United States Patent [191
`Hirviniemi
`
`USOO5802285A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,802,285
`Sep. 1, 1998
`
`[54] WIDE AREA NETWORK (WAN) INTERFACE
`FOR A TRANSMISSION CONTROL
`PROTOCOIJINTERNET PROTOCOL (TCP/
`]P) IN A LOCAL AREA NETWORK (LAN)
`
`[75] Inventor: Seppo Hirviniemi, Helsinki, Finland
`_
`_
`_
`[73] AS51311”: lg‘ Perm“! Symms 0?’ Hclsl'lkla
`Fmhmd
`
`[21] APPL NO-I 948,602
`.
`_
`[22] F?ed'
`
`Oct‘ 10’ 1997
`
`-
`R
`.
`elated U'S App?umon Data
`[63] Continuation of Ser. No. 689,240,Ang. 6, 1996, abandoned,
`which is a continuation ofSer. No. 375,176, Jan, 13, 1996,
`abandoned, whichis a continuation of Ser. No. 67,579, May
`28, 1993, abandoned.
`.
`.
`.
`.
`Foreign Application Priority Data
`[30]
`May 29,1992 [FI]
`Finland
`
`922484
`
`5,426,637
`
`6/1995 Derby et a1. .......................... .. 370/401
`
`FOREIGN PATENT DOCUMENTS
`
`A465201 1/1992 European Pat. Off. .
`
`UT HER PUBLICATIONS
`
`“Architecture and Design of an Open Systems LAN/WAN
`Gateway” Johansen et al, IEEE, 1988, pp. 112-119.
`“Performance Analysis of a LAN/WAN Bridging Architec
`ture" Rodrigues et a1, IEEE, 1989, pp. 0646-0650.
`“Some Experience with LAN Interconnection via Frame
`Relaying” Iarnont et a1, IEEE, 1989, pp. 21-24.
`Examiner’s Search Report re GB 93110591 (1 p.) Aug. 18,
`1993 United Kingdom
`IBM Technical Disclosure Bulletin, ‘101.36, No. 0613, pp.
`61-57, Jun- 1993
`Proc. IEEE, vol. 79, No.2, Inspec. Abstract B 91033950 (1
`pg) Fell 1991 U_S_A_
`
`Primary Examiner-Parshotam S. Lall
`Assistant E
`.mr_vict Vu
`Ammo; Agent, or Firm-Fitch, Even, Tabin & Flannery
`
`[51] Int. cl.6 ........................... ..
`
`. .
`
`G06!‘ 13/00
`
`[57]
`
`ABSTRACT
`
`[52] US. Cl.
`
`395/2003;
`
`of
`
`......................... 395/200‘49’ 290'6’ 200’62’ 200's’ 680’
`
`681’ 682’ 500’ 370/401’ 469’ 903’ 911
`
`[56]
`
`References Cited
`U5, PATENT DOCUMENTS
`,
`$331,312 21990 H11] 32]. ................................ 370/403
`{159949
`1991
`‘
`,
`,592 10/1992
`5,179,554
`1/1993
`5,251,205 10/1993
`5,251,213 10/1993
`5,309,437 5/1994
`
`Thc invan?on relatcs to a method for jamming 3 ms_
`mission control protocol/internet protocol (‘PCP/1P) area
`
`a MAC an: nctwork to a network The TCP/IP software uses a lower-level address resolution
`
`
`
`
`protocol (ARP) protocol to ?nd physical network addresses
`corresponding to logical intn'net protocol (IP) addresses,
`and a lower-level IP protocol to transfer useful tra?ic in IP
`data packets. In the invention, the media access control
`(MAC) manage" of the wide area network (3) simulates
`opaa?on
`the ARP Fowl towards ‘ha
`TCP/[P software, and transmits and receives only IP data
`.
`.
`.
`packets over the wide area network (3) m a manner speci?c
`t0 the
`area network.
`
`6 Claims, 4 Drawing Sheets
`
`RAWS
`
`3
`
`R0
`
`59
`
`ws
`
`Token Ring , Ethernet
`
`2
`
`R0
`
`1
`
`Token Ringjthernet
`
`05” LA" MANAGER
`
`""5
`
`SR
`
`NETBIOS
`
`NDIS
`
`TEPI 1P
`
`MAE
`
`lNa
`
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`US. Patent
`
`Sep. 1, 1998
`
`Sheet 1 of 4
`
`5,802,285
`
`RAWS
`
`SR
`
`WS
`
`Token Ring . Hherne’r
`
`Tokén Ring , Efherne’r
`
`WS
`
`SR
`
`FIG. 1
`
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`U.S. Patent
`
`Sep. 1, 1993
`
`Sheet 2 of 4
`
`5,802,285
`
`05/2 LAN MANAGER
`
`TcP/ 1P
`
`METBms
`
`‘
`
`NDlS
`
`MAC
`
`iva
`
`FIG. 2
`
`05/2 LAN MANAGER
`
`TCPIIP
`
`IP ROUTER
`
`NETBms
`
`‘NDIS
`
`TOK
`MAE
`
`“0'5
`
`ETH
`MAE
`
`WAN MAc
`
`‘"3
`
`ETHERNET LAN
`
`TOKEN RING LAN
`
`FIG. 3
`
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`US. Patent
`
`Sep. 1, 1998
`
`Sheet 3 of 4
`
`5,802,285
`
`TRANSMIT CHAIN
`
`NDIS
`
`A
`
`B
`
`c
`
`J
`
`D
`
`FIG. 4A
`
`F|G_ 45
`
`D1
`
`D2
`
`D3
`
`. D4
`
`REQUEST
`
`E1 FIG. 40
`I
`
`E1
`1
`
`E2
`
`E3
`
`E4
`
`REPLY
`
`F
`
`E
`
`H
`G
`FIG. 4D
`
`NDIS
`
`' RECEIVE LOOK AHEAD
`
`FIG. 4
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`Sep. 1, 1998
`
`Sheet 4 of 4
`
`5,802,285
`
`% NDIS
`
`K1
`FIG. 5A
`
`K2
`
`K3 ip-header
`
`ip-dafa
`
`FIG. 5B
`
`ip-header
`
`ip-da’ra
`
`FIG. 5C
`SDLC header
`
`SDLC DATA (ip header&da’ra
`
`SDLC Link
`
`FIG. 5
`
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`1
`WIDE AREA NETWORK (WAN) INTERFACE
`FOR A TRANSMISSION CONTROL
`PROTOCOIJINTERNET PROTOCOL (TCPI
`I?) IN A LOCAL AREA NETWORK (LAN)
`
`‘This application is a continuation, of application Ser. No.
`08/689,240 ?led Aug. 6, 1996, which is a continuation of
`Ser. No. 08/375,176 ?led Jan. 18, 1996, which is a continu
`ation of Ser. No. 08/067,579 ?led May 28, 1993 all now
`abandoned.
`
`15
`
`20
`
`2
`to a WAN, thus enabling a more efficient utilization of
`WANs than previously.
`According to the invention, the MAC manager of the
`WAN simulates operation complying with the ARP protocol
`5 towards the TCP/IP software, and transmits and receives
`only IP data packets over the WAN in a WAN-speci?c
`manner.
`The basic idea of the invention is that the WAN MAC
`manager controlling tra?ic over the WAN simulates opera
`tion LAN workstation complying with the ARP protocol
`towards the TCP/lP application program. Accordingly, when
`the TCP/IP application program transmits an ARP request
`message to the MAC managm' so as to request a physical
`destination address (network address) corresponding to the
`1P destination address, the MAC manager responds with an
`appropriate reply message which, however, contains an
`arbitrary physical address for said I? address. The TCP/IP
`application assumes to have received a reply and an appro
`priate address from another computer connected to the LAN
`and starts to transfer useful data with the other computer in
`compliance with the IP protocol. It thereby transmits IP data
`packets provided with its own address and the above
`mentioned arbitrary physical address. The MAC manager
`identi?es the IP packets, removes the above-mentioned
`physical addresses and other possible LAN control data and
`transmits only the 1P data packet over the WAN in a
`WAN-speci?c manner. correspondingly, the IP data packets
`are exn'acted from data received over the WAN and provided
`with the physical address of the TCPIIP application and the
`above-mentioned arbitrary address, and then transmitted to
`the TCP/IP application program The WAN is thus all the
`time transparent to the TCPIIP application, and the operation
`of the TCP/IP application is equal to communication over a
`normal LAN.
`The invention is very easy and economical to implement
`as modi?cations and extra functions are required only in the
`MAC
`The TCP/IP applications and WAN s com
`munication can be accomplished in a conventional way.
`
`FIELD OF THE INVENTION
`The invention relates to interfacing a TCP/IP
`(transmission control protocol/interact protocol) software of
`a local area network (LAN) to a wide area network (WAN)
`via a media access control (MAC) manager when the
`TCP/IP software utilizes a lower-level ARP (address reso
`lution protocol) protocol to adapt physical network
`addresses to logical IP addresses, and a lower-level IP
`protocol to transfer useful tra?ic in II’ data packets.
`BACKGROUND OF THE INVENTION
`Computers can be interconnected to form various com
`puter netwrx'ks generally called 10ml area networks (LAN).
`Ethernet and Token Ring are the most typical types of LAN.
`The equipment connected to the LAN may be a workstation,
`a server, a bridge, a router, etc. Computer application
`programs may use various network protocols to communi
`cate with each other over the LAN. One such network
`protocol is TCP/IP (Transmission Control Protocol/Internet
`Protocol), which is used widely in equipments from di?'erent
`manufacturers especially in the UNIX operating system but
`also in the MS-DOS and 030 operating systems. TCP/IP is
`a protocol family consisting of a number of layered proto
`cols complying with the Open Systems Interconnection
`(OSI) model speci?ed by the International Standards Orga
`nization (ISO). The most important OSI layers are the
`transmission protocol layer (layer 4) and the network layer
`(layer 3). When the IP protocol is used in a LAN (Ethernet,
`Token Ring, FDDI), an ARP (Address Resolution Protocol)
`is needed to ?nd a physical LAN address (or more correctly
`an MAC address) corresponding to the requested IP address.
`‘Typically, each compute" maintains an ARP database from
`which it can look up the physical destination address for to
`the logical IP destination address. If the physical destination
`address cannot be found in the ARP database, the computer
`transmits a specialARP request message to the LAN so as
`to request a computer identifying the IP address to transmit
`the respective physical destination address.
`It may also be advantageous that a workstation remote
`from the LAN (a remote workstation), or another LAN, can
`beconnectedtotheLAN.Duetothelongdistanceitis
`thereby necessary to make the interconnection via a
`so-called wide area network (WAN). The simplest form of
`the WAN is an asynchronous modem link from the remote
`workstation to a network element. On the other hand, the
`WAN may also be established over a transfer network. The
`ARPprotocol is not needed ova’ the WAN as the WAN does
`not contain LAN addresses for which the respective IP
`addresses should be found. A remaining problem is that the
`TCP/IP software designed for the LAN always attempts to
`use the ARP protocol to ?nd out the correspondence between
`the addresses. TCP/IP software utilizing an MAC-level
`interface cannot therefore operate directly over the WAN.
`DISCLOSURE OF THE INVENTION
`The object of the present invention is to enable a computer
`using aTCP/IP software designed for a LAN to be interfaced
`
`30
`
`35
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`In the following the invention will be described in ma'e
`detail by means of illustrating embodiments with reference
`to the attached drawings, in which
`FIG. 1 illustrates schematically a LAN inta‘connected
`with another LAN or another remote workstation over a
`WAN according to the invention;
`FIG. 2 illustrates a workstation provided with a MAC
`manager according to the invention;
`FIG. 3 illustrates a router provided with a MAC manager
`according to the invention;
`FIGS. 4A, 4B, 4C and 4D refen'ed collectively as FIG. 4
`illustrate the simulation of an ARP protocol; and
`FIGS. 5A, 5B, and 5C referred collectively as FIG. 5
`illustrate the transfer of useful tra?ic.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`The invention will be described below by way of example
`with reference to Ethernet LANs, but the invention may also
`be applied to other types of LANs, such as Token Ring. FIG.
`1 shows two separate Ethernet LANs l and 2 both having a
`plurality of associated workstations WS and servers SR
`(FIG. 1 shows only a few units for the sake of clarity). The
`workstations WS may be any computers, such as the MIK
`ROMIKKO 4 from ICL Personal Systems Ltd. The servers
`SR may be e.g. printas, disk drives, routm's R0 or work
`
`45
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`3
`station servers implemented by computers. The workstations
`and servers are typically supported by the UNIX, 05/2 or
`DOS operating system.
`The routers RO connect together the geographically sepa
`rate LANs 1 and 2 by means of a WAN. The WAN3 may
`be any connection, such as a telephone line, X.25 line, leased
`line, asynchronous link, SNA network. In addition, an
`asynchronous remote workstation RAWS is connected to
`both LANs over the WAN 3.
`In the preferred embodiment of the invention, the network
`software of the remote workstation RAWS is such as shown
`in FIG. 2. As used herein the network software refers to
`system software needed to make the workstations and serv
`m's communicate with each other. There are two main types
`of network software: network operating systems and tele
`communication software. The network operating system is
`usually an application program in a server and requires its
`own counterpart at the workstation. The network operating
`system is usually on the highest ISO level of hierarchy.
`Network operating-system softwares include e.g. IBM PC
`Lan Program, 0812 Lan Manager, and ICL MS Lan Man
`ager.
`Telecommunication software is intended for intra
`network communication. All workstations and servers con
`nected to the network have to use the same protocol. The
`remote workstation RAWS according to the invention uses
`'I‘CP/IP telecommunication software connected to the net
`work operating-system software via a NETBIOS interface.
`The TCP protocol is on the fourth level of ISO hierarchy, and
`the IP protocol is on the third level of ISO hiu'archy. The
`TCPIIP software uses the IP protocol on the lower level of
`hierarchy (OSI layer 3) to transfer useful tra?ic (payload) in
`IP data packets. It also uses the ARP (Address Resolution
`Protocol) to adapt the physical network addresses to the
`logical addresses used by the IP protocol. The ARP is
`described in the standard RFC-826: An Ethernet Address
`Resolution Protocol. The IP is described in the standard
`RFC-894: Standard for the Transmission of IP Datagrams
`over Ethernet Networks. Typically each computer maintains
`anARPdatabasefromwhich itcanlookupan
`physical destination address on the basis of the logical IP
`destination address. If the physical destination address can
`not be found in the ARP database, the computer transmits a
`specialARPrequest messagetotheLAN so astorequest a
`computa- identifying the IP address to transmit the respec
`tive physical destination address.
`The next lower OSI layer (layer 2) uses an MAC (Media
`Access Control) manager software which controls tra?ic
`over the su'ial WAN 3. The TCP/IP software and the MAC
`software are intaconnected via an NDIS interface. The
`NDIS interface is described in the Microsoft/3Com Network
`Driver Interface speci?cation. Below the MAC manager
`there is a physical layer (081 1) comprising a physical
`transfa path and a physical interface to it.
`The TCP/IP software assumes that the network utilized on
`the transfer network level is a LAN (in this speci?c case
`Ehernet) while the MAC manager, in fact, operates in a
`WAN environment. According to the invention, the MAC
`manager simulates operation of LAN workstation comply
`ing with the ARPprotocol and the Ethernet frame format in
`communication towards the TCP/IP software so that the
`TCP/IP software assumes that it is connected to the Ethernet
`network. An example of this ARP simulation is shown in
`FIG. 4, where the MAC manager responds to the ARP
`request. The TCP/IP software transmits the ARP Request
`packet shown in FIG. 4A to the MAC manager by the NDIS
`
`55
`
`4
`command TransmitChain. The packet is transmitted in order
`to ?nd out the physical address corresponding to the
`requested IP address. As shown in the ?gure, the ARP
`Request packet contains the ?eld A of the physical destina
`tion address (in this speci?c case an empty location for the
`requested physical destination address), the ?eld B of the
`physical source address (the physical address of the TCP/IP
`software), the type ?eld C of the ARP message, and the ARP
`frame D. As shown in FIG. 4B, the ARP frame D contains
`e.g. a physical source address D1, an IP source address D2,
`a physical destination address D3 (unknown) and an IP
`destination address D4. The MAC manager assembles an
`ARP Reply frame E shown in FIG. 4C from the received
`ARP Request frame D. An arbitrary 6-byte constant is
`inserted to the frame E as a physical source address E1; the
`1? source address E2 will be the IP destination address D4
`of the frame D; the physical destination address EB will be
`the destination address D1 of the frame D; and the IP
`destination address E4 will be the IP source address D2 of
`the frame D. The NDIS command ReceiveLookAhead illus
`trated in FIG. 4D is then formed by incorporating the ARP
`type ?eld F, the physical source address G (equal to E1) and
`the physical destination address H (equal to E4) to the ARP
`frame E.
`After having received the message of FIG. 4D, the TCP/IP
`software assumes that the ARP request has been successful
`and starts to transmit IPpackets to the MAC manager, which
`is illustrated in FIG. 5. FIG. 5A shows a packet K transmit
`ted by the TCPIIP software via the NDIS intu'face, the LAN
`control data comprising a physical destination address K1
`(equal to D1), a physical source address K2 (equal to D3),
`anlPtype KBandanIPpacketcontainingthe header
`IP-Header and IP data. The MAC manager extracts the LAN
`control data from the IP packet, as shown in FIG. 5B, and
`inserts the 1? packet in the data ?eld of the SDLC packet,
`which is preceded by the SDLC-Header when the WAN is
`an SDLC link (Synchronous Data Link Control) e.g. in an
`SNA network (Systems Network Architecture), as shown in
`FIG.5C.IftheWAN3isanX25link,theIPpacketis
`transmitted in the data ?eld of the X25 packet. If the WAN
`3 is an asynchronous connection, the 1P packet is SLIP
`encoded before being transmitted SLIP encoding is speci
`tied in the standard RFC-1055: Non-Standard for Transmis
`sion of IP Datagrams over Serial Lines.
`Correspondingly, when SDI£ data packets are received
`from the WAN 3, the MAC manager executes procedures
`inverse to those shown in FIG. 5: the MAC manager extracts
`the WAN control data (SDLC-Header) from the IP data
`packets andprovidesIPdatapackets withtheLAN control
`data and then transmits the packets to the TCPIIP software.
`FIG. 3 illustrates the implementation of the invention in
`a server computer operating as a routs such as the router R0
`in FIG. 1. In the embodiment of FIG. 1, the TCP/IP software
`is connected to the IProuter via the NDIS interface. The IP
`router in turn is connected via anotha' NDIS interface to the
`WAN MAC manager, the Token Ring LAN MAC manager,
`and the Ethernet LAN manager. The IProuter is able to route
`normal tra?ic complying with the ARP and IP protocols
`between the MAC managers and between the MAC man
`agers and the TCPIIP software. Communication between the
`TCP/[P software and the WAN MAC manager takes place as
`described above with reference to FIG. 4.
`The ?gures and the description related to them are only
`intended to illustrate the present invention. In its details, the
`method according to the invention may vary within the
`scope of the attached claims.
`
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`6
`I claim:
`2. A method according to claim 1, wherein useful tra?c
`is transferred from the LAN to the WAN by the steps
`1. A method of interfacing a transmission control
`comprising:
`protocollinternet protocol (TCP/IP) software designed for a
`providing IP data packets at the LAN with LAN control
`local area network (LAN) to a wide area network (WAN),
`data;
`the WAN having a media access control (MAC) manager,
`transmitting, by said TCP/IP software, the IP data packets
`the TCP/IP software utilizing a lower-level address resolu
`provided with the LAN control data to said MAC
`tion protocol (ARP) to ?nd physical network addresses
`manager,
`corresponding to logical internet protocol (IP) addresses,
`extracting, by said MAC manager, said LAN control data
`and the TCPIIP utilizing a lower-level IP protocol to transfer
`from said transmitted 1P data packets;
`useful trai?c in IP data packets, comprising the steps of:
`providing, by said MAC manager, said I? data packets
`simulating, by said MAC manager, operation complying
`with WAN control data; and
`with the ARPprotocol between said MAC manager and
`transmitting, by said MAC manager, over said WAN said
`said TCP/IP software in the direction towards said
`[P data packets provided with WAN control data.
`TCPIIP software, and
`3. A method according to claim 1, wherein useful tral?c
`transmitting IP data packets over the WAN, from and to
`is transferred from the WAN to the LAN by the steps
`said MAC manager, in a manner appropriate to the
`comprising:
`WAN rather than the LAN, and wherein the simulating
`providing IP data packets at the WAN with WAN control
`step comprises the following steps:
`data;
`requesting, by said TCPIIP software, a physical address
`transmitting the [P data provided with the WAN control
`for a component of the WAN whose IP address is
`data to said MAC manager;
`known by transmitting a request message complying
`extracting, by said MAC manager, said WAN control data
`with said ARP protocol to said MAC manager, said
`from said transmitted IP data packets;
`request message containing, as a physical source
`providing, by said MAC manager, said IF data packets
`address, the physical address of a component of the
`with LAN control data; and
`LAN; and as an 1? source address, the IP address of
`transmitting, by said MAC manager, over said LAN said
`said component of the LAN; and as an IP destination
`IF data packets provided with LAN control data.
`address, said IP address of said component of the
`WAN, and
`4. A method according to claim 1, wherein said WAN is
`transmitting, by said MAC manager, to said TCPIIP
`a synchronous data link control (SDLC) link, and said IF
`3° datapacketistransmittedinadata?eldofanSDLC?ame.
`software a reply message complying with said ARP
`5. A method according to claim 1, wherein said WAN is
`protocol and containing, as a physical source
`anXJSIinkandsaidIPdatapacketistransmittedinadata
`address, an arbitrary constant corresponding to said
`physical address of said component of the WAN; as
`?eld of an X25 data packet.
`6. A method according to claim 1, wherein said WAN is
`an IP source address, said IP address of said com
`an asynchronous link, and said I? data packet is SLIP
`ponent of the WAN; as a physical destination
`address, said physical address of said component of
`encoded prior to transmission.
`the LAN; and as an IP destination address, said 1?
`address of said component of the LAN.
`
`* * *
`
`35
`
`III
`
`III
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`IPR2016-00726
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`

`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`
`5'8O2’285
`PATENTNO.
`l, 1998
`:
`DATED
`|NVENTOR(S): Seppo HIRVINIEMI
`
`It is certified that error appears in the above-indentified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`On the title page,
`item
`[63] line 2, following “Ser., No. 375,176" change
`"Jan. 18, 1996," to ——Jan. 18, l995,——.
`
`Signed and Sealed this
`Twenty-?fth Day of May, 1999
`
`Arresting O?FIICQI'
`
`Acting Cnmmixsioner 0]" Parents and Trademarks
`
`Q. TODD DICKINSON
`
`IPR2016-00726
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`2K, ROCKSTAR
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