Subject: [manet] comments on draft-ietf-manet-dlep-19

From: "MATTY, Steven" <[email-masked]>
Date: Fri, 4 Mar 2016 16:51:49 +0000

Hi Rick, Stan et al

Finally had a chance to go over DLEP 19 and only have minor observations...

3.1 Router-requested Destinations

A Destination Announce message MAY also be used by a router to

   request information concerning a destination that it has previously

   declined interest in, via the 'Not Interested' status code, see

   Table 3, or declared as down, via the Destination Down message.

Reading the draft in sequence, this already presume the reader is aware that a router

can decline interest in destinations - even though this has not been stated yet. Agree with Lou that

perhaps Section 3 belongs later in the document.

4. Metrics

Section 4, point 2 -

Suggest some consistency when using terms  "session-wide context" and "modem-wide context"

Section 4 : Link Characteristics  Request message.  I am pleased to see this message in DLEP

(was this added in Draft 18?)

5. DLEP Session Flow

Is there a better way of stating that the Peer Discovery state is optional for routers as it

almost contradicts the opening statement "All peers participating in a DLEP session

transition through five (5)distinct states during the lifetime of a DLEP session:" ?

Perhaps something along the lines of :

"The Peer Discovery state is OPTIONAL to implement for routers.  If it is not used, then a

preconfigured TCP address/port combination MUST be provided to the router, and the router will

immediately transition to the Session Initialization state."

5.1 Peer Discovery State

"It is up to the router implementation if Peer Discovery signals continue to be sent after the

device has transitioned to the Session Initialization state."

Wouldn't we also want to specify that a Modem MUST silently ignore Peer Discovery signals from

routers with which it has already established a DLEP Session? If we don't then we can easily end up

with an infinite ridiculously large number of DLEP sessions between the same modem and router.

5.4 Session Termination State

Is the text "as the result of an invalid message or error" necessary in this para?

NIT: "then if is RECOMMENDED" typo: should read "then it is RECOMMENDED"

"Any messages received after either sending or receiving a Session Termination message MUST be silently ignored."

Presumably "Any messages" means  'Any messages other than Session Termination Response message' ?

6. Transaction Model

Might suggest for clarity that one request per destination is in terms of the DLEP session. The Session Initialization transaction

description seems a little out of place here, and also clarify that receiving multiple Session Initialization requests from different

peers IS permissable

9.1 DLEP Signal Header

NIT: "Signal/Message Type" should read "Signal Type"

10. I'm tempted to suggest splitting the table into two - "DLEP Signals" and "DLEP Messages" since DLEP signal types must not appear in DLEP messagea

and vice versa?

QUESTION :

Destination Announce messages. If a router issues a Destination Announce message for a given MAC, is it free to then further issue a Destination Announce (not interested)

if for some reason it has changed its mind? Or is it restricted to issuing the "not interested" after receiving a Destination Up message for that MAC?

11.1 Status

NIT: Suggest reword "Acknowledgement messages" to "Response messages"

NIT: In the case of a "Not Interested" status, is this strictly an indication of success (or failure)? If not, then it contradicts the text in para 2

11.19: RLQR

NIT: Clarify "A non-dimensional 8-bit integer, 0-100, representing relative link quality" by adding "of the receive link" (or similar)

11.20 RLQT:

NIT: As above but for transmit

QUESTION : RESR and REST are explicitly declared as percentages. RLQR/RLQT are explicitly declared as "non-dimensional". Is this deliberate? Both accept 0-100 and to my tired brain both

would appear to indicate a percentage. If not, then why not open RLQR/RLQT to the full 0-255 range?

Regards

Steve

This email (including any attachments) may contain confidential and/or privileged information or information otherwise protected from disclosure. If you are not the intended recipient, please notify the sender immediately, do not copy this message or any attachments and do not use it for any purpose or disclose its content to any person, but delete this message and any attachments from your system. Airbus Defence and Space Limited disclaims any and all liability if this email transmission was virus corrupted, altered or falsified.
-o-
Emails to Airbus Defence and Space Limited may be processed, recorded and monitored outside the UK.
-o-
Airbus Defence and Space Limited, Registered in England and Wales No. 2449259
Registered Office: Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2AS, England