The Digits Translation Table
The Digits Translation Table is the "sorting machine" or "routing table" for network messages. When a user addresses a message to a remote mailbox, NP Net compares the mailbox address to the prefixes listed in the Digits Translation Table. The Digits Translation Table tells where the message is going, and how many digits the remote node must delete ("absorb") to find the destination mailbox.
The following excerpt from a Digits Translation Table indicates that any mailbox addresses that begin with 21 or 22 are to be routed to node 2 (Chicago), and any addresses that begin with 23 are to be routed to node 8 (Dallas). In addition, the remote nodes must strip off two digits (the prefix) to find the destination mailbox number.
Node Node Digits To
Prefix Number Name Absorb
21 2 Chicago 2
22 2 Chicago 2
23 8 Dallas 2
It is recommended that the table be the same in each node. You can enter your local node number in this table. If some nodes are not allowed to communicate with certain remote nodes, then use the GCOS feature to properly segregate those communities of interest.
Node Prefixes
All network messages are routed by the node prefixes in the Digits Translation Table. Node prefixes are the leading digits of network mailbox numbers that are unique to a node. In the sample Digits Translation Table above, the prefix 23 uniquely identifies node 8; only network addresses at node 8 begin with the digits 23.
The length of an individual prefix depends on whether you are using access codes (see below) and whether mailboxes on two or more nodes share the first, second, third, fourth, etc. digits. Each prefix consists of a number of shared leading digits, plus one digit that is found only in the mailboxes of a single node.
Example:
The San Jose node has the following dialing plan:
4,N4,N4,N4,4,4,4,4,4
This means that the remote mailbox numbers that San Jose can access begin with 2, 3, or 4, and consist of four digits.
The Chicago node (Node 2) uses mailbox numbers 2000 to 2999, and 3000 to 3250
The New York node (Node 4) uses mailbox numbers 3260 to 3999, and 4000 to 4499
The Dallas node (Node 6) uses mailboxes 4500 to 4999
Because none of the nodes have overlapping mailbox numbers, the digits to absorb count is 0 for all prefixes. The San Jose Digits Translation Table would look like this:
Node Node Digits To
Prefix Number Name Absorb
2 2 Chicago 0
30 2 Chicago 0
31 2 Chicago 0
320 2 Chicago 0
321 2 Chicago 0
322 2 Chicago 0
323 2 Chicago 0
324 2 Chicago 0
325 2 Chicago 0
326 4 New York 0
327 4 New York 0
328 4 New York 0
329 4 New York 0
33 4 New York 0
34 4 New York 0
35 4 New York 0
36 4 New York 0
37 4 New York 0
38 4 New York 0
39 4 New York 0
40 4 New York 0
41 4 New York 0
42 4 New York 0
43 4 New York 0
44 4 New York 0
45 6 Dallas 0
46 6 Dallas 0
47 6 Dallas 0
48 6 Dallas 0
49 6 Dallas 0
If a message is made for remote mailbox 3267, NP Net checks the table, sees that prefix 326 matches this mailbox, adds a flag to the message that tells the remote node to absorb no leading digits from the incoming mailbox number, then adds the message to the queue for node 4.
Note the variation in the number of digits needed to make a prefix unique to a node. Chicago is the only node using mailboxes that begin with 2, so that prefix only needs to be one digit. Chicago and New York both uses mailboxes in the 3200 series, so these prefixes must be taken out to the third digit to be unique.
Another thing that is noteworthy about this dialing plan is that no remote mailbox numbers overlap, either with each other or with local San Jose mailboxes. New York, Chicago, and Dallas could use mailbox numbers that begin with 1, 5, 6, 7, 8, and 9, but users on the San Jose system cannot send messages to these mailboxes through NP Net. The San Jose dialing plan will need to be configured differently in order to enable messages to those mailboxes. The Digits To Absorb feature can be used to add this flexibility to the dialing plan.
Digits To Absorb
You assign a Digits To Absorb number to each prefix in the Digits Translation Table. The number of digits can be from 0 to 10. After NP Net matches the destination mailbox number to a prefix, it attaches the corresponding Digits To Absorb count to the message. The remote node deletes the specified number of leading digits to convert the network mailbox number to a local mailbox number. You must configure each node to send Digits To Absorb counts that allow remote nodes to translate network mailbox numbers to valid local mailbox numbers.
Digits to Absorb and Local Mailboxes
If local mailbox numbers match a dialing plan position that contains an N, then there must be a prefix entry in the Digits Translation Table that has the local node number.
If every node on the network uses the same dialing plan, all mailboxes must be the same length. For example, if every node on a network uses the dialing plan N7,N7,N7,N7,N7,N7,N7,N7,N7, users on every node are permitted to make messages for local or remote mailboxes that have 7 digit numbers only. Since NP Net does not absorb digits from local mailboxes, all local mailboxes on every system must be 7 digits; therefore, no digit absorption is possible throughout the network. The following section shows a way to formulate a network-wide dialing plan to avoid this limitation.
Using the Digits to Absorb Feature to Create "Access Codes"
The digits to absorb feature can simplify Digit Translation Table configuration by allowing each node administrator to formulate "access codes" for the other nodes on the system. A user enters the access code for the node before entering the mailbox number of the recipient when making a message for a remote mailbox. For example, if the access code for Boston is 82 and the mailbox you want to reach is 100, you would enter 82100.
You can implement this feature with the either N or the P character in the dialing plan. With the N implementation, users will enter just the access code and mailbox. With the P implementation, users will enter a "network" access code digit, identifying that a network message is being made, then a "node" access code, identifying the destination node, then the destination mailbox number.
The access codes are prefixes in the Digits Translation Table; the associated digits to absorb count tells the remote node to delete the access code to obtain the local mailbox number. Problems with mailbox number overlap between remote nodes are avoided, since the "real" mailbox number (the local mailbox number on the remote node) is obtained after the message is sent.
Using the Digits to Absorb Feature to Create Same-Length Mailbox Numbers
If you want users to always enter the same number of digits for all network addresses, you can use the Node Prefixes and the Digits to Absorb feature in the Digits Translation Table to "pad out" the mailbox numbers for nodes that use shorter extensions. For example, if node 2 uses 3-digit extensions and node 6 uses 4-digit extensions, you can create prefixes for node 2 that are one digit longer than the prefixes for node 6. You also set the Digits to Absorb count for node 2 to be one digit greater than the Digits to Absorb for node 6. The sample Digits Translation Table below shows this kind of configuration.
Node Node Digits To
Prefix Number Name Absorb
211 2 Chicago 3
22 6 Dallas 2