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 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 May 20, 2016. Boucadair, et al. Expires May 20, 2016 [Page 1] Internet-Draft DHCP for MPTCP November 2015 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 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 . . . . . . . . . . . . . . . . . . . . . . . . . 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. Boucadair, et al. Expires May 20, 2016 [Page 2] Internet-Draft DHCP for MPTCP November 2015 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. Boucadair, et al. Expires May 20, 2016 [Page 3] Internet-Draft DHCP for MPTCP November 2015 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) Boucadair, et al. Expires May 20, 2016 [Page 4] Internet-Draft DHCP for MPTCP November 2015 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. Boucadair, et al. Expires May 20, 2016 [Page 5] Internet-Draft DHCP for MPTCP November 2015 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. Boucadair, et al. Expires May 20, 2016 [Page 6] Internet-Draft DHCP for MPTCP November 2015 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 Boucadair, et al. Expires May 20, 2016 [Page 7] Internet-Draft DHCP for MPTCP November 2015 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. Boucadair, et al. Expires May 20, 2016 [Page 8] Internet-Draft DHCP for MPTCP November 2015 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. Boucadair, et al. Expires May 20, 2016 [Page 9] Internet-Draft DHCP for MPTCP November 2015 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, . [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, DOI 10.17487/RFC2131, March 1997, . [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997, . [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, . [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, DOI 10.17487/RFC3396, November 2002, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [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, . [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, . Boucadair, et al. Expires May 20, 2016 [Page 10] Internet-Draft DHCP for MPTCP November 2015 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, . [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, . [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, . [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, . 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 Boucadair, et al. Expires May 20, 2016 [Page 11] Internet-Draft DHCP for MPTCP November 2015 Tirumaleswar Reddy Cisco Systems, Inc. Cessna Business Park, Varthur Hobli Sarjapur Marathalli Outer Ring Road Bangalore, Karnataka 560103 India Email: tireddy@cisco.com Boucadair, et al. Expires May 20, 2016 [Page 12]