L3VPN use case and images

Change-Id: Ib2820c5f729a4f37de04d4e088a636e4478136e9
Signed-off-by: Bin Hu <bh526r@att.com>

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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+.. (c) Bin Hu
+
+L3VPN Use Cases
+===============
+
+Service Providers' virtualized network infrastructure may consist of one or more
+SDN Controllers from different vendors. Those SDN Controllers may be managed
+within one cloud or multiple clouds. Jointly, those VIMs (e.g. OpenStack instances)
+and SDN Controllers work together in an interoperable framework to create L3 services
+in Service Providers' virtualized network infrastructure.
+
+Three use cases of creating L3VPN service by multiple SDN Controllers are described
+as follows.
+
+Any-to-Any Base Case
+--------------------
+
+Description
+~~~~~~~~~~~
+
+There are 2 hosts (compute nodes). SDN Controller A and vRouter A are provided by
+Vendor A, and run on host A. SDN Controller B and vRouter B are provided by
+Vendor B, and run on host B.
+
+There are 2 tenants. Tenant 1 creates L3VPN Blue with 2 subnets: 10.1.1.0/24 and 10.3.7.0/24.
+Tenant 2 creates L3VPN Red with 1 subnet, overlapping address space: 10.1.1.0/24.
+
+The network topology is shown in :numref:`l3vpn-any2any-figure`:
+
+.. figure:: images/l3vpn-any2any.png
+   :name:  l3vpn-any2any-figure
+   :width: 100%
+
+In L3VPN Blue, VMs G1 (10.1.1.5) and G2 (10.3.7.9) are spawned on host A, and attached to 2 subnets
+(10.1.1.0/24 and 10.3.7.0/24) and assigned IP addresses respectively. VMs G3 (10.1.1.6) and
+G4 (10.3.7.10) are spawned on host B, and attached to 2 subnets (10.1.1.0/24 and 10.3.7.0/24)
+and assigned IP addresses respectively.
+
+In L3VPN Red, VM G5 (10.1.1.5) is spawned on host A, and attached to subnet 10.1.1.0/24. VM G6
+(10.1.1.6) is spawned on host B, and attached to the same subnet 10.1.1.0/24.
+
+Exemplary workflow is described as follows:
+
+1. Create Network
+2. Create Network VRF Policy Resource ``Any-to-Any``
+2.1. This sets up that when this tenant is put on a HOST that:
+2.1.1. There will be a RD assigned per VRF
+2.1.2. There will be a RT used for the common any-to-any communication
+3. Create Subnet
+4. Create Port (subnet, network vrf policy resource). This causes controller to:
+4.1. Create vrf in vRouter's FIB, or Update vrf if already exists
+4.2. Install an entry for Guest's HOST-Route in FIBs of Vrouters serving this tenant Virtual Network
+4.3. Announce Guest HOST-Route to WAN-GW via MP-BGP
+
+VRF Lets us do:
+1. Overlapping Addresses
+2. Segregation of Traffic
+
+Derrived Requirements
+~~~~~~~~~~~~~~~~~~~~~
+   - TBD
+
+Northbound API / Workflow
++++++++++++++++++++++++++
+   - TBD
+
+Data model objects
+++++++++++++++++++
+   - TBD
+
+Orchestration
++++++++++++++
+   - TBD
+
+Dependencies on compute services
+++++++++++++++++++++++++++++++++
+   - TBD
+
+Potential implementation
+++++++++++++++++++++++++
+   - TBD
+
+
+ECMP Load Splitting Case (Anycast)
+----------------------------------
+
+Description
+~~~~~~~~~~~
+
+There are 2 hosts (compute nodes). SDN Controller A and vRouter A are provided by
+Vendor A, and run on host A. SDN Controller B and vRouter B are provided by
+Vendor B, and run on host B.
+
+There is 1 tenant. Tenant 1 creates L3VPN Blue with subnet 10.1.1.0/24.
+
+The network topology is shown in :numref:`l3vpn-ecmp-figure`:
+
+.. figure:: images/l3vpn-ecmp.png
+   :name:  l3vpn-ecmp-figure
+   :width: 100%
+
+In L3VPN Blue, VNF1.1 and VNF1.2 are spawned on host A, attached to subnet 10.1.1.0/24
+and assigned the same IP address 10.1.1.5. VNF1.3 is spawned on host B, attached to
+subnet 10.1.1.0/24 and assigned the same IP addresses 10.1.1.5. VNF 2 and VNF 3 are spawned
+on host A and B respectively, attached to subnet 10.1.1.0/24, and assigned different IP
+addresses 10.1.1.6 and 10.1.1.3 respectively.
+
+Here, the Network VRF Policy Resource is ``ECMP/AnyCast``. Traffic to **Anycast 10.1.1.5**
+can be load split from either WAN GW or another VM like G5.
+
+
+Derrived Requirements
+~~~~~~~~~~~~~~~~~~~~~
+   - TBD
+
+Northbound API / Workflow
++++++++++++++++++++++++++
+   - TBD
+
+Data model objects
+++++++++++++++++++
+   - TBD
+
+Orchestration
++++++++++++++
+   - TBD
+
+Dependencies on compute services
+++++++++++++++++++++++++++++++++
+   - TBD
+
+Potential implementation
+++++++++++++++++++++++++
+   - TBD
+
+
+Hub and Spoke Case
+------------------
+
+Description
+~~~~~~~~~~~
+
+There are 2 hosts (compute nodes). SDN Controller A and vRouter A are provided by
+Vendor A, and run on host A. SDN Controller B and vRouter B are provided by
+Vendor B, and run on host B.
+
+There is 1 tenant. Tenant 1 creates L3VPN Blue with 2 subnets: 10.1.1.0/24 and 10.3.7.0/24.
+
+The network topology is shown in :numref:`l3vpn-hub-spoke-figure`:
+
+.. figure:: images/l3vpn-hub-spoke.png
+   :name:  l3vpn-hub-spoke-figure
+   :width: 100%
+
+In L3VPN Blue, vFW(H) is acting the role of ``hub`` (a virtual firewall).
+The other 3 VNFsVMs are ``spoke``. vFW(H) and VNF1(S) are spawned on host A,
+and VNF2(S) and VNF3(S) are spawned on host B. vFW(H) (10.1.1.5) and VNF2(S)
+(10.1.1.6) are attached to subnet 10.1.1.0/24. VNF1(S) (10.3.7.9) and VNF3(S)
+(10.3.7.10) are attached to subnet 10.3.7.0/24.
+
+Exemplary vFW(H) Hub VRF is as follows:
+
+* RD1 10.1.1.5  IP_OVR1 Label1
+* RD1 0/0 IP_OVR1 Label1
+* Label 1 Local IF (10.1.1.5)
+* RD3 10.3.7.9  IP_OVR1 Label2
+* RD2 10.1.1.6  IP_OVR2 Label3
+* RD4 10.3.7.10 IP_OVR2 Label3
+
+Exemplary VNF1(S) Spoke VRF is as follows:
+
+* RD1 0/0 IP_OVR1 Label1
+* RD3 10.3.7.9  IP_OVR1 Label2
+
+Exemplary workflow is described as follows:
+
+1. Create Network
+2. Create VRF Policy Resource
+2.1. Hub and Spoke
+3. Create Subnet
+4. Create Port
+4.1. Subnet
+4.2. VRF Policy Resource, [H | S]
+
+
+Derrived Requirements
+~~~~~~~~~~~~~~~~~~~~~
+   - TBD
+
+Northbound API / Workflow
++++++++++++++++++++++++++
+   - TBD
+
+Data model objects
+++++++++++++++++++
+   - TBD
+
+Orchestration
++++++++++++++
+   - TBD
+
+Dependencies on compute services
+++++++++++++++++++++++++++++++++
+   - TBD
+
+Potential implementation
+++++++++++++++++++++++++
+   - TBD
+
+