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Contents
1. 1 5005287103 Patent Number 5 287 103 Feb 15 1994 Date of Patent United States Patent Kasprzyk et al 11 45 54 METHOD AND APPARATUS FOR Primary Examiner Donald J Yusko PROVIDING LOCAL AREA NETWORK Assistant Examiner Brian Zimmerman CLIENTS WITH INTERNETWORK Attorney Agent or Firm Michael B Johannesen IDENTIFICATION DATA 57 75 Inventors Marlon Z Kasprzyk Carol Stream 57 Paul K Wolfe Jr Naperville both An arrangement providing an internetwork identifica of Ill tion in response to a broadcast message from a LAN client wherein the broadcast message comprises the 73 Assignee amp Laboratories Murray LAN client s LAN address The exemplary apparatus Hill N J comprises a receiver for receiving a message from the 21 Appl No 814 129 LAN and a translator coupled to the receiver for e viding a translation of the LAN address to an internet 22 Filed Dec 30 1991 work identification responsive to determining that the 51 Int H04Q 1 00 received message is a broadcast message request for 52 055 Cl 340 825 52 370 94 1 internetwork identification The translator comprises 58 Field of Search 340 825 52 370 94 1 first device for determining that the received message 395 200 comprises a broadcast message request for an internet 56 References Cited work identificat2. 4 of 6 5 287 103 FIG 4 RARP REQUEST MESSAGE RARP LAN ID IN ADDRESS TABLE U S Patent Feb 15 1994 Sheet 5 of 6 5 287 103 FIG 5 500 DISPLAY MAIN MENU ON SCREEN 502 SERIAL INPUT FROM KEYBOARD 504 5 YES 506 GET INPUT LINE FROM KEYBOARD 508 IS INPUT REQUEST TO UPDATE NO O ADDRESS TABLE FIG 6 YES 510 DISABLE RECEIVE UNIT 512 DISPLAY ADDRESS TABLE MAINTENANCE MENU 514 OPERATION REQUEST FROM KEYBOARD ADD CHANGE 516 DELETE OR DISPLAY ADDRESS TABLE PER INPUT REQUEST IS REQUEST TO EXIT YES 520 UPDATE OFFICIAL ADDRESS TABLE 522 ENABLE RECEIVE UNIT 524 U S Patent Feb 15 1994 Sheet 6 of 6 5 287 103 SELECT OPERATION MODE TYPE MONITOR PACKET TRAFFIC RECEIVE UNIT FIG 4 RARP REQUEST SEND DIAGNOSTIC PACKET TALK TO ROUTER 5 287 103 1 METHOD AND APPARATUS FOR PROVIDING LOCAL AREA NETWORK CLIENTS WITH INTERNETWORK IDENTIFICATION DATA TECHNICAL FIELD This invention relates to local area networks LANs and more specifically to a method and apparatus for providing reverse address resolution ina LAN when a router is used BACKGROUND OF THE INVENTION Local area networks LANs are becoming increas ing sophisticated with several layers of protocols serv ing several purposes in routing and administering traffic on the LAN Incr
3. for counting and reporting on unusual mes sage types being distributed on LAN 110 Additionally if the Internet ID is not found in the address table a new 10 20 25 30 35 40 45 50 55 60 65 8 of the address table requested from the file server If the Internet ID is still not found in the new copy of the address table then the local RARP server could log the failed request to the file server It is there fore intended that such variations be included within the scope of the claims We claim 1 A method for providing an internetwork identifica tion to a client on a local area network LAN said LAN client comprising a node on said LAN that does not have a writable non volatile memory for storing said internetwork identification said LAN being con nected to other LANs by a router said router being configured to not pass broadcast messages from said LAN to said other LANs said method comprising receiving on said LAN a broadcast message from said LAN client during initialization of said LAN cli ent said broadcast message requesting an internet work identification for use in subsequent communi cation with nodes on said other LANs and specify ing an address of said LAN client translating said address of said LAN client into said internetwork identification and transmitting a message on said LAN to said LAN client containing said internetwork identification whereby sai
4. of the LAN address to an internetwork identifica tion responsive to determining that the received mes sage is a broadcast message request for internetwork identification Advantageously the translator com prises a first device for determining that the received message comprises a broadcast message request for an internetwork identification and a second device cou pled to the first device and responsive thereto for re ceiving the LAN address and providing the internet work identification The second device may comprise a disk system or other writable nonvolatile electronic device Furthermore the apparatus may include an interface for a terminal device to update the second device is also provided wherein said updating device comprises a device for sending an update request to a file server and a device responsive to a message from the file server for updating the second device BRIEF DESCRIPTION OF THE DRAWING A more complete understanding of the invention may be obtained from a consideration of the following de scription in conjunction with the drawings in which FIG 1 is a block diagram illustrating the principles of this invention in the context of a multi LAN network employing a router to translate protocols and distribute messages FIG 2 is a block diagram of a local reverse address resolution protocol RARP server of FIG 1 according to an exemplary embodiment of this invention and FIGS 3 6 are flow charts for a RARP
5. packets in the receive unit memory in decision diamond 310 then processing continues to box 312 where communication is established with the IO port 275 FIG 2 A determination is made in deci sion diamond 314 whether the serial port is active If the serial port is not active processing loops to decision diamond 306 If in decision diamond 314 the serial port is active then processing continues to the process serial port subroutine FIG 5 When the process serial port subroutine returns processing loops back to decision diamond 306 Turning now to FIG 4 the process packet subrou tine is shown Processing starts in box 400 where the packet is moved from receive unit 215 FIG 2 to mem ory through LAN interface RAM 240 and into control 1 RAM 270 FIG 2 The receive unit memory is then freed Processing continues to decision diamond 402 where a test is made of the message type If the message type is not a RARP type then the message is not a broadcast message requesting a reverse address transla tion Processing thus continues to box 404 where the packet is discarded Processing then continues to bal loon 406 where the subroutine returns If in decision diamond 402 the message is of type RARP then processing continues to decision diamond 408 where a test is made if the address found in the message is in the address table In a normal case the address will be found in the address table and the Inter net ID is sent to
6. purposes only as this invention may be used with any physical layer LAN protocol of the LANs are connected to a router 140 Router 140 receives all messages on all of the LANs connected to it and recognizes messages that are to be forwarded to another LAN Router 140 translates the message protocol from the source LAN to the destina tion LAN and transmits the message on the destination LAN Routers such as router 140 are known in the art In this exemplary embodiment router 140 is manufac tured by Proteon Inc Two Technology Drive West borough Mass and described in Proteon Model p4200 Hardware Installation Manual No 42 040182 00 De cember 1989 Additionally router 140 accepts mes sages from all LANs destined for a common file server 150 File server 150 is usually a main frame or large mini computer as is known in the art File server 150 pro vides mass storage and other resources for all of the LANSs connected to router 140 File server 150 may also have print spooler and other functions that may be required by the LANs Router 140 translates a message received for file server 150 into the proper protocol and sends the message to fiber optic modem 160 in this preferred embodiment Fiber optic modem 160 trans mits the message via fiber optic links 162 to a second fiber optic modem 164 Second fiber optic modem 164 communicates with file server 150 File server 150 re sponds to the request by sending a message back to
7. server accord ing to FIG 2 describing the program control of the preferred embodiment of this invention 5 287 103 3 DETAILED DESCRIPTION FIG 1 shows a simplified block diagram illustrating a multi LAN network 100 employing an exemplary em bodiment of this invention Multi LAN network com prises LAN 110 and connections to a plurality of other LANs such as 120 and 130 Nodes on each LAN on multi LAN network 100 communicates using the IN TERNET protocol as is known in the art and fully described in D E Comer Internetworking with TCP IP Vol I Principles Protocols and Architec ture Second Edition Prentice Hall 1991 Nodes on LAN 110 communicate with each other using for ex ample ETHERNET R protocol either version 1 or version 10 ETHERNET is a registered trademark of 15 the Xerox Corporation as the physical layer protocol in the Open Systems Interconnection OSI 7 layer reference model established by the International Orga nization for Standardization Switzerland and de scribed in W Stallings Data and Computer Communi cations Third Edition Macmillan Publishing Com pany 1991 LAN 120 uses for purposes of this illustra tion STARLANIO as is known in the art and described in AT amp T Starlan Network Hardware Technical Refer ence Issue 01 Select Code 999 120 201 available from AT amp T LAN 130 may be for example another ETHERNET LAN The intra network protocols used here are for illustrative
8. the requester via fiber optic modem 164 fiber optic links 162 and fiber optic modem 160 to router 140 Router 140 translates the response to the proper protocol and sends the message on the appropriate LAN It is increasingly common to have a file server lo cated in a computer center or facility remote from the one or more of the LANs it serves For example a research and development facility may have a complex comprising several buildings One or more of the build ings may be physically located remotely from the com puter center where the file server is located Also it is increasingly common to have a file server in a first state 20 25 30 40 45 55 65 4 such as New Jersey and have a development center in a second state such as Illinois In both of these cases it is not possible to have a high quality metallic path con necting the router and the file server Therefore fiber optics are employed in this embodiment of this inven tion but other media may be used facilities permitting LAN 110 comprises for purposes of this illustrative embodiment of this invention a plurality of work sta tions 111 and a test system 112 as is common in many development laboratories Work stations 111 comprise a terminal or small personal computer as is known in the art Test system 112 comprises a computer switching frame or other device that is commonly stored program controlled In this exemplary embodiment test system
9. 112 is down loaded with control software from file server 150 and controlled by one or more of work stations 111 In the prior art when a work station 111 or test sys tem 112 came onto the LAN it could communicate with work stations 111 and test system 112 but could not communicate with LANs 120 and 130 or with file server 150 because it did not know its Internet ID Work stations 111 and test system 112 do not have storage facilities that are protected from power shut down sometimes call diskless systems In order to obtain an Internet ID work stations 111 and test system 112 must send a message to file server 150 containing an address File server 150 maintains an address table 116 with a translation of address to Internet ID Since work stations 111 and test system 112 do not know the ad dress of the file server they must send broadcast mes sages on the network requesting their Internet ID Routers such as router 140 are traditionally built so that messages are routed with maximum efficiency and a minimum of congestion Since broadcast messages cause congestion routers such as router 140 do not pass on broadcast messages because broadcast messages have to be sent to all LANs as well as to file server 150 Therefore all diskless systems on a LAN cannot communicate from the home LAN 110 to another LAN or to the file server without going through the router to Obtain an Internet ID from the file server but the router will
10. ANs 120 and or 130 FIG 2 is a block diagram illustrating the main com ponents of Local RARP server 115 Local RARP server 115 is in this exemplary embodiment divided into a LAN interface 210 and a controller 250 LAN interface 210 provides the physical connection to LAN 110 and receives all messages sent on LAN 110 at re ceive unit 215 Receive unit 215 is under the control of CPU 220 and notifies CPU 220 of any incoming mes sage packets of a specific type In this preferred embodi ment receive unit 215 notifies CPU 220 of the receipt of messages of type RARP CPU 22015 a dedicated LAN interface CPU which is Intel 82586 available from the Intel Corp Beaverton Oreg and described in Local Area Networking LAN Component User s Manual Order Number 230814 004 in the preferred embodiment CPU 220 is a processor under control of a program stored in ROM 230 CPU 220 causes message packets of type RARP to be moved from receive unit 215 into RAM 240 CPU 220 then causes the message packets to be moved from RAM 240 into controller 250 Controller 250 reads the header of the RARP mes sage searching for the field which contains the address of the device requesting its Internet ID Controller 250 is under control of CPU 260 which is a standard micro processor in the preferred embodiment CPU 260 is a processor under control of a program stored in ROM 265 Message packets are received in controller 250 at RAM 270 after being transf
11. atus com prising means for receiving said broadcast message from said LAN and means coupled to said means for receiving for pro viding a translation of said address of said one client to an internetwork identification responsive to determining that said received message is a broadcast message request for internetwork identi fication 6 An apparatus in accordance with claim 5 wherein said translation means comprises first means for deter mining that said received message comprises a broad 5 287 103 9 cast message request for internetwork identification and second means for receiving said address and pro viding said internetwork identification said first means coupled to said second means and said second means responsive to said request by said first means for provid ing said internetwork identification 7 An apparatus in accordance with claim 6 wherein said second means comprises a disk system 8 An apparatus in accordance with claim 6 wherein said second means comprises a writable nonvolatile electronic device 9 An apparatus in accordance with claim 6 further comprising means for interfacing said first means to a terminal 10 An apparatus in accordance with claim 6 further comprising means for updating said second means 15 20 25 30 35 45 50 55 65 10 11 apparatus accordance with claim 10 wherein said updating means comprises means for sending an update request
12. d internetwork identification of said LAN client is obtained without said router passing said broadcast message to other LANs 2 A method in accordance with claim 1 wherein said translating comprises performing a table look up in an address table where said LAN address is paired with its corresponding internetwork identification 3 A method in accordance with claim 2 further com prising if said LAN address is not paired with a correspond ing internetwork identification in said address ta ble transmitting a diagnostic message to said LAN client 4 A method in accordance with claim 2 further com prising if said LAN address is not paired with a correspond ing internetwork identification in said address ta ble transmitting a request to a file server for an update of said address table 5 An apparatus for use in a LAN said LAN compris ing one or more clients that do not have writable non volatile memory for storing an internetwork identifica tion said client relying on a node on one other LAN for data storage said LAN being connected by a router to other LANs including said one other LAN said router being configured to not pass broadcast messages from said LAN to said other LANs said apparatus providing an internetwork identification in response to a broadcast message request for internetwork identification at ini tialization of one of said client said broadcast message including said one client s address said appar
13. d to a terminal 117 for controlling controller 250 Additionally one I O port 118 of I O 275 is op tionally connected to router 140 for remotely control ling router 140 Any of the I O ports of I O 275 may be connected to additional LANs or other serial devices as is known in the art FIG 3 is a flow chart showing the control of CPU 260 FIG 2 of the preferred embodiment of this inven 25 35 40 45 65 6 tion The local RARP server of this invention is initial ized upon power up Therefore processing starts in balioon 300 with power up Processing continues to box 302 where the system boots via ROM 265 FIG 2 or alternatively pumped from a card download system as is known in the art Processing continues to box 304 where the parameters for the LAN interface 210 CPU 220 FIG 2 are set and the receive unit 215 FIG 2 is started Processing continues to a large loop that remains active until the power is turned off Processing contin ues to decision diamond 306 which represents a power off If the power goes off processing terminates at bal loon 308 If the power is on then processing continues to decision diamond 310 where a test is made if the receive unit has received a packet If the receive unit has received a packet then processing continues to the process packet subroutine FIG 4 When the process packet subroutine returns processing loops to the test for power decision diamond 306 If there were no
14. e the table then processing pro ceeds to connector FIG 6 If in decision diamond 508 input request is to update the table then processing continues to box 510 where receive unit 215 FIG 2 is disabled The receive unit is disabled so that no partial Internet IDs are delivered to clients on the LAN and so that the proper Internet ID is delivered in all cases Processing continues to box 512 where the address table maintenance menu is displayed Processing continues to box 514 where the operation request is obtained from the keyboard Processing con tinues to decision diamond 516 where a test is made if the keyboard input is a request to exit If it is not then processing continues to box 518 where the address table 116 FIG 2 is updated with additions changes dele tions or a display of the address table entries is per formed Processing continues from box 518 back to box 512 where the address table maintenance menu is dis played If in decision diamond 516 that the input from the keyboard was determined to be a request to exit then processing continues to box 520 where address table 116 FIG 2 is updated Processing then continues to box 522 where receive unit 215 FIG 2 is enabled so that Internet IDs may be obtained and processing returns in balloon 524 Turning now to FIG 6 if in decision diamond 508 the input is determined not to be a request to update the address table then processing proceeds through con nect
15. easingly routers are being used to connect or more LANs together and to file servers printers and other centrally located services A router may change or translate the protocol of one LAN to the protocol of another as part of its function By using a router several diverse LANs may be connected to each other and also share common resources Routers gener ally require that in order to transmit a message from one LAN to another or to the common resources the message must have an inter network identification In ternet ID of the sending or receiving node of the LAN One of the characteristics of most routers is that they do not translate and distribute broadcast messages from clients on one LAN to other LANs or to common re sources This design evolved because the distribution of broadcast messages caused severe inter network con gestion that results in blocking of other messages How ever this design causes an important group of LAN clients to be cut off from inter network communications and central services Any LAN client that does not have writable non volatile memory is cut off from such inter network communications and services until properly initialized If a LAN client has a writable non volatile store such Internet ID information can be stored therein and will be available following any occasion when the LAN client is taken out of service and its other memory con tents destroyed As stated above in order to establi
16. erred from RAM 240 of LAN interface 210 via direct memory access as is known in the art under control of CPU 220 CPU 260 finds the address in RAM 270 and performs a data base look up in address table 116 Address table 116 in the preferred embodiment com prises a 1 44 megabit floppy disk system as is known in the art Alternatively address table 116 may com prise a large hard disk system EEPROM PROM or some other form of occasionally writable non volatile memory Address table 116 may be updated by simply removing the disk and adding or deleting addresses or may be updated by a program running on CPU 260 which displays address Internet ID pairs and allows the user to add change and delete such pairs Address table 116 may for more sophisticated system be up dated by requesting a new copy of the address table from the file server Upon determining the Internet ID CPU 260 formats a return message packet for the device requesting its Internet ID in RAM 270 CPU 260 then notifies CPU 220 and CPU 220 causes the message packet to be moved into RAM 240 via direct memory access CPU 220 then causes the message packet to be moved into receive unit 215 which send the message packet out on LAN 110 Controller 250 also comprises in the preferred em bodiment an I O controller 275 as is known in the art for coordinating serial I O with devices other than LAN 110 In this embodiment I O port 119 in I O 275 is connecte
17. ion and a second device coupled to the U S PATENT DOCUMENTS first device and responsive thereto for receiving the LAN address and providing the internetwork identifi 4 813 038 3 1989 Lee 370 94 1 cation The second device may comprise a disk system 4 816 826 3 1989 340 825 52 or other writable nonvolatile electronic device 5 163 045 11 1992 Caram 370 94 1 5 166 931 11 1992 Riddle 370 94 1 5 185 860 2 1993 WU aaa 395 200 12 Claims 6 Drawing Sheets COMPUTER CENTER 150 CROSS CAMPUS CLIENTS LOCAL AREA NETWORK LOCAL RARP SERVER U S Patent Feb 15 1994 Sheet 1 of 6 5 287 103 ROSS CAMPUS 19 4 7115 COMPUTER CENTER m n 150 SERVER 164 160 lt gt E FEER FIBER ADDRESS H MODEM 2 ROUTER TABLE c FIG 1 U S Patent Feb 15 1994 Sheet 2 of 6 5 287 103 117 ar 115 LOCAL RARP SERVER De 275 I I 0 260 215 230 265 LAN RECEIVE 110 UNIT 240 270 l LAN INTERFACE 116 L ADDRESS TABLE CONTROLLER 2507 FIG 2 U S Patent Feb 15 1994 Sheet 3 of 6 5 287 103 FIG 3 300 SET PARAMETERS FOR LAN COPROCESSOR amp START UNIT IS PACKET IN UNIT RARP REQUEST PORT SERIAL PORT U S Patent Feb 15 1994 Sheet
18. not forward broadcast messages To solve this problem a local RARP server 115 is used according to the principles of this invention The local RARP server LRS listens to the network for broadcast messages of one or more specific types trans lates the address into an Internet ID and responds to the requester In the preferred embodiment local RARP server 115 includes copy of the address table 116 as kept in file server 150 Local RARP server 115 includes in the preferred embodiment a terminal 117 for updating address table 116 and controlling such functions as monitoring packet transfer and diagnostics Additionally an optional connection 118 may connect local RARP server 115 to router 140 and local RARP server 115 may control initialize etc router 140 In this exemplary embodiment when test system 112 is powered up or otherwise initialized as part of the boot function it will send a broadcast message on LAN 110 requesting its Internet ID Local RARP server 115 monitors LAN 110 receives the message and deter mines that the message is a broadcast message Local RARP server 115 next uses the address of the device from the broadcast message and performs a table look up to determine the Internet ID for the received ad dress Local RARP server 115 formats and sends message to the requester including the Internet ID The 5 287 103 5 requester this case test system 112 may then com municate with file server 150 or L
19. ntification and the LAN address of the LAN client translates the LAN address into an internetwork identification and trans mits a message comprising the internetwork identifica tion to the LAN client In a method according to the preferred embodiment of this invention a LAN client sends a broadcast mes sage comprising its LAN address on the LAN request ing an internetwork identification so that it may com municate with clients on other LANSs and one or more file servers through a router local reverse address resolution protocol server monitors the LAN for such requests The local reverse address resolution protocol server translates the LAN address from the message into an internetwork identification and transmits a mes sages comprising the internetwork identification to the LAN client Advantageously the translation comprises performing a table look up in an address table where the LAN address is paired with its corresponding internet work identification Furthermore if the LAN address is not in the address table a diagnostic message is sent to the LAN client Anapparatus according to the preferred embodiment of this invention provides internetwork identification in response to a broadcast message from a LAN client wherein the broadcast message comprises the LAN client s LAN address The apparatus comprises a re ceiver for receiving a message from the LAN and a translator coupled to the receiver for providing a trans lation
20. or A to box 526 where the normal mode menu is displayed Processing continues to decision diamond 528 where input is retrieved from the keyboard and the operation mode is selected Processing may continue in box 530 where all packets coming into the receive unit are monitored This informs the maintenance person of the packet traffic on local area network 110 Alterna tively in box 532 a diagnostic packet may be sent across LAN 110 to determine the functionality of both the LAN and the local RARP server Also in box 534 communication may be established through IO 275 FIG 2 to router 140 FIG 1 After each step in this process processing continues through connector A where packets are checked for RARP requests This gets high priority to handling of packets which is the primary functionality of the local RARP server Pro cessing then returns back to box 526 Also as a result of the select operation mode type decision diamond 528 a selection would be made to exit the normal mode in box 536 In this case processing continues to the return balloon 524 It is to be understood that the above described em bodiment is merely an illustrative principle of the inven tion and that many variations may be devised by those skilled in the art without departing from the scope of the invention For example local RARP server could be used to monitor for unauthorized access to a local area network Local RARP server could also be used as a monitor
21. sh inter network communication a LAN client must have an Internet ID However work stations that do not have a disk system and development or test models in systems laboratories frequently do not have writable non volatile memory necessary to store the inter net work identification Internet ID necessary to commu nicate through a router When such a work station or test system is initially connected to the LAN or con nected to the LAN following being taken out of service with contents of memory cleared or otherwise de stroyed it sends a broadcast message to the file server where Internet IDs are stored requesting its Internet ID Since the router does not distribute broadcast mes sages the Internet ID request is not delivered to the file server The solution of providing a file server for each LAN is very expensive and further introduces problems of concurrently updating all of the file servers Therefore a problem in the art is that there is no inexpensive apparatus and method to provide an Inter net ID to LAN clients that do not have writable non volatile memory SUMMARY OF THE INVENTION This problem is solved and a technical advancement is achieved in the art by a method and apparatus that 10 35 40 45 55 65 2 provides internetwork identification data for LAN cli ents Advantageously this invention receives a broad cast message on a LAN wherein the message comprises a request for an internetwork ide
22. the client in box 410 Processing then returns at balloon 406 If in decision diamond 408 the address was not in the address table then processing continues to box 412 where a diagnostic message is issued The diagnostic message is in the preferred embodiment a message sent through the IO port 275 to the control terminal 117 However the diagnostic message may be sent to the address found in the message packet indicating a failure or a message may be sent via LAN 110 to file server 150 and the failure logged Processing then proceeds to the return balloon 406 FIG 5 shows the service serial port subroutine Ser vice serial port subroutine is directed towards control of a terminal such as terminal 117 FIGS 1 and 2 How ever it would also be possible for the subroutine to control the router or accept local area network input as is known in the art Processing starts at at box 500 where the main menu is displayed on the screen Pro cessing continues to decision diamond 502 where a test 5 287 103 7 is made for serial input from keyboard If there is serial input from the keyboard then processing returns in balloon 504 If in decision diamond 502 there is serial input from keyboard then processing continues to box 506 where an input line is retrieved from the keyboard Processing continues to decision diamond 508 where a test is made if the input request is to update the address table If the input is not to updat
23. to a file server and means responsive to a message from said file server for updating said second means 12 On a LAN a terminal without storage of an internetwork identi fication necessary to permit communication to and from it outside said LAN storing means on said LAN for storing said internet work identification unique to said terminal and translating means for monitoring broadcast messages on said LAN from said termina and for responding to selected broadcast messages from said terminal by delivering a message to said terminal compris ing said internetwork identification from said stor age means
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