DLEP Radio Channel Utilization Extension

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. Radio channel utilization provides a packet/frame independent measurement how a radio channel is used and how much resources are still available. While incoming and outgoing traffic can be easily measured on the router, the amount of airtime used by management traffic of the radio is invisible to the router, as is unicast traffic between two adjacent radios (unless the radio supports promiscous mode). This could present the a fully utilized radio channel to the router as totally empty. Getting a direct radio level information how much time on the radio channel has been used up by incoming or outgoing data or control frames allows a router to calculate a better routing metric or allows management agents to detect a channel being unusable for communication because of external jamming.

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 Channel Utilization Extension SHOULD be configurable. To indicate that the Channel Utilization Extension is to be used, an implementation MUST include the Radio Channel Utilization Extension ID in the Extensions Supported Data Item. The Extensions Supported Data Item is sent and processed according to . The Channel Utilization TLVs can be used by the router to improve the tracking of channel usage by different radios and give a more exact estimate how much free capacity the channel has currently. This information can be used for adjusting timing intervals between automatically generated data, e.g. HELLO messages of the local routing protocol. All four Data Items are 64 bit unsigned integers time measurements in nanoseconds since an arbitrary starting point, e.g. the radio bootup. Each value monotonically increases for the entire duration of the DLEP session; they are never reset. Each of the four data items tracks the time the radio is in a certain type of operation. Channel utilization data types

Type	Description
Active	Time the radio has been operational and able to interact with the channel
Busy	Time the radio channel was blocked for an arbitrary reason
RX	Time the radio was receiving data
TX	Time the radio was transmitting data

A radio that doesn't track the time for receiving (RX) and transmitting (TX) data explicitly MUST add all time intervals the radio channel is not free into the Radio Channel Busy Data Item. The time the radio channel has been free can be calculated by substracting the values of Busy, Rx and Tx from the value provided by the Radio Active Channel Data Item. By tracking these values over time the router can calculate the channel usage statistics for routing metrics or report the received value to a management layer. A radio that is using independent channel resources for each neighbor (e.g. by beam forming) can also track and report channel usage time for each DLEP neighbor.

Data Items All four Data Items of this extension can be used both as Session specific and Destination specific metrics. If the radio is only tracking channel usage on the interface level, the Data Items are used in SessionInitResponse and SessionUpdate messages. If the radio also is tracking channel usage for each Destination, they are also used in DestinationUp, DestinationUpdate and DestinationAnnounceResponse messages. All four Data Items contain a single 64 bit unsigned integer time interval measured in nanoseconds as the TLV value.

Radio Channel Active Data Item Radio Channel Active Item contains information about how long the radio channel has been active. This provides the router with a reference to interpret the values provided by the other three Data Items. Because of this the value in this item must be larger than the values in the other three Data Items this extensions defines together. This Data Item is mandatory for SessionInitResponse messages. The format of the Radio Channel Active Data Item is:

Data Item Type:: TBD1
Length:: 8
Active Time:: Time in nanoseconds since the channel has been in use.

Radio Channel Busy Data Item Radio Channel Busy Item contains information how about much time the radio channel has been busy, not including the time provided in the Channel Rx and Chanel Tx Data Item. The format of the Radio Channel Busy Data Item is:

Data Item Type:: TBD2
Length:: 8
Busy Time:: Time in nanoseconds the channel was busy during its active time.

Radio Channel Rx Data Item Radio Channel Rx Item contains information about how much time the local radio has been receiving data from other radios. The format of the Radio Channel Rx Data Item is:

Data Item Type:: TBD3
Length:: 8
Rx Time:: Time in nanoseconds the local radio has received data from other radios during its active time.

Radio Channel Tx Data Item Radio Channel Tx Item contains information about how much time the local radio has been transmitting data to other radios. The format of the Radio Channel Tx Data Item is:

Data Item Type:: TBD4
Length:: 8
Tx Time:: Time in nanoseconds the local radio has transmitted data to other radios during its active time.

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. All 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 Channel Active
TBD2	Radio Channel Busy
TBD3	Radio Channel Rx
TBD4	Radio Channel Tx

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 Channel Utilization