Network Theory – OSI and TCP/IP Models

1. Network Theory – OSI and TCP/IP Models

2. Internetworking:An Overview

3. What is Networking? • Networking - the interconnection of workstations, peripherals, terminals and other devices*

4. Yesterday’s Networks • The advent of the desktop PC brought with it small, closed networks in the mid-1980s. An old-school LAN (local-area network)

5. Today’s Computer Networks • Today, networks are everywhere: • School, work, home • Coffee shops, airports, state parks • Emerging technologies such as EV-DO and WiMAX promise metro-wide networks in the air.

6. What happened? • Over the past 20 years, computer networks have evolved: Small, proprietary, closed systems One huge, global, collection of networks (an internetwork) The Internet

7. What happened? • Vendors realized that standardizing their products would help them make money. • Various groups got together and proposed networking standards. • The Internet (b.1969) offered an attractive de facto set of standards.

8. Network Protocols and Standardization

9. Network Protocols • Early networks: • proprietary technologies • single vendor only • Today: • Standards-based technologies • Macs, PCs, cell phones, watches, toasters, and earrings can all share data as long as they all speak to each other according to the same set of rules, or protocol.

10. Network Protocols • Protocol - a set of rules, or an agreement, that determines the format and transmission of data. SNA (Systems Network Architecture) = IBM IPX (Internet Packet eXchange) = Novell IP (Internet Protocol) = US Department of Defense XNS (Xerox Network System) = Xerox NetBEUI (NetBIOS Extended User Interface) = IBM AppleTalk = Apple DECnet = Digital Equipment Corporation VINES = Banyan

11. TCP/IP: Internet Protocol • One protocol has become the de facto standard for all computer networks. • IP v4 = The Internet Protocol (version 4) • All hosts on the Internet use the IP protocol • The Internet actually uses a family, or suite, of protocols called TCP/IP which includes: • TCP, or Transmission Control Protocol: (adds reliability and sequencing to Internet conversations) • HTTP: (web stuff) • FTP: (file transfer) • DNS: (naming system that brought us .com and www) • SMTP: (mail, SPAM, and other delights of the Info Age)

12. TCP/IP: Internet Protocol TCP/IP’s developers never envisioned that this protocol could support a global network of entertainment and commerce. All of these devices need an IP Address to be on the Internet. All of these devices use the TCP/IP protocol “stack” to communicate. In this case, they are using HTTP to browse the web.

13. Reality Check • In the mid-1980s, Cisco (like all other vendors) focused on “multi-protocol” platforms. • Because TCP/IP has emerged as the dominant protocol, our focus is entirely on IP networks. • So, this is an Introduction to Cisco IP Network Devices

14. Types of Networks

15. LANs • Local-Area Networks (LANs) emerged in the mid 1980s • LANs • connects workstations, peripherals, and other devices in a single building • LANs made it possible to efficiently share such things as files and printers

16. Early LANs Isolated Seattle New York San Francisco

17. Wide Area Networks (WANs) Seattle New York San Francisco

18. LAN, CAN, MAN, and WAN • LAN - limited geographic area • office, home, small building (enterprise) • CAN - Campus-Area Network • University, Company Tech Center (enterprise) • MAN - Metropolitan-Area Network • citywide network, (typically involves a service provider) • WAN - large geographic area • city-to-city, worldwide, Internet (typical involves a service provider) • PAN – personal area network • Cell phone, watch, PDA, bluetooth stuff (you!)

19. Always “on” Intermittent, on-demand connectivity High bandwidth Low bandwidth Cheap Costly Typical Early LANs Typical Early WANs Small geographical area Large geographical area LAN vs WAN • Early LANs and WANs typically used very different: • Protocols • Devices • Signaling • Media (physical connections, wire, RF)

20. Early LAN vs WAN • Different network types, different devices: Common LAN Devices Common WAN Devices Modem, CSU/DSU Hub, Repeater Switch Bridge Access Server LAN Switch Router Router

21. Today’s LAN Devices Wireless (LAN/WAN) Today’s WAN Devices VPN Gateway Switch Bridge Access Point DSLAM Multilayer Switch IP Telephony (LAN/WAN) Optical Transport Firewall IP Phone IP PBX Router Router Early LAN vs WAN • Emerging technologies and dominance of TCP/IP spurred widespread adoption of new device types:

22. Today’s LAN/WAN • Several factors have blurred the distinctions between WANs and LANs and the devices that operate in each. • However, for the purposes of our discussions, we will talk about devices as either “LAN” or “WAN”

23. The OSI Reference Model

24. Enter ISO • ISO – International Organization for Standardization (Geneva) • Voluntary, non-treaty organization charted by the UN • From the earliest days of networking, it was clear to ISO that standards were needed. • Standardization aids: development, interoperability, education…

25. ISO’s OSI Model • ISO looked at existing network protocols (TCP/IP, XNS, SNA) and came up with OSI RM. • OSI RM - Open Systems Interconnection Reference Model

26. OSI Reference Model

27. 7 - Application Layer • Network processes to applications • Provides network services to user applications

28. 6 – Presentation Layer • Data Representation • Code Formatting • Negotiation of data transfer • Ensures information sent by the application can be transmitted on the network • Data encryption

29. 5 – Session Layer • Interhost communication • Establishes, maintains, and manages sessions between applications

30. 4 – Transport Layer • End-to-end connections • Segmentation • Reassembly into data stream • Offers potential of reliable transport

31. 3 – Network Layer • Addresses and best path • Logical addressing is used at this layer • IP, AppleTalk, IPX, etc. • Routers reside at this layer

32. 2 - Data-Link Layer • Access to media • Physical transmission across the medium • Error notification, network topology and flow control • Uses MAC (physical) addresses • Switches and bridges reside at this layer

33. 1 – Physical Layer • Binary Transmission • Provides the electrical, mechanical, procedural and functional means for activating and maintaining the physical link between systems. • The media resides at this layer

34. Data Encapsulation Example End System Intermediate Systems

35. Data Encapsulation

36. TCP/IP vs OSI Model

37. Cisco Networking

38. Brief(est) History of LANs

39. Early LANs • In the 1980s, several LAN technologies competed to offer Layer 1/Layer 2 services: • Token Ring (IBM) • Ethernet (Xerox, et al) • ARCnet (Datapoint) • Later on: • FDDI, Fiber Distributed Data Interface • ATM, Asynchronous Transfer Mode

40. The IEEE Working Groups 802.1 Networking Overview and Architecture 802.2 Logical Link Control Ethernet 802.3 802.4 Token Bus 802.5 Token Ring 802.6 MANs 802.7 Broadband 802.8 Fiber Optic 802.11 Wireless Ethernet ...and more!

41. Today • Ethernet is the de facto standard. • It has crushed its competitors in the LAN space, and has been adopted for Wireless networks and Metro WANs.

42. Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Ethernet and TCP/IP • Ethernet and TCP/IP are the most pervasive protocols TCP/IP Ethernet

43. Device Functions at Layers