What is TCP/IP

1. What is TCP/IP • Transmission Control Protocol / Internet Protocol • TCP and IP are two of the major network protocols of the TCP/IP • a large collection of networking protocols and services • often referred to as a protocol suite • the core communications protocol of the Internet Lecture Notes

2. Who Manages TCP/IP • Internet Society ISOC • Internet Architecture Board IAB • Internet Research Task Force IRTF • Internet Societal Task Force ISTF • Internet Corporation for Assigned Names and Numbers ICANN • Canadian Internet Registration Authority CIRA • Internet Engineering Task Force IETF • most important responsible for creating and managing RFCs Lecture Notes

3. OSI Network Reference Model • Developed by the ISO International Standards Association • 1978 ISO released a set of specifications that described: • network architecture for connecting dissimilar devices. • 1984, the ISO released a revision of this model and called it the • Open Systems Interconnection (OSI) reference model. • international standard • serves as a guide for networking. • vendors design network products based on the specifications • describes how network hardware and software work together in a layered fashion • an architecture that divides network communication into seven layers. Lecture Notes

4. OSI Important Concepts • Follows the basic Divide and Conquer approach to networking • break a big technical problem into a series of interconnected and interrelated problems and solve each one independently • Layers of Abstraction • allows different network functions to operate in abstraction or independent of each other • each network function has its own layer • each layer knows how to interface with the layers above and below it in the model • as long as adjacent layers follow the rules of interlayer communication they are free to carry out their own functions independently • Example TCP/IP will run on top of virtual any network hardware Ethernet, Token Ring, ATM, SONET, Frame Relay, etc. Lecture Notes

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

6. How Protocol Layers Behave • typically each layer handles packages of data referred to as Protocol Data Units(PDUs) • PDUs typically include envelope information in the form of • headers • trailers • each layer completes its task and formats itself for encapsulation or processing by the next layer Lecture Notes

7. H data T H Layer 7 T H Layer 6 T H Layer 5 T H Layer 4 T H Layer 3 T H Layer 2 T The Layers In Action Layer 7 Layer 6 Layer 5 Layer 4 Layer 3 Layer 2 Layer 1 Encapsulation Process Lecture Notes

8. The OSI View of TCP/IP • TCP/IP • is a software based set of networking protocols • TCP is Layer 4 Transport Services • IP is Layer 3 Network Services OSI Reference Model Transmission Control Protocol User Datagram Protocol Internet Protocol Lecture Notes

9. Institute for Electrical and Electronic EngineersIEEE 802 Standards • The working level standards hardware manufactures must follow to ensure their products will function seamlessly with other manufacturers products • 802.1 Internetworking • exchanging information from one physical network to another • 802.2 Logical Link Control • how two devices on the same physical network connect for communications • 802.2 Media Access Control • how network nodes are identified(physical address) and how they gain access to the network media • 802.3 CSMA/CD - Carrier Sense Multiple Access with Collision Detection • describes how Ethernet networking technologies operate • 802.5 Token Ring • describes how Token Ring networking technologies operate • The above represents only the main 802 standards Lecture Notes

10. Internet Layer Functions(Layer 3 - IP) The main IP layer responsibilities boil down to 3 functions: • MTU Fragmentation • Maximum Transmission Unit - the biggest chunk of data we can force into a datagram • Addressing Two layers • Network address- the LAN or physical network shared by all the computer connected to it • Host address - the address of the individual computers or nodes on the network • Routing • How do I get there form here or Can I get there at all Lecture Notes

11. Internet Layer Protocols Here are the Layer 3 protocols necessary for the proper functioning of TCP/IP • IP • ICMP • Ping • ARP and RARP • BootP or DHCP We will cover these in detail in later lectures Lecture Notes

12. Transport Layer Functions - Layer 4 • Sometimes referred to as HOSTS layer as its responsibility is to move data between hosts • performs the initial fragmentation of data files into datagram size pieces and reassembly at the receiving end • There are two distinct protocols: • User Datagram Protocol(UDP) • uses a Connectionless oriented process to transfer datagrams • Transmission Control Protocol(TCP) • uses Connection oriented process to transfer datagrams Lecture Notes

13. TCP/IP Application Layer - Layers 4,5,6 • Process Layer • here the protocol stack interfaces with applications and processes in other words - Users and their application programs • Examples of Application layer Programs/Services • FTP - File transfer protocol • Telnet - Terminal Emulator • NFS - Network File System • All these services use a Client/Server model • a server waits for and completes requests from a Client Lecture Notes

14. Service, Sockets and Ports Services A typical TCP/IP Server handles many request from multiple Clients or hosts at one time, all through a single connection to the network, that is a single network address. So how does it keep track of all these different requests and responses? Who ordered the FTP on Rye with No mayo? • Two elements are used : • Listener Processes, for instance a WEB server program, running on the server listen at specific port numbers • Port Addresses to identify which service is being requested • 0 - 1024 Well known services ports Web server for instance is port 80 • both TCP and UDP use port numbers to deliver datagrams Lecture Notes

15. Service, Sockets and Ports Sockets • the Socket addressis the unique combination of IP Address and Port Number Example WEB server running on a sever with an IP address of 142.222.12.53 142.222.12.53:80 • Port Addresses • 0 - 1024 Well known services ports Web server for instance is port 80 • 1025 - 65,535 ephemeral or unregistered ports • can be requested or assigned on a first free available basis by the TCP/IP stack • IANA regulates and registers ports www.iana.org • both TCP and UDP use port numbers Lecture Notes

16. Service, Sockets and Ports In Action Lecture Notes

17. Protocol Analyzer Elements • Promiscuous mode network interface card and driver • Packet filters • Trace Buffers • Decodes • Alarms • Statistics Lecture Notes

18. Physical Technologies The Physical layer deals with everything that is required to: • place 1’s and 0’s onto a connection medium Physical standards describe: • cables • connectors • electrical or optical components and levels • describes how the 0’s and 1’s will be represented and recognized

19. Header DATA Trailer Frames In order for our data to travel across our network it must be repackaged into: • Frames(packets) Each physical network technology has its own frame properties as described by: • Data Link layer Each frame has a header and trailer. The format of the header and trailer depend on the technology used Error Control Delivery Info

20. Lower Layer Functions

21. Network Technologies • LAN’s Local Area Networks • Stations share a physical medium - MAC • Wide area point-to-point lines • dedicated communication • Wide area Packet delivery services • switched or permanent virtual circuits • Cell switching services • switched or permanent virtual circuits • smaller packet sizes and different switch design

22. Network Technologies Mechanisms For each Technology we need • identify the destination • detect data errors • identify the protocol type for the Protocol Data Unit(PDU) carried within each frame especially in today's Multi-Protocol networks

23. Data Link Protocols • The Data Link layer performs several key jobs with the two most important being: • Managing access to whatever networking medium is in use, called Media Access Control (usually abbreviated as MAC) • Creating temporary point-to-point links between a pair of MAC layer addresses to enable data transfer, called Logical Link Control (usually abbreviated as LLC) • A point-to-point data transfer involves shipping data from a specific MAC layer address that represents the point of transmission to another specific MAC layer address that represents the point of reception on a single network segment, or TCP/IP subnet • PPP is a general-purpose, point-to-point protocol that overcomes SLIP’s deficiencies, and provides WAN data link encapsulation services similar to those available for LAN encapsulation

24. Client Appl Client Appl TCP TCP IP IP IP IP Data link physical Data link physical Data link physical Data link physical Repackaging Host B Host A Router Ethernet Frame Token Ring Frame

25. Internet PPP Protocol Point To Point Protocol • can be used on ANY full duplex circuit • synchronous - bit oriented • asynchronous - byte oriented(start/Stop • slow dial ups • fast leased lines • ISDN • SONET fiber optics • can carry PDU’s for many protocols • IP, IPX, DECnet, AND OTHERS

26. PPP PPP includes several subprotocols • Link Control Protocol • sets up • test • configures • closes link • Network Control Protocol • used to initialize, configure, and terminate a particular network protocol • each protocol has a separate Network Control Protocol

27. Typical PPP Session • Link Control Frame sent by Originating host PPP • starts the negotiation process in which additional Link Control Frames are sent to establish options • Network Control Protocol frames are sent to choose and configure network layer protocols(IP,IPX,etc) • Data is transmitted across the link in PPP • each frame includes a header with the PDU type • Network Control and Link Control Protocol frames are used to close the link

28. Additional PPP Features • Capable of using compression ie reducing the size of the header • Authentication • simple Password Authentication Protocol(PAP clear text) • Challenge Handshake Authentication Protocol (CHAP encrypted) • Automatic Link Quality monitoring

29. Layering For 802 Networks • Layer 2 further subdivided • Logical Link Control Sublayer • defines the format of the LLC header and rules for communicating • MAC sublayer • rules for accessing the meduim • defines the first part of the frame header which includes physical(MAC) source and destination addresses

30. Assigned Protocol Types (by Number)

31. IP IP Evolution to the IEEE 802 Standards RAW

32. 802.3 Defines CSMA/CD Carrier Sense Multiple Access withCollision Detection Basic Principles • All stations have access to the same media. • A frame broadcast by one workstation is heard by all. • Workstations contend for access and take steps when collisions occur.

33. Broadcasting and Multicasting Most transmissions on a network are UNICASTS, those that aredirected between two specific nodes Broadcasts • the destination address is set to all ones to indicate that all nodes on the network should accept the transmission • hex address is written as - X’FF-FF-FF-FF-FF-FF Multicasts • are typically sent to groups of nodes on the network(i.e.. All printers) • these nodes interfaces are program to accept these transmissions

34. Hardware Addresses in the IP Environment • IP addresses are used to identify individual IP hosts on a TCP/IP internetwork • TCP/IP networking uses ARP to determine the hardware address of the local target for the packet • IP hosts maintain an ARP cache—a table of hardware addresses learned through the ARP process—in memory • ARP is used only to find the hardware address of local IP hosts

35. ARP Broadcasts Identify the Source and the Desired IP Address

36. ARP Frame Structure

37. ARP Packet Fields and Functions • There are two basic ARP packets—the ARP request packet and the ARP reply packet • The most confusing part of ARP is the interpretation of the sender and target address information

38. Opcode Field • This field defines whether this ARP packet is a request or reply packet, and defines the type of address resolution taking place

39. ARP Cache • ARP information (hardware addresses and their associated IP addresses) is kept in an ARP cache in memory on most operating systems, including Linux, BSD, UNIX, Windows 95, Windows 98, Windows NT, and Windows 2000 • On a Windows 2000 system, ARP cache entries are kept in memory for 120 seconds

40. Summary IEEE Standards Model OSI Model

41. LAYER 3 The NETWORK LAYER Lecture Notes

42. IP Datagrams IP is a BEST EFFORT protocol IP’s Main Purpose • Provide interconnection of subnetworks to pass the data presented to it from upper layer protocols such as UDP or TCP protocols IP has four main functions • form datagrams • addressing • routing • fragmentation of datagrams Lecture Notes

43. Connectionless IP’s primary goal is to provide the basic algorithm for the transfer of data to and from a network • IP provides this by a connectionless delivery service • delivers data on a best effort basis • if data link layer fails to deliver a datagram IP does not inform anyone • datagrams may be delivered out of order • datagrams may be duplicated • IP does not care Lecture Notes

44. Network Layer Protocols • The primary function of Network layer protocols is to move datagrams through an internetwork connected by routers • Network layer communications are end-to-end communications that define the originator as the source Network layer address, and the target as the destination Network layer address • Internet Protocol is the Network layer protocol used in the TCP/IP suite • IP version 4 (IPv4) is widely implemented • Internet Protocol version 6 (IPv6) is undergoing some initial implementations Lecture Notes

45. Sending IP Datagrams • IP offers connectionless service with end-to-end Network layer addressing • Building an IP datagram packet to send on the wire has certain requirements • We must know the: • IP addresses of the source and destination • Hardware address of the source and next-hop router • Your system needs to resolve the name fred.com to an IP address • This is called the name resolution process Lecture Notes

46. Data Link Header Is Stripped Off and Reapplied by the IP Router as the Packet Is Forwarded Lecture Notes

47. Lifetime of an IP Datagram • All IP packets have a predefined lifetime indicated in each packet’s Time to Live (TTL) field • This ensures that packets cannot indefinitely circle a looped internetwork • The recommended starting TTL value is 64 • The default TTL in Windows 2000 is 128 • If a packet with TTL=1 arrives at a router, the router must discard the packet because it cannot decrement the TTL to zero and forward the packet Lecture Notes

48. Fragmentation and Reassembly • IP fragmentation enables a larger packet to be automatically fragmented by a router into smaller packets to cross a link that supports a smaller MTU, such as an ATM link • Once fragmented, no reassembly occurs until those fragments arrive at the destination, where they will be reassembled at the Transport layer • When the first fragment arrives at the destination, however, the destination host begins counting down from the TTL value of that packet Lecture Notes

49. Fragmentation • first the incoming datagram is checked for the don’t fragment flag • the data portion is then broken into into pieces that match the MTU(aligned to 8 byte boundaries) • the original header is added with the following additions: • length of the datagram( the new fragment size) • more flag set • fragmentation offset • new checksums Lecture Notes

50. Header Length Precedence Type of Service Length of Datagram Version Fragmentation Offset Identification Flags Header Checksum Time To Live Protocol Source IP Address Destination IP Address Options Strict Source Route, Loose Source Route, Record Route, Time Stamp, Security, Padding DATA(up to 65,535 bytes) IP Header Lecture Notes