6. Network Model ENG224 INFORMATION TECHNOLOGY – Part I

Why Network Protocol Models? ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Why Network Protocol Models? Network communication is an extremely complex task Need cooperative efforts from all nodes involved A standard model helps to describe the task of a networking product or service Also help in troubleshooting by providing a frame of reference

Who define Network Model? ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Who define Network Model? Need non-profit making organizations ISO - International Standards Organization e.g. OSI, MPEG-1, 2, 4, etc. (http://www.iso.ch/) IEEE - Institute of Electrical & Electronic Engineers e.g IEEE 802, IEEE 754, etc. (http://www.ieee.org) ITU - International Telecommunication Union e.g. V.34, H.323, H.324, etc. (http://www.itu.int)

The OSI 7-layer Model OSI - Open Systems Interconnection ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model The OSI 7-layer Model OSI - Open Systems Interconnection Defined in 1984 and become an international standard All Away People Pizza Seem Sausage To Throw Need Not Data Do Processing Please

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Layered Architecture Layering specifies different level of functions and services Each layer works with the layer below and above it Each layer provides services to next layer Shield the upper layer from the details of actual implementation

Relationship of OSI layers ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Relationship of OSI layers Virtual Communication Physical Communication

Protocols in a layered architecture ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Protocols in a layered architecture Network communication is possible only if machines speaking the same languages (protocols) Since each layer work independently, each layer speaks different languages (protocols) Lead to the concept of a Protocol Stack Network communication is possible only if the Protocol Stacks on two machines are the same

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model To identify the language (protocol) of each layer, identifier (header and trailer) are added to data

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 1. Physical Layer Example protocols: Ethernet, Token Ring (Physical part) Appl. Appl. Define how cable is attached to the Network Adapter Card How many pins in the connector? The impedance? Max/min electrical voltage? Responsible for transmitting bits from one computer to another Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

2. Data Link Layer Example protocols: Ethernet, Token Ring ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 2. Data Link Layer Example protocols: Ethernet, Token Ring Appl. Appl. Make data frames Provide error-free frame transfer by acknowledgment and retransmission Pres. Pres. Sess. Sess. Tran. Tran. Frame Netw. Netw. Data. Data. Phys. Phys.

INFORMATION TECHNOLOGY – Part I ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model

3. Network Layer Example protocols: IP, IPX ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 3. Network Layer Example protocols: IP, IPX Logical address to physical address translation For TCP/IP running on Ethernet Logical address: IP address 158.132.148.99 Physical address: Ethernet address 00 00 E2 15 1A CA Determine the route from source to destination computer Appl. Appl. Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

INFORMATION TECHNOLOGY – Part I ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model

4. Transport Layer Example protocols: TCP, SPX, NWLink ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 4. Transport Layer Example protocols: TCP, SPX, NWLink Ensure packets are delivered error free, in sequence Translate between packets and message Appl. Appl. Pres. Pres. Sess. Sess. Tran. Tran. 1 2 3 Sending 1 3 2 Receiving Netw. Netw. Data. Data. Phys. Phys.

5. Session Layer Example application program: Winsock, UNIX Socket ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 5. Session Layer Example application program: Winsock, UNIX Socket Appl. Appl. Establishment, maintaining and release of session Provide dialog management Regulate which side transmit, when, for how long (Sync.) Provide synchronization between user tasks Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model What is a Session? A. Consecutive sessions on a transport layer connection B. Consecutive sessions on a multiple transport layer connections 1 2 3 1 2 3 C. Both 1 2 3

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 6. Presentation Layer Example application program: redirector (NT), SSL Appl. Appl. Translate data from Application Layer to the format suitable for session layer (the network) Provide data encryption, compression Changing or converting character set, graphic, and file format Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

7. Application Layer Example protocols: FTP, Telnet, HTTP ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 7. Application Layer Example protocols: FTP, Telnet, HTTP Entry point for application to access network Directly support user applications E.g. File transfer, email General capabilities: Network access, flow control, Error recovery Appl. Appl. Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

Example: File Transfer ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Example: File Transfer The most traditional network task Implemented by a simple Application Layer protocol called FTP FTP Client FTP Server PictureTel Network

Utility: WS_FTP ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Utility: WS_FTP

FTP FTP TCP TCP IP IP Ethernet Ethernet ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model PictureTel WS_FTP FTP FTP FTP Client FTP Server Layers 5-7 Layers 5-7 Layer 4 TCP TCP Layer 4 Layer 3 IP IP Layer 3 Ethernet Ethernet Layers 1,2 Layers 1,2

The 802 Project Model IEEE launched the Project 802 in 1980 February ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model The 802 Project Model IEEE launched the Project 802 in 1980 February Predate the ISO standard, but the development was performed in roughly the same time Objective: To clearly define the network standards for different kind of physical components of a network - the interface card and the cabling Enhance the Data Link and Physical layers of the OSI model

ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model IEEE 802 Categories 802.1 Internetworking 802.2 Logical Link Control (LLC) 802.3 Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) LAN (Ethernet) 802.4 Token Bus LAN 802.5 Token Ring LAN 802.6 Metropolitan Area Network (MAN) 802.7 Broadband Technical Advisory Group 802.8 Fiber-Optic Technical Advisory Group 802.9 Integrated Voice/Data Networks 802.10 Network Security 802.11 Wireless Networks 802.12 Demand Priority Access LAN, 100 BaseVG-AnyLAN

Enhancements to the OSI Model ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Enhancements to the OSI Model Divide the Data Link layer into 2 sub-layers Logical Link Control Sub-layer Define the use of service access points (SAPs) as an interface for higher layer to Data Link layer Media Access Control Sub-layer Directly interface with the network card For delivering error-free data communications

Logical Link Control (LLC) ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Logical Link Control (LLC) 802.1 802.2 Media Access Control (MAC) 802.3 802.4 802.5 802.12