Self-managed mediated information flow

• US 20050044268A1
• Filed: 07/30/2004
• Published: 02/24/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: Cloudsoft Corp. Ltd.
• Original Assignee: Enigmatec Corporation
• Inventors: West, Andrew Martin, Johnston-Watt, Duncan, Connor, Richard, Sheehan, Dean Alan, Dearle, Alan
• Granted Patent: US 9,525,566 B2
• Time in Patent Office: Days
• US Class Current: 709/238
• CPC Class Codes: H04L 41/0663 Performing the actions predefined by failover planning, e.g. switching to standby network elements
• CPC Class Codes: H04L 41/0668 by dynamic selection of recovery network elements, e.g. replacement by the most appropriate element after failure
• CPC Class Codes: H04L 41/08 Configuration management of networks or network elements address allocation H04L61/50
• CPC Class Codes: H04L 41/0803 Configuration setting
• CPC Class Codes: H04L 41/0816 the condition being an adaptation, e.g. in response to network events
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies
• CPC Class Codes: H04L 43/0811 by checking connectivity
• CPC Class Codes: H04L 51/063 Content adaptation, e.g. replacement of unsuitable content
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/101 based on network conditions
• CPC Class Codes: H04L 67/1012 based on compliance of requirements or conditions with available server resources
• CPC Class Codes: H04L 67/1014 based on the content of a request
• CPC Class Codes: H04L 67/1023 based on a hash applied to IP addresses or costs
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer
• CPC Class Codes: H04L 67/288 Distributed intermediate devices, i.e. intermediate devices for interaction with other intermediate devices on the same level
• CPC Class Codes: H04L 67/55 Push-based network services
• CPC Class Codes: H04L 67/563 Data redirection of data network streams
• CPC Class Codes: H04L 67/63 Routing a service request depending on the request content or context

Abstract

There is provided a method for mediating the flow of messages in a computer network having a mediation architecture that includes a plurality of logical nodes arranged in a logical mediation cycle. The method provides algorithms for: handing mediation tasks over between mediator nodes; reconfiguring the logical topology of the mediation architecture in response to a change request while maintaining system invariants; and refining the structure of the mediation architecture by adding whole subnetworks in place of single nodes. The method also addresses failure detection and recovery.

Claims

1. A method for mediating the flow of messages in a computer network, wherein the computer network has a mediation network that includes:

at least one local point of presence (LPP) module for interfacing between the mediation network and client programs;

at least one mediator (M) module for hosting a mediation task;

at least one mediator router (MR) module for analyzing the content of incoming messages, each MR module routing the incoming messages to a predetermined M module in dependence upon said content; and

at least one transmission proxy (TP) module for forwarding messages to at least one of said LPP modules,

wherein, in the method, incoming messages to the mediation network are propagated along a mediation cycle that comprises the steps of;

an LPP module addressing incoming messages to a respective one of said at least one mediator router (MR) modules;

at said addressed MR module, analyzing the content of incoming messages and routing said messages to a predetermined mediator module in dependence upon said analyzed content;

at said predetermined mediator module, applying the mediation task to said analyzed messages and directing mediated messages to a respective one of said TP modules; and

at said TP module that receives said mediated messages, forwarding said mediated messages to at least one of said LPP modules.

2. A method as claimed in claim 1, wherein the incoming messages to the mediation network belong to one of the group of message types including:

new information, which emanates from a process acting as an information source;

queries about state of nodes in the mediation network, which require a reply; and

expressions of interest, which require ongoing replies whenever pertinent new information is received by the mediation network.

3. A method as claimed in claim 1, further comprising inducing a change in internal operation of the mediation network by directing a control message as an incoming message along the mediation cycle.

4. A method as claimed in claim 3, wherein the change in internal operation is a handover of a mediation task between a donor mediator module and a recipient mediator module,

wherein the control message is a mediator handover message, the content of the mediator handover message describing the reallocation of content having a predetermined content tag from the donor mediator module to the recipient mediator module, where the donor mediator module is currently registered as handling said content, and

wherein the direction of the mediator handover message comprises:

from a predetermined LPP module, sending the mediator handover message to a respective associated MR module;

at the associated MR module, reading said content tag and forwarding the message to the donor mediator module; and

upon receipt of the mediator handover message, the donor mediator module;

changing mediator node state;

sending a MEDIATOR_HANDOVER message to the recipient mediator module, the MEDIATOR_HANDOVER message containing the content of the mediator handover message;

sending a MEDIATOR_CHANGED message to an associated TP module; and

then changing state in order to forward messages containing the content tag to the recipient mediator module.

5. A method as claimed in claim 4, further comprising:

the TP module forwarding the MEDIATOR_CHANGED message to at least one LPP module;

the recipient mediator module generating a NEW_MEDIATOR_ACTIVE message, the NEW_MEDIATOR_ACTIVE message having a payload corresponding to the reallocated content, and broadcasting said NEW_MEDIATOR_ACTIVE message to all TP modules associated therewith; and

the LPP module buffering all incoming messages between receipt of the MEDIATOR_CHANGED message and receipt of the NEW_MEDIATOR_ACTIVE message.

6. A method as claimed in claim 5, further comprising:

the LPP module then forwarding the NEW_MEDIATOR_ACTIVE message to the associated MR module; and

whenever a MR module receives a NEW_MEDIATOR_ACTIVE message, updating a routing table for said MR module to cause future content matching the payload of the NEW_MEDIATOR_ACTIVE message to be sent to the recipient mediator module rather than the donor mediator module;

informing the donor mediator module that the routing table has been updated, the donor mediator module thereafter ceasing to forward messages once all MR modules have been informed that the recipient mediator module is now the mediator module for the reallocated content.

7. A method as claimed in claim 3, wherein the change in internal operation is a reconfiguration of the logical topology of the mediation network and wherein the control message is one or more reconfiguration messages.

8. A method as claimed in claim 7, wherein the reconfiguration of the logical topology includes generation of a causal barrier to ensure that messages passing through the mediation network before the reconfiguration are delivered in advance of messages passing through the mediation network after the reconfiguration.

9. A method claimed in claim 8, wherein the step of generating the causal barrier includes:

circulating said one or more reconfiguration messages around the mediation cycle; and

ensuring that each module in the cycle has been sufficiently notified of the reconfiguration.

10. A method as claimed in claim 9, wherein the reconfiguration of the logical topology of the mediation architecture is the insertion of an additional local point of presence (LPP) node, and said one or more reconfiguration messages include a new_LPP message that uniquely identifies the additional LPP node, the insertion including:

in a predetermined additional LPP module at the additional LPP node, generating the new_LPP message and sending the new_LPP message to a corresponding MR module at an MR node;

in the corresponding MR module, receiving the new_LPP message, updating a reference count for the MR node, and propagating the new_LPP message to all mediator modules in the architecture;

in each mediator module, receiving the new_LPP message, and transmitting the new_LPP message to a respective, corresponding TP module at a TP node, each TP node having an associated credit balance;

in each of the corresponding TP modules, receiving the new_LPP message and sending a respective, extended new_LPP message to the additional LPP module, the extended new_LPP message including the respective associated credit balance;

in the additional LPP module, receiving the extended new_LPP messages, thereby completing the circulation of the new_LPP message; and

in the additional LPP module, summing the credit balances, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

11. A method as claimed in claim 10, wherein the reconfiguration of the logical topology of the mediation architecture includes the further insertion of an additional mediator router (MR) node, and wherein said one or more reconfiguration messages further include a new_MR message that uniquely identifies the additional MR node, the further insertion including:

the additional LPP sending a new_MR message to a corresponding MR module at an MR node having a corresponding credit balance;

the corresponding MR module responding to the new_MR message by sending a new_MR_route_table message, which includes;

address information for the additional MR node, the address of the additional LPP node, routing information and a fraction of the corresponding credit balance;

the corresponding MR module then forwarding the new_MR_route_table message to an arbitrary mediator module;

the arbitrary mediator module passing the new_MR_route_table message to the additional LPP module;

the additional LPP module then passing the routing map to the additional MR module; and

in the additional MR module, using the contents of the new_MR_route_table message to initialise a new credit balance and routing maps.

12. A method as claimed in claim 11, wherein the reconfiguration further includes, changing the MR module that the additional LPP module addresses, to the additional MR module, wherein the additional MR module sends a MR_initialised( ) message to the additional LPP module upon receipt of the new_MR_route_table message and wherein the additional LPP module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial MR modules respectively.

13. A method as claimed in claim 9, wherein the reconfiguration of the logical topology of the mediation architecture is the insertion of an additional mediator (M) node, and said one or more reconfiguration messages include a new_M message that uniquely identifies the additional mediator node, the insertion including:

a predetermined additional mediator module generating the new_M message and sending the new_M message to a corresponding TP module at a TP node;

in the corresponding TP module, receiving the new_M message, updating a reference count for the TP node, and propagating the new_M message to all LPP modules in the architecture;

in each LPP module, receiving the new_M message, transmitting the new_M message to a respective, corresponding MR module at an MR node, each MR node having an associated credit balance;

in each of the corresponding MR modules, receiving the new_M message and sending a respective, extended new_M message to the additional mediator module, the extended new_M message including the respective associated credit balance; and

in the additional mediator module, receiving the extended new_M messages, thereby completing the circulation of the new_M message; and

in the additional mediator module, summing the credit balances, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

14. A method as claimed in claim 13, wherein the reconfiguration of the logical topology of the mediation architecture includes the further insertion of an additional transmission proxy (TP) node, and wherein said one or more reconfiguration messages further include a new_TP message that uniquely identifies the additional TP node, the further insertion including:

the additional mediator module receiving the new_TP message;

the additional mediator module adding the address of the additional mediator node to the new_TP message and forwarding the new_TP message to a corresponding TP module at an TP node having a corresponding credit balance;

the corresponding TP module responding to the new_TP message by generating an extended new_TP message, which includes;

address information for the additional TP node, the address of the additional mediator node, a list of LPPs and a fraction of the corresponding credit balance;

the corresponding TP module then forwarding the new_TP message to an arbitrary LPP module;

the arbitrary LPP module then passing a new routing map message to the additional TP module;

the additional TP module then passing the routing map to the additional MR module; and

the additional TP module using the contents of the new routing map message to initialise a new corresponding credit balance and a list of LPP modules.

15. A method as claimed in claim 14, wherein the reconfiguration further includes:

changing the TP module that the additional mediator module addresses to the additional TP module, wherein the additional TP module sends a TP_initialised( ) message to the additional mediator module upon receipt of the new routing map message and wherein the additional mediator module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial TP modules respectively.

16. A method as claimed in claim 3, wherein the computer network further includes a failure detection node that is in communication with each node in the mediation network, the method further comprising:

at the failure detection node, providing a failure detection module;

at each node of the mediation network, providing a failure reporting module;

whenever an incoming or outgoing communication link between nodes fails, each of said failure reporting modules reporting information relating to the failing communication link to said failure detection module; and

said failure detection module determining whether said failing link is indicative of a failing node.

17. A method as claimed in claim 16, further comprising, where the failure detection module determines that said failing link is indicative of a failing node:

creating a new node of the same type as the failing node;

imbuing the new node with information relating to the failing node'"'"'s internal state and immediate neighbourhood topology; and

reconfiguring the network to use the new node in preference to the failing node.

18. A method as claimed in claim 1, further comprising generating a message log of all incoming messages received by said predetermined mediator module.

19. A method as claimed in claim 18, wherein the mediation task applied to said analyzed messages at said predetermined mediator module includes generating the message log.

20. A method as claimed in claim 18, wherein the computer network further includes an external application, the method further comprising:

generating the message log in said external application.

21. A method as claimed in claim 3, wherein the change in internal operation is a structural refinement of the logical topology of the mediation architecture and wherein the control message is one or more refinement messages.

22. A method as claimed in claim 21, wherein a subnetwork is inserted in place of a single node during the step of structural refinement.

23. A mediation network for mediating the flow of messages in a computer network, wherein the mediation network includes:

at least one local point of presence (LPP) module for interfacing between the mediation network and client programs;

at least one mediator (M) module for hosting a mediation task;

at least one mediator router (MR) module for analyzing the content of incoming messages, each MR module routing the incoming messages to an associated, predetermined M module in dependence upon said content; and

at least one transmission proxy (TP) module for forwarding messages to at least one of said LPP modules,

wherein the mediation network couples messages along a unidirectional mediation cycle in which;

LPP modules address MR modules;

MR modules in turn address M modules;

M modules in turn address TP modules; and

TP modules in turn address LPP modules.

24. A mediation network as claimed in claim 23, wherein the incoming messages to the mediation network belong to one of the group of message types including:

new information, which emanates from a process acting as an information source;

queries about state of nodes in the mediation network, which require a reply; and

expressions of interest, which require ongoing replies whenever pertinent new information is received by the mediation network.

25. A mediation network as claimed in claim 23, further comprising a control mechanism that induces a change in internal operation of the mediation network by directing a control message as an incoming message along the mediation cycle.

26. A mediation network as claimed in claim 25, wherein the control mechanism for inducing the change in internal operation is a handover mechanism, which redistributes a mediation requirement between a donor mediator node and a recipient mediator node,

wherein the control message is a mediator handover message, the content of the mediator handover message describing the reallocation of content having a predetermined content tag from the donor mediator node to the recipient mediator node, where the donor mediator node is currently registered as handling said content, and

wherein the mediator handover message is directed by:

sending the mediator handover message from a predetermined LPP module to a respective associated MR module;

reading said content tag at the associated MR module and forwarding the message to the donor mediator module; and

upon receipt of the mediator handover message, the donor mediator node;

changing mediator node state;

sending a MEDIATOR_HANDOVER message to the recipient mediator module, the MEDIATOR_HANDOVER message containing the content of the mediator handover message;

sending a MEDIATOR_CHANGED message to an associated TP module; and

then changing state in order to forward messages containing the content tag to the recipient mediator module.

27. A mediation network as claimed in claim 26, further comprising:

the TP node forwarding the MEDIATOR_CHANGED message to at least one LPP module;

the recipient mediator module generating a NEW_MEDIATOR_ACTIVE message, the NEW_MEDIATOR_ACTIVE message having a payload corresponding to the reallocated content, and broadcasting said NEW_MEDIATOR_ACTIVE message to all TP modules associated therewith; and

the LPP module buffering all incoming messages between receipt of the MEDIATOR_CHANGED message and receipt of the NEW_MEDIATOR_ACTIVE message.

28. A mediation network as claimed in claim 27, wherein

the LPP module then forwards the NEW_MEDIATOR_ACTIVE message to the associated MR module;

and

wherein, whenever a MR module receives a NEW_MEDIATOR_ACTIVE message, said MR module updates a routing table for said MR module to cause future content matching the payload of the NEW_MEDIATOR_ACTIVE message to be sent to the recipient mediator module rather than the donor mediator module;

informing the donor mediator module that the routing table has been updated, the donor mediator module thereafter ceasing to forward messages once all MR modules have been informed that the recipient mediator module is now the mediator module for the reallocated content.

29. A mediation network as claimed in claim 25, wherein the control mechanism for inducing the change in internal operation is a reconfiguration mechanism and wherein the control message is one or more reconfiguration messages.

30. A mediation network as claimed in claim 29, wherein the reconfiguration mechanism generates a causal barrier to ensure that messages passing through the mediation network before the reconfiguration are delivered in advance of messages passing through the mediation network after the reconfiguration.

31. A mediation network claimed in claim 30, wherein the generation of the causal barrier includes circulating said one or more reconfiguration messages around the mediation cycle, and ensuring that each module in the cycle has been sufficiently notified of the reconfiguration.

32. A mediation network as claimed in claim 31, wherein the reconfiguration mechanism inserts an additional local point of presence (LPP) node into the logical topology of the mediation network and said one or more reconfiguration messages include a new_LPP message that uniquely identifies the additional LPP node, the reconfiguration mechanism including:

means for generating a new_LPP message that uniquely identifies the additional LPP node, and for sending the new_LPP message to a corresponding MR module at an MR node, said generating and sending means being provided in a predetermined additional LPP module;

means for receiving the new LPP message, for updating a reference count in the MR node, and propagating the new_LPP message to all mediator modules in the mediation network, said receiving, updating and propagating means being provided in the corresponding MR module;

means for receiving the new_LPP message and for transmitting the new_LPP message to a respective, corresponding TP module at a TP node, each TP node having an associated credit balance, said receiving and transmitting means being provided in each mediator module;

means for receiving the new_LPP message and sending a respective, extended new_LPP message to the additional LPP module, the extended new_LPP message including the respective associated credit balance, said receiving and sending means being provided in each of the corresponding TP modules;

means for receiving the extended new_LPP messages and thereby completing the circulation of the new_LPP message, said receiving means being provided in the additional LPP module; and

means for summing the credit balances, said summing means being provided in the additional LPP module, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

33. A mediation network as claimed in claim 32, wherein the reconfiguration mechanism further includes a MR insertion mechanism for inserting an additional mediator router (MR) node, and wherein said one or more reconfiguration messages further include a new_MR message that uniquely identifies the additional MR node, the MR insertion mechanism including:

means for sending a new_MR message to a corresponding MR module at an MR node having a corresponding credit balance, said sending means being provided in the additional LPP module;

means for receiving the new_MR message and for sending a new_MR_route_table message, said receiving and sending means being provided in the corresponding MR module, wherein the new_MR_route_table message includes;

address information for the additional MR node, the address of the additional LPP node, routing information and a fraction of the corresponding credit balance;

means for forwarding the new_MR_route_table message to an arbitrary mediator module, said forwarding means being provided in the corresponding MR module;

means for passing the new_MR_route_table message to the additional LPP module, said passing means being provided in the arbitrary mediator module;

further means for passing the routing map to the additional MR module, said further passing means being provided in the additional LPP module; and

initialising means for using the contents of the new_MR_route_table message to initialise a new credit balance and routing maps, said initialising means being provided in the additional MR module.

34. A mediation network as claimed in claim 33, wherein the reconfiguration mechanism further includes means for changing the MR module that the additional LPP addresses to the additional MR module;

wherein the additional MR module sends a MR_initialised( ) message to the additional LPP module upon receipt of the new_MR_route_table message and wherein the additional LPP module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial MR modules respectively.

35. A mediation network as claimed in claim 31, wherein the reconfiguration mechanism inserts an additional mediator (M) node into the logical topology of the mediation network and said one or more reconfiguration messages include a new_M message that uniquely identifies the additional M node, the reconfiguration mechanism including:

means for generating the new_M message and for sending the new_M message to a corresponding TP module at a TP node, said generating and sending means being provided in a predetermined additional mediator module;

means for receiving the new_M message, updating a reference count for the TP node, and propagating the new_M message to all LPP in the architecture, said receiving, updating and propagating means being provided in the corresponding TP module;

means for receiving the new_M message, and for transmitting the new_M message to a respective, corresponding MR module at an MR node, each MR node having an associated credit balance, said receiving and transmitting means being provided in each LPP module;

means for receiving the new M message and sending a respective, extended new_M message to the additional mediator module, the extended new_M message including the respective associated credit balance, said receiving and sending means being provided in each of the corresponding MR modules;

means for receiving the extended new_M messages and thereby completing the circulation of the new_M message, said receiving means being provided in the additional M module; and

means for summing the credit balances, said summing means being provided in the additional M module, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

36. A mediation network as claimed in claim 35, wherein the reconfiguration mechanism further includes a TP insertion mechanism for inserting an additional transmission proxy (TP) node, and wherein said one or more reconfiguration messages further include a new_TP message that uniquely identifies the additional TP node, the TP insertion mechanism including:

means for receiving a new_TP message that includes the address of the additional TP, said receiving means being provided in the additional mediator module;

means for adding the address of the additional mediator node to the new_TP message and forwarding the new_TP message to a corresponding TP module at a TP node having a corresponding credit balance, said adding and forwarding means being provided in the additional mediator module;

means for receiving the new_TP message and generating an extended new_TP message, which includes;

address information for the additional TP node, the address of the additional mediator node, a list of LPP nodes and a fraction of the corresponding credit balance, said receiving and generating means being provided in the corresponding TP module;

means for forwarding the new_TP message to an arbitrary LPP module, said forwarding means being provided in the corresponding TP module;

means for passing a new routing map message to the additional TP module, whose address is in the new routing map message, said passing means being provided in the corresponding TP module;

further means for passing the routing map to the additional MR module, said further passing means being provided in the additional TP module; and

initialising means for using the contents of the new routing map message to initialise a credit balance and a list of LPP nodes, said initialising means being provided in the additional TP module.

37. A mediation network as claimed in claim 36, wherein the reconfiguration mechanism further includes means for, changing the TP module that the additional mediator addresses to the additional TP module;

wherein the additional TP module sends a TP_initialised( ) message to the additional mediator module upon receipt of the new routing map message and wherein the additional mediator module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial TP modules respectively.

38. A mediation network as claimed in claim 23, wherein the computer network further includes a failure detection node that is in communication with each node in the mediation network, the failure detection node being provided with a failure detection module, and each node of the mediation network being provided with a failure reporting module;

wherein, whenever an incoming or outgoing communication link between nodes fails, each of said failure reporting modules reports information relating to the failing communication link to said failure detection module; and

wherein said failure detection module determines whether said failing link is indicative of a failing node.

39. A mediation network as claimed in claim 38, further comprising a failure handling mechanism, whenever the failure detection module determines that said failing link is indicative of a failing node, the failure handling mechanism:

creates a new node of the same type as the failing node;

imbues the new node with information relating to the failing node'"'"'s internal state and immediate neighbourhood topology; and

reconfigures the network to use the new node in preference to the failing node.

40. A mediation network as claimed in claim 23, further comprising means for generating a message log of all incoming messages received by said predetermined mediator module.

41. A mediation network as claimed in claim 40, wherein the mediation task applied to said analyzed messages at said predetermined mediator module includes generating the message log.

42. A mediation network as claimed in claim 40, wherein the computer network further includes an external application that generates the message log, the mediation network further comprising:

means for receiving the message log generated in said external application.

43. A mediation network as claimed in claim 23, wherein the change in internal operation is a structural refinement of the logical topology of the mediation network and wherein the control message is one or more refinement messages.

44. A mediation network as claimed in claim 43, wherein a subnetwork is inserted in place of a single node during the step of structural refinement.

45. A computer program product for mediating the flow of messages in a computer network, the computer program product including executable instructions for providing a mediation network having:

at least one local point of presence (LPP) module for interfacing between the mediation network and client programs;

at least one mediator (M) module for hosting a mediation task;

at least one mediator router (MR) module for analyzing the content of incoming messages, each MR module routing the incoming messages to a predetermined M module in dependence upon said content; and

at least one transmission proxy (TP) module for forwarding messages to at least one of said LPP modules,

wherein, when the instructions are executed, incoming messages to the mediation network are propagated along a mediation cycle that comprises the steps of;

an LPP module addressing incoming messages to a respective one of said at least one mediator router (MR) modules;

at said addressed MR module, analyzing the content of incoming messages and routing said messages to a predetermined mediator module in dependence upon said analyzed content;

at said predetermined mediator module, applying the mediation task to said analyzed messages and directing mediated messages to a respective one of said TP modules; and

at said TP module that receives said mediated messages, forwarding said mediated messages to at least one of said LPP modules.

46. A computer program product as claimed in claim 45, wherein the incoming messages to the mediation network belong to one of the group of message types including:

new information, which emanates from a process acting as an information source;

queries about state of nodes in the mediation network, which require a reply; and

expressions of interest, which require ongoing replies whenever pertinent new information is received by the mediation network.

47. A computer program product as claimed in claim 45, further comprising inducing a change in internal operation of the mediation network by directing a control message as an incoming message along the mediation cycle.

48. A computer program product as claimed in claim 47, wherein the change in internal operation is a handover of a mediation task between a donor mediator module and a recipient mediator module,

wherein the control message is a mediator handover message, the content of the mediator handover message describing the reallocation of content having a predetermined content tag from the donor mediator module to the recipient mediator module, where the donor mediator module is currently registered as handling said content, and

wherein the direction of the mediator handover message comprises:

from a predetermined LPP module, sending the mediator handover message to a respective associated MR module;

at the associated MR module, reading said content tag and forwarding the message to the donor mediator module; and

upon receipt of the mediator handover message, the donor mediator module;

changing mediator node state;

sending a MEDIATOR_HANDOVER message to the recipient mediator module, the MEDIATOR_HANDOVER message containing the content of the mediator handover message;

sending a MEDIATOR_CHANGED message to an associated TP module; and

then changing state in order to forward messages containing the content tag to the recipient mediator module.

49. A computer program product as claimed in claim 48, further comprising:

the TP module forwarding the MEDIATOR_CHANGED message to at least one LPP module;

the recipient mediator module generating a NEW_MEDIATOR_ACTIVE message, the NEW_MEDIATOR_ACTIVE message having a payload corresponding to the reallocated content, and broadcasting said NEW_MEDIATOR_ACTIVE message to all TP modules associated therewith; and

the LPP module buffering all incoming messages between receipt of the MEDIATOR_CHANGED message and receipt of the NEW_MEDIATOR_ACTIVE message.

50. A computer program product as claimed in claim 49, further comprising:

the LPP module then forwarding the NEW_MEDIATOR_ACTIVE message to the associated MR module; and

whenever a MR module receives a NEW_MEDIATOR_ACTIVE message, updating a routing table for said MR module to cause future content matching the payload of the NEW_MEDIATOR_ACTIVE message to be sent to the recipient mediator module rather than the donor mediator module;

informing the donor mediator module that the routing table has been updated, the donor mediator module thereafter ceasing to forward messages once all MR modules have been informed that the recipient mediator module is now the mediator module for the reallocated content.

51. A computer program product as claimed in claim 47, wherein the change in internal operation is a reconfiguration of the logical topology of the mediation network and wherein the control message is one or more reconfiguration messages.

52. A computer program product as claimed in claim 51, wherein the reconfiguration of the logical topology includes generation of a causal barrier to ensure that messages passing through the mediation network before the reconfiguration are delivered in advance of messages passing through the mediation network after the reconfiguration.

53. A computer program product claimed in claim 52, wherein the step of generating the causal barrier includes:

circulating said one or more reconfiguration messages around the mediation cycle; and

ensuring that each module in the cycle has been sufficiently notified of the reconfiguration.

54. A computer program product as claimed in claim 53, wherein the reconfiguration of the logical topology of the mediation architecture is the insertion of an additional local point of presence (LPP) node, and said one or more reconfiguration messages include a new_LPP message that uniquely identifies the additional LPP node, the insertion including:

in a predetermined additional LPP module at the additional LPP node, generating the new_LPP message and sending the new_LPP message to a corresponding MR module at an MR node;

in the corresponding MR module, receiving the new_LPP message, updating a reference count for the MR node, and propagating the new_LPP message to all mediator modules in the architecture;

in each mediator module, receiving the new_LPP message, and transmitting the new_LPP message to a respective, corresponding TP module at a TP node, each TP node having an associated credit balance;

in each of the corresponding TP modules, receiving the new_LPP message and sending a respective, extended new_LPP message to the additional LPP module, the extended new_LPP message including the respective associated credit balance;

in the additional LPP module, receiving the extended new_LPP messages, thereby completing the circulation of the new_LPP message; and

in the additional LPP module, summing the credit balances, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

55. A computer program product as claimed in claim 54, wherein the reconfiguration of the logical topology of the mediation architecture includes the further insertion of an additional mediator router (MR) node, and wherein said one or more reconfiguration messages further include a new_MR message that uniquely identifies the additional MR node, the further insertion including:

the additional LPP sending a new_MR message to a corresponding MR module at an MR node having a corresponding credit balance;

the corresponding MR module responding to the new_MR message by sending a new_MR_route_table message, which includes;

address information for the additional MR node, the address of the additional LPP node, routing information and a fraction of the corresponding credit balance;

the corresponding MR module then forwarding the new_MR_route_table message to an arbitrary mediator module;

the arbitrary mediator module passing the new_MR_route_table message to the additional LPP module;

the additional LPP module then passing the routing map to the additional MR module; and

in the additional MR module, using the contents of the new_MR_route_table message to initialise a new credit balance and routing maps.

56. A computer program product as claimed in claim 55, wherein the reconfiguration further includes, changing the MR module that the additional LPP module addresses, to the additional MR module, wherein the additional MR module sends a MR_initialised( ) message to the additional LPP module upon receipt of the new_MR_route_table message and wherein the additional LPP module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial MR modules respectively.

57. A computer program product as claimed in claim 53, wherein the reconfiguration of the logical topology of the mediation architecture is the insertion of an additional mediator (M) node, and said one or more reconfiguration messages include a new_M message that uniquely identifies the additional mediator node, the insertion including:

a predetermined additional mediator module generating the new_M message and sending the new_M message to a corresponding TP module at a TP node;

in the corresponding TP module, receiving the new_M message, updating a reference count for the TP node, and propagating the new_M message to all LPP modules in the architecture;

in each LPP module, receiving the new_M message, transmitting the new_M message to a respective, corresponding MR module at an MR node, each MR node having an associated credit balance;

in each of the corresponding MR modules, receiving the new_M message and sending a respective, extended new_M message to the additional mediator module, the extended new_M message including the respective associated credit balance; and

in the additional mediator module, receiving the extended new_M messages, thereby completing the circulation of the new_M message; and

in the additional mediator module, summing the credit balances, sufficient notification of the reconfiguration being assured when the credit sum reaches a predetermined completion value.

58. A computer program product as claimed in claim 57, wherein the reconfiguration of the logical topology of the mediation architecture includes the further insertion of an additional transmission proxy (TP) node, and wherein said one or more reconfiguration messages further include a new_TP message that uniquely identifies the additional TP node, the further insertion including:

the additional mediator module receiving the new_TP message;

the additional mediator module adding the address of the additional mediator node to the new_TP message and forwarding the new_TP message to a corresponding TP module at an TP node having a corresponding credit balance;

the corresponding TP module responding to the new_TP message by generating an extended new_TP message, which includes;

address information for the additional TP node, the address of the additional mediator node, a list of LPPs and a fraction of the corresponding credit balance;

the corresponding TP module then forwarding the new_TP message to an arbitrary LPP module;

the arbitrary LPP module then passing a new routing map message to the additional TP module;

the additional TP module then passing the routing map to the additional MR module; and

the additional TP module using the contents of the new routing map message to initialise a new corresponding credit balance and a list of LPP modules.

59. A computer program product as claimed in claim 58, wherein the reconfiguration further includes:

changing the TP module that the additional mediator module addresses to the additional TP module, wherein the additional TP module sends a TP_initialised( ) message to the additional mediator module upon receipt of the new routing map message and wherein the additional mediator module sends inc_ref_count( ) and dec_ref_count( ) messages to the additional and initial TP modules respectively.

60. A computer program product as claimed in claim 47, wherein the computer network further includes a failure detection node that is in communication with each node in the mediation network, the computer program product further comprising:

at the failure detection node, providing a failure detection module;

at each node of the mediation network, providing a failure reporting module;

whenever an incoming or outgoing communication link between nodes fails, each of said failure reporting modules reporting information relating to the failing communication link to said failure detection module; and

said failure detection module determining whether said failing link is indicative of a failing node.

61. A computer program product as claimed in claim 60, further comprising, where the failure detection module determines that said failing link is indicative of a failing node:

creating a new node of the same type as the failing node;

imbuing the new node with information relating to the failing node'"'"'s internal state and immediate neighbourhood topology; and

reconfiguring the network to use the new node in preference to the failing node.

62. A computer program product as claimed in claim 45, further comprising generating a message log of all incoming messages received by said predetermined mediator module.

63. A computer program product as claimed in claim 62, wherein the mediation task applied to said analyzed messages at said predetermined mediator module includes generating the message log.

64. A computer program product as claimed in claim 62, wherein the computer network further includes an external application, the computer program product further comprising:

generating the message log in said external application.

65. A computer program product as claimed in claim 47, wherein the change in internal operation is a structural refinement of the logical topology of the mediation architecture and wherein the control message is one or more refinement messages.

66. A computer program product as claimed in claim 65, wherein a subnetwork is inserted in place of a single node during the step of structural refinement.

67. A computer program product as claimed in claim 45, the computer program product including instructions for providing a datastore for storing information about the logical and physical structure of the mediated network.