RAW F. Theoleyre
Internet-Draft CNRS
Intended status: Standards Track G. Papadopoulos
Expires: January 6, 2020 IMT Atlantique
July 5, 2019

Operations, Administration and Maintenance (OAM) features for RAW


The wireless medium presents significant specific challenges to achieve properties similar to those of wired deterministic networks. At the same time, a number of use cases cannot be solved with wires and justify the extra effort of going wireless. This document presents some of these use-cases.

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Table of Contents

1. Introduction

RAW (Reliable and Available Wireless) is an effort to provide deterministic behavior over a network that includes a wireless physical layer. Enabling the wireless communication reliable and available is even more challenging than it is with wires, due to the numerous causes of loss in transmission that add up to the congestion losses and the delays caused by overbooked shared resources. To provide quality of service along a multihop path that is composed of wired and wireless hops, additional methods needs to be considered to leverage the potential lossy wireless communication.

Traceability belongs to Operations, Administration, and Maintenance (OAM) which is the toolset for fault detection and isolation, and for performance measurement. More can be found on OAM Tools in .

The main purpose of this document is to details the requirements of the OAM features recommended to construct a predictable communication infrastructure on top of a collection of wireless networks. In particular, we expect to provide packet loss evaluation, self-testing and automated adaptation to enable trade-offs between resilience and energy consumption.

This document describes the benefits, problems, and trade-offs for using OAM in wireless networks to provide availability and predictability.

In this document, the term OAM will be used according to its definition specified in [RFC6291]. We expect to implement an OAM framework in RAW networks to maintain a real-time view of the network infrastructure, and its ability to respect the Service Level Agreements (delay, reliability) assigned to each data flow.

1.1. Terminology

2. OAM to provision appropriately the resources

RAW networks expect to make the communications predictable on top of a wireless network infrastructure. Most critical applications will define a Service Level Agreeemnt to respect for the data flows it generates. Thus, the wireless networks have to be dimensionned to respect these SLAs.

To respect strict guarantees, RAW relies on a PCE which has to schedule the transmissions in the different wireless networks. Thus, resources have to be provisionned to handle any defect. OAM represents the core of the overprovisonning process, and maintains the network operational by updating the schedule dynmically.

Fault-tolerance also assumes that multiple path have to be provisionned so that an end-to-end circuit keeps on existing whatever the conditions. OAM is in charge of controling the replication/ process

To be energy-efficient, reserving some dedicated out-of-band resources for OAM seems ireealistic, and only in-band solutions are considered here.

3. Operation

RAW expects to operate fault-tolerant networks. Thus, we need mechanisms able to detect faults, before they impact the network performance.

We make a distinction between the two following complementary mechanisms:

These two-steps identification is required since RAW expects to rely on wireless networks. Thus, we have to minimize the amount of statistics / measurements to exchange:

Thus, localized and centralized mechanisms have to be combined together, and additionnal control packets have to be triggered only after a fault detection.

4. Administration

To take proper decisions, the network has to expose a collection of metrics, including:

These metrics should be collected:

4.1. Worst-case constraint

RAW aims to enable real-time communications on top of an heterogeneous architecture. Since wireless networks are known to be lossy, RAW has to implement strategies to improve the reliability on top of unreliable links. Hybrid Automatic Repeat reQuest (ARQ) has typically to enable retransmissions based on the end-to-end reliability and latency requirements.

To take correct decisions, the controller needs to know the distribution of packet losses for each flow, and for each hop of the paths. In other words, average end-to-end statistics are not enough. They must allow the controller to predict the worst-case.

4.2. Energy efficiency constraint

RAW targets also low-power wireless networks, where energy represents a key constraint. Thus, we have to cake care of the energy and bandwidth consumption. The following techniques aim to reduce the cost of such maintenance:

5. Maintenance

RAW needs to implement a self-healing and self-optimization approach. The network must continuously retrieve the state of the network, to judge about the relevance of a reconfiguration, quantifying:

Thus, reconfiguration may only be triggered if the gain is significant.

Since RAW expects to support real-time flows, we have to soft-reconfiguration, where the novel ressources are reserved before the ancient ones are released. Some mechanisms have to be proposed so that packets are forwarded through the novel track only when the resources are ready to be used, while maintaining the global state consistent (no packet re-ordering, duplication, etc.)

In particular, RAW has to support the following modifications:

6. Informative References

[ipath] Gao, Y., Dong, W., Chen, C., Bu, J., Wu, W. and X. Liu, "iPath: path inference in wireless sensor networks.", 2016.
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, D. and S. Mansfield, "Guidelines for the Use of the "OAM" Acronym in the IETF", BCP 161, RFC 6291, DOI 10.17487/RFC6291, June 2011.

Authors' Addresses

Fabrice Theoleyre CNRS Building B 300 boulevard Sebastien Brant - CS 10413 Illkirch - Strasbourg, 67400 FRANCE Phone: +33 368 85 45 33 EMail: theoleyre@unistra.fr URI: http://www.theoleyre.eu
Georgios Z. Papadopoulos IMT Atlantique Office B00 - 102A 2 Rue de la Châtaigneraie Cesson-Sévigné - Rennes, 35510 FRANCE Phone: +33 299 12 70 04 EMail: georgios.papadopoulos@imt-atlantique.fr