lpwan Working Group A. Pelov
Internet-Draft Acklio
Intended status: Standards Track P. Thubert
Expires: July 23, 2021 Cisco Systems
A. Minaburo
Acklio
January 19, 2021
Static Context Header Compression (SCHC) Architecture
draft-pelov-lpwan-architecture-00
Abstract
This document defines the SCHC architecture.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Global architecture . . . . . . . . . . . . . . . . . . . . . 3
4. Data management . . . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The base operation and the definition of the SCHC compression &
Fragmentation are now described in several documents published by the
LPWAN working group.
Among them:
o The [rfc8724] defines the generic compression and fragmentation
mechanisms for SCHC and applies it to IPv6 and UDP.
o The [I-D.ietf-lpwan-coap-static-context-hc] extend the compression
to CoAP and OSCORE.
o The [I-D.ietf-lpwan-schc-yang-data-model] defines a rule
representation using the YANG formalism.
As [I-D.ietf-lpwan-coap-static-context-hc] states, the SCHC
compression and fragmentation mechanism can be implemented at
different levels and/or managed by different organizations. For
instance, as represented figure Figure 1, IP compression and
fragmentation may be managed by the network SCHC instance and end-to-
end compression between the device and the application. The former
can itself be split in two instances since encryption hides the field
structure.
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(device) (NGW) (App)
+--------+ +--------+
A S | CoAP | | CoAP |
p C | inner | | inner |
p H +--------+ +--------+
. V | SCHC | | SCHC |
| inner | cryptographical boundary | inner |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A S | CoAP | | CoAP |
p C | outer | | outer |
p H +--------+ +--------+
. C | SCHC | | SCHC |
| outer | functional boundary | outer |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
N . udp . . udp .
e .......... .................. ..........
t . ipv6 . . ipv6 . . ipv6 .
w C .......... .................. ..........
o S . schc . . schc . . . .
r H .......... .......... . . .
k C . lpwan . . lpwan . . . .
.......... .................. ..........
((((LPWAN)))) ------ Internet ------
Figure 3: OSCORE compression/decompression.
Figure 1: Different SCHC instances in a global system
This document defines a generic architecture for SCHC that can be
used at any of these levels. The goal of the architectural document
is to orchestrate the different protocols and data model defined by
the LPWAN woeking group to design an operational and interoperable
framework for allowing IP application over contrained networks.
2. Definitions
3. Global architecture
As described in [rfc8724] a SCHC service is composed of a Parser,
analyzing packets and creating a list of fields what will be used to
match against the compression rules. If a packet matches rules,
compression can be applied following rules instructions.
If SCHC compressed packet is too large to be send in a single L2
frame, fragmentation will apply. The process is similar, device
rules are checked to find the most appropriate fragmentation rule,
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regarding the SCHC packet size, the link error rate, the reliability
required by the application, ...
On the other direction, when a packet SCHC arrives, the ruleID is
used to find the rule. Its nature allows to select if it is a
compression or fragmentation rule.
The rule database contains a set of rules specific to a single
device. The [rfc8724] indicates that the SCHC instance reads the
rules to process C/D and F/R, rules are not modified during these
actions.
A SCHC instance, summarized in the Figure 2, implies C/D and F/R
present in both end. The device connected to a constrained network
is in one end and the other end is either located in the core network
or at the application.
In any cases, the rules must be the same in both ends to perform C/D
and F/R.
(device) (core|app)
(---) (---)
( r ) ( r )
(---) (---)
. read . read
. .
+-----+ +-----+
<===| R&D |<=..............................<=| C&F |<===
===>| C&F |=>..............................=>| R&D |===>
+-----+ +-----+
Figure 2: Summarized SCHC elements
To enable rule synchronization between both ends, a common rule
representation must be defined.
4. Data management
[I-D.ietf-lpwan-schc-yang-data-model] defines an YANG data model to
represent the rules. This enables the use of several protocols for
rule management, such as NETCONF, RESTCONF and CORECONF. NETCONF
uses SSH, RESTCONF uses HTTPS, and CORECONF uses CoAP(s) as their
respective transport layer protocols. The data is represented in XML
under NETCONF, in JSON under RESTCONF and in CBOR under CORECONF.
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create
(-------) read +=======+ *
( rules )<------->|Rule |<--|-------->
(-------) update |Manager| NETCONF, RESTCONF or CORECONF
. read delete +=======+ request
.
+-------+
<===| R & D |<===
===>| C & F |===>
+-------+
Figure 3: Summerized SCHC elements
Rule Manager (RM) is in charge of handling data derived from the YANG
Data Model and apply changes to the rules database Figure 3.
The RM is a application using the Internet to exchange information,
therefore:
o for the network-level SCHC, the communication does not require
routing. Each of the end-points having an RM and both RMs can be
viewed on the same link, therefore wellknown Link Local addresses
can be used to identify the device and the core RM. L2 security
MAY be deemed as sufficient, if it provides the necessary level of
protection.
o for application-level SCHC, routing is involved and global IP
addresses SHOULD be used. End-to-end encryption is recommended.
Management messages can also be carried in the negotiation protocol
as proposed in [I-D.thubert-lpwan-schc-over-ppp]
The RM traffic may be itself compressed by SCHC, especially if
CORECONF is used, [I-D.ietf-lpwan-coap-static-context-hc] can be
used.
5. Acknowledgements
The authors would like to thank (in alphabetic order):
6. Normative References
[I-D.ietf-lpwan-coap-static-context-hc]
Minaburo, A., Toutain, L., and R. Andreasen, "LPWAN Static
Context Header Compression (SCHC) for CoAP", draft-ietf-
lpwan-coap-static-context-hc-16 (work in progress),
October 2020.
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[I-D.ietf-lpwan-schc-yang-data-model]
Minaburo, A. and L. Toutain, "Data Model for Static
Context Header Compression (SCHC)", draft-ietf-lpwan-schc-
yang-data-model-03 (work in progress), July 2020.
[I-D.thubert-lpwan-schc-over-ppp]
Thubert, P., "SCHC over PPP", draft-thubert-lpwan-schc-
over-ppp-01 (work in progress), June 2020.
[rfc8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
Zuniga, "SCHC: Generic Framework for Static Context Header
Compression and Fragmentation", RFC 8724,
DOI 10.17487/RFC8724, April 2020,
<https://www.rfc-editor.org/info/rfc8724>.
Authors' Addresses
Alexander Pelov
Acklio
1137A avenue des Champs Blancs
35510 Cesson-Sevigne Cedex
France
Email: a@ackl.io
Pascal Thubert
Cisco Systems
45 Allee des Ormes - BP1200
06254 Mougins - Sophia Antipolis
France
Email: pthubert@cisco.com
Ana Minaburo
Acklio
1137A avenue des Champs Blancs
35510 Cesson-Sevigne Cedex
France
Email: ana@ackl.io
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