JP2009135818A - Packet transfer apparatus, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transmit a packet issued from a certain node to one unspecified edge node on a packet communication network such as an IP communication network. <P>SOLUTION: Routers 11, 12 receive a packet wherein an edge node that becomes a destination is not specified at all, selects one packet transfer destination from among routers and edge nodes connected thereto, and transmits the received packet to the packet transfer destination. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a packet transfer apparatus and a computer program.

Conventionally, in an IP (Internet Protocol) communication network such as the Internet, a communication partner is specified using an IP address assigned to a communication device (node). The IP address can be roughly classified into three types, that is, a unicast address, a multicast address, and an anycast address. A unicast address designates one specific node, and unicast is most often used. The multicast address designates the entire group consisting of a plurality of nodes. Broadcast (communication form in which the entire node is designated as a destination) can be considered as a kind of multicast. The anycast address designates one optimal node in a group of a plurality of nodes. Anycast is used, for example, to distribute the load on a DNS server using a single DNS server at the optimal network location for a user node in a group of multiple DNS servers (name servers) as a communication partner, This is used when, for example, one HA that is optimal for a user node among multiple HAs (Home Agents) in the network is used as a communication partner to dynamically discover HAs in Mobile IPv6.
RFC4601, “Protocol Independent Multicast-Sparse Mode (PIM-SM): Specification” RFC1546, “Host Anycasting Service”

  However, in the above-described conventional communication forms (unicast, multicast and anycast), it is difficult to realize delivery of a packet transmitted from a certain node to an unspecified one edge node on the IP communication network. . In unicast, the destination node must be specified at the time of transmission. Multicast and anycast are communication modes in which a group of edge nodes that can be destinations is clearly indicated in a packet, and the packet destination is limited to edge nodes belonging to the group. In broadcast, a packet is delivered to all edge nodes on the IP communication network.

  An example of a method for randomly selecting a packet destination is to generate a destination address using a random number generator. However, with this method, there is a possibility that a nonexistent IP address is generated and the packet reaches nowhere and is discarded. Alternatively, an IP address assigned to the relay node instead of the edge node may be generated, and the packet may not reach the edge node. Usually, the other party who wants to deliver the packet is considered to be an edge node (a node other than the relay node) that is performing some service or receiving some service.

  In addition, it is conceivable that the sender randomly collects IP addresses assigned to the existing edge nodes and randomly selects a destination address from them, but this method places a heavy burden on the sender.

  The present invention has been made in consideration of such circumstances, and its purpose is to deliver a packet transmitted from a certain node to an unspecified one edge node on a packet communication network such as an IP communication network. An object of the present invention is to provide a packet transfer device and a computer program that can be used.

  In order to solve the above problems, a packet transfer apparatus according to the present invention includes a packet transfer apparatus in a packet communication network in which packet transfer apparatuses are connected to each other and between the packet transfer apparatus and an edge node through communication lines. Is a packet transfer device that is connected to both the packet transfer device and the edge node, and is connected to the reception device for receiving a packet in which an edge node that can be a destination is not specified at all. And a transfer destination selecting means for selecting one packet transfer destination from the packet transfer apparatus and the edge node, and a transmission means for transmitting the received packet to the packet transfer destination.

  The packet transfer apparatus according to the present invention has route information including information on the distance on the network to the edge node, and the transfer destination selection unit is configured to limit the distance on the network for the packet to reach the edge node. Based on the above, a packet transfer destination is selected.

  In the packet transfer apparatus according to the present invention, the transfer destination selection means selects a packet transfer destination so as to reach an edge node within a packet arrival range specified by the received packet.

  In the packet transfer apparatus according to the present invention, the path information includes a minimum transfer count on the network to the edge node, and the transfer destination selection means reaches the edge node within the upper limit of the transfer count of the received packet. Thus, the packet transfer destination is selected, and the packet transfer apparatus transfers the received packet after subtracting 1 from the upper limit of the transfer count of the received packet.

  The packet transfer apparatus according to the present invention is characterized in that the transfer destination selection means randomly selects a packet transfer destination.

  In the packet transfer apparatus according to the present invention, the transfer destination selection means selects a packet transfer destination with equal probability.

  In the packet transfer apparatus according to the present invention, the transfer destination selecting means weights and selects a packet transfer destination with a weight corresponding to a distance on the network to the edge node.

  The packet transfer apparatus according to the present invention is characterized in that the packet transfer destination is temporarily selected so as to be away from the edge node within a certain range.

The computer program according to the present invention is connected to only a packet transfer device in a packet communication network in which packet transfer devices and between a packet transfer device and an edge node are connected by a communication line, or a packet A computer program for performing packet transfer processing in a packet transfer apparatus connected to both the transfer apparatus and the edge node, the reception function for receiving a packet in which an edge node that can be a destination is not specified at all; A computer realizes a transfer destination selection function for selecting one packet transfer destination from among connected packet transfer apparatuses and edge nodes, and a transmission function for transmitting the received packet to the packet transfer destination. To do.
As a result, the packet transfer apparatus described above can be realized using a computer.

  According to the present invention, it is possible to obtain an effect that a packet transmitted from a certain node can be delivered to an unspecified one edge node on a packet communication network such as an IP communication network.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an IP communication network according to an embodiment of the present invention. In this embodiment, IPv4 (Internet Protocol Version 4) is handled.
In FIG. 1, the IP communication network includes a backbone router 11, an edge router 12, and an edge node 13. The trunk router 11 is connected to another trunk router 11 or edge router 12 via a communication line. The edge router 12 is connected to the backbone router 11 or another edge router 12 through a communication line, and is also connected to the edge node 13.

  The backbone router 11 is a router that transmits and receives packets to and from other backbone routers 11 or edge routers 12. The edge router 12 transmits / receives a packet to / from the trunk router 11 or another edge router 12 and also transmits / receives a packet to / from the edge node 13. In the following description, the term “router” includes both the basic router 11 and the edge router 12. The router is a relay node and has a packet transfer function.

  The edge node 13 is a node that transmits or receives a packet, such as a user terminal or a server. The edge node 13 may be connected to the edge router 12 via an access network.

[Communication mode according to this embodiment]
In the communication mode according to the present embodiment, a packet transmitted from a certain edge node is delivered to one unspecified edge node on the IP communication network. The packet is a packet for which no edge node that can be a destination is specified. This communication mode is referred to as “unspecified communication”. Further, the present embodiment has the following features.
(1) The destination of the packet is only the edge node.
(2) A packet is delivered to an existing edge node. However, it is not essential that the edge node receiving the packet responds.
(3) A range (packet arrival range) to which a packet is delivered can be specified. The packet reach is expressed by a distance on the network. As the distance on the network, the number of hops (the number of times through the router) can be used.

[How to specify the communication type]
A method for designating the communication form of the packet when the edge node 13 transmits the packet will be described.
The source edge node 13 does not specify an edge node that can be a destination in a packet to be transmitted. Instead, the source edge node 13 clearly indicates in the packet that the packet to be transmitted is unspecified communication. Also, the packet reachable range can be specified. As a method for realizing these, two examples are given below.

(Method 1) Specifying only by destination IP address
In the IP header, the destination IP address has a 32-bit (4 bytes) configuration, and 3 bytes are used to indicate unspecified communication, and the remaining 1 byte designates the packet reachable range. FIG. 2 shows the address configuration. For example, it is defined that the value of the upper 3 bytes of the address “254.0.0.xxx” indicates unspecified communication, and the lower 1 byte (xxx portion) indicates the packet reachable range. The upper limit of the number of hops is used for the packet reach. This definition is well known throughout the IP communication network.

(Method 2) Specifying using the destination IP address and TTL (Time To Live)
Indicates that unspecified communication is performed using all 4 bytes of the destination IP address in the IP header. Further, the packet reachable range is specified using the TTL field (8 bits) in the IP header. This definition is well known throughout the IP communication network.

  The source edge node 13 uses the method 1 or 2 to generate a packet in which no edge node that can be a destination is specified. Any of the methods 1 and 2 may be used, but the method 1 will be described below as an example. The packet reachable range is represented by the upper limit of the number of hops.

[Route Information Management Method in Router]
Each router holds and manages the minimum number of hops to the edge node 13 as a value “EdgeDistance”. Each router recognizes the distance to the edge node 13 by exchanging “EdgeDistance” between the routers. FIG. 3 shows a route information management procedure. The edge router 12 in FIG. 3 is connected to the access network. An edge node 13 is connected to the access network.

With reference to FIG. 3, a method of managing route information in the router will be described.
Step 1: The edge router 12 (R1) advertises the “EdgeDistance” value “1” to the adjacent router. The advertisement [R1, 1] in FIG. 3 indicates that the source edge router 12 (R1) advertises the “EdgeDistance” value “1”. The edge router 12 (R1) transmits the advertisement [R1, 1] from all the interfaces connected to the router. That is, the advertisement [R1, 1] is transmitted from all interfaces other than the interface connected to the access network.

  In step 1, the routing table 30 of the edge router 12 (R1) in FIG. 3 stores its own interface number IF0 and “EdgeDistance” value “0” in association with each other. The “EdgeDistance” value “0” indicates that the number of hops to the edge node 13 is zero. Therefore, the route table 30 indicates that the interface (IF0) is connected to the access network.

  Step 2: The router that has received the advertisement [R1, 1] (the trunk router 11 (R2) in the example of FIG. 3) sets the IP address of the source router and the “EdgeDistance” value “1” to the routing table for unspecified communication. 40. In the route table 40 of the trunk router 11 (R2) in FIG. 3, the IP address of the source router (R1) and the “EdgeDistance” value “1” are stored in association with each other based on the advertisement [R1, 1]. . The routing table 40 indicates that the minimum number of hops to the edge node 13 is 1 via the router (R1).

  Step 3: The backbone router 11 (R2) refers to the routing table 40, and if the “EdgeDistance” value “1” received this time is the minimum value received so far, or has received the “EdgeDistance” value for the first time. In this case, a value obtained by adding 1 to the received value is set as its own “EdgeDistance” value. In the example of FIG. 3, since the “EdgeDistance” value is received for the first time, the “EdgeDistance” value of the backbone router 11 (R2) is set to “2”. Then, it progresses to step 4. On the other hand, if the “EdgeDistance” value “1” received this time is not the minimum value received so far, the “EdgeDistance” value is not updated and the processing is terminated.

  Step 4: The core router 11 (R2) advertises its updated “EdgeDistance” value “2” to the adjacent router. The backbone router 11 (R2) transmits the advertisement [R2, 2] from all the interfaces connected to the router.

Step 2 ′: The backbone router 11 (R3) that has received the advertisement [R2, 2] registers the IP address of the transmission source router and the “EdgeDistance” value “2” in the routing table 50 for unspecified communication. The route table 50 of the trunk router 11 (R3) in FIG. 3 stores the IP address of the source router (R2) and the “EdgeDistance” value “2” in association with each other based on the advertisement [R2, 2]. . The route table 50 indicates that the minimum number of hops to the edge node 13 is 2 via the router (R2). Also, the edge router 12 (R1) that has received the advertisement [R2, 2] registers the IP address of the transmission source router and the “EdgeDistance” value “2” in the routing table 30 for unspecified communication.
Then, it progresses to step 3.

  By this method, all routers in the IP communication network can know the minimum number of hops to the edge node 13. In the example of FIG. 3, the router (R1) has an “EdgeDistance” value “1”, the router (R2) has an “EdgeDistance” value “2”, and the router (R3) has an “EdgeDistance” value “3”. Note that the unspecified communication route table possessed by each router has only information on adjacent routers. However, only the edge router 12 also has information regarding an interface connected to the access network.

[Packet forwarding method in router]
All routers in the IP communication network know the minimum number of hops to the edge node 13 by the above-described route information management method. When the destination IP address of the received packet specifies unspecified communication (see FIG. 2), the router transfers the received packet by the packet transfer method described below.

A packet transfer method in unspecified communication will be described with reference to FIG.
The router receives a packet in which no edge node that can be a destination is specified. The destination IP address shown in FIG. 2 specifies that the packet is unspecified communication by the unspecified communication specifying unit, and the packet reachable range specifying unit specifies the upper limit of the hop number of the packet.

  Step 11: When the destination IP address of the received packet specifies unspecified communication, the router updates the hop number upper limit included in the destination IP address by one. Here, as shown in FIG. 4, since the upper limit of the hop number of the received packet is 3, the packet reachable range designation part in the destination IP address of the received packet is rewritten with the upper limit “2” of the hop number subtracted by 1.

  Step 12: The router randomly selects one entry from the entries whose “EdgeDistance” value is less than or equal to the updated hop count upper limit “2” of the received packet in the routing table 60 for unspecified communication. In the example of the routing table 60 of FIG. 4, the entries whose EdgeDistance ”value is 2 or less are 4 of the interface (IF0) entry, the router (R1) entry, the router (R2) entry, and the router (R3) entry. Therefore, the router randomly selects one entry from the four entries, and it is assumed here that the entry of the router (R2) is selected.

  Step 13: The router transfers the received packet to the router (R2) of the entry of the selection result.

  In the route table 60 of FIG. 4, the entry of the interface (IF0) connected to the access network is registered only when the router is the edge router 12. When the interface (IF0) entry is selected in step 12, the edge router 12 transfers the received packet by the packet transfer method described below. This packet transfer method will be described with reference to FIG.

  The edge router 12 performs processing for resolving the layer 2 (L2) address when the interface (IF0) connected to the access network is selected as a result of the random selection in step 12 above. This is a process of randomly selecting a transfer destination edge node 13 in order to transfer a packet to only one edge node in the access network. Specifically, one L2 address is randomly selected from the list of L2 addresses assigned to each edge node 13 in the access network connected to the interface (IF0). Examples of the L2 address include a MAC (Media Access Control) address. Examples of the physical address list include an ARP (Address Resolution Protocol) table.

  In FIG. 5, the edge router 12 randomly selects one entry from the interface (IF0) entries in the ARP table 70. In the example of the ARP table 70 of FIG. 5, the interface (IF0) entry includes a MAC address (MACa) entry, a MAC address (MACb) entry, a MAC address (MACc) entry, and a MAC address (MACd) entry. There are four. Accordingly, the edge router 12 randomly selects one entry from the four entries. Here, it is assumed that the entry of the MAC address (MACb) is selected.

  The edge router 12 uses the MAC address (MACb) of the entry of the selection result as the destination address of the L2 frame, stores the received packet in the L2 frame, and transmits it. As a result, the received packet reaches the edge node 13 of the MAC address (MACb).

  As described above, according to the present embodiment, an effect that a packet transmitted from a certain node can be delivered to an unspecified one edge node on the IP communication network can be obtained.

  According to this embodiment, by using the “EdgeDistance” value included in the route table managed by each router, the packet is surely arrived at the edge node. That is, the packet is transferred such that the minimum hop number to the edge node satisfies the hop number upper limit of the received packet.

  If the upper limit of the number of hops of unspecified communication packets is originally insufficient, the packet is discarded. In this case, an “ICMP unreachable” message may be returned to the packet source.

  Note that the router (packet transfer device) according to the present embodiment may be realized by dedicated hardware, or may be configured by a computer system such as a personal computer to realize the function of the router. The function may be realized by executing a program.

In addition, an input device, a display device, and the like are connected to the router as peripheral devices. Here, the input device refers to an input device such as a keyboard and a mouse. The display device refers to a CRT (Cathode Ray Tube), a liquid crystal display device or the like.
The peripheral device may be connected directly to the router or may be connected via a communication line.

Further, a program for realizing the function of the router (packet transfer apparatus) according to the present embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. Thus, packet transfer processing may be performed. Here, the “computer system” may include an OS and hardware such as peripheral devices.
“Computer-readable recording medium” refers to a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disk), and a built-in computer system. A storage device such as a hard disk.

Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic Random Access Memory)), etc., which hold programs for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, in step 12 described above, each entry in the routing table for unspecified communication may be selected with equal probability.

  Alternatively, the entry weight may be selected with a weight corresponding to the “EdgeDistance” value of each entry in the routing table for unspecified communication. In this case, the larger the “EdgeDistance” value, the larger the selection probability.

  In addition, as a packet transfer destination selection condition, it may be possible to ensure that the edge node is not further away from the edge node than necessary so that the edge node can always be reached. In this case, the router (packet transfer device) allows the packet transfer destination to be temporarily selected so as to be away from the edge node within a certain range.

  In the above-described embodiment, the routing table for unspecified communication is independently constructed, but a multicast distribution tree may be used. When distributing a packet by multicast, the router normally copies the packet and forwards it to all the downstream links of the multicast distribution tree. When performing unspecified communication, the router does not duplicate the packet, and only needs to forward the packet to one of the downstream link candidates. Also, the edge router randomly selects one of the edge nodes participating in the multicast group (Join) based on the “Join” message of the edge node, and forwards the packet to the selected edge node. do it. When a multicast delivery tree is used, a packet transfer destination that matches the packet reachable range may be selected based on the multicast delivery tree. Therefore, it is not necessary to manage the minimum number of hops to the edge node.

  The packet communication network according to the present invention is not limited to the IP communication network, and various packet communication protocols can be applied.

It is a block diagram which shows the structure of the IP communication network which concerns on one Embodiment of this invention. 4 is a configuration example of a destination IP address of a packet according to the embodiment. It is explanatory drawing for demonstrating the path | route information management method concerning the embodiment. It is explanatory drawing for demonstrating the packet transfer method concerning the embodiment. It is explanatory drawing for demonstrating the packet transfer method concerning the embodiment.

Explanation of symbols

11 ... backbone router (packet transfer device), 12 ... edge router (packet transfer device), 13 ... edge node

Claims (9)

In a packet communication network in which packet transfer devices and between packet transfer devices and edge nodes are respectively connected by communication lines, they are connected only to packet transfer devices, or both packet transfer devices and edge nodes A packet transfer device to be connected,
A receiving means for receiving a packet in which an edge node that can be a destination is not specified at all;
A transfer destination selecting means for selecting one packet transfer destination from among the packet transfer device and the edge node connected to the own device;
Transmitting means for transmitting the received packet to the packet transfer destination;
A packet transfer apparatus comprising: It has route information including information on the distance to the edge node on the network,
The packet transfer apparatus according to claim 1, wherein the transfer destination selection unit selects a packet transfer destination based on a restriction on a distance on the network for the packet to reach the edge node.   The packet transfer apparatus according to claim 2, wherein the transfer destination selection unit selects a packet transfer destination so as to reach an edge node within a packet arrival range specified by the received packet. The path information includes the minimum number of transfers on the network to the edge node,
The forwarding destination selecting means selects a packet forwarding destination so as to reach an edge node within the upper limit of the number of forwarding times of the received packet;
The packet transfer apparatus according to claim 3, wherein the packet transfer apparatus transfers the received packet after subtracting 1 from the upper limit of the transfer count of the received packet.   The packet transfer apparatus according to claim 1, wherein the transfer destination selection unit randomly selects a packet transfer destination.   The packet transfer apparatus according to claim 1, wherein the transfer destination selection unit selects a packet transfer destination with equal probability.   3. The packet transfer apparatus according to claim 2, wherein the transfer destination selection unit weights and selects the packet transfer destination with a weight corresponding to a distance on the network to the edge node.   3. The packet transfer apparatus according to claim 2, wherein a packet transfer destination is allowed to be temporarily moved away from an edge node within a certain range. In a packet communication network in which packet transfer devices and between packet transfer devices and edge nodes are respectively connected by communication lines, they are connected only to packet transfer devices, or both packet transfer devices and edge nodes A computer program for performing packet transfer processing in a connected packet transfer device,
A reception function for receiving a packet in which an edge node that can be a destination is not specified at all;
A transfer destination selection function for selecting one packet transfer destination from among a packet transfer device and an edge node connected to the own device;
A transmission function for transmitting the received packet to the packet transfer destination;
A computer program for causing a computer to realize the above.