Network management (HND in Networking)

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Network management (HND in Networking)

  1. 1. Network Management Naresh Loganathan Page 1 Table of Contents Task 01..............................................................................................3 1.1..........You are thinking about creating a network solution for a small business of approximately 15 users. You can use Wi-Fi or cable network. Describe which method you suggest? Give reasons to your answer. .....................................3 Wired or Cable Network diagram ..........................................................3 Benefits of wired connection ...............................................................3 Benefits of wireless connection ............................................................4 Legacy infrastructure and mixed environments .........................................5 WLAN vs LAN ..................................................................................5 LAN and WLAN Security ....................................................................6 LAN and WLAN Availability .................................................................6 Wired vs Wireless.............................................................................7 Task 1.2 .............................................................................................8 What are the required devices to setup the network in Task 1.1? Describe the security methods you applied, performance and cost to establish the network....8 WIRELESS ROUTER............................................................................8 Wireless Router Functions...................................................................8 NETWORK INTERFACE CARD.................................................................9 Network Interface Card Functions .........................................................9 ETHERNET CABLE ........................................................................... 10 Task 1.3 ........................................................................................... 11 Describe what Network Operating System (NOS) is and what are the additional features available compared to client Operating System (OS). ..................... 11 NOS REMOTE LOGIN ........................................................................ 12 Task 02............................................................................................ 13 Task 2.1 ........................................................................................... 13 The 7 layer network management model and list Protocols and a device operates on layers of the 7 layer model. .......................................................... 13 OSI 7 Layers Reference Model For Network Communication......................... 13 Characteristics of Layered Protocols: ................................................... 14 Layer 7 Application layer.................................................................. 15 Layer 6 Presentation Layer ............................................................... 17 Layer 5 Session layer....................................................................... 18
  2. 2. Network Management Naresh Loganathan Page 2 Layer 4 Transport layer.................................................................... 19 Layer 3 Network layer ..................................................................... 21 Layer 2 Data link layer..................................................................... 23 Layer 1 Physical layer...................................................................... 24 Task 2.2 ........................................................................................... 26 Briefly explain the peer to Peer network (Workgroup) model and Client Server network (Domain) model. ................................................................. 26 Peer-to-peer network...................................................................... 26 Client/ server network .................................................................... 27 Task 03............................................................................................ 32 Task 3.1 ........................................................................................... 32 Design a total network solution for a company which has around 25 computers and have 2 servers respectively one for web server and the other one for file sharing propose and Internet connectivity. This design must reflect a high availability on all aspect of the networking starting from LAN to WAN. ........... 32 Task 3.2 ........................................................................................... 33 Compare and contrast OSI and TCP/IP proposed network management standards ................................................................................................ 33 Distinguishing Points ....................................................................... 33 TCP/IP Model................................................................................ 34 OSI Model .................................................................................... 35 Task 3.3 ........................................................................................... 37 Describe the responsibilities of Network Administrator. ............................. 37 Equipment upgrades ....................................................................... 37 Configuration................................................................................ 37 Software upgrades ......................................................................... 38 Patches....................................................................................... 38 Performance maintenance ................................................................ 38 Ho-hum chores.............................................................................. 38 Software inventory......................................................................... 38 Designing the Network..................................................................... 39 Setting Up the Network.................................................................... 39 Maintaining the Network .................................................................. 39 Expanding the Network.................................................................... 39
  3. 3. Network Management Naresh Loganathan Page 3 Task 01 1.1 You are thinking about creating a network solution for a small business of approximately 15 users. You can use Wi-Fi or cable network. Describe which method you suggest? Give reasons to your answer. This task provides evidence for P14.1.1 Wired or Cable Network diagram Benefits of wired connection It is easy enough to see why enterprises want to remain wired – control and security, reliability and speed are the primary benefits of using physical connections. It is also relatively cost- effective, as the price of cabling – even at the lengths needed to cover an average office – is pretty cheap. One great advantage of having a wired infrastructure, which seems particularly relevant in today’s mobile world, is the control it provides. If a physical connection is needed to access the corporate network, the business is in full control of who and what gets online. While this has
  4. 4. Network Management Naresh Loganathan Page 4 obvious security benefits of keeping unauthorized visitors out of your network, it also means your network will not be overloaded with non-business critical traffic. Wireless or Wi-fi Network Diagram Benefits of wireless connection While a physical infrastructure may be good from a management point of view and offer cheap deployment, having all those wires running throughout a building can be costly and awkward to maintain. For example, if a business increases its workforce, all those new workers will need physical connections at their desk – connections that will need to be manually set up. Any breakages in the wired connection will also have to be manually fixed as there is no software solution to a broken Ethernet pin.
  5. 5. Network Management Naresh Loganathan Page 5 With the explosion in mobile devices over the last few years – Apple alone has sold around 100 million iPads since the tablet was introduced in 2010 – many workers are bringing their own devices into the office. It is vital these employees have access to the corporate network to get the most out of them, and that means giving them wireless access. As well as being able to use their own devices, wireless infrastructure means freedom to move around the office, from desk to desk or meeting room to meeting room. According to the above scenario I like to suggest use both Network method. Legacy infrastructure and mixed environments There are pros and cons to having a wireless and a wired enterprise and it is fair to say that wireless becoming the norm is still some way off. For example, there is too much legacy infrastructure in place to rip it out and replace it with a wireless set up. A combination of wired and wireless is the way forward, at least for now. That way a business can satisfy the needs of its mobile workers and ensure all security, control and reliability requirements are met. Having a mixed environment does not need to mean a nightmare from a management point of view. Cisco, for example, recently unveiled its new Unified Access platform, which brings together wired and wireless connections in one switch. The 5760 Unified Access WLAN controller enables wireless connections to be managed on top of existing wired infrastructure. Juniper Networks also integrates wireless LANs with existing wired infrastructure, giving businesses the best of both worlds. Managing both together means businesses can run the same policies across the wired and wireless infrastructure, meaning business will see the benefit of having both while, hopefully, reducing the negatives associated with either installation. WLAN vs LAN LAN stands for Local Area Network, which is a collection of computers and other network devices in a certain location that are connected together by switches and/or routers that facilitate the communication of the network elements. Each computer or network element is connected to the switches/routers via a UTP cable. The added letter in WLAN stands for wireless. This is a type of network where the data is not transmitted via cables but over the air through the use of wireless transmitters and receivers. WLANs are deployed in areas where a wide number of computers may connect to the network but not at the same time. Places like coffee shops often add WLAN to their shops to entice more customers who do not stay for extended periods. Even at home where you have a somewhat fixed number of computers that connect to the network, WLAN is also preferred as it gives users the freedom to move around the house and carry their laptops with them without needing to fuss with cables. For areas where the computers are pretty much fixed, a wired LAN is very desirable due to the advantages that it offers.
  6. 6. Network Management Naresh Loganathan Page 6 First off, a wired LAN is much faster compared to a WLAN. Most wireless routers nowadays are limited to a theoretical maximum speed of 54mbps while a contemporary wired LAN has a bandwidth of 100mbps. Gigabit network equipment can even ramp this up to 1000mbps or 1Gbps. This might not be such a big issue for browsing the internet or sending email but when you are copying large files, it can take a while with a WLAN. WLANs are also vulnerable to attack as just about anyone with a strong enough transceiver is able to detect the signal. Access can then be achieved by breaking the encryption used by the router through certain software. The information that is being transmitted through the WLAN can also be collected by malicious person and used in a variety, often destructive, ways. In order to intercept data in a wired LAN, you need to physically connect to a switch or a router. LAN and WLAN Security In theory, wireless LANs are less secure than wired LANs, because wireless communication signals travel through the air and can easily be intercepted. To prove their point, some engineers have promoted the practice of wardriving, that involves traveling through a residential area with Wi-Fi equipment scanning the airwaves for unprotected WLANs. On balance, though, the weaknesses of wireless security are more theoretical than practical. WLANs protect their data through the Wired Equivalent Privacy (WEP) encryption standard that makes wireless communications reasonably as safe as wired ones in homes. No computer network is completely secure and homeowners should research this topic to ensure they are aware of and comfortable with the risks. Important security considerations for homeowners tend to not be related to whether the network is wired or wireless but rather ensuring: the home's Internet firewall is properly configured the family is familiar with the danger of Internet "spoof emails" and how to recognize them the family is familiar with the concept of "spyware" and how to avoid it babysitters, housekeepers and other visitors do not have unwanted access to the network LAN and WLAN Cost Wireless gear costs somewhat more than the equivalent wired Ethernet products. At full retail prices, wireless adapters and access points may cost three or four times as much as Ethernet cable adapters and hubs/switches, respectively. 802.11b products have dropped in price considerably with the release of 802.11g, and obviously, bargain sales can be found if shoppers are persistent. LAN and WLAN Availability Wireless LANs suffer a few more reliability problems than wired LANs, though perhaps not enough to be a significant concern. 802.11b and 802.11g wireless signals are subject to interference from other home appliances including microwave ovens, cordless telephones, and garage door openers. With careful installation, the likelihood of interference can be minimized.
  7. 7. Network Management Naresh Loganathan Page 7 Wireless networking products, particularly those that implement 802.11g, are comparatively new. As with any new technology, expect it will take time for these products to mature. Wired vs Wireless Wired Wireless Installation moderate difficulty easier, but beware interference Cost less more Reliability high reasonably high Performance very good good Security reasonably good reasonably good Mobility limited Outstanding
  8. 8. Network Management Naresh Loganathan Page 8 Task 1.2 What are the required devices to setup the network in Task 1.1? Describe the security methods you applied, performance and cost to establish the network. This task provides evidence for P14.1.2 WIRELESS ROUTER A wireless router is a device in a wireless local area network (WLAN) that determines the next network point to which a packet should be forwarded toward its destination. A wireless router works in the same way as the router in a hard-wired home or business local area network (LAN), but allows greater mobility for notebook or portable computers. The individual computers are equipped with small wireless transceivers that can be plugged into either a Universal Serial Bus (USB) port or a PC card slot. For home and business computer users who have high-speed Internet connections, a wireless router can also act as a hardware firewall. This is true even if the home or business has only one computer. Many engineers believe that the use of a router provides superior protection against hacking because individual computer IP addresses are not directly exposed to the Internet. A wireless router also does not consume computer resources as a firewall program does. Wireless Router Functions In technical terms, router, be it wired or wireless, functions like a layer 3 gateway i.e. that it connects various networks and then it operates at the network layer of the OSI model. Wireless routers operate either in wired Local Area Network (LAN), wireless LAN or a network which is a mixture of wired and wireless. Most of the wireless routers have features like LAN ports, Wide Area Network (WAN) ports, which is used in connecting to a wider area network, and wireless antennae, which helps in connecting with wireless devices like wireless access points, wireless repeaters and wireless bridges. Wireless router is used by wireless devices as their hub while mini-LAN, which is present in the router, is connected as a single device to the remaining LAN. Wireless routers can function both in a point-to-point mode and point-to-multipoint mode. Wireless devices must be set to the same service set identifier and radio channel to which the wireless router is connected.
  9. 9. Network Management Naresh Loganathan Page 9 NETWORK INTERFACE CARD A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring. Network interface cards provide a dedicated, full-time connection to a network. Most home and portable computers connect to the Internet through as-needed dial-up connection. The modem provides the connection interface to the Internet service provider. Network Interface Card Functions The purpose of a LAN Card is to create a physical connection to the network; to provide an open 'door', as it were. The first interface supported by a LAN Card is a physical interface of how the cable plugs into the card. This interface is well defined in technical documentation, which is why standard network cables fit most standard LAN cards. The second function of a LAN Card is to provide a data link. There is a theoretical model in computer networking called OSI - Open Systems Interconnection. This model, or a way of explaining networks, includes 7 layers. The first two layers are the physical layer and data link. Each layer of the OSI model allows for other layers to be independent. Upgrading or changing one layer does not affect others. This means that if plugins change for all LAN cards, other elements like the protocols don't have to change. The data link function of a LAN Card provides hardware-level sending and receiving of network binary data. Zeros and ones flow from the network into the network card. The card can recognize this flow and it can even check for errors. When you turn on a computer with a LAN Card, it will have two lights, one green and one orange. The orange light will come on when the data link layer is activated. This means that the cable works, there is a network connected, and data bits are flowing. The second light, the green light, comes on once the next layer the network layer is activated (such as an IP network).
  10. 10. Network Management Naresh Loganathan Page 10 ETHERNET CABLE Ethernet is a physical and data link layer technology for local. Ethernet was invented by engineer Robert Metcalfe. When first widely deployed in the 1980s, Ethernet supported a maximum theoretical data rate of 10 megabits per second (Mbps). Later, so-called "Fast Ethernet" standards increased this maximum data rate to 100 Mbps. Today, Gigabit Ethernet technology further extends peak performance up to 1000 Mbps. Higher level network protocols like Internet Protocol (IP) use Ethernet as their transmission medium. Data travels over Ethernet inside protocol units called frames. The run length of individual Ethernet cables is limited to roughly 100 meters, but Ethernet networks can be easily extended to link entire schools or office buildings using network bridge devices.
  11. 11. Network Management Naresh Loganathan Page 11 Task 1.3 Describe what Network Operating System (NOS) is and what are the additional features available compared to client Operating System (OS). This task provides evidence for P14.1.2 Initially, computers were built to operate as a singular entity; having discrete resources and individual operating system. Although the use of multiple computers to solve a single problem is not unheard of, it is often a human’s job to subdivide the problem into manageable chunks that the computers can separately work on. A distributed OS is just an improvement of the original concept. But instead of a human cutting up the job, the OS is smart enough to know which computers are overloaded and which ones are idle. It would then balance the tasks available so that each computer in the group is sharing equal load. This is good for maximizing the usefulness of each computer. The drawback though is that you would need to upgrade all the units every so often to maintain a reasonable level of performance. There is also some software that is simply not compatible with distributed computing. They are not optimized to take advantage of multiple processes, and as such can only be processed by one computer. The appearance of network operating systems is a direct result of the need to cut costs and control each computer in the system. Network OS does not reside on every computer, the client only has enough software to boot the hardware and contact the server. All the subsequent operations are done on the server, and the only role of the client is to relay the input and output between the server and the user. This is very effective in controlling the installed software since clients do not have the capability to add or remove software. A network OS requires a very minimal amount of hardware on the client, although the server should be capable to handle the demands of multiple users. This means that you would not need to upgrade the clients as long as you keep the server properly maintained. This even led to the creation of thin clients or devices that cannot function on their own but are meant to work with network OS. Depending on the needs and resources of your company, a distributed or network OS might be worth looking into. Each has its own advantages and disadvantages that you should take into consideration. A distributed OS could cost a bit more than a network OS, but a network OS cannot handle computation intensive programs due to the stress it puts in the server. The decision is up to you in picking a better solution that what you currently have.
  12. 12. Network Management Naresh Loganathan Page 12 NOS REMOTE LOGIN Each user uses its own operating system. When a user wants to access any other machine, he must require some kind of remote login to access the other machine. The user knows the location of the files on their own systems, and they use file transfer commands to transfer these files from one machine to another. Let's have a look at advantages and disadvantages of Network operating system; Advantages Servers are highly stable. Security is managed by server. Up gradation of system is easy. Remote access to server is possible. Disadvantages High Cost. Great dependency on server. Regular maintenance is required. Network Operating System Operating System Control over file placement is done by user. Control over file placement is done by system itself. Various machines are included and each machine has its own user IDs. Various machines are included and there is single system wide mapping. Each computer system schedules and run its own processes. A single process running on one machine may have its sub-processes running on other machines. Follows two-tier client server architecture. Follows n-tier client server architecture. Huge dependency on server. No dependency on any machine. Medium Processing speed. Fast processing.
  13. 13. Network Management Naresh Loganathan Page 13 Task 02 Task 2.1 The 7 layer network management model and list Protocols and a device operates on layers of the 7 layer model. This task provides evidence for P14.2.1 OSI 7 Layers Reference Model For Network Communication Open Systems Interconnection (OSI) model is a reference model developed by ISO (International Organization for Standardization) in 1984, as a conceptual framework of standards for communication in the network across different equipment and applications by different vendors. It is now considered the primary architectural model for inter-computing and internetworking communications. Most of the network communication protocols used today have a structure based on the OSI model. The OSI model defines the communications process into 7 layers, which divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers. Each layer is reasonably self-contained so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers. The OSI 7 layers model has clear characteristics. Layers 7 through 4 deal with end to end communications between data source and destinations. Layers 3 to 1 deal with communications between network devices. On the other hand, the seven layers of the OSI model can be divided into two groups: upper layers (layers 7, 6 & 5) and lower layers (layers 4, 3, 2, 1). The upper layers of the OSI model deal with application issues and generally are implemented only in software. The highest layer, the application layer, is closest to the end user. The lower layers of the OSI model handle data transport issues. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the wires, for example) and is responsible for placing data on the medium.
  14. 14. Network Management Naresh Loganathan Page 14 Characteristics of Layered Protocols: Above Figure shows Headers and the OSI protocol layers. When a device transmits data to the network, each protocol layer processes the data in turn. Consider the network layer for the sending device. Data to be transmitted is received from the transport layer. The network layer is responsible for routing and must add its routing information to the data. The network layer information is added in the form of a header, which is appended to the beginning of the data. The term Protocol Data Unit (PDU) is used to describe the combination of the control information for a layer with the data from the next higher layer. Each layer appends a header to the PDU that the next higher layer receives. The data field for each layer consists of the PDU for the next higher layer. The physical layer does not encapsulate in this manner because the physical layer manages data in bit form.
  15. 15. Network Management Naresh Loganathan Page 15 07. Application layer 06. Presentation layer 05. Session layer 04. Transport layer 03. Network layer 02. Data link layer 01. Physical layer Layer 7Application layer Application layer is the level of the protocol hierarchy where user-accessed network processes reside. An TCP/IP application is any network process that occurs above the transport layer. This include all the processes that the users directly interact with, as well as other processes at this level that users are not necessarily aware of. The Application Layer provides the services user applications needed to communicate through the network. Here are several examples of user application layer services: • Electronic mail transport. • Remote file access. • Remote job execution. • Directories. • Network management. Application Layer Protocol Functions Application layer ISO OSI protocols are used by both the source and destination devices during a communication session. In order for the communications to be successful, the application layer protocols implemented on the source and destination host must match. Protocols establish consistent rules for exchanging data between applications and services loaded on the participating devices. Protocols specify how data inside the messages is structured and the types of messages that are sent between source and destination. These messages can be requests for services, acknowledgments, data messages, status messages, or error messages. Protocols also define message dialogues, ensuring that a message being sent is met by the expected response and the correct services are invoked when data transfer occurs. Many different types of applications communicate across data networks. Therefore, Application layer services must implement multiple protocols to provide the desired range of communication experiences. Each protocol has a specific purpose and contains the characteristics required to meet that purpose. The right protocol details in each layer must be followed so that the functions at one layer interface properly with the services in the lower layer. Applications and services may also use multiple protocols in the course of a single conversation. One protocol may specify how to establish the network connection and another describe the process for the data transfer when the message is passed to the next lower layer.
  16. 16. Network Management Naresh Loganathan Page 16 Ap plication Layer Services and Protocols A single application may employ many different supporting Application layer services; thus what appears to the user as one request for a web page may, in fact, amount to dozens of individual requests. And for each request, multiple processes may be executed. For example, a client may require several individual processes to formulate just one request to a server. Additionally, servers typically have multiple clients requesting information at the same time. For example, a Telnet server may have many clients requesting connections to it. These individual client requests must be handled simultaneously and separately for the network to succeed. The Application layer processes and services rely on support from lower layer functions to successfully manage the multiple conversations. Protocols: FTP1 , HTTP2 , SMTP3 , DNS4 , TFTP5 , NFS6 , TELNET7 Application layer network devices When most people think of Application Layer protocols like HTTP, SMTP, or POP3, they also think of software applications which are the interface for these applications. But this is not always the case. With a little thought we can easily think of examples where the interface for the applications are hardware implementations. For example, take many of today's cordless phones which are capable of connecting to one's VoIP account. Now while there is software on these phones it is easy to imagine that the majority of the work is done by hardware. In fact, your voice is collected by a microphone and hardware processes it so that it is compatible with the proprietary VoIP application protocol by hardware inside the phone. This hardware can be either an Application Specific Integrated Circuit (ASIC) or a Field Programmable Gate Array (FPGA). Another example of a hardware implementation of an Application Layer protocol is found within Bluetooth. Bluetooth, in its entirety, covers many layers of the OSI Reference Model but we will focus on the application layer implementation. Within Bluetooth devices you can find many applications falling within the Application Layer. One such application is one which would allow a wireless ear piece, like the one shown in Figure 1, to communicate with a cell phone in your pocket. In this case, the ear piece, which has a Bluetooth chip inside, will convert the signal it receives from the phone to a form acceptable to the speaker completely through hardware. Likewise, the ear piece will receive a signal of your voice from the microphone and convert it to a form acceptable to the Bluetooth chip which will then send the signal to your phone. This is all done through hardware.
  17. 17. Network Management Naresh Loganathan Page 17 Layer 6 Presentation Layer The presentation layer is layer 6 of the 7-layer Open Systems Interconnection (OSI) model. It is used to present data to the application layer (layer 7) in an accurate, well-defined and standardized format. The presentation layer is sometimes called the syntax layer. The presentation layer is responsible for the following: Data encryption/decryption Character/string conversion Data compression Graphic handling The presentation layer mainly translates data between the application layer and the network format. Data can be communicated in different formats via different sources. Thus, the presentation layer is responsible for integrating all formats into a standard format for efficient and effective communication. The presentation layer follows data programming structure schemes developed for different languages and provides the real-time syntax required for communication between two objects such as layers, systems or networks. The data format should be acceptable by the next layers; otherwise, the presentation layer may not perform correctly. Network devices or components used by the presentation layer include redirectors and gateways. Presentation layer protocols The OSI presentation layer protocol (ISO-PP) is for the information transit between open systems using connection oriented or connectionless mode transmission at the presentation layer of the OSI 7 layer model. An application protocol is specified in terms of the transfer of presentation data values between application entities (PS users), using the User data parameter of presentation service primitives. The Presentation Layer has two functions it carries out on behalf of PS users: negotiation of transfer syntaxes transformation to and from transfer syntax. The function of transfer syntax negotiation is supported by presentation protocols. Transformation of syntax is a function contained within a presentation entity and has no impact
  18. 18. Network Management Naresh Loganathan Page 18 on presentation protocol design. For connectionless mode transmission, the sending presentation entity selects the transfer syntaxes. No transfer syntax negotiation occurs. A set of presentation data value definitions associated with an application protocol constitutes an abstract syntax. For two application entities to communicate successfully they must have an agreement on the set of abstract syntaxes they intend to use. During the course of communication they may decide to modify this agreement. As a consequence, the set of abstract syntaxes in use may be changed. The abstract syntax specification identifies the information content of the set of presentation data values. It does not identify the transfer syntax to be used while presentation data values are transferred between presentation entities, nor is it concerned with the local representation of presentation data values. The Presentation Layer exists to ensure that the information content of presentation data values is preserved during transfer. It is the responsibility of cooperating application entities to determine the set of abstract syntaxes they employ in their communication and inform the presentation entities of this agreement. Knowing the set of abstract syntaxes to be used by the application entities, the presentation entities are responsible for selecting mutually acceptable transfer syntaxes that preserve the information content of presentation data values. Protocols: ASCII8 , EBCDIC9 , MIDI10 , MPEG11 , JPEG12 Presentation layer network devices The Presentation Layer is responsible for converting the data sent over the network from one type of representation to another. For example, the Presentation Layer can apply sophisticated compression techniques so fewer bytes of data are required to represent the information when it's sent over the network. At the other end of the transmission, the Transport Layer then uncompressed the data. The Presentation Layer also can scramble the data before it's transmitted and then unscramble it at the other end, using a sophisticated encryption technique. Layer 5 Session layer In the Open Systems Interconnection (OSI) communications model, the Session layer (sometimes called the "port layer") manages the setting up and taking down of the association between two communicating end points that is called a connection. A connection is maintained while the two end points are communicating back and forth in a conversation or session of some duration. Some connections and sessions last only long enough to send a message in one direction. However, other sessions may last longer, usually with one or both of the communicating parties able to terminate it. For Internet applications, each session is related to a particular port, a number that is associated with a particular upper layer application. For example, the HTTP program or daemon always has port number 80. The port numbers associated with the main Internet applications are referred to as well-known port numbers. Most port numbers, however, are available for dynamic assignment to other applications.
  19. 19. Network Management Naresh Loganathan Page 19 Session layer protocols The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs).An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.235 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. If a connection is not used for a long period, the session-layer protocol may close it and re-open it. It provides for either full duplex or half-duplex operation and provides synchronization points in the stream of exchanged messages.Other examples of session layer implementations include Zone Information Protocol (ZIP) – the AppleTalkprotocol that coordinates the name binding process, and Session Control Protocol (SCP) – the DECnet Phase IV session-layer protocol.Within the service layering semantics of the OSI network architecture, the session layer responds to service requests from the presentation layer and issues service requests to the transport layer. Protocols: SQL13 , RPC14 Session layer network devices According to the OSI Model, the session layer is where connections are established, managed, and torn down. For connection-oriented network protocols, understanding how the session layer works, and what symptoms would help you identify when it's not working, is an important part of your job as a network administrator. However, because TCP doesn't respect the OSI model, we have to sort of carve TCP/IP out of this conversation, which really limits its practical application in most environments. When you think about session-oriented communications vs. connectionless conversations, you might compare them to a telephone conversation vs. using a walkie-talkie. With a telephone, you call the person who you want to talk to, establish a connection -- or session -- and then you hang up, severing the connection once the conversation is completed. With a walkie-talkie, you simply speak into the device and hope that the person on the other end is listening and that they respond in kind. There's no session established. Two session-oriented protocols that you are still likely to see on production networks are Netbios and RPC. These protocols are commonly used within Microsoft-based LAN environments. However, problems with these protocols are seldom seen and when they are, since they're used on the LAN, it's unlikely that the problem is network related. More likely, it's an application problem. Layer 4 Transport layer The transport layer is the layer in the open system interconnection (OSI) model responsible for end-to-end communication over a network. It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components.
  20. 20. Network Management Naresh Loganathan Page 20 The transport layer is also responsible for the management of error correction, providing quality and reliability to the end user. This layer enables the host to send and receive error corrected data, packets or messages over a network and is the network component that allows multiplexing. As the transport layer is built on top of the network layer, it is important to know the key features of the network layer service. There are two types of network layer services: connectionless and connection-oriented. The connectionless network layer service is the most widespread. Transport layer protocols This chapter provides an overview of the most important and common protocols of the TCP/IP transport layer. These include: I. User Datagram Protocol (UDP) II. Transmission Control Protocol (TCP) By building on the functionality provided by the Internet Protocol (IP), the transport protocols deliver data to applications executing in the IP host. This is done by making use of ports. The transport protocols can provide additional functionality such as congestion control, reliable data delivery, duplicate data suppression, and flow control as is done by TCP. I. User Datagram Protocol (UDP) UDP is a standard protocol with STD number 6. UDP is described by RFC 768 – User Datagram Protocol. Its status is recommended, but in practice every TCP/IP implementation that is not used exclusively for routing will include UDP. UDP is basically an application interface to IP. It adds no reliability, flow-control, or error recovery to IP. It simply serves as a multiplexer/demultiplexer for sending and receiving datagrams, using ports to direct the datagrams. Demultiplexing based on ports UDP provides a mechanism for one application to send a datagram to another. The UDP layer can be regarded as being extremely thin and consequently has low overheads, but it requires the application to take responsibility for error recovery and so on. II. Transmission Control Protocol (TCP) TCP is a standard protocol with STD number 7. TCP is described by RFC 793 – Transmission Control Protocol. Its status is recommended, but in practice, every TCP/IP implementation that is not used exclusively for routing will include TCP. TCP provides considerably more facilities for applications than UDP, notably error recovery, flow control, and reliability. TCP is a connection-oriented protocol, unlike UDP, which is connectionless. Most of the user application protocols, such as Telnet and FTP, use TCP. The two processes communicate with each other over a TCP connection. Protocols: TCP15 or UDP16
  21. 21. Network Management Naresh Loganathan Page 21 Transport layer network devices The device will maintain a routing table whose size is dependent on thesize of the WAN and the device will ensure that overall security of thenetwork is maintained. This can be implemented by making the device support V-WAN. Bysupporting V-WAN the device can also work on the security function of aswitch, with regard to each router and the network below each router. The device will update its routing table automatically. This means that it will maintain a database of the routers connected to it. This will be updatedat stipulated time interval . This ensures that it is well aware of thenetworks connected to it and indirectly the hosts present in each network. Layer 3 Network layer The most significant protocol at layer 3 (also called the network layer) is the Internet Protocol, or IP. IP is the standard for routing packets across interconnected networks--hence, the name internet. It is an encapsulating protocol similar to the way Ethernet is an encapsulating protocol. If we view the original check as a unit of data needed to be sent, we now have two envelopes required to do the transmission--the check first goes into an IP envelope, and then the entire IP envelope (known as a packet) is placed into an Ethernet frame. The format of an IP packet is documented in RFC 791. The most significant aspect of the IP protocol is the addressing: every IP packet includes the IP source address (where the packet is coming from) and the IP destination address. Network layer protocols Among the seven layers in the OSI reference model, layer 3 belongs to the network layer. There are some important network layer protocols that you should know of. Protocol is nothing but a set of rules that determine how messages are being exchanged between different computers. Let us now briefly consider five important protocols that are related to the network layer message transfers. They are:. Protocols: IPv4, IPv6, CLNP, IPSec, and ICMP IPv4: IP stands for Internet Protocol while v4 indicates that it is the version 4. Here, version 4 refers to the fourth revision of the Internet Protocol that was later widely deployed. There exists an IPv4 header structure that is the basis for network layer transfer of packets. This is one of the most important network layer protocols. IPv6: This is also an Internet Protocol that is of version 6. Though IPv4 is widely used these days, it is expected that this IPv6 is going to take over the rest of the attention. Hence, it is called the next generation protocol. There are just a few basic differences between both the protocols. The address space of IPv6 is larger than that of the IPv4.
  22. 22. Network Management Naresh Loganathan Page 22 CLNP: CLNP stands for Connectionless Network Protocol. The service that this protocol renders is called CLNS. This routes the messages to their destination independently. IPSec: Internet Protocol Security is one such protocol that enables encryption and also authentication of every IP packet that moves in the data stream. Encryption and authentication are two techniques to ensure secure message transfer from the source to the destination. ICMP: ICMP stands for Internet Control Message Protocol. This particular protocol is very important among all the network layer protocols. This is used by the operating systems of network computers to send error messages indicating that a particular service was not available or the connection to a router failed, etc. Network layer network devices The network layer does not care much about the type of data it is moving, the path it takes, or the different media that it moves over. Typically, you are allowed to change physical media types at this layer. To connect different network types, you need an interconnection device that supports data links for different network types. Such a device includes different media connections on either side and, like the router in the following figure, can connect gigabit Ethernet on one side of the device to something foreign, such as Token Ring, on the other side. Just as the data link layer has addresses that it uses to identify other devices with which your computer communicates, these are hard to understand addresses and they are only valid for the current network segments (the area between two routers). This area between routers is also referred to as a data link because it is the only place where the local devices can communicate with each other, using MAC addresses (or data link layer addresses). The network layer of the OSI model also uses addresses, but these are network layer addresses and their specific format is based on the network layer protocol being used. Internet Protocol (IP) represents a common network layer protocol. At the network layer, IP uses IP addresses to determine which two devices are communicating. The relationship between the network layer and the data link layer is that all communication over a data link will always be performed using data link (MAC) addresses, so as the network layer sends data down to the data link layer, it must also tell the data link layer what the destination MAC address is for this data.
  23. 23. Network Management Naresh Loganathan Page 23 Layer 2 Data link layer Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Physical addressing, is not to be confused with network or IP addressing. The physical address defines how devices are labeled in the data link layer. This physical address is most commonly called the Media Access Control (MAC) address. The MAC address is a unique number assigned by the manufacturer. This numbering system is actually administered by one of the networking governing bodies. Network topology consists of the data-link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time. Switches and bridges use MAC addressing to make networking decisions and therefore these types of equipment function on the data link layer. Data link layer protocols The basic function of the layer is to transmit frames over a physical communication link. Transmission may be half duplex or full duplex. To ensure that frames are delivered free of errors to the destination station (IMP) a number of requirements are placed on a data link protocol. The protocol (control mechanism) should be capable of performing: I. The identification of a frame (i.e. recognise the first and last bits of a frame). II. The transmission of frames of any length up to a given maximum. Any bit pattern is permitted in a frame. III. The detection of transmission errors. IV. The retransmission of frames which were damaged by errors. V. The assurance that no frames were lost. VI. In a multidrop configurationSome mechanism must be used for preventing conflicts caused by simultaneous transmission by many stations. VII. The detection of failure or abnormal situations for control and monitoring purposes. It should be noted that as far as layer 2 is concerned a host message is pure data, every single bit of which is to be delivered to the other host. The frame header pertains to layer 2 and is never given to the host. Protocols: IEEE 802.222 , 802.323 , 802.524
  24. 24. Network Management Naresh Loganathan Page 24 Data link layer network devices The Data Link Layer is concerned with local delivery of frames between devices on the same LAN. Data Link frames, as these protocol data units are called, do not cross the boundaries of a local network. Inter-network routing and global addressing are higher layer functions, allowing Data Link protocols to focus on local delivery, addressing, and media arbitration. In this way, the Data Link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between parties contending for access to a medium. When devices attempt to use a medium simultaneously, frame collisions occur. Data Link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them. Delivery of frames by layer 2 devices is affected through the use of unambiguous hardware addresses. A frame's header contains source and destination addresses that indicate which device originated the frame and which device is expected to receive and process it. In contrast to the hierarchical and routable addresses of the network layer, layer 2 addresses are flat, meaning that no part of the address can be used to identify the logical or physical group to which the address belongs. Layer 1 Physical layer The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer. The implementation of this layer is often termed PHY. The Physical Layer consists of the basic hardware transmission technologies of a network. It is a fundamental layer underlying the logical data structures of the higher level functions in a network. Due to the plethora of available hardware technologies with widely varying characteristics, this is perhaps the most complex layer in the OSI architecture. The Physical Layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. The bit stream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a hardware transmission medium. The Physical Layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, the modulation scheme to use and similar low-level parameters, are specified here. Within the semantics of the OSI network architecture, the Physical Layer translates logical communications requests from the Data Link Layer into hardware-specific operations to affect transmission or reception of electronic signals.
  25. 25. Network Management Naresh Loganathan Page 25 Physical layer protocols CSMA/CD - Carrier Sense Multiple Access / Collision Detect CSMA/CA - Carrier Sense Multiple Access / Collision Avoid FDMA - Frequency Division Multiple Access MSK - Minimum Shift Keying GFMSK - Gaussian-Fitered Minimum Shift Keying TDMA - Time Division Multiple Access CDMA - Code Division Multiple Access B8ZS - Binary 8 Zero Substitution 2B1Q - 2 Binary 1 Quaternary PCM - Pulse Code Modulation QAM - Quadrature Amplitude Modulation PSK - Phase Shift Keying SONET - Synchronous Optical NETworking Protocols: IEEE 802.323 , 802.524 Physical layer network devices I. Cables II. Connectors III. Repeaters IV. Passive Hub V. Simple Active Hub VI. Transmitters VII. Multiplexers VIII. Receivers IX. Transceivers X. Couplers
  26. 26. Network Management Naresh Loganathan Page 26 Task 2.2 Briefly explain the peer to Peer network (Workgroup) model and Client Server network (Domain) model. This task provides evidence for P14.2.2 Peer-to-peer network In a peer-to-peer network, there are no specific servers, and there is no hierarchy among the computers. All the computers are equal and therefore are known as peers. Each computer functions as both a client and a server.And there is no administrator responsible for the entire network. The user at each computer determines what data on that computer is shared on the network. Computers in a peer-to-peer network are called peers. In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network. Each computer can function both as a client and a server. Computers are not dedicated to function as servers. They use the network to share resources among the independent peers. The computer whose applications are required by the other networked computers functions as a server. The other computers function as clients. Therefore, a dedicated administrator is not assigned for network management. A peer-to-peer network is a small group of people using a network. Peer-to-peer networks members usually perform similar tasks, which necessitates the sharing of resources. The peer- to-peer networks support 10 computers. The users in a peer-to-peer network are located in the same geographical area. Operating systems, such as Microsoft Windows 98 or Microsoft Windows XP, can be used to set up a peer-to-peer network. Additional software is not required because peer-to-peer networking is built into the systems. Another important point of peer-to-peer networks is that the users of each computer plan and control the security of their resources. The users determine the resources on their computers, which can be shared on the network. The shared network resources, such as disk space, printers or faxes, can be used by anyone who has access to the network. This is possible only if the shared network resources are not password protected. Peer-to-peer networks have weak and intrusive security because a central server is not used to administer and secure the network. In addition, some users may not implement security. A peer-to-peer network does not support a central login process. This implies that a user who logs on to one peer can access any shared network resource, which is not controlled by a specific password. Peer-to-peer networks are relatively simple. Because each computer functions as a client and a server, there is no need for a powerful central server or for the other components required for a high-capacity network. Peer-to-peer networks can be less expensive than server-based networks. Peer-to-peer networks are simple and inexpensive to install and maintain. The cost of implementing peer-to-peer networks is low because a central server is not used to administer the network. In addition, the components for a high-capacity network are not required in a peer- to-peer network.
  27. 27. Network Management Naresh Loganathan Page 27 In a peer-to-peer network, the users handle administration. This means that all the users need to be trained in how to share files, folders, and printers. In a peer-to-peer network, suddenly shutting down your computer can cause one of your colleagues to be unable to print. Peer-to-peer networks are appropriate for environments where all the users are located in the same geographical area and the network security is not an important factor. In addition, these networks are useful when the network expansion is limited. Advantages of a peer-to-peer network Less initial expense. Setup - An operating system (such as Windows XP) already in place may only need to be reconfigured for peer-to-peer operations. Disadvantages of a peer-to-peer network Decentralized - No Centralized server. Security - Does not provide the security available on a peer-to-peer network. Client/ server network In a server-based network, clients rely on the services that the server provides, such as file storing and printing. Client computers are generally less powerful than server computers. A server-based network using network operating system is that the networks are organized into domains. A domain is a collection of networks and clients that share security information. Domain security and logon permissions are controlled by special servers called domain controllers. Users cannot access the resources of servers in a domain until a domain controller has authenticated them.
  28. 28. Network Management Naresh Loganathan Page 28 In server-based networks, a network administrator centrally manages the resource security. The administrator defines and manages user access to network resources. Another beneficial of server-based networks is central file storage. Server-based networks provide easy backup of critical data. Data backup is another useful characteristic of server based networks. Server based networks can support a larger number of users than peer-to-peer networks. To support a large number of users, server-based networks use monitoring and network management tools. Servers must perform varied and complex tasks. Advantages of a client/server network Centralized - Resources and data security are controlled through the server. Security - More security then Peer-to-peer network. Flexibility - New technology can be easily integrated into system. Interoperability - All components (client /server) work together. Accessibility - Server can be accessed remotely and across multiple platforms. Disadvantages of a client/server network Expense, requires initial investment in dedicated server. Maintenance, large networks will require a staff to ensure efficient operation. Dependence, when server goes down, operations will cease across the network.
  29. 29. Network Management Naresh Loganathan Page 29 compares the features of client/server networking (such as with Novell NetWare, Windows NT Server, and Windows 2000/XP) with peer-to-peer networking (such as with Windows for Workgroups, Windows 9x, Windows Me, and Windows NT Workstation). This table will help you decide which type of network is appropriate for your situation. Table 10.1. Comparing Client/Server and Peer-to-Peer Networking Item Client/Server Peer-to-Peer Access control Via user/group lists of permissions. A single password provides user access to only the resources on that list; users can be given several different levels of access. Via password lists by resource. Each resource requires a separate password. All-or-nothing access is used. No centralized user list exists. Security High, because access is controlled by user or by group identity. Low, because knowing the password gives anybody access to a shared resource. Performance High, because server doesn’t waste time or resources handling workstation tasks. Low, because servers often act as workstations. Hardware cost High, because of specialized design of server, high-performance nature of hardware, redundancy features. Low, because any workstation can become a server by sharing resources. Software cost License fees per workstation user are part of the cost of the Network Operating System server software (Windows NT/2000/XP Server, Novell NetWare). Free; all client software is included with any release of Windows 9x, Windows NT Workstation, Windows 2000 Professional, Windows Me, or Windows XP. Backup Centralized when data is stored on server; allows use of high-speed, high- capacity tape backups with advanced cataloguing. Left to user decision; usually mixture of backup devices and practices at each workstation. Redundancy Duplicate power supplies, hot-swappable drive arrays, and even redundant servers are common. Network OS normally is capable of using redundant devices automatically. No true redundancy among either peer ―servers‖ or clients. Failures require manual intervention to correct with high possibility of data loss.
  30. 30. Network Management Naresh Loganathan Page 30 Difference between client/server and peer-to-peer networksIn terms of security and cost There’s a huge difference between client/server and peer-to-peer networks. For instance, a peer-to-peer network has no central server. Each workstation on the network shares its files equally with the others. There’s no central storage or authentication of users. Conversely, there are separate dedicated servers and clients in a client/server network. Through client workstations, users can access most files, which are generally stored on the server. The server will determine which users can access the files on the network. Peer-to-peer networks should be installed in homes or in very small businesses where employees interact regularly. They are inexpensive to set up (comparatively speaking); however, they offer almost no security. On the other hand, client/server networks can become as big as you need them to be. Some support millions of users and offer elaborate security measures. As you can imagine, client/server networks can become very expensive. Peer-to-peer networks Peer-to-peer networks are appropriate only for very small businesses or for home use. A peer- to-peer network can support about ten clients (workstations) before it begins to suffer from some serious performance and management problems. Usually, peer-to-peer networks are composed of a collection of clients that run either Windows NT Workstation or Windows 98. Windows 3.11, Windows 95, and Windows 2000 Professional also support peer-to-peer networking. The concept behind peer-to-peer networking is to share files and printers as inexpensively as possible; therefore, there’s no main server on the network. Instead, each client functions both as a client and as a server simultaneously. Since users are allowed to control access to the resources on their own computers, however, security becomes very risky in a peer-to-peer environment. There’s no central security or any way to control who shares what. Users are free to create any network share points on their computers. The only security on a peer-to-peer network is at the share level. When users create network shares, they may implement no security, which means that anyone can have full access to the share, or they may assign a password to the share. Depending on which networking platform you use, a user may be able to assign one password to a share for read-only access and another password for full control over the share. Although this arrangement may sound somewhat secure, it isn’t. The computer that contains the shared resources doesn’t check on who’s trying to access those resources. Any user can access them as long as the user knows the password. If someone happens to write down a password, anyone who finds that password can access the share. Client/server networks There are an almost infinite variety of client/server networks, but all of them have a couple of things in common. For one thing, all have centralized security databases that control access to shared resources on servers. In the world of Windows, the server usually runs NetWare, Windows NT, or one of the Windows 2000 Server products. The server contains a list of usernames and passwords. Users can’t log on to the network unless they supply valid usernames and passwords to the server. Once logged on, users may access only those resources that the network administrator allows them to access. Thus, client/server networks possess much more security than do peer-to-peer networks.
  31. 31. Network Management Naresh Loganathan Page 31 Client/server networks also tend to be much more stable. In a peer-to-peer network, certain shared resources reside on each user’s machine. If users decide to monkey around and crash their computers, they could seriously affect their peer-to-peer network (where coworkers depend on resources that reside on other users’ machines). On most client/server networks, however, shared resources reside on the server, where they’re safe from curious users. If a user happens to erase a shared resource from the server, you can rely on the nightly backup. (It’s very difficult to back up a peer-to-peer network every night.) The primary downside to a client/server network is its cost. Servers can become very expensive. For example, you could pay over $800 for a copy of Windows NT Server and five client licenses, and that price doesn’t even include the cost of the hardware, which must be more powerful than a standard workstation. Additionally, client/server networks require an employee to manage them. Unless you have someone in your office who’s trained in NetWare or Windows NT Server and in all of the issues that are involved in client/server networking, you’ll have to hire someone from the outside. And believe me when I say that qualified networking professionals don’t come cheap.
  32. 32. Network Management Naresh Loganathan Page 32 Task 03 Task 3.1 Design a total network solution for a company which has around 25 computers and have 2 servers respectively one for web server and the other one for file sharing propose and Internet connectivity.This design must reflect a high availability on all aspect of the networking starting from LAN to WAN. This task provides evidence for P14.2.3, P14.3.1, P14.3.3, P14.4.
  33. 33. Network Management Naresh Loganathan Page 33 Task 3.2 Compare and contrast OSI and TCP/IP proposed network management standards This task provides evidence for P14.3.2 Transmission Control Protocol is used by Internet applications like email, world wide web, FTP, etc. TCP/IP was developed by the Department of Defence (DOD) to connect various devices to a common network (Internet). The main purpose behind developing the protocol was to build a robust and automatically recovering phone line failure while on the battlefield. On the other hand, Open Systems Interconnection was developed by the International Organization for Standardization (ISO). This model was made up of two components, namely, seven-layer model and the subset of protocols. Distinguishing Points Both the TCP/IP and OSI model work in a very similar fashion. But they do have very subtle differences too. The most apparent difference is the number of layers. TCP/IP is a four-layered structure, while OSI is a seven-layered model.
  34. 34. Network Management Naresh Loganathan Page 34 TCP/IP Model The Internet Protocol Suite, popularly known as the TCP/IP model, is a communication protocol that is used over the Internet. This model divides the entire networking functions into layers, where each layer performs a specific function. This model gives a brief idea about the process of data formatting, transmission, and finally the reception. Each of these functions take place in the layers, as described by the model. TCP/IP is a four-layered structure, with each layer having their individual protocol. Let us have a look at the four layers: Link Layer As the name suggests, this layer includes the physical and logical connections from the host's link. It is also known as Network Access layer and Network Interface layer. It explains how the data is transmitted from the host, through the network. The physical connectors like the coaxial cables, twisted pair wires, the optical fiber, interface cards, etc., are a part of this layer. This layer can be used to connect different network types like ATM, Token ring, Ethernet, LAN, etc. Internet Layer This layer is also known as the Network Layer. The main function of this layer is to route the data to its destination. The data that is received by the link layer is made into data packets (IP datagrams). The data packets contain the source and the destination IP address or logical address. These packets are sent on any network and are delivered independently. This indicates that the data is not received in the same order as it was sent. The protocols at this layer are IP (Internet Protocol), ICMP (Internet Control Message Protocol), etc.
  35. 35. Network Management Naresh Loganathan Page 35 Transport Layer This layer is responsible for providing datagram services to the Application layer. This layer allows the host and the destination devices to communicate with each other for exchanging messages, irrespective of the underlying network type. Error control, congestion control, flow control, etc., are handled by the transport layer. The protocol that this layer uses is TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP gives a reliable, end- to-end, connection-oriented data transfer, while UDP provides unreliable, connectionless data transfer between two computers. Application Layer It provides the user interface for communication. This is the layer where email, web browsers or FTP run. The protocols in this layer are FTP, SMTP, HTTP, etc. OSI Model The Open Systems Interconnected (OSI) model divides the network into seven layers and explains the routing of the data from source to destination. It is a theoretical model which explains the working of the networks. It was developed by the International Organization for Standardization (ISO) for their own network suite. Here are the details of OSI's seven layers: Physical Layer As the name suggests, this is the layer where the physical connection between two computers takes place. The data is transmitted via this physical medium to the destination's physical layer. The popular protocols at this layer are Fast Ethernet, ATM, RS232, etc. Data Link Layer The main function of this layer is to convert the data packets received from the upper layer into frames, and route the same to the physical layer. Error detection and correction is done at this layer, thus making it a reliable layer in the model. It establishes a logical link between the nodes and transmit frames sequentially. Network Layer The main function of this layer is to translate the network address into physical MAC address. The data has to be routed to its intended destination on the network. This layer is also responsible to determine the efficient route for transmitting the data to its destination. While doing so, it has to manage problems like network congestion, switching problems, etc. The protocols used here are IP, ICMP, IGMP, IPX, etc.
  36. 36. Network Management Naresh Loganathan Page 36 Transport Layer This layer provides end-to-end delivery of data between two nodes. It divides data into different packets before transmitting it. On receipt of these packets, the data is reassembled and forwarded to the next layer. If the data is lost in transmission or has errors, then this layer recovers the lost data and transmits the same. Session Layer This layer is responsible to establish and terminate connections between two communicating machines. This connection is known as a session, hence the name. It establishes full-duplex, half-duplex and simplex connection for communication. The sessions are also used to keep a track of the connections to the web server. Presentation Layer The data conversion takes place at this layer. The data that it receives from the application layer is converted into a suitable format that is recognized by the computer. For example, the conversion of a file from .wav to .mp3 takes place at this layer. Application Layer This layer provides a user interface by interacting with the running application. E-mail, FTP, web browsers, etc., are the network applications that run on this layer. The entire communication industry stands on the backbone of TCP/IP and OSI reference model. It is absolutely vital to learn the above differences, if anyone wants to be an expert in the field of communication.
  37. 37. Network Management Naresh Loganathan Page 37 Task 3.3 Describe the responsibilities of Network Administrator. Simply put, network administrators administer networks, which means that they take care of the tasks of installing, configuring, expanding, protecting, upgrading, tuning, and repairing the network. Network administrators take care of the network hardware, such as cables, hubs, switches, routers, servers, and clients, as well as network software, such as network operating systems, e-mail servers, backup software, database servers, and application software. On a big network, these responsibilities constitute a full-time job. Large networks tend to be volatile: Users come and go, equipment fails, cables break, and life in general seems to be one crisis after another. Smaller networks are much more stable. After you get your network up and running, you probably won’t have to spend much time managing its hardware and software. An occasional problem may pop up, but with only a few computers on the network, problems should be few and far between. Regardless of the network’s size, all network administrators must attend to several common chores: Equipment upgrades The network administrator should be involved in every decision to purchase new computers, printers, or other equipment. In particular, the network administrator should be prepared to lobby for the most network-friendly equipment possible, such as new computers that already have network cards installed and configured and printers that are network ready. Configuration The network administrator must put on the pocket protector whenever a new computer is added to the network. The network administrator’s job includes considering what changes to make to the cabling configuration, what computer name to assign to the new computer, how to integrate the new user into the security system, what rights to grant the user, and so on.
  38. 38. Network Management Naresh Loganathan Page 38 Software upgrades Every once in a while, your trusty operating system vendor (in other words, Microsoft) releases a new version of your network operating system. The network administrator must read about the new version and decide whether its new features are beneficial enough to warrant an upgrade. In most cases, the hardest part of upgrading to a new version of your network operating system is determining the migration path — that is, how to upgrade your entire network to the new version while disrupting the network or its users as little as possible. Upgrading to a new network operating system version is a major chore, so you need to carefully consider the advantages that the new version can bring. Patches Between upgrades, Microsoft releases patches and service packs that fix minor problems with its server operating systems. For more information, see the section ―Patching Up Your Operating System and Software‖ later in this chapter. Performance maintenance One of the easiest traps that you can get sucked into is the quest for network speed. The network is never fast enough, and users always blame the hapless network manager. So the administrator spends hours and hours tuning and tweaking the network to squeeze out that last 2 percent of performance. Ho-hum chores Network administrators perform routine chores, such as backing up the servers, archiving old data, freeing up server hard drive space, and so on. Much of network administration is making sure that things keep working and finding and correcting problems before any users notice that something is wrong. In this sense, network administration can be a thankless job. Software inventory Network administrators are also responsible for gathering, organizing, and tracking the entire network’s software inventory. You never know when something is going to go haywire on Joe in Marketing’s ancient Windows 2000 computer and you’re going to have to reinstall that old copy of WordPerfect.
  39. 39. Network Management Naresh Loganathan Page 39 Designing the Network The first phase in the life cycle of a network involves creating its design, a task not usually performed by new network administrators. Designing a network involves making decisions about the type of network that best suits the needs of your organization. In larger sites this task is performed by a senior network architect: an experienced network administrator familiar with both network software and hardware. Setting Up the Network After the new network is designed, the second phase of network administration begins, which involves setting up and configuring the network. This consists of installing the hardware that makes up the physical part of the network, and configuring the files or databases, hosts, routers, and network configuration servers. The tasks involved in this phase are a major responsibility for network administrators. You should expect to perform these tasks unless your organization is very large, with an adequate network structure already in place. Maintaining the Network The third phase of network administration consists of ongoing tasks that typically constitute the bulk of your responsibilities. They might include: Adding new host machines to the network Administering network security Administering network services, such as NFS services, name services, and electronic mail Troubleshooting network problems Expanding the Network The longer a network is in place and functioning properly, the more your organization might want to expand its features and services. Initially, you can increase network population by adding new hosts and expanding network services by providing additional shared software. But eventually, a single network will expand to the point where it can no longer operate efficiently. That is when it must enter the fourth phase of the network administration cycle: expansion. Several options are available for expanding your network: Setting up a new network and connecting it to the existing network using a machine functioning as a router, thus creating an internetwork Configuring machines in users' homes or in remote office sites and enabling these machines to connect over telephone lines to your network Connecting your network to the Internet, thus enabling users on your network to retrieve information from other systems throughout the world Configuring UUCP communications, enabling users to exchange files and electronic mail with remote machines.
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