| US 7,590,760 B1 | ||
| Hybrid interface synchronization method and driver-client model for high availability systems | ||
| Donald Banks, San Jose, Calif. (US); Vijay Savla, Acton, Mass. (US); Timothy Donahue, Natick, Mass. (US); Balachander Chandrasekaran, Milpitas, Calif. (US); and Denis Leclerc, Sterling, Mass. (US) | ||
| Assigned to Cisco Technology, Inc., San Jose, Calif. (US) | ||
| Filed on May 24, 2002, as Appl. No. 10/156,556. | ||
| Int. Cl. G06F 15/16 (2006.01); G06F 15/173 (2006.01); G06F 11/00 (2006.01) | ||
| U.S. Cl. 709—248 [709/223; 714/11] | 16 Claims |
| 1. In a high-availability network device that includes redundant route processors (RPs), where an RP communicates with line
cards, which provide interfaces over which traffic flows, through an interconnect, each RP having memory, where a first RP
is an Active RP that controls processing and a second RP is a Standby RP which takes over processing during a switchover,
where the line cards are accessible to both the Active and Standby RPs, and with an interconnect coupling the Active and Standby
RPs to facilitate interprocess communication, a method for interface synchronization of the interface states on the first
and second RPs so that applications that have been modified for high-availability (HA-aware applications) and non-modified
applications (HA-unaware applications) can be used on the same system, the method comprising:
maintaining an Active interface description block and real and shadow Standby interface description blocks, with an interface
description block storing state variables to associated with an interface on a line card, in the memories of the Active and
Standby RPs;
marking the state of the real interface description block of the Standby RP as down to indicate to HA-unaware applications
that the Standby RP is not communicating with line cards;
copying an Active interface description data block from Active RP memory to the shadow interface description block in Standby
RP memory to initialize the Standby shadow interface description data block;
synchronizing the Standby shadow interface description data block with Active interface description data block, subsequent
to initializing the standby interface description data block, whenever the Active interface description data block changes
by utilizing the interconnect to send a change to the Standby RP where it is written to the shadow copy in the interface description
data block on the Standby RP; and
during a switchover, copying the shadow interface description block of the Standby RP to the real interface description block
of the standby RP and notifying HA-unaware applications of a state change so that to HA-unaware applications it appears that
the line card interface has just become available.
|