Internet DRAFT - draft-aguilar-lpwan-schc-streaming
draft-aguilar-lpwan-schc-streaming
lpwan Working Group S. Aguilar
Internet-Draft C. Gomez
Updates: 8724 (if approved) Universitat Politecnica de Catalunya
Intended status: Standards Track 8 March 2023
Expires: 9 September 2023
SCHC Streaming Mode
draft-aguilar-lpwan-schc-streaming-00
Abstract
This documents presents an update of SCHC [RFC8724] by providing a
new F/R mode called SCHC Streaming mode.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 9 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SCHC Streaming . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Transfer Cycles . . . . . . . . . . . . . . . . . . . . . 4
3.2. ACK Behaviour . . . . . . . . . . . . . . . . . . . . . . 6
4. SCHC Streaming mode examples . . . . . . . . . . . . . . . . 6
5. SCHC Streaming mode YANG Data Model . . . . . . . . . . . . . 14
5.1. SCHC YANG Data Model Extension . . . . . . . . . . . . . 14
5.2. SCHC YANG Tree Extension . . . . . . . . . . . . . . . . 14
6. Security considerations . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
SCHC [RFC8724] provides Fragmentation/Reassembly (F/R) modes, i.e.,
No-ACK, ACK-Always and ACK-on-Error. These modes allow for SCHC
Packets larger than the Maximum Transmission Unit (MTU) of the
underlying Layer 2 (L2) to be transferred between the sender and
receiver with a range of reliability options, including SCHC Fragment
retransmissions, over delay tolerant networks. The available F/R
modes allow transmitting non-fragmented SCHC Packets concurrently
with fragmented SCHC Fragments, and SCHC Packet interleaving.
However, SCHC does not provide an optimal F/R mode for a continuous
transmission of un-fragmented SCHC Packets, i.e, streaming of SCHC
Packets smaller than, or of the same size as, the L2 MTU.
The streaming of SCHC Packets can be used to send, e.g., sensor
measurements or the location coordinates of an asset tracker, which
are sent every number of minutes and are optimized to fit in only one
SCHC Fragment, with or without SCHC Compression. These SCHC Packets
may not require fragmentation but require reliability, as some
fragment losses may be incurred due to intermittent connectivity
(e.g., vehicles going into tunnels, no coverage areas) or
opportunistic coverage (e.g., coverage is available for certain time
windows, of duration and frequency that might not be deterministic).
With current SCHC F/R modes, each sensor measurement or location
information can be sent as a compressed or un-compressed SCHC Packet,
with different reliability options, however, each SCHC Packet will
require a SCHC ACK, even if it is of only one SCHC Fragment in size.
In networks, e.g., LPWANs [RFC8376], the downlink traffic or network
capacity may be limited. [I.D.Compound ACK] provides an optimization
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in the ACK traffic by grouping the feedback of several windows of
tiles in the same ACK message, providing flexibility on when the
receiver sends feedback.
The present document extends [RFC8724] with a new F/R mode called
SCHC Streaming. This F/R mode optimized the overhead of current F/R
modes for a contiuos streaming of compressed or un-compressed SCHC
Packets which require one SCHC Fragment to be transferred. The SCHC
Streaming mode provides different configuration option on when the
receiver can provide feedback, therefore adapting to the specifics of
each network, e.g., the amount of ACK traffic that can be supported,
application delay tolerance, L2 MTU size and the maximum number of
window bitmaps that can be carried in a SCHC Compound ACK.
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
It is assumed that the reader is familiar with the terms and
mechanisms defined in [RFC8376] and in [RFC8724], specially
Section 8.
3. SCHC Streaming
The SCHC Streaming mode supports L2 technologies that have variable
MTU and out-of-order delivery (to some extent). It requires an L2
that provides a feedback path from the reassembler to the fragmenter.
SCHC Streaming mode uses windows, with all tiles, except for the last
one, of equal size (regular size). The last tile MAY be smaller or
equal to a regular tile.
A SCHC Fragment carries one or several contiguous tiles, which may
span multiple windows from the same DTag value. A SCHC Compound ACK
reports on the reception of one window of tiles or several windows of
tiles, each one identified by its window number and corresponding to
the same DTag value.
Each Profile, for each RuleID value, MUST define:
* the tile size (a tile does not need to be multiple of an L2 Word,
but it MUST be at least the size of an L2 Word),
* the value of M,
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* the value of N,
* the value of WINDOW_SIZE, which MUST be strictly less than 2^N,
* the size and algorithm for the RCS field,
* the value of T,
* the value of MAX_ACK_REQUESTS,
* the expiration time of the Retransmission Timer,
* the expiration time of the Inactivity Timer,
* when the SCHC Compound ACKs are sent.
For each active RuleID value, the sender MUST maintain:
* one Attempts counter, and
* one Retransmission Timer.
For each active RuleID value, the receiver MUST maintain:
* one Inactivity Timer, and
* one Attempts counter.
3.1. Transfer Cycles
In SCHC Streaming mode the flow of tiles is continuous and it is
divided into cycles. There are two cycles, the Window Cycle and the
DTag Cycle (see Figure 1). To uniquely identify each tile, a
combination of DTag, Window Number and FCN is used in each DTag
Cycle.
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+---------------------------------------------...-----------....----...
| SCHC Streaming flow of SCHC Packets
+---------------------------------------------...-----------...-----...
Tile# | 4 | 3 | 2 | 1 | 0 | 4 | 3 | 2 | 1 | 0 | 4 | ... | 0 | 4 | ... | 0 |...
Window# |-------- 0 --------|-------- 1 --------|- 0 ... 1 -|- 0 ... 1 -|...
DTag# |-------------------- 0 ----------------|----- 1 -----|----- 0 -----|...
Window Cycle# |---------------------0-----------------|------1------|------0------|...
DTag Cycle# |-------------------------------0---------------------|------1------|...
^ ^ ^
| | |
Window Cycle 0 start Window Cycle 0 ends |
^ |
| |
DTag Cycle 0 start DTag Cycle 0 ends
Figure 1: SCHC Packets streaming carried in Tiles and Windows
using the SCHC Streaming Mode. M = 1 bit (Window Cycle of 2
Windows) and DTag = 1 bit (DTag Cycle of 2 Window Cycles, i.e., 4
Windows)
The sender will begin the first DTag and Window Cycle by sending
tiles using DTag = 0 and Window Number = 0 (the tile index, i.e., the
FCN, MUST be decremented by 1 from WINDOW_SIZE - 1 downward). After
each window of tiles, the Window Number is increased. Current Window
Cycle ends once the Window Number reaches its maximum value and the
last fragment of this window is sent. Next Window Cycle will begin
by increasing the DTag value by one, and resetting the Window Number
and FCN values. The number of Window Cycles without repeating the
same DTag, Window Number and FCN value depends on the size of the
DTag field, which determines the DTag Cycle. After the DTag reaches
its maximum value, and therefore the end of the DTag Cycle, it MUST
be reset. To manage the receiver feedback, the Receiver MUST send at
least one SCHC Compound ACK per DTag Cycle, i.e., before the DTag is
reset, indicating tiles losses in any of previous Window Cycles
corresponding to this DTag Cycle. Only one Window Cycle MUST be
reported per SCHC Compound ACK. The SCHC Compound ACK MUST be sent
before the start of a new DTag Cycle. SCHC Fragments MAY be
delivered out-of-order in each DTag Cycle, but all tiles MUST be
received before advancing to the next DTag Cycle.
The SCHC All-1 message is used to finalize current SCHC Streaming
session in case it is needed.
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3.2. ACK Behaviour
A SCHC Compound ACK MAY be sent after the All-0 SCHC Fragment message
and MUST be sent after the All-1 SCHC Fragment message. This allows
the receiver to provide feedback after any window of tiles. The
Profile MUST specify when the sender should listen for a SCHC
Compound ACK, specially in networks which require the sender to
enable reception of incoming SCHC ACKs. The sender MAY listen after
each complete window of tiles (the All-0 message in each window),
after the All-0 of the last window of each Window Cycle or after the
All-0 of the last window of each DTag Cycle.
The receiver can send SCHC Compound ACKs:
* at the end of each Window Cycle, in the last window (with the
maximum window number), an All-0 message indicates the end of
current window, and as it is the last window of current Window
Cycle, it indicates the end of current Window Cycle. The receiver
MAY send a SCHC Compound ACK. Note that after this Window Cycle
ends, the receiver MAY request fragments of previous DTag values
(before the DTag Cycle ends).
* A success SCHC ACK MUST be sent by the receiver at the end of each
DTag Cycle, to acknowledge all SCHC Fragment before continuing to
next DTag Cycle. Note that after a new DTag Cycle begins, it is
not possible to recover SCHC Fragment from previous DTag Cycles,
as the combination of DTag, Window Number and FCN is repeated.
4. SCHC Streaming mode examples
This section provides examples of the SCHC Streaming mode. The
configuration used in these examples is as follows:
* RuleID: Same RuleID in all SCHC Fragments.
* M: 2 bits (with values 00,01,10,11)
* N: 3 bits (with values from 6 to 0 plus the All-1)
* DTag: 1 bits
* WINDOW_SIZE: 7 tiles
In Figure 2, a SCHC Streaming transmission example is shown. In this
transmission, the first 3 windows have fragment losses. The fourth
window has no fragment losses. The receiver sends a SCHC Compound
ACK reporting on the fragment losses of the first 3 windows, after
receiving the All-0 message that signal the end of current Window
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Cycle, i.e., the All-0 message of the fourth window. The sender
resends the missing fragments and continues to next Window Cycle by
increasing the DTag value.
Next Window Cycle present fragment losses that are recovered at the
end of the cycle, as the receiver sends a SCHC Compound ACK message
after receiving the All-0 message. The sender resends the missing
fragment, and as it is the end of the DTag Cycle, a success ACK is
sent by the receiver to continue the transmission in the next DTag
Cycle.
Sender Receiver
|-----DTag= 0, W=0, FCN=6 ----->|
|-----DTag= 0, W=0, FCN=5 ----->|
|-----DTag= 0, W=0, FCN=4 ----->|
|-----DTag= 0, W=0, FCN=3 ----->|
|-----DTag= 0, W=0, FCN=2 --X |
|-----DTag= 0, W=0, FCN=1 ----->|
|-----DTag= 0, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 0, W=1, FCN=6 ----->|
|-----DTag= 0, W=1, FCN=5 ----->|
|-----DTag= 0, W=1, FCN=4 ----->|
|-----DTag= 0, W=1, FCN=3 ----->|
|-----DTag= 0, W=1, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 --X |
|-----DTag= 0, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 0, W=2, FCN=6 ----->|
|-----DTag= 0, W=2, FCN=5 --X |
|-----DTag= 0, W=2, FCN=4 ----->|
|-----DTag= 0, W=2, FCN=3 ----->|
|-----DTag= 0, W=2, FCN=2 ----->|
|-----DTag= 0, W=2, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 0, W=3, FCN=6 ----->|
|-----DTag= 0, W=3, FCN=5 ----->|
|-----DTag= 0, W=3, FCN=4 ----->|
|-----DTag= 0, W=3, FCN=3 ----->|
|-----DTag= 0, W=3, FCN=2 ----->|
|-----DTag= 0, W=3, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1111111
|<--- DTag= 0, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 0, W=0, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=5 ----->|
(next Window Cycle)
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|-----DTag= 1, W=0, FCN=6 ----->|
|-----DTag= 1, W=0, FCN=5 ----->|
|-----DTag= 1, W=0, FCN=4 ----->|
|-----DTag= 1, W=0, FCN=3 ----->|
|-----DTag= 1, W=0, FCN=2 --X |
|-----DTag= 1, W=0, FCN=1 ----->|
|-----DTag= 1, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 1, W=1, FCN=6 ----->|
|-----DTag= 1, W=1, FCN=5 ----->|
|-----DTag= 1, W=1, FCN=4 ----->|
|-----DTag= 1, W=1, FCN=3 ----->|
|-----DTag= 1, W=1, FCN=2 ----->|
|-----DTag= 1, W=1, FCN=1 --X |
|-----DTag= 1, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 1, W=2, FCN=6 ----->|
|-----DTag= 1, W=2, FCN=5 --X |
|-----DTag= 1, W=2, FCN=4 ----->|
|-----DTag= 1, W=2, FCN=3 ----->|
|-----DTag= 1, W=2, FCN=2 ----->|
|-----DTag= 1, W=2, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 1, W=3, FCN=6 ----->|
|-----DTag= 1, W=3, FCN=5 ----->|
|-----DTag= 1, W=3, FCN=4 ----->|
|-----DTag= 1, W=3, FCN=3 ----->|
|-----DTag= 1, W=3, FCN=2 ----->|
|-----DTag= 1, W=3, FCN=1 ----->|
|-----DTag= 1, W=3, FCN=0 ----->| Bitmap: 1011111
|<--- DTag= 1, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 1, W=0, FCN=2 ----->|
|-----DTag= 1, W=1, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=5 ----->|
|<--- DTag= 1, ACK, W=3, C=1 ---| C=1 [success ACK is needed before moving to next DTag cycle]
(next Window and DTag Cycle)
Figure 2: SCHC Streaming mode sequence example 1
Figure 3 shows another example of SCHC Streaming mode where a SCHC
Compound ACK is sent at the ending of the DTag Cycle, recovering SCHC
Fragment losses of previous windows of the DTag Cycle. As both
Window Cycles present SCHC Fragment losses, two SCHC Compound ACKs
are sent by the receiver at the end of the DTag Cycle.
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Sender Receiver
|-----DTag= 0, W=0, FCN=6 ----->|
|-----DTag= 0, W=0, FCN=5 ----->|
|-----DTag= 0, W=0, FCN=4 ----->|
|-----DTag= 0, W=0, FCN=3 ----->|
|-----DTag= 0, W=0, FCN=2 --X |
|-----DTag= 0, W=0, FCN=1 ----->|
|-----DTag= 0, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 0, W=1, FCN=6 ----->|
|-----DTag= 0, W=1, FCN=5 ----->|
|-----DTag= 0, W=1, FCN=4 ----->|
|-----DTag= 0, W=1, FCN=3 ----->|
|-----DTag= 0, W=1, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 --X |
|-----DTag= 0, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 0, W=2, FCN=6 ----->|
|-----DTag= 0, W=2, FCN=5 --X |
|-----DTag= 0, W=2, FCN=4 ----->|
|-----DTag= 0, W=2, FCN=3 ----->|
|-----DTag= 0, W=2, FCN=2 ----->|
|-----DTag= 0, W=2, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 0, W=3, FCN=6 ----->|
|-----DTag= 0, W=3, FCN=5 ----->|
|-----DTag= 0, W=3, FCN=4 ----->|
|-----DTag= 0, W=3, FCN=3 ----->|
|-----DTag= 0, W=3, FCN=2 ----->|
|-----DTag= 0, W=3, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
(next Window Cycle)
|-----DTag= 1, W=0, FCN=6 ----->|
|-----DTag= 1, W=0, FCN=5 ----->|
|-----DTag= 1, W=0, FCN=4 ----->|
|-----DTag= 1, W=0, FCN=3 ----->|
|-----DTag= 1, W=0, FCN=2 --X |
|-----DTag= 1, W=0, FCN=1 ----->|
|-----DTag= 1, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 1, W=1, FCN=6 ----->|
|-----DTag= 1, W=1, FCN=5 ----->|
|-----DTag= 1, W=1, FCN=4 ----->|
|-----DTag= 1, W=1, FCN=3 ----->|
|-----DTag= 1, W=1, FCN=2 ----->|
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|-----DTag= 1, W=1, FCN=1 --X |
|-----DTag= 1, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 1, W=2, FCN=6 ----->|
|-----DTag= 1, W=2, FCN=5 --X |
|-----DTag= 1, W=2, FCN=4 ----->|
|-----DTag= 1, W=2, FCN=3 ----->|
|-----DTag= 1, W=2, FCN=2 ----->|
|-----DTag= 1, W=2, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 1, W=3, FCN=6 ----->|
|-----DTag= 1, W=3, FCN=5 ----->|
|-----DTag= 1, W=3, FCN=4 ----->|
|-----DTag= 1, W=3, FCN=3 ----->|
|-----DTag= 1, W=3, FCN=2 ----->|
|-----DTag= 1, W=3, FCN=1 ----->|
|-----DTag= 1, W=3, FCN=0 ----->| Bitmap: 1111111
|<--- DTag= 0, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 0, W=0, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=5 ----->|
|<--- DTag= 1, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 1, W=0, FCN=2 ----->|
|-----DTag= 1, W=1, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=5 ----->|
|<--- DTag= 1, ACK, W=3, C=1 ---| C=1 success ACK is needed before moving to next DTag cycle
(next Window and DTag Cycle)
Figure 3: SCHC Streaming mode sequence example 2
Figure 4 presents a SCHC Streaming transmission that is closed by the
sender using an All-1 message. After the All-1 message, the receiver
sends a SCHC Compound ACKs for missing fragments. The sender resends
missing fragments and waits for a success SCHC ACK indicating that
all SCHC Fragments were correctly received and that current SCHC
Streaming transmission can be closed.
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Sender Receiver
|-----DTag= 0, W=0, FCN=6 ----->|
|-----DTag= 0, W=0, FCN=5 ----->|
|-----DTag= 0, W=0, FCN=4 ----->|
|-----DTag= 0, W=0, FCN=3 ----->|
|-----DTag= 0, W=0, FCN=2 --X |
|-----DTag= 0, W=0, FCN=1 ----->|
|-----DTag= 0, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 0, W=1, FCN=6 ----->|
|-----DTag= 0, W=1, FCN=5 ----->|
|-----DTag= 0, W=1, FCN=4 ----->|
|-----DTag= 0, W=1, FCN=3 ----->|
|-----DTag= 0, W=1, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 --X |
|-----DTag= 0, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 0, W=2, FCN=6 ----->|
|-----DTag= 0, W=2, FCN=5 --X |
|-----DTag= 0, W=2, FCN=4 ----->|
|-----DTag= 0, W=2, FCN=3 ----->|
|-----DTag= 0, W=2, FCN=2 ----->|
|-----DTag= 0, W=2, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 0, W=3, FCN=6 ----->|
|-----DTag= 0, W=3, FCN=5 ----->|
|-----DTag= 0, W=3, FCN=4 ----->|
|-----DTag= 0, W=3, FCN=3 ----->|
|-----DTag= 0, W=3, FCN=2 ----->|
|-----DTag= 0, W=3, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
(next Window Cycle)
|-----DTag= 1, W=0, FCN=6 ----->|
|-----DTag= 1, W=0, FCN=5 ----->|
|-----DTag= 1, W=0, FCN=4 ----->|
|-----DTag= 1, W=0, FCN=3 ----->|
|-----DTag= 1, W=0, FCN=2 --X |
|-----DTag= 1, W=0, FCN=1 ----->|
|-----DTag= 1, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 1, W=1, FCN=6 ----->|
|-----DTag= 1, W=1, FCN=5 ----->|
|-----DTag= 1, W=1, FCN=4 ----->|
|-----DTag= 1, W=1, FCN=3 ----->|
|-----DTag= 1, W=1, FCN=2 ----->|
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|-----DTag= 1, W=1, FCN=1 --X |
|-----DTag= 1, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 1, W=2, FCN=6 ----->|
|-----DTag= 1, W=2, FCN=5 --X |
|-----DTag= 1, W=2, FCN=4 ----->|
|-----DTag= 1, W=2, FCN=3 ----->|
|-----DTag= 1, W=2, FCN=2 ----->|
|-----DTag= 1, W=2, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 1, W=3, FCN=6 ----->|
|--DTag= 1, W=3, FCN=7, RCS --->| All-1, Bitmap: 1011111
|<--- DTag= 0, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 0, W=0, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=5 ----->|
|<--- DTag= 1, Compound ACK ----| [C=0, W=0 - Bitmap:1111011, W=1 - Bitmap:1111101, W=2 - Bitmap:1011111]
|-----DTag= 1, W=0, FCN=2 ----->|
|-----DTag= 1, W=1, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=5 ----->|
|<--- DTag= 1, ACK, W=3, C=1 ---| C=1
Figure 4: SCHC Streaming mode sequence example 3 - Closed by sender
Figure 5 shows a SCHC Streaming example where the receiver aborts
current transmission.
Sender Receiver
|-----DTag= 0, W=0, FCN=6 ----->|
|-----DTag= 0, W=0, FCN=5 ----->|
|-----DTag= 0, W=0, FCN=4 ----->|
|-----DTag= 0, W=0, FCN=3 ----->|
|-----DTag= 0, W=0, FCN=2 --X |
|-----DTag= 0, W=0, FCN=1 ----->|
|-----DTag= 0, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 0, W=1, FCN=6 ----->|
|-----DTag= 0, W=1, FCN=5 ----->|
|-----DTag= 0, W=1, FCN=4 ----->|
|-----DTag= 0, W=1, FCN=3 ----->|
|-----DTag= 0, W=1, FCN=2 ----->|
|-----DTag= 0, W=1, FCN=1 --X |
|-----DTag= 0, W=1, FCN=0 ----->| Bitmap: 1111101
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(no ACK)
|-----DTag= 0, W=2, FCN=6 ----->|
|-----DTag= 0, W=2, FCN=5 --X |
|-----DTag= 0, W=2, FCN=4 ----->|
|-----DTag= 0, W=2, FCN=3 ----->|
|-----DTag= 0, W=2, FCN=2 ----->|
|-----DTag= 0, W=2, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|-----DTag= 0, W=3, FCN=6 ----->|
|-----DTag= 0, W=3, FCN=5 ----->|
|-----DTag= 0, W=3, FCN=4 ----->|
|-----DTag= 0, W=3, FCN=3 ----->|
|-----DTag= 0, W=3, FCN=2 ----->|
|-----DTag= 0, W=3, FCN=1 ----->|
|-----DTag= 0, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
(next Window Cycle)
|-----DTag= 1, W=0, FCN=6 ----->|
|-----DTag= 1, W=0, FCN=5 ----->|
|-----DTag= 1, W=0, FCN=4 ----->|
|-----DTag= 1, W=0, FCN=3 ----->|
|-----DTag= 1, W=0, FCN=2 --X |
|-----DTag= 1, W=0, FCN=1 ----->|
|-----DTag= 1, W=0, FCN=0 ----->| Bitmap: 1111011
(no ACK)
|-----DTag= 1, W=1, FCN=6 ----->|
|-----DTag= 1, W=1, FCN=5 ----->|
|-----DTag= 1, W=1, FCN=4 ----->|
|-----DTag= 1, W=1, FCN=3 ----->|
|-----DTag= 1, W=1, FCN=2 ----->|
|-----DTag= 1, W=1, FCN=1 --X |
|-----DTag= 1, W=1, FCN=0 ----->| Bitmap: 1111101
(no ACK)
|-----DTag= 1, W=2, FCN=6 ----->|
|-----DTag= 1, W=2, FCN=5 --X |
|-----DTag= 1, W=2, FCN=4 ----->|
|-----DTag= 1, W=2, FCN=3 ----->|
|-----DTag= 1, W=2, FCN=2 ----->|
|-----DTag= 1, W=2, FCN=1 ----->|
|-----DTag= 1, W=2, FCN=0 ----->| Bitmap: 1011111
(no ACK)
|<--------- RECV ABORT ---------|
Figure 5: SCHC Streaming mode sequence example 4 - Aborted by
receiver
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5. SCHC Streaming mode YANG Data Model
The present document also extends the SCHC YANG data model defined in
[RFC9363] by including a new identity in the fragmentation mode type.
5.1. SCHC YANG Data Model Extension
TBD
5.2. SCHC YANG Tree Extension
TBD
6. Security considerations
TBD
7. IANA Considerations
This document has no IANA actions.
8. Acknowledgements
Carles Gomez has been funded in part by the Spanish Government
through the TEC2016-79988-P grant, and the PID2019-106808RA-I00 grant
(funded by MCIN / AEI / 10.13039/501100011033), and by Secretaria
d'Universitats i Recerca del Departament d'Empresa i Coneixement de
la Generalitat de Catalunya 2017 through grant SGR 376.
Sergio Aguilar has been funded by the ERDF and the Spanish Government
through project TEC2016-79988-P and project PID2019-106808RA-I00,
AEI/FEDER, EU (funded by MCIN / AEI / 10.13039/501100011033).
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
Zuniga, "SCHC: Generic Framework for Static Context Header
Compression and Fragmentation", RFC 8724,
DOI 10.17487/RFC8724, April 2020,
<https://www.rfc-editor.org/info/rfc8724>.
[RFC9363] Minaburo, A. and L. Toutain, "A YANG Data Model for Static
Context Header Compression (SCHC)", RFC 9363,
DOI 10.17487/RFC9363, March 2023,
<https://www.rfc-editor.org/info/rfc9363>.
9.2. Informative References
[RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN)
Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018,
<https://www.rfc-editor.org/info/rfc8376>.
Authors' Addresses
Sergio Aguilar
Universitat Politecnica de Catalunya
C/Esteve Terradas, 7
08860 Castelldefels
Spain
Email: sergio.aguilar.romero@upc.edu
Carles Gomez
Universitat Politecnica de Catalunya
C/Esteve Terradas, 7
08860 Castelldefels
Spain
Email: carles.gomez@upc.edu
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