One document matched: draft-boucadair-mptcp-dhc-05.txt
Differences from draft-boucadair-mptcp-dhc-04.txt
Network Working Group M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Standards Track Orange
Expires: November 10, 2016 T. Reddy
Cisco
May 9, 2016
DHCP Options for Network-Assisted Multipath TCP (MPTCP)
draft-boucadair-mptcp-dhc-05
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
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 November 10, 2016.
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Copyright Notice
Copyright (c) 2016 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. DHCPv6 MPTCP Option . . . . . . . . . . . . . . . . . . . . . 5
3.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 6
4. DHCPv4 MPTCP Option . . . . . . . . . . . . . . . . . . . . . 7
4.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. DHCPv4 Client Behavior . . . . . . . . . . . . . . . . . 8
5. DHCP Server Configuration Guidelines . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 10
8.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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. 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. Concretely, the
explicit mode has several advantages, e.g.,:
o It does not impose any specific constraint on the location of the
concentrator. For example, the concentrator can be located in any
access network, located upstream in the core network, or located
in a data canter facility.
o Tasks required for activating the explicit mode are minimal. In
particular, this mode does not require any specific routing and/or
forwarding policies for handling outbound packets other than
ensuring that a concentrator is reachable from a CPE, and vice
versa (which is straightforward IP routing policy operation).
o The engineering effort to change the location of a concentrator
for some reason (e.g., to better accommodate dimensioning
constraints, to move the concentrator to a data canter, to enable
additional concentrator instances closer to the customer premises,
etc.) is minimal
o An operator can easily enforce strategies for differentiating the
treatment of MPTCP connections that are directly initiated by an
MPTCP-enabled host connected to a concentrator if the explicit
mode is enabled. Typically, an operator may decide to offload
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MPTCP connections originated by an MPTCP-enabled terminal from
being forwarded through a specific concentrator, or decide to
relay them via a specific concentrator. Such policies can be
instructed to the concentrator. Implementing such differentiating
behavior if the implicit mode is in use may be complex to achieve.
o Multiple concentrators can be supported to service the same CPE,
e.g., a concentrator can be enabled for internal services (to
optimize the delivery of some operator-specific services) while
another concentrator may be solicited for external services (e.g.,
access to the Internet). The explicit mode allows the deployment
of such scenario owing to the provisioning of a concentrator
selection policy table that relies upon the destination IP
prefixes to select the concentrator to involve for an ongoing
MPTCP connection, for instance.
o Because the concentrator's reachability information is explicitly
configured on the CPE, means to guarantee successful inbound
connections can be enabled in the CPE to dynamically discover the
external IP address that has been assigned for communicating with
remote servers, instruct the concentrator to maintain active
bindings so that incoming packets can be successfully redirected
towards the appropriate CPE, etc.
o Troubleshooting and root cause analysis may be facilitated in the
explicit mode since faulty key nodes that may have caused a
service degradation are known. Because of the loose adherence to
the traffic forwarding and routing polices, troubleshooting a
service degradation that is specific to multi-access serviced
customers should first investigate the behavior of the involved
concentrator.
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
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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.
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]).
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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)
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.
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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.
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.
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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.
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
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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
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
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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.
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/:
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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.
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>.
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[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>.
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-08 (work in progress), February 2016.
[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-08 (work in progress), May 2016.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[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
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Christian Jacquenet
Orange
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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