rfc9034v6.txt   rfc9034.txt 
Internet Engineering Task Force (IETF) L. Thomas Internet Engineering Task Force (IETF) L. Thomas
Request for Comments: 9034 C-DAC Request for Comments: 9034 C-DAC
Category: Standards Track S. Anamalamudi Category: Standards Track S. Anamalamudi
ISSN: 2070-1721 SRM University-AP ISSN: 2070-1721 SRM University-AP
S.V.R. Anand S.V.R. Anand
M. Hegde M. Hegde
Indian Institute of Science Indian Institute of Science
C. Perkins C. Perkins
Lupin Lodge Lupin Lodge
May 2021 June 2021
Packet Delivery Deadline Time in the Routing Header for IPv6 over Low- Packet Delivery Deadline Time in the Routing Header for IPv6 over Low-
Power Wireless Personal Area Networks (6LoWPANs) Power Wireless Personal Area Networks (6LoWPANs)
Abstract Abstract
This document specifies a new type for the 6LoWPAN routing header This document specifies a new type for the 6LoWPAN routing header
containing the deadline time for data packets, designed for use over containing the deadline time for data packets, designed for use over
constrained networks. The deadline time enables forwarding and constrained networks. The deadline time enables forwarding and
scheduling decisions for time-critical machine-to-machine (M2M) scheduling decisions for time-critical machine-to-machine (M2M)
skipping to change at line 443 skipping to change at line 443
Then, the Deadline-6LoRHE encoding with nonzero OTL is: Then, the Deadline-6LoRHE encoding with nonzero OTL is:
DTL = 3, OTL = 2, TU = 0b10, BinaryPt = 8, DT = 0xD4E4, DTL = 3, OTL = 2, TU = 0b10, BinaryPt = 8, DT = 0xD4E4,
OTD = 0x64 OTD = 0x64
6. Deadline-6LoRHE in Three Network Scenarios 6. Deadline-6LoRHE in Three Network Scenarios
In this section, the Deadline-6LoRHE operation is described for three In this section, the Deadline-6LoRHE operation is described for three
network scenarios. Figure 4 depicts a constrained time-synchronized network scenarios. Figure 4 depicts a constrained time-synchronized
LLN that has two subnets, N1 and N2, connected through 6LowPAN Border LLN that has two subnets, N1 and N2, connected through 6LoWPAN Border
Routers (6LBRs) [RFC8929] with different reference clock times, T1 Routers (6LBRs) [RFC8929] with different reference clock times, T1
and T2. and T2.
+-------------------+ +-------------------+
| Time-Synchronized | | Time-Synchronized |
| Network | | Network |
+---------+---------+ +---------+---------+
| |
| |
| |
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This document defines a new Elective 6LoWPAN Routing Header Type, and This document defines a new Elective 6LoWPAN Routing Header Type, and
IANA has assigned the value 7 from the 6LoWPAN Dispatch Page 1 number IANA has assigned the value 7 from the 6LoWPAN Dispatch Page 1 number
space for this purpose. space for this purpose.
+=======+=================+===========+ +=======+=================+===========+
| Value | Description | Reference | | Value | Description | Reference |
+=======+=================+===========+ +=======+=================+===========+
| 7 | Deadline-6LoRHE | RFC 9034 | | 7 | Deadline-6LoRHE | RFC 9034 |
+-------+-----------------+-----------+ +-------+-----------------+-----------+
Table 1: Entry in the Elective Table 1: Entry in the "Elective
6LoWPAN Routing Header Type 6LoWPAN Routing Header Type"
Registry Registry
8. Synchronization Aspects 8. Synchronization Aspects
The document supports time representation of the deadline and The document supports time representation of the deadline and
origination times carried in the packets traversing networks of origination times carried in the packets traversing networks of
different time zones having different time-synchronization different time zones having different time-synchronization
mechanisms. For instance, in a 6TiSCH network where the time is mechanisms. For instance, in a 6TiSCH network where the time is
maintained as ASN time slots, the time synchronization is achieved maintained as ASN time slots, the time synchronization is achieved
through beaconing among the nodes as described in [RFC7554]. There through beaconing among the nodes as described in [RFC7554]. There
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<https://ieeexplore.ieee.org/document/7460875>. <https://ieeexplore.ieee.org/document/7460875>.
[IEEE.802.1AS.2011] [IEEE.802.1AS.2011]
IEEE, "IEEE Standard for Local and Metropolitan Area IEEE, "IEEE Standard for Local and Metropolitan Area
Networks - Timing and Synchronization for Time-Sensitive Networks - Timing and Synchronization for Time-Sensitive
Applications in Bridged Local Area Networks", IEEE Std Applications in Bridged Local Area Networks", IEEE Std
802.1AS-2011, DOI 10.1109/IEEESTD.2011.5741898, March 802.1AS-2011, DOI 10.1109/IEEESTD.2011.5741898, March
2011, <https://doi.org/10.1109/IEEESTD.2011.5741898>. 2011, <https://doi.org/10.1109/IEEESTD.2011.5741898>.
[IOAM-DATA] [IOAM-DATA]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
for In-situ OAM", Work in Progress, Internet-Draft, draft- Ed., "Data Fields for In-situ OAM", Work in Progress,
ietf-ippm-ioam-data-12, 21 February 2021, Internet-Draft, draft-ietf-ippm-ioam-data-12, 21 February
<https://tools.ietf.org/html/draft-ietf-ippm-ioam-data- 2021, <https://tools.ietf.org/html/draft-ietf-ippm-ioam-
12>. data-12>.
[PHY-SPEC] Wi-SUN Alliance, "Wi-SUN PHY Specification V1.0", March [PHY-SPEC] Wi-SUN Alliance, "Wi-SUN PHY Specification V1.0", March
2016, <http://wi-sun.org>. 2016, <http://wi-sun.org>.
[RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases",
RFC 8578, DOI 10.17487/RFC8578, May 2019, RFC 8578, DOI 10.17487/RFC8578, May 2019,
<https://www.rfc-editor.org/info/rfc8578>. <https://www.rfc-editor.org/info/rfc8578>.
[RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli, [RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli,
"IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929, "IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929,
skipping to change at line 904 skipping to change at line 904
similarly for DT_abs - CT_abs. similarly for DT_abs - CT_abs.
As time proceeds, DT_abs - CT_abs gets smaller. When the deadline As time proceeds, DT_abs - CT_abs gets smaller. When the deadline
time expires, DT_abs - CT_abs begins to grow negative. A proper time expires, DT_abs - CT_abs begins to grow negative. A proper
selection for SAFETY_FACTOR allows it to go _slightly negative_ but selection for SAFETY_FACTOR allows it to go _slightly negative_ but
for an intermediate point to _detect_ that it has gone negative. for an intermediate point to _detect_ that it has gone negative.
Note that in modular arithmetic, "slightly negative" means _exactly_ Note that in modular arithmetic, "slightly negative" means _exactly_
the same as "almost as large as the modulus (i.e., 2^N)". Now the same as "almost as large as the modulus (i.e., 2^N)". Now
consider the test condition ((CT - DT) mod 2^N) > SAFETY_FACTOR*2^N. consider the test condition ((CT - DT) mod 2^N) > SAFETY_FACTOR*2^N.
(DT_abs - OT_abs) < 2^N*(1-SAFETY_FACTOR) satifies the test condition (DT_abs - OT_abs) < 2^N*(1-SAFETY_FACTOR) satisfies the test
when CT_abs == OT_abs (i.e., when the packet is launched). In condition when CT_abs == OT_abs (i.e., when the packet is launched).
modular arithmetic, 2^N*(1-SAFETY_FACTOR) == 2^N - 2^N*SAFETY_FACTOR In modular arithmetic, 2^N*(1-SAFETY_FACTOR) == 2^N -
== -2^N*(SAFETY_FACTOR). Then DT_abs - OT_abs < 2^N*SAFETY_FACTOR == -2^N*(SAFETY_FACTOR). Then DT_abs - OT_abs <
-2^N*(1-SAFETY_FACTOR). Inverting the inequality, OT_abs - DT_abs > -2^N*(1-SAFETY_FACTOR). Inverting the inequality, OT_abs - DT_abs >
2^N*(1-SAFETY_FACTOR), and thus at launch CT_abs - DT_abs > 2^N*(1-SAFETY_FACTOR), and thus at launch CT_abs - DT_abs >
2^N*(1-SAFETY_FACTOR). 2^N*(1-SAFETY_FACTOR).
As CT_abs grows larger, CT_abs - DT_abs gets LARGER in (non-negative) As CT_abs grows larger, CT_abs - DT_abs gets LARGER in (non-negative)
modular arithmetic until the time at which CT_ABS == DT_ABS, and modular arithmetic until the time at which CT_ABS == DT_ABS, and
suddenly CT_ABS - DT_abs becomes zero. Also suddenly, the test suddenly CT_ABS - DT_abs becomes zero. Also suddenly, the test
condition is no longer fulfilled. condition is no longer fulfilled.
As CT_abs grows still larger, CT_abs > DT_abs, and we need to detect As CT_abs grows still larger, CT_abs > DT_abs, and we need to detect
 End of changes. 5 change blocks. 
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