[DLK] FW: Honeywell comments on proposed VDL 2 T2 change

[Jose Godoy]

Dear Ladies and Gentlemen,

Tom McGuffin has provided the following comments on proposed changes to the VDLM2 T2 timer. Please review as it will be discussed during the September 22, 2016 AEEC DLK Systems Subcommittee web conference:

...Here are some additional comments on modifying T2 and other parameters

T1, T2, N1 , N2 can be modified in GSIF and other XIDs.

The values should be set in the XID RSP, as those set the parameters for the link

>From the VDL 2 Tech Manual,
The ground LME shall include in the XID_RSP_LE (F=1) any optional parameters for which it is not using the default values.

The ground LME shall include in the XID_RSP_HO (F=1) the optional parameters for which it is not using the default values.


T2 is connected to T1, because if T2 is longer, then sender's T1 has to be longer or sender will send more retransmissions. Increasing T1/T2 will have the effect of lengthening T1N2 scenarios.

Was this (T2 change impact on T1 values) considered and simulated properly by ELSA?

>From the Tech Manual,

5.3.4.2 Parameter T2 (delay before acknowledgement). Parameter T2 defines the maximum time allowed for the DLE to respond to any received frame (other than an XID) in order to ensure the response is received before the peer DLE's Timer T1 expires.
5.3.4.2.1 A station shall respond to any received frame (other than an XID) within parameter T2 time in order to ensure the response is received before the peer DLE's Timer T1 expires.
Note.- The period T2 should be a delay (shorter than the T1min value of the peer DLE) to permit the acknowledging DLE to schedule the response as an event in normal data processing and to allow sufficient time for an acknowledgement while maximizing the likelihood that an INFO frame will be transmitted and eliminate the need for an explicit acknowledgement...

Tom McGuffin
Honeywell Aerospace - Electronic COE
Datalink System Engineer
15001 N.E. 36th St    M/S  B13A
Redmond, WA 98052
Ph. (425) 885-8205

Best Regards,


José Godoy
Principal Engineer
AEEC AGCS, AOC, DLK Subcommittees Secretary
AEEC AeroMACS, Traffic and Surveillance (ADS-B), ARINC 429, and GNSS/GPS Working Groups Secretary

ARINC Industry Activities (IA)
An SAE-ITC Industry Program
16701 Melford Blvd., Suite 120
Bowie, MD 20715

desk  +1  240-334-2583
cell +1  443-534-8925
email: jose.godoy at sae-itc.org





Nothing in this message is intended to constitute an electronic signature unless a specific statement to the contrary is included in this message. Confidentiality Note: This message is intended only for the person or entity to which it is addressed. It may contain confidential and/or proprietary material. Any review, transmission, dissemination or other use, or taking of any action in reliance upon this message by persons or entities other than the intended recipient is prohibited. If you received this message in error, please contact the sender and delete it from your computer.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.sae-itc.org/pipermail/dlk/attachments/20160812/803596f8/attachment.html>