EP0465201A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Bridge-like internet protocol router
Assignee: Digital Equipment Corp
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Filing: 1991-07-01
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Granted: —
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Expires: 2011-07-01
Abstract
Abstract A device and related method for coupling segments of an extended local area network (LAN) in such a way that message traffic employing inter-network protocols such as TCP/IP will be handled without the difficulties usually associated with bridges, and without the complexity and expense of full IP router capability. The device operates like a bridge for non-TCP/IP traffic. For TCP/IP traffic it operates in a bridge-like manner but maintains a database associating extended LAN segment addresses with port numbers in the device, so that packets can be automatically forwarded over a spanning tree connecting the network segments. A host computer in any network segment can address others in different network segments of the extended LAN as though all were in a single LAN. The device of the invention functions to block the flow of ARP messages and to generate ARP replies that render the device of the invention transparent to hosts within the extended LAN. The device is also transparent to true IP routers, which may still be used to effect communication with points outside the extended LAN.
Inventors
- 👤 Radia Joy Perlman
- 👤 G. Paul Koning
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 19:20
CPC Classifications
H; H04; H04L; H04L12/00; H04L12/28; H04L12/46; H04L12/4604; H04L12/462; H04L12/4625
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
173 words
For use in an extended interconnected local area network (10) (LAN) handling message traffic in accordance with a set of inter-network protocols that use a network addressing scheme, a bridge-like Internet Protocol (IP) router (22, 24) (BLIP), characterized by: multiple ports for attaching the BLIP to multiple segments (12, 14, 16) of an extended LAN; means (40) for distinguishing received message traffic that uses the inter-network protocols from other message traffic that does not use the protocols; bridge means (42) for processing the other message traffic exactly in the manner of a conventional bridge, using unique station addresses to determine how to forward the message traffic; and bridge-like means (44) for processing the inter-network protocol traffic in a manner analogous to a bridge, wherein a message packet received from an extended LAN segment attached to the BLIP is forwarded if necessary to at least one other extended LAN segment attached to the BLIP, using network addresses and network segment addresses, instead of unique station addresses, to determine how to forward the message traffic.
Claim 2
Dependent Claim
22 words
A bridge-like IP router as defined in claim 1, and further comprising: means for processing address resolution messages requesting destination address information.
Claim 3
Dependent Claim
119 words
A bridge-like IP router as defined in claim 2, wherein; the means for processing address resolution messages includes means for detecting and discarding address resolution messages requesting destination address information, and means for responding to the address resolution messages with a special address code when the requested destination address is on a different segment of the same extended LAN as the BLIP; and the bridge-like means includes means for forwarding a message packet having the special address code, to some subset of the attached extended LAN segments except the one from which the message packet was received; whereby a host device may transmit to destinations on other extended LAN segments as though the destinations were on the same LAN.
Claim 4
Dependent Claim
119 words
A bridge-like IP router as defined in claim 3, wherein: the means for processing address resolution messages includes means for detecting and discarding address resolution messages requesting destination address information, and means for responding to the address resolution messages with a special address code when the requested destination address is on a different segment of the same extended LAN as the BLIP; and the bridge-like means includes means for forwarding a message packet having the special address code, to some subset of the attached extended LAN segments except the one from which the message packet was received; whereby a host device may transmit to destinations on other extended LAN segments as though the destinations were on the same LAN.
Claim 5
Dependent Claim
60 words
A bridge-like IP router as defined in claim 4, wherein the bridge-like means includes: an IP database associating each segment of the extended LAN with a port of the BLIP; and means for updating the IP database by obsering each received message and correlating the segment address for each message source with a port through which the message is received.
Claim 6
Dependent Claim
63 words
A bridge-like IP router as defined in claim 4, wherein the bridge-like means includes: an ARP database associating each network layer address in attached exended LAN segments with a corresponding data link layer address; and means for updating the ARP database by sending ARP messages directed to specific network layer addresses and processing ARP replies that contain the corresponding data link layer addresses.
Claim 7
Dependent Claim
33 words
A bridge-like IP router as defined in claim 4, wherein the bridge-like means includes: a router database containing the data link layer addresses of all true IP routers connected to the extended LAN.
Claim 8
Independent Claim
122 words
A method of operation of extended interconnected local area networks (LANs) handling message traffic in accordance with a set of protocols known as TCP/IP, the method comprising the steps of: configuring an extended local area network (LAN) to include a plurality of extended LAN segments connected by bridge-like IP routers (BLIPs); receiving a packet of data at a BLIP; characterized by: determining whether the packet has been transmitted under TCP/IP protocols; processing non-TCP/IP packets in the manner of a convention bridge; and processing TCP/IP traffic in a manner analogous to a bridge, wherein a message packet received from an extended LAN segment attached to the BLIP is forwarded if necessary to at least one other extended LAN segment attached to the BLIP.
Claim 9
Dependent Claim
86 words
A method as defined in claim 8, and further comprising: detecting and discarding ARP messages requesting destination address information; responding to ARP messages with a special address code when the requested destination address is on a different segment of the same extended LAN as the BLIP; and forwarding a message packet having the special address code, to at least one other attached LAN segment; whereby a host device may transmit to destinations on other extended LAN segments as though the destinations were on the same LAN.
Claim 10
Dependent Claim
58 words
A method as defined in claim 8, and further comprising: maintaining an IP data base that associates each setment of the extended LAN with a port of the BLIP; wherein the maintaining step is performed by observing each received message and correlating the segment address for each message source with a port through which the message is received.
Claim 11
Dependent Claim
60 words
A method as defined in claim 8, and further comprising; maintaining an ARP database that associates each network layer address in attached extended LAN segments with a corresponding data link layer address; wherein the maintaining step is performed by sending ARP messages directed to specific network layer addresses and processing ARP replies that contain the corresponding data link layer addresses.
Claim 12
Dependent Claim
30 words
A method as defined in claim 8, and further comprising: maintaining a router database containing the data link layer addresses of all true IP routers connected to the extended LAN.
Claim 13
Independent Claim
259 words
A method of operation of a configuration of interconnected local area networks (LANs) handling message traffic in accordance with a set of protocols known as TCP/IP, the method comprising the steps of: configuring an extended local area network (LAN) to include a plurality of extended LAN segments connected by bridge-like IP routers (BLIPs); receiving a packet of data at a BLIP; determining whether the packet has been trasmitted under TCP/IP protocols; processing non-TCP/IP packets in a manner of a conventional bridge; processing non-TCP/IP traffic in a manner analogous to a bridge, wherein a message packet received from an extended LAN segment attached to the BLIP is forwarded if necessary to at least one other extended LAN segment attached to the BLIP; detecting and discarding ARP messages requesting destination address information; configuring an extended local area network (LAN) to include a plurality of extended LAN segments connected by bridge-like IP routers (BLIPs); receiving a packet of data at a BLIP; determining whether the packet has been transmitted under the inter-network protocols; processing packets that were not transmitted under the inter-network protocols in the manner of a conventional bridge, using unique station addresses to determine how to forward the packets; and processing inter-network protocol traffic in a manner analogous to a bridge, wherein a message packet received from an extended LAN segment attached to the BLIP is forwarded if necessary to at least one other extended LAN segment attached to the BLIP, using network addresses and network segment addresses, instead of unique station addresses, to determine how to forward the packets.
Claim 14
Dependent Claim
87 words
A method as defined in claim 13, and further comprising: determining whether a received message packet is destined for an attached segment of the extended LAN; forwarding a packet destined for an attached segment other than the one from which the packet was transmitted, by obtaining a data link layer destination address from the ARP database; and forwarding a packet destined for a segment unattached to the BLIP, by transmitting the packet to at least one other segment through a port selected to reach the destination segment.
Claim 15
Dependent Claim
49 words
A method as defined in claim 14 and further comprising: checking the destination address of every packet destined for the same extended LAN segment as the one from which the packet was transmitted; and taking corrective action depending on the data link layer destination address contained in the packet.
Claim 16
Dependent Claim
42 words
A method as defined in claim 15, wherein the step of taking corrective action includes: discarding the packet if the data link layer destination address matches an entry in the ARP database corresponding to an IP destination address contained in the packet.
Claim 17
Dependent Claim
77 words
A method as defined in claim 15, wherein the step of taking corrective action includes, if there is no match between the data link layer destination address in the packet and an entry in the ARP database corresponding to an IP destination address contained in the packet: substituting the ARP database entry for the data link layer destination address in the packet; and sending a redirect message to a source host from which the packet was transmitted.
References Cited (Backward Citations)
No citation records indexed.
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