Requirements of TCPMPL

One of the first steps in designing the custom message passing layer for WARPED is to enumerate the goals of this message passing layer. Some of the goals of TCPMPL are as follows:

• Low Software Overhead: The main goal of TCPMPL is to reduce the overhead of the software communication layer in WARPED
• Functionalities: The next goal of TCPMPL is to support the functionalities of a message passing layer that WARPED requires for correct functional execution. The main functionalities WARPED needs is SPMD, sending, receiving and probing of messages.
• Shared LANs: This is one of the important goals of TCPMPL. TCPMPL will be run on shared LANs. The local network will be shared among other internetwork applications running on any workstations. It should not assume any dedicated switch to achieve a better communication subsystem performance.
• Portability: The software should be portable to a majority of platforms. Since it is developed exclusively for WARPED and WARPED is used by many researchers, portability is one of the main goals of TCPMPL.

Before designing the TCPMPL message passing library, the features of a message passing layer that WARPED requires is needed. The following are the features that must be supported by the library for functional execution of WARPED:

• SPMD: The library must support the SPMD concept. Programs compiled with the library should have the feature of starting the parallel application on different machine and achieve synchronization among themselves before the application code is executed.
• Message Delivery: The service provided by TCPMPL must be reliable, and must ensure ordered delivery. Reliability is required as the underlying network may not be reliable. In order to ensure reliability, the message passing layer should take care of message retransmission, if the message has not reached its destination. Another feature which is indispensable is ensuring the FIFO property while delivering the messages. The messages are to be delivered to the destination process in the order in which they were sent. There is no restriction on the messages from different processes. It is up to the implementation to deliver messages from different processes in any order.
• Message Boundary: When an user application sends a message of a particular size, TCPMPL must maintain the message boundary when giving the message to the receiver. Consider a sequence of messages of sizes , , and sent in this order to a destination process. The destination process should first receive a message of size , followed by a message of size and then the message of size . It should not deliver a message of size () bytes or in any other combination.
• Send: The library must support the sending of messages from one process on a machine to any other process.
• Probe: The user application must be able to poll for new messages through TCPMPL, that can be received without blocking.
• Receive: The application must be able to receive messages from any process in its process group.

 
• Configuration of Processes
• Initialization of Processes
  • Starting of Processes
  • Establishment of Communication Channels
• Reliability of Message Delivery
• Maintaining FIFO property
• Message Boundary
• Primitive Error Detection
• Portability