unit-5 chapter-10Selecting Technologies and Devices for Campus Networks 283

LAN Cabling Plant Design 284Cabling Topologies 284Building-Cabling Topologies 285Campus-Cabling Topologies 285Types of Cables 285LAN Technologies 289Ethernet Basics 290Ethernet and IEEE 802.3 290Ethernet Technology Choices 291Half-Duplex and Full-Duplex Ethernet 292100-Mbps Ethernet 292Gigabit Ethernet 29310-Gbps Ethernet 295Selecting Internetworking Devices for a Campus Network Design 299Criteria for Selecting Campus Internetworking Devices 300Optimization Features on Campus Internetworking Devices 302Example of a Campus Network Design 303Background Information for the Campus Network Design Project 303Business Goals 304Technical Goals 304Network Applications 305User Communities 306Data Stores (Servers) 307Current Network at WVCC 307Traffic Characteristics of Network Applications 310Summary of Traffic Flows 311Performance Characteristics of the Current Network 312Network Redesign for WVCC 313Optimized IP Addressing and Routing for the Campus Backbone 313Wireless Network 314Improved Performance and Security for the Edge of the Network 315Summary 316Review Questions 317Design Scenario 317

1.Mention two types of cabling topologies?A centralized cabling scheme terminates most or all of the cable runs in one area ofthe design environment. A star topology is an example of a centralized systemA distributed cabling scheme terminates cable runs throughout the design environment.Ring, bus, and mesh topologies are examples of distributed systems.

2.what are the types of cables?Three major types of cables:Shielded copper, including shielded twisted-pair (STP), coaxial (coax), and twinaxial(twinax) cablesUnshielded copper (typically UTP) cables Fiber-optic cables

3.what are the categories of UTP cabling?Category 1 and 2 are not recommended for data transmissions because of their lackof support for high bandwidth requirements.■ Category 3 is tested to 16 MHz. Category 3 is often called voice-grade cabling, butit is used for data transmission also, particularly in older 10BASE-T Ethernet and 4-Mbps Token Ring networks.■ Category 4 is tested at 20 MHz, allowing to run 16-Mbps Token Ring with a bettersafety margin than Category 3.■ Category 5 is tested at 100 MHz, allowing it to run high-speed protocols such as100-Mbps Ethernet and Fiber Distributed Data Interface (FDDI). When four pairsare used, Category 5 supports Gigabit Ethernet.■ Category 5 Enhanced (Category 5e) is suitable for 100-Mbps Ethernet, GigabitEthernet, and ATM. Many companies sell 350-MHz Category 5e cabling, althoughthe standard for the cabling (Addendum 5 to TIA/EIA-568-A) states 100 MHz.■ Category 6 is suitable for 100-Mbps Ethernet, Gigabit Ethernet, and ATM. The standardfor the cabling (ANSI/TIA/EIA-568-B.2-1) states 200 MHz, although vendorssupport higher bandwidths.

4.what is the LAN technologies?LAN technologies you should recommend■ Biases (technology religion)■ Policies about approved technologies or vendors■ The customer’s tolerance to risk■ Technical expertise of the staff and plans for staff education■ Budgeting and scheduling

5.what is the Ethernet?Ethernet is a physical and data link layer standard for the transmission of frames on aLAN. An Ethernet LAN that is accurately provisioned to meet bandwidth requirements and outfitted with high-quality components, including NICs, cables, and internetworking devices, can meet even the most stringent demands for availability

6.what is are options for implementing Ethernet networks?■ Half- and full-duplex Ethernet■ 100-Mbps Ethernet■ 1000-Mbps (1-Gbps or Gigabit) Ethernet■ 10-Gbps Ethernet■ Metro Ethernet■ Long-Reach Ethernet (LRE)■ Cisco EtherChannel

7.what are the four physical implementations of 100 Mbps?■ 100BASE-TX: Two pairs of Category 5 (or better) UTP cabling■ 100BASE-T2: Two pairs of Category 3 (or better) UTP cabling■ 100BASE-T4: Four pairs of Category 3 (or better) UTP cabling■ 100BASE-FX: Two multimode optical fibers

8.what is the Gigabit Ethernet?Gigabit Ethernet was originally defined in the IEEE 802.3z standard and is now mergedinto the full IEEE 802.3 standard. It operates essentially like 100-Mbps Ethernet, exceptthat it is 10 times faster. It uses CSMA/CD with support for one repeater per collisiondomain and handles both half- and full-duplex operations. It uses a standard 802.3 frameformat and frame size.

9.what are the Gigabit Ethernet Specifications?• 1000BASE-SX, also known as the short-wavelength specification ,appropriate for multimode horizontal cabling and backbone networks.• 1000BASE-LX uses a longer wavelenght specification supports bothmultimode and single-mode cabling. 1000BASE-LX is appropriate for building and campus-backbone networks.• 1000BASE-CX is appropriate for a telecommunications closet or computer room where the distance between devices is 25 m or less. 1000BASE-CX runs over 150-ohm balanced,shielded, twinax cable.• 1000BASE-T is intended for horizontal and work-area Category 5 or better UTP cabling.• 1000BASE-T supports transmission over four pairs of UTP cable and covers a cabling distance of up to 100 m, or a network diameter of 200 m. Only one repeater is allowed.

10.what is metro ethernet? Metro Ethernet supports a copper or fiber-opticinterface but uses fiber-optic cabling inside the provider’s network. It can use a variety of transport protocols, including Synchronous Optical Network (SONET), AsynchronousTransfer Mode (ATM), dense-mode wavelength-division multiplexing (DWDM), and Multiprotocol Label Switching (MPLS).

11.what is long reach ethernet?Long-Reach Ethernet (LRE), which can be used to connect buildings and rooms withinbuildings in campus networks. LRE provides a point-to-point link that can deliver a symmetrical,full-duplex, raw data rate of 11.25 Mbps over distances of up to 1 mile (1.6 km).

12.what is Cisco EtherChannel?Cisco provides EtherChannel ports for many of its high-end switches and routers. Intel and other vendorsmake EtherChannel NICs for servers.EtherChannel can be used between routers, switches, and servers on point-to-point links that require more bandwidth than a single Ethernet link can provide.

13.what are the criteria added in the router?■ Network layer protocols supported■ Routing protocols supported■ Support for multicast applications■ Support for advanced queuing, switching, and other optimization features■ Support for compression (and compression performance if it is supported)■ Support for encryption (and encryption performance if it is supported)

14.what are the business goals?■ Increase the enrollment from 600 to 1000 students in the next 3 years.■ Reduce the attrition rate from 30 to 15 percent in the next 3 years.■ Improve faculty efficiency and allow faculty to participate in more research projectswith colleagues at other colleges.■ Improve student efficiency and eliminate problems with homework submission.■ Allow students to access the campus network and the Internet wirelessly using theirnotebook computers.

■ Allow visitors to the campus to access the Internet wirelessly using their notebookcomputers.■ Protect the network from intruders.■ Spend a grant that the state government issued for upgrading the campus network.

15.what are the network applications?1.Homework2.Email3.Web research4.Library card catalog5.Weather modeling6.Telescope monitoring7.Graphics upload8.Distance learning9.College management system

16.what are the WVCC user communities?The expected growth of the communities is also included. Growth is expected for two reasons:■ New PCs and Macintoshes will be purchased.■ Wireless access will allow more students and visitors to access the network with theirpersonal laptop computers.

17.what are the campus network design features?• The network uses switched Ethernet. A high-end switch in each building is redundantly

connected to two high-end switches in the Computing Center.• Within each building, a 24- or 48-port Ethernet switch on each floor connects enduser

systems.• The switches run the IEEE 802.1D Spanning Tree Protocol.• The switches support SNMP and RMON. A Windows-based network management

software package monitors the switches. The software runs on a server in the server farm module of the network design.

18.what are theTraffic Characteristics of Network Applications?• The users of the weather-modeling and telescope-monitoring applications want to expand

their use of these applications, but are currently hindered by the amount of bandwidthavailable to the Internet.

• The graphics-upload application users are also hindered fromsending large files in a timely fashion by the shortage of bandwidth to the Internet.The distance-learning application is an asymmetric (one-way) streaming-video application.

19.what are the performance characteristics of the Current Network?• The IP addressing scheme supports just one IP subnet with a subnet mask of

255.255.255.0• The 1.544-Mbps connection to the Internet is overloaded. Average network utilizationof

the serial WAN link, measured in a 10-minute window, is 95 percent. The router drops about 5 percent of packets due to utilization peaks of 100 percent.

• The router itself is overloaded.The student assistants wrote a script to periodicallycollect the output of the show processes cpu command. The assistants discoveredthat the 5-minute CPU utilization is often as high as 90 percent and the 5-secondCPU utilization often peaks at 99 percent, with a large portion of the CPU power.

16 mark:1.what are the most important criteria for selecting a network device?At this point in the network design process, you have developed a network topology and

should have an idea of which segments will be interconnected. Table 10-3 provides areview of the major differences between internetworking devices that can be used to connectnetwork segments. In most cases, the choice will be between a switch and a router.Hubs and bridges are generally no longer used, although hubs are sometimes placed in anetwork to facilitate tapping into a network for protocol analysis, and bridges are stillsometimes used in wireless network. After you have designed a network topology and made some decisions about the placement and scope of shared, switched, and routed network segments, you should then recommend actual switches, bridges, and routers from various vendors. This section covers selection criteria you can use when making decisions.

Criteria for Selecting Campus Internetworking DevicesCriteria for selecting internetworking devices in general include the following:■ Number of ports■ Processing speed■ Amount of memory■ Amount of latency introduced when the device relays data■ Throughput in packets per second■ Ingress/egress queuing and buffering techniques■ LAN and WAN technologies supported■ Autosensing of speed (for example, 10 or 100 Mbps)■ Autodetection of half- versus full-duplex operation■ Media (cabling) supported■ Ease of configuration■ Manageability (for example, support for Simple Network Management Protocol[SNMP] and Remote Monitoring [RMON], status indicators)■ Cost■ Mean time between failure (MTBF) and mean time to repair (MTTR)■ Support for packet filters and other security measures■ Support for hot-swappable components■ Support for in-service software upgrades■ Support for redundant power supplies■ Support for optimization features■ Support for QoS features■ Availability and quality of technical support■ Availability and quality of documentation■ Availability and quality of training (for complex switches and routers)■ Reputation

Availability of independent test results that confirm the performance of the deviceFor switches and bridges (including wireless bridges), the following criteria can be addedto the first bulleted list in this section:■ Bridging technologies supported (transparent bridging, Spanning Tree Algorithm, remotebridging, and so on)■ Advanced spanning-tree features supported (rapid reconfiguration of spanning treesand multiple spanning trees [802.1s])■ The number of MAC addresses that the switch or bridge can learn■ Support for stacking or virtual switching where multiple switches can be managed asone switch■ Support for port security (802.1X)

■ Support for cut-through switching■ Support for adaptive cut-through switching■ VLAN technologies supported, such as the VLAN Trunking Protocol (VTP) andIEEE 802.1Q■ Support for multicast applications (for example, the ability to participate in the InternetGroup Management Protocol [IGMP] to control the spread of multicast packets)■ Amount of memory available for switching tables, routing tables (if the switch has arouting module), and memory used by protocol routines■ Availability of a routing module■ 802.3af Power over Ethernet (PoE) or 802.3at PoE+For routers (and switches with a routing module), the following criteria can be added tothe first bulleted list in this section:■ Network layer protocols supported■ Routing protocols supported■ Support for multicast applications■ Support for advanced queuing, switching, and other optimization features■ Support for compression (and compression performance if it is supported)■ Support for encryption (and encryption performance if it is supported)For wireless access points and bridges, the following criteria can be added to the first bulletedlist in this section:■ Wireless speeds supported (11 Mbps, 5.5 Mbps, 54 Mbps, and 600 Mbps)■ Wireless standards supported (802.11a, 802.11b, 802.11g, and 802.11n)Speed of uplink Ethernet port■ Support for Dynamic Host Configuration Protocol (DHCP), Network AddressTranslation (NAT), and IP routing■ Support for VLANs■ Support for inline power over Ethernet if the access point is unlikely to be mountednear power outlets■ Antenna range and support for higher-end antenna attachments■ Transmit power and receive sensitivity■ Ability to tune the transmit power■ Availability of a rugged model for outside use■ Support for authenticating client devices by MAC address■ Support for user authentication with 802.1X and the Extensible AuthenticationProtocol (EAP)■ Support for mutual authentication, which allows a client to be certain that it is communicatingwith the intended authentication server■ An option for disabling Service Set Identifier (SSID) broadcasts■ Support for 128-bit or better encryption■ Support for dynamic keys, unique keys for each user, per-packet keying, and a messageintegrity check (MIC)■ Support for one-time passwords or token cards■ Support for Publicly Secure Packet Forwarding (PSPF)■ Support for security standards such as WPA or 802.11i

Optimization Features on Campus Internetworking DevicesChapter 13, “Optimizing Your Network Design,” covers optimization and QoS in moredetail, but it is worth mentioning here that optimization and QoS features are moreimportant in campus network designs than many designers might expect. Not only isQoS required in the WAN, where the available bandwidth is lower than in the campus,but stringent requirements for low latency and jitter drive the need for QoS in LANswitches and routers as well. Even in campus networks, bandwidth demand on the networkoften exceeds the available bandwidth. In addition, VoIP drives the need for QoS

because of its requirement for low latency. QoS features should be considered whenselecting internetworking devices for campus networks.In most networks, at least some elements are oversubscribed and therefore require QoSfeatures. QoS features are most often required on uplinks from the distribution layer tothe core layer of a hierarchical network design. Sometimes QoS is required on uplinksfrom the access layer to the distribution layer also. The sum of the speeds on all ports ona switch where end devices are connected is usually greater than that of the uplink port.When the access ports are fully used, congestion on the uplink port is unavoidable.Access layer switches usually provide QoS based only on Layer 2 information, if at all.For example, access layer switches can base QoS decisions on the input port for traffic.Traffic from a particular port can be defined as high-priority traffic on an uplink port.The scheduling mechanism on the output port of an access layer switch ensures that trafficfrom such ports is served first. Input traffic can be marked to ensure the required servicewhen traffic passes through distribution and core layer switches.Distribution and core layer switches can provide QoS based on Layer 3 information,including source and destination IP addresses, port numbers, and QoS bits in an IP packet.QoS in distribution and core layer switches must be provided in both directions oftraffic flow. See Chapter 13 for more information on QoS and optimization.Example of a Campus Network DesignThe goal of this section is to present a campus network design that was developed usingthe design methodology in this book. The example is based on a real network design.Some of the facts have been changed or simplified to preserve the privacy of the designcustomer, to protect the security of the customer’s network, and to make it possible topresent a simple and easy-to-understand example.Background Information for the Campus Network Design ProjectWandering Valley Community College (WVCC) is a small college in the western UnitedStates that is attended by about 600 full- and part-time students. The students do not liveon campus. Approximately 50 professors teach courses in the fields of arts and humanities,business, social sciences, mathematics, computer science, the physical sciences, andhealth sciences. Many of the professors also have other jobs in the business community,and only about half of them have an office on campus. Approximately 25 administrationpersonnel handle admissions, student records, and other operational functions.Enrollment at WVCC has doubled in the past few years. The faculty and administrationstaff has also doubled in size, with the exception of the IT department, which is still quitesmall. The IT department consists of one manager, one server administrator, two networkadministrators, and two part-time student assistants.Because of the increase in enrollment and other factors covered in the next three sections,the current network has performance and reliability problems. The administrationhas told the IT department that both student and faculty complaints about the networkhave increased. Faculty members claim that, due to network problems, they cannot efficientlysubmit grades, maintain contact with colleagues at other colleges, or keep up withresearch. Students say they have handed in homework late due to network problems. Thelate submissions have impacted their grades. Despite the complaints about the network,faculty, staff, and student use of the network has doubled in the past few years.Wireless access has become a point of contention between the IT department and otherdepartments. Students often place wireless access points in the Computing Center and theMath and Sciences building without permission from the IT department. The IT manageris concerned about network security and has assigned part-time students to roam the networkto locate and remove unauthorized access points. The part-time students resent thistask because in many instances the rogue access points were installed by peers and associates.Also, they think that wireless access should be allowed.

Explain the netwok Applications?

Network ApplicationsStudents, faculty, and staff use the WVCC network for the following purposes:■ Application 1, homework: Students use the network to write papers and other documents.They save their work to file servers in the Computing Center and print theirwork on printers in the Computing Center and other buildings.■ Application 2, email: Students, faculty, and administrative staff make extensive useof email.■ Application 3, web research: Students, faculty, and administrative staff use MozillaFirefox or Microsoft Internet Explorer to access information, participate in chatrooms, play games, and use other typical web services.■ Application 4, library card catalog: Students and faculty access the online card catalog.■ Application 5, weather modeling: Meteorology students and faculty participate in aproject to model weather patterns in conjunction with other colleges and universitiesin the state.■ Application 6, telescope monitoring: Astronomy students and faculty continuallydownload graphical images from a telescope located at the state university.■ Application 7, graphics upload: The Art department uploads large graphics files toan off-campus print shop that can print large-scale images on a high-speed laserprinter. The print shop prints artwork that is file-transferred to the shop via theInternet.■ Application 8, distance learning: The Computer Science department participates ina distance-learning project with the state university. The state university lets WVCCstudents sign up to receive streaming video of a computer science lecture course thatis offered at the state university. The students can also participate in a real-time “chatroom” while attending the class.■ Application 9, college management system: The college administration personnel usethe college management system to keep track of class registrations and student records

User CommunitiesTable 10-4 shows the user communities at WVCC. The expected growth of the communitiesis also included. Growth is expected for two reasons:■ New PCs and Macintoshes will be purchased.■ Wireless access will allow more students and visitors to access the network with theirpersonal laptop computers.

Data Stores (Servers)Table 10-5 shows the major data stores (servers) that have been identified at WVCC.

Current Network at WVCCA few years ago, the college buildings were not even interconnected. Internet access wasnot centralized, and each department handled its own network and server management.Much progress has been made since that time, and today a Layer 2 switched, hierarchicalnetwork design is in place. A single router that also acts as a firewall providesInternet access.The logical topology of the current campus-backbone network at WVCC consists of ahierarchical, mesh architecture with redundant links between buildings. Figure 10-5shows the logical topology of the campus backbone.

The router acts as a firewall using packet filtering. The router also implements NAT.The router has a default route to the Internet and does not run a routing protocol. TheWAN link to the Internet is a 1.544-Mbps T1 link.

The physical design of the current network has the following features:■ Buildings are connected via full-duplex 100BASE-FX Ethernet.■ Within buildings, 100-Mbps Ethernet switches are used.■ Every building is equipped with Category 5e cabling and wallplates in the variousoffices, classrooms, and labs.■ The router in the Computing Center supports two 100BASE-TX ports and one T1port with a built-in CSU/DSU unit. The router has a redundant power supply.■ A centralized (star) physical topology is used for the campus cabling. Undergroundcable conduits hold multimode fiber-optic cabling. The cabling is off-the-shelf cablingthat consists of 30 strands of fiber with a 62.5-micron core and 125-microncladding, protected by a plastic sheath suitable for outdoor wear and tear.

Traffic Characteristics of Network ApplicationsThe student assistants in the IT department conducted an analysis of the traffic characteristicsof applications. The analysis methods included capturing typical application sessionswith a protocol analyzer, interviewing users about their current and planned uses ofapplications, and estimating the size of network objects transferred on the network.The students determined that the homework, email, web research, library card catalog,and college management system applications have nominal bandwidth requirements andare not delay sensitive. The other applications, however, use a significant amount ofbandwidth, in particular a high percentage of the WAN bandwidth to the Internet. Thedistance-learning application is also delay sensitive.The users of the weather-modeling and telescope-monitoring applications want to expandtheir use of these applications, but are currently hindered by the amount of bandwidthavailable to the Internet. The graphics-upload application users are also hindered fromsending large files in a timely fashion by the shortage of bandwidth to the Internet.The distance-learning application is an asymmetric (one-way) streaming-video application.The state university uses digital video equipment to film the class lectures in real timeand send the video stream over the Internet, using the Real-Time Streaming Protocol(RTSP) and the Real-Time Transport Protocol (RTP). The remote students do not send anyaudio or video data; they simply have the ability to send text questions while the class ishappening, using a chat room web page.