Computer Networking Chapter 2. The Model
1. Overview 1.1. Concepts 1.2. Advantages and Disadvantages 2. Layers 2.1. Application Layer 2.2. Presentation Layer 2.3. Session Layer 2.4. Transport Layer 2.5. Network Layer 2.6. Datalink Layer 2.7. Physical Layer 3. Data flow in
Open Systems Interconnections The partitions a communication system into abstraction layers networking. The contains seven layers that define functions data communications protocols. Each layer represents a function performed when data is transferred between cooperating applications across an intervening network. Overview Model
The is a product international organization for standardization (ISO). Published in 1984 by both ISO, as standard ISO 7498, and renamed CCIT as a standard X.200 ITU-T has two major components, a seven-layer and a set specific protocols. Overview Model
A conceptual that characterizes and standardizes communication functions a telecommunication and computing system. Its goal is interoperability diverse communication systems with standard protocols. A layer does not define a single protocol. It defines a data communications function that may be performed by any number protocols, each providing a service suitable to function that layer. Overview Model
Every protocol communicates with its peers. A peer is an implementation same protocol in equivalent layer on a remote system, i.e., local ftp is peer a remote ftp. Peer-level communications must be standardized to successful communications to take place. In abstract, each protocol is concerned only with communicating to its peers. A layer serves layer above it and is served by layer below it. Layers
Application layer Presentation layer Session layer Transport Layer Network Layer Datalink layer Physical layer Layers
Layers
Application layers (above layer) Application Presentation Layers Session Transport Layer Network Layer Data Link Physical Data Transport Layers (below layers)
Application Transport Layer Network Layer Data Link Physical supporting network applications encryption, Presentation compression, machinespecific conventions Session synchronization, checkpointing, recovery data exchange Ví dụ Telnet FTP ASCII EBCDIC JPEG Operating System/ Application Access Scheduling Layers
Ví dụ Transport Network Data Link Physical process-process data transfer routing destination data transfer between neighboring network elements bits on wire TCP UDP SPX IP IPX 802.3 / 802.2 HDLC EIA/TIA-232 V.35 Layers Data Flow Layers
As data flows within in network, each layer appends appropriate heading information to frames information flowing within network while removing heading information added by a lower layer. In this manner, layer n interacts with layer n-1 as data flows through an network. Data flow In
Data flow In
Data flow In
Upper Layer Data TCP HeaderUpper Layer Data Application Presentation Session Transport Đơn vị vận chuyển (PDU) Segment Data flow In IP Header Data Network Packet LLC Header Data FCS Data Link Frame MAC Header Data FCS 0101110101001000010 Physical Bits
Application Presentation Session Transport Network Data Link Physical Upper Layer Data Upper Layer Data TCP+ Upper Layer Data IP + TCP + Upper Layer Data LLC Hdr + IP + TCP + Upper Layer Data 0101110101001000010 Data flow In
Data flow In