CA2226189C - Method and apparatus for synchronizing data transmission with on-demand links of a network - Google Patents
Method and apparatus for synchronizing data transmission with on-demand links of a network Download PDFInfo
- Publication number
- CA2226189C CA2226189C CA002226189A CA2226189A CA2226189C CA 2226189 C CA2226189 C CA 2226189C CA 002226189 A CA002226189 A CA 002226189A CA 2226189 A CA2226189 A CA 2226189A CA 2226189 C CA2226189 C CA 2226189C
- Authority
- CA
- Canada
- Prior art keywords
- link
- router
- packet
- node
- network
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/66—Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/40—Network security protocols
Abstract
A novel synchronization mechanism synchronizes delivery of data packets over on-demand links of a computer network in a manner that efficiently utilizes those links. The mechanism comprises control information generated by a sour ce node and stored in a network layer header of a data packet transmitted to a destination node via at least one router coupled to an on-demand link of the network. Depending upon the state of the control information the router is instructed whether to immediately dial the link to establish a connection fo r delivery of the packet to the destination node.
Description
CA 02226189 1998-01-0~
W O97/02691 PCTrUS96/11202 METEOD AND APPARATUS FOR SYNCEIRONIZING DATA TRANSMISSION
WIT~ ON-DEMAND LINKS OF A NETWORK
EIELD OF T~E INVENTION
This invention relates generally to conl~uLer neLwulhs and, more particularly, to efficient ~ltili7~tion of on~ om~nd communication links of a computer network.
BACKGROUND OF T~E INVENTION
A computer network is a geographically distributed collection of hlLel con,.ected c~ .. l.:~~ti~-n links for transporting data between nodes, such as computers. A plurality of c~ nt;~wulh~ may be further interconnected by intermedi~te nodes, or routers, to eYtend the ~ ;live "size" of the nG~wolk~, smaller groups of which may be m~int~ined as an autonomous system or domain of nodes. These nodes typically communicate by ~Yt~h~nging discrete "packets" of data according to predefined protocols. In this context, a protocol consists of a set of rules defininp how the nodes interact with each other.
The co~ ic~tion links forming the networks may be perm~nently installed to theiri,lLercol-l-ected nodes, as in the case of an Fth.ornet communications system, or they may be dial-up lines of a switched telephone network that remain ordinarily unconnected These dial-up lines are typically "brought-up", i.e., dialed, by the routers to initiate node-to-node c~ mml-nication on-demand; accordingly, these lines are also known as on-demand links. An f~Y~mple of a network that utilizes on-demand links is the Integrated Services Digital Network (ISDN).
In order to reduce design complexity, most nelwolk~ are organized as a series ofhaldw~; and sonw~le levels or "layers" within each node. These layers interact to format data for transfer between, e.g., a source node and a destination node communicating over the ~ ne~wulL. Specifically, predetermined services are performed on the data as it passes through each layer and the layers communicate with each other by means of the predefined protocols.
This layered design permits each layer to offer selected services to other layers using a CA 02226189 1998-01-0~
W O 97/026g1 PCT~US96/11202 dardi~ed int~ ce that shields those layers from the details of actual imrl~ l;on ofthe services.
In an attempt to standardize network architectllres, i.e., the sets of layers and protocols used within a I~GLWV1k~ a generalized model has been proposed by the International Standards s O,~;an~lion (ISO). The model, ealled the Open Systems Interconnection (OSV reference model, is direeted to the intereonneetion of systems that are "open" for eommllnie~tion with other systems. The proposed OSI model has seven layers whieh are termed, in ~ccçnding interf~f~.ing order, the physical, data link, net~ork, ~ransport, session, presentation, and ~plication layers. These layers are arranged to form a "protocol stack" in each node of the network.
Fig. 1 illustrates a s~hlom~tie bloek diagram of prior art protocol stacks 125 and 175 used to transmit data between a souree node 110 and a destination node 150, respectively, of a e~ mpllt~r network 100. Each protocol stack is structured aecording to the OSI seven-layer model; acco-di,-gly, each staek comprises a collection of protocols, one per layer. As can be seen, the protoeol stacks 125 and 175 are physieally connected through a commlmie~tions ehannel 180 at the physical layers 124 and 16~. For ease of description, the protoeol staek 125 will be deseribed.
Broadly stated, the physical layer 124 transmits a raw data bit stream over a eoll..-lu.lieation ehannel 180, while the data link layer 122 manipulates the bit stream and I.~n:irolll-s it into a datastream that appears free of tr~ncmiccion errors. This latter task is ~ecompli.ched by dividing the tr~ncmitted data into frames and tr~ncmittin~ the frames sequentially, aeeompanied with error eorrecting me~h~ni.cmc for detecting or correeting errors.
The network layer 120 routes data packets from the source node to the destination node by s~leeting one of many alternative paths through the physical network. The transport layer 118 aeeepts the datastream from the session layer 116, apportions it into smaller units (if necessary), passes the smaller units to the network layer 120 and provides appropriate mer.h~nicmc to ensure that all the units arrive correctly at the d~stin~tion.
The session layer 116 establishes data transfer "sessions" between software processes on the source and destin~tion nodes, along with management of such sessions in an orderly fashion.
CA 02226189 1998-01-0~
W O 97/0201 PCTrUS96/11202 That is, a session not only allows ol.linaly data transport between the nodes, but it also provides enh~nred services in some applications. The pres~;..lalion layer 114 performs frequently-requested functions relating to the presentation of transmitted data, incl~ ing encoding of data into ~ dald formats, while the application layer 11 2 contains a variety of protocols that are co~ lonly needed by processes e~ecuting on the nodes.
Data tran.cmi.~.~ion over the network 100 therefore consists of generating data in, e.g., a sending process 104 Px~c~ltin~ on the source node 110, passing that data to the application layer 112 and down through the layers ofthe protocol stack 125, where the data are sequentially follll~LLed as a packet for delivery onto the channel 180 as bits. Those packet bits are then Ll~ ed to the protocol stack 175 ofthe destin~tion node 150, where they are passed up that stack to a receiving process 174. Data flow is s~.henn~tically illustrated by solid arrows.
Although actual data tr~n~mi~cion occurs vertically through the stacks, each layer is prograrnmed as though such tr~n~mi.~ion were horizontal. That is, each layer in the source node 100 is programmed to transmit data to its corresponding layer in the destination node 150, as srhrm~tic~lly shown by dotted arrows. To achieve this effect, each layer of the protocol stack 125 in the source node 110 typically adds information (in the form of a header field) to the data packet generated by the sending process as the packet descends the stack. At the destin~tion node 150, the various headers are s*ipped offone-by-one as the packet propagates up the layers of stack 175 until it arrives at the receiving process.
As noted, a significant function of each layer in the OSI model is to provide services to the other layers. Two types of services offered by the layers are "connection-oriented" and ''connectiQnlee.C~ network services. In a connection-oriented service, the source node establishes a connection with a destin~tion node and, after sending a packet, terminates the cQ~ e~il;Qn The overhead ~cori~ted with establishing the connection may be unattractive for nodes requiring efficient communication performance. For this case, a fully connectionless service is desirable where each tr~n.cmitted packet carries the full address of its destin~tion through the network.
Network layer protocols are generally used to implement a connectionless networkservice, the latter of which primarily defines a packet format. When the network layer receives CA 02226l89 l998-Ol-0~
WO 97/02691 PCTrUS96/11202 a packet from the transport layer for tr~ncmiccion over the network, it adds (to the paeket) a header ec,. ~ E, inter alia, souree and dçctin~tion addresses. ~xamples of n~lwol k layer protoeols are the eonnectionless network layer protoeol (CLNP) defined by ISO, the Internet (IP) IwLwolk layer protoeol and the Internet Packet Fxeh~nEe (IPX) protoeol.
The overall packet formats of the CLNP and IP headers may be .oxt~n~led to ~ee~ mmodate added re~Lu- c;s by way of option fields contained within the headers defined by the network layer services. The types of options supported by these fields typieally include souree routing, priority and security-specific inrollnalion. However, the conv~ntion~1 IPX
header format is generally not exr~nd~hle since its header was not designed to aecomodate appended fields in a manner that is eomp~tihle with the rçm~ining fields of the paeket.
As also noted, a router is used to bring-up an on-demand link of a network typieally in response to the reeeption of a data packet int~nrled to be forwarded over the link. However eaeh time the link is dialed, eonnection charges are incurred. Certain types of data packets are ~Yçh~nEed in accordance with non-time critieal applications, such as synchronizing distributed lS ~t~h~Ces with respeet to direetory serviees. This type of computer-to-computer traffic is flexible as to when packet tr~ncmiccion oceurs and the present invention is direeted to ~y~lcll~ul~i~in~ delivery of sueh traffc until times when the on-demand link is dialed for other eompelling reasons.
SUMMARY OF T~E INVENTION
The invention comprises a ~.. eç1~ icm for synchronizing delivery of types of data packets over on-demand links of a computer network in a manner that efficiently utilizes those links. The novel synchronization mer.h~nicm comprises control information generated by a souree node and generally stored in a network layer header of a data packet tr~ncmitted to a d~ctin~tion node via at least one router coupled to an on-demand link of the network.
2s Depending upon the state of the eontrol information, the router is instrueted whether to imme~ tloly dial the link to establish a eonneetion for delivery of the paeket to the dçstin~tion node.
CA 02226l89 l998-Ol-0~
W O 97/02691 PCTrUS96/11202 Plt;r~ably, the control i~ ion is incol~ol~led within the network layer header as an option. In the case of network layer headers that support option fields, such as the clml-~ Sr nt;lw~lh layer protocol (CLNP) and the Internet (IP) network layer protocol headers, a new option type is defined for on-demand links. The Internet Packet Fx~h~l~g~
(rPX) protocol header, however, does not accomodate option fields and, thus, a nGlw~
addressing ~l~i-g~ is provided that e~p~nd~e the forrnat of this header to support the novel control il~llllaLion, e.g., a flag, as an option.
In the illustrative embodiment of the invention, if the novel flag is asserted, the router is instructed "not to dial the on-demand link". When the router receives a data packet with an o asserted flag, it stores certain information contained in the packet that is sufflcient to identify the sending process within a source node and discards the r~m~in-1çr ofthe packet prior to sending a return packet to the source. The return packet preferably in~.hldes complete source and d~etin~tion addresses of the data packet, i.e., inforrnation sufficient to identify a process within the source node sending that packet, along with a reason for returning that packet (e.g., "on-demand link not currently dialed"). Furthermore, the router keeps track of these source and d~etin~ti~)n addresses so that when it eventually brings-up the link, it can send a subsequent notification packet to the source indicating that the on-demand link is currently available for tr~n.emieeinn ofthe data packet to the dçstin~tinn.
Synchrol~alion of particular types of data packets, e.g., periodically ll ;1. .e. . .;1 l ed data packets that are not time critical, with an on-demand link may be further realized by requiring the source node to periodically poll the router to test whether the link is connecte~1 This terhni1ue is less optimal than that of the illustrative embodiment because of an increase in network bandwidth neceseit~ted by the polling traffic; however, it may be useful as a backup me~h~niem in the event the router "crashes" and loses the information needed to identify the sending process within the source node.
In an alternate embodiment, the router may store the data packet with the asserted flag and, when the on-demand link is subsequently dialed, send the packet to the dçstin~tion node.
For this embodiment, the router is not required to notify the source node that the link was previously unavailable and that the data packet was temporarily stored at the router. Although CA 02226189 1998-01-0~
WO 97/02691 P~liU~'.S/11202 this approach reduces traffic between the router and source node, it may result in "stale" data being l~l-e- ~;1 led to the destin~tion node if the latency incurred waiting for the link to be c~)nn~cted is subst~ntis~l In yet another embodiment ofthe invention, the router may l~ ----l a mllltic~ct m~e.e~e s to all nodes of the network when the on-demand link is up. Here, the mlllti~.~et m~ec~e cc~ ins the novel control i.~..--~lion which alerts sending processes of recipient source nodes that "the on-demand link is ~;ullGIllly available for data tr~n~miC~ion" The control i- ro-ll.~lion further contains h~l.--alion sufficient to notify the source nodes as to which d.~stin~tiQn nodes are available over the link.
In response to the multicast mee~g~, any source node wishing to l-~ .. il h rc,llllalion over that link may then send a data packet to the router. One advantage of this embodiment is that the router need not retain the source and destin~tion addresses of every data packet ed for an inactive on-demand link; another advantage is that source nodes need not initiate data l,~ ----e~i;on over the link until they receive the multicast message.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like nces indicate similar elements, and in which:
Fig. 1 is a schematic block diagram of prior art protocol stacks used to transmit data between a source node and a destin~tion node of a computer network;
Fig. 2 is a block diagram of a network system including a collection of computer1IG~WUIk~ connected to a plurality of nodes;
Fig. 3 is s~h~m~tic block diagram of a system having a plurality of domains interconnected by an on-demand link in which a novel synchronization merh~ni~m ofthe present 2s invention may be advantageously used;
Figs. 4A - 4C are sch~m~tic diagrams of option fields of conventional network layer headers for storing the novel synchlolliGalion me~h~niem in accordance with the invention;
CA 02226189 1998-01-0~
W O 97/02691 rCTAUS96111202 Fig. S is a srh~m~tic diagram depicting the forrnat of a conventional IPX nc;Lw~lk layer header; and Fig. 6 is a schf~m~tic diagram illustrating an improved format of the IPX network layer header for storing the novel syncl~ol~i~lion m~rh~ni~m according to the invention.
s DETAll ,F.n DESCRrPTION OF ILLUSTRATIVE EMBODIMENT
Fig. 2is a block diagram of a network system 200 comprising a collection of co~ uLer ~elw~lk~ connected to a plurality of nodes. The nodes are typically general-purpose computers comprising a source node S, an end node N, a destin~tion node D and a plurality of interm~ te nodes R1-R2. Each node typically comprises a central processing unit (CPU) 202, a memory unit 204 and at least one network adapter 206 interconnected by a system bus 210. The memory unit 204 may comprise storage locations typically composed of random access memory (RAM) devices, which are addressable by the CPU 202 and network adapter 206. The memory unit typically provides temporary storage of information, such as executable processes and collLenLs of data packets, as described further herein. An operating system, portions of which are typically resident in memory and executed by CPU, functionally organizes the node by, inter alia, invoking network operations in support of those processes executing in the CPU.
The computer networks inclnded within system 200 may range from local area networks (LANs) to wide area networks (WANs). A LAN is a limited area network, while a WAN may be a public or private teleco.. ~ tions facility that interconnects nodes widely dispersed using comml~nir~tion links. Communication among the nodes coupled to these networks is typically effected by exrh~nging discrete data"packets" specifying addresses of, e.g., source and destin~tion nodes. Since the system shown in Fig. 2 comprises a relatively small group of inte,comlected LANs 1-3, it is preferably m~int~ined as an autonomous domain. The intermediate nodes are preferably routers configured to facilitate the flow of data packets s throughout the domain 200 by routing those packets to the proper receiving nodes.
In general, when a source node S transmits a packet over LAN 1, the packet is sent to all nodes on that LAN. If the int~nded recipient of the packet is connected to LAN 3, the packet is routed through router R1, over LAN 2 and through R2 onto LAN 3. A key function CA 02226l89 l998-Ol-0~
WO97/02691 P~l/~',''11202 of a router is d~ the next node to which the packet is sent; this routing filnrtion is pl erel ~ y ~)e~ r ~ ed by n elwolk layer 260 of a protocol stack 250 within each node. Typically, the packet co..l~ two destin~tion addresses: the address ofthe final dçstin~ti~ n node and the address ofthe next node along the route. The final destin~tion address remains constant as the s packet ll~vel~es the l~elwolk~ while the next destin~tion address rh~ngeS as the packet moves from node to node along the route through the networks.
Sperifiç~lly~ when source node S sends a packet to dçstin~tion node D, i.e., the final ~lestin~tion address, the packet is L~ e(l onto LAN 1 with a next destin~fion address specifying the address of router R1. Address h~l ",~lion embedded in the packet, which is processed by the higher-layer software of the protocol stack 250, identifies the final riestin~tion of the packet as node D. Based on this information, R1 determines that the next node along the route is router R2 and proceeds to pass the packet onto LAN 2 for reception by that node.
Router R2 then determines that the next node is the final destination node D and transmits the packet over LAN 3 to node D.
Fig. 3 is a sch.?m~tic block diagram of a system 300 comprising a plurality of ~lom~inc 310 and 320 interconnected by a communication link 330 coupled to routers 312 and 322. The c~ ~-----.-~l;r~tion link 330 is plerel~bly a temporary link that may be "brought-up", i.e., dialed, by the routers to initiate node-to-node col"l,lu"ication on-demand; that is, on-demand link 330 may be embodied as a dial-up link of a switched telephone network that remains ordinarily unconnected In the illustrative embodiment, the on-demand link may comprise an Integrated Services Digital Network (ISDN) line, while the domains interconnected by the link may include in-~eprnflPnt Tntrrn~ot Packet F.xc~.h~n~e (IPX) networks, such as the Novell Corporate IPX
network and the Microsoft Corporate IPX network.
Typically, the router 312 dials the on-demand link 330 in response to the reception of a 2s data packet from source node S that is destined for destin~tion node D. Each time the link is dialed, though, connection charges similar to those of any switched telephone line are incurred.
Yet, certain types of data packets are L~ ed in accordance with non-time critical applications, such as electronic mail or synchronizing distributed ~l~t~hacçc associated with directory services. This type of computer-to-computer traffic is generally flexible as to when CA 02226l89 l998-Ol-0~
W O 97/02691 PCTrUS96/11202 data ~ ion occurs and, as noted, the present invention is directed to syncl~ol~,.g delivery of such traffic until times when the on-demand link is otherwise dialed.
For routers 312 and 322 to be used in system 300, the interconnected n~:Lw~),h~ must share the same network layer protocols and must be compatible at the higher protocol stack s layers. The ne~wo,k~ may, however, differ at the data link layer 362 and the physical layer 364, as shown s~ ic~lly in the protocol stack 3so of router 3 l 2. Although the routers may operate with any network layer protocol, in the illustrative embodiment described herein, the n~lw~lk layer protocols are preferably the connectionless network layer protocol (CLNP), the Tnt~rnet (IP) network layer protocol and the IPX protocol.
o As further noted, when the network layer 360 receives a data packet from the transport layer 358 for tr~n~mi~ion over the network, it adds a network layer header to the packet. The formats of these header fields are generally the same among all network layer services primarily because the same information are typically contained in each packet. Figs. 4A and 4B depict the formats of IP and CLNP network layer packets 410 and 450, respectively. It can be seen that both ofthese packets generally contain information pertaining to their headers 412 and 452 (e.g., length and ~hec~cllm fields); more particularly, though, each header inr.l~ldes an options field 426 and 466 to accommodate added features. The types of options supported by these fields typically include source routing, priority and security-specific information. Fig. 4C
depicts the general format of the contents of an options field 480 which comprises an octet (1-2c byte) option code field 482 that uniquely defines a type of option, a l-byte length field 484 in~lic~ting the length of the option in bytes, and a variable, e.g., 0-254 byte, value field 486.
However, the IPX protocol header does not accomodate option fields and, thus, the invention provides a network addressing arrangement that expands the format of this header.
Fig. 5 is a s~.h.om~tic diagram depicting the format of a conventional IPX packet 500 having a network layer header comprising ~ppl-~xill.ately 30 bytes. Specifically, the header contains, inter alia, hierarchical d~stin~tion and source addresses, each of which includes a plurality of address elements. For example, the destination address 510 comprises a 4-byte destin~tion nc:~wc,lh field 512 that indicates the particular network over which the packet will travel, a 6-byte d.o~tin~tion node field 514 identifying a data link layer address of the receiving node on that CA 02226189 1998-01-0~
WO 97/02691 PCT~US96/11202 nt;~w~lh and a 2-byte destin~tinn socket field 516 specifying the receiving process in the r~ceivillg node. Data field 530 is appended to the header, immP~ tely following the source address field 520.
Accol~ g to the addressing arrangement, a special socket value is provided that inr1ic~tçs the provision of additional header h~ro~ Lion after the source address field to e~t;~iLiv~ly create an i"~prov~d network layer header. Fig. 6 is a ~ch~m~tic diagram illustrating the format of the improved IPX network layer header 600. A source node substitutes the special socket value 656 for the actual destin~tion socket number within the 2-byte destin~tinn socket field 516 ofthe conventional dçstin~fion address field 510. Preferably, the special socket value instructs the routers to PY~mine the contents of e~p~n~1ed header fields 660 prior to rOl w~udulg packets over the networks.
In accordance with the invention, a mech~ni~m is provided for synchlolliGing delivery of particular types of data packets over on-demand links of a computer network in a manner that f~ffi~i,ontly utilizes those links. Referring now to Figs. 1-6, the novel synch~ fi~aLion mer.h~ni~m cc,l-",.ises control i,~"-l~lion generated by a source node, e.g., source node S, and stored in the network layer header of a data packet tr~n~mitted to a destin~tion node, e.g., destin~tion node D, via a router 312 coupled to on-demand link 330 of network system 300. Depending upon the state of the control information, the router is instructed whether to immer~i~tçly dial the link to establish a connection for delivery of the packet to the destination node D.
Preferably, the control information is incorporated within the network layer header as an option. In the case of the IP and CLNP network layer protocols whose headers contain option fields, a new option type is defined for on-demand links. Specifically, the new option type comprises an option code, e.g., "ODL", stored in field 482 that uniquely specifies an on-demand link, along with information stored in value field 486 instructing the router whether to dial the 2s on-demand link in response to reception of the packet. The total length of the option field 480 in bytes is indicated in the length field 484.
With respect to the improved IPX header 600, on the other hand, the control information is stored in a field 670 of the expanded header fields 660. Although the contents of the field comprising the control information may vary, preferably the field is provided as a novel CA 02226189 1998-01-0~
WO 97102691 PCT~US96/11202 flag 670 and the state of this flag instructs the router how to handle the on-demand link 330. In other words, when the router 312 receives a data packet having the special socket value, e.g., "SS", ~ubsLiLuLed for the actual destin~tion socket number of the destination address, the router s the contents of ~Yp~nrled header fields and, in particular, the state of the flag 670 prior to rO. v~alding the packet over the link 330.
In the illustrative embodiment of the invention, assertion of the flag preferably instructs the router "not to dial the on-demand link". If the flag is asserted, the router stores certain a~ion cnnt~ined in the packet and discards the remaining contents of the packet prior to sending a return packet to the source. The return packet preferably includes complete source o and destin~tion addresses ofthe data packet, i.e., information sufficient to identify a process within the source node sending that packet, along with a reason for returning that packet (e.g., "on-demand link not currently dialed"). Additionally, the router 312 temporarily stores the source and dçstin~tion addresses of the header in its memory 204 so that when it eventually brings-up the link 330, it can send a subsequent notification packet to the source node S
in~lic~ting that the on-demand link 330 is currently available for tr~n~mi~ion ofthe data packet to the destin~tion node.
In an alternate embodiment of the invention, the router 312 may store the entire data packet with the asserted flag 670 in its memory 204 (Fig. 2) and, when the on-d.-m~n~l link 330 is subsequently dialed, send the packet to the destin~tion node D in domain 320. For this embodiment, the router 312 is not required to notify the source node S that the link 330 was previously unavailable and that the data packet was temporarily stored at the router 312.
Although this approach reduces traffic between the router and source node, it may result in "stale" data being tr~n~mitted to the destination node D if the latency incurred waiting for the link to be connected is substantial.
2s In yet another embodiment of the invention, the router 312 may transmit a single multicast message to all nodes ofthe network when the on-demand link 330 is dialed and available. Here, the multicast message contains the novel control information which, when asserted, alerts sending processes of recipient nodes that "the on-demand link is currently CA 02226189 1998-01-0~
WO 97/02691 PCTrUS96/11202 available for data tr~n.cmi~cion". The control i..~l",dlion further colllaills i~ ion sllffi~ nt to notify the source nodes as to which destin~tiQn nodes are available over the link.
Speeifi~lly, the available destin~tion nodes are known by (i) storing the source/destin~tion address pair i.~malion at the router. In this case, the router sends an s individual packet to each source node listing the dçstin~tion nodes available over the link; (ii) routing i,~ll"aLion stored at the source nodes. Here, the router need only identify the particular link that is available; and (iii) configuring the router with a summary of de~ ;on addresses reachable over the link. The router may provide this latter information to the source nodes via a mllltic~t message.
o In response to the message, any source node wishing to transmit information over the link 330 may then send a data packet to the router 312. An advantage of this embodiment is that the router 312 need not retain the source and destin~tion addresses of every data packet dçstined for an inactive on-demand link; another advantage is that source nodes need not initiate data tr~n~mi~ion over the link until they receive the multicast message.
While there has been shown and described an illustrative embodiment for synch~ i"g particular types of data packets, e.g., periodically Ll~ "lil~ed data packets that are not time critical, with an on-demand link of a computer network in a manner that efficiently utilizes that link, it is to be understood that various other adaptations and modifications may be made within the spirit and scope of the invention. For example, source nodes may be configured to periodically poll a router to test whether the on-demand link is actively connected This technique is less optimal than that of the illustrative embodiments because of an increase in network bandwidth n~cec~itated by the polling traffic; however, it may be useful as a backup mf~c.ll~ni.~". in the event the router "crashes" and loses the information needed to identify the sending processes within the source nodes.
2s In addition, the control i.~r~ ,laLion specifying whether an on-demand link should be activated may be provided to a router by way of data packet locations other than the network layer header. For example, the router may be configured to ex~mine beyond the network layer header, i.e., it may parse the packet to analyze higher-level protocol stack layer headers, to ~et~o~mine whether the packet instructs the router to activate the link.
W O 97/02691 PCT~US96/11202 The r~lego;ng description has been directed to specific embo~lim~nts of this invention.
It will be app~ C:IlL, however, that other variations and modifications may be made to the clesçrihed embodimPnt~ with the ~tt~inment of some or all of their advantages. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.
W O97/02691 PCTrUS96/11202 METEOD AND APPARATUS FOR SYNCEIRONIZING DATA TRANSMISSION
WIT~ ON-DEMAND LINKS OF A NETWORK
EIELD OF T~E INVENTION
This invention relates generally to conl~uLer neLwulhs and, more particularly, to efficient ~ltili7~tion of on~ om~nd communication links of a computer network.
BACKGROUND OF T~E INVENTION
A computer network is a geographically distributed collection of hlLel con,.ected c~ .. l.:~~ti~-n links for transporting data between nodes, such as computers. A plurality of c~ nt;~wulh~ may be further interconnected by intermedi~te nodes, or routers, to eYtend the ~ ;live "size" of the nG~wolk~, smaller groups of which may be m~int~ined as an autonomous system or domain of nodes. These nodes typically communicate by ~Yt~h~nging discrete "packets" of data according to predefined protocols. In this context, a protocol consists of a set of rules defininp how the nodes interact with each other.
The co~ ic~tion links forming the networks may be perm~nently installed to theiri,lLercol-l-ected nodes, as in the case of an Fth.ornet communications system, or they may be dial-up lines of a switched telephone network that remain ordinarily unconnected These dial-up lines are typically "brought-up", i.e., dialed, by the routers to initiate node-to-node c~ mml-nication on-demand; accordingly, these lines are also known as on-demand links. An f~Y~mple of a network that utilizes on-demand links is the Integrated Services Digital Network (ISDN).
In order to reduce design complexity, most nelwolk~ are organized as a series ofhaldw~; and sonw~le levels or "layers" within each node. These layers interact to format data for transfer between, e.g., a source node and a destination node communicating over the ~ ne~wulL. Specifically, predetermined services are performed on the data as it passes through each layer and the layers communicate with each other by means of the predefined protocols.
This layered design permits each layer to offer selected services to other layers using a CA 02226189 1998-01-0~
W O 97/026g1 PCT~US96/11202 dardi~ed int~ ce that shields those layers from the details of actual imrl~ l;on ofthe services.
In an attempt to standardize network architectllres, i.e., the sets of layers and protocols used within a I~GLWV1k~ a generalized model has been proposed by the International Standards s O,~;an~lion (ISO). The model, ealled the Open Systems Interconnection (OSV reference model, is direeted to the intereonneetion of systems that are "open" for eommllnie~tion with other systems. The proposed OSI model has seven layers whieh are termed, in ~ccçnding interf~f~.ing order, the physical, data link, net~ork, ~ransport, session, presentation, and ~plication layers. These layers are arranged to form a "protocol stack" in each node of the network.
Fig. 1 illustrates a s~hlom~tie bloek diagram of prior art protocol stacks 125 and 175 used to transmit data between a souree node 110 and a destination node 150, respectively, of a e~ mpllt~r network 100. Each protocol stack is structured aecording to the OSI seven-layer model; acco-di,-gly, each staek comprises a collection of protocols, one per layer. As can be seen, the protoeol stacks 125 and 175 are physieally connected through a commlmie~tions ehannel 180 at the physical layers 124 and 16~. For ease of description, the protoeol staek 125 will be deseribed.
Broadly stated, the physical layer 124 transmits a raw data bit stream over a eoll..-lu.lieation ehannel 180, while the data link layer 122 manipulates the bit stream and I.~n:irolll-s it into a datastream that appears free of tr~ncmiccion errors. This latter task is ~ecompli.ched by dividing the tr~ncmitted data into frames and tr~ncmittin~ the frames sequentially, aeeompanied with error eorrecting me~h~ni.cmc for detecting or correeting errors.
The network layer 120 routes data packets from the source node to the destination node by s~leeting one of many alternative paths through the physical network. The transport layer 118 aeeepts the datastream from the session layer 116, apportions it into smaller units (if necessary), passes the smaller units to the network layer 120 and provides appropriate mer.h~nicmc to ensure that all the units arrive correctly at the d~stin~tion.
The session layer 116 establishes data transfer "sessions" between software processes on the source and destin~tion nodes, along with management of such sessions in an orderly fashion.
CA 02226189 1998-01-0~
W O 97/0201 PCTrUS96/11202 That is, a session not only allows ol.linaly data transport between the nodes, but it also provides enh~nred services in some applications. The pres~;..lalion layer 114 performs frequently-requested functions relating to the presentation of transmitted data, incl~ ing encoding of data into ~ dald formats, while the application layer 11 2 contains a variety of protocols that are co~ lonly needed by processes e~ecuting on the nodes.
Data tran.cmi.~.~ion over the network 100 therefore consists of generating data in, e.g., a sending process 104 Px~c~ltin~ on the source node 110, passing that data to the application layer 112 and down through the layers ofthe protocol stack 125, where the data are sequentially follll~LLed as a packet for delivery onto the channel 180 as bits. Those packet bits are then Ll~ ed to the protocol stack 175 ofthe destin~tion node 150, where they are passed up that stack to a receiving process 174. Data flow is s~.henn~tically illustrated by solid arrows.
Although actual data tr~n~mi~cion occurs vertically through the stacks, each layer is prograrnmed as though such tr~n~mi.~ion were horizontal. That is, each layer in the source node 100 is programmed to transmit data to its corresponding layer in the destination node 150, as srhrm~tic~lly shown by dotted arrows. To achieve this effect, each layer of the protocol stack 125 in the source node 110 typically adds information (in the form of a header field) to the data packet generated by the sending process as the packet descends the stack. At the destin~tion node 150, the various headers are s*ipped offone-by-one as the packet propagates up the layers of stack 175 until it arrives at the receiving process.
As noted, a significant function of each layer in the OSI model is to provide services to the other layers. Two types of services offered by the layers are "connection-oriented" and ''connectiQnlee.C~ network services. In a connection-oriented service, the source node establishes a connection with a destin~tion node and, after sending a packet, terminates the cQ~ e~il;Qn The overhead ~cori~ted with establishing the connection may be unattractive for nodes requiring efficient communication performance. For this case, a fully connectionless service is desirable where each tr~n.cmitted packet carries the full address of its destin~tion through the network.
Network layer protocols are generally used to implement a connectionless networkservice, the latter of which primarily defines a packet format. When the network layer receives CA 02226l89 l998-Ol-0~
WO 97/02691 PCTrUS96/11202 a packet from the transport layer for tr~ncmiccion over the network, it adds (to the paeket) a header ec,. ~ E, inter alia, souree and dçctin~tion addresses. ~xamples of n~lwol k layer protoeols are the eonnectionless network layer protoeol (CLNP) defined by ISO, the Internet (IP) IwLwolk layer protoeol and the Internet Packet Fxeh~nEe (IPX) protoeol.
The overall packet formats of the CLNP and IP headers may be .oxt~n~led to ~ee~ mmodate added re~Lu- c;s by way of option fields contained within the headers defined by the network layer services. The types of options supported by these fields typieally include souree routing, priority and security-specific inrollnalion. However, the conv~ntion~1 IPX
header format is generally not exr~nd~hle since its header was not designed to aecomodate appended fields in a manner that is eomp~tihle with the rçm~ining fields of the paeket.
As also noted, a router is used to bring-up an on-demand link of a network typieally in response to the reeeption of a data packet int~nrled to be forwarded over the link. However eaeh time the link is dialed, eonnection charges are incurred. Certain types of data packets are ~Yçh~nEed in accordance with non-time critieal applications, such as synchronizing distributed lS ~t~h~Ces with respeet to direetory serviees. This type of computer-to-computer traffic is flexible as to when packet tr~ncmiccion oceurs and the present invention is direeted to ~y~lcll~ul~i~in~ delivery of sueh traffc until times when the on-demand link is dialed for other eompelling reasons.
SUMMARY OF T~E INVENTION
The invention comprises a ~.. eç1~ icm for synchronizing delivery of types of data packets over on-demand links of a computer network in a manner that efficiently utilizes those links. The novel synchronization mer.h~nicm comprises control information generated by a souree node and generally stored in a network layer header of a data packet tr~ncmitted to a d~ctin~tion node via at least one router coupled to an on-demand link of the network.
2s Depending upon the state of the eontrol information, the router is instrueted whether to imme~ tloly dial the link to establish a eonneetion for delivery of the paeket to the dçstin~tion node.
CA 02226l89 l998-Ol-0~
W O 97/02691 PCTrUS96/11202 Plt;r~ably, the control i~ ion is incol~ol~led within the network layer header as an option. In the case of network layer headers that support option fields, such as the clml-~ Sr nt;lw~lh layer protocol (CLNP) and the Internet (IP) network layer protocol headers, a new option type is defined for on-demand links. The Internet Packet Fx~h~l~g~
(rPX) protocol header, however, does not accomodate option fields and, thus, a nGlw~
addressing ~l~i-g~ is provided that e~p~nd~e the forrnat of this header to support the novel control il~llllaLion, e.g., a flag, as an option.
In the illustrative embodiment of the invention, if the novel flag is asserted, the router is instructed "not to dial the on-demand link". When the router receives a data packet with an o asserted flag, it stores certain information contained in the packet that is sufflcient to identify the sending process within a source node and discards the r~m~in-1çr ofthe packet prior to sending a return packet to the source. The return packet preferably in~.hldes complete source and d~etin~tion addresses of the data packet, i.e., inforrnation sufficient to identify a process within the source node sending that packet, along with a reason for returning that packet (e.g., "on-demand link not currently dialed"). Furthermore, the router keeps track of these source and d~etin~ti~)n addresses so that when it eventually brings-up the link, it can send a subsequent notification packet to the source indicating that the on-demand link is currently available for tr~n.emieeinn ofthe data packet to the dçstin~tinn.
Synchrol~alion of particular types of data packets, e.g., periodically ll ;1. .e. . .;1 l ed data packets that are not time critical, with an on-demand link may be further realized by requiring the source node to periodically poll the router to test whether the link is connecte~1 This terhni1ue is less optimal than that of the illustrative embodiment because of an increase in network bandwidth neceseit~ted by the polling traffic; however, it may be useful as a backup me~h~niem in the event the router "crashes" and loses the information needed to identify the sending process within the source node.
In an alternate embodiment, the router may store the data packet with the asserted flag and, when the on-demand link is subsequently dialed, send the packet to the dçstin~tion node.
For this embodiment, the router is not required to notify the source node that the link was previously unavailable and that the data packet was temporarily stored at the router. Although CA 02226189 1998-01-0~
WO 97/02691 P~liU~'.S/11202 this approach reduces traffic between the router and source node, it may result in "stale" data being l~l-e- ~;1 led to the destin~tion node if the latency incurred waiting for the link to be c~)nn~cted is subst~ntis~l In yet another embodiment ofthe invention, the router may l~ ----l a mllltic~ct m~e.e~e s to all nodes of the network when the on-demand link is up. Here, the mlllti~.~et m~ec~e cc~ ins the novel control i.~..--~lion which alerts sending processes of recipient source nodes that "the on-demand link is ~;ullGIllly available for data tr~n~miC~ion" The control i- ro-ll.~lion further contains h~l.--alion sufficient to notify the source nodes as to which d.~stin~tiQn nodes are available over the link.
In response to the multicast mee~g~, any source node wishing to l-~ .. il h rc,llllalion over that link may then send a data packet to the router. One advantage of this embodiment is that the router need not retain the source and destin~tion addresses of every data packet ed for an inactive on-demand link; another advantage is that source nodes need not initiate data l,~ ----e~i;on over the link until they receive the multicast message.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like nces indicate similar elements, and in which:
Fig. 1 is a schematic block diagram of prior art protocol stacks used to transmit data between a source node and a destin~tion node of a computer network;
Fig. 2 is a block diagram of a network system including a collection of computer1IG~WUIk~ connected to a plurality of nodes;
Fig. 3 is s~h~m~tic block diagram of a system having a plurality of domains interconnected by an on-demand link in which a novel synchronization merh~ni~m ofthe present 2s invention may be advantageously used;
Figs. 4A - 4C are sch~m~tic diagrams of option fields of conventional network layer headers for storing the novel synchlolliGalion me~h~niem in accordance with the invention;
CA 02226189 1998-01-0~
W O 97/02691 rCTAUS96111202 Fig. S is a srh~m~tic diagram depicting the forrnat of a conventional IPX nc;Lw~lk layer header; and Fig. 6 is a schf~m~tic diagram illustrating an improved format of the IPX network layer header for storing the novel syncl~ol~i~lion m~rh~ni~m according to the invention.
s DETAll ,F.n DESCRrPTION OF ILLUSTRATIVE EMBODIMENT
Fig. 2is a block diagram of a network system 200 comprising a collection of co~ uLer ~elw~lk~ connected to a plurality of nodes. The nodes are typically general-purpose computers comprising a source node S, an end node N, a destin~tion node D and a plurality of interm~ te nodes R1-R2. Each node typically comprises a central processing unit (CPU) 202, a memory unit 204 and at least one network adapter 206 interconnected by a system bus 210. The memory unit 204 may comprise storage locations typically composed of random access memory (RAM) devices, which are addressable by the CPU 202 and network adapter 206. The memory unit typically provides temporary storage of information, such as executable processes and collLenLs of data packets, as described further herein. An operating system, portions of which are typically resident in memory and executed by CPU, functionally organizes the node by, inter alia, invoking network operations in support of those processes executing in the CPU.
The computer networks inclnded within system 200 may range from local area networks (LANs) to wide area networks (WANs). A LAN is a limited area network, while a WAN may be a public or private teleco.. ~ tions facility that interconnects nodes widely dispersed using comml~nir~tion links. Communication among the nodes coupled to these networks is typically effected by exrh~nging discrete data"packets" specifying addresses of, e.g., source and destin~tion nodes. Since the system shown in Fig. 2 comprises a relatively small group of inte,comlected LANs 1-3, it is preferably m~int~ined as an autonomous domain. The intermediate nodes are preferably routers configured to facilitate the flow of data packets s throughout the domain 200 by routing those packets to the proper receiving nodes.
In general, when a source node S transmits a packet over LAN 1, the packet is sent to all nodes on that LAN. If the int~nded recipient of the packet is connected to LAN 3, the packet is routed through router R1, over LAN 2 and through R2 onto LAN 3. A key function CA 02226l89 l998-Ol-0~
WO97/02691 P~l/~',''11202 of a router is d~ the next node to which the packet is sent; this routing filnrtion is pl erel ~ y ~)e~ r ~ ed by n elwolk layer 260 of a protocol stack 250 within each node. Typically, the packet co..l~ two destin~tion addresses: the address ofthe final dçstin~ti~ n node and the address ofthe next node along the route. The final destin~tion address remains constant as the s packet ll~vel~es the l~elwolk~ while the next destin~tion address rh~ngeS as the packet moves from node to node along the route through the networks.
Sperifiç~lly~ when source node S sends a packet to dçstin~tion node D, i.e., the final ~lestin~tion address, the packet is L~ e(l onto LAN 1 with a next destin~fion address specifying the address of router R1. Address h~l ",~lion embedded in the packet, which is processed by the higher-layer software of the protocol stack 250, identifies the final riestin~tion of the packet as node D. Based on this information, R1 determines that the next node along the route is router R2 and proceeds to pass the packet onto LAN 2 for reception by that node.
Router R2 then determines that the next node is the final destination node D and transmits the packet over LAN 3 to node D.
Fig. 3 is a sch.?m~tic block diagram of a system 300 comprising a plurality of ~lom~inc 310 and 320 interconnected by a communication link 330 coupled to routers 312 and 322. The c~ ~-----.-~l;r~tion link 330 is plerel~bly a temporary link that may be "brought-up", i.e., dialed, by the routers to initiate node-to-node col"l,lu"ication on-demand; that is, on-demand link 330 may be embodied as a dial-up link of a switched telephone network that remains ordinarily unconnected In the illustrative embodiment, the on-demand link may comprise an Integrated Services Digital Network (ISDN) line, while the domains interconnected by the link may include in-~eprnflPnt Tntrrn~ot Packet F.xc~.h~n~e (IPX) networks, such as the Novell Corporate IPX
network and the Microsoft Corporate IPX network.
Typically, the router 312 dials the on-demand link 330 in response to the reception of a 2s data packet from source node S that is destined for destin~tion node D. Each time the link is dialed, though, connection charges similar to those of any switched telephone line are incurred.
Yet, certain types of data packets are L~ ed in accordance with non-time critical applications, such as electronic mail or synchronizing distributed ~l~t~hacçc associated with directory services. This type of computer-to-computer traffic is generally flexible as to when CA 02226l89 l998-Ol-0~
W O 97/02691 PCTrUS96/11202 data ~ ion occurs and, as noted, the present invention is directed to syncl~ol~,.g delivery of such traffic until times when the on-demand link is otherwise dialed.
For routers 312 and 322 to be used in system 300, the interconnected n~:Lw~),h~ must share the same network layer protocols and must be compatible at the higher protocol stack s layers. The ne~wo,k~ may, however, differ at the data link layer 362 and the physical layer 364, as shown s~ ic~lly in the protocol stack 3so of router 3 l 2. Although the routers may operate with any network layer protocol, in the illustrative embodiment described herein, the n~lw~lk layer protocols are preferably the connectionless network layer protocol (CLNP), the Tnt~rnet (IP) network layer protocol and the IPX protocol.
o As further noted, when the network layer 360 receives a data packet from the transport layer 358 for tr~n~mi~ion over the network, it adds a network layer header to the packet. The formats of these header fields are generally the same among all network layer services primarily because the same information are typically contained in each packet. Figs. 4A and 4B depict the formats of IP and CLNP network layer packets 410 and 450, respectively. It can be seen that both ofthese packets generally contain information pertaining to their headers 412 and 452 (e.g., length and ~hec~cllm fields); more particularly, though, each header inr.l~ldes an options field 426 and 466 to accommodate added features. The types of options supported by these fields typically include source routing, priority and security-specific information. Fig. 4C
depicts the general format of the contents of an options field 480 which comprises an octet (1-2c byte) option code field 482 that uniquely defines a type of option, a l-byte length field 484 in~lic~ting the length of the option in bytes, and a variable, e.g., 0-254 byte, value field 486.
However, the IPX protocol header does not accomodate option fields and, thus, the invention provides a network addressing arrangement that expands the format of this header.
Fig. 5 is a s~.h.om~tic diagram depicting the format of a conventional IPX packet 500 having a network layer header comprising ~ppl-~xill.ately 30 bytes. Specifically, the header contains, inter alia, hierarchical d~stin~tion and source addresses, each of which includes a plurality of address elements. For example, the destination address 510 comprises a 4-byte destin~tion nc:~wc,lh field 512 that indicates the particular network over which the packet will travel, a 6-byte d.o~tin~tion node field 514 identifying a data link layer address of the receiving node on that CA 02226189 1998-01-0~
WO 97/02691 PCT~US96/11202 nt;~w~lh and a 2-byte destin~tinn socket field 516 specifying the receiving process in the r~ceivillg node. Data field 530 is appended to the header, immP~ tely following the source address field 520.
Accol~ g to the addressing arrangement, a special socket value is provided that inr1ic~tçs the provision of additional header h~ro~ Lion after the source address field to e~t;~iLiv~ly create an i"~prov~d network layer header. Fig. 6 is a ~ch~m~tic diagram illustrating the format of the improved IPX network layer header 600. A source node substitutes the special socket value 656 for the actual destin~tion socket number within the 2-byte destin~tinn socket field 516 ofthe conventional dçstin~fion address field 510. Preferably, the special socket value instructs the routers to PY~mine the contents of e~p~n~1ed header fields 660 prior to rOl w~udulg packets over the networks.
In accordance with the invention, a mech~ni~m is provided for synchlolliGing delivery of particular types of data packets over on-demand links of a computer network in a manner that f~ffi~i,ontly utilizes those links. Referring now to Figs. 1-6, the novel synch~ fi~aLion mer.h~ni~m cc,l-",.ises control i,~"-l~lion generated by a source node, e.g., source node S, and stored in the network layer header of a data packet tr~n~mitted to a destin~tion node, e.g., destin~tion node D, via a router 312 coupled to on-demand link 330 of network system 300. Depending upon the state of the control information, the router is instructed whether to immer~i~tçly dial the link to establish a connection for delivery of the packet to the destination node D.
Preferably, the control information is incorporated within the network layer header as an option. In the case of the IP and CLNP network layer protocols whose headers contain option fields, a new option type is defined for on-demand links. Specifically, the new option type comprises an option code, e.g., "ODL", stored in field 482 that uniquely specifies an on-demand link, along with information stored in value field 486 instructing the router whether to dial the 2s on-demand link in response to reception of the packet. The total length of the option field 480 in bytes is indicated in the length field 484.
With respect to the improved IPX header 600, on the other hand, the control information is stored in a field 670 of the expanded header fields 660. Although the contents of the field comprising the control information may vary, preferably the field is provided as a novel CA 02226189 1998-01-0~
WO 97102691 PCT~US96/11202 flag 670 and the state of this flag instructs the router how to handle the on-demand link 330. In other words, when the router 312 receives a data packet having the special socket value, e.g., "SS", ~ubsLiLuLed for the actual destin~tion socket number of the destination address, the router s the contents of ~Yp~nrled header fields and, in particular, the state of the flag 670 prior to rO. v~alding the packet over the link 330.
In the illustrative embodiment of the invention, assertion of the flag preferably instructs the router "not to dial the on-demand link". If the flag is asserted, the router stores certain a~ion cnnt~ined in the packet and discards the remaining contents of the packet prior to sending a return packet to the source. The return packet preferably includes complete source o and destin~tion addresses ofthe data packet, i.e., information sufficient to identify a process within the source node sending that packet, along with a reason for returning that packet (e.g., "on-demand link not currently dialed"). Additionally, the router 312 temporarily stores the source and dçstin~tion addresses of the header in its memory 204 so that when it eventually brings-up the link 330, it can send a subsequent notification packet to the source node S
in~lic~ting that the on-demand link 330 is currently available for tr~n~mi~ion ofthe data packet to the destin~tion node.
In an alternate embodiment of the invention, the router 312 may store the entire data packet with the asserted flag 670 in its memory 204 (Fig. 2) and, when the on-d.-m~n~l link 330 is subsequently dialed, send the packet to the destin~tion node D in domain 320. For this embodiment, the router 312 is not required to notify the source node S that the link 330 was previously unavailable and that the data packet was temporarily stored at the router 312.
Although this approach reduces traffic between the router and source node, it may result in "stale" data being tr~n~mitted to the destination node D if the latency incurred waiting for the link to be connected is substantial.
2s In yet another embodiment of the invention, the router 312 may transmit a single multicast message to all nodes ofthe network when the on-demand link 330 is dialed and available. Here, the multicast message contains the novel control information which, when asserted, alerts sending processes of recipient nodes that "the on-demand link is currently CA 02226189 1998-01-0~
WO 97/02691 PCTrUS96/11202 available for data tr~n.cmi~cion". The control i..~l",dlion further colllaills i~ ion sllffi~ nt to notify the source nodes as to which destin~tiQn nodes are available over the link.
Speeifi~lly, the available destin~tion nodes are known by (i) storing the source/destin~tion address pair i.~malion at the router. In this case, the router sends an s individual packet to each source node listing the dçstin~tion nodes available over the link; (ii) routing i,~ll"aLion stored at the source nodes. Here, the router need only identify the particular link that is available; and (iii) configuring the router with a summary of de~ ;on addresses reachable over the link. The router may provide this latter information to the source nodes via a mllltic~t message.
o In response to the message, any source node wishing to transmit information over the link 330 may then send a data packet to the router 312. An advantage of this embodiment is that the router 312 need not retain the source and destin~tion addresses of every data packet dçstined for an inactive on-demand link; another advantage is that source nodes need not initiate data tr~n~mi~ion over the link until they receive the multicast message.
While there has been shown and described an illustrative embodiment for synch~ i"g particular types of data packets, e.g., periodically Ll~ "lil~ed data packets that are not time critical, with an on-demand link of a computer network in a manner that efficiently utilizes that link, it is to be understood that various other adaptations and modifications may be made within the spirit and scope of the invention. For example, source nodes may be configured to periodically poll a router to test whether the on-demand link is actively connected This technique is less optimal than that of the illustrative embodiments because of an increase in network bandwidth n~cec~itated by the polling traffic; however, it may be useful as a backup mf~c.ll~ni.~". in the event the router "crashes" and loses the information needed to identify the sending processes within the source nodes.
2s In addition, the control i.~r~ ,laLion specifying whether an on-demand link should be activated may be provided to a router by way of data packet locations other than the network layer header. For example, the router may be configured to ex~mine beyond the network layer header, i.e., it may parse the packet to analyze higher-level protocol stack layer headers, to ~et~o~mine whether the packet instructs the router to activate the link.
W O 97/02691 PCT~US96/11202 The r~lego;ng description has been directed to specific embo~lim~nts of this invention.
It will be app~ C:IlL, however, that other variations and modifications may be made to the clesçrihed embodimPnt~ with the ~tt~inment of some or all of their advantages. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.
Claims (19)
1. Apparatus for synchronizing delivery of a data packet generated by a source node and transmitted over an on-demand link of a computer network to a destination node in a manner that efficiently utilizes that link, the apparatus comprising:
a router coupled to the on-demand link the router configured to activate the link to establish a connection to another node of the network for delivery of the packet to the destination node; and means for instructing the router whether to immediately activate the link to establish the connection, the instructing means comprising control information stored in the data packet.
a router coupled to the on-demand link the router configured to activate the link to establish a connection to another node of the network for delivery of the packet to the destination node; and means for instructing the router whether to immediately activate the link to establish the connection, the instructing means comprising control information stored in the data packet.
2. The apparatus of Claim 1 wherein the control information is generated by the source node.
3. The apparatus of Claim 1 wherein the control information is stored in a network layer header of the data packet.
4. The apparatus of Claim 3 wherein the control information comprises an option within the network layer header.
5. The apparatus of Claim 4 wherein the option is a new type of option defined for the on-demand link and contained within an option field of the header.
6. The apparatus of Claim 4 wherein the option is a flag stored within an expanded header field of the header.
7. The apparatus of Claim 1 wherein the control information is contained within higher-layer protocol stack headers of the data packet other than a network layer header.
8. A method for synchronizing delivery of a data packet generated by a sending process within a source node of a computer network and transmitted over an on-demand link of the network to a destination node in a manner that efficiently utilizes that link, the method comprising the steps of:
generating control information within the data packet at the sending process of the source node;
forwarding the data packet to a router coupled to the on-demand link;
examining the control information at the router, the control information instructing the router to abstain from immediately activating the link to establish a connection to another node of the network; and storing information contained within the packet at the router, the stored information being sufficient to identify the sending process within the source node.
generating control information within the data packet at the sending process of the source node;
forwarding the data packet to a router coupled to the on-demand link;
examining the control information at the router, the control information instructing the router to abstain from immediately activating the link to establish a connection to another node of the network; and storing information contained within the packet at the router, the stored information being sufficient to identify the sending process within the source node.
9. The method of Claim 8 further comprising the step of sending a notification packet to the sending process when the on-demand link is activated, the notification packet informing the sending process that the link is currently available for delivery of the data packet to the destination node.
10. The method of Claim 8 further comprising, immediately after the step of storing, the step of sending a return packet to the source node, the return packet identifying the sending process of the source node and informing that process that the on-demand link is not currently dialed.
11. The method of Claim 8 further comprising the step of sending a return packet to the source node, the return packet identifying the sending process of the source node and informing that process that the on-demand link is not currently activated.
12. The method of Claim 11 further comprising, at the source node, the step of periodically polling the router to test whether the link is activated.
13. The method of Claim 8 further comprising the step of storing the control information in a network layer header of the data packet.
14. A method for synchronizing delivery of a data packet generated by a source node and transmitted over an on-demand link of a computer network to a destination node in a manner that efficiently utilizes that link, the method comprising the steps of:
generating control information within the data packet at the source node;
forwarding the packet to a router coupled to the on-demand link;
examining the control information at the router, the control information instructing the router to abstain from immediately activating the link to establish a connection to another node of the network;
storing the data packet at the router; and sending the data packet over the on-demand link to the destination node when the link is subsequently activated.
generating control information within the data packet at the source node;
forwarding the packet to a router coupled to the on-demand link;
examining the control information at the router, the control information instructing the router to abstain from immediately activating the link to establish a connection to another node of the network;
storing the data packet at the router; and sending the data packet over the on-demand link to the destination node when the link is subsequently activated.
15. A method for synchronizing delivery of a data packet generated by a source node and transmitted over an on-demand link of a computer network to a destination node in a manner that efficiently utilizes that link, the method comprising the steps of:
generating control information within a multicast data packet at a router coupled to the on-demand link;
distributing the multicast packet to nodes of the network, including the source node;
examining the control information at the source node, the control information informing the source node that the on-demand link is currently available for establishing a connection to the destination node; and sending a data packet from the source node to the router for transmission over the link to the destination node.
generating control information within a multicast data packet at a router coupled to the on-demand link;
distributing the multicast packet to nodes of the network, including the source node;
examining the control information at the source node, the control information informing the source node that the on-demand link is currently available for establishing a connection to the destination node; and sending a data packet from the source node to the router for transmission over the link to the destination node.
16. Apparatus for synchronizing delivery of a data packet generated by a source node and transmitted over an on-demand link of a computer network to a destination node in a manner that efficiently utilizes that link, the apparatus comprising:
a router coupled to the on-demand link, the router configured to activate the link to establish a connection to another node of the network for delivery of the packet to the destination node; and means for instructing the router whether to immediately activate the link to establish the connection the instructing means comprising control information generated by the source node and stored in a network layer header of the data packet.
a router coupled to the on-demand link, the router configured to activate the link to establish a connection to another node of the network for delivery of the packet to the destination node; and means for instructing the router whether to immediately activate the link to establish the connection the instructing means comprising control information generated by the source node and stored in a network layer header of the data packet.
17. The apparatus of Claim 16 wherein the control information comprises an option within the network layer header.
18. The apparatus of Claim 17 wherein the option is a new type of option defined for the on-demand link and contained within an option field of the header.
19. The apparatus of Claim 17 wherein the option is a flag stored within an expanded header field of the header.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/498,640 US5596574A (en) | 1995-07-06 | 1995-07-06 | Method and apparatus for synchronizing data transmission with on-demand links of a network |
| US08/498,640 | 1995-07-06 | ||
| PCT/US1996/011202 WO1997002691A1 (en) | 1995-07-06 | 1996-07-02 | Method and apparatus for synchronizing data transmission with on-demand links of a network |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2226189A1 CA2226189A1 (en) | 1997-01-23 |
| CA2226189C true CA2226189C (en) | 2001-09-11 |
Family
ID=23981910
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002226189A Expired - Lifetime CA2226189C (en) | 1995-07-06 | 1996-07-02 | Method and apparatus for synchronizing data transmission with on-demand links of a network |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5596574A (en) |
| EP (1) | EP0836781B1 (en) |
| JP (1) | JP3279319B2 (en) |
| AU (1) | AU6407396A (en) |
| CA (1) | CA2226189C (en) |
| DE (1) | DE69601374T2 (en) |
| WO (1) | WO1997002691A1 (en) |
Families Citing this family (51)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5781534A (en) * | 1995-10-31 | 1998-07-14 | Novell, Inc. | Method and apparatus for determining characteristics of a path |
| US5732213A (en) * | 1996-03-22 | 1998-03-24 | Ericsson Inc. | System and method of testing open systems interconnection (OSI) layers in telecommunication networks |
| US6101528A (en) * | 1996-03-27 | 2000-08-08 | Intel Corporation | Method and apparatus for discovering server applications by a client application in a network of computer systems |
| US6430596B1 (en) | 1996-03-27 | 2002-08-06 | Intel Corporation | Managing networked directory services with auto field population |
| US5802304A (en) * | 1996-04-18 | 1998-09-01 | Microsoft Corporation | Automatic dialer responsive to network programming interface access |
| US5944795A (en) * | 1996-07-12 | 1999-08-31 | At&T Corp. | Client-server architecture using internet and guaranteed quality of service networks for accessing distributed media sources |
| US5893116A (en) * | 1996-09-30 | 1999-04-06 | Novell, Inc. | Accessing network resources using network resource replicator and captured login script for use when the computer is disconnected from the network |
| US5943676A (en) | 1996-11-13 | 1999-08-24 | Puma Technology, Inc. | Synchronization of recurring records in incompatible databases |
| US6141664A (en) | 1996-11-13 | 2000-10-31 | Puma Technology, Inc. | Synchronization of databases with date range |
| US6330568B1 (en) | 1996-11-13 | 2001-12-11 | Pumatech, Inc. | Synchronization of databases |
| US6212529B1 (en) * | 1996-11-13 | 2001-04-03 | Puma Technology, Inc. | Synchronization of databases using filters |
| US7013315B1 (en) | 1996-11-13 | 2006-03-14 | Intellisync Corporation | Synchronization of databases with record sanitizing and intelligent comparison |
| US7302446B1 (en) | 1996-11-13 | 2007-11-27 | Intellisync Corporation | Synchronizing databases |
| US6405218B1 (en) | 1996-11-13 | 2002-06-11 | Pumatech, Inc. | Synchronizing databases |
| US5777544A (en) * | 1997-03-17 | 1998-07-07 | Intellon Corporation | Apparatus and method for controlling data communications having combination of wide and narrow band frequency protocols |
| US6105064A (en) * | 1997-05-30 | 2000-08-15 | Novell, Inc. | System for placing packets on network for transmission from sending endnode to receiving endnode at times which are determined by window size and metering interval |
| US6034988A (en) * | 1997-08-04 | 2000-03-07 | Intellon Corporation | Spread spectrum apparatus and method for network RF data communications having extended communication channels |
| US6212183B1 (en) * | 1997-08-22 | 2001-04-03 | Cisco Technology, Inc. | Multiple parallel packet routing lookup |
| US6014667A (en) * | 1997-10-01 | 2000-01-11 | Novell, Inc. | System and method for caching identification and location information in a computer network |
| US6018770A (en) * | 1997-10-13 | 2000-01-25 | Research In Motion Limited | System and method for managing packet-switched connections |
| US8621101B1 (en) | 2000-09-29 | 2013-12-31 | Alacritech, Inc. | Intelligent network storage interface device |
| US8782199B2 (en) * | 1997-10-14 | 2014-07-15 | A-Tech Llc | Parsing a packet header |
| US6434620B1 (en) * | 1998-08-27 | 2002-08-13 | Alacritech, Inc. | TCP/IP offload network interface device |
| US6697868B2 (en) * | 2000-02-28 | 2004-02-24 | Alacritech, Inc. | Protocol processing stack for use with intelligent network interface device |
| US8539112B2 (en) | 1997-10-14 | 2013-09-17 | Alacritech, Inc. | TCP/IP offload device |
| US6226680B1 (en) | 1997-10-14 | 2001-05-01 | Alacritech, Inc. | Intelligent network interface system method for protocol processing |
| US6757746B2 (en) * | 1997-10-14 | 2004-06-29 | Alacritech, Inc. | Obtaining a destination address so that a network interface device can write network data without headers directly into host memory |
| JP3476665B2 (en) * | 1997-11-13 | 2003-12-10 | 富士通株式会社 | Relay device test system, communication device, and communication method |
| US6304881B1 (en) * | 1998-03-03 | 2001-10-16 | Pumatech, Inc. | Remote data access and synchronization |
| US6925477B1 (en) | 1998-03-31 | 2005-08-02 | Intellisync Corporation | Transferring records between two databases |
| US6370121B1 (en) | 1998-06-29 | 2002-04-09 | Cisco Technology, Inc. | Method and system for shortcut trunking of LAN bridges |
| US7007003B1 (en) | 1998-12-04 | 2006-02-28 | Intellisync Corporation | Notification protocol for establishing synchronization mode for use in synchronizing databases |
| KR100309803B1 (en) * | 1998-12-26 | 2001-12-17 | 서평원 | Database Synchronization System and Method between Network Management System and Managed Equipment |
| US6539381B1 (en) | 1999-04-21 | 2003-03-25 | Novell, Inc. | System and method for synchronizing database information |
| US8019901B2 (en) | 2000-09-29 | 2011-09-13 | Alacritech, Inc. | Intelligent network storage interface system |
| NO313727B1 (en) * | 2000-10-19 | 2002-11-18 | Ericsson Telefon Ab L M | Packet-based communication process related to high availability solutions |
| US7543087B2 (en) * | 2002-04-22 | 2009-06-02 | Alacritech, Inc. | Freeing transmit memory on a network interface device prior to receiving an acknowledgement that transmit data has been received by a remote device |
| US6996070B2 (en) * | 2003-12-05 | 2006-02-07 | Alacritech, Inc. | TCP/IP offload device with reduced sequential processing |
| KR100584383B1 (en) * | 2004-01-20 | 2006-05-26 | 삼성전자주식회사 | OPTICAL LINE TERMINALOLT FOR MANAGING LINK STATUS OF OPTOCAL NETWORK UNITSONUs AND GIGABIT ETHERNET PASSIVE OPTICAL NETWORKGE-PON APPLING THE SAME |
| US8248939B1 (en) | 2004-10-08 | 2012-08-21 | Alacritech, Inc. | Transferring control of TCP connections between hierarchy of processing mechanisms |
| WO2006081454A2 (en) | 2005-01-26 | 2006-08-03 | Internet Broadcasting Corporation | Layered multicast and fair bandwidth allocation and packet prioritization |
| US20080263171A1 (en) * | 2007-04-19 | 2008-10-23 | Alacritech, Inc. | Peripheral device that DMAS the same data to different locations in a computer |
| US8539513B1 (en) | 2008-04-01 | 2013-09-17 | Alacritech, Inc. | Accelerating data transfer in a virtual computer system with tightly coupled TCP connections |
| US20090276820A1 (en) * | 2008-04-30 | 2009-11-05 | At&T Knowledge Ventures, L.P. | Dynamic synchronization of multiple media streams |
| US8549575B2 (en) | 2008-04-30 | 2013-10-01 | At&T Intellectual Property I, L.P. | Dynamic synchronization of media streams within a social network |
| US8341286B1 (en) | 2008-07-31 | 2012-12-25 | Alacritech, Inc. | TCP offload send optimization |
| US20100088748A1 (en) * | 2008-10-03 | 2010-04-08 | Yoel Gluck | Secure peer group network and method thereof by locking a mac address to an entity at physical layer |
| US20100088399A1 (en) * | 2008-10-03 | 2010-04-08 | Yoel Gluck | Enterprise security setup with prequalified and authenticated peer group enabled for secure DHCP and secure ARP/RARP |
| US9306793B1 (en) | 2008-10-22 | 2016-04-05 | Alacritech, Inc. | TCP offload device that batches session layer headers to reduce interrupts as well as CPU copies |
| US20110055571A1 (en) * | 2009-08-24 | 2011-03-03 | Yoel Gluck | Method and system for preventing lower-layer level attacks in a network |
| CN103081540A (en) * | 2010-12-28 | 2013-05-01 | 三洋电机株式会社 | Wireless device |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2673787B1 (en) * | 1991-03-08 | 1993-05-07 | Alcatel Business Systems | PACKET MODE CONCENTRATOR METHOD AND ARRANGEMENT FOR DATA TERMINALS SERVED BY AN ISDN NETWORK. |
| IT1250515B (en) * | 1991-10-07 | 1995-04-08 | Sixtel Spa | NETWORK FOR LOCAL AREA WITHOUT WIRES. |
| SE470299B (en) * | 1992-05-22 | 1994-01-10 | Ellemtel Utvecklings Ab | Queue system for selectors with "Fast-Circuit" characteristics |
| FR2711468B1 (en) * | 1993-10-19 | 1996-01-05 | Ouest Standard Telematique Sa | Interconnection device between two remote local networks, and corresponding interconnection method. |
| US5448566A (en) * | 1993-11-15 | 1995-09-05 | International Business Machines Corporation | Method and apparatus for facilitating communication in a multilayer communication architecture via a dynamic communication channel |
| US5491800A (en) * | 1993-12-20 | 1996-02-13 | Taligent, Inc. | Object-oriented remote procedure call networking system |
-
1995
- 1995-07-06 US US08/498,640 patent/US5596574A/en not_active Expired - Lifetime
-
1996
- 1996-07-02 EP EP96923601A patent/EP0836781B1/en not_active Expired - Lifetime
- 1996-07-02 AU AU64073/96A patent/AU6407396A/en not_active Abandoned
- 1996-07-02 CA CA002226189A patent/CA2226189C/en not_active Expired - Lifetime
- 1996-07-02 DE DE69601374T patent/DE69601374T2/en not_active Expired - Lifetime
- 1996-07-02 WO PCT/US1996/011202 patent/WO1997002691A1/en active IP Right Grant
- 1996-07-02 JP JP50528097A patent/JP3279319B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE69601374T2 (en) | 1999-05-27 |
| DE69601374D1 (en) | 1999-02-25 |
| EP0836781B1 (en) | 1999-01-13 |
| US5596574A (en) | 1997-01-21 |
| EP0836781A1 (en) | 1998-04-22 |
| CA2226189A1 (en) | 1997-01-23 |
| WO1997002691A1 (en) | 1997-01-23 |
| AU6407396A (en) | 1997-02-05 |
| JP3279319B2 (en) | 2002-04-30 |
| JPH10510414A (en) | 1998-10-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2226189C (en) | Method and apparatus for synchronizing data transmission with on-demand links of a network | |
| US5781534A (en) | Method and apparatus for determining characteristics of a path | |
| US6430196B1 (en) | Transmitting delay sensitive information over IP over frame relay | |
| US5805818A (en) | System for acknowledging availability of neighbor node using data packet containing data that is ordinarily fowarded to neighbor node | |
| CA2226204C (en) | Network addressing arrangement for backward compatible routing of an expanded address space | |
| US7486622B2 (en) | OAM echo messaging to verify a service-based network distribution path | |
| US7554959B1 (en) | Apparatus and method for cluster network device discovery | |
| EP1478129B1 (en) | Using network transport tunnels to provide service-based data transport | |
| US20030126188A1 (en) | Generic header parser providing support for data transport protocol independent packet voice solutions | |
| CN101305583A (en) | Session relay device and session relay method | |
| US6389453B1 (en) | Method and system for routing undirectional multicast data | |
| US6473430B2 (en) | Systems and methods for connecting frame relay devices via an ATM network using a frame relay proxy signaling agent | |
| US5917823A (en) | X.25 access to frame relay network | |
| US7009980B1 (en) | Apparatus and method for automatic port identity discovery in hierarchical heterogenous systems | |
| US20010052025A1 (en) | Router setting method and router setting apparatus | |
| US7107354B2 (en) | Multiplexer discovery and parameter exchange | |
| Carne | A professional's guide to data communication in a TCP/IP world | |
| JPH10117215A (en) | Inter-network connection method and its system | |
| US6865178B1 (en) | Method and system for establishing SNA connection through data link switching access services over networking broadband services | |
| Cisco | X.25 and LAPB Commands | |
| Cisco | Configuring Packet-Switched Software | |
| AU2003280481B9 (en) | System and method to provide node-to-node connectivity in a communications network | |
| JP3693953B2 (en) | Broadcast transmission method, apparatus, and program | |
| Meyer | Extensions to RIP to Support Demand Circuits | |
| JP3501558B2 (en) | ATM communication equipment |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20160704 |