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Diffstat (limited to 'docs/requirements/use_cases')
| -rw-r--r-- | docs/requirements/use_cases/l3vpn_hub_and_spoke.rst | 198 |
1 files changed, 150 insertions, 48 deletions
diff --git a/docs/requirements/use_cases/l3vpn_hub_and_spoke.rst b/docs/requirements/use_cases/l3vpn_hub_and_spoke.rst index 73ec4c2..a000046 100644 --- a/docs/requirements/use_cases/l3vpn_hub_and_spoke.rst +++ b/docs/requirements/use_cases/l3vpn_hub_and_spoke.rst @@ -8,9 +8,20 @@ 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. +A Hub-and-spoke topology comprises two types of network entities: a central hub +and multiple spokes. The corresponding VRFs of the hub and the spokes are +configured to import and export routes such that all traffic is routed through +the hub. As a result, spokes cannot communicate with each other directly, but +only indirectly via the central hub. Hence, the hub typically hosts central network +functions such firewalls. + +Furthermore, there is no layer 2 connectivity between the VNFs. + +In addition, in this use case, the deployed network infrastructure comprises +equipment from two different vendors, Vendor A and Vendor B. 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. @@ -21,17 +32,20 @@ The network topology is shown in :numref:`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, +The other 3 VNF VMs 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. -Derrived Requirements + +Derived Requirements ~~~~~~~~~~~~~~~~~~~~~ Northbound API / Workflow +++++++++++++++++++++++++ +[**Georg: this needs to be made more readable / explanatory**] + Exemplary vFW(H) Hub VRF is as follows: * RD1 10.1.1.5 IP_OVR1 Label1 @@ -62,24 +76,19 @@ Exemplary workflow is described as follows: 4.2. VRF Policy Resource, [H | S] + Data model objects ++++++++++++++++++ - TBD -Orchestration -+++++++++++++ - - TBD - -Dependencies on compute services -++++++++++++++++++++++++++++++++ - - TBD Current implementation ++++++++++++++++++++++ -Different APIs have been developed to support creating a network topology and directing -network traffic through specific network elements in specific order, for example, [BGPVPN]_ -and [NETWORKING-SFC]_. We analyzed those APIs regarding the Hub-and-Spoke use case. +Different APIs have been developed to support creating a L3 network topology and +directing network traffic through specific network elements in specific order, +for example, [BGPVPN]_ and [NETWORKING-SFC]_. We analyzed those APIs regarding +the Hub-and-Spoke use case. BGPVPN @@ -90,16 +99,33 @@ Neutron by means of the BGPVPN API [BGPVPN]_. However, the [BGPVPN]_ API does not support creating the Hub-and-Spoke topology as outlined above, i.e. setting up specific VRFs of vFW(H) and other VNFs(S) within one L3VPN to direct the traffic from vFW(H) to VNFs(S). +[**Georg: I'd like to move the last statement further down as this is already a +conclusion without having done any kind of analysis.**] The [BGPVPN]_ API currently supports the concepts of network- and -router-associations. An association in principle maps to a VRF that -interconnects either subnets of a Neutron network (network association) or the -networks connected by a router (router association). It does not yet allow for -creating VRFs per VM port (port associations) as illustrated in Hub-and-Spoke use case. -The functionality of port association is needed, however, to create separate VRFs per VM -in order to implement the Hub-and-Spoke use case. Furthermore, the functionality of setting -up next-hop routing table, labels, I-RT and E-RT etc in VRF is also required to enable -traffic direction from Hub to Spokes. +router-associations. An association maps Neutron network objects (networks and +routers) to a VRF with the following semantics: + +* A *network association* interconnects all subnets and ports of a Neutron + network by binding them to a given VRF +* a *router association* interconnects all networks, and hence indirectly all + ports, connected to a Neutron router by binding them to a given VRF + +It is important to notice that these associations apply to entire Neutron +networks including all ports connected to a network. This is due to the fact +that in the Neutron, ports can only exist within a network but not individually. +Furthermore, Neutron networks were originally designed to represent layer 2 +domains. As a result, ports within the same Neutron network typically have layer +connectivity among each other. There are efforts to relax this original design +assumption, e.g. routed networks, which however do not solve the problem at hand +here (see the gap analysis further down below). + +In order to realize the hub-and-spoke topology outlined above, VRFs need to be +created on a per port basis. Specifically, ports belonging to the same network +should not be interconnected except through a corresponding configuration of a +per-port-VRF. This configuration includes setting up next-hop routing table, +labels, I-RT and E-RT etc. in order to enable traffic direction from hub to +spokes. It may be argued that given the current network- and router-association mechanisms, the following workflow establishes a network topology which aims to achieve the desired @@ -108,32 +134,56 @@ by creating a dedicated Neutron network with two subnets for each VRF in the Hub-and-Spoke topology. 1. Create Neutron network "hub" - :code:`neutron net-create hub` + ``neutron net-create --tenant-id Blue hub`` + 2. Create a separate Neutron network for every "spoke" - :code:`neutron net-create spoke-i` + ``neutron net-create --tenant-id Blue spoke-i`` + 3. For every network (hub and spokes), create two subnets - :code:`neutron subnet-create <hub/spoke-i network UUID> 10.1.1.0/24` - :code:`neutron subnet-create <hub/spoke-i network UUID> 10.3.7.0/24` + ``neutron subnet-create <hub/spoke-i UUID> --tenant-id Blue 10.1.1.0/24`` -4. Create a BGPVPN object (VRF) for the hub network with the corresponding import + ``neutron subnet-create <hub/spoke-i UUID> --tenant-id Blue 10.3.7.0/24`` + + +4. Create the Neutron ports in the corresponding networks + ``neutron port-create --tenant-id Blue --name vFW(H) --fixed-ip subnet_id=<hub UUID>,ip_address=10.1.1.5`` + + ``neutron port-create --tenant-id Blue --name VNF1(S) --fixed-ip subnet_id=<spoke-i UUID>,ip_address=10.3.7.9`` + + ``neutron port-create --tenant-id Blue --name VNF2(S) --fixed-ip subnet_id=<spoke-i UUID>,ip_address=10.1.1.6`` + + ``neutron port-create --tenant-id Blue --name VNF3(S) --fixed-ip subnet_id=<spoke-i UUID>,ip_address=10.3.7.10`` + + +5. Create a BGPVPN object (VRF) for the hub network with the corresponding import and export targets - :code:`neutron bgpvpn-create --name hub-vrf --import-targets <RT-hub RT-spoke> --export-targets <RT-hub>` + ``neutron bgpvpn-create --name hub-vrf --import-targets <RT-hub RT-spoke> --export-targets <RT-hub>`` -5. Create a BGPVPN object (VRF) for every spoke network with the corresponding import + +6. Create a BGPVPN object (VRF) for every spoke network with the corresponding import and export targets - :code:`neutron bgpvpn-create --name spoke-i-vrf --import-targets <RT-hub> --export-targets <RT-spoke>` + ``neutron bgpvpn-create --name spoke-i-vrf --import-targets <RT-hub> --export-targets <RT-spoke>`` + -6. Associate the hub network with the hub VRF - :code:`bgpvpn-net-assoc-create hub --network <hub network-UUID>` +7. Associate the hub network with the hub VRF + ``bgpvpn-net-assoc-create hub --network <hub network-UUID>`` -7. Associate each spoke network with the corresponding spoke VRF - :code:`bgpvpn-net-assoc-create spoke-i --network <spoke-i network-UUID>` -After step 7, VMs can be booted on the corresponding networks. +8. Associate each spoke network with the corresponding spoke VRF + ``bgpvpn-net-assoc-create spoke-i --network <spoke-i network-UUID>`` -The resulting network topology tries to resemble our target topology as shown in + +9. Add static route to direct all traffic to vFW VNF running at the hub. + + **Note:** Support for static routes not yet available. + + ``neutron bgpvpn-static-route-add --tenant-id Blue --cidr 0/0 --nexthop-ip 10.1.1.5 hub`` + +After step 9, VMs can be booted with the corresponding ports. + +The resulting network topology intents to resemble the target topology as shown in :numref:`l3vpn-hub-spoke-figure`, and achieve the desired traffic direction from Hub to Spoke. However, it deviates significantly from the essence of the Hub-and-Spoke use case as described above in terms of desired network topology, i.e. one L3VPN with multiple @@ -143,6 +193,7 @@ number of Spokes, and in case of scale-in and scale-out of Hub and Spokes. The gap analysis in the next section describes the technical reasons for this. + Network SFC ''''''''''' @@ -154,24 +205,75 @@ or not the service chain from vFW(H) to VNFs(S) can be created in the way of L3V VRF policy approach using [NETWORKING-SFC]_ API. Hence, it is currently not possible to configure the networking use case as described above. +**Georg: we need to look deeper into SFC to substantiate our claim here.** + -Gaps in Current Solution -++++++++++++++++++++++++ +Gaps in the Current Solution +++++++++++++++++++++++++++++ Given the use case description and the currently available implementation in OpenStack provided by [BGPVPN]_ project and [NETWORKING-SFC]_ project, we identify the following gaps: -* [L3VPN-HS-GAP1] The [BGPVPN]_ project lacks port-associations - The workflow described above intents to mimic port associations by means of - separate Neutron networks. Hence, the resulting workflow is overly complicated - and not intuitive by requiring to create additional Neutron entities - (networks) which are not present in the target topology. This method is also not scalable. +[L3VPN-HS-GAP1] No means to disable layer 2 semantic of Neutron networks +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +Neutron networks were originally designed to represent layer 2 broadcast +domains. As such, all ports connected to a network are in principle +inter-connected on layer 2 (not considering security rules here). In contrast, +in order to realize L3VPN use cases such as the hub-and-spoke topology, +connectivity among ports must be controllable on a per port basis on layer 3. + +There are ongoing efforts to relax this design assumption, for instance by means +of routed networks ([NEUTRON-ROUTED-NETWORKS]_). In a routed network, a Neutron network +is a layer 3 domain which is composed of multiple layer 2 segments. A routed +network only provides layer 3 connectivity across segments, but layer 2 +connectivity across segments is **optional**. This means, depending on the +particular networking backend and segmentation technique used, there might be +layer 2 connectivity across segments or not. A new flag ``l2_adjacency`` +indicates whether or not a user can expect layer 2 connectivity or not across +segments. + +This flag, however, is ready-only and cannot be used to overwrite or disable the +layer 2 semantics of a Neutron network. + + +[L3VPN-HS-GAP2] No port-association available in the BGPVPN project yet +''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +Due to gap [L3VPN-HS-GAP1], the [BGPVPN]_ project was not yet able to implement +the concept of a port association. A port association would allow to associate +individual ports with VRFs and thereby control layer 3 connectivity on a per +port basis. + +The workflow described above intents to mimic port associations by means of +separate Neutron networks. Hence, the resulting workflow is overly complicated +and not intuitive by requiring to create additional Neutron entities (networks) +which are not present in the target topology. Moreover, creating large numbers +of Neutron networks limits scalability. + +Port associations are on the road map of the [BGPVPN]_ project, however, no +design that overcomes the problems outlined above has been specified yet. +Consequently, the time-line for this feature is unknown. + +As a result, creating a clean Hub-and-Spoke topology is current not yet +supported by the [BGPVPN]_ API. + + +[L3VPN-HS-GAP3] No support for static routes in the BGPVPN project yet +'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +In order to realize the hub-and-spoke use case, a static route is needed to +attract the traffic at the hub to the corresponding VNF (direct traffic to the +firewall). Support for static routes in the BGPVPN project is available for the +router association by means of the Neutron router extra routes feature. However, +there is no support for static routes for network and port associations yet. - Within the [BGPVPN]_ project, design work on port-association has started. The - timeline for this feature is however not defined yet. As a result, creating a - clean Hub-and-Spoke topology is current not yet supported by the [BGPVPN]_ API. +Design work for supporting static routes for network associations has started, +but no final design has been proposed yet. -* [L3VPN-HS-GAP2] Creating a clean hub-and-spoke topology is current not yet supported by the [NETWORKING-SFC]_ API. +.. +.. [L3VPN-HS-GAP4] Creating a clean hub-and-spoke topology is current not yet supported by the NETWORKING-SFC API. +.. [Georg: We need to look deeper into SFC before we can substantiate our claim] |