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diff --git a/docs/requirements/use_cases/service_binding_pattern.rst b/docs/requirements/use_cases/service_binding_pattern.rst deleted file mode 100644 index 8abcf7a..0000000 --- a/docs/requirements/use_cases/service_binding_pattern.rst +++ /dev/null @@ -1,198 +0,0 @@ -.. This work is licensed under a Creative Commons Attribution 4.0 International License. -.. http://creativecommons.org/licenses/by/4.0 -.. (c) Georg Kunz - - -Service Binding Design Pattern ------------------------------- - -Description -^^^^^^^^^^^ - -This use case aims at binding multiple networks or network services to a single -vNIC (port) of a given VM. There are several specific application scenarios for -this use case: - -* Shared Service Functions: A service function connects to multiple networks of - a tenant by means of a single vNIC. - - Typically, a vNIC is bound to a single network. Hence, in order to directly - connect a service function to multiple networks at the same time, multiple vNICs - are needed - each vNIC binds the service function to a separate network. For - service functions requiring connectivity to a large number of networks, this - approach does not scale as the number of vNICs per VM is limited and additional - vNICs occupy additional resources on the hypervisor. - - A more scalable approach is to bind multiple networks to a single vNIC - and let the service function, which is now shared among multiple networks, - handle the separation of traffic itself. - - -* Multiple network services: A service function connects to multiple different - network types such as a L2 network, a L3(-VPN) network, a SFC domain or - services such as DHCP, IPAM, firewall/security, etc. - - -In order to achieve a flexible binding of multiple services to vNICs, a logical -separation between a vNIC (instance port) - that is, the entity that is used by -the compute service as hand-off point between the network and the VM - and a -service interface - that is, the interface a service binds to - is needed. - -Furthermore, binding network services to service interfaces instead of to the -vNIC directly enables a more dynamic management of the network connectivity of -network functions as there is no need to add or remove vNICs. - - -Requirements -^^^^^^^^^^^^ - -Data model -"""""""""" - -This section describes a general concept for a data model and a corresponding -API. It is not intended that these entities are to be implemented exactly as -described. Instead, they are meant to show a design pattern for future network -service models and their corresponding APIs. For example, the "service" entity -should hold all required attributes for a specific service, for instance a given -L3VPN service. Hence, there would be no entity "service" but rather "L3VPN". - - -* ``instance-port`` - - An instance port object represents a vNIC which is bindable to an OpenStack - instance by the compute service (Nova). - - *Attributes:* Since an instance-port is a layer 2 device, its attributes - include the MAC address, MTU and others. - - -* ``interface`` - - An interface object is a logical abstraction of an instance-port. It allows to - build hierarchies of interfaces by means of a reference to a parent interface. - Each interface represents a subset of the packets traversing a given port or - parent interface after applying a layer 2 segmentation mechanism specific to the - interface type. - - *Attributes:* The attributes are specific to the type of interface. - - *Examples:* trunk interface, VLAN interface, VxLAN interface, MPLS interface - - -* ``service`` - - A service object represents a specific networking service. - - *Attributes:* The attributes of the service objects are service specific and - valid for given service instance. - - *Examples:* L2, L3VPN, SFC - - -* ``service-port`` - - A service port object binds an interface to a service. - - *Attributes:* The attributes of a service-port are specific for the bound - service. - - *Examples:* port services (IPAM, DHCP, security), L2 interfaces, L3VPN - interfaces, SFC interfaces. - - - -Northbound API -"""""""""""""" - -An exemplary API for manipulating the data model is described below. As for the -data model, this API is not intended to be a concrete API, but rather an example -for a design pattern that clearly separates ports from services and service -bindings. - -* ``instance-port-{create,delete} <name>`` - - Creates or deletes an instance port object that represents a vNIC in a VM. - - -* ``interface-{create,delete} <name> [interface type specific parameters]`` - - Creates or deletes an interface object. - - -* ``service-{create,delete} <name> [service specific parameters]`` - - Create a specific service object, for instance a L3VPN, a SFC domain, or a L2 network. - - -* ``service-port-{create,delete} <service-id> <interface-id> [service specific parameters]`` - - Creates a service port object, thereby binding an interface to a given service. - - - -Orchestration -""""""""""""" - -None. - - -Dependencies on other resources -""""""""""""""""""""""""""""""" - -The compute service needs to be enabled to consume instance ports instead of -classic Neutron ports. - - -Current Implementation -^^^^^^^^^^^^^^^^^^^^^^ - -The core Neutron API does not follow the service binding design pattern. For -example, a port has to exist in a Neutron network - specifically it has to be -created for a particular Neutron network. It is not possible to create just a -port and assign it to a network later on as needed. As a result, a port cannot -be moved from one network to another, for instance. - -Regarding the shared service function use case outlined above, there is an -ongoing activity in Neutron [VLAN-AWARE-VMs]_. The solution proposed by this -activity allows for creating a trunk-port and multiple sub-ports per Neutron -port which can be bound to multiple networks (one network per sub-port). This -allows for binding a single VNIC to multiple networks and allow the -corresponding VMs to handle the network segmentation (VLAN tagged traffic) -itself. While this is a step in the direction of binding multiple services -(networks) to a port, it is limited by the fundamental assumption of Neutron -that a port has to exist on a given network. - -There are extensions of Neutron that follow the service binding design pattern -more closely. An example is the BGPVPN project. A rough mapping of the service -binding design pattern to the data model of the BGPVPN project is as follows: - -* instance-port -> Neutron port - -* service -> VPN - -* service-port -> network association - -This example shows that extensions of Neutron can in fact follow the described -design pattern in their respective data model and APIs. - - - -Conclusions -^^^^^^^^^^^ - -In conclusion, the design decisions taken for the core Neutron API and data -model do not follow the service binding model. As a result, it is hard to -implement certain use cases which rely on a flexible binding of services to -ports. Due to the backwards compatibility to the large amount of existing -Neutron code, it is unlikely that the core Neutron API will adapt to this design -pattern. - -New extension to Neutron however are relatively free to choose their data model -and API - within the architectural boundaries of Neutron of course. In order to -provide the flexibility needed, extensions shall aim for following the service -binding design pattern if possible. - -For the same reason, new networking frameworks complementing Neutron, such as -Gluon, shall follow this design pattern and create the foundation for -implementing networking services accordingly. - |