Bidirectional connections

[danalex97]

When two nodes communicate via the capacity module they create unidirectional links. However, when a connection is established from node A to node B, node B cannot see the Link unless node A specifically sends the object through a ControlMessage. This effectively allows establishing a link only after an RTT.

This is, however, impractical since the user needs to implement a handshake mechanism for bidirectional connections. This issue is about creating and testing a BidirectionalPerfectLink in the capacity module. The new bi-directional link will eventually replace the PerfectLink.

Requirements:

• when A calls Connect a new Link object should be created
• when B calls Connect, instead of creating a new Link object, the Link object created by A should be used
• when A calls Connect another Link object should be created
• [...]

Implementation: the easiest way to implement this is probably as following:

• when A calls Connect, a new Link L(A) is created
• A sends a control message to B
• when B calls Connect, a new Link L(B) is created
• B sends a control message to A
• when B receives the control message, B replaces L(B).download with L(A).download
• when A receives the control message, A replaces L(A).download with L(B).download
• this way, both A and B have different Link objects, but the objects are correctly linked

An example handshake mechanism can be found here.