_
`
`United States Patent [19]
`Picazo, Jr. et al.
`
`US005432907A
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,432,907
`Jul. 11, 1995
`
`[54] NETWORK HUB WITH INTEGRATED
`BRIDGE
`
`5,251,213 10/1993 Videlock et al. .............. .. 370/ 85.12
`5,299,195 3/1994 Shah ......................... .. 370/85.6
`5,301,303 4/ 1994 Abraham et a1. . . . .
`. . . . . .. 395/500
`5,329,618 7/1994 Moati et a1. ....................... .. 395/200
`[75] Inventors: Jose J. Picazo, Jr., San Jose; William
`.
`.
`.
`.
`E.St l S
`l,both fCl'f.
`Primary Exammer-Chnstopher B. Shin
`ee 5’ unnyva e
`o a 1
`.
`Attorney, Agent, or Firm—Ronald Craig Fish; Falk,
`[73] Asslgneez Network Resources Corporation
`Vestal 8‘ Flsh
`'
`[21] Appl. No.: 881,931
`ABSTRACT
`[57]
`[22] Filed:
`May 12, 1992
`H0“ 3/02 A hub circuit with an integrated bridge circuit carried
`[51] Int Cl 6
`370/85 12_
`out in software including a switch for bypassing the
`[52] US'
`' 3;7O364/242_94,364/242:95f bridge process such that the two bridged networks
`’
`’364/242_96.’364/DIG_ 1’
`effectively become one network. An in-band manage
`[58] Field of Search ............. .. 370/8512,’ 85.13, 85.14; mm Process in Software is disclosed which receives
`395 /2OO
`and executes network management commands rece1ved
`as data packets from the LANs coupled to the inte
`grated hub/bridge. Also disclosed is hardware and soft
`ware to implement an isolate mode where data packets
`which would ordinarily be transferred by the bridge
`process are not transferred except in-band management
`packets are transferred to the in-band management pro
`cess regardless of which network from which they
`arrived. An out-of-band to in-band management process
`receives network management commands and executes
`them or forwards them in-band to whatever device to
`whlch they are addressed
`
`[56]
`
`_
`References Clted
`U,S. PATENT DOCUMENTS
`Re. 33 426 11/1990 Sugimoto et a]. .............. .. 370/85.14
`4,627:052 12/1986 Home ct a1‘ ____________ "
`4,825,435 4/1989 Amundsen et al. ................. .. 370/97
`4,901,312 2/1990 Hui et al. ..
`370/8512
`4,922,503 5/1990 Leone
`370/3513
`----- "
`15/
`511x591?’
`395/2‘OO
`5’088’032 2x992 B2222: ”‘ a '
`5,114,453 5/1992 Morrow ......................... .. 370/85.13
`5,l79,554 l/1993 Lomicka et a1. ............... .. 370/8513
`5,214,646 5/ 1993 Yacoby .......................... .. 370/8514
`
`37 Claims, 6 Drawing Sheets
`
`REDUNDANT P S.
`
`FOIRL FIBER OPTIC HUB
`r
`r14
`
`111
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`
`20 ~E+
`
`W24
`
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`T34
`
`32
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`82
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`BRIDGE / WAN INTFC
`
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`BRIDGE / ROUTER!
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`
`56
`I10 BASE T HUB uamoorj [1o BASE T HUB / BRIDGE] 10 BASE T iHUB/ BRIDGE
`
`"?n * 633 E e167
`
`000001
`
`VIASAT 1011
`IPR of U.S. Pat. No. 5,960,074
`
`

`
`US. Patent
`
`July 11, 1995
`
`Sheet 1 of 6
`
`5,432,907
`
`REDUNDANT P S.
`I
`FOIRL FIBER OPTIC HUB
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`
`

`
`U.S. Patent
`
`July 11, 1995
`
`Sheet 2 of 6
`
`5,432,907
`
`90
`
`196
`
`INTEGRATED HUB I BRIDGE
`
`130
`
`AUI
`
`CONTRQLLER
`
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`000003
`
`000003
`
`

`
`US. Patent
`
`July ‘11, 1995
`
`Sheet 3 0f 6
`
`5,432,907
`
`LAN 1
`
`LAN 2
`
`CONTROLLER
`
`CONTROLLER
`
`(REPEATEH) \262 (BACKBQNE) N 264
`
`A
`
`‘
`
`A
`
`266
`h263 264
`v r260
`v
`(
`'
`265 L)
`-_“+'__’ //
`\
`2677 ‘- EEEEETE'EEEEE'ET ’
`f‘i’l___ l<-—|$OLATE MODE ‘
`P‘
`“I
`l [284
`
`268
`f
`BRIDGE
`DATA‘
`BA E
`S
`
`_> .
`
`MANAGEMENT
`INPUT OuEuE
`
`286
`
`306
`
`'
`
`W296
`
`I
`'
`CONFIGJSTATUS 0.5.
`\294
`
`280
`292 [288
`HUB/ BRIDGE IN - BAND L
`ggZEQTOF-LQIER
`MANAGEMENT EEOEEEE
`T
`290
`
`[282
`382133?!)
`PROcEss
`
`[298
`SERIAL PORT
`
`303
`
`31°
`
`300 \ :
`
`. MODEM
`
`FIG. 4
`
`000004
`
`

`
`US. Patent
`
`July 11, 1995
`
`Sheet 4 of 6
`
`5,432,907
`
`BRIDGE
`START
`
`GET NExT
`RECEIVED
`PACKET
`
`376
`
`34°
`
`A44
`342
`ERRoR IN YES DISCARD
`PACKET?
`PACKET
`
`4
`
`*
`
`NO [346
`UPDATE BRIDGE
`DATABASE wITH
`SOURCE ADDRESS
`AND NETwoRK lD
`FRCM wHICH PACKET
`CAME
`
`I READ DESTINATION
`
`ADDRESS OF
`PACKET AND LOOK
`FOR THIS ADDRESS
`IN BRIDGE DATABASE
`
`359
`
`IS DESTINATION
`ADDRESS ON SAME
`SIDE OF BRIDGE
`AS SOURCE ADDRESS
`FRoM WHICH PACKET
`ORIGINATED?
`
`7
`
`35a
`/
`PUT PACKET IN
`HUB MANAGEMENT
`INPUT QUEUE
`
`A
`
`{352
`
`DISCARD
`PACKET
`
`354
`
`356
`
`364
`[
`DISCARD
`PACKET
`
`N0
`
`_
`
`'
`
`IS PACKET AN
`INTERNAL HUB
`MANAGEMENT
`'7
`PACKET'
`
`IS PACKET PROTOCOL
`TYPE A TYPE WHICH
`SHOULD BE FQRWARDED?
`YES
`
`FIG_ 5A
`
`.
`To FIG. 58
`
`IS PACKET
`GRouP
`ADDRESSED?
`3 o
`YES
`CoPY THE J
`PACKET
`361
`I
`I
`PUT A COPY OF THE
`PACKET IN THE
`MANAGEMENT INPUT
`QUEUE 284
`.____________|
`
`000005
`
`

`
`US. Patent
`
`July 11, 1995
`
`Sheet 5 of 6
`
`5,432,907
`
`366
`
`DID PACKET COME
`FROM LAN 1?
`YES
`/ 368
`
`READ POINTER
`ADDRESS FROM LAN 2
`
`//
`
`37o
`
`BYPASS OR
`ISOLATE
`MODE
`
`FORWARDING VECTOR
`
`- - — - -—
`
`AND VECTOR PROCESSING
`TO ROUTINE POINTED TO
`
`V367
`
`DISCARD
`372 \J PACKET
`
`{382
`
`To
`BRIDGE
`START
`
`TRANSMIT ‘
`PACKET TO LAN 2
`USING LAN 2
`CONTROLLER
`
`[390
`
`374
`
`READ POINTER
`I
`ADDRESS PROM
`I
`LAN 1 FORwARDING
`VECTOR AND VECTOR ____ _ _ _ __ __
`PROCEEDING TO
`R TIN P
`Ou E OINTED TO
`
`‘Sh/‘05825
`
`DISCARD
`PACKET
`
`C375
`
`92
`
`39a
`
`BRIDGE OR
`BYPASS
`MODE
`
`394 J
`
`400 \
`
`TRANSMIT
`PACKET To
`LAN 1 USING
`LAN 1
`CQNTROLLER
`
`To
`BFHDGE
`START
`
`FIG. 5B
`
`Y
`396/
`
`\402
`
`000006
`
`

`
`US. Patent
`
`July 11, 1955
`
`Sheet 6 of 6
`
`5,432,907
`
`544
`
`500
`
`BUFFER
`
`RIC 1
`BUFFER
`
`CRS
`LEDS
`
`POL. STAT
`REG.
`
`516
`608
`TA B
`
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`
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`GATE
`ARRAY
`
`\_w_/
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`SELECTS
`
`564
`
`000007
`
`

`
`1
`
`NETWORK HUB WITH INTEGRATED BRIDGE
`
`20
`
`25
`
`BACKGROUND OF THE INVENTION
`The invention pertains to the ?eld of networks for
`communications between computers, and, more speci?
`cally, to improvements in hubs for such networks.
`Networks serve the purpose of connecting many
`different computers or terminals to each other, host
`computers, printers, ?le servers etc. so that expensive
`computing assets, programs, ?les and other data may be
`shared among many users. Communication protocols
`and standards for networks developed quickly to stan
`dardize the way in which data packets were sent across
`the data exchange media of the network. Several proto
`cols have developed for networks including Ether
`net TM , Token Ring TM , FOIRL and FDDI, the latter
`two being adapted for ?ber optic physical media carry
`ing the signals.
`The physical media ?rst used on Ethernet were thick
`coaxial cables, and a standard called 10Base5 was devel
`oped for assuring multivendor compatibility between
`components in thick coax, mix and match networks
`where network components from different vendors
`were used. These thick coax lines were bulky, expensive
`and hard to work with. Later, thinner coax Ethernet
`was developed, and, as an alternative to coax, un
`shielded twisted pair wires were used for the physical
`media. A vendor compatibility standard called 10Base
`T developed for twisted pair media.
`Networks have their own hardware and software to
`interface with the physical media that carry the signals,
`and the network software must interface with the oper
`ating system software. Computers communicate with
`each other using a set of rules called a protocol. A
`group of protocols, all related to the same model are
`called a protocol suite. To encourage open systems, a
`common model called 081 was developed by the Inter
`national Standards Organization. 081 engendered a
`protocol suite which allows computers of all sizes and
`capabilities the world over to communicate using a
`common set of rules.
`The 081 model has seven layers of software, each of
`which makes different functionality available to com
`45
`puters communicating using this model. Each layer in
`the model deals with speci?c computer-communication
`functions.
`The Physical Layer is the lowest layer and speci?es
`the rules for transmission of signals across the physical
`media. Hubs, also known as repeaters, have multiple
`connections to this physical media called pods. The
`purpose of a hub is to receive data packets from one
`port and repeat these packets, i.e., retransmit them on
`every other port connected to the hub according to
`whatever protocol, e.g., Ethernet, etc., which is in use.
`The Data Link layer deals with transmission of data
`between devices on the same network. In addition to
`describing how a device accesses the physical media,
`this layer also provides some measure of error detection
`and control. Local Area Network (LAN) technologies
`such as Ethernet, Token Ring and FDDI operate at this
`layer. Data link addresses are implemented at this layer,
`and provide each device connected to the network a
`unique identi?er by which packets may be sent to it.
`Bridges, which are devices which aid in forwarding
`data packets from one network segment or one network
`to another, operate at the Data Link layer.
`
`5,432,907
`2
`The Network Layer deals with transfer of data be
`tween devices on different networks. The Network
`Layer adds the notion of network addresses which are
`speci?c identi?ers for each intermediate network be
`tween a data source and a destination. Routers, which
`are devices which assist in transferring data packets
`from one network to another, operate at the Network
`Layer.
`The remaining layers, called the higher layers, are the
`Transport Layer, Session Layer, Presentation Layer
`and Application Layer. These layers deal with commu
`nication between message source and message destina
`tion. The transport layer manages the transfer of data
`from a source program to a destination program. Pro
`cess addresses, which identify speci?c “processes”, i.e.,
`computer programs, are implemented at this layer.
`Gateways operate at these higher 081 layers.
`Within the 081 model, the user presents data through
`application programs to the highest layer. This data is
`then passed downward through the hierarchy of layers
`with each layer adding addressing and/ or control infor
`mation. When the data reaches the physical layer, it is
`sent to a device.
`Conversely, received data is passed up through the
`layers with each layer stripping address or control in
`formation.
`One way to think of a protocol is a common language
`by which computers may communicate, but a more
`accurate way is as a set of rules by which data is com
`municated between identical OSI layers.
`There are other communication protocols beside the
`OSI Model. These include TCP/IP, XNS, IPX, Ap
`pleTalk, DECnet and SNA. Each of these protocols has
`its own layer model. For example, TCP/IP collapses
`network functionality into only 4 layers, while Ap
`pleTalk has 6 layers.
`All network media have a limitation on the maximum
`volume of traffic that may be carried based upon the
`bandwidth imposed by the physical characteristics of
`the media. Ethernet bandwidth is 10 Megabits/second.
`This acts a limit on the traf?c volume and can limit the
`number of computers, which may be connected to a
`single “segment” of a network. A segment is section of
`a network connected to a group of machines which may
`communicate with each other via repeater operations
`without having to traverse a bridge or router. Bridges
`and routers are useful in that they allow connections of
`multiple segments such that more computers may com
`municate with each other than would otherwise be
`possible given the limited bandwidth of the media.
`Each bridge and router requires certain other periph
`eral circuitry to support it such as LAN controllers, a
`CPU, a power supply, a network management process,
`memory to store bridge source and destination address
`tables and various other things like status registers etc.
`Likewise, repeaters require many support circuits many
`of which are the same support circuits needed by brid
`ges and routers. Further, bridges, routers and repeaters
`or hubs require initialization to set them up for opera
`tions, and they require initial installation labor to set
`them up properly to operate in a particular network
`con?guration. In addition, each type machine is subject
`to network management considerations, assuming an
`intelligent hub. An intelligent hub is one which collects
`statistics about traf?c flow through its ports, can elec
`tronically turn ports on and off and which provides
`error correction and detection services. Intelligent brid
`ges, routers and hubs supply status information upon
`
`40
`
`55
`
`60
`
`65
`
`000008
`
`

`
`5,432,907
`3
`request from network management processes and can
`respond to network management commands, such as
`shut off a particular port.
`In the prior art, bridges and routers were separate
`circuits from hubs and this created needless duplication
`of many peripheral circuits which were common be
`tween hubs and bridges and which could be shared.
`This needless duplication cost more and provided more
`points of failure. For example, if the bridge power sup
`ply failed or the CPU crashed, all machines on the two
`network segments on either side of the bridge would be
`cut off from each other.
`Typically, a bridge is connected to a hub by a sepa
`rate local area network segment which itself requires
`two port interface circuits such as LAN controllers and
`AUI’s (generic network interfaces) with appropriate
`port drivers adapted for the speci?c media used for the
`bridge-hub LAN segment. This bridge-hub LAN seg
`ment represents an additional expense, requires manage
`ment and provides additional points of failure which
`20
`could disable the network. An intelligent hub coupled
`to a bridge or router by a separate LAN segment then
`requires three different device addresses for manage
`ment message traffic, and creates more possibility for a
`network failure in multiplying the number of points of 25
`possible failure.
`Another drawback of separate bridge/router and hub
`circuits is that bridge/routers do not usually include a
`mode where the bridge/ routing function can be by
`passed. The ability to bypass the bridge/routing func
`tion provides ?exibility in network growth as small
`networks do not need bridging functions until the maxi
`mum network traffic volume starts to exceed the avail
`able network bandwidth. The ability to selectively by
`pass the bridge/routing function gives a network de
`signer the ability to design a small network which has a
`built in capacity to grow larger without adding new
`components and improves the ability to troubleshoot
`the network.
`Integrated hubs and bridges existed as option cards
`for concentrator chassis at the time this patent applica
`tion was ?led. One example of such a device is the
`Penril 2530 concentrator card with full performance
`bridging although it is not currently known whether
`this device quali?es as prior art because the copyright
`45
`date of the literature on this device is dated the same
`month as the ?ling date of this patent application. The
`Penril Module 2530 lOBaseT concentration and bridg
`ing card for the Penril 2500 series concentrator com
`bines a hub and bridge which operates at all times on the
`same printed circuit board. The design of the Penril
`2500 concentrators were for large networks. The 2530
`card slides into a card slot on the 2500 series concentra
`tor which can also service a plurality of such cards. The
`concentrator frame is believed to contain certain shared
`55
`features such as power supply etc. and has a local, inter
`nal LAN segment that couples all the repeater/bridge
`cards together so that they can send data back and forth
`between them. The repeater on each card can be cou
`pled to up to 25 machines on the network segment
`connected to that card and the integrated bridge contin
`uously bridges the network segment coupled to a partic
`ular card to the internal LAN segment such that a ma
`chine coupled to a LAN segment coupled to card 1 can
`send a packet to a machine coupled to a LAN segment
`coupled to card 2 via the bridge on card 1, the internal
`LAN segment of the concentrator, the bridge on card 2
`and the repeater on card 2. No distributed management
`
`60
`
`5
`
`15
`
`4
`functionality is integrated on either card 1 or 2. That
`management functionality is placed on a third card
`which is plugged into a different card slot. If the man
`agement card fails, the repeaters and bridges in cards 1
`and 2 cannot be controlled. Likewise, if the internal
`LAN fails, user 1 cannot send data to user 2 or vice
`versa.
`A concentrator structures like the Penril 2500 series is
`designed for large networks since to connect two exter
`nal network segments, two cards are needed each of
`which can service up to 25 user machines. If the net
`work has only 27 users, such a concentrator represents
`too big and complex of a structure to be affordable and
`justifiable.
`Another problem with. concentrators such as the
`Penril 2500 series is their lack of “stackability”. The
`problem which prompts the need for a stackable net
`work slice architecture is as follows. Suppose a particu
`lar building had 3 users on the ground ?oor and a group
`of 20 heavy users on the 4th ?oor or otherwise spaced
`away from the 3 users on the ground floor by a distance
`which is just under the maximum IOBaseT cable run
`permitted by the applicable Ethernet speci?cation. The
`use of a concentrator requires that every one of the
`group of 20 users has his own twisted pair running from
`his machine back to the concentrator. The same is true
`for thick and thin coaxial cable installations. Such a
`con?guration can be prohibitively expensive because a
`great deal of wire or coax must be used and the expense
`of installing all that wiring through the walls and ceil
`ings can be large.
`Now suppose that the distance to the group of 20
`from the concentrator is larger than the maximum al
`lowable cable run. In such a case, the complex wiring
`cannot be used, and if those users must be able to share
`resources with the 3 users on the ground floor, another
`concentrator must be purchased. Concentrators like the
`Penril are expensive. Typical costs today are in the
`neighborhood of $30,000 for the concentrator frame
`and about $6000 for each card.
`A similar problem arises in large networks in big
`companies who may, for example, have a branch of?ce
`in another state with only 6 users. If those users must
`share data or resources connected to the network at the
`parent company, they must be on the same network as
`the users at the parent company. With concentrator
`technology, the 6 users in the branch of?ce must be
`connected to the concentrator at the parent company
`by a wide area network (WAN) connection. The Penril
`concentrator 2500 series has a card module (the 2540)
`which implements a WAN interface, but the 6 users in
`the branch of?ce must also have a concentrator to plug
`their WAN interface card into. Therefore, the expense
`of having the tiny 6 user network segment remotely
`located is greater than it needs to be.
`Thus, a need has arisen for an apparatus which can
`perform the functionality of bridges or routers and hubs
`without the aforementioned de?ciencies, and which can
`overcome the aforedescribed dif?culties with concen
`trator technology in smaller networks or large network
`will small satellite networks.
`
`30
`
`35
`
`40
`
`50
`
`65
`
`SUMMARY OF THE INVENTION
`According to the teachings of the invention, a hub or
`repeater circuit which is initialized and managed by a
`microprocessor is integrated with a bridge or router
`which is integrated into the same system with the hub or
`repeater so that much of the circuitry that supports the
`
`000009
`
`

`
`10
`
`45
`
`5,432,907
`6
`5
`software. The isolate mode helps isolate problems on
`hub can be shared by the bridge. In the preferred em
`the network for faster troubleshooting.
`bodiment, the microprocessor which also serves to
`In the preferred embodiment, forwarding Vectors are
`initialize and manages the hub or repeater circuitry
`used to speed performance. These forwarding vectors
`executes an in-band management process in background
`and implements the bridge function by running a bridge
`are predetermined memory locations that contain
`pointer addresses pointing to separate bridge and bypass
`software routine in foreground. In the preferred em
`software routines. The bypass routine simply discards
`bodiment, the bridge process selectively couples two
`the packet because the repeater has already sent the
`local area networks together designated network one
`packet out on network two through the AUI port. In
`and network two, and the bridge process can be shut off
`the preferred embodiment, there are separate receive
`in a bypass mode such that the two network segments
`and transmit buffers in memory which are implemented
`on either side of the bridge are merged into one large
`by a linked list. The bypass process discards the packet
`network segment. The one or more network segments
`by removing it from the receive buffer of the network
`coupled by the bridge may have different protocols
`from which it arrived by rearranging the pointers on the
`such as Ethernet and Token Ring or FDDI in some
`linked list to skip over the packet and either erasing the
`embodiments. The hub serves as the network interface
`packet or informing a memory managing process that
`for network one for the bridge process, and a LAN
`the block of memory locations consumed by the packet
`controller and transceiver serve as the network inter
`are available for other uses such as storing other pack
`face for network two. Usually, network two is a back
`ets.
`bone connection, but in some embodiments, it may be a
`In an alternative embodiment, a console command
`wide area network (WAN) or another repeater and
`process executing in background in software receives
`another LAN segment comprised of a plurality of trans
`out-of-band management commands from the network
`ceiver cables coupled to the ports of the repeater. In a
`manager via a modem or a terminal connected to the
`WAN embodiment, the LAN controller will be re
`integrated hub/bridge. The console command process
`placed with a WAN controller. In some embodiments,
`executes any management messages addressed to the
`the bridge process selectively couples more than two
`integrated hub/bridge by interacting appropriately with
`networks, and in some embodiments, the bridge process
`the hub, bridge process etc. Any management messages
`is replaced by a router process. The bridge or router
`addressed to other hubs, bridges, routers etc. on any of
`function may be performed in either hardware or soft
`the networks coupled together are written as data pack
`ware.
`ets into the transmit buffer of the appropriate network
`Dynamic random access memory is shared between
`which must be traversed to get to the destination ma
`the bridge process and two LAN controllers. One of the
`chine.
`LAN controllers is coupled to the hub and the other is
`An important aspect-of the invention is in the “net
`coupled to the bridge process. The LAN controller ‘
`work slice” stackable architecture implemented by the
`coupled to network two uses a transceiver to drive the
`integrated hub/bridge. This architecture is especially
`physical media of network two.
`useful in small networks and to solve the problems
`In the preferred embodiment, the bridge software
`noted above with concentrator technology. As the term
`includes a bypass mode wherein the bridge function is
`is used herein, the genus of machines each of which may
`bypassed and data packets presented at any port' of
`be referred to as a “network slice” is a stand-alone hub
`network one to the repeater circuitry are repeated on all
`or repeater with 26 or fewer ports, having its own en
`network one ports as in normal processing and are also
`closure and user interface switches and indicator light,
`repeated on an AUI port. This AUI port is coupled to
`and having a built-in, i.e., integrated bridge to couple
`network two through a software controlled switch to
`the repeater ports to a backbone, a local backbone or
`the transceiver used in the bridge mode to couple the
`another repeater and LAN segment, and having distrib
`bridge process to network two in some embodiments.
`uted management, i.e., a collection of subroutines in the
`This transceiver is therefore shared between the bridge
`control software that can understand management com
`and bypass modes. In the preferred embodiment, the
`mands and requests for data originated by a network
`AUI port on the network one hub or repeater is coupled
`administrator. One important species in this genus has
`in bypass or bridge modes to the network two media
`“open architecture” while another important species
`through a media access unit (MAU) in the form of a
`utilizes a bypass mode wherein the bridge function is
`module which slides into or out of the AUI port thereby
`bypassed and the two LAN segments connected to
`enabling different MAU’s for different media types on
`either side of the bridge are connected together to form
`network two to be easily exchanged when conditions
`a single LAN. “Open architecture” means that certain
`demand a change in media type on the second network
`national standard for network communication and man
`segment or backbone connection.
`agement are implemented. The hub/bridge according
`In an alternative embodiment, an “isolate” mode is
`to the teachings of the invention supports the known
`also embodied in the hub/bridge system. In isolate
`SNMP network management protocol and all the
`known national RFC’s and MIB standards published by
`mode, no packets are forwarded from network one to
`network two thereby effectively isolating these two
`the IETF for repeaters, bridges, RS232 ports, MAUs,
`networks from each other except for in-band manage
`ethernet protocols, internet ?le transfer and other pro
`ment packets. In-band management packets are data
`tocols and the IEEE 801.1(d) spanning tree, ?ltering by
`protocol algorithm.
`packets containing commands, status inquiries etc. from
`the network manager to administer various aspects of
`By integration of a hub and bridge in the same pack
`network operation. In isolate mode, if an in-band man
`age, circuitry can be shared so costs are reduced, a
`agement packet appears at either network interface, the
`network link between a separate bridge and hub can be
`65
`eliminated thereby further reducing costs and simplify
`bridge process selects this packet from the stream of
`ing installation in that only one setup procedure need be
`data and forwards it to the input queue of an in-band
`management process carried out by the hub/bridge
`performed instead of two, and points of failure are elim
`
`30
`
`50
`
`55
`
`000010
`
`

`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a typical network envi
`ronment in which the teachings of the invention ?nd
`utility.
`FIG. 2 is a block diagram of one embodiment of the
`invention employing the broad concept of integration
`of a bridge with a hub in the same package to share
`circuitry and eliminate points of failure which would
`exist if the bridge and hub were separate circuits.
`FIG. 3 is a block diagram of another embodiment of
`the invention with dual network two transceivers for
`fault tolerance.
`FIG. 4 is a data flow diagram illustrating the three
`software processes that are executed in the preferred
`embodiment, to perform bridging, in-band management
`and out-of-band management functions.
`30
`FIGS. 5A and 5B are a flow diagram of the process
`ing of the bridge process illustrating operation of the
`forwarding vectors.
`FIGS. 6A and 6B are a block diagram of the circuitry
`of the preferred embodiment.
`
`25
`
`35
`
`5,432,907
`7
`8
`inated thereby improving reliability. For example, with
`30 is also connected via a coaxial backbone connection
`separate bridge and hub boxes, if the bridge fails, the
`48 to a lOBase-T hub with integrated bridge 50.
`The lOBase-T hub 50 is connected via a plurality of
`hub and the machines of network one are cut off from
`repeater ports 56 to a plurality of computers of which
`network two and the hub cannot be managed if the
`computers 52 and 54 are typical. Any data packet enter
`network manager is coupled on the network two side of
`ing the hub 50 from any one of the ports is automatically
`the bridge. According to the teachings of the invention,
`repeated on all the other repeater ports 56. The same
`this problem can be eliminated by bypassing the bridge.
`type of repeating operation is carried out automatically
`The bypass mode also gives more ?exibility for network
`by all of hubs 12, 30, 34, 38, 66 and 72.
`growth. Further, with the invention, both the bridge
`A lOBase-T hub uses a physical layer communication
`and hub functions can be managed by the network man
`protocol which is appropriate for a twisted pair of phys
`ager by messages to the same address which reduces
`ical media. Twisted pair connections are shown in FIG.
`in-band network management traffic.
`1 by lines with single slashes through them. A lOBase2
`hub repeats data packets on its ports using a physical
`layer protocol appropriate to coaxial cable.
`The lOBase-T hub 34 has a plurality of repeater pods
`connected to a plurality of computers of which device
`62 is typical. Hub 34 also has a twisted pair port connec
`tion 64 to another lOBase-T hub 66 which has an inte
`grated bridge. Connection 64 is a backbone connection
`for hub 66. Hub 66 is connected to a plurality of com
`puters of which computer 67 is typical via repeater
`ports 68.
`Likewise, hub 34 is connected via a twisted pair pod
`connection 70 to the backbone port of another lOBase-T
`hub with integrated bridge 72. The hub/bridge 72 is
`connected to a plurality of computers via repeater pods
`74.
`As an example of how the integrated hub bridge
`circuits in FIG. 1 work, consider the following hypo
`thetical data exchange transactions. Suppose that com
`puter 52 wishes to send a data packet to computer 54. In
`this example, the data packet would enter the lOBase-T
`hub/bridge 50 via twisted pair line 80 and would be
`automatically repeated on all the repeater ports 56 in
`cluding twisted pair line 82. Computer 54 would receive
`the packet as would all the other computers connected
`to hub/bridge 50. However, the packet would have a
`destination address indicating device 54 was the in
`tended recipient such that other computers connected
`to the hub/bridge 50 would discard the packet.
`In the preceding example, the bridge function in
`hub/bridge 50 would examine the destination address of
`the packet arriving via twisted pair 80 and check a
`forwarding table of network addresses which contains
`entries for various network addresses indicating
`whether those addresses are on network 1 or network 2.
`In the bridge mode of operation for hub/bridge 50, all
`of the repeater ports 56 are considered to be network 1
`and the backbone connection 48 is considered to be
`network 2. The bridging function, in the preferred em~
`bodiment, is a learning bridge which builds the for
`warding table as data packets arrive at the bridge from
`each source address. The bridging function knows
`which network a packet came from, and will make an
`entry in its table associating each source address with
`the network from which it came. Assuming that com
`puter 54 had already sent a packet somewhere else, the
`bridging function would know that computer 54 was
`connected to network 1 and therefore would not for
`ward the packet received from computer 52 to the net
`work 2 via backbone connection 48. However, in the
`situation where computer 54 had not previously sent a
`packet, the bridging function in hub/bridge 50 would
`assume that computer 54 was connected to network 2,
`and would forward the packet to network 2 via back
`bone connection