Network Working Group M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Standards Track France Telecom
Expires: May 20, 2016 T. Reddy
Cisco
November 17, 2015
DHCP Options for Network-Assisted Multipath TCP (MPTCP)
draft-boucadair-mptcp-dhc-04
Abstract
One of the promising deployment scenarios for Multipath TCP (MPTCP)
is to enable a Customer Premises Equipment (CPE) that is connected to
multiple networks (e.g., DSL, LTE, WLAN) to optimize the usage of its
network attachments. Because of the lack of MPTCP support at the
server side, some service providers consider a network-assisted model
that relies upon the activation of a dedicated function called: MPTCP
Concentrator.
This document focuses on the explicit deployment scheme where the
identity of the MPTCP Concentrator(s) is explicitly configured on
connected hosts. This document specifies DHCP (IPv4 and IPv6)
options to configure hosts with Multipath TCP (MPTCP) parameters.
Requirements Language
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].
Status of This Memo
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
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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 May 20, 2016.
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Copyright Notice
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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DHCPv6 MPTCP Option . . . . . . . . . . . . . . . . . . . . . 4
3.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 5
4. DHCPv4 MPTCP Option . . . . . . . . . . . . . . . . . . . . . 5
4.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. DHCPv4 Client Behavior . . . . . . . . . . . . . . . . . 7
5. DHCP Server Configuration Guidelines . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 9
8.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
One of the promising deployment scenarios for Multipath TCP (MPTCP,
[RFC6824]) is to enable a Customer Premises Equipment (CPE) that is
connected to multiple networks (e.g., DSL, LTE, WLAN) to optimize the
usage of such resources, see for example [RFC4908]. This deployment
scenario relies on MPTCP proxies located on both the CPE and network
sides (Figure 1). The latter plays the role of traffic concentrator.
A concentrator terminates the MPTCP sessions established from a CPE,
before redirecting traffic into a legacy TCP session.
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IP Network #1
+------------+ _--------_ +------------+
| | (e.g., LTE ) | |
| CPE +======================+ |
| (MPTCP | (_ _) |Concentrator|
| Proxy) | (_______) | (MPTCP |
| | | Proxy) |------> Internet
| | | |
| | IP Network #2 | |
| | _--------_ | |
| | ( e.g., DSL ) | |
| +======================+ |
| | (_ _) | |
+-----+------+ (_______) +------------+
|
----CPE network----
|
end-nodes
Figure 1: "Network-Assisted" MPTCP Design
Both implicit and explicit modes are considered to steer traffic
towards an MPTCP Concentrator. This document focuses on the explicit
mode that consists in configuring explicitly the reachability
information of the MPTCP concentrator on a host.
This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options
that can be used to configure hosts with MPTCP Concentrator IP
addresses.
This specification assumes an MPTCP Concentrator is reachable through
one or multiple IP addresses. As such, a list of IP addresses can be
returned in the DHCP MPTCP option. Also, it assumes the various
network attachments provided to an MPTCP-enabled CPE are managed by
the same administrative entity.
2. Terminology
This document makes use of the following terms:
o MPTCP Concentrator (or concentrator): refers to a functional
element that is responsible for aggregating the traffic of a group
of CPEs. This element is located upstream in the network. One or
multiple concentrators can be deployed in the network side to
assist MPTCP-enabled CPEs to establish MPTCP connections via
available network attachments.
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On the uplink path, the concentrator terminates the MPTCP
connections [RFC6824] received from its customer-facing interfaces
and transforms these connections into legacy TCP connections
[RFC0793] towards upstream servers.
On the downlink path, the concentrator turns the legacy server's
TCP connection into MPTCP connections towards its customer-facing
interfaces.
o DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC3315].
o DHCP client denotes a node that initiates requests to obtain
configuration parameters from one or more DHCP servers.
o DHCP server refers to a node that responds to requests from DHCP
clients.
3. DHCPv6 MPTCP Option
3.1. Format
The DHCPv6 MPTCP option can be used to configure a list of IPv6
addresses of an MPTCP Concentrator.
The format of this option is shown in Figure 2. As a reminder, this
format follows the guidelines for creating new DHCPv6 options
(Section 5.1 of [RFC7227]).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V6_MPTCP | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ipv6-address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ipv6-address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DHCPv6 MPTCP option
The fields of the option shown in Figure 2 are as follows:
o Option-code: OPTION_V6_MPTCP (TBA, see Section 8.1)
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o Option-length: Length of the 'MPTCP Concentrator IP Address(es)'
field in octets. MUST be a multiple of 16.
o MPTCP Concentrator IPv6 Addresses: Includes one or more IPv6
addresses [RFC4291] of the MPTCP Concentrator to be used by the
MPTCP client.
Note, IPv4-mapped IPv6 addresses (Section 2.5.5.2 of [RFC4291])
are allowed to be included in this option.
To return more than one MPTCP concentrators to the requesting DHCPv6
client, the DHCPv6 server returns multiple instances of
OPTION_V6_MPTCP.
3.2. DHCPv6 Client Behavior
Clients MAY request option OPTION_V6_MPTCP, as defined in [RFC3315],
Sections 17.1.1, 18.1.1, 18.1.3, 18.1.4, 18.1.5, and 22.7. As a
convenience to the reader, we mention here that the client includes
requested option codes in the Option Request Option.
The DHCPv6 client MUST be prepared to receive multiple instances of
OPTION_V6_MPTCP; each instance is to be treated separately as it
corresponds to a given MPTCP Concentrator: there are as many
concentrators as instances of the OPTION_V6_MPTCP option.
If an IPv4-mapped IPv6 address is received in OPTION_V6_MPTCP, it
indicates that the MPTCP Concentrator has the corresponding IPv4
address.
The DHCPv6 client MUST silently discard multicast and host loopback
addresses [RFC6890] conveyed in OPTION_V6_MPTCP.
4. DHCPv4 MPTCP Option
4.1. Format
The DHCPv4 MPTCP option can be used to configure a list of IPv4
addresses of an MPTCP Concentrator. The format of this option is
illustrated in Figure 3.
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| List-Length | List of |
+-+-+-+-+-+-+-+-+ MPTCP |
/ Concentrator IPv4 Addresses /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| List-Length | List of | |
+-+-+-+-+-+-+-+-+ MPTCP | |
/ Concentrator IPv4 Addresses / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. ... . optional
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| List-Length | List of | |
+-+-+-+-+-+-+-+-+ MPTCP | |
/ Concentrator IPv4 Addresses / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
Figure 3: DHCPv4 MPTCP option
The fields of the option shown in Figure 3 are as follows:
o Code: OPTION_V4_MPTCP (TBA, see Section 8.2);
o Length: Length of all included data in octets. The minimum length
is 5.
o List-Length: Length of the "List of MPTCP Concentrator IPv4
Addresses" field in octets; MUST be a multiple of 4.
o List of MPTCP Concentrator IPv4 Addresses: Contains one or more
IPv4 addresses of the MPTCP Concentrator to be used by the MPTCP
client. The format of this field is shown in Figure 4.
o OPTION_V4_MPTCP can include multiple lists of MPTCP Concentrator
IPv4 addresses; each list is treated separately as it corresponds
to a given MPTCP Concentrator.
When several lists of MPTCP Concentrator IPv4 addresses are to be
included, "List-Length" and "MPTCP Concentrator IPv4 Addresses"
fields are repeated.
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0 8 16 24 32 40 48
+-----+-----+-----+-----+-----+-----+--
| a1 | a2 | a3 | a4 | a1 | a2 | ...
+-----+-----+-----+-----+-----+-----+--
IPv4 Address 1 IPv4 Address 2 ...
This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.
Figure 4: Format of the List of MPTCP Concentrator IPv4 Addresses
OPTION_V4_MPTCP is a concatenation-requiring option. As such, the
mechanism specified in [RFC3396] MUST be used if OPTION_V4_MPTCP
exceeds the maximum DHCPv4 option size of 255 octets.
4.2. DHCPv4 Client Behavior
To discover one or more MPTCP Concentrators, the DHCPv4 client MUST
include OPTION_V4_MPTCP in a Parameter Request List Option [RFC2132].
The DHCPv4 client MUST be prepared to receive multiple lists of MPTCP
Concentrator IPv4 addresses in the same OPTION_V4_MPTCP; each list is
to be treated as a separate MPTCP Concentrator instance.
The DHCPv4 client MUST silently discard multicast and host loopback
addresses [RFC6890] conveyed in OPTION_V4_MPTCP.
5. DHCP Server Configuration Guidelines
DHCP servers that support the DHCP MPTCP Concentrator option can be
configured with a list of IP addresses of the MPTCP Concentrator(s).
If multiple IP addresses are configured, the DHCP server MUST be
explicitly configured whether all or some of these addresses refer
to:
1. the same MPTCP Concentrator: the DHCP server returns multiple
addresses in the same instance of the DHCP MPTCP Concentrator
option.
2. distinct MPTCP Concentrators : the DHCP server returns multiple
lists of MPTCP Concentrator IP addresses to the requesting DHCP
client (encoded as multiple OPTION_V6_MPTCP or in the same
OPTION_V4_MPTCP); each list refers to a distinct MPTCP
Concentrator.
Precisely how DHCP servers are configured to separate lists of IP
addresses according to which MPTCP Concentrator they refer to is out
of scope for this document. However, DHCP servers MUST NOT combine
the IP addresses of multiple MPTCP Concentrators and return them to
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the DHCP client as if they were belonging to a single MPTCP
Concentrator, and DHCP servers MUST NOT separate the addresses of a
single MPTCP Concentrator and return them as if they were belonging
to distinct MPTCP Concentrators. For example, if an administrator
configures the DHCP server by providing a Fully Qualified Domain Name
(FQDN) for a MPTCP Concentrator, even if that FQDN resolves to
multiple addresses, the DHCP server MUST deliver them within a single
server address block.
DHCPv6 servers that implement this option and that can populate the
option by resolving FQDNs will need a mechanism for indicating
whether to query A records or only AAAA records. When a query
returns A records, the IP addresses in those records are returned in
the DHCPv6 response as IPv4-mapped IPv6 addresses.
Since this option requires support for IPv4-mapped IPv6 addresses, a
DHCPv6 server implementation will not be complete if it does not
query A records and represent any that are returned as IPv4-mapped
IPv6 addresses in DHCPv6 responses. The mechanism whereby DHCPv6
implementations provide this functionality is beyond the scope of
this document.
For guidelines on providing context-specific configuration
information (e.g., returning a regional-based configuration), and
information on how a DHCP server might be configured with FQDNs that
get resolved on demand, see [I-D.ietf-dhc-topo-conf].
6. Security Considerations
The security considerations in [RFC2131] and [RFC3315] are to be
considered.
MPTCP-related security considerations are discussed in [RFC6824].
Means to protect the MPTCP concentrator against Denial-of-Service
(DoS) attacks must be enabled. Such means include the enforcement of
ingress filtering policies at the boundaries of the network. In
order to prevent exhausting the resources of the concentrator by
creating an aggressive number of simultaneous subflows for each MPTCP
connection, the administrator should limit the number of allowed
subflows per host for a given connection.
Attacks outside the domain can be prevented if ingress filtering is
enforced. Nevertheless, attacks from within the network between a
host and a concentrator instance are yet another actual threat.
Means to ensure that illegitimate nodes cannot connect to a network
should be implemented.
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Traffic theft is also a risk if an illegitimate concentrator is
inserted in the path. Indeed, inserting an illegitimate concentrator
in the forwarding path allows to intercept traffic and can therefore
provide access to sensitive data issued by or destined to a host. To
mitigate this threat, secure means to discover a concentrator (for
non-transparent modes) should be enabled.
7. Privacy Considerations
Generic privacy-related considerations are discussed in
[I-D.ietf-dhc-anonymity-profile].
The concentrator may have access to privacy-related information
(e.g., International Mobile Subscriber Identity (IMSI), link
identifier, subscriber credentials, etc.). The concentrator must not
leak such sensitive information outside an administrative domain.
8. IANA Considerations
8.1. DHCPv6 Option
IANA is requested to assign the following new DHCPv6 Option Code in
the registry maintained in http://www.iana.org/assignments/
dhcpv6-parameters:
Option Name Value
--------------- -----
OPTION_V6_MPTCP TBA
8.2. DHCPv4 Option
IANA is requested to assign the following new DHCPv4 Option Code in
the registry maintained in http://www.iana.org/assignments/bootp-
dhcp-parameters/:
Option Name Value Data length Meaning
--------------- ----- ----------- -----------------------------------
OPTION_V4_MPTCP TBA Variable; Includes one or multiple lists of
the minimum MPTCP Concentrator IP addresses;
length is each list is treated as a separate
5. MPTCP Concentrator.
9. Acknowledgements
Many thanks to Olivier Bonaventure for the feedback on this document.
Olivier suggested to define the option as a name but that design
approach was debated several times within the dhc wg.
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Thanks to Dan Seibel, Bernie Volz, Niall O'Reilly, Simon Hobson, and
Ted Lemon for the feedback on the dhc wg mailing list.
10. References
10.1. 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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<http://www.rfc-editor.org/info/rfc2131>.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
<http://www.rfc-editor.org/info/rfc2132>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
DOI 10.17487/RFC3396, November 2002,
<http://www.rfc-editor.org/info/rfc3396>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<http://www.rfc-editor.org/info/rfc6824>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<http://www.rfc-editor.org/info/rfc6890>.
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10.2. Informative References
[I-D.ietf-dhc-anonymity-profile]
Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
profile for DHCP clients", draft-ietf-dhc-anonymity-
profile-04 (work in progress), October 2015.
[I-D.ietf-dhc-topo-conf]
Lemon, T. and T. Mrugalski, "Customizing DHCP
Configuration on the Basis of Network Topology", draft-
ietf-dhc-topo-conf-06 (work in progress), October 2015.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC4908] Nagami, K., Uda, S., Ogashiwa, N., Esaki, H., Wakikawa,
R., and H. Ohnishi, "Multi-homing for small scale fixed
network Using Mobile IP and NEMO", RFC 4908,
DOI 10.17487/RFC4908, June 2007,
<http://www.rfc-editor.org/info/rfc4908>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<http://www.rfc-editor.org/info/rfc6333>.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
<http://www.rfc-editor.org/info/rfc7227>.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Christian Jacquenet
France Telecom
Rennes
France
Email: christian.jacquenet@orange.com
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Tirumaleswar Reddy
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: tireddy@cisco.com
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