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2a. Control links
2a1. The control link is established at system load time.
2a2. The status of a control link may be active or inactive
2a2a. The status of the control link should reflect the relationship between the HOSTs.
2b. Primary Links
2b1. Primary links are established by a user or executive call to the monitor
2b1a. The network identification number of the HOST to be linked to must be included in the call
2b1b. An attempt to establish more than one primary link to a particular HOST will be regarded as an error, and the request will be defaulted
2b1c. Standard Transmission Character Set
2b1c1. There will be a standard character set for transmission of data over the primary links and control links.
2b1c1a. This will be full (8 bit) ASCII.
2b1d. (get link) The protocol for establishing a link to HOST B from HOST A is as follows
2b1d1. A selects a currently unused link to HOST B from its allocation tables
2b1d2. A transmits a link-connect message to B over link 0.
2b1d3. A then waits for:
2b1d3a. A communication regarding that link from B
2b1d3b. A certain amount of time to elaspse
2b1d4. If a communication regarding the link is received from B, it is examined to see if it is:
2b1d4a. A verification of the link from B.
2b1d4a1. This results in a successful return from the monitor to the requestor. The link number is returned to the requestor, and the link is established.
2b1d4b. A request from B to establish the link. This means: that B is trying to establish the same link as A independently of A.
2b1d4b1. If the network ID number of A(Na) is greater than that of B(Nb), then A ignores the request, and continues to await confirmation of the link from B.
2b1d4b2. If, on the other hand, Na<Nb, A:
2b1d4b2a. Honors the request from B to establish the link,
2b1d4b2b. Sends verification as required,
2b1d4b2c. Aborts its own request, and repeats the allocation process.
2b1d4c. Some other communication from B regarding the link.
2b1d4c1. This is an error condition, meaning that either:
2b1d4c1a. A has faulted by selecting a previously allocated link for allocation,
2b1d4c1c. Or a message regarding allocation from B to A has been garbled in transmission.
2b1d4c2. In this case, A's action is to:
2b1d4c2a. Send a link disconnect message to B concerning the attempted connection
2b1d4c2b. Consider the state of HOST B to be in error and initiate entry to a panic routine(error).
2b1d5. If no communication regarding the link is received from B in the prescribed amount of time, HOST B is considered to be in an error state.
2b1d5a. A link disconnect message is sent to B from A.
2b1d5b. A panic routine is called(error).
2c. Auxilliary Links
2c1. Auxilliary links are established by a call to the monitor from a user program.
2c1a. The request must specify pertinent data about the desired link to the monitor
2c1a1. The number of the primary link to B.
2c1b. The request for an auxilliary link must be made by a user program in each of the HOSTs (A and B).
2c1c. If Na > Nb, then HOST A proceeds to establish a link to HOST B in the manner outlined above (getlink).
2c1d. If Na<Nb, then A waits:
2c1d1. For HOST B to establish the link (after looking to see if B has already established the corresponding link).
2c1d2. For a specified amount of time to elapse.
2c1d2a. This means that HOST B did not respond to the request of HOST A.
2c1d2b. The program in HOST A and B should be able to specifiy the amount of time to wait for the timeout.