Webinar: Applying REST to Network Management – An Implementor’s View


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This webinar gives an introduction to the principles of REST, shows how it can be used to expose programmable APIs on network elements and provides some real world examples from our implementation.

The principles of Representational State Transfer (REST) have gained a strong following since they were described by Roy Fielding in his doctoral dissertation written in 2000. REST’s strength lies in its scalability and generality, allowing it to be used for many types of applications.

The industry has already seen a number of implementations of network management applications that use REST interfaces on the infrastructure management layer, notably OpenStack Quantum and the Sun Cloud API. As a vendor to the vendors, we’ve seen a significant increase in interest around having REST interfaces exposed directly on the network element, be they hardware based or virtual.


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Webinar: Applying REST to Network Management – An Implementor’s View

  1. 1. Applying REST to Network Management;An Implementor’s ViewCarl Moberg, VP Technologycalle@tail-f.com @cmobergConfidential Information | December 18, 2012
  2. 2. Agenda•  Background and Overview of REST•  REST in a Network Management Context•  Introducing Data Models•  Putting it all Together•  A Short DemoConfidential Information | December 18, 2012 1
  3. 3. A Brief History of REST•  Fielding, R. T. (2000) Architectural Styles and the Design of Network-based Software Architectures•  Many called, few are chosen•  An architectural style... but we digressConfidential Information | December 18, 2012 2
  4. 4. Which Way to Slice This?•  The REST Architectural Style describes six constraints: –  Uniform interface, Stateless, Cacheable, Client-server, Layered System, Code on demand (optional)•  Guiding principles for of a REST interface (the Uniform Interface constraints): –  Resources have unique identifiers (e.g. URIs) –  Manipulations of resources through representations –  Self-descriptive Messages –  Hypermedia as the engines of application state (HATEOAS)Confidential Information | December 18, 2012 3
  5. 5. Resources Have Unique Identifiers (e.g. URIs)GET /api/running/interfaces/interface/eth0/ipv4 HTTP/1.1!!<ipv4 y:self="/api/running/interfaces/interface/eth0/ip:ipv4”>! <address y:self=”[...]">! <ip></ip>!...!!•  Individual resources are identified in requests using URIs•  Resources are conceptually separate from the representations•  Resource representations depend on query and server support (e.g. XML and JSON)Confidential Information | December 18, 2012 4
  6. 6. Manipulation of Representations < Content-Type: application/vnd.yang.data+xml! ! <ipv4 y:self="/api/running/interfaces/interface/eth0/ip:ipv4”>! <address y:self=”[...]">! <ip></ip>! </address>! </ipv4>!•  Representations (including metadata) contain enough information to be modified or deleted•  Provided that the client has permission to do soConfidential Information | December 18, 2012 5
  7. 7. Self-descriptive Messages < HTTP/1.1 200 OK! < Server: ConfD! < Cache-control: private, no-cache, must-revalidate, proxy-revalidate ! < Date: Tue, 18 Dec 2012 15:53:12 GMT! < Content-Type: application/vnd.yang.data+xml! < Transfer-Encoding: chunked!•  Each message includes enough information to describe how to process the message•  Foundation for stateless processing•  Standard methods and media types are used to indicate semantics and exchange informationConfidential Information | December 18, 2012 6
  8. 8. Hypermedia as the Engines of Application State <running y:self="/api/running"/>! ! <interface y:self="/api/running/interfaces/interface/eth0">! ! <lock y:self="/api/running/_lock">! A REST API must not define fixed ! resource names or hierarchies - (angry) Fielding on his blog•  Most profound (and abused) criteria•  Clients deliver state via contents, query-string parameters, request headers and the URI•  Servers deliver state to clients via content, response codes, and response headers•  ...just like the web worksConfidential Information | December 18, 2012 7
  9. 9. REST vs Other Protocols REST SNMP NETCONF SOAP Data models SNMP MIBs YANG Models Data SMI YANG WSDL Modeling Language Management HTTP Verbs SNMP NETCONF N/A Operations Operations Operations RPC Protocol HTTP/XML/ BER XML XML Encoding JSON Transport SSL/HTTP/ UDP SSH/TCP SSL/HTTP/ Stack TCP TCPConfidential Information | December 18, 2012 8
  10. 10. REST in a Network Management Context•  We will focus on using REST to read and write data to network elements•  Most applications we’ve come across expect to use RESTful HTTP to extract data using simple scripts –  curl(1), wget(1)•  As mentioned, we manipulate resources, one at a time•  But we know people will try and use it to peek and pokeRecommended reading: RFC 3535 Overview of the 2002 IAB NetworkManagement WorkshopConfidential Information | December 18, 2012 9
  11. 11. Information Models and Data Models•  Information Models are conceptual, implementation independent•  Data Models are detailed, intended for implementations Information Examples: UML, Entity Model Relations (ER) Examples: SMI, WSDL, Data Model Data Model Data Model YANGRecommended reading: RFC 3444 On the difference between InformationModels and Data ModelsConfidential Information | December 18, 2012 10
  12. 12. Data Models in Network Management•  So, what is the data model of a router or a switch? –  For OpenFlow people, it’s the switch pipeline –  For I2RS people, it’s the FIB and RIB –  For most implementations in the field, it’s what’s in the CLI•  Well used CLIs exhibit the inherited characteristics of all use cases it’s been exposed to•  We’ll assume (and it’s relatively well founded) that REST APIs want to be on the same abstraction level as the CLI –  Also, reality (code base) prohibits much else –  REST on a network level is very interesting, but differentConfidential Information | December 18, 2012 11
  13. 13. The YANG Data Modeling Language•  IETF RFC 6020, Standards Track•  A Language designed to write data models for the NETCONF protocol. It provides features including: –  Human readable –  Hierarchical –  Reusable types and groupings –  Extensibility –  Formal constraints for validation•  Proven to be useful for other applications (CLI, Web UI, etc) 12
  14. 14. Example Data Model in YANG interfaces •  We’ll be looking at –  ietf-interface.yang! interface –  ietf-ip.yang! key: name •  Developed in the IETF statistics NETMOD WG ipv4 •  More models in the address address making ipv6 address addressConfidential Information | December 18, 2012 13
  15. 15. Mapping YANG to REST Resources•  YANG data nodes are mapped to REST resources•  YANG rpc statements are mapped to HTTP POST operations•  HTTP Verbs: –  GET to fetch resources –  POST to create resources –  PUT to replace a resource –  PATCH to modify existing resources –  DELETE to remove resourcesConfidential Information | December 18, 2012 14
  16. 16. An Example Query (An Ethernet Interface) 1> GET /api/running/interfaces/interface/eth0 HTTP/1.1!> Authorization: Basic YWRtaW46YWRtaW4=!> User-Agent: curl/7.28.!> Host:!> Accept: */*!> !< HTTP/1.1 200 OK!< Server: ConfD!< Date: Mon, 17 Dec 2012 16:08:33 GMT! 2< Content-Type: application/vnd.yang.data+xml!< Transfer-Encoding: chunked!< !!<interface y:self="/api/running/interfaces/interface/eth0”>! <name>eth0</name>! <type>ethernetCsmacd</type>! <location>0</location>! 3 <ipv4 xmlns="urn:ietf:params:xml:ns:yang:ietf-ip">! <address y:self="/api/running/interfaces/interface/eth0/ip:ipv4/address/">! <ip></ip>! </address>! </ipv4>! <ethernet xmlns="http://example.com/ethernet">! </ethernet>!</interface>!!Confidential Information | December 18, 2012 15
  17. 17. Introducing ConfD and its REST Interface REST NETCONF NETCONF SNMP Web UI ConfD Core Engine •  Transactions •  AAA/User Sessions •  Logs and audit trails YANG Module CDB Managed Objects API Managed Managed Object Object Managed Managed Object ObjectConfidential Information | December 18, 2012 16
  18. 18. How Does REST Work in a ConfD Context•  Just another northbound interface, shared everything•  RESTful API over HTTP –  for accessing data defined in YANG, stored in CDB –  using the datastores as defined in NETCONF•  Configuration data and state data are exposed to GET•  Configuration data also accept DELETE PATCH POST and PUTConfidential Information | December 18, 2012 17
  19. 19. REST Resources (Top Level)•  Top level resource application/vnd.yang.api –  Well known /api location –  version string –  running - the running datastore –  operational - the representation of all operational dataConfidential Information | December 18, 2012 18
  20. 20. REST Resources (Datastores)•  Datastores application/vnd.yang.datastore –  running - The running configuration of the device –  startup - The startup configuration of the deviceConfidential Information | December 18, 2012 19
  21. 21. Rest Resources (Model Resources)•  Model Resources application/vnd.yang.data –  All resources has y:path and y:self in representation –  All subresources has y:self referenceConfidential Information | December 18, 2012 20
  22. 22. (Finally) Time for Demo•  Queries –  Top-level –  Datastores –  Operations•  Interface configuration –  Look at interfaces –  Change IP addressConfidential Information | December 18, 2012 21
  23. 23. Conclusions and Things to Ponder•  REST allows for easy scripting with existing tools –  Many command line tools available and default on Linux and Mac –  Many, many language bindings•  REST does not provide sessions: –  Impact on error management –  How about transactions•  Rest allows for changing a single resource at a time: –  How does this scale in multi-parameter, complex environmentConfidential Information | December 18, 2012 22
  24. 24. Wrap up and Questions•  Suggested reading list: –  Fielding Dissertation –  RFC 3535 –  RFC 3444 –  YANG-API Protocol Draft (draft-bierman-netconf-yang-api-01)•  Discuss! –  @cmoberg –  calle@tail-f.comConfidential Information | December 18, 2012 23