| Network Working Group | M. Jethanandani |
| Internet-Draft | |
| Intended status: Standards Track | B. Weis |
| Expires: January 23, 2019 | Cisco Systems |
| K. Patel | |
| Arrcus | |
| D. Zhang | |
| Huawei | |
| S. Hartman | |
| Painless Security | |
| U. Chunduri | |
| A. Tian | |
| Ericsson Inc. | |
| J. Touch | |
| USC/ISI | |
| July 22, 2018 |
Negotiation for Keying Pairwise Routing Protocols in IKEv2
draft-mahesh-karp-rkmp-06
This document describes a mechanism to secure the routing protocols which use unicast to transport their signaling messages. Most of such routing protocols are TCP-based (e.g., BGP and LDP), and the TCP Authentication Option (TCP-AO) is primarily employed for securing the signaling messages of these routing protocols. There are also two exceptions: BFD which is over UDP or MPLS, and RSVP-TE which is over IP (but employs an integrated approach to protecting the signaling messages instead of using IPsec). The proposed mechanism secures pairwise TCP-based Routing Protocol (RP) associations, BFD associations and RSVP-TE associations using the IKEv2 Key Management Protocol (KMP) integrated with TCP-AO, BFD, and RSVP-TE respectively. Included are extensions to IKEv2 and its Security Associations to enable its key negotiation to support TCP-AO, BFD, and RSVP-TE.
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.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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Existing routing protocols using unicast pairwise communication model (e.g., BGP, LDP, RSVP-TE, and BFD) have cryptographic authentication mechanisms that use a key shared between the network devices (devices for short) on the both sides of the model to protect routing message exchanges between endpoints. The unicast key management for these protocols today is limited to statically configured master keys in individual network devices. This document defines a mechanism to secure such pairwise Routing Protocol (RP) associations using IKEv2, allowing network devices to automatically exchange keying material related information between the network devices. To benefit the discussion, it is implied that the routing protocols mentioned in the remainder of this memo use unicast pair-wise communication model, unless otherwise mentioned.
This memo assumes that network devices need to be provisioned with some credentials for a one-to-one authentication protocol. Any method for a pairwise security protocol specified for use with IKEv2 is applicable.
When two network devices running a routing protocol have not yet established a secure association, the two endpoints need to select a KMP solution that meets their mutual requirements and use that KMP solution to establish the required security before sending out any routing protocol packets. The KMP solution typically enables the network devices to perform mutual authentication using their provisioned credentials and to agree upon certain keying material as the result of an successful authentication. The keying material then can be applied to secure the routing protocol.
This section lists the key terminologies used throughout the memo.
Network Device: In this memo, a router or any other type of device participating in routing protocols is referred to as a network device.
Key Management Database (KDMB): A KDMB is a conceptual database which locates in the middle of a key management protocol and a routing protocol to provide the long-term key management service. Therefore, the RP and the KMP need not to cooperate directly.
The following acronyms and abbreviations are used throughout this memo.
As illustrated in Figure 1, this work makes use the state machine of IKEv2. Assume a network device and its peer device are in State 1. That is, the device has not authenticated its peer device and does not have the keys to secure the routing protocol packets which it would like to exchange with the peer. Before sending any routing protocol packets, the two devices need to perform a IKE_SA_INIT exchange. If the IKE_SA_INIT exchange succeeds, both network devices are transferred to State 2 where they have agreed upon certain keying material but have decided how to use the material to derive keys to secure routing protocols. To achieve this objective, the two network devices perform an IKE_AUTH exchange, in which both endpoints try to authenticate each other and generate security associations for the routing protocol they intend to support. If the IKE_AUTH exchange succeeds, the network devices transfer their state to State 3 where both endpoints are authenticated and keys for securing the routing protocols are generated. If the endpoints intend to generate new SAs for routing protocols by using the keying material already generated, they can just perform an CREATE_CHILD_SA exchange. A discussion in more details can be found in Section 4.
-----------------------
=======> | Not Authenticated |==========
|| | No RP Keys | ||
|| ----------------------- IKE_SA_INIT exchange
|| State 1 ||
|| ||
INFORMATIONAL VV
|| --------------------------
|| | Privacy Keys Exchanged |
|| | No RP Keys |
|| --------------------------
|| || State 2
|| ||
|| |-------------------- IKE_AUTH exchange
=========| Authenticated | <============
| RP Keys Derived | ====
-------------------- ||
State 3 ^^ ||
|| CREATE_CHILD_SA
|| ||
===============
Figure 1: State Diagram
Three types of keys mentioned the discussion of this memo are listed as follows:
The KARP analysis in BGP, LDP, PCEP, and MSDP indicates that all of these routing protocols need a dedicated key management protocol[RFC6952] to confidentially exchange keying material between endpoints. There is no need to define an entirely new protocol for this purpose, when existing mature protocol exchanges and methods have been vetted. This draft makes use of the IKEv2 protocol exchanges, state machine, and policy definitions to define a dedicated key management protocol.
The notations contained in the IKEv2 message are defined as follows.
| Notation | Payload |
|---|---|
| AUTH | Authentication |
| CERT | Certificate |
| CERTREQ | Certificate Request |
| D | Delete |
| HDR | IKEv2 Header (not a payload) |
| IDi | Identification - Initiator |
| IDr | Identification - Responder |
| KE | Key Exchange |
| Ni, Nr | Nonce |
| N | Notify |
| SA | Security Association |
| SK | Encrypted and Authenticated |
| TSi | Traffic Selector - Initiator |
| TSr | Traffic Selector - Responder |
A network device desiring to negotiate a key and other associated parameters for a pair-wise routing protocol to a peer initiates an IKE_SA_INIT exchange defined in IKEv2. The IKE_SA_INIT exchange is a two-message exchange that allows the network devices to negotiate cryptographic algorithms, exchange nonce information, and do a Diffie-Hellman (DH) exchange, for their routing protocols, after which protocols on these network devices can communicate privately. Note that at the end of a IKE_SA_INIT exchange the endpoints on the both sides have not authenticated each other yet. For the details of this exchange, refer to IKE_SA_INIT in IKEv2.
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SAi1, KEi, Ni -->
<-- HDR, SAr1, KEr, Nr, [CERTREQ,]
IKE_SA_INIT
Up to this step, this work introduces no change to IKEv2.
Next, the network devices perform an IKE_AUTH exchange defined in IKEv2. The SA payloads contain the security policies for a key and the associated parameters (as defined in Header and Payload Formats), and the TS payloads contains traffic selectors as defined in IKEv2. For the details of the exchange please refer to IKE_AUTH in IKEv2.
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SK {IDi, [CERT,] [CERTREQ,]
[IDr,] AUTH, SAi2, TSi, TSr} -->
<-- HDR, SK {IDr, [CERT,] AUTH,
SAr2, TSi, TSr}
IKE_AUTH
The network devices may then destroy the state associated with the IKEv2 SA, continuing to use the RP policy and keying material, or they may choose to retain them for further usages. Note that this policy differs from IKEv2/IPsec, where the deletion of the IKEv2 SA necessitates the deletion of the IPsec SAs. If both the network devices choose to retain them, they may use the IKEv2 SA to subsequently agree upon replacement policy for the same RP, or agree upon the policy and keying material for another routing protocol. Either case will require the use of the IKEv2 CREATE_CHILD_SA exchange as defined in IKEv2.
A CREATE_CHILD_SA exchange therefore can be triggered in order to
Peer (Initiator) Peer (Responder)
-------------------- ------------------
HDR, SK {[N], SA, Ni, [KEi],
[TSi, TSr]} -->
<-- HDR, SK {SA, Nr, [KEr],
[TSi, TSr]}
CREATE_CHILD_SA
A CREATE_CHILD_SA exchange MAY be initiated by either end of the SA after the initial exchanges are completed. All messages in a CREATE_CHILD_SA exchange are cryptographically protected using the cryptographic algorithms and keys negotiated in the initial exchange.
For details on the exchange, refer to the CREATE_CHILD_SA exchange as defined in IKEv2.
Peer (Initiator) Peer (Responder)
------------------- ------------------
HDR, SK {[N,] [D,] ... } -->
<-- HDR, SK {[N,] [D,] ... }
INFORMATIONAL
The IKEv2 INFORMATIONAL exchange is also useful for deleting specific IKEv2 SAs or sending status information. The Notify (N) and Delete (D) payloads are as those defined by IKEv2. For example, if the Responder refused to accept one of Proposals sent by the Initiator, it would return an INFORMATIONAL exchange of type NO_PROPOSAL_CHOSEN instead of the response to CREATE_CHILD_SA.
IKEv2 is used to dynamically derive keying material information between the two network devices trying to establish or maintain a routing protocol neighbor adjacency. Typically network devices running the routing protocols establish neighbor adjacencies at the routing protocol level. These routing protocols may run different security algorithms that provide transport level security for the protocol neighbor adjacencies. Depending on the security algorithm used, the routing protocols are configured with security algorithm specific keys that are either long term keys or short term session keys. These keys are specific to the security algorithms used to enforce transport level security for the routing protocols.
A routing protocol causes IKEv2 to execute when it needs keying material to establish neighbor adjacency. This can be as a result of the routing protocol neighbor being configured, neighbor changed or updated, a local rekey policy decision, or some other event dictated by the implementation. The keying material would allow the network devices to then independently generate the same key and establish an IKEv2 session between them. This is typically done by the Initiator (IKEv2 speaker) initiating an IKEv2 IKE_SA_INIT exchange mentioned in the section 2.1 towards its IKEv2 peer. As part of IKEv2_INIT exchange, IKEv2 will send a message to the peer's IKEv2 port. The format of the message is explained in Section 6. The procedure to exchange key information is explained in Section 6. Once the keying material information is successfully exchanged by both of the IKEv2 speakers, the IKEv2 neighbor adjacency may be torn down or kept around as explained in Section 6.
The master key data received from IKEv2 peers is stored in the separate Key Management Database known as KMDB. KMDB follows the guidelines in Database of Long Lived Symmetric Cryptographic Keys, and each entry consists of Key specific information, Security algorithm to which the Key is applicable to, Routing Protocol Clients of interest, and the announcing KMP Peer. KMDB is also used to notify the routing protocols about the key updates. Typically keying material information is exchanged whenever a routing protocol is about to create a new neighbor adjacency. This is considered as an Initial Key exchange mode. Keying material information is also exchanged to refresh existing key data on an already existing neighbor adjacency. This is considered as Key rollover exchange mode. The following sections describes their detail behavior.
Routing protocols informs IKEv2 of its new neighbor adjacency. It does so by creating a local entry in KMDB which consists of a Security algorithm, Key specific information, routing protocol client and the routing protocol neighbor. Upon a successful creation of such an entry IKEv2 initiates KMP peering with the neighbor and starts an initial IKE_SA_INIT exchange explained in Section 3.1 followed by the RP_AUTH exchanged explained in Section 3.2. Once the key related information is successfully exchanged, KMDB may invoke the routing protocol client to provide key specific information updates if any.
A routing protocol may need to perform the key selection and rollover in cooperation with KMDB. Such a procedure is described in Section 3 of Database of Long-Lived Symmetric Cryptographic Keys. Details of how RP interact with KMDB and deals with multiple keys during rollover are also described in that section. When a routing protocol uses TCP-AO to secure its message exchanges, conditions could be a little more complex. Typically, a TCP-AO implementation has its own key tables. TCP-AO may only carry out key management operations on the key tables if the key information maintained in KDMB needs not to be updated. In [I-D.chunduri-karp-using-ikev2-with-tcp-ao], a Gatekeeper (GK) mechanism is provided to orchestrate the key management operations on the TCP-AO key tables and KMDB.
Protocol interaction between KMP and its client routing protocols is typically done using KMDB. Routing protocols may be able to update KMDB by performing key selection and rollover operations. During a key selection, if there is no appropriate key found in the conceptual database, as a part of the KMDB update, IKEv2 is initiated to connect with its appropriate IKEv2 peer so as to generate a new key. When a key needs to be revoked, it is also the responsibility of IKEv2 to inform its peer to guarantee the synchronization of the databases on the both sides. In addition, when a key is obsoleted for some reasons when it is being used by a client routing protocol, the routing protocol may need to be informed of this update. For the routing protocols which using TCP-AO to secure their message exchanges, a Gatekeeper mechanism is provided to trigger the update of keys and manage the key revocation [I-D.chunduri-karp-using-ikev2-with-tcp-ao].
The protocol defined in this memo uses IKEv2 payload definitions. However, new security policy definitions are described to support security transforms and policy defined by routing protocol documents.
The TCP Authentication Option (TCP-AO) is primarily intended for BGP and other TCP-based routing protocols. In order for IKEv2 to negotiate TCP-AO policy, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. This memo proposes adding a new Protocol Identifier to the table, with a Protocol Name of "TCP_AO" and a value of 6.
The Security Association (SA) payload contains a list of Proposals, which describe one or more sets of policies that a network device is willing to use to protect a routing protocol. In the Initiator's message, the SAi2 payload contains a list of Proposal payloads (as defined in the next sections), each of which contains a single set of policy that can be applied to the packets described in the Traffic Selector (TS) payloads in the same exchange. Each set of policy is given a particular "Proposal Number" uniquely identifying this set of policy.
The responder includes a single Proposal payload in it's SA policy, which denotes the choice it has made amongst the initiator's list of Proposals. Any attributes of a selected transform MUST be returned unmodified as explained in IKEv2 section 3.3.6. The initiator of an exchange MUST check that the accepted offer is consistent with one of its proposals, and if not MUST terminate the exchange.
Each Proposal has a list of Transform (T) substructures, each of which describe a particular set of cryptographic policy choices. A TCP-AO proposal uses the INTEG transform to negotiate the MKT Message Authentication Code (MAC) algorithm. Cryptographic Algorithms for TCP-AO describes HMAC-SHA-1-96, AES-128-CMAC-96, which map to the existing INTEG transform IDs of AUTH_HMAC_SHA1_96 and AUTH_AES_CMAC_96 respectively. The use of each INTEG algorithm implies the use of a specific KDF (deriving session keys from a master key), and so the choice of a particular INTEG transform ID also specifies the required KDF transform. This will be true for every transform ID used with TCP-AO, as required in RFC 5926 (see Section 3.2 where the "KDF_Alg" is a fixed element of a MAC algorithm definition for TCP-AO).
+-------+---------------------------------+ |Number | Name | +-------+---------------------------------+ | 0 |Options Not Integrity Protected | | 1 |Options Integrity Protected | +-------+---------------------------------
Figure 2: Transform Type 6 - TCP Authentication Option Transform IDs
A TCP-AO proposal also requires a new type of transform, which describes whether TCP options are to be protected by the integrity algorithm. This memo proposes adding a new Transform Type in the IANA registry for "Transform Type Values" [IKEV2-TRANSFORM-TYPES]
The following table shows the Transforms that can be negotiated for a TCP-AO protocol.
Protocol Mandatory Types Optional Types --------------------------------------------------- TCP-AO INTEG, TCP D-H
Figure 3: Mandatory and Optional Transforms for TCP-AO
Figure 4 shows an example of IKEv2 SA Payload including a single Proposal sent in the first message of an IKE_AUTH or CREATE_CHILD_SA exchange. It indicates a willingness to use either of the two MAC algorithms defined in RFC 5926, and is willing to either protect TCP options or not. The SPI value represents the new SendID it is associating with the TCP-AO Master Key Tuple (MKT) policy being negotiated.
SA Payload
|
+--- Proposal #1 ( Proto ID = TCP-AO(T6), SPI size = 1,
| 4 transforms, SPI = 0x01 )
|
+-- Transform INTEG ( Name = AUTH_HMAC_SHA1_96 )
+-- Transform INTEG ( Name = AUTH_AES_CMAC_96 )
+-- Transform TCP ( Name = PROTECT_OPTIONS )
+-- Transform TCP ( Name = NO_PROTECT_OPTIONS )
Figure 4: Example Initiator SA Payload for TCP-AO
SA Payload
|
+--- Proposal #1 ( Proto ID = TCP-AO(6), SPI size = 1,
| 2 transforms, SPI = 0x11 )
|
+-- Transform INTEG ( Name = AUTH_HMAC_SHA1_96 )
+-- Transform TCP ( Name = PROTECT_OPTIONS )
Figure 5: Example Responder SA Payload for TCP-AO
[RFC5925] declares that "KeyID values MAY be the same in both directions of a connection, but do not have to be and there is no special meaning when they are."
Each TCP-AO MAC algorithm specification in Section 3.2 of Crypto for TCP-AO defines the Key_Length as a number of bits <n> needed as keying material for the MAC algorithm.
In order for IKEv2 to negotiate BFD authentication policy, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. This memo proposes adding a new Protocol Identifier to the table, with a Protocol Name of "BFD" and a value of 7.
The base BFD specification defines five authentication mechanisms: Password, Keyed MD5, Meticulous Keyed MD5, Keyed SHA1, and Meticulous Keyed SHA1. Because Password does not use keys, the support of this mechanism is out of the scope of this work. In the other four mechanisms, Keyed MD5 and Meticulous Keyed MD5 use MD5 as the Message Authentication Code (MAC) algorithm, while Keyed SHA1 and Meticulous Keyed SHA1 use SHA1. In [I-D.ietf-bfd-generic-crypto-auth], a generic authentication mechanism and a generic meticulous authentication mechanism which can support various MAC algorithms is proposed.
Therefore, a BFD proposal also requires a new type of transform to identify the type of BFD authentication. This memo proposes adding a new Transform Type in the IANA registry for "Transform Type Values"[IKEV2-TRANSFORM-TYPES]
+-------+---------------------------------+ |Number | Name | +-------+---------------------------------+ | 0 |Base Authentication | | 1 |Base Meticulous Authentication | | 2 |Generic Authentication | | 3 |Generic Meticulous Authentication| +-------+---------------------------------+
Figure 6: Transform Type 7 - BFD Authentication Option Transform IDs
Base Authentication in Figure 6 indicates the keyed (MD5 or SHA-1) authentication mechanism defined in the base BFD specification. Base Meticulous Authentication indicates the meticulous keyed (MD5 or SHA-1) authentication mechanism defined in the base BFD specification. Generic Authentication and Generic Meticulous Authentication indicate the generic keyed authentication and the generic keyed meticulous authentication mechanisms defined in [I-D.ietf-bfd-generic-crypto-auth] respectively.
A BFD proposal uses INTEG transforms to negotiate Message Authentication Code (MAC) algorithms. In the base BFD [RFC5880], keyed MD5 and keyed SHA-1 are adopted. The two algorithms can be identified using existing INTEG transform IDs of AUTH_HMAC_MD5_96 and AUTH_HMAC_SHA1_96 respectively. In [I-D.ietf-bfd-hmac-sha], it is specified that a BFD using the authentication mechanisms defined in [I-D.ietf-bfd-generic-crypto-auth] MUST support HMAC-SHA-256 which can be identified using existing INTEG transform IDs of AUTH_HMAC_SHA2_256_128 [RFC4868].
The BFD KeyID is sent in the SPI field of an IKEv2 proposal. Note that according to [RFC5880], the length of KeyID is 8 bits.
Because in BFD the transport key is the same as the protocol master key, no KDF needs to be negotiated.
The following figure shows the Transforms that can be negotiated for a BFD implementation.
Protocol Mandatory Types Optional Types --------------------------------------------------- BFD BFD, INTEG D-H
Figure 7: Mandatory and Optional Transforms for BFD
In order for IKEv2 to negotiate RSVP-TE authentication policy, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. This memo proposes adding a new Protocol Identifier to the table, with a Protocol Name of "RSVP-TE" and a value of 8.
In the authentication mechanism for RSVP-TE [RFC2747], only HMAC-MD5 is mandated. Therefore, no INTG transform needs to be included in a RSVP-TE proposal.
+-------+---------------------------------+ |Number | Name | +-------+---------------------------------+ | 0 |Not Allowed | | 1 |Allowed | +-------+---------------------------------+
Figure 8: Transform Type 8 - RSVP-TE Transform IDs
A RSVP-TE proposal requires a new type of transform, which indicates whether the integrity handshake (which is used to collect the latest sequence number associated with a key ID) is permitted. This memo proposes adding a new Transform Type in the IANA registry for "Transform Type Values" [IKEV2-TRANSFORM-TYPES]
The RSVP-TE KeyID is sent in the SPI field of an IKEv2 proposal.
The following figure shows the Transforms that can be negotiated for a RSVP-TE implementation.
Protocol Mandatory Types Optional Types --------------------------------------------------- RSVP-TE RSVP-TE, D-H
Figure 9: Mandatory and Optional Transforms for BFD
A Notify Payload (IKEv2 Section 3.10) or Delete Payload (IKEv2 Section 3.11) contains a Protocol ID field. The Protocol ID is set to TCP_AO (6) when a notify message is relevant to the TCP-AO KeyID value contained in the SPI field. Similarly, the Protocol ID is set to BFD (7) when a notify message is relevant to the BFD KeyID value contained in the SPI field, and the Protocol ID is set to RSVP-TE (8) when a notify message is relevant to the RSVP-TE KeyID value contained in the SPI field.
In order for IKEv2 to negotiate TCP-AO authentication policies, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. IANA is requested to add a new Protocol Identifier to the table, with a Protocol Name of "TCP-AO" and a value of 6. A TCP-AO proposal also requires a new type of transform, which describes whether TCP options are to be protected by the integrity algorithm. This memo proposes adding a new Transform Type 6 for this transform in the IANA registry for "Transform Type Values".
In order for IKEv2 to negotiate BFD authentication policies, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. IANA is requested to add a new Protocol Identifier to the table, with a Protocol Name of "BFD" and a value of 7. A BFD proposal also requires a new type of transform, which identifies the type of BFD authentication mechanism. This memo proposes adding a new Transform Type 7 in the IANA registry for "Transform Type Values".
In order for IKEv2 to negotiate RSVP-TE authentication policies, a new Security Protocol Identifier needs to be defined in the IANA registry for "IKEv2 Security Protocol Identifiers" Magic Numbers' for ISAKMP Protocol. IANA is requested to add a new Protocol Identifier to the table, with a Protocol Name of "RSVP-TE" and a value of 8. A RSVP-TE proposal requires a new type of transform, which indicates whether the integrity handshake (which is used to collect the latest sequence number associated with a key ID) is permitted. This memo proposes adding a new Transform Type 8 in the IANA registry for "Transform Type Values".
TBD
During the development of TCP-AO, Gregory Lebovitz noted that a protocol based on an IKEv2 exchange would be a good automated key management method for deriving a TCP-AO master key.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC2747] | Baker, F., Lindell, B. and M. Talwar, "RSVP Cryptographic Authentication", RFC 2747, DOI 10.17487/RFC2747, January 2000. |
| [RFC4868] | Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868, DOI 10.17487/RFC4868, May 2007. |
| [RFC5880] | Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010. |
| [RFC5925] | Touch, J., Mankin, A. and R. Bonica, "The TCP Authentication Option", RFC 5925, DOI 10.17487/RFC5925, June 2010. |
| [RFC5926] | Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms for the TCP Authentication Option (TCP-AO)", RFC 5926, DOI 10.17487/RFC5926, June 2010. |
| [RFC7296] | Kaufman, C., Hoffman, P., Nir, Y., Eronen, P. and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014. |