manual: Include QoS chapter and add osmo-pcu specific example

Change-Id: I4d409b55861f05ba229dc5cb97f99370356e3dbd
Requires: osmo-gsm-manuals.git Id344c29eda2a9b3e36376302b425e9db1f6c0f28

doc/manuals/chapters/qos-example.adoc

@@ -0,0 +1,44 @@
+==== Full example of QoS for osmo-pcu uplink QoS
+
+In the below example we will show the full set of configuration required
+for both DSCP and PCP differentiation of uplink Gb traffic by osmo-pcu.
+
+What we want to achieve in this example is the following configuration:
+
+.DSCP and PCP assignments for osmo-bts uplink traffic in this example
+[options="header",width="30%",cols="2,1,1"]
+|===
+|Traffic      |DSCP|PCP
+|Gb (NS)      |  10|  1
+|===
+
+. configure the osmocom program to set the DSCP value
+ * osmo-pcu.cfg: `dscp 10` in `udp bind` vty node
+. configure an egrees QoS map to map from priority to PCP
+
+.Example Step 1: add related VTY configuration to `osmo-pcu.cfg`
+----
+...
+pcu
+ gb ip-dscp 10
+ gb socket-priority 1
+ ...
+----
+
+.Example Step 2: egress QoS map to map from DSCP values to priority values
+----
+$ sudo ip link set dev eth0.9<1> type vlan egress-qos-map 0:0 1:1 5:5 6:6 7:7 <2>
+----
+<1> make sure to specify your specific VLAN interface name here instead of `eth0.9`.
+<2> create a egress QoS map that maps the priority value 1:1 to the PCP. We also
+    include the mappings for 5, 6, and 7 from the osmo-bts example here (see
+    <<userman-osmobts>>).
+
+NOTE:: The settings of the `ip` command are volatile and only active until
+the next reboot (or the network device or VLAN is removed).  Please refer to
+the documentation of your specific Linux distribution in order to find out how
+to make such settings persistent by means of an `ifup` hook whenever the interface
+comes up.  For CentOS/RHEL 8 this can e.g. be achieved by means of an `/sbin/ifup-local
+script` (when using `network-scripts` and not NetworkManager).  For Debian or Ubuntu,
+this typically involves adding `up` lines to `/etc/network/interfaces` or a `/etc/network/if-up.d`
+script.

doc/manuals/osmopcu-usermanual.adoc

@@ -21,6 +21,8 @@ include::{srcdir}/chapters/counters.adoc[]
 
 include::./common/chapters/gb.adoc[]
 
+include::./common/chapters/qos-dscp-pcp.adoc[]
+
 include::./common/chapters/vty_cpu_sched.adoc[]
 
 include::./common/chapters/port_numbers.adoc[]