International Business Machines Corporation

Edward Glen Britton

Jeffrey Douglas Haggar

Barton Clark Vashaw

Maurice Isrel

Jon Anthony Bell

Michael G Fitzpatrick

Andrew Henry Richter

Lap Thiet Huynh

Arthur James Stagg

Bala Rajaraman

Wesley McMillan Devine

Thomas Donald Moore

David Bruce Lindquist

Roy Frank Brabson

Karen Marie Tracey

David Paul Brooks

Rodney A Bell

Alfred Bundgaard Christensen

Methods, systems, and computer program products for dynamically modifying an application program's behavior in response to changing environmental conditions (such as network changes, system changes, and so forth). The application may solicit such information, and/or may receive unsolicited environmental change notifications. In response to a change notification, the application may take one or more of the following approaches to adapt to the changing conditions: (1) alter its execution; (2) modify its use of, or control of, other cooperating application; and (3) modify the selection of application execution threads. (An application might also decide to make no changes in its behavior.)

Dynamic modification of application behavior in response to changing environmental conditions

A value-based caching system and method. A value based cache method can include partitioning a cache into different value-based partitions. Data to be stored in the cache can be valued and the valued data can be cached in individual ones of the value-based partitions. Subsequently, cache entries can be evicted from the value-based partitions. Finally, the caching and evicting can be managed according to the valuing step. In this regard, the cache and eviction management step can ensure greater cache responsiveness for data having a greater value relative to other valued data.

Value based caching

The invention ensures that a single and consistent reply is made to ARP request in a system of connected IP networks. When an adapter (A) becomes active, the owning host sends an ARP advertisement into the network over the adapter. If the advertisement is also received at the sending host over a different adapter B, then the host knows that adapter B is on in the same physical network as adapter A and B can be designated as a backup adapter for A and A can be designated as backup adapter for B. If adapter A fails or becomes inactive, the host resets the backup adapter field for any adapter it owns for which A is marked as the backup adapter. If a backup adapter B has been designated for A, the host also sends an ARP advertisement associating MAC-B with IP-A. This allows network connections originally served via adapter A to continue non-disruptively over adapter B and it also provides access to the host for subsequent new connections. When adapter A becomes active again, the host sends a gratuitous ARP advertisement that maps IP-A to MAC-A. This allows adapter A to re-assume responsibility for responding to ARP requests for IP-A.

Method and apparatus for generating replies to address resolution protocol requests

The invention ensures that a single and consistent reply is made to ARP request in a system of connected IP networks. In each host, the first adapter A to become active is designated as being in an arbitrary first physical network (PNET ). For each subsequent adapter B to become active on a host, the host sends a packet over one of the adapters (A) of each network already known to the host with a hop count of one. If the packet is received over adapter B, it is known that adapters A and B are in the same physical network. If this occurs, adapter B is marked as being in the same network PNET as adapter A. If the packet is not received over adapter B then B is in a different physical network as A. In this event, adapter B is marked as being in a new network PNET . When adapter A becomes inactive, if there are other active adapters in the physical network to which A belongs, then one of the remaining adapters B in that physical network is designated to have the responsibility for replying to ARP requests for A. A gratuitous ARP advertisement is transmitted into the network mapping IP-A with MAC-B. When adapter A again becomes active, adapter A will re-assume ownership of ARP replies for IP address A.

The invention ensures that a single and consistent reply is made to an ARP request in a system of connected IP networks. When an adapter becomes active, the relative network on which it resides is determined by transmitting control packets over it and all other adapters known to the host and observing if and where responses are returned to the adapters. One adapter on a network is designated as active. If the same network contains other adapters, they are marked as standby adapters for the purpose of responding to ARP messages. Special processing is provided for offload adapters that perform there own ARP processing.

Method and apparatus for generating replies to address resolution protocol requests by offload adapters

Method and apparatus for generating replies to address resolution protocol requests for virtual IP addresses

The invention ensures that a single and consistent reply is made to ARP requests in a system of connected IP networks in which each host can contain combinations of host adapters, offload adapters and virtual IP addresses.

Method and apparatus for returning packet acknowledgements from a packet receiving node to a packet sending node of a packet network. During a predefined initial startup phase of a packet connection between the sending and receiving nodes, an acknowledgement is returned to the sending node for every group of X packets received from the sending node. After the expiration of the initial startup phase, an acknowledgement is returned for every W-N packets received from the sending node. W represents the maximum number of packets that can be in transit on the connection at any given time, N is an integer less than W. If packet congestion occurs, the algorithm reverts to returning an acknowledgement for every group of X packets.

Method and apparatus for scheduling packet acknowledgements

The present invention utilizes Virtual Internet Protocol Addressing (VIPA) to enable a host computer to efficiently route TCP/IP traffic across multiple physical links. This is accomplished by associating different applications or application sets with different virtual IP addresses. The virtual IP addresses may be associated with different physical adapters. Since many applications send similar data repeatedly, categorizing application sets and associating them with different physical adapters allows high volume applications to be associated with one adapter while lower volume, interactive data is associated with another adapter.

Session traffic splitting using virtual internet protocol addresses

A method of allowing TCP/IP resources to be rerouted to another active link connected to the same resources in a timely manner. This method comprises sending a Routing Information Protocol (RIP) update to the router by sending information to the other resource specifying a metric that indicates that the desired network is unreachable; this RIP update is sent with the IP source address set as if it had been transmitted across the failed link. This causes the route to be updated to indicate that the failing link is no longer active and indicate an alternate route as the preferred means of reaching the resource.

Methods and systems for actively updating routing in TCP/IP connections

In a telecommunications system containing a host computer and multiple real connections to the telecommunications network, an apparatus, method and system for allowing transmission to the host computer to reroute dynamically through the multiple available real connections to the host without requiring changes to the devices connecting to the host.

Virtual internet protocol (IP) addressing

In a telecommunications system containing more than one host computer and multiple real connections to the telecommunications network, an apparatus, method and system for allowing transmission to the dynamic reassignment of sessions from a failing host to an alternate or backup host computer without requiring changes to the devices or addresses of devices connecting to the host.

Host identity takeover using virtual internet protocol (IP) addressing

A process and apparatus for detecting the occurrence of an event threshold and performing some type of action in response to the detection. The disclosed use of the invention is for managing communication connections in a network. An event counter, a sliding event threshold counter and a sliding interval counter are initialized to prescribed initial states at the start of counter management. At the expiration of an interval specified by the contents of the sliding interval counter, the sliding interval counter is incremented by an offset time value, and the sliding event threshold counter is updated by the sum of an offset event value and the event counter. The event counter is incremented on each occurrence of an event to be counted. Each time the event counter exceeds a threshold established by the sliding threshold event counter, the sliding threshold event counter is incremented by the contents of the offset event value, and the sliding interval counter is updated to the sum of the offset time value and the present time. Thus, all values of interest are maintained by a combination of keeping an absolute count of the events, and by 'sliding' the contents of two counters, one of which is used to measure successive time intervals and the other to set a new threshold for each successive interval based on the offset threshold and the absolute event count at the beginning of the interval.

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Chapel Hill, NC, United States of America

Edward Glen Britton