Method of dynamically assigning a logical network address and a link address

• US 6,295,298 B1
• Filed: 03/11/1997
• Issued: 09/25/2001
• Est. Priority Date: 04/11/1997
• Status: Expired due to Term

• Current Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Sedacca, David A., Hrastar, Scott E.
• Primary Examiner(s): TON, DANG T
• Application Number:
  US08/832,714
• Time in Patent Office: 1,659 Days
• Field of Search: 370/352, 370/358, 370/389, 370/392, 370/409, 370/901, 370/902, 370/912, 370/401, 370/503, 370/509, 370/510, 370/535, 370/537, 370/461, 370/462, 370/431, 370/442, 370/451, 370/407, 370/254, 370/465, 370/466, 370/480, 395/200.01, 395/200.12, 395/200.15, 395/200.16, 375/222, 375/224, 348/469, 348/461, 348/441
• US Class Current: 370/409
• 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 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]
• CPC Class Codes: H04L 61/5061 Pools of addresses

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 ink conning 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. An address assignment method employed in a head end operating in a network which routes a plurality of packets to an RF (radio frequency) modem which is connected to said head end via a bidirectional link and an RF cable connection, the method having the steps of:

responding to an assignment request from said RF modem via said bidirectional link by obtaining a link address for said RF modem, wherein said RF cable connection has a plurality of channels multiplexed onto said RF cable connection so that a channel of said plurality of channels is separated from other said channels by frequency, wherein said channel of said plurality of channels has a plurality of frames multiplexed onto said channel so that a frame of said plurality of frames only uses said channel for a portion of time that said channel can be used, wherein said frame of said plurality of frames has a fixed number of packets, N, multiplexed into said frame so that an i^th packet of said fixed number of packets is always at a static, computably fixed bit position relative to a frame header at the start of said frame, and given that i is an integer between 0 and N+1 (0<

i<

N+1); and

returning an assigned link address to said RF modem via said bidirectional link.

2. The method of claim 1, wherein each said i^th packet has a packet payload and a packet header containing a link ID field populated with a first link ID value so that said i^th packet in a successive frame within said channel is capable of containing said packet header with a second Link ID value in the link ID field, said second link ID value being different from said first link ID value.

3. The method of claim 2, wherein said link address is used by said head end to prepare said packet payload for said RF cable connection that said RF modem should process, said link address further comprising:

a channel ID used to uniquely select said channel utilized in said RF cable connection by said head end and said RF modem;

a pipe ID used to uniquely select said static, computably fixed bit position within said frame where said RF modem should examine said i^th packet; and

a link ID value for said RF modem, said link ID value for said RF modem being used by said head end to populate the link ID field of said i^th packet when said head end prepares said packet payload for said RF modem, said link ID field of said i^th packet then containing said first link ID value, and said link ID value for said RF modem being used by said RF modem to identify whether said packet payload of said i^th packet within said frame should be processed by said RF modem when said link ID value for said RF modem matches said first link ID value in said link ID field of said i^th packet.

4. A method employed by a head end for dynamically assigning a link address to be used by an RF (radio frequency) modem, the method comprising steps of:

receiving from said RF modem an address assignment request for said link address, wherein said head end is coupled to said RF modem by an RF cable connection and a bidirectional link, said RF cable connection having a plurality of channels multiplexed onto said RF cable connection so that a channel of said plurality of channels is separated from other channels of said plurality of channels by frequency, said channel of said plurality of channels having a plurality of frames multiplexed onto said channel so that a frame of said plurality of frames only uses said channel for a portion of time that said channel can be used, said frame of said plurality of frames having a fixed number of packets, N, multiplexed into said frame so that an i^th packet of said fixed number of packets is always at a static, computably fixed bit position relative to a frame header at the start of said frame, and given that i is an integer between 0 and N+1 (0<

i<

N+1), said i^th packet having a packet payload and a packet header containing a link ID field populated with a first link ID value so that said i^th packet in a successive frame within said channel is capable of containing said packet header with a second Link ID value in the link ID field, said second link ID value being different from said first link ID value, said receiving step comprising the step of receiving said address assignment request over said bidirectional link; and

responding to said address assignment request from said RF modem by sending information comprising said link address, said responding step comprising the step of transmitting information comprising said link address over said bidirectional link.

5. The method of claim 4, wherein said link address is used by said head end to prepare said packet payload for said RF cable connection that said RF modem should process, said link address further comprising:

a channel ID used to uniquely select said channel utilized in said RF cable connection by said head end and said RF modem;

a pipe ID used to uniquely select said static, computably fixed bit position within said frame where said RF modem should examine said i^th packet; and

a link ID value for said RF modem, said link ID value for said RF modem being used by said head end to populate the link ID field of said i^th packet when said head end prepares said packet payload for said RF modem, said link ID field of said i^th packet then containing said first link ID value, and said link ID value for said RF modem being used by said RF modem to identify whether said packet payload of said i^th packet within said frame should be processed by said RF modem when said link ID value for said RF modem matches said first link ID value in said link ID field of said i^th packet.

6. A system for dynamically assigning a link address comprising:

a head end; and

an RF modem connected to said head end via an RF cable connection and a bidirectional link, said RF cable having a plurality of channels multiplexed onto said RF cable connection so that each channel of said plurality of channels is separated from other channels of said plurality of channels by frequency, said channel of said plurality of channels having a plurality of frames multiplexed onto said channel so that each frame of said plurality of frames only uses said channel for a portion of time that said channel can be used, said frame of said plurality of franes having a fixed number of packets, N, multiplexed into said frame so that an i^th packet of said fixed number of packets is always at a static, computably fixed bit position relative to a frame header at the start of said frame, and given that i is an integer between 0 and N+1(0<

i<

N+1), said head end configured to receive a request from said RF modem over said bidirectional link for an assignment of said link address, said head end further configured to respond to said request by sending said assignment of said link address over said bidirectional link to said RF modem.

7. The system of claim 6, wherein each said i^th packet has a packet payload and a packet header containing a link ID field populated with a first link ID value so that said i^th packet in a successive frame within said channel is capable of containing said packet header with a second Link ID value in the link ID field, said second link ID value being different from said first link ID value.

8. The system of claim 7, wherein said link address is used by said head end to prepare said packet payload for said RF cable connection that said RF modem should process, said link address further comprising:

a channel ID used to uniquely select said channel utilized in said RF cable connection by said head end and said RF modem;

a pipe ID used to uniquely select said static, computably fixed bit position within said frame where said RF modem should examine said i^th packet; and

a link ID value for said RF modem, said link ID value for said RF modem being used by said head end to populate the link ID field of said i^th packet when said head end prepares said packet payload for said RF modem, said link ID field of said i^th packet then containing said first link ID value, and said link ID value for said RF modem being used by said RF modem to identify whether said packet payload of said i^th packet within said frame should be processed by said RF modem when said link ID value for said RF modem matches said first link ID value in said link ID field of said i^th packet.

9. A method employed by a head end for dynamically assigning at least one logical network address to be used by at least one host, the method comprising steps of:

receiving from said RF modem an address assignment request for said at least one logical network address, wherein said head end is coupled to an RF modem by an RF cable connection and a bidirectional link, said RF cable connection having a plurality of channels multiplexed onto said RF cable connection so that a channel of said plurality of channels is separated from other channels of said plurality of channels by frequency, said channel of said plurality of channels having a plurality of frames multiplexed onto said channel so that a flame of said plurality of frames only uses said channel for a portion of time that said channel can be used, said frame of said plurality of frames having a fixed number of packets, N, multiplexed into said frame so that an i^th packet of said fixed number of packets is always at a static, computably fixed bit position relative to a frame header at the start of said frame, and given that i is an integer between 0 and N+1 (0<

i<

N+1);

responding to said address assignment request from said RF modem by sending, over said bidirectional link, information comprising said at least one logical network address;

determining that a session with said RF modem has ended; and

releasing said at least one logical network address assigned to said at least one host so that said at least one logical network address is reclaimed by said head end.

10. The method of claim 9, wherein each said i^th packet has a packet payload and a packet header containing a link ID field populated with a first link ID value so that said i^th packet in a successive frame within said channel is capable of containing said packet header with a second Link ID value in the link ID field, said second link ID value being different from said first link ID value.

11. The method of claim 10, wherein said link address is used by said head end to prepare said packet payload for said RF cable connection that said RF modem should process, said link address further comprising:

a channel ID used to uniquely select said channel utilized in said RF cable connection by said head end and said RF modem;

a pipe ID used to uniquely select said static, computably fixed bit position within said frame where said RF modem should examine said i^th packet; and

a link ID value for said RF modem, said link ID value for said RF modem being used by said head end to populate the link ID field of said i^th packet when said head end prepares said packet payload for said RF modem, said link ID field of said i^th packet then containing said first link ID value, and said link ID value for said RF modem being used by said RF modem to identify whether said packet payload of said i^th packet within said frame should be processed by said RF modem when said link ID value for said RF modem matches said first link ID value in said link ID field of said i^th packet.