Internet DRAFT - draft-pu-6lo-multipath-transmission
draft-pu-6lo-multipath-transmission
6lo C. Pu
Internet Draft Y. Wang
Intended status: Standards Track H. Wang
Expires: March 25, 2019 Y. Yang
P. Wang
Chongqing University of
Posts and Telecommunications
September 21, 2018
Multipath Transmission for 6LoWPAN Networks
draft-pu-6lo-multipath-transmission-03
Abstract
This document provides a multipath transmission method for 6LoWPAN
Networks, which can effectively provide the transmission redundancy
for packets. It is suitable for high-reliability networks,
especially for IPv6-based industrial wireless scenarios.
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Table of Contents
1. Introduction ................................................ 2
2. 6LoWPAN Multipath Header Format.............................. 3
3. Architecture ................................................ 3
4. Number of Paths Destination.................................. 4
5. Multipath Distribution....................................... 5
6. Packet Replication and Elimination........................... 7
7. Security Considerations...................................... 8
8. IANA Considerations ......................................... 8
9. References .................................................. 8
9.1. Normative References.................................... 8
9.2. Informative References.................................. 9
Authors' Addresses ............................................ 10
1. Introduction
6LoWPAN can deploy large-scale and high-density wireless personal
area network devices with its high popularity, applicability, and
more address space. However, due to the low processing power, the
limited energy and the poor communication environment of the 6LoWPAN
network, packets are easily lost during transmission, which causes
transmission failure. The use of multipath packet transmission
technology in 6LoWPAN is of great significance for improving
communication reliability and transmission performance. It is well
known that RPL as a routing protocol standardized by IETF, is an
efficient distance vector protocol for wireless sensor networks,
which has designed a series of new mechanisms [RFC6550], and is
widely used in 6LoWPAN. Aiming at the explicit requirement of multi-
path packet transmission for 6LoWPAN, this document proposes an RPL-
based multipath transmission method, which improves the success rate
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of packets transmission in uplink networks and further enhances the
transmission reliability.
2. 6LoWPAN Multipath Header Format
6LoWPAN multipath header designed at the adaptation layer contains
the multipath header type field, the sequence number field of the
multipath package (SequenceNumber) and the path number field
(PathCount) [RFC4944], as depicted in Figure 1.
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multipath | Sequence Number | Path Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: 6LoWPAN Multipath Header Format
Field definitions are as follows.
Multipath: Different types of headers at the adaptation layer must
have a length of 8-bit header type field. The multipath field is
the header type field of 6LoWPAN Multipath Header that uses the
Dispatch Value Bit Pattern of 11101000.
Sequence Number: This field contains the unique sequence number
SequenceNumber of packets, and its length is 16 bits.
Path Number: This field includes the number of paths PathCount that
needs to be filled in the packet, and its length is 8 bit.
3. Architecture
The following figure 2 shows the architecture of the 6LoWPAN
protocol stack. In this architecture, the IP layer uses RPL to
realize the multipath transmission. Moreover, at the adaptation
layer, the multipath transmission entity is achieved by designing a
multipath header. The encapsulation of multipath packets and the
transmission of multipath packets can be implemented by using above
methods.
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+---------------------------------------------------+
| COAP Application Layer XMPP |
|---------------------------------------------------|
| UDP Transport Layer |
|---------------------------------------------------|
| ---------- --------------|
| |RPL|IPv6| IP Layer | Multipath||
| ---------- |Transmission||
| --------------|
|---------------------------------------------------|
| ------------------|
| Fragmentation Adaptation Layer| Multipath||
| Header Compression |Transport Entity||
| ------------------|
|---------------------------------------------------|
| CSMA/CA Mac Layer |
|---------------------------------------------------|
| Channel Detection Physical Layer |
+---------------------------------------------------+
Figure 2: 6LoWPAN Protocol Stack Architecture
Before the source node sends a message, it is necessary to determine
the number of paths P according to reliability requirements. Then we
need to assign one or more paths for each parent node at the IP
layer through the rank value. The rank value is calculated according
to the residual energy value and the hop value to the sink node from
the source node [RFC6551], [RFC6552]. The number of paths is
encapsulated into the multipath header of the message at the
adaptation layer before sending the message to the parent node. In
addition, each intermediate routing node forwards the message
according to the above method until it reaches the sink node.
4. Number of Paths Destination
Before the source node sends packets, it is needed to first
determine the number of transmission paths. By determining the
number of suitable paths, the end-to-end transmission success rate
can be effectively improved, and the transmission reliability of the
network can be further improved.
ETX refers to the number of expected transmissions of a link and is
an important criterion for evaluating the quality of links in the
network. This paper uses ETX to confirm the number of paths and
balance the link quality of each path. At the same time, it selects
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the path with better quality, thereby increases the transmission
success rate of the network.
Assume that there are n paths in the network, each path has a, b, c,
d,...links, then the total ETX value of path a can be calculated by
following formula:
E1 = L1 + L2 + ... + La.
Similarly, the total ETX values of the path b, path c, and path d
are
E2 = L1+L2+...+Lb, E3 = L1+L2+...+Lc, E4 = L1+L2+...+Ld, and
so on.
Among them, li represents the ETX of the link i in each path, so the
transmission success rate of the path a is
p1 = 1 / E1.
Similarly, the transmission success rate of the path b, path c, and
path d are
p2 = 1 / E2, p3 = 1 / E3, p4 = 1 / E4, and so on.
Then, the transmission success rate of the entire network is the sum
of the transmission success rates of all the paths, that is
p = p1 + p2 + p3 + ... + pi + ... + pn.
Where p represents the success rate of the entire network, and pi
represents the transmission success rate of path i. Sort p1 to pn
from largest to smallest, followed by p11, p12, p13,..., p1i,...p1n.
In order to ensure the success rate of one transmission, calculating
the following formula:
p = p11 + p12 + p13 + ... + p1i >= 1.
When the above formula is established, then i is the number of
required path.
5. Multipath Distribution
If the required number of paths P is greater than the total number
of parent nodes N in the collection of RPL parent nodes, multiple
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paths are assigned to each parent node according to the size
relation among the rank values of all parent nodes. The following
formula is used.
Pm = round (P/Rm/R) where R = 1/R1 + 1/R2 + ... + 1/Rn
Here, round() presents the rounding function, rounding for the
calculation result of (P/Rm/R). P is the total number of paths. Pm
shows the number of paths allocated for parent node m. Rm represents
the Rank value corresponding to the parent node m (m=1,2,...n). The
above situation is shown as Figure 3.
+---------------------------------------------------+
| rank2=500 P2=1 |
| +------------>(R1)----> ..... |
| | |
| | |
| | /---->(R3)---->(R4)----> .....\ |
| |rank1=100 P1=5/ \ |
|(S) ---------->(R2).....--->(R5)--->(R6)---> ...(D)|
| |P=8 \ / |
| | \---->(R7)---->(R8)----> ...../ |
| | |
| |rank3=200 P3=2 /----> ..... |
| +---------------->(R9) |
| \----> ..... |
+---------------------------------------------------+
Figure 3: The Transmission Process of P>N
If the number of paths P is less than or equal to the total number
of parent nodes, P rank values are selected according to the rise
order of rank values, and one path is assigned to the parent node
corresponding to each rank value, as shown in Figure 4.
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+---------------------------------------------------+
| rank2=500 P2=1 |
| +---------------->(R1)---->(R2)---->(R3)......... |
| | | |
| | rank1=100 P1=1 | |
| | /-------------->(R4)---->(R5)---->(R6)......\ | |
| |/ \| |
|(S)P=3 (D)|
| .\rank3=200 P3=1 /. |
| . \-------------->(R7)---->(R8)---->(R9)....../ . |
| . . |
| . rank4=600 P4=0 . |
| ..................(10)....(R11)....(R12)......... |
| |
+---------------------------------------------------+
Figure 4: The Transmission Process of P<=N
6. Packet Replication and Elimination
The process of packet multipath transmission also includes packet
replication and elimination. A detailed description is given as
following five steps.
1) When the multipath transport entity of the adaptation layer
receives the packet from the upper layer of the protocol stack, it
first confirms the total number of paths P of the transmission
packet according to the reliability requirements of the packet. When
P is less than or equal to 1, it indicates that the packet does not
need to use multipath transmission, then the packet can be forwarded
directly.
2) When the total number of paths P is larger than 1, the number of
the replicated packets PathCount that needs to be forwarded by each
parent node in the collection of RPL parent nodes is allocated using
the multipath packet allocation method [I-D.ietf-detnet-
architecture], [I-D.ietf-detnet-problem-statement].
3) For the parent node that PathCount is greater than or equal to
1, the multipath transport entity replicates the packet and adds the
multipath header at the adaptation layer, and then sends the packet
to the parent node. In this case, the packet sequence number
SequenceNumber of the multipath header in all replicated packets
must be concurrent and it can be accumulated when the next new
packet is sent. The path number field is filled with the
corresponding number of copies PathCount. For the parent node whose
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number of copies PathCount is less than 1, the source node does not
send the packet.
4) After the intermediate routing node receives the packet
including the multipath header, it judges whether the number of
paths PathCount is equal to 1 in the multipath header. If PathCount
is equal to 1, the intermediate node sends the packet directly with
the value of each field in the multipath header constant. If
PathCount is greater than 1, the node replicate PathCount copies of
the packet and distributes them to multiple paths. Repeating step 2
and 3, and in step 2, P is equal to PathCount. In step 3, the new
multipath header is not added, the SequenceNumber of the packet is
unchanged, and the path number field is filled with the new
corresponding number of copies.
5) When a destination node receives a packet containing the
multipath header, it can distinguish whether the packet has been
received according to the source address and the packet sequence
number in the multipath header. If the destination node has not
received the packet before, the node forwards the packet to its
upper layer protocol directly. Otherwise, the node discards the
packet [I-D.ietf-detnet-architecture], [I-D.ietf-detnet-problem-
statement].
7. Security Considerations
This document does not add any new security considerations other
than what is already mentioned in the referenced technology.
8. IANA Considerations
This document creates an IANA registry for 6LoWPAN Multipath Header
Type, and assigns the following dispatch type values:
11101000: for 6LoWPAN Multipath Header Type.
9. References
9.1. Normative References
[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, March 2012,
<http://www.rfc-editor.org/info/rfc6550>.
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[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4 Networks",
RFC 4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., and
D. Barthel, "Routing Metrics Used for Path Calculation in
Low-Power and Lossy Networks", RFC 6551, March 2012,
<http://www.rfc-editor.org/info/rfc6551>.
[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)", RFC 6552,
March 2012, <http://www.rfc-editor.org/info/rfc6552>.
9.2. Informative References
[I-D.ietf-detnet-architecture]
Finn, N. and P. Thubert, "Deterministic Networking
Architecture", draft-ietf-detnet-architecture-04 (work in
progress), August 2017.
[I-D.ietf-detnet-problem-statement]
Finn, N. and P. Thubert, "Deterministic Networking Problem
Statement", draft-ietf-detnet-problem-statement-02 (work in
progress), September 2016.
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Authors' Addresses
Chenggen Pu
Chongqing University of Posts and Telecommunications
2 Chongwen Road
Chongqing, 400065
China
Phone: (86)-23-6246-1061
Email: mentospcg@163.com
Yadong Wang
Chongqing University of Posts and Telecommunications
2 Chongwen Road
Chongqing, 400065
China
Phone: (86)-23-6246-1061
Email: 13618266302@163.com
Heng Wang
Chongqing University of Posts and Telecommunications
2 Chongwen Road
Chongqing, 400065
China
Phone: (86)-23-6248-7845
Email: wangheng@cqupt.edu.cn
Yi Yang
Chongqing University of Posts and Telecommunications
2 Chongwen Road
Chongqing, 400065
China
Phone: (86)-23-6246-1061
Email: 15023705316@163.com
Ping Wang
Chongqing University of Posts and Telecommunications
2 Chongwen Road
Chongqing, 400065
China
Phone: (86)-23-6246-1061
Email: wangping@cqupt.edu.cn
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