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The TCP/IP Protocol.

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1 The TCP/IP Protocol

2 Introduction To TCP/IP
Transmission Control Protocol/Internet Protocol (TCP/IP) Most commonly used network protocol suite today Wide vendor support Open protocol Provides access to Internet services Windows Server 2003 Can use several protocols Many of its main features require the use of TCP/IP

3 Internet History : Early packet-switching principles 1961: Kleinrock - queueing theory shows ` effectiveness of packet-switching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972: ARPAnet demonstrated publicly, NCP (Network Control Protocol) first host-host protocol, first e mail program. ARPAnet has 15 nodes 1.8.1 3

4 Internet History 1970: ALOHAnet satellite network in Hawaii
: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn - architecture for interconnecting networks late70’s: proprietary architectures,DECnet, SNA, XNA 1979: ARPAnet has 200 nodes 1.8.2 4

5 Internet History Cerf and Kahn’s internetworking principles:
: Internetworking, new and proprietary nets Cerf and Kahn’s internetworking principles: minimalism, autonomy-no internal changes required to interconnect networks best effort service model stateless routers decentralized control define today’s Internet architecture 1.8.2 5

6 Internet History 1983: deployment of TCP/IP
: new protocols, a proliferation of networks 1983: deployment of TCP/IP 1982: SMTP protocol defined 1983: DNS defined for name-to-IP address translation 1985: FTP protocol defined 1988: TCP congestion control 1.8.3 6

7 Internet History US networks: Csnet, BITnet, NSFnet, Minitel
: new protocols, a proliferation of networks US networks: Csnet, BITnet, NSFnet, Minitel 100,000 hosts connected to confederation of networks 1.8.3 7

8 Internet History Early 1990’s: ARPAnet decommissioned
1990, 2000’s: commercialization, the Web, new apps Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, ) early 1990s: Web hypertext [Bush 1945, Nelson 1960’s] HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape late 1990’s: commercialization of the Web 1.8.4 8

9 Internet History Late 1990’s – 2000’s:
1990, 2000’s: commercialization, the Web, new apps Late 1990’s – 2000’s: more killer apps: instant messaging,peer-2-peer file sharing (e.g., Naptser) network security to forefront est. 50 million host, 100 million+ users backbone links running at Gbps now: Gbps (youtube, social networking) 1.8.4 9

10 The (capital “I”) Internet
The world-wide network of TCP/IP networks Different people or organisations own different parts Different parts use different technologies Interconnections between the parts Interconnections require agreements sale/purchase of service contracts “peering” agreements No central control or management

11 The principle of “Internetworking”
We have lots of little networks Many different owners/operators Many different types Ethernet, dedicated leased lines, dialup, optical, broadband, wireless, ... Each type has its own idea of low level addressing and protocols We want to connect them all together and provide a unified view of the whole lot (treat the collection of networks as a single large internetwork)‏

12 What’s the Internet millions of connected computing devices: hosts, end-systems PC’s workstations, servers PDA’s phones, communication links fiber, copper, radio, satellite routers: forward packets (chunks) of data through network local ISP company network regional ISP router workstation server mobile

13 TCP/IP Architecture Overview
The TCP/IP model can be broken down into four layers: Application Transport Internet Physical Network Interface Application layer provides access to network resources. It defines rules, commands, and procedures for client to talk to a service running on a server

14 TCP/IP Architecture Overview (continued)
Transport layer is responsible for preparing data ready to be transported across the network Internet layer is responsible for logical addressing and routing Physical Network Interface layer consists of the network card driver and the network card itself

15 TCP/IP Protocol

16 The TCP/IP Model SMTP HTTP FTP Telnet DNS Audio Video TCP UDP RTP IP
Application layer SMTP HTTP FTP Telnet DNS Audio Video TCP UDP RTP Transport layer IP Network layer Ethernet PPP ATM Optics ADSL Satellite 3G Physical and Data link layer

17 Layer Interaction: TCP/IP Model
Application Application TCP or UDP TCP or UDP IP IP IP IP Link Link Link Link Link Link Physical Physical Physical Router Host Host Router

18 Layer Interaction: The Application Layer
Applications behave as if they can talk to each other, but in reality the application at each side talks to the TCP or UDP service below it. Application Application The application layer doesn't care about what happens at the lower layers, provided the transport layer carries the application's data safely from end to end. TCP or UDP TCP or UDP IP IP IP IP Link Link Link Link Link Link Physical Physical Physical Router Host Host Router

19 Layer Interaction: The Transport Layer
The transport layer instances at the two ends act as if they are talking to each other, but in reality they are each talking to the IP layer below it. The transport layer doesn't care about what the application layer is doing above it. Application Application TCP or UDP TCP or UDP The transport layer doesn't care what happens in the IP layer or below, as long as the IP layer can move datagrams from one side to the other. IP IP IP IP Link Link Link Link Link Link Physical Physical Physical Router Host Host Router

20 Layer Interaction: The Network Layer (IP)
The IP layer has to know a lot about the topology of the network (which host is connected to which router, which routers are connected to each other), but it doesn't care about what happens at the upper layers. Application Application TCP or UDP TCP or UDP IP IP IP IP The IP layer works forwards messages hop by hop from one side to the other side. Link Link Link Link Link Link Physical Physical Physical Router Host Host Router

21 Layer Interaction: Link and Physical Layers
The link layer doesn't care what happens above it, but it is very closely tied to the physical layer below it. All links are independent of each other, and have no way of communicating with each other. Application Application TCP or UDP TCP or UDP IP IP IP IP Link Link Link Link Link Link Physical Physical Physical Router Host Host Router

22 A Flow of Application messages across TCP/IP layers
Messages (UDP) or Streams (TCP) Application Transport Internet UDP or TCP segment IP Packets Network-specific frames Message Layers Underlying network Physical Network interface

23 Encapsulation of a message transmitted via TCP over an Ethernet
Application message TCP header IP header Ethernet header Ethernet frame port TCP IP

24 Layering: physical communication
data application transport network link physical network link physical application transport network link physical data application transport network link physical application transport network link physical

25 Application Layer Protocols
There are many Application layer protocols, each of which is associated with a client application and service provided by a server (Client/Server Model) HTTP FTP TELNET SMTP POP3 IMAP4

26 Application Model

27 Application Layer Protocols
HTTP Hypertext Transfer Protocol (HTTP) is the most common protocol used on the Internet today HTTP defines the commands that Web browsers can send and how Web servers are capable of responding FTP File Transfer Protocol (FTP) is file-sharing protocol FTP is implemented in stand-alone FTP clients as well as in Web browsers It is safe to say that most FTP users today are using Web browsers

28 Application Layer Protocols
TELNET Telnet is a terminal emulation protocol that is primarily used to connect remotely to UNIX and Linux Systems The Telnet protocol specifies how a telnet server and telnet client communicate

29 Application Layer Protocols
SMTP Simple Mail Transfer Protocol (SMTP) is used to send and receive messages between servers that are communicating It is used by client software, such as Outlook Express, to send messages to the server SMTP is never used to retrieve from a server when you are reading it Other protocols control the reading of messages

30 Application Layer Protocols
POP3 Post Office Protocol version 3 (POP3) is the most common protocol used for reading messages This protocol has commands to download messages and delete messages from the mail server POP3 does not support sending messages POP3 supports only a single inbox and does not support multiple folders for storage on the server

31 Application Layer Protocols
IMAP4 Internet Message Access Protocol version 4 (IMAP4) is another common protocol used to read messages IMAP4 can download message headers only and allow you to choose which messages to download IMAP4 allows for multiple folders on the server side to store messages

32 Transport Layer Protocols
Transport layer protocols (TCP & UDP) are responsible for getting data ready to move across the network The most common task performed by Transport layer protocols is breaking entire messages down into segments suitable to form packets Transport layer protocols use port numbers When a segment is addressed to a particular port, the Transport layer protocol knows to which service to deliver the packet

33 TCP Transmission Control Protocol (TCP) is the most commonly used Transport layer protocol for most Internet services TCP is connection-oriented and reliable Connection-oriented means that TCP creates and verifies a connection with a remote host before sending information Verifies that the remote host exists and is willing to communicate before starting the conversation Provides flow control, segmentation, and error control

34 TCP Connection-oriented
Establishes a connection before transmitting data Three-way handshake SYN SYN/ACK ACK

35 Send more data, wait for ACK
TCP Error control & Flow control Require acknowledgements from receiver to ensure data was received correctly Checksum Unique character string allowing receiving node to determine if arriving data unit exactly matches data unit sent by source Ensures data integrity Send data, wait for ACK ACK Send more data, wait for ACK

36 TCP Segmentation Sequencing Reassembly
Breaking large data units received from Session layer into multiple smaller units called segments Increases data transmission efficiency MTU (maximum transmission unit): Largest data unit network will carry (Ethernet default: 1500 bytes) Sequencing Method of identifying segments belonging to the same group of subdivided data Reassembly Process of reconstructing segmented data units

37 Transport Layer (cont’d.)
Figure 2-2 Segmentation and reassembly

38 TCP Segment 1 2 3 4 5 6 7 8 9 10 11 User Data 1 Source ID or port 16 bits 2 Destination ID or port 16 bits 3 Sequence number 32 bits 4 ACK number 32 bits 5 Header length 4 bits 6 Unused 6 bits 7 Flags 6 bits 8 Flow control 16 bits 9 CRC bits 10 Urgent pointer 16 bits 11 Options 16 bits

39 UDP User Datagram Protocol (UDP) UDP is the appropriate if
Not as commonly used as TCP Used for different services Connectionless and unreliable UDP is the appropriate if Unconcerned about missing packets Want to implement reliability in a special way Streaming audio and video are in this category

40 UDP – Segment 1 2 3 4 User Data Source ID or port
Destination ID or port Length 4 Checksum

41 TCP versus UDP TCP is connection-oriented and reliable
Like registered mail UDP is connectionless and unreliable Like sending a message split on several postcards and assuming that the receiver will be able to put the message together

42 Internet Layer Protocols
Internet layer protocols are responsible for all tasks related to logical addressing An IP address is a logical address Any protocol that is aware of other networks exists at this layer Each Internet layer protocol is very specialized They include: IP, RIP and OSPF, ICMP, IGMP, and ARP

43 Internet Layer Protocols
IP Internet Protocol (IP) is responsible for the logical addressing of each packet created by the Transport layer to produce a complete IP Packet As each packet is built, IP adds the source and destination IP address to the IP packet ICMP Internet Control Messaging Protocol (ICMP) is used to send IP error and control messages between routers and hosts The most common use of ICMP is the ping utility

44 IP Packet version 4 1 2 3 4 5 6 7 8 9 10 11 IP4 12 13 14 1 Version number 4 bits 2 Header length 4 bits 3 Type of Service 8 bits 4 Total length 16 bits 5 Identifiers 16 bits 6 Flags 3 bits 7 Packet offset 13 bits 8 Hop limit 8 bits 9 Protocol 8 bits 10 CRC bits 11 Source address 32 bits 12 Destination Address 32 bits 13 Options varies 14 User data varies

45 Internet Layer Protocols
IGMP Internet Group Management Protocol (IGMP) is used for the management of multicast groups Hosts use IGMP to inform routers of their membership in multicast groups Routers use IGMP to announce that their networks have members in particular multicast groups The use of IGMP allows multicast packets to be distributed only to routers that have interested hosts connected

46 Internet Layer Protocols
ARP Address Resolution Protocol (ARP) is used to convert logical IP addresses to physical MAC addresses This is an essential part of the packet delivery process

47 Network Interface Layer Protocols
Most of the common Network Interface layer protocols are defined by the Institute of Electrical and Electronics Engineers (IEEE)

48 IP Addresses Internet Protocol (IP):
a protocol used in the internet layer. IP makes use of the existing networks to deliver information, where these networks may use a variety of protocols. Each computer has two addresses: hardware address: used by the underlying network protocol for deliver data frame; IP address: used by the internetworking protocols for deliver IP Packet. Hardware address is also known as physical address.

49 Types of addresses used on hosts
Address Example Software Example Address Application Layer Web browser Network Layer TCP/IP :80 Data Link Layer Ethernet 00-0C-00-F5-03-5A

50 IP Addresses IP Addressing Scheme
Each computer / router is assigned a unique IP address having 32 bits. Each IP address has two parts: The prefix (network ID or NetID) specifies the network to which the computer is attached. The suffix (HostID) specifies a particular computer on a network. Problem Given only 32 bits, how many bits should be allocated to the prefix and the suffix? around 4 billion addresses.

51 IP Addresses IP Addressing Scheme Considerations
If the prefix has many bits (large prefix, small suffix), there are many networks you can built but each network can only have a few computers. If the prefix has a few bits (small prefix, large suffix), there are only few networks you can built but each network can have many computers.

52 Subnet Masks A subnet mask defines which part of its IP address is the network ID and which part is the host ID Subnet masks are composed of four octets just like an IP address Wherever there is a 255 in the subnet mask, that octet is part of the network ID Wherever there is a 0 in the subnet mask, that octet is part of the host ID

53 Subnet Masks (continued)
A computer uses its subnet mask to determine Which network it is on Whether other computers are on the same network or a different network If two computers on the same network are communicating, then they can deliver packets directly to each other If two computers are on different networks, they must use a router to communicate

54 Subnet Masks (continued)

55 IP Address Classes The IP addressing scheme defines three primary classes (A,B,C), where each class has a distinct prefix/suffix size, and two reserved classes (D&E). The internet can accommodate large networks, medium networks, and small networks. Classes A, B, C are the primary classes. The IP addresses of computers and routers belong to these classes. Class D is used for multicasting. When a packet is sent to an IP multicast address, all the computers sharing this address will receive this packet. Class E addresses are considered experimental and are not used

56 The Classful Addressing Scheme

57 The first decimal value defines the class of the IP address as follows:

58 IP Address Classes & Default Subnet Masks

59 Each packet sent across the internet contains:
In each primary class, the number of networks and the number of computers per network are as follows: Each packet sent across the internet contains: the IP address of the source, and the IP address of the destination.

60 Dotted Decimal Notation
Commonly we use the dotted decimal notation to represent the 32-bit IP address. more convenient for human to manipulate Each octet (8-bit) is expressed as a decimal value, and adjacent decimal values are separated by a dot. Example:

61 Other special value of primary classes:
Loopback address 127.x.x.x intended for use in testing TCP/IP and for inter-process communication on the local computer Other special value of primary classes:

62 Assigning IP Addresses
Assigning Prefix Address Each network must have a unique prefix address throughout an internet. To connect a network to the global internet, an organization obtains a unique prefix address from the Internet Service Provider (ISP). In turn, the ISP coordinates with a central organization (the Internet Assigned Number Authority (IANA, on or before 1998); the Internet Corporation for Assigned Names and Numbers (ICANN, after 1998)) to ensure the uniqueness of the prefix. To connect a network to a private internet (Intranet), the organization can determine the prefix while ensuring its uniqueness.

63 Assigning IP Addresses
Assigning Suffix Address Each computer must have a unique suffix address in the same network; while two computers in two different networks can have identical suffix address or HostID. If the suffix is 00…0 or 11…1, the corresponding IP addresses have special meaning. Do not assign these suffixes. An IP address with suffix equal to 00…0 is used to refer to the network itself. An IP address with suffix equal to 11…1 is a directed broadcast address, i.e., it refers to all hosts on the network.

64 Firstly, assign a unique prefix to each network:
Example An organization wants to form a private TCP/IP internet with four networks, where one network is large (with many computers), two are medium, and one is small. Firstly, assign a unique prefix to each network: Assign a class A prefix for the large network (say, 10). Assign a class B prefix for each of the two medium networks (say, and ). Assign a class C prefix for the small network (say, ). Secondly, assign a unique suffix to each computer within each network:


66 Private IP Addresses You can use these addresses on any private LAN.
You CANNOT use them on the internet. Internet routers will block them.

67 Default Gateway Default gateway is another term for router
If a computer does not know how to deliver a packet, it gives the packet to the default gateway to deliver Routers can distinguish multiple networks and how to move packets between them Routers can also figure out the best path to use to move a packet between different networks

68 Classful IP Address A classful network had a “natural” or “implied” prefix length or netmask: Class A: prefix length /8 (netmask )‏ Class B: prefix length /16 (netmask )‏ Class C: prefix length /24 (netmask )‏ Modern (classless) routing systems have explicit prefix lengths or netmasks You can't just look at an IP address to tell what the prefix length or netmask should be. Protocols and configurations need explicit netmask or prefix length.

69 Classless addressing An ISP gets a large block of addresses
Internet routing and address management today is classless CIDR = Classless Inter-Domain Routing routing does not assume that class A, B, C implies prefix length /8, /16, /24 An ISP gets a large block of addresses e.g., a /16 prefix, or separate addresses

70 Classless addressing Allocate smaller blocks to customers
e.g., a /26 prefix (64 addresses) to 4 customers for their medium public networks, a /28 prefix (16 addresses) to 32 customers for their medium public networks, and a /29 prefix (8 addresses) to another 64 customers for their small public networks (and some space left over for other customers)

71 Binary presentation of Classless IP
/ (netmask )‏ / (netmask )‏ / (netmask )

72 Classless addressing exercise
Consider the address block /28 and /29. What are the IP addresses range can you obtain from each block? in prefix length notation netmasks in decimal IP address ranges What blocks are still available (not yet allocated)?

73 Sockets and Ports

74 Sockets and Ports Processes assigned unique port numbers
Process’s socket Port number plus host machine’s IP address Port numbers Simplify TCP/IP communications Ensures data transmitted correctly to the specific application among multiple applications running on same host Example Telnet port number: 23 IPv4 host address: Socket address: :23

75 Sockets and Ports (cont’d.)
Figure 4-12 A virtual connection for the Telnet service

76 Sockets and Ports (cont’d.)
Port number range: 0 to 65535 Three types Well Known Ports Range: 0 to 1023 Operating system or administrator use Registered Ports Range: 1024 to 49151 Network users, processes with no special privileges Dynamic and/or Private Ports Range: through 65535 No restrictions

77 Sockets and Ports (cont’d.)
Table 4-3 Commonly used TCP/IP port numbers

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