1. Networking Protocols John R. Durrett ISQS 6343 #1

2. Introduction Protocol –set of rules –software –facilitate inter-computer communication OSI Seven Layer Model –model not reality –facilitate understanding –representative of different aspects of inter-networking –no direct correspondence with commercial implementations

3. The OSI Model 7 - Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 - Data Link 1 - Physical

4. Physical Layer Bits over media electrical signals computers, NIC, “wire”, etc. “black box” interface assumptions with upper layers

5. Data-Link Assumes physical layer frames - groups of bits ensures only delivery not accuracy Examples: –Token Ring –Ethernet IEEE model –LLC (logical link control) –MAC (Media Access Control)

6. Network Assumes data-link layer packets routing of packets –therefore addresses necessary network optimization congestion handling No error checking

7. Transport Relies on network layer Frequently combined with network layer in protocols Messages Error checking –UDP & TCP NetBEUI, TCP/IP, IPX/SPX

8. Session Assumes Transport layer Sessions between computers based on names of other computers NetBIOS - Windows Sockets - TCP/IP

9. Presentation Assumes session layer based on services provided –encryption, compression, translation

10. Application Assumes session exists RPC –procedural –distributed –locations required –relatively static pipes FTP protocol

11. Windows Networking Transport Device Interface (TDI) Network Device Interface Specification (NDIS) Allows support of multiple transport protocols interface between transport & session layers

12. NetBEUI Compact LAN based not routable ubiquitous limits size limits choice of clients/servers

13. TCP/IP UBIQUITIOUS performance & reliability based standards arrived before implementations IETF RFCs flexibility == difficult to manage IPs

14. Dotted quad –128.48.35.45 Classes –C, B, A –subnets Limits of current IPs –IPv6 or IPng Domain Names –reversed version of IPs –DNS

15. Protocol choice Clients –Windows NT –Windows 95… –DOS –OS/2 –Un*x –Macs Network Structure –Similar servers –LCD

16. Interoperability Hub - very simple relay Switch - virtual circuits Router - makes pathway choice based on IPs Bridge - passes data unchanged Gateway - translation Proxy Server - security