Designing Real-World Networks

CSC 363

4 February, 1999

Announcements

• Midterm exam due on Tuesday, 9 Feb at noon

• Group projects--how are they going? Who’s doing what?

Some Real World Networks

• Ethernet

• Token Ring

• FDDI

• ATM

• ARCnet (we won’t cover this one--not in use anymore)

Ethernet Characteristics

• Many flavors

• CSMA/CD

• Mature

• Flexible

Ethernet Operation

• Signaling on the wire

• Collision Detection

• Backoff Algorithm

Problem:

• You need to connect, with Ethernet, two buildings in the same college campus. The buildings are 980 miles apart, as the crow files. Which medium will you use?

Problem:

• You have four Ethernet stations to attach for a small accounting firm on a tight budget. All stations are located in the same room. Which medium will you use?

Problem:

• Every once in awhile, your 20-stations 10Base2 network goes down. You’ve traced the problem to a secretary who occasionally rolls his chair over his thinnet cable, breaking the network connection momentarily, which causes your NetWare file server to drop connections to all the clients. You can’t really move his computer, and since 10Base2 requires the cabling to go in and out of the computer, you can’t do anything about the location of the thinnet cable, either. All the network adapters in your LAN are 10Base2/10BaseT combo adapters. What can you do to make certain no single faulty cable can bring down your network?

Problem:

• You have a large (400-station) Ethernet network to design. Your client wants to use the most flexible architecture possible, because they intend to upgrade to either faster versions of Ethernet or possible ATM in the next five years. Which medium will you use? Will you use any other types of media in portions of the network?

Problem:

• You need to connect two networks together across a busy street. The city will not grant a right-of-way to dig or tunnel under the street, and municipal ordinances prevent the use of an aerial cable. Which medium will you use?

100Mbps Ethernet

• 100VG AnyLAN

• Fast Ethernet

Compare and Contrast

Problem:

• You have a client who is installing a new UTP network with 50 new, Pentium class PCs. Her graphics design company will be using the computers to manipulate complex graphical advertising materials. Which network architecture do you recommend?

Problem:

• You have a client who wants to migrate to 100Mbps Ethernet but doesn’t have the budget to replace all the installed category 3 wiring in his building. Which network architecture do you recommend?

Token Ring

• Interface equipment (MAU, MSAU (IBM), SMAU

• Cabling

• Patch cables

Problem:

• Your computer is connected to a 20-node Token Ring network. It has not heard from its nearest upstream neighbor in seven seconds, the time allotted for token passing. Identify and describe the process that is activated by your computer.

FDDI

• Deterministic token passing network

• Multiple frames on the ring at one time--full-circle not required before new transmissions take place.

• Tokens released when transmit complete

Problem:

• You have set up a FDDI network to include a backup server, which performs routing, regularly scheduled backups of nodes on the ring. What is the FDDI option that enables the backup machine to transmit and receive backup data from each machine at a regular time, regardless of the machine holding the token?

ATM

• Point-to-point switched network

• 53-octet (8 bits *53) cells

• PVCs

• SVCs

Problem:

• You are designing an experimental ATM backbone that will run in parallel with your FDDI backbone for one year. You will place traffic on the ATM backbone during test cycles and slowly transition from the FDDI to ATM backbones in months 10, 110, and 12 of the experiment. Should you buy a switch with SVC capabilities, PVC capabilities, or both? Why?

LAN Design

• Complexity

• Technology

• Physical Plant

Decision Factors in LAN Complexity

• Network scale

• Distance between computers

• What kind of traffic will the network carry

• What kind of software will be used

• Special Requirements

• Budget

Network Designs-simple to complex

• Peer network

• single-server network

• Multi-server network

• Multi-server high-speed backbone network

• Enterprise network

Problem:

• You are in charge of putting together a network for a small company. There are only seven employees, and each employee needs a computer to share e-mail and files with other people in the company. Security is not a vital concern, but cost is, and all individuals can be depended upon to maintain their own computers. Will you install a peer network or a single-server network? Why?

Problem:

• Your company has 4 departments-marketing, engineering, production, and administration, with 35, 55, 25, and 10 computers in each division, respectively. You have a sever running Windows NT that provides file storage for everyone; it also hosts a SQL database back end for Administration and maintains the Internet connection for e-mail and Marketing’s WWW pages. The network is slow and getting slower. You have adequate funds for modest improvements.

• 1. Explain the advantages of providing each department with its own departmental file server.

• 2. Do you need a high-speed backbone between the servers? Explain.

Problem:

• You are a networking consultant to a large manufacturing corporation that is replacing its mainframe computing system with a network of specialized servers and PCs. The headquarters occupies several large businesses on a campus, and there will be over 700 client computers connected to the network when installation is complete. Huge amounts of information will be transferred from department to department (and from building to building) as products move through the stages of research, development, production, and support. How will you tie the servers together?

Decision Factors in Networking Technologies

• Appropriate to traffic and software

• Appropriate to physical plant

• Appropriate to budget

• Appropriate to distances and max. nodes

Problem:

• You have been given the assignment to install a network for a small law firm. The computers will mostly be used for e-mail, scheduling, word processing, and searching for information on legal reference CD ROMs. The senior partner in the firm has heard about fiber and high-speed networking and asks you if a FDDI ring would be appropriate for the firm. What is your reply?

Problem:

• You have been asked to prepare a plan for the future growth of your organization’s network. The CIO wants you to consider new technologies that will support the bandwidth-intensive applications of the future. What technologies will be the focus of your report?

Problem:

• You have an installed network of several hundred stations and several servers on a 10baseT Ethernet network. You would like to increase the bandwidth between the servers and the most demanding clients but leave the rest of the network on 10baseT Ethernet. How will you achieve this goal?

Decision Factors in Physical Plant

• Network topology

• Cost per location

• Distance Limitations

• Other Limitations

• Bandwidth