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osmux-reference: Add sequence charts 

Change-Id: Ic2c63e4d9e67b877dc06a206ec7f07d0704329a5
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Pau Espin 2017-07-19 13:21:25 +02:00 committed by Neels Hofmeyr
parent ac70cf9658
commit 1ce6c62914
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doc/manuals/osmux-reference.adoc
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@ -307,6 +307,195 @@ of 17 bytes is to be allocated after the header.
* On receival of this kind of OSmux frame, it's usually enough for the reader to
discard the header plus the calculated padding and keep operating.
== Sequence Charts
=== Trunking
Following chart shows how trunking works for 3 concurrent calls from different
MS on a given BTS. In this case only uplink data is shown, but downlink follows
the same idea. Batching factor is set to 1 to easily illustrate trunking mechanism.
It can be seen how 3 RTP packets from 3 different Ms (a, b, and c) arrive to the
BSC from the BTS. The BSC generates 3 OSmux frames and stores and sends them
together in one UDP packet to the BSC-NAT. The BSC-NAT decodes the three OSmux
frames, identifies each of them through CID values and transform them back to
RTP before sending them to the MGW.
["mscgen"]
----
msc {
hscale = 2;
bts [label="BTS"], bsc [label="BSC"], bscnat [label="BSC-NAT"], mgw [label="MGW"];
...;
--- [label="3 Regular RTP-AMR calls using OSmux (has been ongoing for some time)"];
bts => bsc [label="RTP-AMR[seq=y,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=z,ssrc=MSc]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m,AMR(y)],Osmux[ft=2,cid=i+1,seq=n,AMR(x)],Osmux[ft=2,cid=i+2,seq=l,AMR(z)]]"];
bscnat => mgw [label="RTP-AMR[seq=o,ssrc=r] (originally seq=y,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p,ssrc=s] (originally seq=x,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=q,ssrc=t] (originally seq=z,ssrc=MSc)"];
bts => bsc [label="RTP-AMR[seq=y+1,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+1,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=z+1,ssrc=MSc]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+1,AMR(y+1)],Osmux[ft=2,cid=i+1,seq=n+1,AMR(x+1)],Osmux[ft=2,cid=i+2,seq=l+1,AMR(z+1)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+1,ssrc=r] (originally seq=y+1,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+1,ssrc=s] (originally seq=x+1,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=q+1,ssrc=t] (originally seq=z+1,ssrc=MSc)"];
bts => bsc [label="RTP-AMR[seq=y+2,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+2,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=z+2,ssrc=MSc]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+2,AMR(y+2)],Osmux[ft=2,cid=i+1,seq=n+2,AMR(x+2)],Osmux[ft=2,cid=i+2,seq=l+2,AMR(z+2)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+2,ssrc=r] (originally seq=y+2,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+2,ssrc=s] (originally seq=x+2,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=q+2,ssrc=t] (originally seq=z+2,ssrc=MSc)"];
}
----
=== Batching
Following chart shows how batching with a factor of 3 works. To easilly
illustrate batching, only uplink and one concurrent call is considered.
It can be seen how 3 RTP packets from MSa arrive to the BSC from the BTS. The
BSC queues the 3 RTP packets and once the batchfactor is reached, an OSmux frame
is generated and sent to the BSC-NAT. The BSC-NAT decodes the OSmux frames,
transforms each AMR payload into an RTP packet and each RTP packet is scheduled
for delivery according to expected proportional time delay (and timestamp field
is set accordingly).
["mscgen"]
----
msc {
hscale = 2;
bts [label="BTS"], bsc [label="BSC"], bscnat [label="BSC-NAT"], mgw [label="MGW"];
...;
--- [label="Regular RTP-AMR call using OSmux with batch factor 3 (has been ongoing for some time)"];
bts => bsc [label="RTP-AMR[seq=x,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+1,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+2,ssrc=MSa]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m,AMR(x),AMR(x+1),AMR(x+2)]]"];
bscnat => mgw [label="RTP-AMR[seq=o,ssrc=r] (originally seq=x,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+1,ssrc=r] (originally seq=x+1,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+2,ssrc=r] (originally seq=x+2,ssrc=MSa)"];
bts => bsc [label="RTP-AMR[seq=x+3,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+4,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+5,ssrc=MSa]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+1,AMR(x+3),AMR(x+4),AMR(x+5)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+3,ssrc=r] (originally seq=x+3,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+4,ssrc=r] (originally seq=x+4,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+5,ssrc=r] (originally seq=x+5,ssrc=MSa)"];
bts => bsc [label="RTP-AMR[seq=x+6,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+7,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=x+8,ssrc=MSa]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+2,AMR(x+6),AMR(x+7),AMR(x+8)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+6,ssrc=r] (originally seq=x+6,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+7,ssrc=r] (originally seq=x+7,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=o+8,ssrc=r] (originally seq=x+8,ssrc=MSa)"];
}
----
=== Trunking and Batching
Following chart shows how trunking and batching work together. The chart shows 2
concurrent calls from different MS on a given BTS, and BSC is configured with a
batch factor of 3. Again only uplink data is shown, but downlink follows the
same idea. Batching factor is set to 1 to easily illustrate trunking mechanism.
["mscgen"]
----
msc {
hscale = 2;
bts [label="BTS"], bsc [label="BSC"], bscnat [label="BSC-NAT"], mgw [label="MGW"];
...;
--- [label="2 Regular RTP-AMR call using OSmux with batch factor 3 (has been ongoing for some time)"];
bts => bsc [label="RTP-AMR[seq=x,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+1,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+1,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+2,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+2,ssrc=MSb]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m,AMR(x),AMR(x+1),AMR(x+2)],Osmux[ft=2,cid=i+1,seq=n,AMR(y),AMR(y+1),AMR(y+2)]]"];
bscnat => mgw [label="RTP-AMR[seq=o,ssrc=r] (originally seq=x,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p,ssrc=s] (originally seq=y,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+1,ssrc=r] (originally seq=x+1,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+1,ssrc=s] (originally seq=y+1,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+2,ssrc=r] (originally seq=x+2,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+2,ssrc=s] (originally seq=y+2,ssrc=MSb)"];
bts => bsc [label="RTP-AMR[seq=x+3,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+3,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+4,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+4,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+5,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+5,ssrc=MSb]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+1,AMR(x+3),AMR(x+4),AMR(x+5)],Osmux[ft=2,cid=i+1,seq=n+1,AMR(y+3),AMR(y+4),AMR(y+5)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+3,ssrc=r] (originally seq=x+3,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+3,ssrc=s] (originally seq=y+3,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+4,ssrc=r] (originally seq=x+4,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+4,ssrc=s] (originally seq=y+4,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+5,ssrc=r] (originally seq=x+5,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+5,ssrc=s] (originally seq=y+5,ssrc=MSb)"];
}
----
=== Marker bit
As described earlier, the Marker bit is always expected to relate to the first
AMR payload of an OSmux frame. Thus, special considerations may be followed when
the OSmux encoder receives an RTP packet with a marker bit. For instance,
previously enqueued RTP packets may be sent even if the configured batch factor
is not reached.
We again use the scenario with 2 concurrent calls and a batch factor of 3.
["mscgen"]
----
msc {
hscale = 2;
bts [label="BTS"], bsc [label="BSC"], bscnat [label="BSC-NAT"], mgw [label="MGW"];
...;
--- [label="2 Regular RTP-AMR call using OSmux with batch factor 3 (has been ongoing for some time)"];
bts => bsc [label="RTP-AMR[seq=x,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+1,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+1,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+2,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+2,ssrc=MSb]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m,AMR(x),AMR(x+1),AMR(x+2)],Osmux[ft=2,cid=i+1,seq=n,AMR(y),AMR(y+1),AMR(y+2)]]"];
bscnat => mgw [label="RTP-AMR[seq=o,ssrc=r] (originally seq=x,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p,ssrc=r] (originally seq=y,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+1,ssrc=r] (originally seq=x+1,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+1,ssrc=s] (originally seq=y+1,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+2,ssrc=r] (originally seq=x+2,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+2,ssrc=s] (originally seq=y+2,ssrc=MSb)"];
bts => bsc [label="RTP-AMR[seq=x+3,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+3,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+4,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+4,ssrc=MSb] with Marker bit set M=1"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+1,AMR(x+3),AMR(x+4)],Osmux[ft=2,cid=i+1,seq=n+1,AMR(y+3)]]"];
bscnat => mgw [label="RTP-AMR[seq=o+3,ssrc=r] (originally seq=x+3,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+3,ssrc=s] (originally seq=y+3,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+4,ssrc=r] (originally seq=x+4,ssrc=MSa)"];
bts => bsc [label="RTP-AMR[seq=x+5,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+5,ssrc=MSb]"];
bts => bsc [label="RTP-AMR[seq=x+6,ssrc=MSa]"];
bts => bsc [label="RTP-AMR[seq=y+6,ssrc=MSb]"];
bsc => bscnat [label="UDP[Osmux[ft=2,cid=i,seq=m+2,AMR(x+5),AMR(x+6)],Osmux[ft=2,cid=i+1,seq=n+2,AMR(y+4),AMR(y+5),AMR(y+6)]]"];
bscnat => mgw [label="RTP-AMR[seq=p+4,ssrc=s] (originally seq=y+4,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+5,ssrc=r] (originally seq=x+5,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+5,ssrc=s] (originally seq=y+5,ssrc=MSb)"];
bscnat => mgw [label="RTP-AMR[seq=o+6,ssrc=r] (originally seq=x+6,ssrc=MSa)"];
bscnat => mgw [label="RTP-AMR[seq=p+6,ssrc=s] (originally seq=y+6,ssrc=MSb)"];
}
----
== Evaluation: Expected traffic savings