Internet DRAFT - draft-xie-tcpm-mptcp-feedback
draft-xie-tcpm-mptcp-feedback
TCP Maintenance and Minor Extensions (tcpm) B. Zhao
Internet-Draft W. Yang
Intended status: Standards Track W. Du
Expires: 18 April 2024 Y. Ren
X. Zhou
G. Xie
CNIC
16 October 2023
A Message Feedback Method for MPTCP
draft-xie-tcpm-mptcp-feedback-00
Abstract
Mobile phone devices are usually configured with multiple wireless
access network cards, such as LTE/5G, Wi-Fi. And the wireless
network is a network with highly time-varying bandwidth. For a
single wireless device, the limited bandwidth cannot meet the peak
rate requirements of low-latency applications. MPTCP supports the
simultaneous use of multiple networks on mobile devices. Due to the
time-varying nature of wireless networks, it is challenging for MPTCP
to accurately schedule data blocks to different sub-streams to meet
their low-latency requirements. This document proposes a new cross-
layer feedback method for wireless networks to pass the scheduling
information and status of the wireless network to the MPTCP Server.
MPTCP Server can predict the transmission capacity of the wireless
network based on this cross-layer information, thereby improving the
efficiency of data block scheduling on multipaths.
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 18 April 2024.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 3
4. Non-3GPP Device Information . . . . . . . . . . . . . . . . . 4
5. 3GPP Device Information . . . . . . . . . . . . . . . . . . . 4
6. MP_INFO Usage . . . . . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Historical Note . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
With the popularity of mobile devices, most devices have multiple
wireless access methods, such as 5G, and Wi-Fi. This has brought a
realistic basis for the popularity of MPTCP. However, the current
MPTCP can only perceive information such as RTT, but cannot perceive
information from edge wireless devices. Therefore, a new subtype of
MPTCP options is proposed in this document to transmit cross-layer
information of wireless devices [RFC8684]. Figure 1 illustrates the
integration of the MP_INFO into the wireless devices, where the MPTCP
client resides on the UE and the MPTCP server resides on the Server.
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+---------+ +---------+ +--------+ +----------+
| | | NR | GTP-U | | MP_INFO | |
| |----+---------|---------| UPF |----------| |
| UE | | 3GPP | | | | Server |
|---------| +---------+ +--------+ |--------- |
| MPTCP | +---------+ | MPTCP |
| | | | MP_INFO | |
| |----|Non-3GPP |-----------------------------| |
| | | | | |
+---------+ +---------+ +----------+
Figure 1: A network architecture for MPTCP
2. Terminology
NR: New Radio, a new wireless access technology for 5G.
GTP-U Message: GTP-U (user plane) messages are either user plane
messages or signalling messages. User plane messages are used to
carry user data packets between GTP-U entities. Signalling
messages are sent between network nodes for path management and
tunnel management.GTP-U peer: node implementing at least one side
of any of the GTP user plane based protocols.
UPF: User Plane Function.
CQI: CQI reflects the time-changing link capability.
3. Design Overview
In mobile networks, the performance of wireless devices has a great
impact on data transmission. Therefore, by feeding back the
information of the wireless device to the MPTCP server, it is
convenient for the MPTCP scheduler to schedule traffic to different
paths according to the information of the edge device. For the non-
3GPP path, the Wi-Fi AP can directly modify the MPTCP data packet to
feed back the device information to the MPTCP server. For the 3GPP
path, 5G NR periodically feeds back equipment information to UPF
through the GTP-U protocol [GTP-U]. UPF can directly modify the
MPTCP data packet to feed back the device information to the MPTCP
server. This document defines the extension of the MPTCP subtype,
which allows the MPTCP server schedules traffic to different paths
according to the information of edge devices. In addition, this
document provides a cross-layer information transfer method for 3GPP
and non-3GPP equipment [_5G-MPTCP]. Section 4 will introduce the
transmission method of non-3GPP devices. In Section 5, the
transmission method of 3GPP equipment will be introduced. Section 6
will introduce the usage of MP_INFO.
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4. Non-3GPP Device Information
The MPTCP server needs to obtain information on non-3GPP devices,
such as Wi-Fi AP. This document defines a new MPTCP Option subtype
MP_INFO. Non-3GPP devices can transform devices information from
wireless devices to the MPTCP server. The format of MP_INFO is shown
in Figure 2. It has the following fields:
Device Type: The type of device, 0x1 represents the non-3GPP path.
Rate: The send Rate of non-3GPP devices.
Buffer Length: The buffer length of a non-3GPP device.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Kind | Length |Subtype|Device.| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Buffer Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MP_INFO Structure for Non-3GPP Device
5. 3GPP Device Information
For the 3GPP path, we need to overcome the difficulty of acquiring 5G
NR information. In the 3GPP path, the GTP-U tunnel is responsible
for transmitting data between the radio access network and the
UPF[gNB]. So as shown in Figure 3, for the 3GPP path, 5G NR
transmits equipment information to UPF through GTP-U [GTP-U]. Then,
UPF transmits the calculated rate and Buffer to the MPTCP server
through MP_INFO. In the 3GPP path, the GTP-U tunnel is responsible
for transmitting data between the radio access network and the
UPF[gNB]. 5G NR uses the GTP-U tunnel to periodically send status
information to the UPF, e.g. 1 ms. 5G NR only transmits the key
information that affects the latency. Note that this information is
only transmitted between 5G NR and UPF.
+---------+ +---------+ +---------+ +---------+
| UE | | NR | GTP-U | UPF | MP_INFO | Server |
+---------+----+---------|----------|---------|-----------|---------|
| MPTCP | | | | | | MPTCP |
+---------+ +---------+ +---------+ +---------+
Figure 3: Communication process between NR and UPF
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The format of MP_INFO for 3GPP devices is shown in Figure 4. It has
the following fields:
Device Type: The type of device, 0x2 represents the 3GPP path.
Rate: The send rate of the 3GPP device, can be calculated by CQI.
RLC Buffer: The sum of RLC buffer length, can be feedback through NR
[RLC].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Kind | Length |Subtype|Device.| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RLC Buffer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: MP_INFO Structure for 3GPP Device
6. MP_INFO Usage
MPTCP scheduler can leverage cross-layer information from 5G NR and
Wi-Fi AP to predict the transmission delay of data blocks on each
path. However, there is a visual gap between this cross-layer
information and the MPTCP server, which requires different methods on
different paths to transmit cross-layer path information to the MPTCP
server. So this document separately introduces the cross-layer
information collection for non-3GPP and 3GPP paths. For 3GPP paths,
we recommend feeding back the MP-INFO option every 10ms. Because
3GPP equipment generally uses fixed time slot allocation, the time of
one frame is 10ms. Non-3GPP devices do not have fixed time slots, so
the feedback time can be flexible.
And network operator can design their prediction delay methods
according to the cross-layer information. By leveraging cross-layer
information from edge wireless, the MPTCP server can predict downlink
latency and optimize multipath scheduling. For example, By CQI and
RLC Buffer information, the MPTCP server can predict the delay of the
3GPP path. By Rate and Buffer Length information, UPF can predict
the delay of the non-3GPP path. According to the predicted
transmission delay, the MPTCP scheduler can use different strategies
to schedule packets.
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MP-INFO option is an incremental information. In multipath, some
paths may do not support this option. For this case, the MPTCP
scheduler can fall back to the MinRTT scheduler.
7. IANA Considerations
This draft adds the following subtype numbers to the MPTCP Option
Subtypess registry of [RFC8684]:
+=======+=========+=========================+===========+
| Value | Symbol | Name | Reference |
+=======+=========+=========================+===========+
| 0x9 | MP_INFO | Cross layer information | [RFC8684] |
| | | of non-3GPP devices | |
+-------+---------+-------------------------+-----------+
Table 1: MPTCP Option Subtypes
+===================+===============+
| Device Type Value | Message |
+===================+===============+
| 0x1 | Non-3GPP Path |
+-------------------+---------------+
| 0x2 | 3GPP Path |
+-------------------+---------------+
Table 2: Device Type in MP_INFO
8. Security Considerations
Since the MP_INFO option requires intermediate devices to modify data
packets, some devices may not support this option.
Some wireless devices may send incorrect MP-INFO information, so the
terminal should confirm the security of the path.
9. References
9.1. Normative References
[RFC8684] Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
Paasch, "TCP Extensions for Multipath Operation with
Multiple Addresses", RFC 8684, DOI 10.17487/RFC8684, March
2020, <https://www.rfc-editor.org/info/rfc8684>.
9.2. Informative References
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[gNB] 3GPP TS 38.300 (2023-06), "NR and NG-RAN Overall
description (Release 15)", n.d..
[GTP-U] 3GPP TS 29.281 V18.0.0 (2023-06), "General Packet Radio
System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)
(Release 18)", n.d..
[RLC] 3GPP TS 38.322 (2023-06), "Radio Link Control (RLC)
protocol specification (Release 15)", n.d..
[_5G-MPTCP]
3GPP, "System architecture for the 5G System (5GS) Release
17", 2022.
Appendix A. Historical Note
Authors' Addresses
Baosen Zhao
CNIC
Beijing
100083
China
Email: zhaobaosen@cnic.cn
Wanghong Yang
CNIC
Beijing
100083
China
Email: yangwanghong@cnic.cn
Wenji Du
CNIC
Beijing
100083
China
Email: hjdu@cnic.cn
Yongmao Ren
CNIC
Beijing
100083
China
Email: renyongmao@cstnet.cn
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Xu Zhou
CNIC
Beijing
100083
China
Email: zhouxu@cstnet.cn
Gaogang Xie
CNIC
Beijing
100083
China
Email: xie@cnic.cn
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