Digital Traffic Network (DTN) System Guidance
I. SCOPE AND PURPOSE - The Digital Traffic Network (DTN) is a continuous system of computer-assisted, automatic digital stations, serving as Mailbox Operations (MBOs), each under the control of a system operator (sysop). Forwarding operations occur on both a fully automated basis and manually depending upon prevailing circumstances, routing plans and sysop preferences. MBOs access other system MBOs automatically or manually, and “keyboard” operators access MBOs manually.
This Guidance supplements NTS Area Terms of Reference, and should be interpreted consistent with the Public Service Communications Manual (PSCM), Section II, published by the ARRL. It describes routing approaches, sets DTN station roles and coordination standards, and outlines generally accepted principles and practices within the DTN.
II. DTN ROUTING APPROACHES – Area Digital Coordinators (ADCs) have the flexibility to implement a variety of routing plans consistent with NTS principles and other requirements. One approach uses Area Digital Hubs -- MBO stations designated in the three geographical areas, Eastern, Central and Pacific by the respective ADCs, providing scheduled inter-area forwarding and coordination. This approach permits ADCs the flexibility to establish one or more such MBOs to achieve a systematic and scaled digital-routing plan under this Guidance. The area hub approach has access and capacity limitations. Another approach is an “open system” in which any digital station may forward to an MBO within an area at any time. This approach increases flexibility, but, to some extent, requires more effort by keyboarding operators to locate and poll traffic coming into a region or area.
III. COORDINATION AND ROLES - ADCs exchange information with respect to status and operation of MBOs and disseminate received information to the NTS levels within the area. ADC-designated digital station operators making changes will consult with and issue information through the ADC.
A. Area Digital Coordinators
1. Qualifications – ADCs must presently serve as an DTN MBO sysop, or have past MBO sysop experience and have the capability to promptly activate such an operation.
2. Duties – The ADC duties include the following:
a) Designate digital stations at the region and area levels;
b) Assign digital stations to a MBO polling schedule;
3. Issue standard operating procedures;
4. Issue certificates in recognition of participation;
5. Coordinate the standard frequency plan; and
6. Collect digital statistics and report activity.
B. Station Operations. Digital station operators perform functions consistent with Area, Region and Section responsibilities as prescribed for the NTS in accordance with the PSCM. Digital station operations at the NTS section and local level are the responsibility of the Section Traffic Manager (STM). To the extent feasible, ADCs should coordinate digital operations with the STMs.
1. Area/Region HUB MBOs- One or more stations are designated by the ADC as a Hub or as Hub backups and perform forwarding tasks according to the digital routing plan. These stations:
a) Operate fully automatically under computer control;
b) Scan multiple bands according to prescribed plan;
c) Auto-forward according to prescribed schedules; and
d) Submit reports and station information to the ADC.
2. DIGITAL RELAY STATIONS (DRS) - Perform functions of relay involving posting of message files and removing traffic from DTN MBOs for appropriate nets or TCC functions in support of NTS objectives, observing DTN principles and practices. DRSs are designated by the ADC and:
a) Perform assigned relay duties to clear area MBOs
b) Route incoming traffic via area/region nets
c) handle assigned TCC schedules and traffic
d) Submit periodic reports as required.
IV. DIGITAL STATION OPERATING PRINCIPLES AND PRACTICES
A. DTN operates in parallel with the other NTS nets and circuits but on a continuous basis and at all levels. Access is available to all, both "keyboarders" and sysops consistent with proscribed DTN station roles and this Guidance. Roaming in other areas is discouraged except as necessary to accomplish manual forwarding due to system failures. Stations may be excluded for causing interference or unauthorized removal of traffic.
B. DTN has established a core of common frequencies covering all bands that provide suitable propagation. Area and Regional MBOs may add additional frequencies for their own forwarding use but are not required to publish the additional frequencies. This core list may change from time to time but provisions must be coordinated through the ADC with the DTN sysops within the area. All DTN MBOs are expected to scan the core list frequencies.
C. MBO sysops are encouraged to provide multiple modes, with an emphasis on the faster ones. Every effort should be made to avoid using AmTOR for MBO forwarding. Ideally an DTN MBO should be available on PacTOR, and Clover or PacTOR II. VHF packet should be used to provide higher speed access for local “keyboarders”
The use of VHF packet should be limited to those BBSs KNOWN to be reliable for NTS use. General packet circuits should never be used to route NTS traffic. In general, a single relay by packet represents a reliable disposition of NTS formatted traffic. HF packet should NEVER be used to forward NTS traffic.
D. NTS traffic received into NTS digital circuits will be routed via NTS circuits and/or nets except in rare emergency cases when no NTS outlet is then available or some other more expeditious and reliable route is available. Such exceptions should not become the basis for establishing a routine circuit for such traffic.
E. DTN sysops should handle their traffic giving due regard to message precedence, just as is done in the cyclic nets.
F. TCC stations may use DTN circuits to forward traffic routed through schedules. Such traffic may be placed on the selected MBO by the sending TCC station and removed by the receiving TCC station. Use of the "P" type may be necessary to ensure that ONLY the receiving TCC station gets the traffic. Standard reports to the appropriate TCC Director are required, and traffic sent or received using type "P" should be counted as though it had been "T".
G. Counts of traffic received and traffic forwarded should be reported by the individual MBO sysop to the ADC. Originations and deliveries are not included in these reports but should be reported to the STM as part of the Station Activity Report (SAR).
H. NTS digital stations are expected to forward or ensure delivery of all traffic on hand in a timely manner. If a station experiences a system failure it is the sysop's responsibility to find a way to clear the traffic on hand. If it is not possible to extract all messages on hand from the failed disk drive, then that sysop must notify at least one of the other DTN sysops (preferably the ADC) and ask that a notice be passed throughout the system advising of the failure. Any sysop who has recently passed traffic to the failed MBO should then review the situation and reinstate any messages so forwarded. The sysop of the failed MBO should, after recovery, try to establish which messages were on hand, pass a list of them to all other DTN sysops for further follow up and place all of them on hold. When sufficient time has passed that no further demand is expected to be made regarding these messages the failed MBO sysop may delete them.
J. MBO sysops should participate at least occasionally in their local and section nets to maintain cyclic net proficiency.
K. Since the NTS Digital System operates on a continuous basis, traffic should never be removed from an NTS MBO and taken to a cyclic net for later transmission unless it has reached the (digitally serviced) point nearest its destination. There is one exception to this: if an opportunity exists to DIRECTLY DELIVER a message to a station for delivery through the net, then it is proper to remove the traffic from the MBO. Removing traffic from an MBO to increase the traffic count of a cyclic net only delays traffic and is not an acceptable practice.
L. Keyboarder stations are responsible for ensuring that messages they remove from a BBS or MBO are marked as forwarded (that is their status is changed to "TY" or "TF". Failing to do so will lead to duplicated attempts to relay and deliver such messages. Likewise, Keyboarders should NEVER download messages marked as already forwarded.
V. AREA DIGITAL STANDARD OPERATING PROCEDURES
ADCs are authorized to develop and implement Area Standard Operating Procedures (SOPs) for the designated DTN stations within the area. Such SOPs shall be consistent with this Guidance and shall be filed with the Area Staff Chair and League headquarters.