MDS 05-2708A01, Rev. F
MDS TransNET Ref. Manual
53
Extended SAF Network
Below is an example of a multilevel network utilizing two repeaters—X
J,K
and X
K,L
. The example demonstrates the extensibility of the network. In this
case, messages directed to Remotes in the sub-network L will be relayed
through Extension radios X
J,K
and X
K,L
. Like the previous example, the
Extension radios will split their operating time equally between their Master
and Remote “personalities.” This multi-layered network can be extended
indefinitely without degradation in throughput, beyond that initially incurred
by placing the network in the SAF mode.
Invisible
place
holder
Figure 18. Extended SAF Network
Networks: J, K, L
Retransmission and ARQ Operation
Functionally, the sub-network side of an Extension behaves like a corre-
sponding connection between a Master and a Remote.
When an Extension is using its “Master personality” it sends acknowledg-
ments and performs unconditional retransmissions based on its
REPEAT
count.
When an Extension is using its “Remote personality,” acknowledgments are
processed and retransmissions occur as needed, up to the number of times
specified by the
RETRY
count value.
If data arrives from a new source prior to completion of retransmissions, it is
considered to be a violation of the polling model protocol. The new data takes
precedence over the old data, and the old data is lost. In such a situation, new
data is likely to be corrupted as it will have some old data mixed in with it.
SAF Configuration Example
Here is an outline for the configuration of a simple store-and-forward link.
X
K,L
R
L
R
L
M
J
R
J
R
J
X
J,KI
R
J
R
K
R
K
R
L
Sub-Network “J”
Sub-Network “K”
Sub-Network “L”
