Method of using routing protocols to reroute packets during a link failure

• US 6,301,223 B1
• Filed: 04/11/1997
• Issued: 10/09/2001
• Est. Priority Date: 01/17/1997
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Hrastar, Scott E., Merrill, Todd A., Bowcutt, Roy A.
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Phunkulh, Bob A.
• Application Number:
  US08/837,073
• Time in Patent Office: 1,642 Days
• Field of Search: 370/216, 370/217, 370/218, 370/219, 370/220, 370/221, 370/225, 370/226, 370/227, 370/228, 370/242, 370/243, 370/244, 370/245, 395/200.68, 395/200.69, 395/200.7, 395/200.71, 395/200.72, 395/200.73, 395/200.74, 709/239, 375/222
• US Class Current: 370/227
• CPC Class Codes: H04H 20/79 using downlink of the CATV systems, e.g. audio broadcast via CATV network
• CPC Class Codes: H04H 60/84 which are fixed telephone networks
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/2856 Access arrangements, e.g. Internet access asynchronous transfer mode networks H04L12/5601; broadband local area networks H04L12/2801; optical access or distribution networks H04Q11/0067; access to open networks H04L12/5691; digital subscriber line end-user equipment and bit-level processing of data on a PSTN-based network H04M11/00; home network gateways H04L12/2834; wireless access networks H04W
• CPC Class Codes: H04L 12/2863 Arrangements for combining access network resources elements, e.g. channel bonding modem pooling H04L25/14; routing of packets H04L45/00; multichannel or multilink protocols H04L69/14
• CPC Class Codes: H04L 12/2872 Termination of subscriber connections
• CPC Class Codes: H04L 12/2874 Processing of data for distribution to the subscribers
• CPC Class Codes: H04L 12/5692 Selection among different networks
• CPC Class Codes: H04L 2101/604 Address structures or formats
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 41/0213 Standardised network management protocols, e.g. simple network management protocol [SNMP]
• CPC Class Codes: H04L 41/0663 Performing the actions predefined by failover planning, e.g. switching to standby network elements
• CPC Class Codes: H04L 41/0677 Localisation of faults
• CPC Class Codes: H04L 61/50 Address allocation
• CPC Class Codes: H04L 61/5007 Internet protocol [IP] addresses
• CPC Class Codes: H04L 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]
• CPC Class Codes: H04L 61/5061 Pools of addresses
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04N 21/25816 : involving client authentication restricting access to computer systems by authenticating users using a predetermined code G06F21/33; cryptographic authentication protocols H04L9/32; networks authentication protocols H04L63/08; authentication in wireless network security H04W12/06
• CPC Class Codes: H04N 21/42676 : for modulating an analogue carrier signal to encode digital information or demodulating it to decode digital information, e.g. ADSL or cable modem
• CPC Class Codes: H04N 21/6118 : involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 : involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/17309 : Transmission or handling of upstream communications

Abstract

An asymmetrical network for coupling customer-premises Internet hosts such as personal computers to the Internet. The head end of a CATV system has a high-bandwidth connection to the Internet. The down link connecting the personal computers to the Internet is the cables provided by the CATV system; the up link is a telephone connection to the head end. A router is connected to the down link by means of an RF modem, to the up link by means of an analog modem, and to a LAN which is connected to the Pcs. The router routes IP packets for the hosts that are received on the CATV cable to the hosts via the LAN; it routes IP packets from the hosts that are destined for the Internet to the head end via the telephone line. The asymmetrical network conserves IP addresses and addresses on the CATV cable by dynamically allocating the IP addresses for an RF modem'"'"'s hosts and an address on the CATV cable for the RF modem in response to a request made by the RF modem via the telephone line. It further saves IP addresses by assigning a non-unique IP address to the router for use inside the LAN. When the CATV system fails, the asymmetrical network automatically begins to use the telephone line as both the up link and the down link, and when the CATV system is restored, the asymmetrical network automatically returns to using the CATV cable as the down link and the telephone line as the up link. A further feature of the asymmetrical network is that the head end components and the RF modem have IP addresses, so that standard TCP/IP protocols can be used to control the asymmetrical network.

Claims

1. A cable modem apparatus for reliably providing a personal computer access to the Internet through a cable television link and a public switched telephone network link, said apparatus comprising:

a cable television link failure detector connected to the cable television link;

a message generator connected to said cable television link failure detector, wherein said message generator is configured to generate at least one message responsive to said cable television link failure detector detecting cable television link failures;

a message transmitter connected to said message generator, wherein said message transmitter is configured to transmit the at least one message through the public switched telephone network link to cause Internet communications to be communicated to the personal computer through the public switch telephone network link;

a failure ended message generator connected to said cable television link failure detector, wherein said failure ended message generator is configured to generate failure ended messages responsive to said cable television link failure detector detecting cable television link failure endings; and

a failure ended message transmitter connected to said failure ended message generator, wherein said failure ended message transmitter is configured to transmit failure ended messages through the public switched telephone network link to cause Internet communications to again be communicated to the personal computer through the cable television link.

2. The apparatus of claim 1, wherein the message generated responsive to said cable television link failure detector detecting cable television link failures also causes a suspension of Internet communications communicated through the cable television link.

3. The apparatus of claim 1, wherein said message generator configured to generate at least one message responsive to said cable television link failure detector detecting cable television link failures is further configured to generate messages as long as said cable television link failure detector detects cable television link failures, and said message transmitter configured to transmit the at least one message through the public switched telephone network link to cause Internet communications to be communicated to the personal computer through the public switch telephone network link is further configured to transmit messages as long as said cable television link failure detector detects cable television link failures.

4. A method for routing data communicated to a first router from a second router, wherein the first router and the second router are connected by a first communication path and a second communication path, said method comprising steps of:

routing data from the second router to the first router through the first communication path;

receiving at the second router at least one message through the second communication path;

determining from the at least one message that the first communication path has failed;

changing at least one routing table responsive to receiving the at least one message through the second communication path;

routing data from the second router to the first router through the second communication path, responsive to changing at least one table;

receiving at least one network status message through the second communication path;

determining from the at least one network status message the first communication path is operative,

changing the at least one routing table responsive to determining that the first communication path is operative; and

routing data from the second router to the first router through the first communication path, responsive to changing the routing tables.

5. The method of claim 4, wherein the step of routing data through the second communicating path includes the second router suspending attempts to route data to the first router through the first communication path.

6. The method of claim 4, wherein the at least one message is transmitted from the first router.

7. The method of claim 4, wherein the at least one message includes a network routing protocol packet.

8. The method of claim 4, wherein the at least one message includes a SNMP trap packet.

9. The method of claim 4, wherein the at least one message includes a RIP packet.

10. The method of claim 4, wherein the at least one message includes a table of operative communication paths to the first router.

11. The method of claim 4, wherein the at least one message includes a table of paths distinct from operative communication paths to the first router.

12. The method of claim 4, wherein:

the data includes IP packets including IP addresses;

the first router being connected to at least one personal computer; and

the second router being connected to the Internet.

13. The method of claim 4, wherein:

the first communication path is a cable television RF communication path; and

the second communication path is a telephone line.

14. The method of claim 4, further including the step of maintaining a routine table for the second router, wherein responsive to determining a change of status of the first communication path the table is changed.

15. The method of claim 4, wherein the first communication path is a unidirectional path and wherein the second communication path is a bidirectional path.

16. An improved CATV head end apparatus for reliably providing a personal computer access to the Internet through a cable television path and a public switched telephone network path, said apparatus comprising:

a local area network (LAN);

a modem pool, said modem pool comprising a plurality of modems connected to the public switched telephone network path and to said LAN, wherein said modem pool maintains a first table of addresses;

a router connected to said LAN and to the Internet, wherein said router maintains a second table of addresses and routes data according to said second table; and

a CATV communication manager connected to said LAN, said communication manager formatting data and producing output, wherein said communication manager maintains a third table of addresses,

wherein the second table of addresses maintained by the router is changed responsive to a message received by the router through the LAN responsive to failure of the cable television path to the personal computer, and wherein the router routes data addressed to the personal computer to the modem pool responsive to the change of the second table maintained by the router.

17. The apparatus of claim 16, further comprising:

a plurality of modulators connected to said communication manager, said modulators digitally modulating the output from said communication manager; and

a combiner connected to said plurality of modulators, said combiner combining all output from said modulators and outputting said combined output through said cable television path;

and a network management server connected to said LAN, wherein said network management server maintains a fourth table of addresses,

wherein responsive to a message received by the modem pool through the public switched telephone network path responsive to failure of the cable television path to the personal computer, the first table of addresses maintained by the modem pool is changed and a message responsive to failure of the cable television path to the personal computer is transmitted to the router through the LAN.