Fraunhofer FKIE

Fraunhofer Strasse 20 Wachtberg 53343 DE henning.rogge@fkie.fraunhofer.de

Routing Manet DLEP PHY TLV This document defines an extension to the Dynamic Link Exchange Protocol (DLEP) to provide the quality of incoming radio signals.

Introduction The dynamic Link Exchange Protocol (DLEP) is defined in . It provides the exchange of link-related control information between DLEP peers. DLEP peers are comprised of a modem and a router. DLEP defines a base set of mechanisms as well as support for possible extensions. This document defines one such extension.

Requirements Language In many IETF documents, several words, when they are in all capitals as shown below, are used to signify the requirements in the specification. These capitalized words can bring significant clarity and consistency to documents because their meanings are well defined. This document defines how those words are interpreted in IETF documents when the words are in all capitals.

• These words can be used as defined here, but using them is not required. Specifically, normative text does not require the use of these key words. They are used for clarity and consistency when that is what's wanted, but a lot of normative text does not use them and is still normative.
• The words have the meanings specified herein only when they are in all capitals.
• When these words are not capitalized, they have their normal English meanings and are not affected by this document.

Authors who follow these guidelines should incorporate this phrase near the beginning of their document:

• The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Extension Usage and Identification The use of the Radio Quality Extension SHOULD be configurable. To indicate that the Radio Quality Extension is to be used, an implementation MUST include the Radio Quality Extension Type Value in the Extensions Supported Data Item. The Extensions Supported Data Item is sent and processed according to . The Radio Quality Extension Type Value is TBD; see .

Radio Quality Data Items This section describes the quality related Data Items of this extension. All Data Items available in this extension provide access to the radios physical layer measurements related to signal quality. Because of different designs of Radio PHY layers, this quality can be expressed in different ways, by referring to signal-to-noise ratio or by measuring the biterror rate (e.g. by using a forward error correction). Both of these possible informations are very valuable for calculating MANET metrics for radio networks with moving nodes and low datarates, e.g. VHF radio networks. Estimating channel quality based on packet loss can be impractical, because the estimated value changes too fast (because of movement) compared to the number of received frames. Biterror rate (and Signal Strength) can provice the additional information necessary to build a reasonable stable and agile metric. Biterror rate (before error correction) is a more generic way to represent this value, because it is a radio independent measurement. The Biterror Rate data item is mandatory when using the Radio Quality extension. All other TLVs presented in this document are optional.

Radio Biterror Rate Data Item Radio Biterror Rate Data Item is a mandatory TLV that contains information about the radio receivers estimate how often a transmitted bit will be received wrong. This value can often be either directly measured by the radio by comparing the result of a forward-error-correction to the original received data or calculated from the received signal-to-noise ratio and knowledge about the current modulation coding scheme. This Data Item can be both interface and neighbor specific. The format of the Radio Biterror Rate Data Item is:

Data Item Type:

TBD

Length:

1

Biterror:

Biterror rate measured as a negative exponent multiplied by 10 (to base 10), e.g. "40" for an error rate of 1 to 10^-4. An error rate of 0 is encoded with a 255.

Radio SNR Data Item Radio SNR Data Item contains information which signal to noise ratio the radio measured. This Data Item can be both interface and neighbor specific. The format of the Radio SNR Data Item is:

Data Item Type:

TBD

Length:

3

SNR:

SNR measured in dB multiplied by 10 as a signed integer.

Flags:

Flags field as defined below.

The Flags field is defined as:

I:

Interference Flag, indicating the the data includes interference into the noise value (SINR).

Reserved:

MUST be written as zero. Ignored on receipt and left for future assignment.

Radio Signal Strength Data Item (also called RSSI) Radio Signal Strength Data Item contains information which absolute signal strength the radio measured. This Data Item can be both interface and neighbor specific. This Data Item could also be used together with the Request Link Characteristics message to reconfigure the outgoing signal strength, either to reduce the size of the collision domain or to increase the range of the radio. The format of the Radio Signal Strength Data Item is:

Data Item Type:

TBD

Length:

2

Signal:

Signal Strength measured in dBm multiplied by 10 as a signed integer.

Radio Noise Data Item Radio Noise Data Item contains information which absolute noise value the radio measured. This Data Item SHOULD be interface specific. The format of the Radio Noise Data Item is:

Data Item Type:

TBD

Length:

2

Noise:

Noise measured in dBm multiplied by 10 as a signed integer.

Security Considerations The extension introduces a new Data Item for DLEP. The extension does not inherently introduce any additional vulnerabilities above those documented in . The approach taken to security in that document applies equally when running the extension defined in this document.

IANA Considerations As described below, IANA has assigned two values per this document. Both assignments are to registries defined by .

Extension Type Value IANA has assigned the following value in the "Extension Type Values" registry within the "Dynamic Link Exchange Protocol (DLEP) Parameters" registry. The new value is in the range with the "Specification Required" policy: New Extension Type Value

Code	Description	Reference
TBD	Radio Quality	This document

Data Item Value IANA has assigned the following value in the "Data Item Type Values" registry within the "Dynamic Link Exchange Protocol (DLEP) Parameters" registry. The new value is in the range with the "Specification Required" policy: New Data Item Value

Type Code	Description	Reference
TBD	Radio Biterror Rate	This document
TBD	Radio SNR	This document
TBD	Radio Signal	This document
TBD	Radio Noise	This document

Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. When routing devices rely on modems to effect communications over wireless links, they need timely and accurate knowledge of the characteristics of the link (speed, state, etc.) in order to make routing decisions. In mobile or other environments where these characteristics change frequently, manual configurations or the inference of state through routing or transport protocols does not allow the router to make the best decisions. This document introduces a new protocol called the Dynamic Link Exchange Protocol (DLEP), which provides a bidirectional, event-driven communication channel between the router and the modem to facilitate communication of changing link characteristics. Informative References Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226.