Add documentation for Multihop GNB's deployment

Signed-off-by: Marikkannu, Suresh <[email protected]>

Author: sureshmarikkannu

dict.txt

@@ -25,6 +25,7 @@ GiB
 GigE
 GitOps
 Github
+GNB
 Grafana
 Haswell
 IPMI
@@ -47,6 +48,7 @@ Mbps
 Microservices
 Mininet
 Moto
+Multihop
 Multipass
 NAV
 Netbox
@@ -322,6 +324,7 @@ upf
 uplink
 uptime
 url
+usecase
 vfio
 virtualenv
 vpn

index.rst

@@ -24,6 +24,7 @@
    onramp/roc
    onramp/devel
    onramp/blueprints
+   onramp/deployments
 
 .. toctree::
    :maxdepth: 3

onramp/deployments.rst

@@ -0,0 +1,48 @@
+Deployment usecase's
+-----------------------
+
+This section documents various onramp deployment usecase's.
+
+Multihop GNB
+~~~~~~~~~~~~~~~~~~~~~~
+
+By default onramp uses isolated networks for the N3(ex: 192.168.252.x) and
+N6(ex: 192.168.250.x) interfaces. This prevents GNB(which is on different
+subnet and located multiple hops away) connecting to the UPF on N3 interface.
+
+In order to support such deployment onramp provides an option to configure
+N3 IP from the same subnet as DATA_IFACE. It can be enabled by setting
+``core.upf.multihop_gnb: true``
+
+For ex, lets say the DATA_IFACE subnet is 10.21.61.0/24 and GNB subnet
+is 10.202.1.0/24. Configure the parameters as follows,
+
+.. code-block::
+
+   data_iface: ens18
+   ran_subnet: "10.202.1.0/24"
+   upf:
+      access_subnet: "10.21.61.1/24"	# access subnet & gateway
+      core_subnet: "192.168.250.1/24"	# core subnet & gateway
+      multihop_gnb: true
+      default_upf:
+        ip:
+          access: "10.21.61.12" # when multihop_gnb set to true, make sure to assign IP from same subnet of data_iface
+          core:   "192.168.250.3"
+        ue_ip_pool: "172.250.0.0/16"
+
+In case if we need to connect multiple GNB's (GNB2 subnet: 10.203.1.0/24)
+from different subnet then add routes as follows
+in ``deps/5gc/roles/core/templates/sdcore-5g-values.yaml`` ``(if core.upf.mode: af_packet)``:
+in ``deps/5gc/roles/core/templates/sdcore-5g-sriov-values.yaml`` ``(if core.upf.mode: dpdk)``:
+
+.. code-block::
+
+   config:
+     upf:
+       routes:
+         - to: {{ ansible_default_ipv4.address }}
+           via: 169.254.1.1
+         - to: 10.203.1.0/24
+           via: 10.203.1.1
+