|Publication number||US6873602 B1|
|Application number||US 09/620,119|
|Publication date||Mar 29, 2005|
|Filing date||Jul 20, 2000|
|Priority date||Aug 6, 1999|
|Publication number||09620119, 620119, US 6873602 B1, US 6873602B1, US-B1-6873602, US6873602 B1, US6873602B1|
|Original Assignee||Fujitsu Limited|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (13), Referenced by (76), Classifications (15), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a network system, a switch, and a server. More particularly, the present invention relates to a network system comprising a plurality of terminals, a plurality of switches which interconnects those terminals and select correct packet destinations, and a server for controlling those switches. The present invention further relates to a switch and server for use in the above network system.
2. Description of the Related Art
In the context of effective use of limited bandwidth resources in a local area network (LAN), confining the broadcast domain, i.e., the area within which broadcast frames can reach, is one of the promising approaches. Virtual LAN (abbreviated as “VLAN” where appropriate) is known as an enabling technology for this, which allows logical grouping of user terminal stations regardless of their physical locations and connections.
The above conventional network system operates as follows. Suppose here that the terminal T1 is attempting to send a broadcast frame FR.
Returning to the context of
There is a standardized format of the tag field (IEEE 802.1Q) for the purpose of VLAN implementations, and switches conforming to the standard specifications are increasingly common in the market today. As opposed to this increasing prevalence of standardized switch products, few terminal stations (including network interface cards for them) support the standard specifications for VLAN. To construct VLANs, it is therefore necessary to define VLAN membership for each port of each switch. This is, however, a troublesome task particularly in such a network where the terminals are administrated under an IP address based management policy. That is, the network administrator has to manually change the VLAN membership definitions of a relevant switch, every time a terminal station is moved, added, or removed.
Taking the above into consideration, an object of the present invention is to provide a network system which eliminates the need for changing VLAN definitions even if a member terminal is relocated, added, or removed.
To accomplish the above object, according to the present invention, there is provided a network system comprising a plurality of terminals, a plurality of switches, and a server. Each terminal belongs to one of a plurality of logical groups, or VLANs. The switches interconnect the terminals, receiving and forwarding the packets originating therefrom. Each switch comprises: a first storage unit which stores information that is used to identify logical group membership of the source terminal of a received packet; a query unit which sends a query to the server to request information about the logical group membership, when the first storage unit has failed to provide sufficient information to identify the logical group membership of a particular source terminal; and an updating unit which updates the information stored in the first storage unit according to a response to the query. To control the switches, the server comprises: a second storage unit which stores a list of identifiers of the terminals, in association with the logical groups to which the terminals belong; a searching unit which searches the second storage unit in response to the query from the requesting switch; and a transmission unit which sends the search result to the requesting switch.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.
FIGS. 11(A), 11(B), and 11(C) are diagrams which show a few examples of frames exchanged between a switch and a server shown in
FIG. 11(A) shows the general structure of frames for query, response, and notification;
FIG. 11(B) shows the detailed structure of frames for query and response:
FIG. 11(C) shows the detailed structure of frames for notification;
FIGS. 18(A), 18(B), and 18(C) are diagrams showing data message structures based on the SNMP frame format which is used in data exchange between a switch and a server;
FIG. 18(A) shows the entire structure of an SNMP frame;
FIG. 18(B) shows the detailed data structure of PDU field shown in FIG. 18(A);
FIG. 18(C) shows the detailed data structure of VarBindList field shown in FIG. 18(B);
FIGS. 19(A) and 19(B) are diagrams showing data message structures based on the COPS frame format which is used in data exchange between a switch and a server;
FIG. 19(A) shows the entire structure of a COPS frame;
FIG. 19(B) shows the detailed data structure of PDU field shown in FIG. 19(A);
A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.
The following section will describe the structure of the switch 2-1; the same can be applied to the other two switches 2-2 and 2-3. The switch 2-1 comprises a first storage unit 2 a, a query unit 2 b, and an updating unit 2 c. The first storage unit 2 a stores information to be used in identifying a specific logical group (i.e., virtual LAN) to which the source terminal of a received packet belongs. Virtual LAN (VLAN) refers to what is called a “subnet” in the TCP/IP network terminology. More strictly speaking, the term “VLAN” refers to a broadcast domain within which MAC-layer broadcast frames (i.e., frames directed to all terminals in a network) are confined. The query unit 2 b sends a query message to the server 3 when the logical group of the source terminal cannot be identified in spite of a search on the first storage unit 2 a. The updating unit 2 c updates information in the first storage unit 2 a according to the result of a query issued by the query unit 2 b.
The server 3 comprises a second storage unit 3 a, a searching unit 3 b, and a transmitter 3 c. When a query message is received from either of the switches 2-1 to 2-3, the server 3 performs a search on the second storage unit 3 a and returns a relevant record to the requesting switch. More specifically, the second storage unit 3 a stores a list of identifiers of the terminals, in association with the logical groups to which the terminals belong. The searching unit 3 b searches the second storage unit 3 a in response to a query from a switch. The transmitter 3 c sends the search result back to the requesting switch.
According to the present invention, the proposed network system operates as follows. Suppose here that the terminal 1-5 is removed from the switch 2-2 and relocated to the local terminal group of the switch 2-1, as illustrated in
Inside the switch 2-1, the updating unit 2 c updates the data stored in the first storage unit 2 a according to the search result sent from the server 3. Having sufficient information about the relocated terminal 1-5, the switch 2-1 now begins forwarding of frames transmitted from the terminal 1-5. Each such frame is added an appropriate tag field that indicates a particular VLAN where the terminal 1-5 belongs. Since the above notification is forwarded to the remaining switches 2-2 and 2-3, frames originating from other terminals within the same VLAN can also be delivered correctly to the terminal 1-5.
In some cases, it may not be necessary to redistribute the relocation notification over the network, because other switches can learn the facts about the relocation of the terminal 1-5 when they actually receive and process a frame originating from the terminal 1-5. This frame also provides information implying that the switch 2-1 is serving the terminal 1-5 at present. This implicit relocation notification, however, is disadvantageous for the following reason. Suppose, for example, that a certain terminal has sent a frame to the terminal 1-5 just after the relocation. Until they learn that the terminal 1-5 has moved to the switch 2-1's local terminal group, the switches would route the frame toward the old location (i.e., switch 2-2), thus failing to deliver it to the correct destination. To avoid this problem, it is desirable to send the notification to the switches in an explicit fashion.
As can be seen from the above discussion, the proposed network system is arranged to update VLAN configurations automatically when a terminal is relocated, through a query and response process between a switch and a server. This automatic reconfiguration function will alleviate the workload imposed on the network administrators.
A more specific embodiment of the present invention will now be described below.
The terminals 10-1 to 10-7 are end stations based on a personal computer or other platform, which send and receive data packets to/from each other, including documents, engineering drawings, and any other data objects created by users. The switches 11-1 to 11-4, coupled to those terminals 10-1 to 10-7, receive frames from their local terminals, and retransmit them toward their respective destinations through appropriate ports, after adding a tag that indicates a particular VLAN where each source terminal belongs. The switches 11-1 to 11-4 send such a tagged frame to the next leg of a route, thereby relaying the frame toward its destinations. When the next leg is the last link to the destination, they remove the tag from the frame and send it out through a relevant port.
Now the switches 11-1 to 11-4 are referred to collectively as the switches 11, whose details are depicted in FIG. 4. The switch 11 comprises a relaying processor 11 a, a controller 11 b, and a memory 11 c. The primary role of the switch 11 is to relay transmission frames through its ports P0 to P3. To this end, the relaying processor 11 a accepts and redirects the frames to their relevant ports, under the control of the controller 11 b. The controller 11 b performs various processing tasks according to programs and data stored in the memory 11 c, as well as governing other parts of the switch 11. The memory 11 c is composed of semiconductor memory devices or other storage components, being arranged to store software programs for the controller 11 b, as well as other data such as a VLAN configuration table described in the next paragraph.
“VID” field in the right-most column shows the identifiers of VLANs being supported by each port. Every tagged frame carries a virtual LAN identifier (VID) as described earlier in
In addition to the VLAN configuration table described above, the memory 11 c stores the following information, which should be defined and saved in a system initialization procedure.
Referring back to
The CPU 12 a performs various operations according to programs stored in the RAM 12 c, besides controlling other parts of the server 12. The ROM 12 b stores basic programs and data that the CPU 12 a executes and manipulates. The RAM 12 c serves as temporary storage for application programs and scratchpad data that the CPU 12 a executes and manipulates at runtime. The HDD unit 12 d stores various application programs to be executed by the CPU 12 a. Also stored in the HDD unit 12 d are: a switch data table, a terminal data table, and a VID data table, which will be subsequently described.
Besides storing the above three tables, the HDD unit 12 d maintains the following information, which should be defined and saved in a system initialization procedure.
Referring back to
According to the above embodiment of the invention, the network system operates as follows. Referring to
FIGS. 11(A), 11(B), and 11(C) present the frame formats used in a query and response session between the switch 11-4 and server 12. First, FIG. 11(A) shows the structure of frames for query, response, or notification, which is composed of the following fields.
FIG. 11(B) shows a query/response frame, which is composed of the following fields.
Referring back to
Now that the terminal in question has been identified, the server 12 looks up the switch data table (
Besides responding to the switch 11-4, the server 12 sends a notification frame to inform the switch 11-2 that the terminal 10-1 has left its local terminal group. The notification frame is structured into a plurality of data fields, as shown in FIG. 11(C). In the present example, they are:
Further, the server 12 issues another notification frame to inform the switch 11-1 that a terminal with a VID of “4” has been added somewhere beyond the link extending from port P13 of the switch 11-1. This means that the port P13 is now required to handle tagged frames containing a VID value of “4” because of the relocation of the terminal 10-1. With such a notification frame received from the server 12, the switch 11-1 updates its local VLAN configuration table accordingly. The above notification frame, however, may not be provided when the switch 11-1 supports the GARP VLAN registration protocol (GVRP), or when the switch 11-1 has no knowledge about the network topology. GVRP is an optional function for automatic distribution of VLAN configuration data, which is stipulated in the IEEE 802.1Q standard. GARP denotes the generic attribute registration protocol.
To summarize the above section, when a terminal is relocated, its local switch sends a query to the server 12 to identify to which VLAN the terminal belongs. The VLAN configuration table in each switch is updated in accordance with the new setup. In this way, the proposed system automatically reconfigures itself when a terminal is relocated, thus reducing the workload of the network administrators.
Referring next to
In the present context, the server 12 attempts to add a new entry to the terminal data table according to the policy option (5) described earlier, because the terminal 10-8 has no entry in the table. Suppose here that the selected policy says “add a new entry only when the terminal is allowed to become a member of a specific VLAN.” Consulting its VID data table (FIG. 9), the server 12 then suggests a specific VLAN to which the newly added terminal 10-8 is supposed to belong. Subsequently, the server 12 refers to its switch data table (
Besides returning the above-described response frame to the switch 11-3, the server 12 sends a notification frame to the switch 11-1, informing that a new terminal 10-8 belonging to VLAN #5 has been added at the network portion relevant to port 12 of the switch 11-1. This means that the port P12 is now required to handle tagged frames with a VID valued of “5” because of the enrollment of the new terminal 10-8. As previously noted, this notification, is not necessarily provided when that the switch 11-1 supports the GVRP protocol specified in IEEE 802.1Q, or when the switch 11-1 has no knowledge about the network topology. At any rate, if such a notification frame is received from the server 12, the switch 11-1 updates its own VLAN configuration table accordingly. In the case that no such notification frame is provided for any reason, the network administrator should do some necessary set-up task. To this end, the system may be designed to notify the administrator of the addition of a new terminal.
To summarize the above section, when a new terminal is added to the network, its local switch consults the VID data table to determine to which VLAN the terminal is supposed to belong. The VLAN configuration table in each switch is updated in accordance with the new setup. In this way, the proposed system automatically reconfigures itself and immediately enables the new terminal to start communication sessions.
Referring next to the flowchart of
That is, if the port number defined in the VLAN configuration table does not agree with the port which actually accepted the frame in question, this implies that the connection of that source terminal has been changed within the same local terminal group. If this is the case, the process advances to step S5.
That is, when a terminal has been relocated within a group of terminals being local to a specific switch (i.e., within the same local terminal group), the controller in that switch will handle this event according to the aforementioned policy option (2). If the first policy “request the server to provide necessary information” is selected, the process advances to step S3. If the second policy “update the configuration data by itself” is chosen, the process advances to step S6.
Referring next to
The “Current Local Switch” field needs no change in the case that the terminal in question remains within the same switch's local terminal group. The process then advances to step S29 in this case. Also, when the “Current Local Switch” status of the terminal is “Unknown” at present, this situation is equated with addition of a new terminal. Accordingly, the process advances to step S29.
In order for a switch to make a notification about to which port a terminal in question is coupled, the switch must have enough knowledge about topological configuration of the network. If only an insufficient knowledge is available, then the switch requests the network management server to provide information on the current usage of every switch, and searches for such switches that are related to a specific VLAN to which the terminal in question belongs to. The switches identified as such are then notified of the following information: (a) which terminal has been newly attached or relocated, (b) what VID the terminal has, (c) to which port the terminal has previously been connected, and (d) to which port the terminal is currently connected.
Referring next to
Through the process shown in the flowcharts of
When a notification message is received from the server 12; the switches will operate as shown in the flowchart of FIG. 16. This process comprises the following steps.
When a response message is received from the server 12, the requesting switch will operate as shown in the flowchart of FIG. 17. The process comprises the following steps.
See FIG. 11(B) for the response frame format. If the VID field 31 c contains the VID of the terminal in question, the process advances to step S53.
In the above embodiment of the invention, messages for use in server-switch communication sessions have been described as being constructed in a proprietary format shown in FIGS. 11(A) to 11(C). However, it is not intended to limit the implementation of frames to this specific format. It is also possible to use standard frame formats such as those in the Simple Network Management Protocol (SNMP) or Common Open Policy Service (COPS), as will be described below.
FIGS. 18(A) to 18(C) show several data message structures based on SNMP frame format. First, FIG. 18(A) gives the entire structure of an SNMP frame, which comprise the following fields: “Type” 40, “Length” 41, “Version” 42, “Community” 43, and “Protocol Data Unit (PDU)” 44. The last portion, PDU field 44, conveys the body of a message that is exchanged between a switch and a server.
FIG. 18(B) shows the detailed data structure of the PDU field 44. Actually, the PDU field 44 comprises the following fields: “Type” 44 a, “Length” 44 b, “Request ID” 44 c, “Error Status” 44 d, and “VarBindList” 44 e. The proposed usage of those data fields are as follows.
Referring to FIG. 18(C), the VarBindList field 44 e begins with “Type” subfield 44 ea and “Length” subfield 44 eb. They are followed by a single VarBind block or a series of VarBind blocks. Each VarBind block is composed of the following subfields: “Type” 44 ec, “Length” 44 ed, “Object ID (OID)” 44 ee, and “Object Syntax” 44 ef. In the example of FIG. 18(C), the Object Syntax field 44 ef contains the body of a message exchanged between a switch and a server, and the preceding OID field 44 ee indicates what kind of data is stored in the Object Syntax field 44 ef.
FIGS. 19(A) and 19(B) show the COPS frame structure. First, FIG. 19(A) gives the outline of a COPS frame, which comprises the following fields: “Version” 50, “op Code” 51, “Client-Type” 52, “Length” 53, and “PDU” 54.
Shown in parentheses are the corresponding terms that have been used in the present description of the invention.
Referring next to FIG. 19(B), the PDU field 54 is composed of the following fields: “Length” 54 a, “C-Num” 54 b, “C-Type” 54 c, and “Object contents” 54 d. The proposed usage of those fields is as follows.
The present invention provides automatic reconfiguration functions for VLANs. Once the server and switches are properly set up at a system initialization phase, subsequent changes such as terminal movements can be tracked by the system, without the need for intervention of network administrators. When a new terminal is connected, the system automatically enrolls it in an appropriate VLAN, thus allowing immediate startup without manual setting by the administrators. As such, the present invention totally alleviates the administrative workloads to maintain the network system.
The above-described processing mechanisms are actually implemented as software and hardware functions of a computer system. The process steps of the proposed network system are encoded into computer programs, which can be stored in an appropriate computer-readable storage medium. The computer system executes those programs to provide the intended functions of the present invention. Suitable computer-readable storage media include magnetic storage media and solid state memory devices. Portable storage media, such as CD-ROMs and floppy disks, are particularly suitable for circulation purposes. Further, it will be possible to distribute the programs through an appropriate server computer deployed on a network. The program files delivered to users are normally installed in their computer's hard drive or other local mass storage devices, and they are executed after being loaded to the main memory.
The processing steps that the server executes are relatively simple and can be implemented as software programs. They can even be provided as additional plug-ins for existing software of DNS servers and/or network management system (NMS) servers. It is therefore possible to integrate all those server functions on a single platform. Such a plug-in solution and the approach of integrated DNS/NMS servers also make it possible to provide a user-friendly network configuration screen.
At an initial setup stage, the associations between terminals and their VLAN domains are defined at the server in an organized way. Even when the network employs a large number of switches, they can be configured with simple parameters, with the reduced need for administrative tasks of configuring each switch.
Further, in the proposed network system, the server is where the VLAN membership of each terminal is determined. This arrangement simplifies the function of each switch, thus enabling the production of cost effective network switches.
The above discussion will now be summarized as follows. The present invention provides a network system comprising a plurality of terminals and switches and a server. Each terminal belongs to one of a plurality of logical groups, or VLANs. The switches interconnect the terminals by receiving and forwarding the packets originating therefrom. Each switch comprises: a first storage unit which stores information that is used to identify logical group membership of the source terminal of a received packet; a query unit which sends a query to request information about the logical group membership, when the first storage unit has failed to provide sufficient information to identify the logical group membership of a particular source terminal; and an updating unit which updates the information stored in the first storage unit according to a response to the query. The server comprises: a second storage unit which stores a list of identifiers of the terminals, in association with the logical groups to which the terminals belong; a searching unit which searches the second storage unit in response to the query from the requesting switch; and a transmission unit which sends the search result to the requesting switch. This structural arrangement permits the network system to quickly reconfigures its VLAN setup, even when a terminal is relocated or newly added.
The present invention also provides a switch for use in a network system where a plurality of terminals are interconnected by a plurality of switches that receive and forward packets originating from the terminals under the control of a server. This switch comprises: a storage unit which stores information that is used to identify logical group membership of the source terminal of a received packet; a query unit which sends a query the server to request information about the logical group membership, when the storage unit has failed to provide sufficient information to identify the logical group membership of a particular source terminal; and an updating unit which updates the information stored in the storage unit according to a response to the query sent by the query unit. This structural arrangement eliminates many of troublesome operations for VLAN setup, thus alleviating the workload imposed on the network administrators.
Further, according to the present invention, a server for use in a network system is provided. To control a plurality of switches interconnecting a plurality of terminals, this server comprises: a storage unit which stores a list of identifiers of the terminals in association with logical groups to which the terminals belong; a searching unit which searches the storage unit in response to a query from one of the switches; and a transmission unit which sends the search result to the switch that has sent the query. This structural arrangement permits a relocated or newly added terminal to quickly start communication sessions with other terminals.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.
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|U.S. Classification||370/254, 370/401, 370/338|
|International Classification||H04L12/46, H04L12/24|
|Cooperative Classification||H04L41/0893, H04L12/4641, H04L41/0816, H04L12/4691, H04L41/0856|
|European Classification||H04L41/08A2A, H04L12/46V3B2, H04L41/08F, H04L41/08B2, H04L12/46V|
|Jul 20, 2000||AS||Assignment|
Owner name: FUJITSU LIMITED, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:AMBE, MICHIKO;REEL/FRAME:010959/0763
Effective date: 20000510
|Oct 6, 2008||REMI||Maintenance fee reminder mailed|
|Mar 29, 2009||LAPS||Lapse for failure to pay maintenance fees|
|May 19, 2009||FP||Expired due to failure to pay maintenance fee|
Effective date: 20090329