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A Subscribe-Notify Mechanism in DHCP protocol to notify changes in DHCP Server

IP.com Disclosure Number: IPCOM000188701D
Original Publication Date: 2009-Oct-19
Included in the Prior Art Database: 2009-Oct-19
Document File: 4 page(s) / 221K

Publishing Venue

Motorola

Related People

Sridhar, Sriram: INVENTOR

Abstract

DHCP protocol is extended in a way such that every DHCPOFFER/DHCPREQUEST is treated as an implicit subscription to be notified of any changes that is done in the DHCP server. When a DHCP client has made the DHCPOFFER/DHCPREQUEST, it is guaranteed by the DHCP Server in DHCPACK response that it will be notified of any changes done in the DHCP server. When the DHCP server is re-provisioned with a new set of parameter values, say DNS IP address is changed, the DHCP server shall immediately notify all the DHCP clients via a unicast DHCPNOTIFY message. The clients update the re-provisioned parameters and there by avoid any call failures that involve DNS look up. With this implicit SUBCRIBE-NOTIFY method of client-server communication, any future changes done in DHCP server can be immediately notified to all the DHCP clients.

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A Subscribe-Notify Mechanism in DHCP protocol to notify changes in DHCP Server

 

By Author’s Sriram Sridhar,

Motorola, Inc.

Networks Business

 

ABSTRACT

DHCP protocol is extended in a way such that every DHCPOFFER/DHCPREQUEST is treated as an implicit subscription to be notified of any changes that is done in the DHCP server.

When a DHCP client has made the DHCPOFFER/DHCPREQUEST, it is guaranteed by the DHCP Server in DHCPACK response that it will be notified of any changes done in the DHCP server. When the DHCP server is re-provisioned with a new set of parameter values, say DNS IP address is changed, the DHCP server shall immediately notify all the DHCP clients via a unicast DHCPNOTIFY message.

The clients update the re-provisioned parameters and there by avoid any call failures that involve DNS look up. With this implicit SUBCRIBE-NOTIFY method of client-server communication, any future changes done in DHCP server can be immediately notified to all the DHCP clients.

PROBLEM

Network service provider had dynamically upgraded the DNS server IP address because of some network congestion in one of the DNS server. This information is updated in the DHCP server. But, there is no way for the DHCP server to inform the clients (ONT's) that the DNS server IP has changed.

ONT’s in the GPON (Gigabit Passive Optical Network) networks use SIP(Session Initiation Protocol) signaling over IP for communicating with the SBC (Session  Border Controller) and CS2K(Switch) and use DNS look up to resolve a fully qualified domain name (Switch domain name or URI (Uniform Resource Identifier)).

As a result of the change in DNS server IP’s, ONT’s do not have this new modified information and  report call failures because DNS look up failed and therefore they are not able to initiate calls made from the phones connected to their POTS lines.

This is a transient condition and this condition will remain on all the ONT’s until one of the following occurs:

  1. The ONT’s are forced to release their DHCP bindings and renew their lease with a new IP address and it gets the new DNS IP address in the DHCP ACK message.

 

  1. The ONT’s automatically renew their lease just before the lease expiry and it gets the new DNS IP address in the DHCP ACK message.

SOLUTION

DHCP protocol is extended in a way such that every DHCPOFFER/DHCPREQUEST is treated as an implicit subscription to be notified of any changes that is done in the DHCP server. 

When a DHCP client has made the DHCPOFFER/DHCPREQUEST, it is guaranteed by the DHCP Server in DHCPACK response that it will be notified of any changes done in the DHCP server.

When the DHCP server is re-provisioned with a new set of parameter values, say DNS IP address is changed, the DHCP server shall immediately notify all the DHCP clients via a unicast DHCPNOTIFY message.

The clients update the re-provisioned...