Re: [icnrg] [EXT] I-D Action: draft-irtf-icnrg-icnping-03.txt

[Spyridon Mastorakis <[e-mail]>]

Thanks for the comments, Junxiao. The drafts have been updated and your comments have been addressed.

Spyros

—

Spyridon (Spyros) Mastorakis, Ph.D.
Assistant Professor
Computer Science Department
University of Nebraska at Omaha
Peter Kiewit Institute Room 174E
Associate Editor, IEEE Internet of Things Journal
Director, Ph.D. Program in Information Technology
Website: https://sites.google.com/site/spyridonmastorakis

On Apr 5, 2022, at 6:39 AM, David R. Oran <[e-mail]<mailto:[e-mail]>> wrote:

Non-NU Email

Thanks!
We’ll get these fixed quickly.

On 4 Apr 2022, at 11:57, Junxiao Shi wrote:

Hi Spyros

I have inspected the diff between -03 and -4. Certain errors are not fully
fixed. See comments inline.

New problem: in references

[NDNTLV]   "NDN Packet Format Specification.", 2016,
<https://urldefense.com/v3/__http://named-data.net/doc/ndn-tlv/__;!!PvXuogZ4sRB2p-tU!Xz_WVwqvAcMkJkLusl_deBsZ2d92QSiVeCmfC6bOzFHRjdZdhj71JsWc0R-MLFGprkAL$ > .

The current spec link is:
https://urldefense.com/v3/__https://named-data.net/doc/NDN-packet-spec/current/__;!!PvXuogZ4sRB2p-tU!Xz_WVwqvAcMkJkLusl_deBsZ2d92QSiVeCmfC6bOzFHRjdZdhj71JsWc0R-MLKV7kvFM$  . It was last updated
in 2022.
You can also cite a specific version on
https://urldefense.com/v3/__https://github.com/named-data/NDN-packet-spec__;!!PvXuogZ4sRB2p-tU!Xz_WVwqvAcMkJkLusl_deBsZ2d92QSiVeCmfC6bOzFHRjdZdhj71JsWc0R-MLMaxcvab$  using a commit hash.

On Sun, Mar 6, 2022 at 6:52 PM Spyridon Mastorakis <[e-mail]<mailto:[e-mail]>>
wrote:

*External Email*
Dear Junxiao,

Thank you for your comments. We have addressed them in the updated
versions of our drafts that we just uploaded. Please see below for more
details:

On Dec 13, 2021, at 9:00 AM, Junxiao Shi <[e-mail]<mailto:[e-mail]>>
wrote:

Non-NU Email
------------------------------
Dear folks

I had a look at the NDN encoding for ICN Ping Protocol rev03.
It seems that the protocol partially assumes NDN packet format v0.2, and
is incompatible with the current NDN packet format.

As of 2019-May
<https://urldefense.com/v3/__https://redmine.named-data.net/issues/4853__;!!PvXuogZ4sRB2p-tU!R1XTGYwBlOXYUAzHhlV6sAyjq-Qz47wI4GLKSybSpxaQ2vKKrLONq9piKdxFWKR6IgjQ$> ,
the NDN packet encoding is written with IETF ABNF syntax.
However, ICN Ping still specifies its encoding with W3C EBNF syntax, which
could lead to confusion.


Fixed. We converted the packet encoding to the ETF ABNF syntax.


RFC5234 <https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/rfc5234__;!!PvXuogZ4sRB2p-tU!Xz_WVwqvAcMkJkLusl_deBsZ2d92QSiVeCmfC6bOzFHRjdZdhj71JsWc0R-MLHhiZDl2$ > defines the IETF
ABNF syntax. NDN packet encoding follows this specification.
In this syntax, a rule is defined by the following sequence:

name =  elements crlf

However, draft-irtf-icnrg-icnping-04 Section 5.2 is still defining a rule
with ::= operator.

The Parameters element is meant to contain PathSteering TLV.
As suggested below, it may make sense to move it to the NDNLPv2 header.

Section 5.2 defines Ping Echo Reply to be a Data packet with ContentType=0
and FreshnessPeriod=0.
Since ContentType defaults to 0 and FreshnessPeriod defaults to 0, neither
field is necessary.

Importantly, the NDN protocol specifies
<https://urldefense.com/v3/__https://named-data.net/doc/NDN-packet-spec/current/data.html*freshnessperiod__;Iw!!PvXuogZ4sRB2p-tU!R1XTGYwBlOXYUAzHhlV6sAyjq-Qz47wI4GLKSybSpxaQ2vKKrLONq9piKdxFWGIoTdsr$>
:

If the Data does not have a FreshnessPeriod or if it has a FreshnessPeriod
equal to zero, it MUST be immediately marked “non-fresh”.
If an Interest contains MustBeFresh element, a node MUST NOT return
“non-fresh” Data in response to this Interest.

This rule applies to not only the Content Store, but also the forwarding
pipelines.
Based on this rule, the Ping Echo Reply packet does not satisfy the Ping
Echo Request packet, making the ICN Ping incompatible with the current NDN
packet format.


We aim to avoid fetching cached responses from the network (unless a
request’s base name matches the name of a content object in the CS of a
forwarder and the client is ok with receiving a cached response). To do
that in the first place, the operation of a forwarder needs to be different
than how NFD works right now. So we do not think this is an issue with the
packet format per se, but rather the operation of the forwarder, which
needs to be extended/modified to handle ping and traceroute traffic.


draft-irtf-icnrg-icnping-04 Section 5.1 says:

Since the NDN packet format does not provide a mechanism to prevent the
network from caching specific data packets, we use the MustBeFresh element
for echo requests (in combination with a Freshness Period TLV of value 0
for echo replies) to avoid fetching cached echo replies with an expired
freshness period.


This still will not work, because an Interest with MustBeFresh cannot be
satisfied by a non-fresh Data.
This is enforced not only in NDN forwarders, but also in NDN libraries.

To minimize caching effect, you can either set FreshnessPeriod to 1 (not
0), or use a unique name each time (you are already doing this by adding a
random nonce component), or both.


Section 5.2 inserts a "PathSteering TLV" in the Data packet, which appears
before the Name element.
The TLV evolvability guidelines of the NDN protocol does not permit adding
new elements before the Name element.
New elements should be added later in the packet; to exclude an element
from the security envelope, it should appear after the SignatureValue
element.


Good point. We have moved the PathSteering TLV after the Signature TLV.

In the case of PathSteering TLV that "might be modified in a hop-by-hop
fashion", it does not belong in the network layer, but should be added as a
link layer header in NDNLPv2 or another link layer protocol.

The "PathSteering TLV" cites draft-oran-icnrg-pathsteering, but that
document only defines a "Path label TLV".
Its TLV-TYPE number assignment is 0x09, but that number is a "critical"
TLV-TYPE number that would cause a forwarder that does not understand this
feature to drop the packet; this choice needs justification.
Moreover, 0x09 is marked as reserved
<https://urldefense.com/v3/__https://named-data.net/doc/NDN-packet-spec/current/types.html__;!!PvXuogZ4sRB2p-tU!R1XTGYwBlOXYUAzHhlV6sAyjq-Qz47wI4GLKSybSpxaQ2vKKrLONq9piKdxFWM33PpJJ$> because
it conflicts with the former Selectors element in NDN packet format v0.2,
so that you may need to choose a different number.
You can then propose a change
<https://urldefense.com/v3/__https://gerrit.named-data.net/admin/repos/NDN-TLV__;!!PvXuogZ4sRB2p-tU!R1XTGYwBlOXYUAzHhlV6sAyjq-Qz47wI4GLKSybSpxaQ2vKKrLONq9piKdxFWA18J1X7$> to
reserve the number in NDN network layer protocol or edit this page
<https://urldefense.com/v3/__https://redmine.named-data.net/projects/nfd/wiki/NDNLPv2__;!!PvXuogZ4sRB2p-tU!R1XTGYwBlOXYUAzHhlV6sAyjq-Qz47wI4GLKSybSpxaQ2vKKrLONq9piKdxFWIEfRn16$> to
reserve the number in NDNLPv2.


To some extent, this sounds like an open question to us (i.e., whether
PathSteering TLV should be a part of the encoding of the base NDN protocol
or should be included in NDNLPv2). Nevertheless, we believe that since a
field like HopCount (whose value changes on a hop-by-hop basis) is in the
base NDN protocol rather than NDNLP, path steering should also be in the
base protocol, since it too is a hop-by-hop field independent of a
particular single hop.


The "PathSteering TLV" cites draft-oran-icnrg-pathsteering
<https://urldefense.com/v3/__https://www.ietf.org/archive/id/draft-oran-icnrg-pathsteering-05.html__;!!PvXuogZ4sRB2p-tU!Xz_WVwqvAcMkJkLusl_deBsZ2d92QSiVeCmfC6bOzFHRjdZdhj71JsWc0R-MLLgu6Y3D$ > ,
but that document only defines a "Path label TLV", and its encoding differs
from what's given in Figure 9.

Yours, Junxiao

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DaveO