1. Internet SecurityInternet Security Dr. ClincyLecture1 CS 4491 Internet Security Dr. Clincy Networking Fundamentals Note: I am still “tweaking” your syllabus in trying to get to 16 or 17 lectures with 50% online

2. Internet SecurityInternet Security Dr. ClincyLecture2 Internet – Consists of various technologies LAN Examples: Ethernet, Token Ring, Wireless and FDDI Ring Point-to-Point WAN Examples: Telephony Modem, DSL, Cable/Modem, T-Lines, and SONET Switched WAN Examples: X.25, Frame Relay and ATM Briefly explain the difference between packet switch networks and circuit switch networks

3. Internet SecurityInternet Security Dr. ClincyLecture3 Internet uses TCP/IP for internetworking – why ? Bottom Line: what makes TCP/IP so great and unique from other network protocols ??: –Network Technology Independence – independent of a particular vendor’s hardware –Universal Interconnection – any 2 computers connected to the internet can communicate – each computer has a unique internationally recognized address –End-to-End Acknowledgements – acknowledgements between the source and destination versus intermediate nodes –Application Protocol Standards – TCP/IP provides services (or software) to applications needing lower level communication services In understanding TCP/IP, one must understand OSI

4. Internet SecurityInternet Security Dr. ClincyLecture4 Why Study OSI? Still an excellent model for conceptualizing and understanding protocol architectures More granularity in functionality - more functional delineation Key points: –Modular –Hierarchical (chain of command, pecking order) –Boundaries between layers (called interfaces) NOTE: the protocols or functionality with in the layer could change however, the interface remains the same – this facilitates the flexibility

5. Internet SecurityInternet Security Dr. ClincyLecture5 OSI Open Systems Interconnection Developed by ISO (International Organization for Standardization) Contains seven layers Application Presentation Session Transport Network Data Link Physical

6. Internet SecurityInternet Security Dr. ClincyLecture6 AZ BCQT 7 1 3 1 Tx Rx Intermediate Nodes What happens at the End and Intermediate Nodes ?

7. Internet SecurityInternet Security Dr. ClincyLecture7 –between different layers on the same node or stack (INTERFACE) –between similar layers on different nodes or stacks (PEER-TO-PEER PROCESSES) Recap - OSI’s Layered Approach

8. Internet SecurityInternet Security Dr. ClincyLecture8 OSI Reference Model ? Bottom 3 layers Bottom 3 layers responsible for getting the info to the destination (Bottom 3 layers): at the lower levels of the model protocols define the electrical and physical standards (Bottom 3 layers) at the lower levels, the bit ordering, the transmission of the bits, and error detecting and correcting are defined Top 4 layers at the higher levels of the model, the protocols define the data formatting, message syntax, dialogue management, message sequences and info presentation

9. Internet SecurityInternet Security Dr. ClincyLecture9 OSI Physical Layer Responsible for transmission of bits Always implemented through hardware Encompasses mechanical, electrical, and functional interfaces Encoding issues: how 0’s and 1’s are converted to signals Transport medium: Coaxial, Twisted Pair, Optical, etc.. Transmission Rate/Data Rate – how fast to send bits Transmission mode: transmission direction (simplex, duplex) Physical Topology: network layout

10. Internet SecurityInternet Security Dr. ClincyLecture10 OSI Data Link Layer Responsible for error-free, reliable transmission of data Framing, Flow control, Error control (detection/correction) Makes use of physical address because with in the same network Network Layer Data Link Layer Physical Layer Actually sends the packets (groups of frames) from node to node using a routing algorithm Takes raw data (bits) and transform them into frames, error control, etc. Transmit and receive the raw data (bits)

11. Internet SecurityInternet Security Dr. ClincyLecture11 OSI Data Link Layer

12. Internet SecurityInternet Security Dr. ClincyLecture12 OSI Network Layer Responsible for routing of messages through networks Concerned with type of switching used (circuit v. packet) Handles routing among different networks (Routing across “internetworks”) NOTE: with in the same network, only the DATA LINK layer is needed – amongst multiple networks, the NETWORK LAYER and routing are needed Makes use of logical address vs physical address because not with in same network

13. Internet SecurityInternet Security Dr. ClincyLecture13 OSI Network Layer Transport Network Layer Data Link Layer Concerned with an error-free end-to-end flow of data Actually sends the packets (groups of frames) from node to node using a routing algorithm Takes raw data (bits) and transform them into frames

14. Internet SecurityInternet Security Dr. ClincyLecture14 OSI Network Layer

15. Internet SecurityInternet Security Dr. ClincyLecture15 OSI Upper Layers Application Presentation Session Transport Peer-to-Peer Processes ….. End-to-End nodes only

16. Internet SecurityInternet Security Dr. ClincyLecture16 OSI Transport Layer Isolates messages from lower and upper layers Breaks down message size (segmentation) (down) and performs re-assembly (up) Monitors quality of communications channel (oversee all hops) Selects most efficient communication service necessary for a given transmission (could change over hops) Flow and Error control for Source and Sink

17. Internet SecurityInternet Security Dr. ClincyLecture17 OSI Session Layer Establishes logical connections between systems (up/down) Manages log-ons, password exchange, log-offs (up/down) Terminates connection at end of session (up/down)

18. Internet SecurityInternet Security Dr. ClincyLecture18 OSI Session Layer

19. Internet SecurityInternet Security Dr. ClincyLecture19 OSI Presentation Layer Provides format and code conversion services Examples –File conversion from ASCII to EBDIC –Invoking character sequences to generate bold, italics, etc on a printer The source and sink could operate using different encoding schemes – the presentation layer makes the translations Security Compression

20. Internet SecurityInternet Security Dr. ClincyLecture20 OSI Application Layer Provides access to network for end-user (end-user being a human being or software application) User’s capabilities are determined by what items are available on this layer (ie. remote log-in, file transfer, email service, directory service, etc.)

21. Internet SecurityInternet Security Dr. ClincyLecture21 An exchange using the OSI model Explain encapsulation and decapsulation

22. Internet SecurityInternet Security Dr. ClincyLecture22 COMPLEXITY TO CONSIDER Any particular node in an internetwork can be functioning as follows simultaneously: Tx to other internetwork nodes Rx from other internetwork nodes Intermediate node to some other internetwork nodes

23. Internet SecurityInternet Security Dr. ClincyLecture23 How TCP/IP maps to OSI ??

24. Internet SecurityInternet Security Dr. ClincyLecture24 Physical addresses Physical address is also known as the link address Physical address can be different sizes (depend on the network) Unicast type physical addresses – single Rx Multicast type physical address – multiple Rxs Broadcast type physical address – all Rxs can pickup message

25. Internet SecurityInternet Security Dr. ClincyLecture25 IP Addresses can be either unicast, multicast or broadcast types Going from network A physical address 10 to network P physical address 95. Can’t use the physical address because different networks The network layer address contains the uniqueness we need from source to sink. Network layer address is A-P Unit at this layer - datagram Explain communications at the network layer

26. Internet SecurityInternet Security Dr. ClincyLecture26 Addresses in TCP/IP Application Specific Address Converts to a part address

27. Internet SecurityInternet Security Dr. ClincyLecture27 Port addresses Addresses of sending and receiving processes (j and k) Add IP address Overhead (H2, T2) added for what ?

28. Internet SecurityInternet Security Dr. ClincyLecture28 Relation- ship between Layers, Addresses, and Units in TCP/IP Signals Bits Frames Datagrams (Packets) Segments Messages