Network Management Concepts and Practice

1. Network ManagementConcepts and Practice Author: J. Richard Burke Presentation by Shu-Ping Lin

2. Outline • Network Components • Overview of Network Management

3. Communication Architecture • A communication architecture integrates many protocols and the software that implements them. • These parts can be developed independently of one another as long as the developers adhere to the standard interfaces between them.

4. OSI Reference Model

5. OSI Reference Model • The model does not specify how to implement the function in each layer. • The functions in each layer are defined by protocol, which are implemented in software. • The software in each layer provides services to the layer above it. • Layering concept simplifies the development process and allows improvements of software in one layer without affecting other layers.

6. Physical Layer • This layer defines the electrical, mechanical, functional specifications for hardware that connects a device to the network. • Physical layer standards would specify • Connector’s size and shape • Exact number of pins • The signals that can be used to those pins

7. Data Link Layer • This layer specifies the procedures in order to achieve reliable point-to-point transfer of information between two devices. • Data link layer can be divided into two sublayers. • Logical Link Control • Medium Access Control

8. Data Link Layer (cont’d) • CSMA/CD is implemented in Ethernet. • CSMA means that a computer waits until there is no signal from any other computer on LAN before transmitting a message. • CD reduces the probability that a collision will occur by backoff its transmission. • Bridge is a typical device working on data link layer.

9. Network Layer • This layer provides the mechanisms for transporting a packet from the source networks to the destination network. • Packets are messages constructed by the network layer and higher layers. • A router is called a network layer device because it is controlled by protocols up to and including the network layer.

10. Transport Layer • Transport layer provides reliable and unreliable transport protocols. • The reliable protocol, which is called the Transport Control Protocol (TCP), provides the mechanisms that enable end-to-end reliability. • TCP accomplishes this by the use of automated acknowledgement and automated retransmissions.

11. Transport Layer (cont’d) • The unreliable transport protocol, which is called the User Datagram Protocol (UDP), places no constrains on the network. • Best-effort delivery from the source device to the destination device is all that is required. • UDP is used when speed is of the essence and the effort spent on ensuring reliability is not cost-effective.

12. Session Layer • The Session layer provides the mechanisms necessary to open and close multiple logical connections between processes on different PCs. • These logical connections are called session. • Many logical connections can use the same physical connection.

13. Presentation Layer • This layer provides a common representation of data transferred between peer application layer entities on different stations. • Abstract syntax notation.one (ASN.1) format is useful for application layer. • However, the layers below the presentation layer use a formant call transfer syntax. • The presentation layer translates between ASN.1 and transfer syntax.

14. Application Layer • Common Application Service Elements provide service generally useful to a variety of application programs provided by vendors. • Specific Application Service Elements service the additional needs of particular application programs.

15. Frames • Frame construction • Application program makes a request. • The request is passed to the appropriate application-layer-entity. • The application-layer-entity constructs an Application layer protocol data unit (PDU). • The Application layer PDU is then passed to the appropriate presentation-layer-entity. This entity constructs a Presentation layer PDU.

16. Frames (cont’d) • PDUs continue to be constructed and passed to the layers below. This process continues until the Network layer PDU is received by the Data Link layer. • The frame is construct in the Data Link layer. The Network Layer PDU is encapsulated in a Data Link layer header and trailer.

17. Frames (cont’d)

18. TCP/IP Protocol Stack

19. Network Device • Workstations • Servers • Repeaters • Hubs • Bridges • Switches • Routers • Probes

20. Workstations • Workstations typical make use of the services of all layers of a protocol stack because they process the requests of application programs for information on servers. • Server is like workstation making use of all layers of the protocol stack.

21. Repeater • Repeater amplifies the signal between segments and extends the length of a LAN. • Repeaters are used on 10BASE2 and 10BASE5 LANs.

22. Hubs • A hub is a repeater with many input and output ports. • Every transmission received by the hub on one port is amplified and retransmitted out of all other ports. • Hub do not examine information in any field of the frame. • Repeaters and hubs are consider a Physical layer device.

23. Bridges • Transparent bridge • divides a LAN into segments that use the same media access control specification and it controls what traffic is passed between segments. • uses bridge table to learn which devices are on which segments. • Translating bridges connects networks using different MAC layer specifications.

24. Bridges (cont’d) • Errors and collisions that take place on one segment are not propagated to devices on the other segment. • The use of switches rather than bridges is commonplace today.

25. Switches • A switch is a multiport bridge. • Switches are typically configured to forward incoming frames to outgoing ports based on destination MAC addresses associated with those ports in the switch table. • Switches also can be configured to drop frames based on MAC destination or to redirect frames to other MAC address.

26. Switches (cont’d) • Higher layers of the protocol stack are now being implemented in switches. • Layer 3 switch also can function like router.

27. Routers • Router reads the Network layer header in packet to find the destination network address and then looks up the address in routing table. • The routing table is a list of mappings of network addresses to ports that will get the packet to the destination networks by the best means.

28. Routers (cont’d) • Routing table

29. Probes • Probes are tools for learning about the details of the communication between devices. • Probes can be placed on a network and the information they gather transferred to the Management Station fro analysis of the traffic.

30. Outline • Network Components • Overview of Network Management

31. Network Management • Jobs of network management in early day • Attaching PCs and server to a LAN using Network Interface Cards (NICs) • Installing protocol stacks • Configuring NIC I/O addresses and interrupts so as not to conflict with other NIC selections. • Using Ping application to ensure that all devices on the network could communicate with one another

32. Network Management (cont’d) • Access control • The manager might write a script for the server to control access to information on it. • The script would provide access to drives, folders or files that use or group of users needed. • Install a print server to manage the print jobs from each of the PCs.

33. Network Management (cont’d) • Network configuration • If the networks were to be divided into subnets, then a bridge would be used to connect them. • The manager would configure a routing table to enable connectivity according to network address, subnet address and subnet mask. • Finally, installing user applications on PCs is necessary for interfacing correctly with OS.

34. Maintenance • After configuring primary network ingredients, here comes the maintenance. • Network performance is not optimized, there will be software and hardware failures and network resources will change. • The manager is required to make estimates of the network capacity. • There was a need for minimal security.

35. Maintenance (cont’d) • New work management has divided into specialties nowadays. • Administration • Backing up servers • Maintaining security • Installing OS and applications • Network engineer • Be responsible for the health of the network and its availability to user.

36. Network-Based Management • As network has grown larger and more complicated, network manager needed to find more efficient way to determine and control the state of network. • Some protocols could be used by network manager to remotely control devices. • Simple Network Management Protocol (SNMP) • Management Information Base (MIBs) • Network Management Systems (NMS)

37. Network Management Protocol Stack • Management Station and Management Agent.

38. Network Management Example • Step 1 • NMS calls for the service of the management process • Step 2 • the management process call the program the implements network management protocol. • Step 3 • NMP constructs a request packet to the program on the management agent. • Step 4 • NMP on the management agent cause the request packet to be passed to the agent process.

39. Network Management Example (cont’d) • Step 5 • The agent process accesses the value of the requested variable and passes it to NMP. • Step 6 • NMP constructs the response packet which is sent back to the management station. • Step 7 • At the management station the program that implements the NMP receives the response packet. • Step 8 • The management process passes the requested value to the application program.