54-80-50 Implementing a Complex Previous screen David Levin Payoff The company referred to in this article as Servco is an international accounting firm with approximately 100 offices throughout the United States providing tax, audit, and management consulting services. Each practice group within Servco had been using a different computer and networking technology. Servco's management wanted to reorganize the firm from practices into industry focus groups and streamline its information technology environment by maximizing the effectiveness of support personnel and equipment expenditures. Problems Addressed Servco's tax department had IBM personal computers and networks. The audit department used Apple microcomputers and Apple's LocalTalk network. The management consulting department used different brands of microcomputers and minicomputers with many different types of LANs. The administration department used Wang minicomputers with Wangnet, Apple micros with LocalTalk, and IBM microcomputers with both Token- Ring Networks and . Each of Servco's offices had several LANs when only a single LAN, interconnecting all practice and functional areas, was needed. LAN applications included: access to practice information on CD-ROM, access to local data bases, electronic mail, printer sharing, building-to-building communication, and network management. Servco also wanted to build a corporate WAN to connect all its office LANs. Applying Ethernet Technology Servco decided to standardize on a single networking technology. The technologies that were evaluated included Ethernet, Token-Ring, Arcnet, FDDI, and FDDI-over-copper. As Ethernet was the LAN technology that was most widely implemented, Servco decided that Ethernet was the most cost-effective networking alternative for the short term. In the long term, Servco expects to migrate to a 100M bps shielded cable LAN when this technology matures and is truly needed. This design process began after the decision was made to standardize on Ethernet. Ethernet comes in many forms (i.e., thicknet 10BASE5, thinnet 10BASE2, Ethernet 10BROAD36, and twisted-pair Ethernet 10BASE-T). Broadband Ethernet was attractive because some of the larger Servco offices already had Wangnet cable plants installed. Twisted-pair Ethernet was attractive if the network would run on existing Twisted-pair cable. Thicknet and thinnet were the least attractive alternatives owing to doubts about the reliability of a topology network. Hub concentrators were chosen as the primary LAN platform and supplemented by fiber-optic backbone cabling. Servco's requests for proposals (RFPs) were based on detailed technical designs for small, medium-sized and large offices. RFPs went to selected vendors including Bytex, Cabletron, Chipcom, IBM, Synoptics, and Timeplex. After initial evaluation of the vendor bid responses, Servco further evaluated products from Cabletron, Chipcom, and Synoptics. The most important result of the structured bidding process was that the leading vendors provided bids based on discounts averaging between 40% and 50%. The management features built into the hubs also enable substantial cost reduction in the Previous screen network support function. This chapter summarizes Servco's requirements analysis, conceptual design, and detailed planning phases for the new networking platform. The details of the planning process are presented with emphasis on the largest Servco office, which is located in New York City. User Population Exhibit 1 is a summary of the network user population in the New York office. The user population per floor varies from 90 to 150 people with an average of approximately 130 people. Additional ports have to be provided for servers, routers, and printers. The total number of network ports needed in the New York office was projected to be approximately 1,500. Each floor is made up of several groups of people whose work primarily requires information exchange and network connectivity within each group. Each group must also be connected to a backbone network to exchange information outside the group. Intelligent network hub concentrators permit and facilitate this type of connectivity. User Population Summary, Servco, New York Office Stations by Department ------Previous screen Administration- Management Word Floor Audit Tax Consulting Processing Additional ------40th 47 15 45 23 12 39th 28 95 8 17 38th 92 32 11 37th 31 83 7 14 36th 141 14 35th 20 83 24 5 29th 53 30 10 28th 54 61 21 6 27th 49 24 20 4 7 Lower Level 7 26 33 17 12

14 B level 7 Lexington Avenue 33 117 18

Totals: 414 651 147 146 112

(For additional columns, see below)

Floor Total Floor Additional Stations Are in ------40th 142 Administrations 39th 148 Communications 38th 135 37th 135 36th 155 35th 155 29th 132 28th 93 27th 142 Lower 104 Financial reporting Level 95 Administration Central files Facilities 14 Personnel 7

168 1470 (Total)

The New York office consists of people located in two office buildings that are across the street from one another. Servco needed a network design that supported a close link between staff members located in the two buildings. The best way to link both buildings was a bridge or router in each location connected by a T-carrier transmission line. The Hub Concentrator Previous screen Exhibit 2 shows a typical hub concentrator. It includes a chassis, one or more power supplies, and different types of modules. Port or host modules connect a to the network segment. A network segment may consist of a single port module or several port modules connected through the backplane in the chassis. Backplanes may be segregated into separate Ethernet, Token-Ring, and FDDI backplanes. Cabletron combines an older backplane for older modules with a newer backplane for newer modules; they call this their Flexible Network Bus (FNB). Typical Hub Configuration

Cabletron MMAC-M8FNB Hub Concentrator Slots ------8 7 6 5 4 3 2 1 E TPRMIM36 TPRMIM36 TPRMIM36 TPRMIM36 TPRMIM36 TPRMIM36 M M EPIM E Channel C Channel C Isolated Channel B Channel B Channel B

Stations Segment No. Slot Use: ------2. Tax 68 1 3. Tax 1 4. Tax 1 5. Administration-Word Processing 8 2 6. Audit 27 3 7. Audit 3 8. Empty

Bill of Materials ------Item Description Part No. Quantity ------1. 8-slot media access center MMAC-M8FNB 1 2. Power supply PSM-M8 2 3. Ethernet management module EMME 1 4. Multi-Channel 26-port 10BASE-T module TPRMIM36 6 5. Ethernet port interface module-fiber EPIM-F2 1 6. 1-port standalone 10BASE-T TPT-4 0

Hub concentrators support Ethernets, Token-Rings, and FDDI LANs. Most vendors offer different modules for shielded and unshielded cabling. The leading hub modules support three or more network segments per box. All hubs restrict to some extent the mix of network segments and the types of connectivity. Network management modules manage one or more segments depending on the vendor. Router modules connect segments together and pass only traffic for other segments. Bridge modules connect segments but do less intelligent filtering among segments. Retiming modules perform signal regeneration for host modules and may be required when connecting hubs together. Exhibit 2 shows a Cabletron hub fitted with an Ethernet management module and six port modules. Three slots have Cabletron TPRMIM36 26-port 10 BASE-T modules, which form Segment 1 on Channel B, which is used by tax personnel. Slot 5 has an isolated 26-port module used by administrative personnel. Slots 6 and 7 have port modules Previous screen for a third segment on channel C. Exhibit 2 includes a bill of materials for this hub. The hub is a Cabletron module MMAC-M8FNB eight-slot hub with the FNB and redundant power supplies. Cabletron's Ethernet management module provides retiming, management, and bridging if required. Servco chose to turn off the bridging function within the module. A fiber-port interface module is installed in the port module in the fifth slot to connect administrative users from different floors to a Netframe server in the computer room. A Cabletron FOT-F2 one-port standalone fiber-optic transceiver connects the segment 1 users to the buildingwide tax backbone. This hub serves 103 nodes or one-half of all network connections on one floor. Alternative LAN Architectures Four alternative LAN architectures were developed by Servco and are shown in Exhibits 3 to 5. These generic designs differed in the type of router (internal versus standalone) and the choice of backbone (fiber-optic versus ). Exhibit 3 illustrates how the existing coaxial backbone network, which can support five 10M-bps Ethernets, can support the new LAN. Standalone routers connect the multiple LAN segments in each hub. A standalone router in the lower level computer room supports connection to the Lexington Avenue offices and WAN transmission facilities. At the right-hand side of Exhibit 4 is a backbone network design that uses fiber- optic cable and additional hubs to provide what is called a collapsed backbone network. Standalone routers connect each segment to the backbone hubs through fault-tolerant fiber- optic . Redundant backbone hubs may be needed because the backbone hub is a single point of potential failure. Router modules within the hub may be used for connection to the Lexington Avenue offices.

LAN Architecture and Two Backbone Implementations

LAN Using Existing Broadband Coaxial Backbone with Hub- Integrated Routers Exhibit 4 shows a design similar to Exhibit 3 in its use of the existing coaxial cable network. The difference is the routing of network segments to the backbone with router modules within the hub. There are cost and performance advantages in having a router module within the hub. Integrated router modules are less expensive because there is no separate chassis or power supply. The internal router modules for all the leading hub vendors have been developed in partnership with Cisco; these internal router modules provide the same throughput as Cisco's standalone IGS series routers. One advantage of an internal router module is that it may be switched easily from segment to segment. Exhibit 5 shows the collapsed backbone architecture with fiber-optic cable and redundant backbone hubs. The difference from the prior design is use of internal router modules. Internal modules are used on all floors as well as in both backbone hubs.

Previous screen

LAN Using a New Fiber Backbone with Hub-Integrated Routes Previous screen Comparing Hub Bid Pricing In the RPFs for hub concentrator equipment the vendors were asked to bid their products in three specific ways:

á Aggregate pricing for a list of components.

á Pricing for three specific configurations representing small, medium-sized and large offices.

á Pricing for a typical 100-user Ethernet segment. Exhibit 6 summarizes the hub bid responses from the five vendors. Timeplex bid the Lannet product line, which is popular in Europe and less known in the United States. The Timeplex/Lannet proposal was eliminated because of its $415 per port cost for the 100-user Ethernet configuration. Bytex bid its new Maestro hub product, which is very robust in Token-Ring applications. Bytex only recently introduced an Ethernet port module; router development is a joint effort with Wellfleet. The $487 per port cost for the 100-user Ethernet configuration and lack of Ethernet experience were the reasons for eliminating the Bytex bid proposal. Hub Bid Responses Cost Summary New York Main Building ------Previous screen Vendor Total Cost (K) No. ports Cost/port ------Chipcom $348.8 1524 $229 $330.1 1524 $217

Synoptics $330.5 1512 $199 Cabletron $401.0 1572 $255 Bytex Ascom/Timeplex

(For additional columns, see below.)

New York Satellite Mid-Size Office ------Total Total Cost No. Cost/ Cost No. Cost/ Vendor (K) ports port (K) ports port ------Chipcom $35.8 136 $263 $60.4 312 $194 $72.3 312 $232 $54.3 312 $174 $67.6 312 $217 Synoptics $34.0 144 $236 $79.0 324 $244 Cabletron $29.6 144 $206 $139.8 360 $388 Bytex Ascom/Timplex

Small Office Total of 4 Sites ------Total Total Cost No. Cost/ Cost No. Cost/ (K) ports port (K) ports port ------$21.1 68 $310 $466.0 2040 $228 $447.4 2040 $219

$18.0 72 $250 $431.5 2052 $210 $23.2 72 $322 $593.5 2148 $276

100 User Configuration Aggregate Purchase Cost ------Ethernet Total Total and Cost No. Cost/ Cost Token-Ring Cost/ (K) ports port (K) No. ports port ------$23.7 108 $219 $6,937.9 39,600 $175

$23.2 108 $215 $6,933.2 39,600 $175 $26.7 108 $248 $8,606.7 43,200 $199 $52.6 108 $487 $8,243.5 39,600 $208 $41.5 100 $415 $8,358.0 39,600 $211 Previous screen The remaining three vendors were Cabletron, Chipcom, and Synoptics. In the typical 100- user Ethernet configuration the vendor bids ranged between $214 and $248 per port. Chipcom provided two bids for the large-size office fiber configuration: one redundant and one nonredundant. Chipcom provided four bids for the medium-size office with redundant and nonredundant configurations for both twisted-pair and optical-fiber hub interconnection. The $34 per port difference was considered unimportant; therefore, the hub concentrators from Cabletron, Chipcom, and Synoptics were evaluated in greater depth. Comparing Hub Products The comparison of hubs was based on three global criteria:

á Technical functions and features.

á Purchase cost.

á Ownership cost over three years. Exhibit 7 summarizes a functions-and-features comparison for the key technical criteria. First is each product's multi-network support. All vendors offer support for multiple network segments within a single hub. The multi-segment support may involve several modules within the hub connected through the hub's backplane. Alternatively, each module within the hub may function in isolation mode. In isolation mode, the ports on each module comprise a single segment, and multiple modules are not joined through the backplane to form a single segment. Exhibit 7 shows that the maximum number of isolated network segments for Chipcom is 15, for Cabletron 7, and 12 for Synoptics. Hub Functions and Features Comparison Function or Feature Chipcom Cabletron Synoptics ------Previous screen 1. Multi-net support Combinations of network segments 3-0-0 3-0-0 2-0-1 using the backplane (Ethernet-Token 2-3-0 2-1-0 2-1-0 Ring-FDDI) 2-0-1 2-0-1 1-2-0 1-3-1 1-2-1 0-0-2 0-3-2 0-2-1 0-2-0 0-0-4 0-0-3 1-1-1 0-7-0 0-3-0 Maximum number of network segments in 15 7 12 isolation mode

2. Node flexibility Module switching capability Yes Yes Yes Maximum slots per hub 17 8 13 Maximum ports per slot 12 26 12 Module adjacent limitation No Yes No Port switching capability Yes No No

3. Hub interconnection Fiber-optic cable Yes Yes Yes Twisted-pair cable Yes Yes Yes Broadband coaxial cable Yes Yes* Yes*

4. Network Management Level 1: LED indicators Yes Yes Yes Level 2: Asynchronous terminal Yes Yes Yes Level 3: Microcomputer-based GUI Yes Yes Yes Level 4: SunNet manager Yes Yes Yes Level 5: Artificial Intelligence- No Yes No based rules

5. Internal routers ranking Ethernet internal/serial Yes Yes Yes Ethernet internal/internal Yes No No Ethernet internal/external Yes Yes Yes Token Ring internal/serial No No No Token Ring internal/internal No No No Token Ring internal/external No No No

*Broadband product not provided by vendor, support provided through third party products

The multi-net support comparisons are based on the Ethernet, Token-Ring and FDDI segments supported simultaneously. Synoptics supports a maximum of three segments, including one Ethernet segment, one Token-Ring segment, and one FDDI segment (1-1- 1). Other multi-net combinations include two Ethernets with one Token-Ring (2-1-0) or two Ethernets with one FDDI (2-0-1). Synoptics' hub supports only two Token-Ring networks when no Ethernet or FDDI segments (0-2-0) are installed. Two FDDI segments are supported with no Ethernet and no Token-Ring segments (0-0-2). Cabletron supports three Ethernet segments (0-0-3), three Token-Ring segments(0- 3-0), or three FDDI segments (0-0-3). If two Ethernet segments are installed, the hub can support one additional Token-Ring (2-1-0) or one additional FDDI segment (2-0-1), but not both. If two Token-Ring segments are used, the Cabletron hub can support one additional Ethernet segment and one additional FDDI segment (1-2-1). Cabletron's multi- net support is considered superior to Synoptics' multi-net support. Chipcom supports three Ethernet segments (3-0-0), seven Token-Ring segments(0-7-0), or four FDDI segments (0-0-4). If two Ethernet segments are installed, the hub can support three additional Token-Rings (2-3-0) or one additional FDDI segment Previous screen (2-0-1). If one Ethernet segment is used, the Chipcom hub can support three additional Token-Rings and one additional FDDI segment (1-3-1). If no Ethernet segments are used, the Chipcom hub supports three Token-Ring segments and two additional FDDI segments (0-3-2). Chipcom's multi-net support is better than Cabletron and Synoptics. Node Flexibility and Hub Interconnection Exhibit 7 also compares node flexibility and hub interconnection alternatives. Cabletron, Chipcom, and Synoptics support host module switching, whereby an individual module may be changed among network segments. The maximum number of slots available for modules is 17 for Chipcom, 8 for Cabletron, and 13 for Synoptics. The maximum number of Ethernet ports per slot is 12 for Chipcom, 26 for Cabletron, and 12 for Synoptics. When using the hub's backplane to connect multiple modules into a single segment, Cabletron requires that these modules use adjacent slots. If a middle module within a network segment is removed, the adjacent modules go into loopback and the network segment fails. Chipcom and Synoptics do not have this module adjacency limitation. Chipcom offers port switching capability: through the use of software, individual ports within a module can be connected to form segments. Chipcom retimes the signal at the port level, unlike Cabletron and Synoptics, which retime with common circuitry at the host module level. Cabletron and Synoptics do not offer port switching. The advantage of port switching is the ability to reconfigure network segments without the manual intervention required to change patch panel cables in the closet. There are five ways to interconnect hubs: fiber-optic cable, thickwire coaxial cable, thinwire coaxial cable, broadband coaxial cable, and twisted-pair cable. Cabletron, Chipcom, and Synoptics offer products for interconnecting hubs using fiber, thickwire, thinwire, and Twisted-pair cable. All three vendors support hub interconnection using Broadband coaxial cable, but Chipcom offers products of its own for this, and Cabletron and Synoptics require the use of third-party products. Comparing Network Management Facilities Comparisons between the hub's network management capabilities are based on five levels of network management facilities. In level one, indicator lights in the hub display traffic activity and faults on specific ports. Cabletron, Chipcom, and Synoptics provide this facility on their respective hub products. Level-two network management is the ability to connect a terminal(or personal computer with terminal-emulation software)to the hub for command input and configuration listings. Chipcom's level-two network management capability is considered somewhat better than the capability offered by Cabletron and Synoptics. The user interface is easier to use and the configuration listings are more comprehensive. Because an older personal computer may be used as a network management workstation, there is little cost for this capability beyond the management module itself. Level three uses a microcomputer with Graphical user interface software to provide a comprehensive management environment. The microcomputer is typically an 80386- or 80486-based machine with Santa Cruz Operation UNIX operating system software. This level of network management is offered by all three vendors. The user sees a graphical representation of the hub concentrator along with the logical node topology within each segment. The level-three network management capability offered by all three leading vendors is considered equally comprehensive and far exceeded Servco's current Previous screen requirements. Level four uses a Sun workstation with SunNet Manager operating software to provide a standardized Graphical user interface network management environment. The advantages of the SunNet Manager environment include a more powerful workstation platform and the ability to collect network management information through software written by other vendors. Level-four network management should be restricted to a few locations, including the corporate network control center and, in the future, the 10 largest offices. All three vendors support the SunNet Manager network management environment with roughly the same level of capability. Level-five network management uses rule-based software to suggest the probable cause of a specific network problem and is offered only by Cabletron. This network management environment is similar to such other products as IBM's NetView, Digital's DECmcc, and AT&T's Unified Network Management Architecture. Like SunNet Manager, level-five network management can provide diagnostic information for components other than the hubs (e.g., for network interface cards, routers, data service units, and transmission channels). The disadvantages of this level of network management are its high cost and the need for a programming staff to properly use this tool. Cabletron's level-five network management facility is admirable, but there was little foreseeable need at Servco for this type of facility. Comparing Internal Routing Capabilities Network segments are connected together using repeaters, bridges, routers, and gateways. Repeaters combine two network segments into one network segment. Bridges and routers connect two network segments together but filter traffic between segments. Routers filter traffic more intelligently than bridges. Because bridges typically do not prevent Apple broadcast packets from flooding other network segments, bridges were not recommended for Servco. Routers create fire walls between network segments and were recommended for Servco. Gateways link network segments that use the same Network operating system and a single network protocol (e.g., 's IPX/SPX). Routers link segments that use many network protocols. Servco needed to support Novell's IPX/SPX, Apple's AppleTalk, and the Transmission Control Protocol/Internet Protocol. Servco could choose either internal hub router modules, which are installed in the hub, or standalone routers, which are external to the hub. Internal router modules are less expensive and their performance equals standalone routers. Exhibit 7 summarizes the comparison of router modules offered by the three hub vendors. All vendors' external routers are rated equal because none make these products. External routers are sold by Wellfleet, Cisco, 3Com, Digital, ACC, and others. Wellfleet and Cisco are the leading vendors. At the time of the comparison none of the hub vendors offered internal router modules for connecting Token- segments, although Cabletron and Chipcom have since introduced these. All three companies' internal Ethernet router modules were jointly developed with Cisco. These internal router modules typically provide the same throughput as the equivalent standalone Cisco IGS router. If internal routers are installed in the hubs, then any standalone routers used should be from the same vendor. At present, router modules from different vendors do not communicate effectively owing to their proprietary router protocols. A common router protocol called router information protocol may be used to link different vendors' routers, but this protocol is very inefficient. Newer router protocols, such as OSPF, promise the Previous screen ability to efficiently link different vendors' routers in the future. The standalone routers should be one of several models from Cisco(for compatibility with the internal routers). This restriction was not considered a serious limitation because Cisco's router product line is considered viable. Cisco provides effective technology for limiting Apple messages, for supporting IBM mainframe access, and Cisco is the leading router vendor. Hub vendors were compared based on three types of internal router modules: Ethernet internal-to-serial, Ethernet internal-to-internal, and Ethernet internal-to-external. An Ethernet internal-to-serial router module links an Ethernet segment within the hub to a transmission line. This transmission line is connected to the router through an EIA-232 interface when speeds less than 19.2K bps are acceptable and through a V.35 interface when speeds greater than 19.2K bps are necessary. All three vendors offer internal-to-serial router modules and all are considered roughly equivalent in their capabilities. An Ethernet internal-to-internal router module links two Ethernet segments within the hub. Cabletron and Synoptics do not offer internal-to-internal router modules, and Chipcom is considered superior in offering this capability. An Ethernet internal-to-external router module links an Ethernet segment within the hub to an Ethernet segment outside the hub. All three vendors offer this product and are considered equivalent in this regard. An internal-to-external router module uses the attachment unit interface connector to attach the external Ethernet network segment. Comparing Maximum Cable Distances Exhibit 8 compares the maximum cable distance between workstation and hub for Ethernet connectivity, Token-Ring connectivity at 4M bps, and Token-Ring connectivity at 16M bps. The maximum cable distances vary by cable type. Three cable types have been analyzed:

á Level 5 shielded cable (the new office standard).

á Level 5 unshielded cable (installed in some offices).

á Level 3 unshielded cable (installed in older offices). Maximum Cable Distance Comparison Maximum Cable Distance (ft) ------Previous screen Chipcom Cabletron Synoptics ------Ethernet Networking Ethernet on type 1 STP 980 410 800 Ethernet on level 5 UTP 490 650 600 Ethernet on type 3 UTP 410 410 330 Token-Ring Networking 4M-bps Token-Ring on level 5 STP 900 980 1100 4M-bps Token-Ring on level 5 UTP 330 820 1000 4M-bps Token-Ring on type 3 UTP 330 410 330 16M-bps Token-Ring on level 5 STP 410 490 600 16M-bps Token-Ring on level 5 UTP 330 390 470 16M-bps Token-Ring on type 3 UTP 330 330 330

Notes: 1. STP Shielded Twisted-pair 2. UTP Unshielded Twisted-pair

In cases where the hub vendor offers different modules for shielded and unshielded cable, the module for unshielded cable was analyzed per the vendors' recommendations. Maximum cable distance is an important criteria for several reasons. The longer the cable distance supported, the more reliable the connectivity when shorter cables are employed. Each connection in the network is equivalent, in terms of signal loss, to between 20 and 50 additional cable feet, depending on the type and quality of connection. Longer allowable cable distances therefore mean greater flexibility in terms of the allowable number of network connection points. Because some of Servco's offices have communications closets that are not centrally located, resulting in cable runs in excess of 450 ft, Servco wanted hub concentrators that would support workstation connections beyond the 330-ft cable distances cited in the IEEE 10BASE-T cabling guidelines. Chipcom offers the longest distance for Ethernet connectivity over shielded level 5 cable, Servco's new standard environment, at 980 ft. This distance considerably exceeds the 10BASE-T standard guideline of 330 ft. Chipcom's maximum cable distance exceeds Synoptics' maximum of 800 ft and Cabletron's maximum of 410 ft. Cabletron offers the longest distance for Ethernet connectivity over unshielded level 5 cable at 650 ft. Synoptics' maximum distance is close at 600 ft. Chipcom's maximum of 490 ft is less. Chipcom and Cabletron both support level 3 unshielded cable up to 410 ft with Synoptics supporting only 330 ft. Token-Ring connectivity at 4M bps on level 5 shielded cable is considered equal among the three vendors, ranging from 900 to 1100 ft. Chipcom is somewhat deficient with level 5 unshielded cable. Cabletron is somewhat better with level 3 cable. Synoptics supports the longest cable runs for 16M bps on shielded and unshielded level 5 cable. All three vendors are equal when using level 3 unshielded cable. In comparing cable distances, Chipcom was rated first, Synoptics was rated a close second, and Cabletron a close third. Summary Hub Comparison Previous screen The three leading vendors were compared and ranked based on key technical selection criteria as shown in Exhibit 9. Synoptics was the weakest of the three leading vendors. The Synoptics hub will not support three Ethernet segments within a single hub, a requirement considered key to Servco's new network environment. Synoptics does not offer an Ethernet internal-to-internal router module. Technical Criteria for Vendor Evaluation

Technical Criteria Chipcom Cabletron Synoptics ------Multi-net support 1 2 3 Node flexibility 1 3 2 Hub interconnection 1 2 3 Network management 2 1 3 Routers 1 2 3 Maximum cable distances 1 3 2

Using cost criteria, technical criteria, equipment already owned, and existing client relationship produced the vendor ranking shown in Exhibit 10. Servco considered the Chipcom solution the best technical solution. Servco had some Synoptics equipment already installed, which both Chipcom and Cabletron offered to replace at minimal cost. The most important criteria, however, was not technical. Servco's existing client relationship was more important, provided the client's product could do the job. Servco judged Cabletron equipment acceptable from a functional point of view and wanted to use the products of a client whenever possible. Overall Ranking of Hub Vendors

Cost and Technical Criteria Chipcom Cabletron Synoptics ------Acquisition cost 1 3 2 Cost of ownership 1 2 3 Technical criteria 1 2 3 Equipment already installed 3 2 1 Existing client relationship 3 1 2

Creating a Backbone Network There were two viable choices for creating a backbone network within the New York site: use the existing broadband coaxial network or install new fiber optic cabling. Servco's existing Broadband coaxial backbone had many channels that were unoccupied. Ethernet modems could be installed in each data communications closet to connect hub router modules to the backbone network. Servco evaluated the cost/benefit ratio of each backbone alternative. The initial cost of using the existing Broadband coaxial network included Ethernet modems at $40,000, cabling and supplies at $5,000, and installation of $10,000. The preferred Ethernet modem was Chipcom's Ethermodem IV. The total cost of using the existing backbone was estimated to be $55,000. The second alternative was installing fiber-optic cabling from each floor to the lower level computer room. The cost of fiber-optic hub equipment was estimated at $40,000. The cost of installation was estimated at $90,000. Electrical conduit work was Previous screen required costing $35,000. The cost of engineering and component installation was estimated at $20,000. The total cost for the fiber backbone was $185,000 versus $55,000 if the existing Broadband network was used. The advantages of the fiber-optic backbone were a higher quality link and the ability to upgrade to 100M-bps FDDI in the future. The advantages of the coaxial backbone were the reduced expense and the ability to support video applications, including video conferencing. Servco elected to perform some upgrades to the existing coaxial backbone, in particular by purchasing Ethernet modems to meet short-term needs, but for the long-term, decided to install the fiber backbone shown in Exhibit 11. It spans 11 floors, including the lower level and the lower B level. The cost of the fiber backbone network was not considered excessive in view of the importance of the network to the business and its suitability for a future 100M-bps FDDI network.

Servco New York Office Fiber Backbone Schematic

The Implemented LAN Architecture The Park Avenue office uses a fiber-optic and collapsed backbone network with external routers. Each floor has two hubs supporting several network segments except for the twenty-ninth floor, which has a single hub. A standalone router located in the lower level computer room provides access to the Lexington Avenue location and the corporate WAN for all 11 floors. Network segments serving audit, management consulting, and administration users are supported by port modules within the hub concentrator. These segments are extended through the fiber-optic backbone cabling to their respective servers in the computer room. Tax file servers are located on the thirty-fifth and thirty-seventh floors in satellite computer rooms. Fiber-optic backbone cabling connects the file server to the building-wide tax backbone network. Exhibit 12 shows Servco's backbone network segments at the Park Avenue site. There are four backbone network segments: the tax backbone, the administrative backbone and management consulting backbone, the audit backbone, and the officewide backbone. a variety of servers are connected to the backbone network segments, including file servers, communications servers, electronic mail post office servers, and electronic mail gateway servers. Remote Lanview are attached to the backbone segments to support network management functions. Tape backup unit workstations are also attached supporting backups of different file servers on each backbone segment. The standalone Cisco AGS+ router connects each backbone and the remote transmission links.

Servco Park Avenue New York, LAN Backbone Detail Exhibit 13 shows Servco's backbone network segments at the Lexington Avenue site. The tax backbone segment supports connection of the four tax file servers. The communications gateway is connected directly to one of the tax file servers. The officewide backbone segment supports several file servers, an officewide post office server, network attached modems, electronic mail communications servers, and two CD-ROM file servers.

Previous screen

A Cisco AGS+ router connects the two backbone segments and the T1 transmission link Previous screen to the Park Avenue office.

Servco Lexington Avenue New York Office, LAN Backbone Design

Building a Metropolitan Area Network After building the integrated LAN for Servco's different metropolitan New York locations, the different LANs needed to be connected together. Exhibit 14 shows a schematic of Servco's metropolitan area network, which serves its offices in the metropolitan New York area.

Servco New York Metropolitan WAN Servco's headquarters site served as the hub for the metropolitan area network. Three sites were connected to headquarters through a DS-0 channel within an existing T1 link used for voice communications. The Lexington Avenue site was connected to the Park Avenue site with a dedicated T1 channel because of the high volume of traffic between sites and the low cost of the high-speed link. Author Biographies David Levin David Levinis president of Netcomm, Inc., a Manhattan-based firm providing computer and communications engineering and management consulting. Previously he worked for Chase Bank, Bankers Trust Co., and Donovan Data Systems.