer from Data Link Physical Layer to Data Link Data Data 01001011 (bits) 01001011 Transmission medium 24 The Big Picture L5 data H5 L4 data L3 data T2 L2 data H4 H3 H2 5 4 3 2 0111011010101001010101001 L5 data H5 L4 data L3 data T2 L2 data H4 H3 H2 0111010101010010101010101 Transmission medium 25 Internet Model sender Applicati on Transport Network Data Link Physical router router Network D.L D.L P.L P.L Transmission medium receiver Network D.L D.L P.L P.L Applicati on Transport Network Data Link Physical 26 Internet Model 27 Protocol Suites A set of protocols must be constructed to ensure that the resulting communication system is complete and efficient Each protocol should handle a part of communication not handled by other protocols How can we guarantee that protocols work well together? Instead of creating each protocol in 28 28 Internet Protocol Suite Layer Protocols Application HTTP, FTP, Telnet, SMTP, Transport TCP, UDP, SCTP, Network Data Link IP (IPv4), IPv6, ICMP, IGMP, Ethernet, Wi-Fi, PPP, Physical RS-232, DSL, 10Base-T, 29 OSI Model User 7.Application Layer 6.Presentation Layer 5.Session Layer 4.Transport Layer 3.Network Layer 2.Data Link Layer 1.Physical Layer Transmission Medium OSI – Open Systems Interconnection Developed by the International Standards Organizations (ISO) Two additional layers Presentation layer Session layer 30 Session Layer Responsible Responsible for for establishing, establishing, managing managing and and terminating terminating connections connections between between applications applications Duties/services Interaction management Simplex, half-duplex, full-duplex Session recovery 31 Presentation Layer Responsible Responsible for for handling handling differences differences in in data data representation representationto to applications applications Duties/services Data translation Encryption Decryption Compression 32
Ngày đăng: 29/03/2021, 10:34
Xem thêm: