OS Services And Networking Support

1. OS Services And Networking Support Juan Wang Qi Pan Department of Computer Science Southeastern University August 1999

2. OS Services and Evolution • Typical OS Services Facilities for program creation Program execution Controlled access to I/O and files System access Error detection and response Accounting • OS evolves and expands to offer new services • In response to hardware upgrading and new types of hardware • in response to user demand • in response to the needs of system management

3. Why OS Services for Networking Support ? • Computer networks have revolutionize our use of computer. Almost Most computers are networking. • Network software is no longer regarded as an add-on for few users, but considered as essential as a text editor. • Many computer manufacturers package networking software as part of the basic OS. • In an information age, computer networks are becoming an integral part in the dissemination of information.

4. Networking Support Services • Management of network devices Network card, Modem • Access to files through networks File servers, Web pages • Access to network I/O devices Network printer, network scanner, network photocopier • Client/Server computing • Distributed process management • Network security

5. How Is Networking Support Provided by an OS? • Networking services has been supported by the evolution of distributed capabilities in the OS and support utilities. • Communications architecture provides support for a network of independent computers and distributed applications.

6. Protocol Architectures • A protocol architecture defines a set of layers and protocols. • A protocol architecture should provide a high degree of cooperation between two communicating systems • Protocol architectures • TCP/IP protocol architecture • OSI protocol architecture

7. TCP/IP Protocol Architecture Five independent layers: • Application Layer • Transport Layer • Network Layer • Data Link Layer • Physical Layer

8. TCP/IP Protocol Architecture • Physical layer • Defines the media, and physical aspects of the signals • Defines clocking and synchronization operations • Defines physical connectors • Data Link Layer • Supports the transfer of traffic over one link • May perform error detection and retransmission

9. TCP/IP Protocol Architecture • Network Layer • Performs IP packet forwarding and route discovery • Transport Layer • Supports end-to-end acknowledge of traffic • provides logic for assuring the reliability of data exchanged between hosts • Application Layer • Contains protocols for specific user applications • Contains end-user applications

10. Protocol Data Units in the TCP/IP Architecture Application Byte Stream User data TCP Segment TCP Header IP Datagram IP Header Network-Level Packet Network Header

11. OSI Protocol Architecture • Open Systems Interconnection • Developed by the International Organization for Standardization (ISO) • Consists of seven layers • Protocols are developed to perform the functions at each layer

12. OSI Layers Application Presentation Session Transport Network Data Link Physical

13. What’s a Network Protocol • A network protocol defines an agreement between the communicating parties on how communication is to proceed. • Peer entities should communicate based on network protocols known by each other.

14. Key Features of a Protocol • Syntax Concerns the format of the transferred data blocks. • Semantics Includes control information for coordination and error handling. • Timing Includes speed and sequencing.

15. Examples of Network Protocols • Application Layer FTP, SMTP, DNS • Transport Layer TCP, UDP • Network Layer IP, ICMP • Link Layer HDLC, PPP, Frame Relay • Physical Layer ISDN, ATM

16. Network and Internet • Network system for connecting computer using a single transmission technology • Internet set of networks connected by routers that are configured to pass traffic among any computers attached to networks in the set

17. Basic Elements of the Internet • Host The internet is an association of thousands user computers that communicate with each other through networks. A user computer is called a host. • Router (Gateway ) A router or gateway is a network device which performs the relaying functions between networks. It must decide next gateway to forward a datagram to.

18. A Simple Network • Individual computers are first connected to a LAN (Ethernet or Token Ring). One router device provides the TCP/IP connection between the LAN and the rest of the world.

19. Basic Networking Information for a Host • IP Address The IP address assigned to this host Example: 129.2.25.102 • Subnet Mask The part of the IP address that distinguishes the network to which this host connects. Example: 255.255.255.0 • Default Router The IP address of the router that connects this host to the rest of the world. Example: 129.2.25.1

20. IP Address, Mask and Routers

21. Network Management • Network manager or administrator is responsible for monitoring and controlling network hardware and software • Network management is a hard problem Internet is heterogeneous and large. • TCP/IP includes SNMP as network management protocol

22. Network Configuration • Protocol software requires configuration parameters. • Small, heterogeneous networks can use decentralized configuration. • IP uses server-based configuration BOOTP: Bootstrap protocol DHCP: Dynamic Host Configuration Protocol

23. Network security • Security is a problem because Internet is not owned by one entity • Organizations can use firewalls to prevent unauthorized access • Encryption and digital signatures can provide confidentiality and secure identification

24. Client/Server Computing • Client/server computing is the key to realize the potential of information systems and networks. • Client machines are generally single-user PCs or workstations with a highly user-friendly interface. • Each server provides a set of shared user services to the clients • The server enables many clients to share access to the same database and enables the use of a high-performance computer system to manage the database

25. Client/Server Computing • Involves splitting an application into tasks and putting each task on the platform where it can be handled most efficiently • Processing for the presentation on the user’s machine • Data management and storage on a server • Involves a network

26. Generic Client/Server Environment

27. How Far Will It Go? • Increasingly, computers function not in isolation but as part of computer networks. • Networking support has been regarded as basic OS services. More and more networking services will be integrated into major OS. Internet-related technologies (like Internet Explorer) have been included in Microsoft Windows OS.