From b71d64b9375bea76cc07b4cb24d22b94a9bc9da0 Mon Sep 17 00:00:00 2001 From: Georg Kunz Date: Tue, 12 Jul 2016 15:50:32 +0200 Subject: Renamed and extended port abstraction model The former port abstraction use case has been rename (again) to better highlight that it represents a design pattern for APIs and data models. In line with this, the text has been extended. Change-Id: I49c3f153dc7b75b000acacd8436b41d9d1219e2a Signed-off-by: Georg Kunz --- docs/requirements/use_cases/port_abstraction.rst | 140 --------------- .../use_cases/service-binding-pattern.rst | 199 +++++++++++++++++++++ 2 files changed, 199 insertions(+), 140 deletions(-) delete mode 100644 docs/requirements/use_cases/port_abstraction.rst create mode 100644 docs/requirements/use_cases/service-binding-pattern.rst (limited to 'docs/requirements/use_cases') diff --git a/docs/requirements/use_cases/port_abstraction.rst b/docs/requirements/use_cases/port_abstraction.rst deleted file mode 100644 index 8f6e791..0000000 --- a/docs/requirements/use_cases/port_abstraction.rst +++ /dev/null @@ -1,140 +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 - - -Port Abstraction ----------------- - -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 binding 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 -"""""""""" - -The envisioned data model of the port abstraction model is as follows: - -* ``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 (TBD). - - -* ``interface`` - - An interface object is a logical abstraction of an instance-port. It allows to - build hierachies 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 -"""""""""""""" - -The API for manipulating the data model is as follows: - -* ``instance-port-{create,delete} `` - - Creates or deletes an instance port object that represents a vNIC in a VM. - - -* ``interface-{create,delete} [interface type specific parameters]`` - - Creates or deletes an interface object. - - -* ``service-{create,delete} [service specific parameters]`` - - Create a specific service object, for instance a L3VPN, a SFC domain, or a L2 network. - - -* ``service-port-{create,delete} [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. - - -Implementation Proposal -^^^^^^^^^^^^^^^^^^^^^^^ - -TBD diff --git a/docs/requirements/use_cases/service-binding-pattern.rst b/docs/requirements/use_cases/service-binding-pattern.rst new file mode 100644 index 0000000..5b288bd --- /dev/null +++ b/docs/requirements/use_cases/service-binding-pattern.rst @@ -0,0 +1,199 @@ +.. 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 binding 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 (TBD). + + +* ``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} `` + + Creates or deletes an instance port object that represents a vNIC in a VM. + + +* ``interface-{create,delete} [interface type specific parameters]`` + + Creates or deletes an interface object. + + +* ``service-{create,delete} [service specific parameters]`` + + Create a specific service object, for instance a L3VPN, a SFC domain, or a L2 network. + + +* ``service-port-{create,delete} [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 [**describe what is meant by that**] 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. + -- cgit 1.2.3-korg