Network Working Group Amjad. Inamdar Internet-Draft R. Singh Intended status: Standards Track Cisco Expires: September 13, 2014 March 12, 2014 IKEv2 based lightweight secure data communication draft-amjads-ipsecme-ikev2-data-channel-01 (D-IKE) Abstract The Internet Key Exchange (IKEv2) protocol provides authentication, confidentiality, integrity, data-origin authentication and anti- replay. Currently, IKEv2 is mainly used as a control channel to negotiate IPsec SA(s). IPsec is not well suited to provide transport layer security for applications as it resides at the network layer and most of the IPsec implementations require integration into operating systems making it difficult to deploy. IPsec uses different sessions for control and data traffic which is not NAT and load balancer friendly. TLS/DTLS, the other popular security mechanism to provide the above security services does not mandate mutual peer authentication and Diffie Hellman exchange. This document describes an IKEv2 based lightweight secure data communication protocol and a way to provide transport layer security for UDP client/server applications. The protocol provides integrity protected encryption and integrity-only protection based on application needs. As most of the IoT applications are UDP based, IKEv2 can be used for key management as well secure data communication in IoT due to its simplicity, scalability, lightweightedness and ease of deployment. 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 September 13, 2014. Inamdar & Singh Expires September 13, 2014 [Page 1] Internet-Draft IKEv2 data channel March 2014 Copyright Notice Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. D-IKE comparision with IPsec . . . . . . . . . . . . . . . . 3 4. D-IKE comparision with DTLS . . . . . . . . . . . . . . . . . 4 5. D-IKE Description . . . . . . . . . . . . . . . . . . . . . . 4 6. Securing UDP applications with D-IKE . . . . . . . . . . . . 4 7. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . 7 9. D-IKE capabilities . . . . . . . . . . . . . . . . . . . . . 7 9.1. Encryption and Integrity protection . . . . . . . . . . . 7 9.2. Integrity only protection . . . . . . . . . . . . . . . . 8 10. D-IKE negotiation . . . . . . . . . . . . . . . . . . . . . . 8 11. D-IKE packet and payload formats . . . . . . . . . . . . . . 9 11.1. D-IKE_SUPPORTED Notify payload . . . . . . . . . . . . . 9 11.2. D-IKE Control and Data packets . . . . . . . . . . . . . 10 11.3. D-IKE payload . . . . . . . . . . . . . . . . . . . . . 11 12. Security Considerations . . . . . . . . . . . . . . . . . . . 11 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 15. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 12 15.1. Draft -01 . . . . . . . . . . . . . . . . . . . . . . . 12 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 16.1. Normative References . . . . . . . . . . . . . . . . . . 13 16.2. Informative References . . . . . . . . . . . . . . . . . 13 Appendix A. Design decisions . . . . . . . . . . . . . . . . . . 13 A.1. Use of the existing IKEv2 control channel . . . . . . . . 13 A.2. IKEv2 header modification . . . . . . . . . . . . . . . . 14 A.3. Use of separate UDP port for data channel . . . . . . . . 14 Appendix B. Possible extensions . . . . . . . . . . . . . . . . 14 B.1. Securing TCP client/server applications using D-IKE . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Inamdar & Singh Expires September 13, 2014 [Page 2] Internet-Draft IKEv2 data channel March 2014 1. Introduction The Internet Key Exchange Protocol version 2 (IKEv2), specified in RFC5996 [1], is a UDP based protocol that provides a secure communication channel similar to ESP defined in RFC4303 [2]. IKEv2 defines mechanisms for mutual authentication of peers, key management, SA management and exchange of configuration information. IKEv2 is mainly used as a secure control channel to negotiate child IPsec SAs. As IKEv2 provides encryption, integrity protection, data origin authenication and replay protection similar to ESP, IKEv2 can be leveraged for secure data communication. This document defines an IKEv2 based secure data communication mechanism (henceforth referred to as D-IKE) and describes a way to secure UDP applications with D-IKE. While the IKE control channel is always encryption and integrity protected, the IKE data channel can provide encryption and integrity protection as well as integrity-only protection depending on the needs of the application. 2. Terminology 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 [7]. 3. D-IKE comparision with IPsec o D-IKE being UDP based is easier to deploy as it resides in the operating system application space and does not require integration with the operating system kernel unlike most of the IPsec implementations o D-IKE is lighter with fewer keys and protocol exchanges as it uses the same channel for control messages and data o D-IKE is simpler as it does not involve programming the Security Policy Database (SPD) o D-IKE being at transport layer is better suited to provide granular and end-to-end security to applications than IPsec which provides network layer security suitable for site to site o D-IKE control and data channels run over a single UDP port and hence D-IKE is load balancer friendly Inamdar & Singh Expires September 13, 2014 [Page 3] Internet-Draft IKEv2 data channel March 2014 4. D-IKE comparision with DTLS o D-IKE provides better enforcement of security through mandatory mutual peer authentication and Diffie Hellman key exchange o D-IKE supports comprehensive authentication methods and has built- in support for mobility, DOS attack mitigation and load balancing 5. D-IKE Description Each UDP application using D-IKE for security will use different UDP port numbers. So with D-IKE, IKEv2 packets are no longer identified by UDP ports 500 and 4500. D-IKE will use a different UDP port number for each UDP application to carry the D-IKE control messages for IKEv2 negotiation as well as application data. The first octet in the UDP payload will identify D-IKE control and data packets. D-IKE control packets will carry the IKEv2 header and payloads as defined in RFC5996 [1] and will be used to negotiate a childless IKEv2 session between UDP client and server. D-IKE data packets will carry encrypted and authenticated UDP application data. The following diagram depicts the format of UDP encapsulated D-IKE control and Data packets. +------------+------+----------+---------------------------+ | UDP Header | Type | RESERVED | D-IKE Control/Data Packet | +------------+------+----------+---------------------------+ |<---------------- UDP Payload -------------->| Encapsulation of D-IKE packets D-IKE can provide integrity-only protection in addition to integrity protected encryption. D-IKE does not negotiate child IPsec SAs in the IKEv2 initial exchange and subsequently as depicted in D-IKE Negotiation section, similar to Childless IKEv2 defined in RFC6023 [3]. Please refer the appendix section of this document for details on the alternative mechanisms that were considered for data communication over IKEv2 and their drawbacks. 6. Securing UDP applications with D-IKE This document introduces the concept of D-IKE sockets to secure communication between UDP client/server applications. D-IKE socket is an IKEv2 session between a UDP client and server uniquely Inamdar & Singh Expires September 13, 2014 [Page 4] Internet-Draft IKEv2 data channel March 2014 identified by the 4 tuple of client and server IP addresses and UDP ports. +--------------+ +--------------+ | UDP Client | | UDP Service | +--------------+ +--------------+ | D-IKE socket | | D-IKE socket | +--------------+ +--------------+ | UDP | | UDP | +--------------+ +--------------+ | IP |<------------>| IP | +--------------+ +--------------+ D-IKE Sockets o A UDP service will register with D-IKE socket specifying the UDP port it wants to listen to. D-IKE will listen on the UDP port number on behalf of the application o A UDP client will open a D-IKE socket specifying the server IP address and the UDP port number. D-IKE will open a UDP socket to the server on behalf of the client o D-IKE will initiate an IKEv2 session without any child SA from UDP client to the server o After successful negotiation of IKEv2 session, the client and server can securely exchange data over D-IKE socket UDP Client UDP Server ---------- ---------- | | |<-------- IKE negotiation --------->| | | |<----- Secure Data Transfer ------->| | | Secure UDP communication over D-IKE For a node running multiple UDP applications(Clients and/or Services), each UDP application will have a unique D-IKE socket Inamdar & Singh Expires September 13, 2014 [Page 5] Internet-Draft IKEv2 data channel March 2014 +----------------+----------------+----------------+ | UDP App 1 | UDP App 2 | UDP App N | +----------------+----------------+----------------+ | D-IKE socket 1 | D-IKE socket 2 | D-IKE socket N | +----------------+----------------+----------------+ | UDP | +--------------------------------------------------+ | IP | +--------------------------------------------------+ D-IKE socket per UDP Application A well known UDP service can simultaneously open a UDP socket as well as D-IKE socket. +--------------+ +---------------------------+ +------------+ | UDP Client | | UDP Service | | UDP Client | +--------------+ +---------------------------+ +------------+ | D-IKE socket | | D-IKE socket | UDP Socket |<-->| UDP Socket | +--------------+ +--------------+------------+ +------------+ | UDP |<-->| UDP | |<-- Unsecured -->| +--------------+ +--------------+ Communication |<----- Secure ----->| Communication Securing UDP Applications using D-IKE The following diagram shows the format of D-IKE packet. |<------------- D-IKE packet -------------->| +----+------+--------+-------------+---------+----------+ | IP | UDP | D-IKE | UDP App | D-IKE | D-IKE | | | | Header | Data | Trailer | Checksum | +----+------+--------+-------------+-- ------+----------+ | |<----- Encrypted ----->| |<----- Integrity Protected ---->| D-IKE packet format D-IKE packet consists of D-IKE header, UDP application data, an optional D-IKE trailer and D-IKE integrity checksum value. Inamdar & Singh Expires September 13, 2014 [Page 6] Internet-Draft IKEv2 data channel March 2014 7. Benefits o Lightweight, scalable and simpler with fewer keys and protocol exchanges o Support for integrity-only protection, in addition to integrity protected encryption o Works seamlessly with load balancers and PAT devices as D-IKE uses the same UDP port as the IKEv2 control channel 8. Protocol Outline This document proposes following extensions to IKEv2 protocol for data communication: o IKEv2 Notify type 'D-IKE_SUPPORTED' to negotiate the use of IKEv2 for data communication o D-IKE packet formats 9. D-IKE capabilities D-IKE will support the following data protection modes: o Encryption and Integrity protection o Integrity only protection 9.1. Encryption and Integrity protection This protection mode provides encryption and integrity protection of D-IKE packets similar to the IKEv2 Encrypted payload as defined in RFC5996 [1] The UDP app data and D-IKE trailer are encrypted and the D-IKE header, UDP app data and D-IKE trailer are integrity protected. +----+------+--------+-------------+---------+----------+ | IP | UDP | D-IKE | UDP App | D-IKE | D-IKE | | | | Header | Data | Trailer | Checksum | +----+------+--------+-------------+-- ------+----------+ | |<----- Encrypted ----->| |<----- Integrity Protected ---->| Encryption and Integrity protection Inamdar & Singh Expires September 13, 2014 [Page 7] Internet-Draft IKEv2 data channel March 2014 9.2. Integrity only protection This protection mode provides integrity protection of IKEv2 data packets and no encryption similar to ESP null encryption as described in RFC4303 [2]. This is suitable for applications that just need data integrity and not confidentiality such as routing protocol exchanges. It may be noted that integrity only protection applies only to D-IKE packets and that D-IKE control packets will always use integrity protected encryption. The UDP app data and D-IKE trailer are encrypted and the D-IKE header, UDP app data and D-IKE trailer are integrity protected. +----+------+--------+-------------+----------+ | IP | UDP | D-IKE | UDP App | D-IKE | | | | Header | Data | Checksum | +----+------+--------+-------------+----------+ |<---- Integrity ----->| Protected Integrity only protection 10. D-IKE negotiation IKEv2 nodes can negotiate to use D-IKE and its capabilities by exchanging D-IKE_SUPPORTED Notify type in IKE_SA_INIT exchange. o IKEv2 initiator can communicate its intent to use D-IKE by including a notify payload of type D-IKE_SUPPORTED along with the proposed capabilities in IKE_SA_INIT request o IKEv2 responder can indicate its willingness to use D-IKE with the proposed capabilities by including a notify payload of type D-IKE_SUPPORTED along with the same capabilities in IKE_SA_INIT response o If the capabilities proposed by IKEv2 Initiator are not acceptable to IKEv2 responder, it MUST NOT include D-IKE_SUPPORTED Notify type in IKE_SA_INIT response o The absence of Notify payload of type D-IKE_SUPPORTED in IKE_SA_INIT response indicates the incapability or unwillingness of the IKEv2 responder to use D-IKE o If IKEv2 responder does not include the same capabilities as proposed by IKEv2 initiator, IKEv2 initiator MUST treat this as unsuccessful negotiation of D-IKE Inamdar & Singh Expires September 13, 2014 [Page 8] Internet-Draft IKEv2 data channel March 2014 o On unsuccessful negotiation of D-IKE, IKEv2 initiator and responder MUST NOT use D-IKE for data transfer. However rest of the IKEv2 negotiation can proceed as normal o On successful negotiation of D-IKE, IKEv2 Initiator and Responder MUST exclude any payloads related to Child SA negotiation in IKE_AUTH exchange and can use D-IKE for data transfer Initiator Responder ------------------------------------------------------ HDR, SAi1, KEi, Ni [N(D-IKE_SUPPORTED)] --> <-- HDR, SAr1, KEr, Nr, [CERTREQ] N(D-IKE_SUPPORTED) HDR, SK {IDi, [CERT,] [CERTREQ,] [IDr,] AUTH, [CP(CFG_REQUEST)] --> <-- HDR, SK {IDr, [CERT,] AUTH, [CP(CFG_REPLY)] IKEv2 data channel negotiation 11. D-IKE packet and payload formats 11.1. D-IKE_SUPPORTED Notify payload 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload !C! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Protocol ID ! SPI Size ! Notify Message Type ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Flags ! RESERVED ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D-IKE_SUPPORTED Notify payload o Protocol ID (1 octet): MUST be 1, as this message is related to an IKEv2 SA o SPI Size (1 octet): MUST be zero, in conformance with section 3.10 of [RFC5996] Inamdar & Singh Expires September 13, 2014 [Page 9] Internet-Draft IKEv2 data channel March 2014 o Notify Message Type (2 octets): MUST be xxxxx, the value assigned for D-IKE_SUPPORTED by IANA o Flags (8 bits): Specify the IKEv2 Data channel properties * bit 0: 0 - Encryption and Integrity protection 1 - Integrity-only protection * bit 1-7: Reserved, sender MUST set these bits to zero and receiver MUST ignore it 11.2. D-IKE Control and Data packets The first octet in the UDP payload will identify D-IKE control and data packets. D-IKE control packets will carry the IKEv2 header and payloads as defined in RFC 5996 and will be used to negotiate a childless IKEv2 session between UDP client and server. D-IKE data packets will carry encrypted and authenticated UDP application data. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ IKEv2 Header and payloads ~ | or | | D-IKE data payload | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D-IKE Control and Data packets o Type (1 octet, unsigned integer): Identifies D-IKE control and data packet * 0 - D-IKE control packet * 1 - D-IKE data packet * 2 - 7 - RESERVED Inamdar & Singh Expires September 13, 2014 [Page 10] Internet-Draft IKEv2 data channel March 2014 11.3. D-IKE payload 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SPI | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Initialization Vector | | (length is block size for encryption algorithm) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Encrypted/Cleartext Data ~ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Padding (0-255 octets) | +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ | | Pad Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Integrity Checksum Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D-IKE payload o Length (2 octets, unsigned integer): Length in octets of the entire IKEv2 Data packet o Reserved (2 octets): Sender MUST set these bits to zero and receiver MUST ignore these bits o SPI (8 octets): A value used by receiver to lookup the session associated with the packet in order to verify integrity and decrypt the data packet. This value is usually the data packet receiver's IKE SPI o Sequence Number (4 octets): This field identifies the D-IKE packet sequence numbers, used for anti-replay checks 12. Security Considerations This protocol variation inherits all the security properties of regular IKEv2 as described in [RFC5996]. The new notification carried in the initial exchange advertises the capability, and cannot be forged or added by an adversary without being detected, because the response to the initial exchange is authenticated with the AUTH Inamdar & Singh Expires September 13, 2014 [Page 11] Internet-Draft IKEv2 data channel March 2014 payload of the IKE_AUTH exchange. IKEv2 data payload inherits all security properties of ESP protocol defined in [RFC4303]. 13. IANA Considerations This document introduces one new IKEv2 Notification Message types as described in Section 11.1. The new Notify Message Types must be assigned values between 16429 and 40959. o D-IKE_SUPPORTED For UDP applications that need a well known port number to secure the application using D-IKE (for example, CoAP over D-IKE), the port number MUST be reserved from IANA. 14. Acknowledgements We would like to thank following people (in alphabetical order) for their review comments and valuable suggestions for idea and initial version of the document: Amit Phadnis, Arif Shouqi, Balaji B L, Brian Weis, Cheryl Madson, Frederic Detienne, J P Vasseur, Kalyani Garigipati, Mike Sullenberger, Naresh Sunkara, Nick Doyle, Paul Hoffman, Rajiv Shankar Daulath, Ramesh Nethi, Sandeep Rao, Scott Fluhrer, and Thamil Kandasamy. 15. Change Log This section lists all the changes in this document. NOTE TO RFC EDITOR: Please remove this section in before final RFC publication. 15.1. Draft -01 Reworked the draft with more focus on UDP application security. Updated the problem statement. Added comparision with IPsec and TLS/ DTLS. Updated D-IKE Notify and Data payloads. Added possible extensions. 16. References Inamdar & Singh Expires September 13, 2014 [Page 12] Internet-Draft IKEv2 data channel March 2014 16.1. Normative References [1] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key Exchange Protocol Version 2: IKEv2", RFC 5996, September 2010. [2] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [3] Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A Childless Initiation of IKEv2 SA", RFC 6023, October 2010. [4] Smyslov, V., "IKEv2 Fragmentation", draft-ietf-ipsecme- ikev2-fragmentation-02 (work in progress), September 2013. [5] Rowles, S., Yeung, A., Tran, P., and Y. Nir, "Group Key Management using IKEv2", draft-yeung-g-ikev2-06 (work in progress), April 2013. [6] Kivinen, T., "Minimal IKEv2", draft-ietf-lwig- ikev2-minimal-00.txt (work in progress), April 2013. [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 16.2. Informative References [8] Devarapalli, V. and K. Weniger, "Redirect Mechanism for IKEv2", RFC 5685, November 2009. Appendix A. Design decisions This section describes the alternative mechanisms for data communication over IKEv2 that were considered and their drawbacks. A.1. Use of the existing IKEv2 control channel The existing IKEv2 control channel can be used for data transfer using a new IKEv2 exchange type DATA exchange similar to INFORMATIONAL exchange, and a new payload type to encapsulate cleartext data that will be protected by Encrypted payload. A drawback with this approach is that the data packets will incur the overhead of IKEv2 header (28 octets) and a minimum of two generic payload headers (4 octets each) with a total protocol overhead of 36 octets per data packet. Also, it is difficult to support unacknowledged data transfer and integrity-only protection for data packets. Inamdar & Singh Expires September 13, 2014 [Page 13] Internet-Draft IKEv2 data channel March 2014 A.2. IKEv2 header modification IKEv2 header can be modified to allow differentiation between control and data packets using the first four bytes of the header and the rest of the header can be different for control and data packets. A possible way to accomplish this is to move the Exchange type field to the beginning of IKEv2 header. The obvious drawback with this approach is that it is not backward compatible with existing IKEv2 protocol. Also, it makes it difficult to support unacknowledged data transfer and integrity-only protection for data packets. A.3. Use of separate UDP port for data channel A separate UDP port e.g 501 can be used for IKEv2 data channel that allows to leverage the IKEv2 protocol's security and reliability mechanisms and security parameters for data communication while avoiding the overhead of IKEv2 header and generic payload headers for data packets. Use of a fixed UDP port for data channel instead of dynamically negotiated UDP ports has the advantage of not requiring the firewalls to snoop the IKEv2 control channel to be able to determine and allow the traffic on data channel UDP port. A drawback with this approach is that the use of different ports for IKEv2 control and data channels makes it difficult for load balancers to associate an IKEv2 control channel with its data channel when there are multiple IKEv2 initiators behind a PAT device. Also when IKEv2 initiator is behind a PAT device, the data packets from responder will be dropped by the PAT device as port 501 will not be open unless there is data traffic from initiator. Appendix B. Possible extensions This section describes the possible extensions to D-IKE protocol. B.1. Securing TCP client/server applications using D-IKE D-IKE can be used to secure TCP applications using one of the following methods. o While IKE control channel can run over UDP, the IKE data channel can negotiate and run over a TCP session carring D-IKE protected application data. A drawback with this approach is that using differnet sessions for control and data may not be friendly with load balancers Inamdar & Singh Expires September 13, 2014 [Page 14] Internet-Draft IKEv2 data channel March 2014 o If IKEv2 were to run over TCP, IKEv2 over TCP can be used to secure TCP applications o D-IKE tunnel mode can be defined that can encapsulate TCP or any other protocol over D-IKE tunnel Authors' Addresses Amjad S. Inamdar Cisco Systems India Pvt. Ltd. SEZ Unit, Cessna Business Park Sarjapur Marathahalli Outer Ring Road Bangalore, Karnataka 560087 India Phone: +91 80 4426 4834 Email: amjads@cisco.com Rajeshwar Singh Janwar Cisco Systems India Pvt. Ltd. SEZ Unit, Cessna Business Park Sarjapur Marathahalli Outer Ring Road Bangalore, Karnataka 560087 India Phone: +91 80 4426 2731 Email: rsj@cisco.com Inamdar & Singh Expires September 13, 2014 [Page 15]