Thtcle coax and other cable systemsfor Ethernet
`
`The Apple Ethernet AUI Adapter enables you to connect a device equipped with an
`Apple Ethernet port to standard Ethernet transceivers for thick coax, fiber—optic, and
`other Ethernet media types. The AUI Adapter will work with external transceivers from
`all companies following the 802.3 AUI (Attachment Unit Interface) specification.
`
`Ethernet cable systemforfiber-optic and thick coax
`
`.II
`
`
`
`Transceiver
`
`Transceiver
`cable
`
`Electrical plug
`
`Chapter 6 Network Types
`
`93
`
`PETITIONERS Ex. 1020, part 2, p. 25
`
`

`
`AppleTalk over Token Ring: TokenTalk
`
`A TokenTalk network transmits AppleTalk protocols over industry-standard (IEEE 802.5)
`Token Ring networks. The growing popularity of Token Ring is the result of its
`compatibility with standard cabling installations and its role in IBM’s Systems Application
`Architecture (SAA), making it ideal for large business installations.
`Providing transmission rates of either 4 megabits per second (Mbps) or 16 Mbps,
`Token Ring can use either shielded twisted—pair cable or unshielded twisted—pair cable. A
`single network can connect up to 260 devices.
`Each device on a Token Ring network is connected to a MAU that is usually located
`in a wiring closet. A typical MAU provides eight ports for connecting network devices. As
`your network grows, you can add MAUs to support more devices,
`You need TokenTalk software and a Token Ring interface card for each computer
`that you want to attach to the network. To connect members of the Macintosh H family
`of computers to Token Ring networks that operate at 4 Mbps, Apple provides the
`TokenTalk NB Card. This card connects to IBM Type 1 cable (shielded twisted—pair).
`Other vendors provide media filters for attaching to IBM Type 3 cable (unshielded
`twisted—pair). You may also purchase interface cards from other companies that allow
`you to connect a Macintosh SE or SE/50 to a Token Ring network.
`
`
`
`94
`
`Part2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 26
`
`

`
`Conclusion
`
`In this chapter, you’ve learned about the different network types that are supported by
`the AppleTalk network system—LocalTalk, Ethernet, and Token Ring. These network
`types target the needs of varying network environments. The following table enables
`you to compare the features of these network types. Note that AppleTalk protocols can
`
`also operate on other types of networks, such as ARCnet, LANSTAR, and IBM baseband
`networks. For more information on these additional network types, refer to the sources
`
`listed in the Appendix.
`
`Table 6-1 A comparison of network types
`
`Medium
`
`Transmission
`rate
`
`Maximum
`number of
`
`Maximum
`
`Ease of
`
`Topology
`
`devices
`
`length
`
`installation
`
`LocalTalle
`
`Shielded
`
`250.4 Kbps
`
`Bus
`
`32
`
`1000 ft.
`
`Easy
`
`twisted—pair
`
`Unshielded
`
`twisted-pair
`(phone wire)
`
`250.4 Kbps
`
`Bus
`Passive star
`
`20-40
`Varies
`
`2000 ft.
`4000 ft. (sum
`of branches)
`
`Easy
`Requires installer
`
`Active star
`
`254
`
`5000 ft./branch Requires installer
`
`Infrared light
`
`230.4 Kbps
`
`NA
`
`128 per
`transceiver
`
`Easy
`
`Transceivers
`must be within
`
`70—ft. diameter
`
`Ethernet
`
`Thick coaxial
`
`10 Mbps
`
`Thin coaxial
`
`10 Mbps
`
`Twisted—pair
`
`10 Mbps
`
`Fiber optic
`
`10 Mbps
`
`Bus
`
`Bus
`
`Star
`
`Bus
`
`100/segment
`1024/network
`
`40/segment
`1024/network
`
`1024
`
`1024
`
`Token Ring
`
`Shielded
`
`twisted—pair
`
`Unshielded
`
`twisted-pair
`
`4/16 Mbps
`
`Star-wired ring
`
`260/ring
`
`4/16 Mbps
`
`Star-wired ring
`
`72/ring
`
`8250 ft.
`
`Requires installer
`
`5300 ft.
`
`550 ft. from
`hub to device
`
`Easy with Apple
`Ethernet product
`
`Requires installer
`
`14,256 ft.
`
`Requires installer
`
`990 ft. from
`MAU to device
`
`Usually requires
`installer
`
`550 ft. from
`MAU to device
`
`Usually requires
`installer
`
`Chapter 6 Network Types
`
`95
`
`PETITIONERS Ex. 1020, part 2, p. 27
`
`

`
`Extending and connecting networks-
`
`When designing your network, you may find that you need to extend a single network
`
`or divide the network into two or more connected sabnetworles. Connection devices
`
`such as repeaters, bridges, routers, and gateways (discussed fully in the next section)
`
`extend networks or provide the link between individual networks, enabling many users
`
`to communicate and share resources with one another.
`
`The following situations commonly call for extending or connecting networks:
`
`I Enlarging a networle that has reached its maximum length or number of devices. If
`you’ve reached the specified device or cable length limits of a network, you may
`
`need to extend the network. For example, if you’re using LocalTalk cable and need
`to extend the cable beyond the specified 1000-foot limit, you would need to use a
`connection device.
`
`I Linleing two or more existing networles in your organization.
`
`It’s not unusual for
`
`networks to be installed in an organization for different reasons and at different
`
`times. The result? Separate networks that don’t communicate. Connection devices
`
`can link these networks together, allowing users on each network to access network
`services on the entire internet.
`
`I Connecting oliflerent networle types or networles using differentprotocols. A common
`reason for connecting networks is to link different network types, such as LocalTalk
`
`and Ethernet, each using different connection methods and transmission media. Or
`
`you may need to link your AppleTalk network to a network running an entirely
`
`different set of protocols, such as DECnet or TCP/IP.
`
`I Maintaining a satisfactory level of networle performance. In a high—traffic network,
`
`performance can be increased significantly by dividing the network into
`subnetworks, each with a low demand for the resources of another subnetwork. A
`
`logical way to divide an existing network is along natural divisions within the
`
`organization. For example, networks are commonly divided by department or by
`
`groups that have shared requirements. By partitioning the network into largely self-
`
`contained subnetworks, you can minimize the amount of traffic flowing between
`
`them and maintain higher levels of performance on each subnetwork.
`
`Chapter 7 Design Guidelines 107
`
`PETITIONERS Ex. 1020, part 2, p. 28
`
`

`
`Isolating a single group generating high trafific. When one group of users generates
`a large amount of network traffic, performance may decline on the entire network.
`For example, several users performing frequent, high-volume printing and file
`sharing can cause network congestion for all other users on the same network.
`
`When designing your network layout, you can plan for such high-traffic groups
`ahead of time by isolating these users in a network of their own. If your network is
`already in place, you can use the same traffic—isolation technique, dividing one large
`network into two smaller networks.
`
`Accommodating different user requirements. If users’ needs for network resources
`vary greatly, you may want to consider creating two networks linked by a connection
`device. In this way, the special interests of each group may be better satisfied.
`
`Restricting access to sensitive information. You may decide that sensitive or
`important inforn1ation—such as product development plans or personnel fi1es—can
`be better safeguarded and supervised by placing the information in a separate
`network. Even though users in other networks can access devices on the “secure”
`network, you can set up certain servers that have restricted access.
`
`Creating zonesfor efiicient network organization. Zones are logical divisions
`within an internet that enable an administrator to balance the number of network
`
`services presented to users. See “Dividing Your Internet Into Zones” later in this
`chapter for a discussion of zones.
`
`Which connection device do you need?
`
`Four kinds of devices are used to extend or connect networks:
`
`repeaters
`
`bridges
`
`routers
`
`gateways
`
`The device you choose depends on what kind of connection services you need, as
`described in the following sections.
`
`108 Part 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 29
`
`

`
`Repeaters
`
`A repeater is a piece of hardware about the size of a modem. It is commonly used to
`add another length of cable to a network, extending the cable beyond its recommended
`maximum length. As a transmission signal travels through the network cable, the signal
`becomes weakened. The repeater amplifies and retransmits this signal, effectively
`enabling it to travel beyond the normal limitations of the cable.
`A repeater can be very helpful if, for example, you have a few users on a LocalTalk
`network whose offices are isolated from the rest of their group, requiring a total cable
`
`length greater than the 1000 feet allowed by LocalTalk. The repeater enables you to
`connect those users to the network rather than creating another, separate, network.
`
`You can also use a repeater to add devices to a network cable; however, there are
`two important points to keep in mind. One, repeaters do not isolate trdjftc. When you
`add a repeater to your network, the result is one larger network. The traffic that results
`from adding more devices can quickly degrade performance on the entire network. Two,
`be aware of the recommended device limitations of each network type. It would be
`
`unwise, for example, to use a repeater to go well beyond the 52-device limitation of
`LocalTalk (using the LocalTalk cable system), since performance would rapidly suffer.
`
`However, if you’re using Ethernet, which can accommodate a large number of devices, a
`repeater may be a good choice for adding more devices.
`
`7%‘ Repeaters enable a cable to be extended
`5*‘ beyond its recommended length.
`
`
`
`Chapter 7 Design Guidelines 109
`
`PETITIONERS Ex. 1020, part 2, p. 30
`
`

`
`Bridges
`
`A bridge can be used to join two networks of the same network type (such as two
`Ethernet networks or two Token Ring networks). The networks can use different types
`of media, such as fiber—optic or coaxial cable. Note that there are currently no bridges
`available to connect LocalTalk networks; routers are used instead (see the next section
`
`for a discussion of routers).
`
`Unlike a repeater, which simply retransmits all data onto the connected cable
`segment, bridges can interpret data addresses. This means that bridges can isolate traffic
`on each network, sending only those packets across the bridge specifically destined for
`the other network. (Note that bridges do not typically isolate broadcast traffic, which
`results from such activities as using the Chooser.)
`Bridges can be dedicated, self-contained devices or computers running appropriate
`bridging software. Because the networks connected by a bridge are not identified by
`network numbers or zone names (unlike routers), installing and administering a bridge is
`usually quite easy. Bridges provide administrators with information about network
`activity levels and error statistics, which are helpful in monitoring the network.
`
`Bridges are used to connect networks together.
`Devices see thepreviously separate networks
`as one single, larger networie.
`
`
`
`110 Part 2 Planning Your Network
`
`
`
`PETITIONERS Ex. 1020, part 2, p. 31
`
`

`
`Connection devices and the OS] model
`
`Connection devices perform network functions that involve different layers in the hierarchical 081 model.
`
`In this hierarchy, as you may recall from Chapter 2, each layer represents a separate level of network
`
`function. Network connection devices perform functions that may involve one or more of these layers. For
`
`example, repeaters—very simple hardware devices—make use of the protocols in just the physical layer,
`
`whereas gateways—sophisticated translators between different protocol architectures——use the greatest
`
`range of networking protocols.
`
`Functional layers
`ofOSI model
`
`Physical
`
`Application
`
`Presentation
`
`Session
`
`Transport
`
`Network
`
`Data link
`
`Repeater
`
`Bridge
`
`Router
`
`Gateway
`
`Routers
`
`Routers can connect networks of the same network type (such as two LocalTalk
`networks) or of different network types (such as an Ethernet network and a Token Ring
`network). Routers enable the connected networks to retain separate identities with their
`own unique network numbers, and they can selectively route data along the most
`efficient path possible. This ensures faster traffic flow and can automatically provide for
`detours if a connection is broken along the path.
`
`Chapter 7 Design Guidelines 111
`
`PETITIONERS Ex. 1020, part 2, p. 32
`
`

`
`Routers are often used to isolate areas of high traffic from lower-traffic areas for
`
`optimum network performance. They also enable you to partition an internet into zones,
`which make it easier for users to locate and access network services. In addition, routers
`(like bridges) provide administrators with information about network activity levels and
`error statistics, which are helpful in monitoring the network.
`Routers can be hardware- or software~based. A hardware-based router is a dedicated
`
`box whose only function is routing. It is generally a self-contained device, without a
`monitor or keyboard, designed to be used only as a router. A software-based router
`operates on a general—purpose computer such as a Macintosh. It can be used as either a
`dedicated or nondedicated router, depending on the level of performance your network
`requires. A dedicated router is a computer which, when running routing software, is
`used for no other purpose. A nondedicated router operates on a computer that can be
`used concurrently for other network services as well. If your router is sending large
`amounts of traffic to other networks or if you need the highest possible performance
`from your router, a dedicated router is the better choice.
`
`Each router on an internet maintains a routing table (shown in the following figure)
`that lists all networks and routers in the internet. The routing table enables routers to
`determine the most efficient route for each packet of data.
`
`Network Information for Router: HppleTalk Internet Houter
`
`Packets Routed:
`
`Recent itctivitg Rate:
`
`Network Reiiabiiitg:
`
`Recent Network Error Rate:
`
`10 zones, 9 networks sorted bu:
`Distance
`Forwarding Port
`4:)
`
`Looa1Taik
`
`Next Router
`
`Routing table
`information
`
`Network Range
`40
`61
`62
`63
`
`35
`25 -
`55
`45 —
`2260 - 2203
`2300 - 2303
`53 -
`60
`
`Zone Name
`Accounting
`LocaiTaik Zone
`LocaiTal k Zo no
`Loca1Ta1k Zone
`
`Marketing...
`Pubiications
`TTLabZone1
`TTLabZone5
`Zone1__.
`
`IONJNIDDDNII-'
`
`The routing table serves as a logical map of the internet. It lists the network number
`
`(or network range) for each network, associated zone names, the address of the next
`
`112 Pom.‘ 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 33
`
`

`
`
`
`router in the path to a given destination network, and the distance to other networks,
`measured in hops. A hop is a unit count between networks on an internet, and means
`“one router away.” Each router uses this routing table to determine where (and whether)
`
`to forward a data packet.
`
`A
`
`4
`
`7
`
`'2
`
`4
`
`. Device A is 3 hops (routers)
`awayfromdeviceB.
`
`''.,.
`
`U
`
`' .
`
`. ' l
`
`0o
`
`Router
`
`I1
`
`c
`
`00
`
`I
`
`\
`
`_.'
`
`4
`
`, I
`
`.
`
`I
`
`I
`
`I
`
`‘ Y
`
`.
`
`B
`
`Routers can be used in the following ways.
`
`I
`
`To connect local rtetworles: A local router is used to connect two or more networks
`
`in close proximity.
`
`‘
`
`I
`
`To connect remote networ/es: A half-router (or remote router) is used to connect
`
`two or more remote networks over a long-distance telecommunications link. Each
`
`network is connected to a router, which in turn is connected to a modem.
`
`I
`
`To cormect rtetwor/es to at baclebone; A backbone router can be either a local router
`
`or a half—router. The router is used to connect networks through a backbone
`network, allowing you to link networks in a nonserial manner. This configuration
`
`minimizes the number of hops between networks (a network is no more than two
`hops from another network) and thereby improves performance. (See “When to Use
`a Backbone” later in this chapter for more information on backbone networks.)
`
`Chapter 7 Design Guidelines 113
`
`
`
`PETITIONERS Ex. 1020, part 2, p. 34
`
`

`
`Arouter maintains a logical map ofnetworles in an intemet
`1 and can route data along the most efficlentpath.
`
`Local networles
`
`Remote networks
`
`114 Part 2 Planning Your Network
`
`
`
`PETITIONERS Ex. 1020, part 2, p. 35
`
`

`
`Because routers are inherently more intelligent than bridges, they do require more
`
`administration time. When you set up a router, you must identify each connected
`network with a networle number or network range (see “Assigning Network Numbers
`
`and Ranges” later in this chapter), and you also need to specify zone names. Routers
`
`generate more overhead traffic than bridges since they are continually updating the
`
`routing tables of all routers in the internet.
`
`Where to place a router
`
`Each internet is, in some ways, unique. The connected networks can differ in size,
`layout, and type. As long as a router is properly connected, there are no absolute rules
`that govern its placement in the internet. You can place a router at any point along the
`length of a network. It isn’t necessary to connect networks end—to—end with a router
`
`between each network. The figure below shows examples of possible router locations.
`
`You can place a router at anypotnt
`along the length of a networle.
`
`Chapter 7 Design Guidelines 115
`
`PETITIONERS Ex. 1020, part 2, p. 36
`
`

`
`Creating redundant routes
`
`Where possible, try to create duplicate routes to each individual network in an internet.
`Using this technique, called redundant routing, you can prevent networks from getting
`cut off from the rest of the internet if a break occurs on one of their access routes.
`
`In the figure below, a router has been added to the internet, resulting in redundant
`connections between networks. The additional router provides an alternate access route
`between any two networks, thereby improving network reliability; it also reduces the
`number of hops between some of the networks.
`f
`Be aware that if you create redundant routes with the same number of hops,
`troubleshooting can be more difficult, because it may be hard to figure out which path
`
`the packets are following.
`
`116 Part2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 37
`
`

`
`Dividing your internet into zones
`
`During router setup, you can arrange devices into logical groupings called zones that
`conceptually partition the internet. There are two main reasons to create zones: to make
`it easier for users to locate devices, and to facilitate the creation of departmental
`workgroups that may reside on different physical networks.
`Internets can contain many hundreds of shared resources, such as printers and file
`
`servers. If users had to sort through a list of all these devices, the process would be
`
`overwhelmingly long and cumbersome. Dividing the internet into zones is a much
`
`preferred alternative, enabling users to View the devices within a single zone rather than
`those on the entire internet.
`
`Zones also enable administrators to group users into a single zone regardless of
`where they are physically located. A group of users assigned to the same zone can
`efficiently locate the network resources in that zone. This is convenient in situations
`where members of a department or workgroup reside in different physical areas. This
`
`also lets administrators change zone groupings without having to change any physical
`connections.
`
`If you do set up users so that they are in the same zone, but reside on different
`networks, be aware that this may cause areas of high traffic on the internet. For example,
`
`in the following diagram, if a user in Zone B on the Token Ring network needs to access
`the file server in Zone B on the LocalTalk network, this will cause traffic on both the
`
`intervening Ethernet network and the LocalTalk network. Especially in large internets,
`you should consider grouping all the users on one network into a single zone to isolate
`traffic within that network.
`
`Zones have no physical boundaries or size limits. A zone can include one device,
`several devices, or all of the devices on the entire internet.
`
`Chapter 7 Design Guidelines 117
`
`PETITIONERS Ex. 1020, part 2, p. 38
`
`

`
`Users connected to dzflerent physical networks
`can belong to the same zone.
`
`
`
`
`
`¢
`' /
`Zone 3
`
`¢
`
`I
`
`Zone B
`
`w
`
`/ F
`
`ile server
`in Zone B
`
`Zone B
`
`Zone A
`
`Q
`Zone A
`
`Ethernet _
`
`.0
`
`Printer
`
`in Zone A
`
`Loca1TaIk‘ . '
`
`Zone names and zone lists
`
`When you set up a router, you can associate one or more zone names with each
`network connected to the router. The name identifies the zone to users through the
`Chooser and is used in various router displays. It’s a good idea to keep zone names short
`and simple and to make them meaningful to users. A common method is to use
`departmental names or locations, such as Personnel, Engineering, or Finance East and
`Finance West.
`
`118 Part 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 39
`
`

`
`A single LocalTalk network can be associated with only one zone name; all of the
`
`devices on that network belong to this one zone. A single Ethernet or Token Ring
`
`network can have multiple zone names, which means that the devices on the network
`
`can belong to different zones. These multiple zone names are referred to as a network
`
`zone list, which contains one or more zone names available to nodes on that network.
`
`During router setup, you specify the default zone for each device. You (or any other
`user) can change the zone to which a device belongs through the Network control panel
`
`(or the Control Panel if you’re using Macintosh system software earlier than version 7.0).
`
`If only one zone is defined for the entire internet (or if no zones are defined), all
`network services in the internet are presented in each Macintosh user’s Chooser window
`
`1
`
`and no zone name is displayed.
`
`Assigning nerworle numbers and ranges
`
`When you use a router to connect networks, you need to identify each network by
`
`assigning it a unique number or range of numbers. (As with zone name assignments, this
`
`is done during router setup.) LocalTalk networks are always identified by a single
`
`network number. Ethernet and Token Ring networks are identified by a network
`
`range. The network number or range must be unique in the internet. No two networks
`
`can have the same number and no two network ranges can overlap or have any network
`numbers in common.
`
`The network range is a series of contiguous network numbers, such as 1-10. Each
`
`number in a network range is a network identifier that can be associated with up to 254
`devices. The size of the network range determines the maximum number of AppleTalk
`
`devices on the physical network. For example, a network having the range 1-10 could
`
`contain up to 10 X 254 devices, or 2,540 devices. If an Ethernet or Token Ring network is
`never expected to require more than 254 devices, you can assign a range that contains a
`
`single number, such as 100-100.
`
`When assigning a network range, be sure the size of the range allows for ample
`
`network growth. For example, in a network containing 500 devices, the range 1-2 would
`
`accommodate current needs (2 x 254 devices = 508), but would only allow 8 additional
`node addresses for future growth. Exceeding this level of growth would require you to
`shut down the router and assign a new, larger network range, disrupting network
`services to users.
`
`Chapter 7 Design Guidelines 119
`
`PETITIONERS Ex. 1020, part 2, p. 40
`
`

`
`The recommended guideline in choosing a network range is to allow capacity for at
`least twice the current number of nodes (more, if rapid growth is anticipated). Since an
`AppleTalk internet supports up to 65,279 network addresses, or over 16 million possible
`node addresses (65,279 x 254 nodes), it’s possible to assign oversized network ranges
`and still have sufficient addresses for a very large internet. For further flexibility in your
`internet setup, when assigning network ranges, allow wide margins between the ranges
`you select. For example, if you assign a range of 100-110 to a network, you may want to
`start the next range with network number 120 rather than network number 111. If your
`internet has relatively few networks, margins between network ranges can be very large.
`
`6 Note Network ranges are part of the extended addressing capabilities of AppleTalk
`Phase 2. To learn more about the capabilities of AppleTalk Phase 2, refer to Inside
`AppleTal/e (second edition), the AppleTalle Phase 2 Introduction and Upgrade Guide,
`and The Advantages ofAppleTalle Phase 2. See the Appendix for information on how to
`
`obtain these publications. 9
`
`Although there are no rules for numbering networks, it’s useful to observe a
`consistent network numbering scheme—especially in large and fast-growing internets.
`One such scheme involves assigning a location code or department code to the digits in
`a network number. The following figure illustrates how a network numbering system
`
`can help to identify networks in an orderly way.
`
`Sample network range: 12345-12399
`
`Network range
`
`Site location (headquarters,
`field office, etc.)
`
`Building
`Floor
`
`120 Part 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 41
`
`

`
`A network numbering system serves several purposes:
`
`I
`
`I
`
`I
`
`It facilitates the assignment of network numbers when new networks are created.
`
`It identifies each network in a way that is meaningful to you. For instance, you can
`
`look at a routing table and immediately associate the network numbers with their
`
`physical locations (such as “building 2, third floor”).
`
`It avoids potential network numbering conflicts that can arise with duplicate
`numbers.
`
`Keep track of your network numbers and ranges by recording them in a logbook, in
`an electronic spreadsheet, or on your network map.
`
`Gateways
`
`The fourth kind of connection device—a gateway—is a combination of hardware and
`
`software that connects an AppleTalk network with a network using non—AppleTalk
`
`protocols, such as TCP/IP or DECnet. Gateways serve as translators between these
`
`otherwise incompatible network protocols. A gateway is not necessarily used to make a
`
`network larger; its primary purpose is to overcome differences between connected
`
`networks. The gateway interprets network-related information in a data transmission,
`
`such as addressing and routing instructions, then translates this information into the
`
`format of the protocols running on the connected network.
`
`Chapter 7 Design Guidelines 121
`
`PETITIONERS Ex. 1020, part 2, p. 42
`
`

`
`Gateways serve as translators
`between otherwise incompatible
`network protocols.
`
`-'
`
`protocols
`
`Node using TCP/IP
`
`Gateway
`
`.Ethernet
`
`¢/
`
`Node using AppleTalk
`protocols
`
`When to use a backbone
`
`If you are planning an internet, you’ll find that a backbone network is a very useful
`part of an efficient network layout. The primary function of a backbone is to transport
`information between other (often slower-speed) networks. A backbone is like a
`superhighway. It alleviates cross—network traffic congestion, providing each connected
`network with a more direct route to every other network in the internet. With a well-
`planned backbone network, data can be sent through a minimal number of routers to
`reach the destination network.
`
`It’s especially useful to create a backbone network to connect many separate
`networks or to connect networks that aren’t physically contiguous. A backbone is often
`used to connect networks on different floors of a building or in different buildings. In
`addition, you can connect network devices directly to a backbone, permitting faster
`access to heavily used devices such as file servers.
`
`122 Part 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 43
`
`

`
`Example A: without or baclebone
`
`IIIIIIIIIIIIIIIIIIIIIIIII
`
`Network 5
`
`lIIIIlIII>
`
`
`Example B: with 6?! backbone
`
`In the preceding figure, Example A shows five networks connected serially by
`routers, with no backbone. To get from Network 1 to Network 5, a packet would need to
`travel four hops and would have to contend with network traffic on three intervening
`networks—which may themselves be slower networks. In contrast, in Example B, the
`same transmission would need to travel only two hops, with the backbone network in
`between. (Network performance can be further enhanced if the backbone is a high-
`speed network such as Ethernet, as discussed in the next section.)
`
`Chapter 7 Design Guidelines 123
`
`PETITIONERS Ex. 1020, part 2, p. 44
`
`

`
`Selecting the backbone network type
`
`Any network type that can be connected to a router can be set up as a backbone.
`However, since the object of a backbone is to enhance performance—and since the
`backbone may be used as a thoroughfare for many connected networks—it’s desirable
`for the backbone network to transmit data at a fast rate.
`
`For example, any type of network can provide the efficiency of fewer hops between
`networks, but an Ethernet or Token Ring backbone also provides a high transmission
`speed. The backbone network type you select should take into account the usage level
`and performance needs of your own internet.
`
`Connecting networks of different speeds
`
`Since you can combine different network types in an internet, you need to consider
`where it would be most advantageous to place higher—speed networks in the layout of
`your internet. When possible, use faster networks in a busy route between other
`networks, as illustrated in the following figure.
`
`Not recommended
`
`More efflcient layouts
`
`LocalTalk
`
`124 Pom! 2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 45
`
`

`
`When connecting networks of different speeds, consider that most lower-cost routers
`(including the AppleTalk Internet Router) do not distinguish the speed of a network
`when selecting the most direct route to a destination. Instead, these routers select the
`route with the least number of hops. If you have a lower—cost router, wherever redundant
`routes exist, try to place fewer hops in the faster network so that this is the path selected.
`You may want to consider eliminating redundant routesin which the number of hop
`counts will cause the router to select the slower-speed route.
`
`Where to place shared resources
`
`How do you determine where it would be most efficient to place shared resources? If
`you have a single network, it doesn’t matter where you place printers and servers from a
`network performance standpoint. However, you will want to consider factors such as
`convenience and security. Shared printers should be easily accessible by network users.
`You may want to place servers close to you for administrative purposes or in an isolated
`area for security reasons (see Chapter 9 for a discussion of security).
`If you have two or more connected networks, there is one basic, common-sense rule
`
`about where to place shared resources: always try to place them on the same network as
`the people most frequently using them. Avoid placing routers or bridges between users
`and the devices they share. This will cause unnecessary traffic over networks that do not
`use the devices or that use them infrequently. If your internet includes a backbone
`network, consider locating devices shared equally by many networks on that backbone.
`(See the following examples.)
`
`Chapter 7 Design Guidelines 125
`
`PETITIONERS Ex. 1020, part 2, p. 46
`
`

`
`
`
`Poor network design
`
`0‘many users on Network B need to use the modem server
`on Network A, unnecessary trafitc will be
`generated on NetworkA.
`
`.
`
`\
`Printer \ _
`/
`.'
`
`Router
`File .°°’ o,
`server
`.'
`<3
`
`OQ
`O.’
`.9O
`.0OOC
`
`9. O
`
`/...
`‘\@
`
`\\
`
`‘J...
`. 9 0
`\
`
`.
`
`.0
`
`Modem@
`
`©
`
`Network A
`
`Network B
`
`
`
`Recommended network design
`
`To isolate traffic on each network,
`Network B has been given its
`own modem server.
`
`126 Part2 Planning Your Network
`
`PETITIONERS Ex. 1020, part 2, p. 47
`
`

`
`Placing shared devices on a backbone
`
`\s
`\/
`
`9
`‘9
`
`Backbone
`
`V .
`
`Users on hetwor/es A, B, and C all
`need to access
`rap '
`'le server,
`the g
`the scanner, and the co
`rmter,
`
`so it makes more sense to locate these
`shared devices on the hetworle
`backbone.
`
`Chapter 7 Design Guidelines 127
`
`PETITIONERS Ex. 1020, part 2, p. 48