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Proactive and Deterministic Discovery of Access Router IP Addresses

IP.com Disclosure Number: IPCOM000246539D
Publication Date: 2016-Jun-16
Document File: 3 page(s) / 20K

Publishing Venue

The IP.com Prior Art Database

Related People

Srivatsa Kedilaya: INVENTOR

Abstract

MAC-Forced Forwarding (also referred to as Dynamic Proxy ARP) is deployed in access networks to ensure that the traffic is routed via an access router to enforce security and facilitate an accounting. The access router IP address needs to be dynamically detected as the switch implementing this feature is not aware of the upstream router IP address. The current mechanisms to detect the access router IP address have dependencies and limitations. We propose a solution to proactively and deterministically find the access router's IP address without these dependencies.

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Date: April 1, 2016

Proactive and Deterministic Discovery of Access Router IP Addresses

Authors et.al.:   Srivatsa Kedilaya

                                Dwarakadheesh Kodicherla

                                Arvind Mollin Kubendran

MAC-Forced Forwarding* (also referred to as Dynamic Proxy ARP) is deployed in access networks to ensure that the traffic is routed via an access router to enforce security and facilitate an accounting. The access router IP address needs to be dynamically detected as the switch implementing this feature is not aware of the upstream router IP address. The current mechanisms to detect the access router IP address have dependencies and limitations. We propose a solution to proactively and deterministically find the access router’s IP address without these dependencies.

Known mechanisms for determining router IP addresses

One of the current mechanisms is to snoop the DHCP ACK being sent to a downstream client and determine the access router IP address from option 3. Snooping a DHCP ACK has a dependency on any downstream client requesting for a lease, which might take a long time, since the lease time is generally in the order of a few days. This means until we are able to snoop DHCP ACK and learn access router IP address the ARP requests to clients and traffic between them will be dropped by the switch .

The other method is to statically configure the access router IP address for each access network. In this method the operator has to know the access router IP address before hand and configure it each time it changes, which is cumbersome and prone to errors.

How does the new solution work

The solution is to temporarily act as a DHCP client in the access network and request a lease. The DHCP ACK, which is obtained in this process, would have option 3 which would have the access router IP address for that network. We deterministically obtain the access router IP address without having to wait for a downstream client to request a lease, or even a dependency on such downstream client to obtain a lease via DHCP.

Also, this process ensures that we are able to determine the access router IP address in a lot less time after a power cycle of the switch or if it is deployed in the network at any instance of time. This method prevents the snooping process which will eventually increase the performance and avoid unnecessary efforts. It also removes the dependency on DHCP lease time.

Auto discovery of access router details for MAC-Forced Forwarding

MAC-Forced Fo...