Internet DRAFT - draft-lijo-6lo-expiration-time
draft-lijo-6lo-expiration-time
6lo Lijo Thomas
Internet-Draft C-DAC
Intended status: Standards Track P. Akshay
Expires: January 4, 2018 Indian Institute of Science
Satish Anamalamudi
Huaiyin Institute of Technology
S.V.R.Anand
Malati Hegde
Indian Institute of Science
C. Perkins
Futurewei
July 3, 2017
Packet Delivery Deadline time in 6LoWPAN Routing Header
draft-lijo-6lo-expiration-time-04
Abstract
This document specifies a new type for the 6LoWPAN routing header
containing the delivery deadline time for data packets. The deadline
time enables forwarding and scheduling decisions for time critical
IoT M2M applications that need deterministic delay guarantees over
constrained networks and operate within time-synchronized networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 4, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. 6LoRHE Generic Format . . . . . . . . . . . . . . . . . . . . 3
4. Deadline-6LoRHE . . . . . . . . . . . . . . . . . . . . . . . 3
5. Deadline-6LoRHE Format . . . . . . . . . . . . . . . . . . . 4
6. Deadline-6LoRHE in Three Network Scenarios . . . . . . . . . 6
6.1. Scenario 1: Endpoints in the same DODAG (N1) in non-
storing mode. . . . . . . . . . . . . . . . . . . . . . . 6
6.2. Scenario 2: Endpoints in Networks with Dissimilar L2
Technologies. . . . . . . . . . . . . . . . . . . . . . . 7
6.3. Scenario 3: Packet transmission across different DODAGs
(N1 to N2). . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Low Power and Lossy Networks (LLNs) are likely to be deployed for
real time industrial applications requiring end-to-end delay
guarantees [I-D.grossman-detnet-use-cases]. A Deterministic Network
("detnet") typically requires some data packets to reach their
receivers within strict time bounds. Intermediate nodes use the
deadline information to make appropriate packet forwarding and
scheduling decisions to meet the time bounds.
The draft [I-D.ietf-roll-routing-dispatch] specifies the 6LoWPAN
Routing Header (6LoRH), compression schemes for RPL routing (source
routing) operation [RFC6554], header compression of RPL Packet
Information [RFC6553], and IP-in-IP encapsulation. This document
specifies a new Deadline-6LoRHE type for the 6LoWPAN Dispatch Page 1,
so that the deadline time of data packets can be included within the
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6LoWPAN routing header. This document also specifies handling of the
deadline time when packets traverse through time-synchronized
networks operating in different timezones or distinct reference
clocks.
2. Terminology
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
[RFC2119].
This document uses terminology consistent with the terminology used
in [RFC6550] and [I-D.ietf-6tisch-terminology]. Also, in this
document, the terms "expiration time", "delivery deadline time", and
"deadline" are used interchangeably with the same meaning.
3. 6LoRHE Generic Format
Note: this section is not normative. It is included for convenience,
and may be deleted in a later revision of this document. The generic
header format of the 6LoRHE is specified in
[I-D.ietf-roll-routing-dispatch]. Figure 1 illustrates the 6LoRHE
generic format.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|1| Length | Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
<-- length -->
Figure 1: 6LoRHE format
o Length: Length of the 6LoRHE expressed in bytes, excluding the
first 2 bytes. This enables a node to skip a 6LoRHE if the Type
is not recognized/supported.
o Type: Type of the 6LoRHE.
o length: variable
4. Deadline-6LoRHE
The Deadline-6LoRHE (see Figure 2) is an elective 6LoRH (i.e., a
6loRHE) that provides the deadline time (DT) for an IPv6 datagram in
a compressed form. Along with the deadline, the header can include
the packet Origination Time (OT), to enable a close estimate of the
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total delay incurred by a packet. The OT field is initialized by the
sender using the current time at the outgoing network interface
through which the packet is forwarded.
The deadline field contains the value of the delivery deadline time
for the packet. The packet SHOULD be delivered to the Receiver
before this time.
packet_deadline_time = packet_origination_time + max_delay
All nodes within the network SHOULD process the Deadline-6LoRHE in
order to support delay-sensitive deterministic applications. The
packet deadline time (DT) and origination time (OT) are represented
in time units determined by a scaling parameter in the routing
header. One of the time units is the Network ASN (Absolute Slot
Number) which can be used in case of a time slotted synchronized
network, for instance a 6TiSCH network, where global time is
maintained in the units of slot lengths of a certain resolution.
The delay experienced by packets in the network is a useful metric
for network diagnostics and performance monitoring. Whenever the
packets crosses into a network using a different reference clock, the
Origination Time field is updated to represent the same Origination
Time as expressed using the reference clock of the outgoing interface
into the new network. This is the same as the current time when the
packet is transmitted into the new network, minus the delay already
experienced by the packet, say 't'. In effect, to the newly entered
network, the packet will appear to have originated 't' time units
earlier with respect to the reference clock of the new network.
Origination Time in new network = current_time_in_new_network -
delay_already_experienced_in_previous_network(s)
5. Deadline-6LoRHE Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|1| Length | 6LoRH Type |O|D| DTL | OTL | TU| EXP | Rsv |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DT (variable length) | OT(variable length)(optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Deadline-6LoRHE format
Length (5 bits): Length represents the total length of the Deadline-
6LoRHE type measured in octets.
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6LoRH Type: TBD
O flag (1bit): Indicates the presence of Origination Time field. '1'
means the OT field is present, and '0' means it is absent.
D flag (1 bit): The 'D' flag, set by the Sender, indicates the action
to be taken when a 6LR detects that the deadline time has elapsed.
If 'D' bit is 1, then the 6LR SHOULD drop the packet if the deadline
time is elapsed. If 'D' bit is 0, then the 6LR MAY ignore the
deadline time and forward the packet.
DTL (3 bits): Length of DT field.
OTL (3 bits) : Length of OT field.
For example, DTL = 000 means the deadline time in the 6LoRHE is 1
octet (8 bits) long. Similarly, OTL = 111 means the origination
time is 8 octets (64 bits) long.
TU (2 bits) : Indicates the time units for DT and OT fields
00 : Time represented in microseconds
01 : Time represented in seconds
10 : Network ASN
11 : Reserved
EXP (3 bits) : Multiplication factor expressed as exponent of 10.
The value of the DT field is multiplied by 10 to this power, to
get the actual deadline time in the units represented by TU. The
default value of EXP is 000, so that the DT field is unaffected.
Rsv (3 bits) : Reserved
DT Value (8..64-bit) : Deadline Time value
OT Value (8..64-bit) : Origination Time value
Whenever a sender initiates the IP datagram, it includes the
Deadline-6LoRHE along with other 6LoRH information.
Example: Consider a 6TiSCH network with time-slot length of 10ms.
Let the current ASN when the packet is originated be 54400, and the
maximum allowable delay (max_delay) for the packet delivery is 1
second from the packet origination, then:
deadline_time = packet_origination_time + max_delay
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= 55400 + 100 (in Network ASNs)
= 55500(Network ASNs)
Deadline-6LoRHE encoding with 'O' flag set to 1 :
DTL = 001, OTL = 001, TU = '10', EXP = 2, DT = 0x22B, OT = 0x22A
6. Deadline-6LoRHE in Three Network Scenarios
In this section, Deadline-6LoRHE operation is described for 3 network
scenarios. Figure 3 depicts a constrained time-synchronized LLN that
has two subnets N1 and N2, connected through LBRs
[I-D.ietf-6lo-backbone-router] with different reference clock times
T1 and T2.
+-------------------+
| Time Synchronized |
| Network |
+---------+---------+
|
|
|
+--------------+--------------+
| |
+-----+ +-----+
| | Backbone | | Backbone
o | | router | | router
+-----+ +-----+
o o o
o o o o o o o o o
o LLN o o LLN o o
o o o o o o o o o
6LoWPAN Network (subnet N1) 6LoWPAN Network (subnet N2)
Figure 3: Intra-network Timezone Scenario
6.1. Scenario 1: Endpoints in the same DODAG (N1) in non-storing mode.
In scenario 1, shown in Figure 4, the Sender 'S' has an IP datagram
to be routed to a Receiver 'R' within the same DODAG. For the route
segment from Sender to 6LBR, the Sender includes a Deadline-6LoRHE by
encoding the deadline time contained in the inband-OAM header
extension. Then 6LR begins hop-by-hop operation to forward the
packet towards the 6LBR. Once 6LBR receives the IP datagram, it
generates a IPv6-in-IPv6 encapsulated packet when sending the packet
downwards to the Receiver [I-D.ietf-roll-useofrplinfo]. The 6LBR
copies the Deadline-6LoRHE from the Sender originated IP header to
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the outer IP header. The Deadline-6LoRHE contained in the inner IP
header is elided.
+-------+
^ | 6LBR | |
| | | |
| +-------+ |
Default | (F)/ /| \ | IP-in-IP
routing | / \ / | \ | Encapsulation
| / \ (C) | (D) |
| (A) (B) / | / |\ |
| /|\ |\: (E) : R |
S : : : / \ V
Figure 4: End points within same DODAG(subnet N1)
At the tunnel endpoint of IPv6-in-IPv6 encapsulation, the Deadline-
6LoRHE is copied back from the outer header to inner header, and the
inner IP packet is delivered to 'R'.
6.2. Scenario 2: Endpoints in Networks with Dissimilar L2 Technologies.
In scenario 2, shown in Figure 5, the Sender 'S' (belonging to DODAG
1) has IP datagram to be routed to a Receiver 'R' over a time-
synchronized IPv6 network. For the route segment from 'S' to 6LBR,
'S' includes a Deadline-6LoRHE. Subsequently, 6LR will perform hop-
by-hop operation to forward the packet towards the 6LBR. Once the IP
datagram reaches 6LBR of DODAG1, it encodes the deadline time (and,
if available, the origination time) into the In-band OAM header
extension, [I-D.brockners-inband-oam-data] and passes the datagram to
the IPv6 layer for further routing.
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+----------------+
| Time |
| synchronized |------R
| Network |
+----------------+
|
|
----------+-----------
^ |
| +---+---+
| | 6LBR |
Default | | |
routing | +------++
| (F)/ /| \
| / \ / | \
| / \ (C) | (D)
: (A) (B) / | / |\
/|\ |\: (E) :
S : : : / \
: :
Figure 5: Packet transmission in Dissimilar L2 Technologies or
Internet
The IP datagram is routed to another time synchronized deterministic
network following its own distinct reference clock, so the deadline
time in In-band OAM has to be updated according to the measurement of
the current time in the new network.
6.3. Scenario 3: Packet transmission across different DODAGs (N1 to
N2).
Consider the scenario depicted in Figure 6, in which the Sender 'S'
(belonging to DODAG 1) has an IP datagram to be sent to Receiver 'R'
belonging to another DODAG (DODAG 2). The operation of this scenario
can be decomposed into combination of case 1 and case 2 scenarios.
For the route segment from 'S' to 6LBR, 'S' includes the Deadline-
6LoRHE. Subsequently, each 6LR will perform hop-by-hop operation to
forward the packet towards the 6LBR. Once the IP datagram reaches
6LBR1 of DODAG1, it applies the same rule as described in Case 2
while routing the packet to LBR2 over a (likely) time synchronized
wired backhaul. The wired side of LBR2 can be mapped to receiver of
Case 2. Once the packet reaches LBR2, it updates the Deadline-6LoRHE
by adding the current time of DODAG2. Further, it generates an IPv6-
in-IPv6 encapsulated packet when sending the packet downstream to the
Receiver [I-D.ietf-roll-useofrplinfo].
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Time Synchronized Network
-+---------------------------+-
| |
DODAG1 +---+---+ +---+---+ DODAG2
Instance 1 | 6LBR1 | | 6LBR2 | Instance 2
| | | | |
+-------+ +-------+ |
(F)/ /| \ (F)/ /| \ |
/ \ / | \ / \ / | \ |
/ \ (C) | (D) / \ (C) | (D) |IP-in-IP
(A) (B) / | / |\ (A) (B) / | / |\ | Encapsulation
/|\ |\: (E) : : /|\ |\: (E) : :|
S : : : / \ : : : : / \ |
: : : R V
Network N1, time zone T1 NetWork N2, time zone T2
Figure 6: Packet transmission in different DODAGs(N1 to N2)
Consider an example of a 6TiSCH network in which S in DODAG1
generates the packet at ASN 20000 to R in DODAG2. Let the maximum
allowable delay be 1 second. The time-slot length in DODAG1 and
DODAG2 is assumed to be 10ms. Once the deadline time is encoded in
Deadline-6LoRHE, the packet is forwarded to LBR of DODAG1. Suppose
the packet reaches LBR of DODAG1 at ASN 20050.
current_time = ASN at LBR * slot_length_value
remaining_time = deadline_time - current_time
= ((packet_origination_time + max_delay) - current time)
= (20000 + 100) - 20050
= 50 (in Network ASNs)
= 50 * 10^3 milliseconds.
The remaining time is encoded in In-Band OAM (see Case 2) and
forwarded to LBR2 over a different L2-interface, typically wired.
Once the packet reaches LBR2, the deadline time in Deadline-6LoRHE is
adjusted by adding or subtracting the difference between the
reference clocks of the two networks, before forwarding the packet to
its connected 6TiSCH network.
7. IANA Considerations
This document defines a new 6LoWPAN Timestamp Header Type, and
assigns a value (TBD) from the 6LoWPAN Dispatch Page1 number space.
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6LoRH Type Value
+------------------+--------+
| Deadline-6LoRHE | TBD |
+------------------+--------+
Figure 7: Deadline-6LoRHE type
8. Security Considerations
The security considerations of [RFC4944], [RFC6282] and [RFC6553]
apply. Using a compressed format as opposed to the full in-line
format is logically equivalent and does not create an opening for a
new threat when compared to [RFC6550], [RFC6553] and [RFC6554].
9. Acknowledgements
The authors thank Pascal Thubert for suggesting the idea and
encouraging the work. Thanks to Shwetha Bhandari's suggestions which
were instrumental in extending the timing information to
heterogeneous networks. The authors acknowledge the 6TiSCH WG
members for their inputs on the mailing list. Special thanks to
Jerry Daniel,Shalu Rajendran, Seema Kumar, Avinash Mohan and Anita
Varghese for their support and valuable feedback.
10. References
10.1. Normative References
[I-D.ietf-6tisch-terminology]
Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
"Terminology in IPv6 over the TSCH mode of IEEE
802.15.4e", draft-ietf-6tisch-terminology-09 (work in
progress), June 2017.
[I-D.ietf-roll-routing-dispatch]
Thubert, P., Bormann, C., Toutain, L., and R. Cragie,
"6LoWPAN Routing Header", draft-ietf-roll-routing-
dispatch-05 (work in progress), October 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.
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[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<http://www.rfc-editor.org/info/rfc6550>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<http://www.rfc-editor.org/info/rfc6553>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<http://www.rfc-editor.org/info/rfc6554>.
10.2. Informative References
[I-D.brockners-inband-oam-data]
Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
P., <>, R., and d. daniel.bernier@bell.ca, "Data Fields
for In-situ OAM", draft-brockners-inband-oam-data-05 (work
in progress), May 2017.
[I-D.grossman-detnet-use-cases]
Grossman, E., Gunther, C., Thubert, P., Wetterwald, P.,
Raymond, J., Korhonen, J., Kaneko, Y., Das, S., and Y.
Zha, "Deterministic Networking Use Cases", draft-grossman-
detnet-use-cases-01 (work in progress), November 2015.
[I-D.ietf-6lo-backbone-router]
Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo-
backbone-router-03 (work in progress), January 2017.
[I-D.ietf-roll-useofrplinfo]
Robles, I., Richardson, M., and P. Thubert, "When to use
RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
useofrplinfo-15 (work in progress), June 2017.
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[I-D.vilajosana-6tisch-minimal]
Vilajosana, X. and K. Pister, "Minimal 6TiSCH
Configuration", draft-vilajosana-6tisch-minimal-00 (work
in progress), October 2013.
Authors' Addresses
Lijo Thomas
C-DAC
Trivandrum 695033
India
Email: lijo@cdac.in
P.M. Akshay
Indian Institute of Science
Bangalore 560012
India
Email: akshaypm@ece.iisc.ernet.in
Satish Anamalamudi
Huaiyin Institute of Technology
No.89 North Beijing Road, Qinghe District
Huaian
China
Email: satishnaidu80@gmail.com
S.V.R Anand
Indian Institute of Science
Bangalore 560012
India
Email: anand@ece.iisc.ernet.in
Malati Hegde
Indian Institute of Science
Bangalore 560012
India
Email: malati@ece.iisc.ernet.in
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Charles E. Perkins
Futurewei
2330 Central Expressway
Santa Clara 95050
Unites States
Email: charliep@computer.org
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