Local Area Networking

1. Local Area Networking Chapter 8

2. Knowledge Concepts • Components of a LAN • Transmission media • Transport • Access methods • Topologies • Interconnection • VLANs • Switches and routers

3. LAN Cabling system Broadband vs baseband CSMA/CD Token Tree ISPF, RIP BGP-4 Bus Ring Star Switch Vlan Bridge Router learning Static vs dynamic Important Vocabulary

4. Topology Topology is the basic geometric layout of the network -- the way in which the computers on the network are interconnected. • Ethernet uses a bus topology (a high speed circuit and a limited distance between the computers, such as within one building).

5. Bus Topology Terminators required on each end

6. Ring Topology Data Flow

7. Token Ring

8. Star Topology Preferred method for today’s LANs Wiring Hub

9. Media Access Control • Ethernet uses a contention-based technique called Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • If two computers attempt to transmit at the same time, they detect the collision, send a jamming signal, wait a random amount of time, then re-broadcast.

10. Node Number/Access Determines Type

11. Most of the World Uses Ethernet

12. Ethernet Tree Topology • Each hub broadcasts to own segment • Misbehaving nodes will be shut off by the hub

13. Throughput • CSMA/CD works well for small number • Of nodes per wire • Throughput defined as useful data that • Can go across wire • PPS (packet per sec) or percent • Utilization of wire speed

14. LANs Cheaper as Nodes Increase

15. Break-point

16. Network Servers: Everything You Wanted to Know But Were Afraid to Ask! • Servers use multiple processors • Very important to access-intensive operations • Multiple processors provide 50% improvement • Buses provide backbone internal support for data transfer • RAM provides a buffer for operations

17. LAN Operating System Functions • Optimized I/O • One of the main services provided by a server is disk access. Disk access consists of three components: seek, latency, and transfer. • I/O optimization attempts to reduce one or more of these disk access components. • Disk Configurations • One of the functions of an OS is to implement a file system. This involves allocating and deallocating disk space and keeping track of space allocated to each file. • Partitioning • Sometimes it is beneficial to divide a single disk drive in two or more partitions; each partition can be managed separately

18. LAN Operating System Functions (cont.) • Single Disk Volume • A volume is a logical disk (a partition or collection of partitions) or physical disk that has been formatted and can be used to store data by an OS. • Multiple Disk Volumes or Volume Sets • Most LAN OSs allow multiple partitions or disks to be combined to form a single logical partition. • A volume created from multiple partitions is called a volume set. • RAID Level 0—Striping without parity • Another capability provided with some LAN OSs is called a Redundant Array of Inexpensive Disks (RAID) Level 0 or striping without parity. Multiple partitions on different disks can be combined to proved a single logical disk; striping with parity differs from a volume just described in that data is written to all partitions simultaneously.

19. Fault Tolerance • A LAN with fault tolerance allows the server to survive some failures that would ordinarily be disabling. Fault tolerance usually is provided by a combination of backup hardware components and software capable of using the backup hardware. • A level of fault tolerance also can be provided by using redundant arrays of inexpensive disks (RAID). There are six levels of RAID, but for fault tolerance we are concerned only with RAID Level 1 and RAID Level 5.

20. It’s a RAID! • Disk arrays improve performance and redundancy • RAID (Redundant Array of Inexpensive Disks) is a method used to write across (stripe) multiple disks to improve performance and fault tolerance • RAID 1 and 5 most popular but all have problems

21. RAID File Disk 1 Disk 2 RAID 0--Stripes data between disks RAID 1--Mirrors data between disks

22. Mirrored Disk Drives Duplexed Controllers Controller 1 Controller 2 File 1 File 1 File 2 File 2 2 1

23. Raid Level 5 Technology Server File 1 Part 1 File 1 Part 2 File 1 Parity File 1 Part 3 File 2 Part 2 File 2 Part 3 File 2 Part 1 File 1 Parity 1 2 3 4

24. A Fault-Tolerant Duplexed Server Duplexed Servers Dedicated High-Speed Connection Disk Drive Disk Drive Mirrored Disk Drives

25. Backup Software • The software used to perform the backups is as important as the hardware. Backup software is responsible for reading the files being backed up and writing them to the backup device. • Backup devices often come with a backup/restore program (both capabilities are contained on one program), and most LAN system software includes a backup/restore module. • Some LAN administrators choose to purchase a separate, more functional backup system than the LAN or backup device versions.

26. Immediate and Recurring Costs of a LAN Immediate Costs Equipment upgrades Documentation Installation of cabling System software installation Creating user environments Space required for new equipment LAN management—personnel costs Consumable supplies—toner, paper, etc. Training users, operators, administrators Site preparation Hardware installation Installing applications Testing Supplies and spares Hardware and software maintenance Training new users, administrators Recurring Costs

27. Basic LAN Management Tasks User/Group Oriented Add, delete users and groups Set user environment Install/remove printers Maintain printers Add/change/delete hardware Add/change/delete hardware Plan and implement changes Make backups Carry out recovery as necessary Plan capacity needs Serve as liaison with other network administrators Set user/group security Solve user problems Setup user/printer environment Manage print jobs Establish connections with other networks Diagnose problems Maintain operating procedures Educate users Monitor the network for problems and to gather statistics for capacity planning Printer Oriented Hardware/Software Oriented General

28. Backup Devices • Removable Disk Drives • Manual intervention is necessary for changing disk cartridges, whereas some tape backup system provide tapes with much higher storage capacity and with automatic tape changing. • Hard-Disk Drives • The arguments for and against this alternative are much the same as those for diskettes. The major difference is that the capacity of hard-disk drives is greater than that of diskettes.

29. Backup Devices (cont.) • Optical Disk Drives • Optical disk drives are gaining popularity as input, output, and backup devices. The reasons for this are their decreasing costs and large storage capacity. • Magnetic Tape Drives • A magnetic tape drive is the usual choice for a backup device. Magnetic tapes are less expensive than the other options. They hold large volumes of data, are easy to use and store, and generally provide good performance.

30. Primary Backup Technologies 1.44 MB Multiple capacities 40 MB to over 1 G To 15 GB 160 MB 2.2 GB To 2.2 GB To 100 MB To 4 GB 10-14 GB 2.88 MB 60 MB 500 MB 15 GB 20 MB 150 MB 1.2 GB 70 GB (compressed) Diskette backup Hard drive, fixed Hard drive, removable cartridge Tape backup, 4mm or 1/4 inch Tape backup, 8mm or VCR Tape backup, 9-track Optical drives Digital versatile disks (when available)

31. Backup Functions Back up all files Differential backup Back up all files modified since a particular date Back up by directory Back up automatically by time or calendar Back up all but a list of files to be excluded Start backup from workstation or server Back up by interface to a database Back up using wildcard characters in file names Incremental backup Maintain index on tape and disk Maintain cross-reference of tape serial numbers and backup Back up manually Back up by list of files Back up by index Compress data Back up multiple volumes Generate reports

32. Gateways • Gateways operate at the network layer and use network layer addresses in processing messages. • Gateways connect two or more LANs that use the same or different (usually different) data link and network protocols. They may connect the same or different kinds of cable. • Gateways process only those messages explicitly addressed to them.

33. Gateways • Gateways translate one network protocol into another, translate data formats, and open sessions between application programs, thus overcoming both hardware and software incompatibilities. • A gateway may be a stand-alone microcomputer with several NICs and special software, a FEP (Front End Processor) connected to a mainframe computer, or even a special circuit card in the network server.

34. Gateways • One of the most common uses of gateways is to enable LANs that use TCP/IP and Ethernet to communicate with IBM mainframes that use SNA. • The gateway provides both the basic system interconnection and the necessary translation between the protocols in both directions.

35. Gateways

36. Classic SNA Architecture

37. Standalone PC 3270 Terminal Emulation

38. LAN-based SNA Gateways

39. SNA/LAN Incompatibilities Yield Multiple Networks

40. TCP/IP Encapsulation

41. Switched Media Technologies • Over the past few years, there has been a major change in the way we think about LANs and backbone networks. LANs have traditionally used multipoint circuits, and WANs have traditionally used point-to-point circuits. • As the shared circuits in LANs and BNs (Backbone Networks) have become overloaded with traffic, networks are starting to use switched point-to-point circuits rather than shared multipoint circuits.

42. Switched Ethernet • The concept behind switched ethernet - and all switched media technologies - is simple; replace the LAN hub with a switch. Each computer now has its own dedicated point-to-point circuit. • Switched ethernet dramatically improves LAN performance. However, since much of the network traffic is to and from the server, the circuit to the server is often the network bottleneck.

43. Switched Ethernet

44. Switched Ethernet • One obvious solution is to increase the number of connections from the server to the switch so that traffic now can reach the server on several circuits. • Other solutions include: • Full Duplex Ethernet (full duplex over traditional 10Base-T). • 10/100 Switched Ethernet (combines 10Base-T and 100Base-T). This is often used to provide 10 Mbps to the clients and 100 Mbps to the server.

45. Full Duplex Ethernet

46. Switched Ethernet Switched Ethernet at Fish & Richardson

47. Switched Ethernet Site Networks No Maximum Distance Spans Hierarchies and Single Possible Paths High Speeds and Low Prices

48. Ethernet Switched Networks There are Distance Limits Between Pairs of Switches • 100 meters with UTP • Longer with optical fiber Ethernet Switch Maximum Separation 100 m with UTP Longer with optical fiber

49. Hierarchies Ethernet Switches Must be Arranged in a Hierarchy • Root is the top-level Root Ethernet Switch

50. Hierarchies • Usually, Fastest Switches are at the Top (Root) 100Base-X Building Switch Gigabit Ethernet Campus Switch 10Base-T Workgroup Switch