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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 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 .

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 formats 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 provide 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 might be directly measured by the radio or be calculated by a measured Signal-to-Noise radio and the known (to the vendor of the radio) E0/N-to-BER curve of each used modulation coding scheme. It was selected as the mandatory data item because it is easier to compare between different radios than two Signal-to-Noise ratios. 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 of 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. This Data Item MUST be used in the Session Initialization Response message and MAY be used in Session Update messages. If the radio supports destination specific quality information, this Data Item MUST be used in Destination Up messages and MAY be used in Destination Update and Destination Announce Response messages. The format of the Radio Biterror Rate Data Item is:

Data Item Type:

TBD1

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 about which signal to noise ratio the radio measured. This Data Item can be both interface and neighbor specific. If supported this Data Item MUST be used in the Session Initialization Response and MAY be used in Session Update messages. If the radio supports destination specific quality information, this Data Item MAY Item MAY be used in Destination Up, Destination Update and Destination Announce Response messages. The format of the Radio SNR Data Item is:

Data Item Type:

TBD2

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 about which absolute signal strength the radio measured. This Data Item can be both interface and neighbor specific. If supported this Data Item MUST be used in the Session Initialization Response and MAY be used in Session Update messages. If the radio supports destination specific quality information, this Data Item MAY Item MAY be used in Destination Up, Destination Update and Destination Announce Response messages. 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. In this case this Data Item MAY be used in Link Characteristics Request and Link Characteristics Response messages. The format of the Radio Signal Strength Data Item is:

Data Item Type:

TBD3

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 about which absolute noise value the radio measured. This Data Item SHOULD be interface specific. If supported this Data Item MUST be used in the Session Initialization Response and MAY be used in Session Update messages. The format of the Radio Noise Data Item is:

Data Item Type:

TBD4

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 five values per this document. Both assignments are to registries defined by .

Data Item Type Values IANA has assigned the following value in the "Data Item Type Values" registry defined by , chapter 15.4. The new values are in the range with the "Specification Required" policy: Data Item Type Values

Type Code	Description
TBD1	Radio Biterror Rate
TBD2	Radio SNR
TBD3	Radio Signal
TBD4	Radio Noise

Extension Type Values IANA has assigned the following value in the "Extension Type Values" registry defined by , chapter 15.6. The new value is in the range with the "Specification Required" policy: DLEP Extension Types

Code	Description
TBD5	Radio Quality

Normative References Informative References