TOSHIBA FUNDAMENTALS

Transcription

1 ELECTRONIC IMAGING DIVISION NATIONAL SERVICE SCHOOL DIGITAL CONNECTED PRODUCTS TRAINING CLASS K NETWORK FUNDAMENTALS TOSHIBA America Business Solutions 2 Musick Irvine, California 92618

2 TABLE OF CONTENTS Preface... 3 Disclaimer... 4 I. INTRODUCTION...5 II. NETWORKING FUNDAMENTALS A REVIEW...6 A. Network Functionality... 6 B. Client/Server vs. Peer-to-Peer Networking C. Network Operating Systems D. Selecting the Appropriate Topology E. Selecting the Appropriate Media F. Media Access Methods G. Network Architecture H. Selecting the Appropriate Connectivity Devices I. Selecting the Appropriate LAN Protocol J. Wide Area Networks (WAN) K. Network Operating Systems Microsoft/Novell Overview L. Network Administration M. Resolving Common Network Problems N. Resolving Cable and Network Interface Card Problems O. Resolving Printer Problems II. NETWORK PRINTING A REVIEW...55 A. Network Print Services B. Novell NetWare Printing C. Print Server Process D. Windows Printing E. LPR/LPD Printing IV. CONCLUSION...58 V. GLOSSARY...59 Electronic Imaging Division 2 Manual

3 PREFACE In order to prepare you for the Electronic Imaging Division (EID) training class, we have developed the Digital Connected Products Training Class, Network Fundamentals Manual (Manual). The purpose of the Manual is to provide the student with a basic review of network printing technologies. The Manual is intended to supplement a students course material received during their EID training program and therefore, provide additional resources necessary to implement and support a given TOSHIBA connected product. The Manual is not intended to review all current state-of-practice networking techniques, nor provide a stand-alone document addressing concepts necessary to adequately support a LAN administrator or similar network professional. It is understood that a student has at minimum a basic, if not intermediate understanding of networking concepts prior to attending a TOSHIBA EID digital product training class. Certain concepts essential to network professionals (e.g., fault tolerance, data backup) will be addressed in the Manual only to the extent that the student will be aware of that concept in a networking environment although that certain concept may not be directly applied to a TOSHIBA connected product. Together, the Manual, course materials, and successful completion of the Instructor-led EID training program will provide an integral part of your understanding TOSHIBA digital network products. Electronic Imaging Division 3 Manual

4 DISCLAIMER TOSHIBA America Business Solutions (TOSHIBA) makes no warranty, or representation, either expressed or implied, with respect to this document or its content, its quality, performance, or fitness for a particular purpose. The information is provided on an as is basis. TOSHIBA will have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this document. Electronic Imaging Division 4 Manual

5 I. INTRODUCTION Understanding the fundamentals of a computer network and network-printing environment are critical if you wish to sell, implement, configure, and support TOSHIBA digital network products. The Electronic Imaging Division (EID) of TOSHIBA offers Instructor-led classroom training programs for each of its digital copier products to qualified dealers and technicians. To this end, TOSHIBA requires each student to posses minimum qualifications regarding his/her knowledge of computer networks. A current list of acceptable certifications is located on TOSHIBA s FYI site ( under the service/training sections. TOSHIBA also provides technical resources after completion of the training course by offering telephone support through its In-Touch Center ( ), Color Support Hotline ( ), and World Wide Web access to product documentation ( With successful completion of the Instructor-led EID training program you will become familiar with the installation and configuration of TOSHIBA digital connected products in a network environment and be able to support those products with a high degree of confidence. Electronic Imaging Division 5 Manual

6 II. NETWORKING FUNDAMENTALS A REVIEW A. Network Functionality Overview A computer network is a physical and logical electronic data communication system that allows the sharing of resources between multiple users and machines. A network may be located within a geographically small area (e.g., within a building) known as a Local Area Network (LAN), span across large areas (e.g., cities, states, or countries) known as a Wide Area Network (WAN), or be connected to multiple networks such as the Internet. Any given network (e.g., LAN, WAN) is a collection of interconnected computing devices and peripherals. In order for a network to function, three essential components must exist: 1) media, 2) protocol, and 3) a network service. Although there are numerous other components, which make up a computer, peripheral, network, or integrated system, these three components are the essential core necessary to provide shared access on a network. An example of commonly used media is the cable or wire (including fiber optics) that physically connects the hardware. The most common of these types of media is copper wire known as unshielded twisted pair (UTP). Examples of commonly used protocols include TCP/IP, IPX/SPX, and NetBEUI. The latter component, service, is used to provide the direction or management of network system services and functionality. Typically a client (i.e., workstation) service is invoked to act as a redirector or grabber of network resources, while a server service functions as a giver of network resources. Standardization Within a given network environment, many different manufacturers products may exist. In order for data transfer to be successfully accomplished over a network, all hardware and software must work together and communicate in a common language. Communication between computers on a network would be a simple task if a single manufacturer created all of the components of that network. However, thousands of companies provide networking hardware and software products, therefore, a common standard must exist in order for communication to be compatible, and therefore successful. Electronic Imaging Division 6 Manual

7 The International Standards Organization (ISO) is a worldwide organization that promotes international standards. During the 1980s, the ISO began efforts to develop a set of protocols that would allow multi-vendor network environments to communicate with one another using industry standard protocols. The result of these efforts was the development of the Open Systems Interconnection (OSI) Model. The OSI Model established the standards for communicating with the same peer protocol layer running on the opposite computer (virtual connectivity) and provides services to the layer above it, except for the Application Layer. The OSI Model divides data communication into seven functions, or layers, which describe how information flows from one end-user to another. Each layer prepares information for, and communicates with the one above or below it. Table 1 presents each layer of the OSI Model and its respective function, associated network component and protocols/services. The table is provided in order to present a generic overview of the OSI Model and its relationship to network components; it is not intended to represent a specific operating system, nor is it intended to provide a detailed completeness of all protocols or ISO standards. Electronic Imaging Division 7 Manual

8 Table 1. OSI Layers OSI LAYER FUNCTION COMPONENT PROTOCOLS SERVICES SMB, SNMP, Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Provides standard services to applications and end-user interface. Handles general network access, and flow control. Translates data from Application Layer to a format the Session Layer can understand. Performs data format conversion. Provides data compression, encoding, and encryption. Allows two applications on different computers to establish, use, and terminate a connection called a session. Synchronizes communications between computers; controls when users can send and receive data. Manages connections and provides reliable packet delivery between sending and receiving computers. Breaks long messages into several packets. Reassembles the packets when in receiving mode. Operates in units of messages. Translates addresses and routes data from one node to another. Performs fragmentation and reassembly, packet switching, and routing. Operates in units of packets. Consists of 2 sublayers. Operates in units of frames. Logical Link Control (LLC): Defines how data is transferred over the media and provides data link services to higher layers. Media Access Control (MAC): Defines who can use the network when multiple computers are trying to access it simultaneously Defines physical hardware connection specifications, and electrical and wiring specifications. Responsible for transmitting data across a wire. Operates in units of bits. Gateways Routers Bridges Switches Hubs Repeaters SMTP, FTP, HTTP, Telnet, LPR, LPD, RSH Postscript Redirector DHCP TCP UDP NWLink SPX IP, ARP, RARP, IARP, Ping, IPX, NetBEUI, RIP SLIP PPP CSMA/CD Token Bus Token Ring Demand Priority The upper layers of the OSI model (e.g., Application Layer) are software oriented whereas the lower layers (e.g., Physical Layer) are more hardware dependent. Electronic Imaging Division 8 Manual

9 Most network equipment manufacturers now build their networking products in compliance with the OSI Model. The purpose of each layer in the OSI Model is to provide a service to the next higher software layer. The service consists of dividing communication tasks into smaller subtasks, which can be utilized by specific protocols at their respective layer. Communication between one computer and another begins at the Application Layer. Data travels down through the layers, across the wire to its destination, and up through the layers to the receiving computer s application. There is a virtual connection between layers from one computer to another (Figure 1). Figure 1. The OSI Model Computer 1 (Sending) Computer 2 (Receiving) Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Network Cable/Wire Prior to data passing from one layer down to another, messages are converted into a more manageable unit (i.e., packet, frame, and bit [Figure 2]). Electronic Imaging Division 9 Manual

10 Figure 2. Data Packet Message Data When the data message arrives at the next lower layer, additional information is added to it in order to identify it on the network and insure data integrity (Figure 3). This additional information may include addressing (source/destination), formatting, and error checking. When the packet arrives at the Physical Layer, it is processed into bits, which are ready for physical transmission across the media to the destination computer (Figure 4). Figure 3. Packet Preparation Application Header Data Presentation Header Session Header Transport Header Network Header Data Link Header Data Link Trailer (CRC) Frame Preamble Packet Electronic Imaging Division 10 Manual

11 All packets have certain common components. These include: Header Source address Destination address Alert signal Clock information Reassemble sequence code for the receiving computer Data Data Trailer Error checking component (CRC) Figure 4. Completed Data Packet Header Data Trailer The sending computer breaks data into smaller sections, adds addressing information (e.g., source, destination, formatting, and error-checking) to it, and prepares the data for actual transmission to the media, and over the network. When the bits of data arrive at the destination computer, the process is essentially reversed; the bits will be re-assembled as they pass up the software layers. The receiving computer takes the data off the wire, brings in the data via a network adapter card, strips off all transmission data from the packets, copies the data from the packet into a buffer for re-assembly, and passes the reassembled data to the Application Layer. This sequence, although simplified in this example, is necessary for the transmission of data from one computer to another in a form that is understood by the receiving computer and ultimately the end-user. Electronic Imaging Division 11 Manual

12 B. Client/Server vs. Peer-to-Peer Networking TOSHIBA There are three basic configurations a local area network will operate under; a peer-to-peer network, a client/server network, or a combination of the two (i.e., hybrid). Given the function, there are three basic roles that a computer will assume on a network: Client a client will utilize, but not provide network resources, Peer a peer can utilize, and provide network resources, and Server a server generally provides, but does not utilize network resources. In a Peer-to-Peer network, there is no centralized administration, and users typically share their resources however they deem necessary. The end-user stores resources on his/her local machine. There are no servers in a Peer-to- Peer network, and therefore the network will generally have little or no security. Peer-to-Peer networks are organized into logical groupings called workgroups. In a Client/Server network, a server provides access to network resources through centralized administration and security. No computer users can access the resources of a network unless a server has authenticated them. Authentication occurs when a user logs onto the network from a client machine which has an account on the network server. Server-based networks provide a single logon procedure which allows users to connect to multiple computers and resources. A hybrid network is a combination of Peer-to-Peer and Client/Server components. Computers function as clients, peers, and servers, and the network will likely have domains and workgroups. Although most shared network resources will be located on a server, each peer also has the ability to share resources. Users do not have to logon to domain controllers in order to have access to local resources. Security Models Share Level (Password-Protected Shares) Share level security is a simple method that allows any user to obtain access to any resource if the user knows the password to that specific resource. This security model is used primarily with Peer-to-Peer networks. User Level (Access Permissions) Security is based on permissions granted to the user during a network logon session. Permissions are based on the user level such as administrator, print manager, end-user, accounting etc. This method is more secure than the share level permissions, which grant access to resources to anyone who knows the password to the shared resource. This method of security is generally used with Electronic Imaging Division 12 Manual

13 dedicated server operating systems, which maintain an ACL (Access Control List). C. Network Operating Systems The network operating system (NOS) is a supervisory software program that resides on the server. It controls how the network operates by defining who can use the network and how information and resources (e.g., printers, modems, and file servers) are shared with other workstations. Without a NOS, computing devices would remain isolated even when physically linked. A NOS will provide a set of protocols for accepting requests from clients and responding to those requests. In addition, a NOS will provide a shared file system, and security features. Most industry standard NOSs operate as dedicated servers and are controlled by administrators who manage system policies, permissions, profiles, and security issues. Client computers operate redirectors, which transmit requests for network service to a dedicated network server. Common NOSs include: Novell IntranetWare Microsoft Windows NT Server AppleShare Banyan Vines IBM OS/2 Warp Server Sun Microsystems Solaris Unix/Linux D. Selecting the Appropriate Topology The physical layout of a network is its topology. The term topology has two meanings regarding network cabling. One meaning refers to a logical description that describes how the data signal travels. For example, in Token Ring the data logically travels in a loop or a ring. The second meaning refers to how the physical layout of the cable appears. For example, in Token Ring, the cable topology often physically resembles a star arrangement. Conversely, Ethernet is logically a bus topology, and can be installed as either a physical bus or a physical star topology. Three prevalent types of network topologies are star, bus, and ring, and include hybrid designs of each topology. The topology of a given network depends on the media access method(s) it uses and type(s) of cables that are installed. Whereas small networks with clusters of network devices tend to employ only one topology, large networks that span a wide physical area or several floors of a building may use a combination of topologies. Electronic Imaging Division 13 Manual

14 Star A star topology describes a physical layout where cables emanate from a central hub and terminate at a single computer. Each cable run is a point-to-point connection. Token Ring, Ethernet, and ArcNet are all capable of being wired into a physical star topology. Cable breaks in a star topology usually affect only one station, however, if the central point (e.g., hub) fails, the entire network will not function. Figure 5. Star Topology Bus A bus topology logically can be thought of as a single cable with two distinct ends. Ethernet is logically a bus topology, and when installed with 10Base2 or 10Base5 cable (see Section II. E), it is a physical bus as well. Physical bus implementations allow the nodes (devices) to attach at various points along the cable. When a device transmits onto the bus, data travels in both directions toward the ends of the cable. Each cable end must be terminated with a resistor in order to absorb the signal energy when it reaches the end of the cable. If a cable is not properly terminated, each packet may reflect and collide with itself causing errors. Cable breaks in a physical bus implementation affect all computers attached to the bus. Figure 6. Bus Topology Electronic Imaging Division 14 Manual

15 Ring A ring topology circulates packets in a loop or a ring. The data on a given ring always travels in one direction. Each device is physically part of the ring in that the signal actually passes into then out of each device. Each device regenerates and transmits the signal to the next device in the ring. FDDI (Fiber Distributed Data Interface) is composed of two rings, one moves data in a clockwise direction while the other moves data in a counter-clockwise direction. The dual rings can keep the network operational in the event of a cable break. Figure 7. Ring Topology Star-Wired Ring The star-wired ring has essentially replaced the ring topology in practical use. Networks based on star-wired ring topologies have nodes radiating from a wiring center or hub. The hub acts as a logical ring with data packets traveling in sequence from port to port. Similar to a star topology, if one node fails, the network will continue to operate. Figure 8. Star-Wired Ring Topology Electronic Imaging Division 15 Manual

16 Star Bus The star bus topology links several star hubs together with bus trunks. If one computer fails, the hub can detect the fault and isolate the computer. If a hub fails, computers connected to it will not be able to communicate, and the bus network will be broken into two segments. Figure 9. Star Bus Topology The topology selected for a given network is based on a combination of several issues, some of which include cost, number of users, distance between nodes, and scalability. A summary of topology advantages and disadvantages are presented in Table 2. Table 2. Topology Summary TOPOLOGY ADVANTAGE DISADVANTAGE Simple, reliable in small networks. Difficult to troubleshoot. A cable Bus Inexpensive, and easy to expand with BNC connectors and repeaters. break along the bus will bring down the network. Heavy network traffic can slow a bus considerably. Each BNC can weaken the signal. Ring Star Every computer given equal access to token; no one computer can dominate the network. If capacity is exceeded, degradation is graceful rather than a sudden failure. Easy to modify and add new computers. Easy to troubleshoot. Single computer failure will not bring down entire network. Supports multiple cable types. Failure of one node can bring down the ring. Adding or removing a computer from the ring disrupts communication. Difficult to isolate problems. Central point failure brings down entire network. Cost is high due to centralizing all nodes into one point. May require central device to switch or rebroadcast signal. Electronic Imaging Division 16 Manual

17 E. Selecting the Appropriate Media Cable is what physically connects network devices together, serving as the conduit for information traveling from one computing device to another. The type of cable utilized for a given network will be dictated in part by the network's topology, size and media access method. Small networks may employ only a single cable type, whereas large networks tend to use a combination of different types of cable (e.g., copper wire, and fiber). The three most common types of cable utilized throughout the world are twisted pair, coaxial, and fiber. A brief discussion of each of these types of cables follows. Twisted Pair Cable Twisted-pair cable is a generic term that describes many different cable styles and specifications. Terminology associated with twisted-pair cabling originated within the telephone company community. Cable may or may not include shielding; UTP is unshielded twisted-pair while STP is shielded twisted-pair. UTP wiring, carries signal 100 meters. UTP is susceptible to crosstalk, which is signal overflow from adjacent wires. STP wiring, carries signal 100 meters. STP has a foil or braided jacket around wiring to help reduce crosstalk and to prevent electromagnetic interference. Figure 10. Twisted Pair Cable STP Shielding Electronic Imaging Division 17 Manual

18 Table 3. Cable Type CATEGORY MEDIA (TYPICAL) SPEED 1 Voice N/A 2 Voice 4Mbps 3 Data 10Mbps 4 Data 16Mbps 5 Data 100Mbps The number of pairs of wires in a cable is typically specified (e.g., 4 pair or 2 pair). Typically solid conductor twisted-pair cable is installed through the walls and ceiling. Each in-wall cable typically terminates in a wall plate connection near the user workspace and at a patch panel near the central hub. Twisted pair cable uses RJ-45 connectors. Patch cables connect the workstation to the wall plate connection; another patch cable connects the patch panel connection to a port on the central hub. Twisted-pair cabling is manufactured to various specifications regarding the number of twists per foot, wire gauge size, and electrical characteristics (e.g., Category 3 or Category 5). Coaxial Cable Coaxial cable falls into two main categories, thick or thin. With thin cables there are several styles, for example Ethernet uses one style while ArcNet uses another. Characteristics such as maximum length, number of devices allowed, and connector types also vary. Thin cable typically uses BNC (British Naval Connectors) connectors. The core carries the data while the braided metal near the outside provides shielding to prevent interference from electrical noise and crosstalk. The conducting core and the wire mesh must never come in contact with each other. Coaxial cable is more resistant to interference and attenuation than twisted pair cabling. Coaxial cable will transmit voice, data and video. Figure 11. Coaxial Cable Outer shield Insulation (PVC, Teflon) Copper wire mesh or aluminum sleeve Conducting core Electronic Imaging Division 18 Manual

19 Thinnet Coaxial Cable 0.25 inches diameter Carries signals up to 185 meters Known as RG-58 family 50 Ohm impedance Thicknet Coaxial Cable 0.5 inches diameter Carries signals up to 500 meters Known as Standard Ethernet Generally used as a backbone Fiber-Optic Cable Fiber-optic cable is constructed of flexible glass and plastic. In fiber-optic cable, the optical fibers (i.e., glass ) carry digital signals in the form of modulated pulses of light (i.e., photons). Each glass strand passes signals in only one direction, therefore a fiber cable must consist of two strands in separate jackets; one strand transmits data and one strand receives data. Figure 12. Fiber-Optic Cable Optical Fiber (core) Glass Clading Fiber Optic Connector Kevlar Protective Outer Sheath Fiber-optic cable is resistant to electronic interference and therefore is ideal for environments with a considerable amount of noise (e.g., electrical interference). Furthermore, since fiber-optic cable can transmit signals further than coaxial and twisted-pair, more and more companies are installing it as a backbone in large facilities and between buildings. The cost of installing and maintaining fiber-optic cable remains too high, however, for it to be a viable network media connection for small networks. Fiber-optic cable transmissions are not subject to electrical interference and are extremely fast (e.g., 100Mbps- 1Gbps). Electronic Imaging Division 19 Manual

20 Signal Transmission There are two primary methods of data transmission regarding cables; baseband and broadband. Baseband baseband systems use digital signaling over a single frequency signals flow in the form of pulses of electricity or light the entire communications channel capacity is used to transmit a single data signal each device on a baseband network transmits bi-directionally some devices can transmit and receive at the same time signals decrease in strength as they travel along the cable repeaters are used to retransmit the signal along the cable Broadband transmission signal flow is unidirectional signals are continuous and non-discrete broadband systems use analog signaling and a wide range of frequencies signals flow across the medium in the form of electromagnetic or optical waves requires amplifiers to regenerate analog signals at their original strength can transmit in the multi-megabit and gigabit range If sufficient total bandwidth is available, multiple analog transmission systems such as cable television and network transmissions can be supported simultaneously on the same cable. Since broadband transmission signal flow is unidirectional, there must be two paths for data to flow in order for a signal to reach all devices. A mid-split broadband system divides bandwidth into two channels; one channel transmits data and one channel receives data. F. Media Access Methods In order for computers to effectively share access with other devices over a given medium, specific rules must be implemented to enable error-free transmission. A media access method defines how computing devices access the network cable and send data. Ethernet, Token Ring and LocalTalk (Apple) media access methods are used primarily for connecting desktop machines (computers, printers etc.) to the network, whereas FDDI, CDDI, Fast Ethernet and ATM are used primarily for high-speed backbones, high-speed network access (e.g. file servers) and very high-speed workgroup applications. There are two primary approaches to media access control; 1) contention, and 2) deterministic. Contention Within the contention approach, there are two functional types of media access control. Each type is used to determine if more than one node is attempting to Electronic Imaging Division 20 Manual

21 access the network at the same time. They both are based on sensing signals each computer emanates to the network cable, hence the name Carrier Sense Multiple Access (CSMA). CSMA is used in two different capacities; collision detection (CD), and collision avoidance (CA). CSMA/CD uses a method where every node on a network will wait to send data only when no other computers are heard on the cable. When a computer detects another computer transmitting, the network adapter card assumes a collision has occurred and it will not transmit its own data. The computer using CSMA/CD will wait until the network is silent before sending its own data. This method attempts to avoid data collisions caused by more than one computer transmitting data at the same time. CSMA/CA is similar to CSMA/CD in that each computer waits for a silent cable. However, CSMA/CA does not check for collisions by listening for other computers transmitting. CSMA/CA will evaluate whether the data was successfully transmitted by waiting for an acknowledgment from the recipient. If an acknowledgment is not received, it assumes the transmission between the two computers will be resent, and therefore it will not send its own data. If an acknowledgement is detected, the sending computer will assume a free line and begin data transmission. Deterministic This method of media access control allows a level of certainty as to the maximum time a computer will have to wait to gain access on the network. This is usually accomplished by passing a token between computers on the network. When a computer receives the token, it is allowed to transmit its data onto the cable. After the recipient has acknowledged the arrival of data, the sending computer will release the token, which allows other computers to capture it (token) and transmit data. Demand Priority It is possible that two computers, listening to the network for silence, may transmit data at exactly the same time. Demand Priority utilizes the hubs and repeaters of a network, where data will be given priority if two computers transmit data at exactly the same time. The data with the highest priority is allowed to transmit first. If the data have the same priority, Demand Priority method allows for the transmission of both data but alternates between small blocks from each computer. Although there are other media access method controls, and newer ones currently being developed, the aforementioned methods are the most common ways of controlling access in today s network environments. Table 4 presents a summary of media access control methods. Electronic Imaging Division 21 Manual

22 Table 4. Media Access Methods (Typical) ACCESS METHOD ACCESS METHOD CONTROL TOPOLOGY COMMON CABLES USED Ethernet CSMA/CD Star or Bus Twisted-pair, coaxial, fiber Fast Ethernet Demand Priority Star Twisted-pair, fiber Token Ring Deterministic Star-wired Ring Twisted-pair, fiber LocalTalk CSMA/CA Bus Twisted-pair FDDI Deterministic Dual ring, Star-wired ring Fiber CDDI Deterministic Star-wired ring Twisted-pair ATM Dedicated circuits Star Fiber, twisted-pair G. Network Architecture The structure of a network s architecture is defined by a set of standards and techniques necessary for designing and building network communication systems. There are third-party proprietary architectures such as IBM s SNA (Systems Network Architecture) and DEC s DNA (Digital Network Architecture). In addition there are open architectures such as the OSI (Open Systems Interconnection) Model defined by the ISO. The following provides a discussion of one of the most common network architectures in existence today, Ethernet. In addition, a brief overview of Fast Ethernet, Token Ring, LocalTalk, FDDI, and CDDI will be discussed. Ethernet Overview Ethernet is the most widely used LAN technology in use today. Approximately 80% of LANs today use Ethernet for installed network connections. The IEEE specification defines the Ethernet standard. The Ethernet specification covers rules for configuring LANs, the type of media that can be used, and how the elements should be networked together. The Ethernet protocol provides the services called for in the Physical and Data Link Layers of the OSI reference model. Every Ethernet network adapter is identified by an address. This address is 48 bits long, and all manufacturers of Ethernet equipment cooperate to make sure that this address is unique; it is different for every single Ethernet device. This address is called the MAC (Media Access Control) address. One element of the specification states that Ethernet networks run at 10 million bits per second (10Mbps) or at a rate of 100 million bits per second (100Mbps) which is commonly refereed to as Fast Ethernet. The transmission of data at these rates is what is referred to as how fast the traffic is on the network. Electronic Imaging Division 22 Manual

23 In addition to the speed of network traffic, specification defines the access method used by computers connected to the LAN. The specified access method is CSMA/CD. On an Ethernet network, a single communication environment (the ether ) propagates signals from one computer to every other computer. All computers are free to put signals on the wire at any time. Occasionally, two computers will send signals out at the same time. When this happens, a collision is said to occur. The computer networking hardware is designed to detect such a collision. When a collision occurs, both computers wait a random length of time, and then re-send their messages. Ethernet Wiring Ethernet can be implemented at different data transmission speeds and over different types of media. This portion of the Ethernet specification addresses the Physical Layer of the OSI reference model. There are several different Physical Layer (e.g., media) specifications. The following list describes the different varieties of Ethernet. Note that the first number in the name refers to the speed in Mbps, Base refers to baseband, and the last number represents a distance standard (or a T for twisted pair). 10BaseT 10 Mbps, baseband transmission Maximum length of a 10BaseT segment is 100 meters (328ft) Minimum cable length between computers is 2.5 meters A 10BaseT LAN will serve 1,024 computers Twisted pair cable categories 3, 4 or 5 Hub to Card/Transceiver distance 100 meters Backbones for Hubs, Coaxial or fiber-optic to join a larger LAN Total computers per LAN without connectivity components, 1024 by specification Uses RJ-45 connectors 10Base2 10 Mbps, baseband transmission Thinnet coaxial cable (RG-58), 0.25 inches diameter Maximum length of a 1OBase2 segment is 185 meters (607ft) Five segments connected by four repeaters Rule, three of the five segments may be populated Maximum total network length 925 meters (3,035ft) Minimum cable length of 0.5 meters (20 inches) Maximum 30 computers (and repeaters) per 185 meter segment Maximum number of computers per network without connectivity components, 1024 by specification Uses BNC connectors Electronic Imaging Division 23 Manual

24 Because normal Ethernet limits would be too confining for a large business, repeaters can be used to join Ethernet segments and extend the network to a total length of 925 meters. 10Base5 - Standard Ethernet 10 Mbps, baseband transmission Thicknet coaxial cable, 0.50 inches diameter Maximum length of a 10Base2 segment is 500 meters Five segments connected by four repeaters Rule, three of the five segments may be populated Maximum total network length 2,500 meters (8,200ft) Maximum computer-to-transceiver distance 50 meters (164ft) Minimum distance between transceivers 2.5 meters (8ft) Maximum I 00 computers (and repeaters) per segment Rule A Thinnet network can combine as many as five cable segments connected by four repeaters, but only three segments can have client workstations attached. Therefore, two segments are untapped and are often referred to as inter-repeater links; this is known as the rule. 10BaseFL Ethernet over Fiber-Optic cable. 10BaseFL (10Mbps, baseband, over fiber-optic cable) is an Ethernet network that typically uses fiber-optic cable to connect computers and repeaters. The primary reason for using 10BaseFL is for long cable runs between repeaters, such as between buildings. The maximum distance for a 1OBaseFL segment is 2,000 meters. 100VG-AnyLAN Designed by Hewlett-Packard and combines elements of Ethernet and Token Ring. Defined by which specifies a standard for transmitting Ethernet frames and Token Ring packets. Also known as 100BaseVG, VG and AnyLAN. 100BaseX (Fast Ethernet) 100BaseT4 (4-pair Category 3, 4, or 5 UTP) 100BaseTX (2-pair Category 5 UTP or STP) 100BaseFX (2-strand fiber optic cable) In a 10Base2 network, a single length of coaxial cable connects the entire network. The diagram below presents a 10Base2 configuration using Thinnet (RG-58) cable and BNC connectors. Electronic Imaging Division 24 Manual

25 Figure 13. Thinnet Bus Coaxial Cable The connection at each computer is made with a BNC T-connector. T Connector Connector to Computer NIC Coaxial Cable The computer at the end of the wire uses a BNC - T Connector with a terminator. Terminator T Connector Connection to Computer NIC The electrical properties of the RG-58 cable system are critical. Proper grounding is vital to correct data transmission. Physical damage to the cable, such as a crimp, can bring down all communication. Missing one of the two terminators will also prevent communication. Electronic Imaging Division 25 Manual

26 10BaseT and 100BaseT Network Both 10BaseT and 100BaseT networks are wired together using twisted pair cable similar to the type that is used for telephone connections. In both cases, the cable must meet rigid electrical specifications. The higher speed 100BaseT must meet a specification called Category 5. To all outward appearances, 10BaseT and 100BaseT networks look physically identical. Hub Figure 14. Twisted Pair Network In a 10BaseT or 100BaseT network, all of the computers are wired into a single connection point, called a hub. The hub takes the signal out of each computer and connects that signal to all the other computers via ports. Because each computer is connected to the hub separately, a bad cable will only affect a single computer. The cable plugs into the hub and the computer using a RJ-45 connector, which is similar to a large telephone jack. BNC T-connectors and terminators are not used with xbaset network devices. Figure 15. RJ-45 Connector Electronic Imaging Division 26 Manual

27 Table 5. IEEE Ethernet TOSHIBA SPECIFICATION 10BASE2 10BASET Topology Bus Star Bus Cable Type RG-58 Thinnet Coax Category 3, 4, 5 UTP Connection to Adapter BNC T-Connector RJ-45 Terminator resistance (OHMS) 50 Terminator Not Used Max. Cable Length 185 m 100m Max. Segments 5 (using 4 repeaters) with only 3 populated segments 5 (using 4 repeaters) with only 3 segments populated Max. Network Length 925m N/A Max. PCs Per Segment 30 (1024 per network) 1 (each PC has cable to hub) Fast Ethernet Fast Ethernet refers to 100 Mbps Ethernet. There are two significant sources of supporting technology regarding the implementation of this network type. One supports 100BaseVG, a significant modification to CSMA/CD. The second, comprised of more than 80 companies (known as the Fast Ethernet Alliance), supports 100BaseT, which at the MAC layer, retains many of the same characteristics as 10BaseT. 100BaseVG and 100BaseT are not compatible with each other or with existing IEEE Ethernet standards. They each have their own standards, IEEE Standard 802.3u for 100BaseT, and for 100BaseVG. Specific bridges, routers or switches must be used to interconnect these technologies. Token Ring The Token Ring architecture was developed by IBM Corporation in the mid- 1980s and subsequently defined by the IEEE in Project 802. Since Token Ring is IBM's preferred method for networking, it is found primarily in large IBM mini and mainframe installations. Due to the increasing popularity of Ethernet, the rate of growth of Token Ring networks has decreased. Token Ring networks use a star-wired ring topology over UTP and STP wiring. A hub (referred to as a MAU [Multi-Station Access Unit]) is at the center of the ring. Two versions of Token Ring are available: 4 Mbps and 16 Mbps. Token Ring networks use a token passing media access control mechanism to circulate packets around the ring. An electronic token travels from station to station in a single, logical direction. If the token is free, a station can attach data to the token, change the token's status to busy, and then send the token on to the next station. Each consecutive station then checks the destination address of the data to see if it should process the data. If the destination address does not match the computer viewing it, it then passes the token on. When the station that originated the token receives it back, it removes the data from the token and changes the token status back to free. Electronic Imaging Division 27 Manual

28 LocalTalk LocalTalk is a proprietary media access method built into Apple Macintosh computers and LaserWriter printers. LocalTalk networks are best suited to small networks using Macintosh computers (e.g. an independently networked classroom). With LocalTalk, computers are set up in a bus configuration using both UTP and STP wiring. LocalTalk transmits at only 230 Kbps or about 1/40 the rate of Ethernet. For this reason, many schools and universities are upgrading their LocalTalk Macintosh installations to Ethernet in order to handle larger file transfers. LocalTalk uses the CSMA/CA media access control mechanism for transmitting data. FDDI The FDDI (Fiber Distributed Data Interface) media access method transfers data at very high speeds (100Mbps) over fiber-optic cable. Like Token Ring, this access method employs a token passing media access control mechanism to transmit data. FDDI, however, uses a dual counter-rotating ring topology, meaning there are two rings of cable with two tokens circulating in opposite directions. This set-up creates a relatively fault tolerant network. Many institutions are installing fiber-optic backbone cables to carry Ethernet signals today and FDDI signals in the future. CDDI CDDI (Copper Distributed Data Interface) is an emerging technology that uses the FDDI media access control mechanism over copper (unshielded twisted-pair) cable. It is employed in a limited fashion to connect file servers and high performance workstations directly to an FDDI backbone. A clear disadvantage of CDDI is that the cost per port remains too high for it to be considered a viable networking solution for the typical desktop computer. H. Selecting the Appropriate Connectivity Devices Network Adapters The network adapter (Network Interface Card [NIC]) is the physical link between the computing device and the network cable. Typically, a network adapter is a card that slides into a computing device's expansion slot, providing a connector for attaching the network cable. A network adapter card is seated in either an ISA (Industry Standard Architecture) 8- or 16-bit slot, or a PCI (peripheral component interconnect) 32-bit slot. Network adapters can also be external units or built directly onto a device's motherboard. Network adapter cards are designed for a specific type of network, such as Ethernet, Token Ring, or FDDI. They operate at the Physical Layer of the OSI protocol stack. A network adapter converts parallel bus data into serial data for transmission over a wire. Electronic Imaging Division 28 Manual

29 Before a successful data transmission can be accomplished, the sending and receiving network adapter establish an electronic dialog and must agree on specific criteria such as; the maximum size of data groups to be sent, the amount of data to be sent before a confirmation, the time interval between sending data groups, the time interval to wait before confirmation is sent, and how much data each NIC can hold before it overflows. There are several methods used to increase the transmission rate of data from the network adapter card to the wire; Direct Memory Access data moves directly from the network adapter card to the CPU, Shared Adapter Memory the computer will use the memory onboard the network adapter, Shared System Memory the network adapter card will use computer memory, Bus Mastering network adapter card takes temporary control of the computer s bus, Buffering RAM, and Onboard Microprocessor - the network adapter does not rely on the CPU. Figure 16. Typical Network Adapter Card Interrupt Request Lines (IRQ) Interrupt request lines are hardware lines over which devices can send interrupts or requests for service to the computer's central processing unit (i.e., CPU). If the CPU is performing another task, the input, through the interrupt, allows devices to get the attention of the processor. Generally, IRQ settings must be specific for each device in order to avoid a conflict. Therefore, when installing a NIC, it is important to locate a free IRQ setting (e.g., one that is not already in Electronic Imaging Division 29 Manual

30 use). Most NICs are set to IRQ 5 since most computers on a network do not have sound cards or second printers. Following is list of standard IRQ settings typically found on most computers. Table 6. Common IRQ Settings IRQ DEVICE 1 Keyboard 2 Video (redirected IRQ 9) 3 Com 2, Com 4 4 Com 1, Com 3 5 Sound, LPT2, NIC 6 Floppy Disk Controller 7 LPT1 8 Real Time Clock (Reserved) 9 Redirected IRQ 2 10 Available 11 Available 12 Mouse 13 Co-Processor 14 HD Controller 15 Available I/O Base Port Address In addition to IRQ settings, most devices will use a small portion of upper memory to send and receive data from the CPU. The I/O base port specifies a channel through which information flows between the computer's hardware and its CPU. The port appears to the CPU as an address. Each hardware device in a system must have a unique I/O base port number address. The port numbers are in hexadecimal format. The most common addresses for NICs are 300 to 30F and 3l0 to 31F. Hub (Repeater) Hubs are also referred to as repeaters. Repeaters regenerate signals for retransmission, and move packets from one physical media to another. Repeaters will pass broadcast storms; they do not perform any isolation of packets. Repeaters are used to extend the length of a network segment or to connect different media types such as Ethernet Thicknet to Ethernet Thinnet. Repeaters cannot connect dissimilar media access methods together. For example, repeaters cannot connect a Token Ring segment to an Ethernet segment. Repeaters amplify and regenerate signals to their original level and operate at the Physical Layer of the OSI Model. Electronic Imaging Division 30 Manual

31 Standard 10BaseT Hub A standard 10BaseT hub is a typically an active (electrically powered) multi-port repeater with RJ-45 connections. It connects multiple computers running 10BaseT cable. The hub receives a signal from one computer (from its respective port) and sends the information to all the other connected ports. All connected devices must be running 10BaseT cable (Cat 3, 4, or 5) and 10BaseT network adapter cards. 100BaseT Hub (Fast Hub) A fast hub works the similar to a 10BaseT hub, but supports network transmission rates of 100Mbps. All connected devices must be running 100BaseT Ethernet network adapter cards, Cat 5 cable, and use RJ-45 connectors. 10/100BaseT Hub A 10/100BaseT hub operates by combining the transmission speed capabilities of 10- and 100 Mbps. It includes the functionality of a 10BaseT hub, a 100BaseT hub and utilizes a switch to translate between the two transmission speeds. Each port will switch between 10BaseT and 100BaseT as required by the device connected to it. It does not provide the dedicated circuit of a switch, but it does provide a lower cost way to mix 10BaseT and 100BaseT on the same network. Note: The switch used in a 10/100BaseT hub is not to be confused with a Switching Hub described in the following section. Bridge Bridges are used to segment networks; they forward packets based on address of destination node. Bridges use RAM to build a routing table based on hardware addresses, and will connect dissimilar network topologies such as Ethernet and Token Ring. Bridges will forward all protocols. Bridges are similar to repeaters in that they cannot distinguish protocols. Bridges also regenerate signals at the packet level and over time learn the MAC address of devices connected to network segments. As the bridge learns its environment, it begins to isolate packets to those network segments where the destination computer resides. Bridges forward all broadcasts to all attached segments. Switches Switches are hubs with bridging capabilities. Switches filter traffic through MAC addresses. Switches are used when upgrading to 100mb Fast Ethernet. The purpose of switching is to increase LAN performance by reducing the number of workstations on each LAN segment. The switch itself moves frames between ports at very high speeds so it does not introduce any delay to the network. The best performance is achieved with one workstation per port so that there is no contention at all when that workstation wants to transmit. The switch sets up a port connection between the sender and receiver for the duration of the transmission. Electronic Imaging Division 31 Manual

32 A switch, or switching hub, monitors the MAC address of each device connected to it. When a computer sends a packet to a switch, the switch examines the MAC address of the destination computer. Rather than sending this packet to all computers, the switch will send this packet only to the computer where it is destined to go. A switch greatly enhances communication bandwidth in an environment where packets are being sent between a lot of different computers. In an environment where all packets are going to or from a single machine (e.g. all workstations are sending to and receiving from a single file server) upgrading to a switch will not have a great effect. 10BaseT Switch A 10BaseT switch is essentially a multi-port repeater that operates at a maximum 10 Mbps. The difference between the repeater and the switch is based on the capabilities of the port. The repeater will only pass on transmissions to all other ports, while the switch will send transmissions to a specific port. 10/100BaseT Switch A 10/100 switch is similar to a 10BaseT switch, but each port can run at either 10BaseT or 100BaseT transmission speed. Using a 10/100 switch you can take advantage of a 100BaseT connection to your file server while keeping 10BaseT connections to your workstations. You can also use a 10/100 switch to migrate slowly from 10BaseT to 100BaseT. Router A router routes packets across multiple networks. Routers use RAM to build a routing table based on network addresses (i.e., IP address). A router shares status and routing information to other routers to provide better traffic management and bypass slow network connections. Routers are slower than bridges due to complex functions. A router strips off Data Link Layer source and destination addresses and then recreates them for packets. Routers can accommodate multiple active paths between LAN segments. Routers will not forward non-routable protocols such as NetBEUI. Routers operate at the Network Layer of the OSI Model and function by disassembling packets. Once open, the router examines the packet for its desired destination address. The router then decides which port to forward the packet onto. Routers perform an excellent job of isolating network traffic and limiting broadcasts. Like bridges, routers can also link unlike networks such as Ethernet and Token Ring. Gateway Gateways are highly complex devices used to link two or more networks with different network architectures. For example, a gateway would provide conversion and translation from Ethernet to IBM's SNA architecture when a PC workstation on a LAN needs to access an IBM mainframe, or when connecting Novell servers to Microsoft servers. Electronic Imaging Division 32 Manual

33 I. Selecting the Appropriate LAN Protocol TOSHIBA A protocol is a set of rules and conventions for sending information over the network. These rules govern the content, format, timing, sequencing, and error control of messages transmitted between network devices. A protocol can be compared to a language; just as two different people might use two different languages to communicate through the same telephone hardware, a physical network can support more than one type of transport protocol. A network operating system, such as Microsoft Networking, may support more than one type of transport protocol. Multiple protocols may be bound to a single network adapter card. For example, a computer may utilize TCP/IP, NetBEUI, or IPX/SPX, and operate with one network adapter. The order in which the protocol is bound determines the order of use by the computer. For example, if IPX/SPX is bound first, IPX/SPX will be used to attempt to make a network connection. If the connection fails, the computer will transparently attempt to use the next protocol bound to the network adapter card. NetBEUI (NetBIOS Enhanced User Interface) NetBEUI is a simple network layer transport protocol developed to support NetBIOS networks. NetBEUI is easily installed (self-configuring, and self-tuning), and requires low memory overhead. The disadvantages to using NetBEUI include its inability to transmit across a router, there is no support for cross platform applications, NetBEUI can generate more traffic than other protocols, and it does not scale beyond small networks. IPX/SPX (Internetwork Packet Exchange/Sequenced Packet Exchange) Novell NetWare servers and clients use this protocol. NWLink is the Microsoft implementation of IPX/SPX. This protocol works well in both LAN and WAN environments, and is routable. This protocol is usually required to access file and print services on a Novell server. Until very recently it was the only protocol natively supported by Novell NetWare. NetWare uses different frame types in connection with protocol use. The frame type adhering to the standard was used as the default in NetWare The frame type adhering to the standard was the default for subsequent releases of NetWare. Not all NetWare networks use the default frame type. If the frame type cannot be determined, many devices can automatically detect the frame type. TCP/IP (Transmission Control Protocol/Internet Protocol) This protocol has become the defacto standard worldwide due to its popularity. It works well in both LAN and WAN environments, is routable, and is supported by many operating systems and platforms. This protocol is required to access the Internet. Microsoft networking supports TCP/IP for Windows 95 and later clients, and for Windows NT. Every device on a TCP/IP network must have a subnet mask, and a unique IP address. If the device is located on a segmented Electronic Imaging Division 33 Manual

34 network, a default gateway is also required. TCP/IP is supported by the latest version of Novell NetWare (NetWare 5.0). Based on the worldwide use of TCP/IP as a common protocol, additional discussion regarding TCP/IP is presented in the foregoing section. TCP/IP is a standard communication language (i.e., protocol) used extensively throughout the world. It is the predominant protocol utilized on the Internet and in private networks (i.e., Intranet, Extranet). TCP and IP were developed by a Department of Defense (DoD) research project in order to connect a number of different networks (designed by different vendors) into a network of networks. The project was initially successful because it provided a few basic services everyone needed, including file transfer, electronic mail and remote logon. In December 1968, the Advanced Research Projects Agency (ARPA) awarded Bolt, Beranek and Bewman a contract to design and deploy a packet switching network. The project was called ARPANET and four nodes were in place by the end of 1969; connections to Europe were established by The initial host-to-host communication protocol used in ARPANET was the Network Control Protocol (NCP). NCP soon proved to be unable to maintain the growing network traffic load, and subsequently, TCP and IP were proposed and implemented in These two protocols provided a more robust suite of communications protocols. TCP and IP have had numerous revisions with the most notable being IP version 6, which was released in December In 1983, the DoD mandated that all of their computer systems would use the TCP/IP protocol suite for wide area communications. TCP/IP is not a single protocol, but rather a suite of protocols. Several of the protocols (e.g., TCP, IP, and UDP) provide "low-level" functions necessary for applications. Other protocols are necessary for conducting specific tasks (e.g., transferring files between computers, sending mail, or finding out who is logged in on another computer). These services should be present in any implementation of TCP/IP, except that micro-oriented implementations may not support computer mail. These traditional applications still play an important role in TCP/IP-based networks. The core of the TCP/IP protocol suite consists of TCP, and IP. Together, these two protocols compose a two-layered program. The upper layer (Transport) consists of TCP. TCP manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer on the client machine that reassembles the packets into the original message. The Electronic Imaging Division 34 Manual

35 lower layer (Internet) consists of IP. IP manages the address portion of each packet in connection with the destination. Each gateway computer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, the packets will be reassembled at the destination machine. TCP/IP uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network. TCP/IP communication is primarily point-to-point; communication is from one point (or host computer) in the network to another point or host computer Many Internet users are familiar with the even higher layer application protocols that use TCP/IP to connect to the Internet. These include; Data Transfer Utilities (Hypertext Transfer Protocol [HTTP], File Transfer Protocol [FTP], Trivial File Transfer Protocol [TFTP], and Remote Copy [RCP]); Remote Execution Utilities (Telnet, Remote Shell [RSH], and Remote Execution [REXEC]); and Printing Utilities; (Line Printer Daemon [LPD], Line Printer Requestor [LPR], and Line Printer Queue [LPQ]). In addition, the Simple Mail Transfer Protocol (SMTP), and Simple Network Management Protocol (SNMP) are included with TCP/IP. These and other protocols are often packaged together with TCP/IP as a "suite." Personal computer connections to the Internet are usually through the Serial Line Internet Protocol (SLIP) or the Point-to-Point Protocol (PPP). These protocols encapsulate the IP packets in order to deliver them over wide areas from a dial-up phone connection. To this end, PPP and SLIP may be considered WAN protocols while TCP/IP may be considered a LAN protocol. Protocols related to TCP/IP include the User Datagram Protocol (UDP), which is used instead of TCP for special purposes. Other protocols are used by network host computers for exchanging router information. These include the Internet Control Message Protocol (ICMP), the Interior Gateway Protocol (IGP), the Exterior Gateway Protocol (EGP), and the Border Gateway Protocol (BGP). Electronic Imaging Division 35 Manual

36 Figure 17. TCP/IP Protocol Suite TOSHIBA OSI Model Protocols Services TCP/IP Protocol Layers Application Presentation Session FTP Telnet TFTP SMTP LPD LPR LPQ RCP HTTP SNMP REXE C RSH Application Transport TCP UDP Transport Network Data Link ARP/RARP LAN Technologies: Ethernet, Token Ring, FDDI IP WAN Technologies: Serial Lines Frame Relay, ATM ICMP IGMP ARPANet Internet Network Common TCP/IP Protocols by Layer TCP/IP represents a collection of network protocols, services, and utilities that provide services at the network and transport layers of the OSI Model. The foregoing section presents the most common of these components organized by the layer in which they are managed. Application Layer: Provides the ability of one application to communicate with another application independent of the hardware platform. TELNET runs commands interactively in a terminal emulation application uses TCP to achieve virtual connection between client and server ability to transfer binary data, emulate graphics terminals, support macros Allows a client to appear as a terminal directly attached to the host (terminal emulation) Text mode, menus, and command execution Cannot download Electronic Imaging Division 36 Manual

37 FTP File Transfer Protocol File transfer and directory access between client and host copies files to/from a remote host reliably over TCP cannot execute files user level of authentication TFTP Trivial File Transfer Protocol copies files to/from a remote host quickly over UDP does not provide directory browsing does not use user-level authentication SMTP Simple Mail Transfer Protocol mail transfer SNMP Simple Network Management Protocol allows diverse network objects to participate in a global network management architecture network management systems can poll network entities implementing SNMP for information network management systems learn of problems by receiving traps from network devices implementing SNMP Printing Utilities LPD Line Printer Daemon responds to LPR/LPQ requests sends print job data to the print device LPR Line Printer Requestor submits a print job to a LPD server LPQ Line Printer Queue queries the print job list of an LPD print server Electronic Imaging Division 37 Manual

38 Data Transfer Utilities RCP Remote Copy copies files to/from a remote host with no authentication Web Browsers Microsoft Internet Explorer and Netscape Navigator/Communicator use HTTP (Hypertext Transfer Protocol) to transfer pages of data from a Web server Remote Execution Utilities REXEC Remote Execution starts a process on the remote host requires user account on TCP/IP host RSH Remote Shell runs commands on a remote host requires user name in.rhosts file on UNIX host Transport Layer: Communication sessions between computers. Error checking and acknowledgement. TCP Transmission Control Protocol connection oriented: establishes a session before exchanging data reliable delivery: sequence numbers, acknowledgments retransmits packets if error in transmission UDP User Data Protocol (UDP) provides a simple but unreliable message service for transaction-oriented services connectionless: no session is established does not guarantee delivery: no sequence numbers, no acknowledgments Electronic Imaging Division 38 Manual

39 Internet Layer: Encapsulation of data into packets, routing algorithms. IP Internet Protocol connectionless: no session is established addresses and routes packets does not guarantee delivery: no sequence numbers, no acknowledgments ARP/RARP/IARP Address Resolution Protocol/Reverse Address Resolution Protocol/Inverse Address Resolution Protocol/ successful mapping of an IP address to a hardware address successful mapping of a hardware address to an IP address address resolution is the function of ARP uses local broadcast address mappings are stored in cache for future reference ICMP Internet Control Message Protocol Messaging on behalf of IP (e.g., Destination host unreachable ) IGMP Internet Group Management Protocol group membership advertisement Network Layer: Putting packets on the wire and retrieving packets from the wire. LAN Protocols Ethernet, Token Ring, ARCnet, etc. WAN Protocols: PPP, X.25, Frame Relay, etc. IP Addressing In order for a computer, workstation, device, or host to be identified on a network, it must have the following: 1) a unique physical address, 2) a name, or 3) an IP host address. The physical address is the MAC address that is hard-wired into the network adapter card. The MAC address is used for LAN addressing, and not internetwork addressing. The name is either a computer name (i.e., NetBIOS name), and/or a domain name (i.e., host name). Typically, the name provides a recognized identification for a host on an IP network. While users typically use a name, they must be resolved into an IP address. The resolution of an IP address Electronic Imaging Division 39 Manual

40 into a NetBIOS name is accomplished by a Windows Internet Name Server (WINS), and the resolution of an IP address into a host name is accomplished by a Domain Name Server (DNS). The IP host address identifies a specific host on an IP network. An IP address is a logical, numeric 32-bit binary number that contains two pieces of information: 1) the Network Identifier (i.e., group of computers), and 2) the Host Identifier (i.e., specific computer on the network. An IP address uses the dotted-decimal format similar to the foregoing example, where each period separates each byte of the 32-bit address: The 32-bit address is broken down into 8-bit units called octets. There are four octets in an IP address. IP addresses are usually written in the form w.x.y.z. Each number w,x,y and z is a number within the range which represents the 8 bit value for that octet. Some values, particularly for w, are reserved and can not be assigned. Network Numbers Consider an IP address of the form w.x.y.z. The value of w determines the network type of IP address. Table 7. Network ID VALUE OF W NETWORK CLASS NETWORK PORTION HOST PORTION A w x.y.z B w.x y.z C w.x.y z For example, an IP address of 34.x.y.z would be classified as a Class A address, and 221.x.y.z would be classified as a Class C address. Table 8. Network Class NETWORK CLASS AVAILABLE NETWORKS AVAILABLE HOSTS ON THE NETWORK A ,777,214 B 16,384 65,534 C 2,097, Unless you go through a gateway, you can only communicate with other devices that share your network number. Every device on an IP network must have a unique IP address. If your network is isolated, you can choose network number any way you like. If your network is connected to the Internet, you must obtain your network number from an IP addressing registrar such as Network Solutions, Inc. Network Solutions, Inc., is an organization that allocates network addresses to ensure that no two devices have the same IP addresses. Electronic Imaging Division 40 Manual

41 Subnet Masking Subnet masks are used to subdivide an IP network. Technically, a subnet mask does not mask portions of the 32-bit octets, but uses those certain portions to identify local or remote networks. There are default subnet masks for each class of networks. Table 9. Default Subnet Mask Network Class Value of w Default subnet mask A B C Typically the default subnet masks are used for a given network unless that network has been subdivided into additional networks, also know as subnetting. A non-default subnet mask can identify a subnetted network. For example, a Class B network subdivided into six subnets would now have a subnet mask of Subnetting is used to create additional subnets (i.e., networks) and hosts per network. Electronic Imaging Division 41 Manual

42 Figure 18. Network/Host ID Class A Address Network ID Host ID TOSHIBA W X Y Z Example Default Subnet Mask = Network ID = 124 Host ID = Class B Address Network ID Host ID W X Y Z Example Default Subnet Mask = Network ID = Host ID = Class C Address Network ID Host ID W X Y Z Example Default Subnet Mask = Network ID = Host ID = 85 DHCP (Dynamic Host Configuration Protocol) DHCP is a Session Layer protocol used to centralize IP address management on computers that are utilizing the DHCP server service. DHCP automatically assigns IP addresses to DHCP clients on a network. In addition, a DHCP server Electronic Imaging Division 42 Manual

43 can automatically assign other components to a network client such as a subnet mask, default gateway, DNS and WINS server address. If a LAN administrator chooses to implement a TCP/IP network, all of the client machines will require an IP address in order to access network resources. A LAN administrator may choose to manually assign an IP address to each machine or have a server (i.e., DHCP server) dynamically assign an IP address to each client machine automatically. The latter case would be the preferred method in a situation where there are numerous computers on a network. In order to utilize DHCP, a DHCP server is configured with a scope (a block or range of available IP addresses) and a machine on the network is configured as a DHCP client (recipient of a DHCP server). When the DHCP server and client are configured correctly, the client machine will log onto the network (with another protocol), and request an IP address from the DHCP server using a broadcast. The DHCP server will then issue an IP address to the client for a specified duration (i.e., lease) determined by the LAN administrator. After a four-step series of requesting, negotiating, assigning, and acknowledging, the client will obtain a valid IP address. The client will then be able to communicate over the network using TCP/IP services for the authorized lease period. Once a client machine has obtained a valid IP address from a DHCP server, the client will request a renewal of that lease in two situations; 1) every time the client logs onto the network, and 2) at one-half the duration of the lease. In both situations, the client issues a request renewal via a directed send, rather than a broadcast, since it now possesses a connection oriented protocol. Gateway Every client using an IP address on a given network requires an IP address, and a subnet mask as minimum components for the protocol to function. A gateway is used to forward IP packets from a host on one network, to a host on a different network. The gateway can be connected to multiple networks (an internetwork) and forwards the packets to the appropriate network. J. Wide Area Networks (WAN) A WAN establishes a connection between two or more remote locations over public and private data communication channels. Most WANs are a combinations of LANs and other of communications components connected by communication links called WAN links. WAN links can include the following; packet-switching networks fiber-optic cable microwave transmitters satellite links cable television coaxial cable systems Electronic Imaging Division 43 Manual

44 Communication between LANs will involve one of the following transmission technologies: analog digital packet switching Digital communications include DDS, TI/T3, and switched 56. Since DDS utilizes digital communication, it does not require modems. Instead, DDS sends data from a bridge or router through a device called a CSU/DSU (channel service unit/data service unit). This device converts the standard digital signals the computer generates into the type of digital signals (bipolar) that is part of the synchronous communications environment. T1/T3 T- Carrier services transmit computer data and multiple voice channels over digital trunk lines. The most common levels of T Carrier service are T1 and T3. A T1 line supports data transmission rates of Mbps, and a T3 line supports data transmission rates of 45 Mbps. T1/T3 lines are dedicated lines that are typically leased or switched. Packet switching The data package is broken into smaller packets and each package is tagged with a destination address and additional identifying code. The packets are relayed through stations in a computer network. The data paths for individual packets depend on the best route at any given instant and use a virtual circuit - logical connection between the sending computer and the receiving computer Switched 56 Both local and long distance telephone companies offer this LAN-to-LAN digital dial-up service that transmits data at 56 Kbps. Switched 56 is merely a circuitswitched version of a 56K bps DDS line. The advantage of switched 56 is that it is used on demand, thereby eliminating the cost of a dedicated line. Each computer using the service must be equipped with a CSU/DSU that can dial up another Switched 56 site. Copper wire will accommodate T1 and T2. However T3 requires a highfrequency medium such as microwave or fiber-optic. X.25 X.25 is a set of protocols incorporated in a packet-switching network that uses switches and circuits and routes data as available to provide the best routing at any particular time. This process uses telephone lines, and is slow due to the overhead of error checking. Electronic Imaging Division 44 Manual

45 Frame Relay Frame relay is a fast packet variable-length, digital, packet-switching technology. The process is point-to-point and uses permanent virtual circuits (PVCs) to transmit at Data Link Layer over a digital leased-line. This process requires frame-relay capable routers or bridges. ATM An ATM (Asynchronous Transfer Mode) network is set up in a star configuration using fiber-optic (and in some newer incarnations, twisted-pair) cables. Data transmits at 155 Mbps and higher. A switch at the center of the star establishes a dedicated circuit between the sending and receiving stations. ATM is ideal for video, voice and teleconferencing applications. ATM, however, requires new network adapters and, in most instances, fiber-optic cable connections. Furthermore, its implementations are limited and proprietary. Until ATM becomes more affordable and standardized, it is more cost-effective to purchase an Ethernet switch or Fast Ethernet to increase a network's bandwidth. ISDN ISDN (Integrated Services Digital Network) is an all-digital, circuit switched communications systems. There are three implementations of ISDN; Basic Rate, Primary Rate, and Broadband-ISDN. Generically, three data channels are used; 2 for 64kbps, and 1 for 16kbps. The 64kbps channels are known as B channels and carry voice, data or image, and the 6kbps channel (i.e., D channel) carries signaling and link management data. ISDN uses non-dedicated dial-up service and does not provide bandwidth on-demand as frame relay. SONET SONET is a synchronous optical network that provides greater than 1 gigabit per second transmission rate. Modems (MOdulatos/DEModulator) Modems are electronic data communication devices that enable two systems to communicate over publicly switched telephone networks. The sending end modem converts computer digital signals into analog signals that can be transmitted over the telephone lines. The receiving modem converts the analog signal back into a digital signal that the computer can understand. There are two fundamental types of modems, asynchronous, and synchronous. Asynchronous communications (Async) use common phone lines not synchronized, no clocking device approximately 56,000bps error control - a parity bit which is used in an error checking and correction scheme called parity checking Electronic Imaging Division 45 Manual

46 signaling or channel speed - how fast the bits are encoded onto the communication channel throughputs - amount of useful information going across the channel v.32bis, v.42, v.42bis Synchronous communication relies on a timing scheme coordinated between two devices to separate groups of bits and transmit them in blocks known as frames if it detects an error, re-transmits it format data into blocks add control info check the info to provide error control the primary protocols in synchronous communication are: synchronous data link control (SDLC) high-level data link control (HDLC) binary synchronous communication protocol public dial network (bisync) lines (dial-up lines) - manually dial up to make a connection leased (dedicated) lines - full time connection that do not go through a series of switches, 56kbps to 45mbps K. Network Operating Systems Microsoft/Novell Overview Microsoft Microsoft networking environments are classified into two structures; Workgroups and Domains. As previously discussed in Section II. (Networking Fundamentals A Review), Workgroups are generally referred to as Peer-to-Peer, and Domains are generally referred to as Client/Server networks. Windows NT domains require users to log on with a valid username and password. NT compares the username and password the user enters with those in the user accounts database. If the names and passwords match, Windows NT authenticates the user and logon is accomplished. Windows NT can store the user accounts database locally, on the user's computer. These locally validated accounts are called workgroup accounts, because you can use the accounts to set up multiple NT computers in a workgroup, or peer-to-peer, relationship. In this case, users log on to their workgroup computers. Alternatively, Windows NT can check usernames and passwords against an account database located on a domain controller. For Windows NT to use a domain controller, you must first implement the NT domain model. In this model, Electronic Imaging Division 46 Manual

47 Windows NT manages the accounts database from a central point, the Primary Domain Controller (PDC). In the domain model, the accounts are called domain accounts, and users log on to the domain where they may have access to domain resources. SMB (Server Message Block) SMB is a high level protocol (Application Layer) developed by Microsoft, Intel, and IBM. SMB defines a series of commands necessary to transmit information between networked computers. The SMB protocol is used in the Microsoft Windows and OS/2 NOS environments. In addition, CIFS (Common Internet File System), which allows file sharing between computers over the Internet, is based on SMB. SMB is also used in the Unix/Linux NOS environment in the form of SAMBA. SMB utilizes a redirector service that allows a client machine to locate files on other computers connected to the network using SMB (or SAMBA) and read, write, open, and execute those files. Once the redirector establishes the session, a two-way conversation occurs between the computers in which the following types of SMB messages are exchanged: Session Control Commands that start and end a redirector connection to shared resources at a server, File Messages Used by the redirector to gain access to files at a server, Printer Messages Used by the redirector to send print jobs to shared printers and capture information from print queues, and Message Messages Used to allow for the exchange of messages with other machines on the network. Novell - Introduction to NDS Novell networking environments use either Bindery or NetWare Directory Services (NDS) to organize network resources. Familiarity with NDS concepts is important when working within a Novell NetWare NDS environment. NDS is a Directory Service. A Directory Service allows you to easily manage your network resources. Simply put, the NDS Directory is a database of objects that represent network resources, such as network users, servers, printers, print queues, and applications. The NDS Directory can be described as a hierarchical tree. The NDS Directory is stored as a set of database files on a server. A NetWare server stores these files on volume SYS. If no file system volumes are present, the server stores the NDS database files in an NDS installation subdirectory. The NDS Directory can be replicated on multiple servers. Electronic Imaging Division 47 Manual

48 The NDS Tree The NDS tree can be thought of as a distributed database that contains directory information about objects. That is, the database contains objects and the attributes, or properties, which describe those objects. Each NDS tree maintains its own database of objects. Because it is a distributed database, the database is usually contained on more than one server. The information in an NDS tree does not describe the physical layout of the network. It usually describes the logical organization of the business. The NDS tree is usually organized into subtrees that reflect the different departments and units in an organization. In turn, those subtrees contain the resources within the different departments. Objects in the NDS Tree The NDS tree is made up of objects. These objects represent network entities and are of two basic types: Leaf Objects and Container Objects. In the tree representation, container objects can hold leaf objects and other container objects. Container objects are Country objects, Organization objects, or Organizational Unit objects. Leaf objects usually represent a network resource such as a user or a printer and can hold no other object. Figure 19. NDS Tree With Objects Electronic Imaging Division 48 Manual