Performance Center is an enterprise version of LoadRunner (LR) that allows concurrent runs in an organization by managing a pool of Controllers and Load generators. It is built on a web interface and suitable for organizations that require running multiple load test projects across the organization. You can find out more about the sales talk from the vendor here if you like. To put it simply, Performance Center can run multiple load test while LR can run a single load test.

Performance Center is designed to manage load tests in the concept of projects (or load test projects). And for each project, you are able to trace the number of runs pertaining to each individual project. Privileges such as Administrators, Consultants, Tester and Managers are also introduced in Performance Center. Administrator role maintains the Performance Center setup as a whole and has the rights to manage the resources, determine the maximum number of concurrent users the project can generate. While privileges for users such as Consultant, Tester or Manager can be configured depending on the organization requirements.

Depends; In order to answer the "depends", we need to understand some basics of JMS and its relation with LoadRunner. First, JMS can be implemented in two ways: (a) via HTTP/XML or (b) via RMI-Java. Going back to the fundamentals of LoadRunner on the article for protocols, "Which protocol to use?", its essential to know what's the communication mechanism in order to select the protocol from LoadRunner. A more detailed description on the different implementations can be found in "JMS over XML-RPC with HTTP protocol" from the TheServerSide.com.

Yes, it's possible and there are couple of ways in doing it (disclaimer: not all are applicable). Was actually responding to fews question on this topic and well, might as well share with everyone. Let's get some fundamentals right on Web Services, (a) they can be implemented without any front-end GUI (e.g. browser) causing challenges to conventional testing techniques. If it was implemented with a front-end, that makes the scripting a little bit easier as it's the same for conventional testers (no issue here). (b) It communicates or delivers via SOAP/HTTP. That's to say, HTTP protocol is the medium of communication, one of the key concepts of using load testing tools such as LoadRunner is understanding the protocol. (Refer to "Which protocol to use?" on protocol fundamentals)

The program was written by Van Jacobson and others. It is based on a clever use of the Time-To-Live (TTL) field in the IP packet’s header. The TTL field is used to limit the life of a packet. When a router fails or is mis-configured, a routing loop or circular path may result. The TTL field prevents packets from remaining on a network indefinitely should such a routing loop occurs. A packet’s TTL field is decremented each time the packet crosses a router on its way through a network. When its value reaches 0, the packet is discarded rather forwarded. When discarded, the ICMP TIME_EXCEEDED message is sent back to the packet’s source to inform the source that the packet was discarded. By manipulating the TTL field original packet, the program traceroute uses information from these ICMP messages to discover paths through a network.