1 Service Function Chaining
2 =========================
4 OpenDaylight Service Function Chaining (SFC) Overview
5 -----------------------------------------------------
7 OpenDaylight Service Function Chaining (SFC) provides the ability to
8 define an ordered list of a network services (e.g. firewalls, load
9 balancers). These service are then "stitched" together in the network to
10 create a service chain. This project provides the infrastructure
11 (chaining logic, APIs) needed for ODL to provision a service chain in
12 the network and an end-user application for defining such chains.
14 - ACE - Access Control Entry
16 - ACL - Access Control List
18 - SCF - Service Classifier Function
20 - SF - Service Function
22 - SFC - Service Function Chain
24 - SFF - Service Function Forwarder
26 - SFG - Service Function Group
28 - SFP - Service Function Path
30 - RSP - Rendered Service Path
32 - NSH - Network Service Header
34 SFC Classifier Control and Date plane Developer guide
35 -----------------------------------------------------
40 Description of classifier can be found in:
41 https://datatracker.ietf.org/doc/draft-ietf-sfc-architecture/
43 Classifier manages everything from starting the packet listener to
44 creation (and removal) of appropriate ip(6)tables rules and marking
45 received packets accordingly. Its functionality is **available only on
46 Linux** as it leverages **NetfilterQueue**, which provides access to
47 packets matched by an **iptables** rule. Classifier requires **root
48 privileges** to be able to operate.
50 So far it is capable of processing ACL for MAC addresses, ports, IPv4
51 and IPv6. Supported protocols are TCP and UDP.
53 Classifier Architecture
54 ~~~~~~~~~~~~~~~~~~~~~~~
56 Python code located in the project repository
57 sfc-py/common/classifier.py.
61 classifier assumes that Rendered Service Path (RSP) **already
62 exists** in ODL when an ACL referencing it is obtained
64 1. sfc\_agent receives an ACL and passes it for processing to the
67 2. the RSP (its SFF locator) referenced by ACL is requested from ODL
69 3. if the RSP exists in the ODL then ACL based iptables rules for it are
72 After this process is over, every packet successfully matched to an
73 iptables rule (i.e. successfully classified) will be NSH encapsulated
74 and forwarded to a related SFF, which knows how to traverse the RSP.
76 Rules are created using appropriate iptables command. If the Access
77 Control Entry (ACE) rule is MAC address related both iptables and
78 IPv6 tables rules are issued. If ACE rule is IPv4 address related, only
79 iptables rules are issued, same for IPv6.
83 iptables **raw** table contains all created rules
85 Information regarding already registered RSP(s) are stored in an
86 internal data-store, which is represented as a dictionary:
90 {rsp_id: {'name': <rsp_name>,
91 'chains': {'chain_name': (<ipv>,),
96 'starting-index': <starting-index>,
97 'transport-type': <transport-type>
103 - ``name``: name of the RSP
105 - ``chains``: dictionary of iptables chains related to the RSP with
106 information about IP version for which the chain exists
108 - ``SFF``: SFF forwarding parameters
110 - ``ip``: SFF IP address
114 - ``starting-index``: index given to packet at first RSP hop
116 - ``transport-type``: encapsulation protocol
118 Key APIs and Interfaces
119 ~~~~~~~~~~~~~~~~~~~~~~~
121 This features exposes API to configure classifier (corresponds to
122 service-function-classifier.yang)
124 API Reference Documentation
125 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
127 See: sfc-model/src/main/yang/service-function-classifier.yang
135 SFC-OVS provides integration of SFC with Open vSwitch (OVS) devices.
136 Integration is realized through mapping of SFC objects (like SF, SFF,
137 Classifier, etc.) to OVS objects (like Bridge,
138 TerminationPoint=Port/Interface). The mapping takes care of automatic
139 instantiation (setup) of corresponding object whenever its counterpart
140 is created. For example, when a new SFF is created, the SFC-OVS plug-in
141 will create a new OVS bridge and when a new OVS Bridge is created, the
142 SFC-OVS plug-in will create a new SFF.
147 SFC-OVS uses the OVSDB MD-SAL Southbound API for getting/writing
148 information from/to OVS devices. The core functionality consists of two
151 a. mapping from OVS to SFC
153 - OVS Bridge is mapped to SFF
155 - OVS TerminationPoints are mapped to SFF DataPlane locators
157 b. mapping from SFC to OVS
159 - SFF is mapped to OVS Bridge
161 - SFF DataPlane locators are mapped to OVS TerminationPoints
163 .. figure:: ./images/sfc/sfc-ovs-architecture.png
164 :alt: SFC < — > OVS mapping flow diagram
166 SFC < — > OVS mapping flow diagram
168 Key APIs and Interfaces
169 ~~~~~~~~~~~~~~~~~~~~~~~
171 - SFF to OVS mapping API (methods to convert SFF object to OVS Bridge
172 and OVS TerminationPoints)
174 - OVS to SFF mapping API (methods to convert OVS Bridge and OVS
175 TerminationPoints to SFF object)
177 SFC Southbound REST Plug-in
178 --------------------------
183 The Southbound REST Plug-in is used to send configuration from datastore
184 down to network devices supporting a REST API (i.e. they have a
185 configured REST URI). It supports POST/PUT/DELETE operations, which are
186 triggered accordingly by changes in the SFC data stores.
188 - Access Control List (ACL)
190 - Service Classifier Function (SCF)
192 - Service Function (SF)
194 - Service Function Group (SFG)
196 - Service Function Schedule Type (SFST)
198 - Service Function Forwarder (SFF)
200 - Rendered Service Path (RSP)
202 Southbound REST Plug-in Architecture
203 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
205 1. **listeners** - used to listen on changes in the SFC data stores
207 2. **JSON exporters** - used to export JSON-encoded data from
208 binding-aware data store objects
210 3. **tasks** - used to collect REST URIs of network devices and to send
211 JSON-encoded data down to these devices
213 .. figure:: ./images/sfc/sb-rest-architecture.png
214 :alt: Southbound REST Plug-in Architecture diagram
216 Southbound REST Plug-in Architecture diagram
218 Key APIs and Interfaces
219 ~~~~~~~~~~~~~~~~~~~~~~~
221 The plug-in provides Southbound REST API designated to listening REST
222 devices. It supports POST/PUT/DELETE operations. The operation (with
223 corresponding JSON-encoded data) is sent to unique REST URL belonging to
226 - Access Control List (ACL):
227 ``http://<host>:<port>/config/ietf-acl:access-lists/access-list/``
229 - Service Function (SF):
230 ``http://<host>:<port>/config/service-function:service-functions/service-function/``
232 - Service Function Group (SFG):
233 ``http://<host>:<port>/config/service-function:service-function-groups/service-function-group/``
235 - Service Function Schedule Type (SFST):
236 ``http://<host>:<port>/config/service-function-scheduler-type:service-function-scheduler-types/service-function-scheduler-type/``
238 - Service Function Forwarder (SFF):
239 ``http://<host>:<port>/config/service-function-forwarder:service-function-forwarders/service-function-forwarder/``
241 - Rendered Service Path (RSP):
242 ``http://<host>:<port>/operational/rendered-service-path:rendered-service-paths/rendered-service-path/``
244 Therefore, network devices willing to receive REST messages must listen
249 Service Classifier Function (SCF) URL does not exist, because SCF is
250 considered as one of the network devices willing to receive REST
251 messages. However, there is a listener hooked on the SCF data store,
252 which is triggering POST/PUT/DELETE operations of ACL object,
253 because ACL is referenced in ``service-function-classifier.yang``
255 Service Function Load Balancing Developer Guide
256 -----------------------------------------------
261 SFC Load-Balancing feature implements load balancing of Service
262 Functions, rather than a one-to-one mapping between Service Function
263 Forwarder and Service Function.
265 Load Balancing Architecture
266 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
268 Service Function Groups (SFG) can replace Service Functions (SF) in the
269 Rendered Path model. A Service Path can only be defined using SFGs or
270 SFs, but not a combination of both.
272 Relevant objects in the YANG model are as follows:
274 1. Service-Function-Group-Algorithm:
278 Service-Function-Group-Algorithms {
279 Service-Function-Group-Algorithm {
287 Available types: ALL, SELECT, INDIRECT, FAST_FAILURE
289 2. Service-Function-Group:
293 Service-Function-Groups {
294 Service-Function-Group {
296 String serviceFunctionGroupAlgorithmName
299 Service-Function-Group-Element {
300 String service-function-name
306 3. ServiceFunctionHop: holds a reference to a name of SFG (or SF)
308 Key APIs and Interfaces
309 ~~~~~~~~~~~~~~~~~~~~~~~
311 This feature enhances the existing SFC API.
313 REST API commands include: \* For Service Function Group (SFG): read
314 existing SFG, write new SFG, delete existing SFG, add Service Function
315 (SF) to SFG, and delete SF from SFG \* For Service Function Group
316 Algorithm (SFG-Alg): read, write, delete
318 Bundle providing the REST API: sfc-sb-rest \* Service Function Groups
319 and Algorithms are defined in: sfc-sfg and sfc-sfg-alg \* Relevant JAVA
320 API: SfcProviderServiceFunctionGroupAPI,
321 SfcProviderServiceFunctionGroupAlgAPI
323 Service Function Scheduling Algorithms
324 --------------------------------------
329 When creating the Rendered Service Path (RSP), the earlier release of
330 SFC chose the first available service function from a list of service
331 function names. Now a new API is introduced to allow developers to
332 develop their own schedule algorithms when creating the RSP. There are
333 four scheduling algorithms (Random, Round Robin, Load Balance and
334 Shortest Path) are provided as examples for the API definition. This
335 guide gives a simple introduction of how to develop service function
336 scheduling algorithms based on the current extensible framework.
341 The following figure illustrates the service function selection
342 framework and algorithms.
344 .. figure:: ./images/sfc-sf-selection-arch.png
345 :alt: SF Scheduling Algorithm framework Architecture
347 SF Scheduling Algorithm framework Architecture
349 The YANG Model defines the Service Function Scheduling Algorithm type
350 identities and how they are stored in the MD-SAL data store for the
351 scheduling algorithms.
353 The MD-SAL data store stores all informations for the scheduling
354 algorithms, including their types, names, and status.
356 The API provides some basic APIs to manage the informations stored in
357 the MD-SAL data store, like putting new items into it, getting all
358 scheduling algorithms, etc.
360 The RESTCONF API provides APIs to manage the informations stored in the
361 MD-SAL data store through RESTful calls.
363 The Service Function Chain Renderer gets the enabled scheduling
364 algorithm type, and schedules the service functions with scheduling
365 algorithm implementation.
367 Key APIs and Interfaces
368 ~~~~~~~~~~~~~~~~~~~~~~~
370 While developing a new Service Function Scheduling Algorithm, a new
371 class should be added and it should extend the base schedule class
372 SfcServiceFunctionSchedulerAPI. And the new class should implement the
375 ``public List<String> scheduleServiceFuntions(ServiceFunctionChain chain, int serviceIndex)``.
377 - **``ServiceFunctionChain chain``**: the chain which will be rendered
379 - **``int serviceIndex``**: the initial service index for this rendered
382 - **``List<String>``**: a list of service function names which scheduled
383 by the Service Function Scheduling Algorithm.
385 API Reference Documentation
386 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
388 Please refer the API docs generated in the mdsal-apidocs.
391 Logical Service Function Forwarder
392 ----------------------------------
400 When the current SFC is deployed in a cloud environment, it is assumed that each
401 switch connected to a Service Function is configured as a Service Function Forwarder and
402 each Service Function is connected to its Service Function Forwarder depending on the
403 Compute Node where the Virtual Machine is located. This solution allows the basic cloud
404 use cases to be fulfilled, as for example, the ones required in OPNFV Brahmaputra, however,
405 some advanced use cases, like the transparent migration of VMs can not be implemented.
406 The Logical Service Function Forwarder enables the following advanced use cases:
408 1. Service Function mobility without service disruption
409 2. Service Functions load balancing and failover
411 As shown in the picture below, the Logical Service Function Forwarder concept extends the current
412 SFC northbound API to provide an abstraction of the underlying Data Center infrastructure.
413 The Data Center underlaying network can be abstracted by a single SFF. This single SFF uses
414 the logical port UUID as data plane locator to connect SFs globally and in a location-transparent manner.
415 SFC makes use of Genius project to track the location of the SF's logical ports.
417 .. figure:: ./images/sfc/single-logical-sff-concept.png
418 :alt: Single Logical SFF concept
420 The SFC internally distributes the necessary flow state over the relevant switches based on the
421 internal Data Center topology and the deployment of SFs.
423 Changes in data model
424 ~~~~~~~~~~~~~~~~~~~~~
425 The Logical Service Function Forwarder concept extends the current SFC northbound API to provide
426 an abstraction of the underlying Data Center infrastructure.
428 The Logical SFF simplifies the configuration of the current SFC data model by reducing the number
429 of parameters to be be configured in every SFF, since the controller will discover those parameters
430 by interacting with the services offered by the Genius project.
432 The following picture shows the Logical SFF data model. The model gets simplified as most of the
433 configuration parameters of the current SFC data model are discovered in runtime. The complete
434 YANG model can be found here `logical SFF model
435 <https://github.com/opendaylight/sfc/blob/master/sfc-model/src/main/yang/service-function-forwarder-logical.yang>`__.
437 .. figure:: ./images/sfc/logical-sff-datamodel.png
438 :alt: Logical SFF data model
440 There are other minor changes in the data model; the SFC encapsulation type has been added or moved in the following files:
442 - `RSP data model <https://github.com/opendaylight/sfc/blob/master/sfc-model/src/main/yang/rendered-service-path.yang>`__
444 - `SFP data model <https://github.com/opendaylight/sfc/blob/master/sfc-model/src/main/yang/service-function-path.yang>`__
446 - `Service Locator data model <https://github.com/opendaylight/sfc/blob/master/sfc-model/src/main/yang/service-locator.yang>`__
448 Interaction with Genius
449 ~~~~~~~~~~~~~~~~~~~~~~~
450 As shown in the following picture, SFC will interact with Genius project's services to provide the
451 Logical SFF functionality.
453 .. figure:: ./images/sfc/sfc-genius-interaction.png
456 The following are the main Genius' services used by SFC:
458 1. Interaction with Interface Tunnel Manager (ITM)
460 2. Interaction with the Interface Manager
462 3. Interaction with Resource Manager