| Network Working Group | M. Boucadair |
| Internet-Draft | C. Jacquenet |
| Intended status: Experimental | France Telecom |
| Expires: December 18, 2015 | June 16, 2015 |
Negotiating the Maximum Number of MPTCP Subflows
draft-boucadair-mptcp-extensions-00
This document specifies an experimental MPTCP option that is meant to negotiate the maximum number of subflows that can be established and maintained for a given MPTCP connection. The purpose is to minimize any possible performance degradation that can be induced by a possibly large number of establishment requests for additional subflows if the remote endpoint is not appropriateley dimensioned to handle such requests.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 18, 2015.
Copyright (c) 2015 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 (http://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.
This document specifies a MPTCP option that is meant to indicate to a remote peer the maximum number of subflows that can be established within a single MPTCP connection. If the remote peer honors the indication provided in this option, any performance degradation induced by a possibly abusive setup of additional subflows that exceed the said maximum becomes unlikely.
This document adheres to [I-D.bonaventure-mptcp-exp-option].
This option targets mainly MPTCP deployments within a single administrative domain such as those MPTCP designs meant to achieve load-balancing, for example. The use of this option contributes to the harmonization of node configuration within an administrative domain, so that an optimal number of subflows is maintained by involved nodes independently of their actual performance capabilities. This option can be used for other deployment scenarios. It is out of scope of this document to identify an exhaustive list of such scenarios.
Experiments based upon the MPTCP option described in this document are meant to help operators refine their MPTCP design and operational procedures, by tweaking some MPTCP parameters such as the number of subflows to be associated with a given MPTCP connection. Experimenting with this MPTCP option should also help assess whether this option can be used to propagate MPTCP-related optimization parameters (derived from the number of concurrent subflows associated to each MPTCP connection) that can be configured in a node that is responsible for aggregating MPTCP connections established with upstream nodes.
This option follows the shared experimental format defined in [I-D.bonaventure-mptcp-exp-option] (see Figure 1).
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| Flags | Experiment |
+---------------+---------------+-------+-------+---------------+
| Id. (16 bits) | Maximum Sub-Flows |
+---------------+-----------------------------------------------+
Figure 1: Option Format
[I-D.bonaventure-mptcp-exp-option].
Experiment ID (to be assigned, see Section 5).
The "Maximum Sub-Flows" field indicates the number of maximum concurrent subflows that can be maintained by a given MPTCP endpoint for each MPTCP connection established by or with this endpoint. The value of this field MUST be strictly greater than zero.
The option defined in Section 2 is used by a TCP endpoint to indicate to its corresponding peer the maximum number of subflows that it can maintain per MPTCP connection.
If two peers (T1 and T2) indicate the maximum number of concurrent subflows per connection they can maintain, then they MUST NOT maintain more than "MIN(MAX_SUBFLOW(T1), MAX_SUBFLOW(T2))" concurrent subflows.
The absence of this option in an MPTCP control message issued by a MPTCP endpoint is an indication that this endpoint can instantiate any number of subflows per MPTCP connection.
If no maximum number of subflows is configured locally to an MPTCP endpoint, it may rely on the results of procedures such as [I-D.boucadair-mptcp-connectivity-checks] as a hint to determine the value to include in the "Maximum Sub-Flows" MPTCP option.
MPTCP-related security considerations are documented in [RFC6824] and [I-D.ietf-mptcp-attacks].
This document requests IANA to assign an experiment ID as per [I-D.bonaventure-mptcp-exp-option].
TBC
| [I-D.bonaventure-mptcp-exp-option] | Bonaventure , O., Hesmans, B. and M. Boucadair, "Experimental Multipath TCP option", 1992. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC6824] | Ford, A., Raiciu, C., Handley, M. and O. Bonaventure, "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, January 2013. |
| [I-D.boucadair-mptcp-connectivity-checks] | Boucadair, M. and C. Jacquenet, "MPTCP Connectivity Checks", Internet-Draft draft-boucadair-mptcp-connectivity-checks-00, March 2015. |
| [I-D.ietf-mptcp-attacks] | Bagnulo, M., Paasch, C., Gont, F., Bonaventure, O. and C. Raiciu, "Analysis of MPTCP residual threats and possible fixes", Internet-Draft draft-ietf-mptcp-attacks-04, March 2015. |