The Packet Radio
“
2 N 1
”
Handbook
by
Buck Rogers
K4ABT
Section 1
;
Packet Radio “The Basics
”
Section 2
;
The X1J4 System Node Operator’s (SNO) Handbook
Section II
;
TheNET X1J4 System Node Operators Handbook
__ Page 35
Chapter 14 Section II
ROUTE QUALITY ANALYSIS:
For each route in its routing table, TheNET
X1
maintains a route quality value in the range 255 (best) to 0 (worst). This
allows it to keep alternate routes in order of quality, and to select the best available route to a destination. A route quality
value can best be visualized as a fraction (the value divided by 256) which quantifies the speed and reliability of a particular
route in comparison to a theoretically perfect route (an infinitely fast and perfectly error-free path) of quality 256.
For example, a route of quality 230 can be thought of as being "90% perfect" in speed and reliability (230/256 = 0.90). The
quality of each frequency used by a TheNET
X1
node is established by the sysop of the node. As a starting point, we
suggest the following values to be used as baud/quality/parameters:
Baudrate
Description
Quality
% Perfect
9600-baud RS232 wire interconnect (2-port)
255
99%+
9600-baud RS232 satellite interconnect (2-port)
252
98
%
9600-baud RS232 wire interconnect (3-port)
248
97
%
9600-baud HDLC isolated inter-node backbone
240
94
%
1200-baud HDLC isolated inter-node backbone
224
88
%
1200-baud HDLC user-accessed frequency
192
75
%
1200-baud HF frequency
180
70
% (Not recommended)
300-baud HDLC HF frequency
128
50
%
The quality of a multi-segment route is simply the product of the qualities of each individual segment, where quality values
are treated as fractions with an implicit denominator of 256. For example, a four-segment route that consists of two 9600-
baud RS232 interconnect segments (quality 255) and two 1200-baud HDLC backbone segments (quality 224) has a
calculated quality of 194 (255/256 times 255/256 times 224/256 times 224/256 equals 194/256). Quality calculations are
rounded to the nearest 256th.
In practice, I have found that path quality for a 1200 baud neighbor node should be locked at 192 and path quality for a
9600 baud backbone neighbor node should be locked at 240.
