Network Working Group J. Schoenwaelder
Internet-Draft V. Bajpai
Intended status: Standards Track Jacobs University Bremen
Expires: January 4, 2016 July 3, 2015
Using RESTCONF with LMAP Measurement Agents
draft-ietf-lmap-restconf-00.txt
Abstract
This document describes how RESTCONF can be used with a YANG data
model for Large-Scale Measurement Platforms (LMAP).
Status of This Memo
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This Internet-Draft will expire on January 4, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Overview of RESTCONF . . . . . . . . . . . . . . . . . . . . 2
3. RESTCONF as LMAP Control Protocol . . . . . . . . . . . . . . 3
4. RESTCONF as LMAP Report Protocol . . . . . . . . . . . . . . 3
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. Informative References . . . . . . . . . . . . . . . . . . . 4
Appendix A. Response to Protocol Comparison Criteria . . . . . . 5
Appendix B. Example RESTCONF Control Protocol Exchange . . . . . 7
Appendix C. Example RESTCONF Report Protocol Exchange . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document discusses how a controller can use the RESTCONF
protocol [I-D.ietf-netconf-restconf] to configure Large-Scale
Measurement of Broadband Performance (LMAP) measurement agents (MAs)
[I-D.ietf-lmap-framework]. It also discusses how RESTCONF can be
used to report measurement results to a collector.
MAs may be deployed as separate hardware devices or as functions
embedded in consumer electronic devices and home routers or as pure
software solutions that can be installed on off-the-shelf computing
equipment. Measurement agents receive instructions from a controller
about when and how to conduct what measurements (the measurement
schedule) and how and when to report measurement results to a data
collector (the report schedule). Further information about the
interaction between MAs and controllers and collectors can be found
in [I-D.ietf-lmap-framework].
The LMAP information model [I-D.ietf-lmap-information-model] defines
the information exchanged between a controller and an MA and the
information exchanged between an MA and a collector. An information
model is conceptual and protocol-independent. A concrete YANG
[RFC6020] data model derived from the conceptual information model is
defined in [I-D.ietf-lmap-yang].
2. Overview of RESTCONF
The RESTCONF protocol [I-D.ietf-netconf-restconf] provides a REST-
like interface to access and manipulate a so-called unified YANG
datastore [RFC6020]. The basic idea behind RESTCONF is expose a YANG
datastores as a collection of Web resources that can be manipulated
using standard HTTP [RFC7230] DELETE, PATCH, POST, and PUT methods.
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The resource hierarchy is derived from the nesting structure of the
YANG schema tree, leading to a so called data model driven REST API.
RESTCONF is essentially a convention how to use HTTP over TLS to
access a datastore that has a structure defined by a YANG data model.
The data is exchanged in XML encoding or JSON encoding.
The normal mode of operation is that the RESTCONF client initiates a
secure transport to the RESTCONF server. For devices located behind
a NAT, a so called 'call-home' mechanism has been defined
[I-D.ietf-netconf-call-home] that enables the RESTCONF server to
establish a secure transport to a RESTCONF client. Note that call
home only changes the TCP connection establishment, the TLS and HTTP
client/server roles do not change. The policy used to call home can
be configured through a configuration data model
[I-D.ietf-netconf-server-model]. This model provides mechanism to
configure a list of redundant endpoints and it provides control over
call-home policies (e.g, call-home frequency, idle-timers, keep-alive
timers).
3. RESTCONF as LMAP Control Protocol
It is straight-forward to user RESTCONF as a control protocol. The
YANG data model [I-D.ietf-lmap-yang] derived from the underlying
information model [I-D.ietf-lmap-information-model] translates into a
collection of RESTCONF resources that can be manipulated at various
levels of granularity using DELETE, PATCH, POST, and PUT methods.
An example exchange showing a REST call to create a schedule object
is shown in Appendix B.
4. RESTCONF as LMAP Report Protocol
One way of mapping the information model parts relevant for reports
into a YANG data model is the usage of YANG notifications. This is
the approach currently used in [I-D.ietf-lmap-yang]. This mapping
leads to report notifications that push measurement results from the
MA to a collector. The RESTCONF protocol uses Server Sent Events as
the underlying mechanism to stream notifications.
A direct mapping of the information model leads to relatively verbose
exchanges and it is possible to define more space efficient
notifications that suppress information that is only changing rarely.
An example exchange of a result notification is shown in Appendix C.
Note that alternative designs are possible. One option is to make
the collector a RESTCONF server and to have the MA push results to
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the collector by posting to resources on the controller. Another
option is to have the results reside on the MA and to export the
results as part of the operational state of the MA. The collector(s)
will then use GET requests to fetch the result resources from the MA.
Note that all three approaches can be implemented using RESTCONF and
YANG.
5. Conclusion
This document discusses how RESTCONF can be used as a control
protocol and a report protocol for Large-Scale Measurement Platforms
(LMAP). The benefit of using RESTCONF is that no new protocol work
needs to be done. Additional benefits derive from using YANG and a
data model driven approach. Despite the reuse of existing tools,
using a data model driven approach allows to easily reuse other data
models (e.g., network interfaces [RFC7223], [RFC7277] or general
system services [RFC7317]) in order to export additional status
information about an MA to a controller.
6. IANA Considerations
This document has no requests for IANA.
7. Acknowledgements
Juergen Schoenwaelder and Vaibhav Bajpai work in part on the Leone
research project, which receives funding from the European Union
Seventh Framework Programme [FP7/2007-2013] under grant agreement
number 317647.
8. Informative References
[I-D.ietf-lmap-framework]
Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
Aitken, P., and A. Akhter, "A framework for Large-Scale
Measurement of Broadband Performance (LMAP)", draft-ietf-
lmap-framework-12 (work in progress), March 2015.
[I-D.ietf-lmap-information-model]
Burbridge, T., Eardley, P., Bagnulo, M., and J.
Schoenwaelder, "Information Model for Large-Scale
Measurement Platforms (LMAP)", draft-ietf-lmap-
information-model-06 (work in progress), July 2015.
[I-D.ietf-lmap-yang]
Schoenwaelder, J. and V. Bajpai, "A YANG Data Model for
LMAP Measurement Agents", draft-ietf-lmap-yang-01 (work in
progress), July 2015.
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[I-D.ietf-netconf-call-home]
Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
draft-ietf-netconf-call-home-08 (work in progress), June
2015.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-06 (work in
progress), June 2015.
[I-D.ietf-netconf-server-model]
Watsen, K. and J. Schoenwaelder, "NETCONF Server and
RESTCONF Server Configuration Models", draft-ietf-netconf-
server-model-06 (work in progress), February 2015.
[I-D.starkcarey-lmap-protocol-criteria]
Stark, B. and T. Carey, "LMAP Protocol Selection
Criteria", draft-starkcarey-lmap-protocol-criteria-01
(work in progress), March 2015.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, May 2014.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
2014.
[RFC7277] Bjorklund, M., "A YANG Data Model for IP Management", RFC
7277, June 2014.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, August 2014.
Appendix A. Response to Protocol Comparison Criteria
A set of control and report protocol comparison criteria has been
defined in [I-D.starkcarey-lmap-protocol-criteria]. This section
compares the usage of RESTCONF against the criteria.
CP-MUST-1 yes (RFC6241 RFC6242, RFC5539),
[I-D.ietf-netconf-restconf]
CP-MUST-2 yes [I-D.ietf-netconf-call-home]
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CP-MUST-3 yes SSH / TLS (NETCONF), TLS (RESTCONF)
CP-MUST-4 yes YANG data models [RFC6020] have a well defined
versioning and extension model
CP-DIFF-1 1
CP-DIFF-2 1
CP-DIFF-3 yes
CP-DIFF-4 yes (NETCONF|RESTCONF) call home
CP-DIFF-5 (underspecified - it is JSON or XML over HTTP/TLS)
CP-DIFF-6 (underspecified - it is JSON or XML over HTTP/TLS)
CP-DIFF-7 HTTP and JSON/XML are pretty much everywhere
CP-DIFF-8 YANG tools are out there and the rest will develop, HTTP
and TLS are pretty well understood
CP-DIFF-9 yes
CP-DIFF-10 many tools out there to create REST code, YANG tools
available
CP-DIFF-11 yes, YANG RFC 6020 data models have a version model
CP-DIFF-12 additional YANG modules can augment the standard data
model
CP-DIFF-13 JSON and XML, CBOR in the making
RP-MUST-1 yes [I-D.ietf-netconf-call-home]
RP-MUST-2 SSH / TLS (NETCONF), TLS (RESTCONF)
RP-MUST-3 YANG RFC 6020 data models have a version model
RP-DIFF-1 TCP
RP-DIFF-2 yes
RP-DIFF-3 (underspecified - it is HTTP over TLS)
RP-DIFF-4 yes
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RP-DIFF-5 yes
RP-DIFF-6 yes (as part of HTTP encoding negotiations)
RP-DIFF-7 (underspecified - it is JSON or XML over HTTP/TLS)
RP-DIFF-8 HTTP and JSON/XML are pretty much everywhere
RP-DIFF-9 many tools out there to create REST code, YANG tools
available
RP-DIFF-10 yes
RP-DIFF-11 many tools out there to create REST code, YANG tools
available
RP-DIFF-12 JSON and XML, CBOR in the making
Appendix B. Example RESTCONF Control Protocol Exchange
Below is a YANG tree diagram of a part of the data model covering
schedules. This is taken from [I-D.ietf-lmap-yang].
module: ietf-lmap
+--rw lmap
+--rw schedules
+--rw schedule* [name]
+--rw name string
+--rw event leafref
+--rw action* [name]
| +--rw name string
| +--rw task leafref
| +--rw option* [name]
| | +--rw name string
| | +--rw value? string
| +--rw destination* leafref
+--rw execution-mode enumeration
Below is an XML representation of instance data conforming to the
YANG data model is shown below. Note that some of the strings are
references to other portions of the instance data not show here.
This is again taken from [I-D.ietf-lmap-yang].
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hourly-schedule
hourly
icmp-latency-hourly
icmp-latency-measurement
daily
sequential
Below is an example showing how RESTCONF can be used to create the
above schedule. The prefix C: indicates the controller, the prefix
M: indicates the measurement agent. This example uses a JSON
encoding (and note that much of the white-space can be removed, this
is only there to help with readability).
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C: POST /restconf/data/ietf-lmap:lmap/schedules HTTP/1.1
C: Host: example.com
C: Content-Type: application/yang.data+json
C:
C: {
C: "ietf-lmap:schedule": {
C: "name": "hourly-schedule",
C: "event": "hourly",
C: "action": [
C: {
C: "name": "icmp-latency-hourly",
C: "task": "icmp-latency-measurement",
C: "destination": "daily",
C: }
C: ],
C: "execution-mode": "sequential"
C: }
C: }
M: HTTP/1.1 201 Created
M: Date: Mon, 26 Mar 2015 17:01:00 GMT
M: Server: example-server
M: Location: https://example.com/restconf/data
M: /ietf-lmap:lmap/schedules/schedule=hourly-schedule
M: Last-Modified: Mon, 26 Mar 2015 17:01:00 GMT
M: ETag: b3a3e673be2
Appendix C. Example RESTCONF Report Protocol Exchange
The first step taken by the collector is to lookup the event stream
resource.
C: GET /restconf/data/ietf-restconf-monitoring:restconf-state/
C: /streams/stream=NETCONF/encoding=json/events HTTP/1.1
C: Host: example.com
C: Accept: application/yang.data+xml
M: HTTP/1.1 200 OK
M: Content-Type: application/yang.api+xml
M:
M:
M: https://example.com/streams/NETCONF-json
M:
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Once the event stream resource is known (information might be
cached), the collector subscribes to the event stream resource.
C: GET /streams/NETCONF-json HTTP/1.1
C: Host: example.com
C: Accept: text/event-stream
C: Cache-Control: no-cache
C: Connection: keep-alive
M: data: {
M: data: "ietf-restconf:notification": {
M: data: "event-time": "2015-03-25T00:01:00+00:00",
M: data: "ietf-lmap:report": {
M: data: "date": "2015-03-25T00:01:00+00:00",
M: data: "agent-id": "xxx",
M: data: "header": {
M: data: "column": "target",
M: data: "column": "rtt"
M: data: }
M: data: "row": {
M: data: "start": "2015-03-25T00:00:55+00:00",
M: data: "value": "192.0.2.1",
M: data: "value": 42
M: data: }
M: data: "row": {
M: data: "start": "2015-03-25T00:00:56+00:00",
M: data: "value": "192.0.2.2",
M: data: "value": 24
M: data: }
M: data: }
M: data: }
M: data: }
Authors' Addresses
Juergen Schoenwaelder
Jacobs University Bremen
Email: j.schoenwaelder@jacobs-university.de
Vaibhav Bajpai
Jacobs University Bremen
Email: v.bajpai@jacobs-university.de
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