Internet-Draft | Accurate Data Scheduling by Server | July 2020 |
Kang & Liang | Expires 14 January 2021 | [Page] |
- Workgroup:
- TCP Maintenance and Minor Extensions
- Internet-Draft:
- draft-kang-tcpm-accurate-data-scheduling-by-server-00
- Published:
- Intended Status:
- Informational
- Expires:
Accurate Data Scheduling by Server in MPTCP
Abstract
This document defines a new mechanism that enables server to send request to client for data scheduling between the subflows during a MPTCP session.¶
Status of This Memo
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This Internet-Draft will expire on 14 January 2021.¶
Copyright Notice
Copyright (c) 2020 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/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶
1. Introduction
MPTCP protocol is now being deployed in more and more networks. In most scenarios, MPTCP scheduling strategies for these subflows are implemented on client side considering RTT and congestion, or sending packets redundantly. Application server cannot actively participate in such decision-making.¶
However in real deployment, application server supports multiple network interfaces from different operators when MPTCP protocol is adopted. There are such scenarios that the server wants to set scheduling to the client on these network interfaces based on server-side rules in a MPTCP session. The requirements for these use cases are listed below:¶
- Network fault prevention. Server tools can detect network quality of deployed network interfaces such as packet Loss, delay and jitter. When the key performance indicators (KPI) become worse, the server hope to switch the traffic to a network interface with better KPI.¶
- Broadband entrances from different operators or the emergency entrance of 5G card are added. This change is dynamic throughout the session and the operator hope to reduce the load on some subflows and lead them to the additional subflow, such as for test. This is the trial operation scenario for new network.¶
- Value-added services. Operator wants to provide customers with diversified services to satisfy individual demand. For example, for VIP users, it should be possible to switch their traffic to network interface with better network KPIs.¶
- Another typical scenario is that operator hope to adjust traffic to a specific subflow for the changes in network cost, for example, the expiration of discounts.¶
There are two related implementations. RFC8684 defines REMOVE_ADDR Option to delete one address during a MPTCP session and it also closes all subflows bound to this address. draft-hoang-mptcp-sub-rate-limit-00 proposes a Subflow Rate Limit Option which can be used by sender to receiver for setting the rate of one subflow to zero. But for the use cases in this document, existing technologies are somewhat inadequate because they do not provide a clear indication of which subflow to switch to.¶
2. Typical flows for accurate data scheduling by server
This document proposes an accurate data scheduling mechanism for server. Two typical flows are illustrated in Figure 1 and Figure 2.¶
For the use case of adding a new network interface to MPTCP session for navigation, normal process of ADD_ADDR should be executed before traffic switching.¶
If it is determined to cancel the data switching on the subflow, the client should delete the navigation information. The navigation information is generated by the client and is used to determine the target subflow for data switching based on the address ID of the target network interface.¶
After data switching, if the subflow with diverted traffic is disconnected, the client should delete the navigation information and configuration information for it. The navigation information is generated by the client and is used to determine the target subflow for data switching based on the address ID of the target network interface.¶
3. Examples
3.1. Traffic switching to a newly-added network interface
Four subflows have been established between client and server that are <IP1, IP3>, <IP2, IP3>, <IP1, IP4> and <IP2, IP4>. On the client, IP1 and IP2 are the address IDs for WiFi and a cellular network. On the server, IP3 and IP4 are the address IDs for Ethernet and WiFi. When a new 5G network is deployed on the server, the server can switch the data traffic on the subflow <IP2,IP4> to the destination IP5 corresponding to 5G. In this case, the target network interface is IP5.¶
3.2. Traffic switching to a network interface already in the session
Four subflows have been established between client and server that are <IP1, IP3>, <IP2, IP3>, <IP1, IP4> and <IP2, IP4>. On the client, IP1 and IP2 are the address IDs for WiFi and a cellular network. On the server, IP3 and IP4 are the address IDs for Ethernet and WiFi. Server tool detects that KPI for IP4 is better now so the server can switch data traffic on the subflow <IP1, IP3> to the destination IP4.¶
4. MP_Navigation Option
In this solution, a MP_Navigation option is defined and sent from server to forces client to switch traffic from the subflow over which the option was received to a target subflow or to cancel the traffic switching when it is not required, which is indicated by a flag 'R'. If it is set, the target subflow is determined through the Address ID of the target network interface in MP_Navigation option.¶
This MP_Navigation Option can be sent in ACK.¶
It is noted that if this option is not supported by the client, it should be omitted.¶
4.1. Option Format
The format of the MP_Navigation option is depicted in Figure 3:¶
Subtype: A new subtype should be allocated to indicate MP_Navigation Option.¶
Address ID: Address ID in MP_Navigation Option is used to identify the address ID of target network Interface.¶
The flag 'R', when set, define the content of this option, as follows:¶
- When value of 'R' is set to zero, server want to use this option to inform client of navigation policy and the client will perform traffic switching as requested by the server. When value of 'R' is set to 1, the server requests to cancel current navigation policy in client and the client will delete corresponding navigation information to the Address ID.¶
When the client receives the MP_Navigation Option, it will determine the target network interface by the Address ID. Address ID may map to one or more ongoing subflows and the client will select one for each data transfer by its local strategies.¶
5. IANA Considerations
IANA is requested to assign a MPTCP option subtype for the MP_Navigation option.¶
6. Security Considerations
Since MP_Navigation Option is neither encrypted nor authenticated, on-path attackers and middleboxes could remove, add or modify the MP_Navigation Option on observed Multipath TCP connections.¶
7. References
7.1. Normative References
- [RFC0793]
- Postel, J., "Transmission Control Protocol", STD 7, RFC 793, DOI 10.17487/RFC0793, , <https://www.rfc-editor.org/info/rfc793>.
- [RFC6824]
- Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, DOI 10.17487/RFC6824, , <https://www.rfc-editor.org/info/rfc6824>.
- [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, , <https://www.rfc-editor.org/info/rfc8684>.