SYSTEM AND METHOD FOR RELIABLE PACKET DATA TRANSPORT IN A COMPUTER NETWORK
A system and method for reliably transmitting a request from a client application ( 50 ) running on a client system ( 13 ) to a server application ( 52 ) running on a server system ( 15 ) and receiving a reply to the request, in which functions that provide parameters governing the reliable transport mechanism and message forming and parsing services are provided by the application processes to and called from application-layer protocol stacks ( 58, 60 ).
1 . A method, at a client computer, for reliably transmitting requests for exchange of messages between a client application running on the client computer and a server application running on a server computer, comprising:
maintaining a plurality of personality functions;
selecting a path between the client application and the server application;
selecting a first set of personality functions pertinent to one or more communication links of the path, based on the requirements of the one or more communication links and the client application requirements; and
linking the client application with the first set of personality functions.
2 . A method as claimed in claim 1 , wherein the personality functions of the set of the personality functions are called by the client application to perform reliable transport-related tasks.
3 . A method as claimed in claim 2 , wherein a personality function determines one or more parameters for a reliable transport-related task.
4 . A method as claimed in claim 1 , wherein a personality function performs one of:
parsing messages received from the transport layer;
adding headers or trailers to requests or replies to form messages for the protocol stack to send to the transport layer, or
providing retransmit and reply cache timer intervals for use by the server application.
5 . A method as claimed in claim 1 , wherein a personality function performs one of: handling creation and parsing of headers, or modifying the data being transported.
6 . A method as claimed in claim 1 , wherein a personality function modifies the payload or adds additional data to a message for transmissions sent between network applications that expect data to be encoded differently.
7 . A method as claimed in claim 1 , wherein a personality function performs one of:
setting up a connection;
wrapping a payload in a header to form a message to be sent to the transport layer;
determining a time-out interval for the i-th retransmission of a message;
determining a total timeout interval allowed for all retransmissions of a message; and
parsing the messages received from the transport layer to determine the type of message for the client application.
8 . A method as claimed in claim 1 wherein a message is one of a request, a reply, a provisional reply, or an acknowledgement.
9 . A method as claimed in claim 1 , wherein the plurality of personality functions includes at least a personality for over-the-air requests, a personality for over-the-backhaul requests and a personality for billing requests.
10 . A method as claimed in claim 9 , wherein the personality for over-the-air requests provides frequent retransmissions with a hard limit on how many retransmissions are made before an error is reported.
11 . A method as claimed in claim 9 , wherein the personality for over-the-backhaul requests provides exponential back-off assuming that losses could be due to congestion.
12 . A method as claimed in claim 9 , wherein the personality for billing requests provides retransmissions for a very long time before giving up.
13 . A method as claimed in claim 3 , wherein the one or more parameters includes a time-out period for the i-th transmission of a request to be made before an error is reported.
14 . A method as claimed in claim 3 , wherein the one or more parameters includes a total allowed number of transmissions of the request message to be made before an error is reported.
15 . A method as claimed in claim 3 , wherein the one or more parameters includes a time-out period for a reply cache timer.
16 . A method as claimed in claim 1 , wherein the plurality of personality functions includes a function that parses a message and returns a reply message which includes a type and sequence number of that message.
17 . A method as claimed in claim 16 , wherein the reply message further comprises a payload if the message includes a payload, the payload.
18 . A method as claimed in claim 1 , wherein, if a reply message received by the client application from the server application contains a sequence number of a request message and a type code that indicates that it is a provisional reply message to the request message, then a current time-out period for retransmission is modified to delay its expiration.
19 . A method as claimed in claim 1 , further comprising:
wrapping a request in a payload field of a message;
starting a retransmission timer established based on the selected set of personality functions; and
transmitting the message to the server computer along the path.
20 . A method as claimed in claim 1 , further comprising:
selecting an alternative path between the client application and the server application;
selecting a second set of personality functions based on the requirements of communication links of the alternative path and the client application requirements, and
linking the client application with the second set of personality functions.