Class #7

1. Class #7 Chapter 7 Data Networking Fundamentals

2. Data Networking Fundamentals Objectives In this class, you will learn to: • Discuss basic networking concepts, including the elements common to all client-server networks • Provide examples of multiple network services • Describe the differences between LANs, MANs, and WANs • Understand the functions of each layer of the OSI model • Describe the purpose of protocols and list several types of protocols • Recognize the core protocols and addressing scheme for the TCP/IP suite

3. Data Networking Fundamentals Basic Terminology • Standalone workstation - a workstation that is not connected to a network, but relies on its own hard disk for data storage and applications. • Client - a workstation connected to a network. A person whose workstation is part of a network may also be called a client, or that person may be known more informally as a user. • Servers - store shared data and programs on their hard disks. They can also perform management functions, such as determining which users have access to certain programs. • Client-server network - a network that uses a server to enable clients to share data, data storage space, and devices.

4. Data Networking Fundamentals Basic Terminology, cont.

5. Requirements for Connectivity • The three requirements for connecting a workstation or server to a network are: • Transmission media – copper, fiber, wireless, etc., that is used to carry data • A transceiver – a device that combines the functions of both a transmitter/encoder and a receiver/decoder. The most common forms (today) of transceiver are the Network Interface Card (NIC) and the modem. • A connector or plug – the interface between the media and the NIC

6. Requirements for Data Communications • Nodes - any device (for example, a server, client, or printer) that can receive a transmission over a network. To receive data, each node must have a unique address, or identifying number. There are 2 types of nodes/hosts: • Server - A computer on the network that has or manages shared resources. • Client – A computer on the network that uses resources shared/managed by a server

7. Requirements for Data Communications, cont. • Protocol - a rule that governs how the parts of a network communicate. • Addressing – each device on a network must be somehow identified so that data can be accurately and reliably sent to it • Redundancy - the practice of using more than one component to guard against outages (or failures). • Network operating system (NOS) – server software that can manage not only data, but also users, groups, security, and applications on the network. • Client Software - software on the client node that can works with the NOS in coordinating a client’s/user’s rights to certain network resources through log-in authentication

8. How Networks are Used • The main purpose for using networks is to share limited numbers of programs, data, and devices, such as printers or fax machines, all of which are known as resources. • Network services can be categorized as follows: • File services – centralized control/storage of shared file resources. This can happen through: • A centralized file server • Local peer servers • Print services – centralized control of shared printers, usually through a central print server • Communication services – Allows remote access to the network through a modem pool, remote access server, or some other remote connectivity device

9. How Networks are Used, cont. • Network services can be categorized as follows (cont): • Mail services – coordinates the storage and transfer of e-mail between users on and off the network through a series of mail servers • Internet services – servers that provide these services are responsible for handling the myriad of different protocols and services available on the Internet, including WWW browsing and file transfer • Management services – network management servers centrally administer and simplify complicated administrative tasks on large or far-flung networks.

10. LANS, MANS, and WANS • One way of classifying networks is according to their geographical boundaries:

11. LANS, MANS, and WANS • Wide area network (WAN) - a network that connects two or more geographically distinct locations. • They are typically connected by fiber or long-range telco-grade copper

12. LANS, MANS, and WANS • Metropolitan area network (MAN) - a network that connects clients and servers in multiple buildings in a campus or small geographical area.

13. LANS, MANS, and WANS, cont. • Local area network (LAN) - a network of computers and other devices that is confined to a relatively small space, such as one building or even one office. • Connectivity device – The key to making a LAN work is this device. When of a network need to communicate with each other, this device is used to exchange data between them. • Hub – a common, very simple connectivity device that broadcasts an incoming digital signal to all its connected devices. • Switches, routers, and bridges are also connectivity devices with specific duties on a network. Their functions will be discussed in a later chapter.

14. LANS, MANS, and WANS

15. LANS, MANS, and WANS

16. The Internet • The Internet is a unique WAN not only because of its size, but also because of its diversity. • It may transmit confidential information between two offices within the same organization, or it may transmit public records to anyone who requests them. • To connect users from around the globe, the Internet relies on a hierarchical structure of connection points, just as the PSTN relies on a hierarchy of central offices. • An Internet Service Provider (ISP) is a company that operates a network and provides consumers with a link to the Internet. Local ISPs are the data version of a class-5 CO. • Higher-grade ISPs and Network Service Providers (NSPs) form the middle layers (aka tandem stations) • At the top of the hierarchy is the Network Access Point (NAP). NAPs form the backbone of the Internet, and are interconnected by peering points. • The two biggest NAPs in the US are known as the Metropolitan Area Exchanges – MAE East in Herndon VA and MAE West in San Jose CA.

17. The Internet, cont.

18. The Internet, cont.

19. The OSI Model • In the early 1980’s, just as the Internet began to be used at a wide level, several global, national, and governmental organizations began to cooperate to set standards in the data communications industry. • The coalition’s goal was to create and enable an easy to use, universal set of standards to enable a wide variety of communications equipment and software to intercommunicate and work together without obstacles. • Instead, they came up with the Open Systems Interconnection (OSI) Model.

20. The OSI Model, cont. Please Do Not Throw Sausage Pizza Away

21. Layer 1: Physical Layer • Protocols at this layer carry, generate, and/or detect voltage (or in the case of fiber optic transmission, pulses of light) so as to transmit and receive signals carrying data. • Examples of Physical Layer objects include transceivers, CAT5, and fiber-optic cable. • The Physical layer sets the data transmission rate and monitors data error rates, though it does not provide error correction services. • Physical network problems, such as a severed wire, affect the Physical layer.

22. Layer 2: Data Link Layer • The Data Link Layer controls communications between the Network layer and the Physical layer. • Objects that handle Data Link layer duties include portions of the Network Interface Card (NIC). • The primary function is to break data into distinct packages for transmission.

23. Layer 2: Data Link Layer, cont. • Frame or Packet - a structured package for moving data that includes not only the raw data, or "payload," but also the sender’s and receiver’s network addresses, and error checking and control information.

24. Layer 2: Data Link Layer, cont. • In reality (not part of the specification), the Data Link Layer is broken up into 2 sub-layers: • Media Access Control (MAC) – each device on a network is designated by a MAC address. • The format of a MAC is aa:bb:cc:xx:yy:zz, where a, b and c are the manufacturer’s codes, and x, y, and z are unique device codes.

25. Layer 2: Data Link Layer, cont. • In reality (not part of the specification), the Data Link Layer is broken up into 2 sub-layers: • Logical Link Control (LLC) – This sub-layer provides a common interface and supplies reliability and flow control services.

26. Layer 2: Data Link Layer, cont. • The Data Link Layer also provides 2 forms of basic forms of error control: • Via a Parity Check: In an 8-bit packet (for example), 7 bits are used for data, and 1 bit is used to confirm whether the sum of the data bits is even or odd: Using an even parity system 0 1 1 0 0 1 1 1 Valid packet 0 0 1 0 0 1 1 1 Invalid Packet 0 0 1 0 0 1 1 0 Valid Packet Using an odd parity system 0 1 1 0 0 1 1 0 Valid Packet 0 0 1 0 0 1 1 1 Valid Packet 0 0 1 0 0 1 1 0 Invalid Packet • Via a Cyclic Redundancy Check (CRC): A CRC takes the values of all the preceding fields in the frame and generates a unique 4-byte number called the Frame Check Sequence (FCS). The FCS is sent with the data in the frame/packet. When the packet arrives, the FCS is recalculated and compared with the original. It is essentially a multi-dimensional form of the basic parity check that can be used for error correction as well as detection.

27. Layer 3: Network Layer • Translates MAC addresses into their network protocol counterparts, and decides how to route data from the sender to the receiver. • Network layer addresses, which reside at the Network layer of the OSI model, follow a hierarchical addressing scheme and can be assigned through operating system software. IP addresses are a form of NLA, also called logical addresses or virtual addresses. • Devices that handle Network Layer services include routers and switches.

28. Layer 4: Transport Layer • Primarily responsible for ensuring that data is reliably transferred from point A to point B reliably, in the correct sequence, and without errors. • Transport protocols also handle flow control, or the method of gauging the appropriate rate of transmission based on how fast the recipient can accept data. • Ready to Send – A package indicating that a sender is waiting to send data to a receiver • Acknowledgement – confirmation that the package arrived and was understood • Retransmit/Retry -- a package did not arrive as expected, and a request for a resend is being made • In addition, this layer breaks up packets that are bigger than the maximum size the network usually handles (about 1500 bytes). This Segmentation is the process of decreasing the size of the data units when moving data from a network segment that can handle larger data units to a network segment that can handle only smaller data units. • The Transport Layer also handles sequencing and reassembly of the multiple packets that come in to a receiver.

29. Layer 5: Session Layer • Session - a connection for data exchange between two parties. • The Session layer’s functions include: • Establishing and keeping alive the communications link for the duration of the session • Duplex management • Identification and authorization of participants • Synchronizing the dialog between the two nodes • Determining whether communications have been cut off, and, if so, figuring out where to restart transmission

30. Layer 6: Presentation Layer • Serves as a translator between the application and the network. • At the Presentation layer, data becomes formatted in a schema that the network can understand; this format varies with the type of network used. • ASCII and EBCDIC are examples of Layer 6 protocols • Also at this layer is Encryption - the use of a mathematical routine to scramble data so that it can only be read by reversing the formula. Examples of this are ROT13 and Z-to-A transposition

31. Layer 7: Application Layer • Provides interfaces to the software that enable programs to use network services. • This DOES NOT refer to a software package or user interface. Instead, it refers to services like file transfer, management interfaces, etc. • This layer is used through an Application program interface (API) - a routine (a set of instructions) that allows a program to interact with the operating system.

32. Summary of the OSI Model

33. Applying the OSI Model

34. Applying the OSI Model, cont. Please read the process description on pages 311-312 for the detailed data flow of this diagram

35. TCP/IP Compared to the OSI Model • As I explained earlier, the OSI model doesn’t always match up with reality. One example is how Transmission Control Protocol/Internet Protocol works. • TCP/IP was developed in the 1960s as part for the DOD Advanced Research Projects Agency network – the forerunner of the modern Internet. Its primary benefits are low cost and the flexible ability to work with a multitude of platforms. It is now the de-facto routable communications standard. • TCP/IP is a suite of protocols including TCP, IP, UDP, ARP, ICMP, etc. • The TCP/IP model includes the following: • Application layer - provides authentication and compression services, and is roughly equivalent to the Application, Presentation, and Session layers of the OSI model. This includes FTP, HTTP, DHCP, and SMTP. • Transport layer - roughly corresponds to the Transport layer of the OSI model, handling flow control, error checking, and sequencing. This includes TCP and UDP • Network layer - equivalent to the Network layer of the OSI model, handling routing and host resolution. This includes IP, ICMP, and ARP. • Link layer - roughly equivalent to the Data Link and Physical layers of the OSI model, handling data formatting and physical transmission.

36. TCP/IP Compared to the OSI Model, cont.

37. The Internet Protocol (IP) • IPv4 belongs to the Network layer of the OSI model and to the Internet layer of the TCP/IP model. It provides information about how and where data should be delivered. • Datagram - the IP portion of a data frame, acts as an envelope for data and contains information necessary for routers to transfer data between subnets. • IP is an unreliable, connectionless protocol, which means that it does not guarantee delivery of data. Reliability is a function of higher-level protocols. If IP were the only protocol used, packets would be sent indiscriminately.

38. The Transmission Control and User Datagram Protocols (TCP and UDP) • TCP: • Belongs to the Transport layer of the connection models. It provides reliable data delivery services and is considered a connection-oriented sub-protocol. • Flow control and error correction are provided at the TCP level. • TCP compensates for IP’s lack of reliability. • UDP: • Also belongs at the Transport Layer, but is also a connectionless sub protocol. It is designed for situations where data must be transmitted quickly (streaming audio and video feeds, for example where lost packets can be compensated for) and with less overhead than TCP.

39. The TCP/IP Application Layer Protocols • Dynamic Host Configuration Protocol (DHCP) - an automated means of assigning a unique Network layer (or IP) address to every device on a network. • File Transfer Protocol (FTP) - an Application layer protocol used to send and receive files between hosts. • Hypertext Transfer Protocol (HTTP) - the Application layer protocol that enables Web browsers to issue requests to Web servers and interpret the response.

40. The TCP/IP Application Layer Protocols, cont. • Simple Mail Transfer Protocol (SMTP) - the protocol responsible for moving messages from one mail server to another over the Internet and other TCP/IP-based networks. • Telnet - a terminal emulation protocol used to log on to remote hosts using the TCP/IP protocol suite.

41. Addressing in TCP/IP CLASS 1st Byte Format Number Number of Purpose of networks hosts per network A 1-126 N.H.H.H 126 16777214 Major Networks (ATT) B 128-191 N.N.H.H >16000 65534 Large Sites C 192-223 N.H.H.H >200000 254 Most ISPs D 224-239 - - - Multicast E 240-254 - - - Experimental Reserved Addresses: x.x.x.0 – the 1st host on a network, which identifies the network’s default route x.x.x.255 – the last host on a network, which identifies the broadcast address 127.0.0.1 – a network’s/node’s loopback address (for internal testing) the 1st and last address in a subnetwork (a subset of a larger network, divided for efficiency, set by a subnet mask) Non-publicly routable addresses (ARPA RFC #1918): A 10.0.0.0 – 10.255.255.255: 1 network of 16 million hosts B 172.16.0.0 – 172.31.255.255: 16 networks of 65534 hosts each C 192.168.0.0 – 192.168.255.255: 255 networks of 255 hosts each

42. Summary • Workstations on a network typically share data, programs, and devices through a central computer called a server. • A network that uses a server to enable clients to share data, data storage space, and devices, is known as a client-server network. • The main purpose for using networks is to share programs, data, and devices, such as printers or fax machines. • The Open Systems Interconnection model was developed for computer-to-computer communications. “P.D.N.T.S.P.A” • TCP/IP is the suite of protocols used on today’s Internet. • IP addresses are broken up into classes, and some have reserved duties.

43. Assignments • Review Questions 1-25 • Hands-On Projects 7-1(all), 7-3 (1-4), 7-4 (all)

44. End of Class Quiz • What functions as a transceiver for a computer workstation or server? • Give an example of a Network Operating System. • What kind of specialized server would be responsible for storing spreadsheets used by several clients on a network? • What kind of specialized server would be responsible for accepting connections from remote users dialing in? • What organization would typically supply a business with a group of IPs for its networked devices?