Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-10-01
2001-02-13
Ton, Dang (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S252000
Reexamination Certificate
active
06188689
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a node (router) that is capable of connecting communication networks such as for example Ethernets and that is capable of transferring packets at the frame level defined in the datalink layer, and to a method of frame transfer.
A router device is used for connecting LANs (Local Area Networks) and transfers datagrams from one LAN to another LAN. In addition to the communication information data to be transferred, the datagram includes the network-layer addresses of its source and destination (i.e. source IP address and destination IP address in a case of IP (Internet Protocol)). The router determines a next-hop node (router or host) and an output interface of the datagram based on the destination address.
In a conventional router, when datalink frames (for example, Ethernet frames) defined in the datalink layer (for example, MAC (Media Access Control) layer) are received from one LAN, these frames are first subjected to the datalink-layer processing, then converted into a packet for being subjected to the network-layer processing.
The output interface and the network-layer address of the next-hop node of this packet are then determined from the network-layer destination address contained in this packet, so that this packet can then be handed over to the corresponding output interface. At this output interface, the datalink-layer address is determined from the network-layer address of the next-hop node and then the packet is converted into datalink frames to be output to another LAN.
The router that transfers communication information (datalink frames) by the procedure described above, after converting received datalink frames into a network-layer packet, determines a node to which this packet is next to be sent (next-hop router or destination host) and an output interface corresponding to the next-hop node, by referring to the content of this packet such as the network-layer address of the final destination (and source address) and by using a network-layer routing table held in the router, and then converts the packet into datalink frames once more to output the frames to the next-hop node.
In the conventional router, the excessive amount of processing within the router involved in the conversion of received datalink frames into a packet, lookup of the network-layer routing table, and conversion of the packet into datalink frames resulted in a large processing time being required for the frame transfer and in a large processing load required within the router.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a mechanism for determining the next transfer target of a received datalink frame, without frame-packet conversion and without network-layer processing, to transfer the datalink frame along the path prescribed for the packet by a network-layer routing protocol.
Datalink frames may be connectionless-type frames such as MAC frames or connection-oriented frames such as cells in ATM (Asynchronous Transfer Mode) or frames in frame relay. The present invention will be applied to a case of receiving a connectionless-type frame and transferring it as (transmitting) a connectionless-type frame, or a case of receiving a connectionless-type frame and transferring it as (transmitting) a connection-oriented frame, or a case of receiving a connection-oriented frame and transferring it as (transmitting) a connectionless-type frame.
According to one aspect of the present invention, there is provided a node, comprising: first means for transferring a connection-less type frame received from one logical network to another logical network by assembling a packet from the received frame and by referring to a destination network-layer address in the packet; a memory for storing a correspondence relationship between an input dedicated virtual link identifier allocated dedicatedly to a specified flow and information for designating a next-hop node to which a frame of the specified flow is to be transferred; and second means for transferring a connection-less type frame received from one logical network to another logical network by referring to the correspondence relationship stored in the memory based on the input dedicated virtual link identifier written in the received frame using a Media Access Control (MAC) address field and by writing the information for designating the next-hop node in the frame to be transferred.
According to another aspect of the present invention, there is provided a node, comprising: first means for transferring a frame received from a connection-less logical network to a connection-oriented logical network by assembling a packet from the received frame and by referring to a destination network-layer address in the packet; a memory for storing a correspondence relationship between an input dedicated virtual link identifier allocated dedicatedly to a specified flow and a virtual connection connected with a next-hop node to which a frame of the specified flow is to be transferred; and second means for transferring a frame received from the connectionless logical network to the connection-oriented logical network using the virtual connection by referring to the correspondence relationship stored in the memory based on the input dedicated virtual link identifier written in the received frame.
According to yet another aspect of the present invention, there is provided a node, comprising: first means for transferring a frame received from a connection-oriented logical network to a connection-less logical network by assembling a packet from the received frame and by referring to a destination network-layer address in the packet; a memory for storing a correspondence relationship between a virtual connection to be used for receiving a frame of a specified flow and an output dedicated virtual link identifier allocated dedicatedly to the specified flow and/or a MAC address of a next-hop node to which a frame of the specified flow is to be transferred; and second means for transferring a frame received from the connection-oriented logical network to the connection-less logical network by referring to the correspondence relationship stored in the memory based on the virtual connection used for receiving the frame and by writing the output dedicated virtual link identifier and/or the MAC address of the next-hop node in the frame to be transferred.
According to yet another aspect of the present invention, there is provided a node belonging to one logical network for transmitting a frame to a destination node belonging to another logical network, comprising: first means for transmitting a connection-less type frame of a packet by writing a MAC address of a next-hop node determined based on a network-layer address of the destination node in the packet in a MAC address field of the frame; a memory for storing a dedicated virtual link identifier allocated between the node and the next-hop node dedicatedly to a specified flow; and second means for transmitting a connection-less type frame of the specified flow by writing the dedicated virtual link identifier stored in the memory in the frame using the MAC address field.
According to yet another aspect of the present invention, there is provided a method of frame transfer, comprising the steps of: storing a correspondence relationship between an input dedicated virtual link identifier allocated in one logical network dedicatedly to a specified flow and information for designating a next-hop node in another logical network to which a frame of the specified flow is to be transferred; transferring a frame received from one logical network to another logical network by referring to the correspondence relationship stored in the memory based on the input dedicated virtual link identifier written in the received frame using a MAC address field and by writing the information for designating the next-hop node in the frame to be transferred; and transferring another frame received from one logical network to another logical network by assembling a pac
Katsube Yasuhiro
Matsuzawa Shigeo
Yamato Katsumi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Sam Phirin
Ton Dang
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