DHC Working Group                                               S. Jiang
Internet-Draft                              Huawei Technologies Co., Ltd
Intended status: Standards Track                                   L. Li
Expires: October 26, 2016 January 9, 2017                                          Y. Cui
                                                     Tsinghua University
                                                               T. Jinmei
                                                           Infoblox Inc.
                                                                T. Lemon
                                                           Nominum, Inc.
                                                                D. Zhang
                                                          April 24,
                                                            July 8, 2016

                             Secure DHCPv6
                       draft-ietf-dhc-sedhcpv6-12
                       draft-ietf-dhc-sedhcpv6-13

Abstract

   The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables
   DHCPv6 servers to pass configuration parameters.  It offers
   configuration flexibility.  If not secured,

   DHCPv6 is vulnerable to
   various attacks.  This document analyzes the includes no deployable security issues of
   DHCPv6 mechanism that can protect
   end-to-end communication between DHCP clients and specifies the secure DHCPv6 servers.  This memo
   describes a mechanism for authentication
   and using public key cryptography to provide
   such security.  The mechanism provides encryption of messages between a DHCPv6 client in all cases, and a DHCPv6
   server.
   can be used for authentication based either on pre-sharing of
   authorized certificates, or else using trust-on-first-use.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 26, 2016. January 9, 2017.

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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   2
   2.  Requirements Language and Terminology . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4   3
   4.  Security Issues of DHCPv6 . . . . . . . . . . . . . . . . . .   4
   5.  Secure DHCPv6 Overview  . . . . . . . . . . . . . . . . . . .   5
     5.1.  Solution Overview . . . . . . . . . . . . . . . . . . . .   5
     5.2.  New Components  . . . . . . . . . . . . . . . . . . . . .   7   6
     5.3.  Support for Algorithm Agility . . . . . . . . . . . . . .   7   6
     5.4.  Applicability . . . . . . . . . . . . . . . . . . . . . .   8   7
   6.  DHCPv6 Client Behavior  . . . . . . . . . . . . . . . . . . .   9   8
   7.  DHCPv6 Server Behavior  . . . . . . . . . . . . . . . . . . .  12  11
   8.  Relay Agent Behavior  . . . . . . . . . . . . . . . . . . . .  14  13
   9.  Processing Rules  . . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Timestamp Check . . . . . . . . . . . . . . . . . . . . .  14
   10.  Extensions for Secure DHCPv6  . . . . . . . . . . . . . . . .  16
     10.1.  14
     9.1.  New DHCPv6 Options  . . . . . . . . . . . . . . . . . . .  16
       10.1.1.  14
       9.1.1.  Certificate Option  . . . . . . . . . . . . . . . . .  16
       10.1.2.  14
       9.1.2.  Signature option  . . . . . . . . . . . . . . . . . .  17
       10.1.3.  Timestamp  15
       9.1.3.  Increasing-number Option  . . . . . . . . . . . . . . . . . .  18
       10.1.4.  17
       9.1.4.  Encrypted-message Option  . . . . . . . . . . . . . .  18
     10.2.  17
     9.2.  New DHCPv6 Messages . . . . . . . . . . . . . . . . . .  19
     10.3. .  18
     9.3.  Status Codes  . . . . . . . . . . . . . . . . . . . . . .  20
   11.  18
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  20
   12.  19
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   13.  19
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23
   14.  21
   13. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  23
   15.  21
   14. Open Issues [RFC Editor: Please remove] . . . . . . . . . . .  25
   16.  23
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     16.1.  23
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     16.2.  23
     15.2.  Informative References . . . . . . . . . . . . . . . . .  26  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27  25

1.  Introduction

   The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315])
   enables
   allows DHCPv6 servers to pass configuration parameters flexibly provide addressing and offers other
   configuration flexibility.  If not being secured, DHCPv6 information relating to local network infrastructure to
   DHCP clients.  The protocol provides no deployable security
   mechanism, and consequently is vulnerable to various attacks.

   This document analyzes the security issues of DHCPv6 and provides the
   following mechanisms for improving a brief summary of the security
   vulnerabilities of DHCPv6 between the DHCPv6 client protocol and then describes a new
   extension to the DHCPv6 server: protocol that provides two additional types of
   security:

   o  the  authentication of the DHCPv6 client and the DHCPv6 server to
      defend against active attacks, such as spoofing attack. spoofing.

   o  the  encryption between the DHCPv6 client and the DHCPv6 server in
      order to protect the DHCPv6 from passive attacks, such as pervasive monitoring.

   Note: this secure mechanism

   The extension specified in this document does not protect outer
   options in Relay-Forward applies only to end-to-end
   communication between DHCP servers and Relay-Reply messages, either added by a
   relay agent toward a server or clients.  Options added by a server toward a relay
   agent.  Communication between a server and a
   relay agent, agents in Relay-Forward messages, and options other than the
   client message in Relay-Reply messages sent by DHCP servers, are not
   protected.  Such communications between relay agents, may be secured through are already protected using the use
   of IPsec, as
   mechanism described described in section 21.1 in [RFC3315].

   The security mechanism specified in this document achieves DHCPv6
   authentication and encryption based on the sender's certificate.  We
   introduce

   This extension introduces two new DHCPv6 messages: Encrypted-Query message the Encrypted-
   Query and the Encrypted-Response message and Four messages.  It defines four new
   DHCPv6 options: Certificate
   option, Signature option, Timestamp option the Certificate, the Signature, the Increasing-
   number, and the Encrypted-message
   option for DHCPv6 authentication and encryption. options.  The Certificate
   option, Signature option, Timestamp option Certificate,
   Signature, and Increasing-number options are used for DHCPv6
   client/server authentication.
   The Encryption-Query message, Encryption-Response message and
   Encrypted-message option are used for
   DHCPv6 encryption.

2.  Requirements Language and 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 [RFC2119] when they
   appear in ALL CAPS.  When these words are not in ALL CAPS (such as
   "should" or "Should"), they have their usual English meanings, and
   are not to be interpreted as [RFC2119] key words.

3.  Terminology

   This section defines terminology specific to secure DHCPv6 used in
   this document.

   secure DHCPv6 client:  A node that initiates the a DHCPv6 request on a
                   link to obtain the DHCPv6 configuration parameters from
                   one or more DHCPv6 servers.  The configuration
                   process is authenticated and encrypted servers using the
                   defined encryption and
                   optional authentication mechanisms defined in this
                   document.

   secure DHCPv6 server:  A node DHCPv6 server that responds to requests from clients
                   using implements the
                   authentication and encryption mechanism mechanisms defined in
                   this document. document, and is configured to use them.

4.  Security Issues of DHCPv6

   DHCPv6 is a client/server protocol that provides managed
   configuration of devices.  It enables a DHCPv6 server to
   automatically configure relevant network parameters on clients.  The
   basic DHCPv6 specification

   [RFC3315] defines security mechanisms, but
   they have some flaws and can be improved.

   The basic DHCPv6 specifications can optionally authenticate the
   origin of messages and validate the integrity of messages using an authentication option mechanism with integrity
   protection.  This mechanism uses a symmetric key pair.  [RFC3315] relies on
   pre-established secret keys.  For any kind of meaningful security,
   each DHCPv6 that is shared by
   the client would need to be configured with its own secret
   key; [RFC3315] provides no mechanism and server for doing this. authentication.  It does not provide any
   key distribution mechanism.

   For the out of band this approach, operators can set up a key database for both
   servers and clients from which the client obtains a key before
   running DHCPv6.  Manual  However, manual key distribution runs counter to the
   goal of minimizing the configuration data needed at each host.

   [RFC3315] provides an additional mechanism for
   Consequently, there are no known deployments of this security
   mechanism.

   [RFC3315] provides an additional mechanism for preventing off-network
   timing attacks using the Reconfigure message: the Reconfigure Key
   authentication method.  However, this method protects only the
   Reconfigure message.  The key is transmitted in plaintext to the
   client in earlier exchanges and so this method is vulnerable to on-
   path active attacks.

   Anonymity Profile for DHCP Clients [RFC7844] explains how to generate
   DHCPv4 or DHCPv6 requests that minimize the disclosure of identifying
   information.  However, the anonymity profile limits the use of the
   certain options.  It also cannot anticipate new options that may
   contain private information is defined.  In addition, the current anonymity
   profile does not work in cases where the client wants to maintain
   anonymity from eavesdroppers but must identify itself to the DHCP
   server with which it intends to communicate.

   Privacy consideration for DHCPv6 [RFC7824] presents an analysis of
   the privacy issues associated with the use of DHCPv6 by Internet
   users.  No solutions are presented.

   Current DHCPv6 messages are still transmitted in cleartext and the
   privacy information within the DHCPv6 message is not protected from
   passive attack, such as pervasive monitoring.  The
   IETF has expressed strong agreement that pervasive monitoring is an
   attack that needs to be mitigated where possible in [RFC7258].

   In comparison,

   To better address the security mechanisms defined in problem of passive monitoring and to achieve
   authentication without requiring a symmetric key distribution
   solution for DHCP, this document
   provides for defines an asymmetric key
   authentication and encryption based on the public key
   certificates of the client and server.  The DHCPv6 authentication can
   protect DHCPv6 from mechanism.  This protects against both
   active attacks, such as spoofing attack.  And the
   DHCPv6 encryption defends against spoofing, and passive attacks, such as
   pervasive
   monitoring attack. monitoring.

5.  Secure DHCPv6 Overview

5.1.  Solution Overview

   This solution provides authentication and encryption mechanisms based
   on

   The following figure illustrated secure DHCPv6 procedure.  Briefly,
   this extension establishes the certificates of server's identity with an anonymous
   Information-Request exchange.  Once the server's identity has been
   established, the DHCPv6 client and server.  Before may either choose to communicate with the
   standard DHCPv6 configuration process,
   server or not.  Not communicating with an unknown server avoids
   revealing private information, but if there is no known server on a
   particular link, the Information-request and
   Reply messages are exchanged client will be unable to select the authenticated DHCPv6 communicate with a DHCP
   server.  After mutual authentication between

   If the DHCPv6 client and chooses to communicate with a server, it uses the following DHCPv6 configuration process is encrypted
   Encrypted-Query message to encapsulate its communications to
   avoid the privacy information disclosure.  We introduce DHCP
   server.  The server responds with Encrypted-Response messages.
   Normal DHCP messages are encapsulated in these two new
   DHCPv6 messages: Encrypted-Query message, Encrypted-Response message
   and four messages using
   the new DHCPv6 options: defined Encrypted-message option, Certificate
   option, Signature option, Timestamp option.  Based on  Besides the new Encrypted-
   message option, the Signature option is defined to verify the
   integrity of the DHCPv6 messages and options, the corresponding then authentication and encryption
   mechanisms are achieved.

   The following figure illustrates secure DHCPv6 procedure.  The DHCPv6 of client first sends Information-request message as per [RFC3315].
   and server.  The
   Information-request message Increasing number is used to request the servers for the
   servers' certificates information, without going through any address,
   prefix or non-security option assignment process.  The Information-
   request contains no DHCPv6 options except ORO option defined to avoid
   client's privacy information disclosure.  When receiving the detect replay
   attack.

           +-------------+                           +-------------+
           |DHCPv6 Client|                           |DHCPv6 Server|
           +-------------+                           +-------------+
                  |            Information-request message, the server sends the           |
                  |----------------------------------------->|
                  |           Option Request option          |
                  |                                          |
                  |                    Reply message that
   contains the server's                 |
                  |<-----------------------------------------|
                  |             Certificate option, option           |
                  |             Signature option, Timestamp option and             |
                  |          Increasing-number option        |
                  |         Server Identifier option.  Upon the receipt option         |
                  |                                          |
                  |            Encryption-Query              |
                  |----------------------------------------->|
                  |          Encrypted-message option        |
                  |          Server Identifier option        |
                  |                                          |
                  |            Encryption-Response           |
                  |<-----------------------------------------|
                  |          Encrypted-message option        |
                  |                                          |

                          Secure DHCPv6 Procedure

5.2.  New Components

   The new components of the Reply
   message, the DHCPv6 client verifies mechanism specified in this document are as
   follows:

   o  Servers and clients that use certificates first generate a public/
      private key pair and then obtain a certificate that signs the server's identity according
      public key.  The Certificate option is defined to carry the contained options in
      certificate of the Reply message.  If there are multiple
   authenticated DHCPv6 server certs, the client selects one
   authenticated DHCPv6 server for the following DHCPv6 configuration
   process.  If there are no authenticated DHCPv6 server cert or
   existing server certs fails authentication, sender.

   o  A signature generated using the client should retry a
   number of times.  In this way, it private key which is difficult for a rogue server to
   beat out a busy "real" server.  And then the client takes some other
   alternative action depending on its local policy.

   After the server's authentication, the first DHCPv6 message sent from used by the client
      receiver to verify the server, such as Solicit message, contains integrity of the
   client's Certificate information for client authentication.  The DHCPv6 client sends messages and then
      authentication of the Encrypted-Query message client/server.  The Signature option is
      defined to server, which
   carries carry the Encrypted-message signature.

   o  A Increasing-number that can be used to detect replayed packet.
      The Increasing-number option and is defined to carry a strictly-
      increasing serial number.  Timestamp is one of the Server Identifier
   option. possible
      implementation choice.

   o  The Encrypted-message option that contains the encrypted DHCPv6
      message.

   o  The Encrypted-Query message that is sent from the secure DHCPv6
      client to the secure DHCPv6 server.  When  The Encrypted-Query message
      MUST contain the DHCPv6 server
   receives Encrypted-message option.  In addition, the Encrypted-Query message,
      Server Identifier option MUST be contained if it decrypts is contained in
      the original DHCPv6 message.  The Encrypted-Query message using
   its private key.  If MUST NOT
      contain other options except the decrypted Server Identifier option and
      Encrypted-message option.

   o  The Encrypted-Response message contains the client's
   Certificate option, that is sent from the secure DHCPv6
      server verifies the client's identity
   according to the contained client certificate information.

   After the client's authentication, the server sends secure DHCPv6 client.  The Encrypted-Response
      message contains the Encrypted-message option.  The Encrypted-
      Response message to the client, which contains the Encrypted-message MUST NOT contain other options except Encrypted-
      message option.  The Encrypted-message option contains

5.3.  Support for Algorithm Agility

   In order to provide a means of addressing problems that may emerge
   with existing hash algorithms, signature algorithm and encryption
   algorithms in the encrypted DHCPv6
   message sent from server future, this document provides a mechanism to client, which
   support algotirhm agility.  The support for algorithm agility in this
   document is encrypted using mainly a algorithm notification mechanism between the
   client's public key.  If
   client and the message fails server.  The same client authentication,
   then and server SHOULD use the
   various algorithm in a single communication session.

   If the server sends does not support the corresponding error algorithm used by the client, the
   server SHOULD reply with an AlgorithmNotSupported status code
   (defined in Section 9.3) to the client.  During  Upon receiving this status
   code, the client MAY resend the message protected with the mandatory
   algorithm.

5.4.  Applicability

   In principle, secure DHCPv6 is applicable in any environment where
   physical security on the link is not assured and attacks on DHCPv6
   are a concern.  In practice, however, authenticated and encrypted
   DHCPv6 configuration process, will rely on some operational assumptions mainly
   regarding public key distribution and management.  In order to
   achieve the
   Timestamp option more wide use of secure DHCPv6, opportunistic security
   [RFC7435] can be contained applied for secure DHCPv6 deployment, which allows
   DHCPv6 encryption in the encrypted environments where support for authentication is
   not available.

   In some scenario where authentication is not available, secure DHCPv6 messages
   provides encryption without authentication to
   defend against replay attacks.

           +-------------+                           +-------------+
           |DHCPv6 Client|                           |DHCPv6 Server|
           +-------------+                           +-------------+
                  |            Information-request           |
                  |----------------------------------------->|
                  |           Option Request option          |
                  |                                          |
                  |                    Reply                 |
                  |<-----------------------------------------|
                  |             Certificate option           |
                  |             Signature option             |
                  |             Timestamp option             |
                  |         Server Identifier option         |
                  |                                          |
                  |            Encryption-Query              |
                  |----------------------------------------->|
                  |          Encrypted-message option        |
                  |          Server Identifier option        |
                  |                                          |
                  |            Encryption-Response           |
                  |<-----------------------------------------|
                  |          Encrypted-message option        |
                  |                                          |

                          Secure DHCPv6 Procedure

5.2.  New Components

   The new components of the mechanism specified in this document are as
   follows:

   o  Servers and clients that use certificates first generate a public/
      private key pair and then obtain a certificate that signs the
      public key.  The Certificate option is defined to carry the
      certificate of the sender.

   o  A signature generated using the private key which is used by the
      receiver to verify the integrity of the DHCPv6 messages and then
      authentication of the client/server.  Another option is defined to
      carry the signature.

   o  A timestamp that can be used to detect replayed packet.  The
      Timestamp option is defined to carry the current time of the
      client/server.  The secure DHCPv6 client/server need to meet some
      accuracy requirements and be synced to global time, while the
      timestamp checking mechanism allows a configurable time value for
      clock drift.  The real time provision is out of scope of this
      document.

   o  The Encrypted-message option that contains the encrypted DHCPv6
      message.

   o  The Encrypted-Query message that is sent from the secure DHCPv6
      client to the secure DHCPv6 server.  The Encrypted-Query message
      contains the Encrypted-message option and Server Identifier
      option.

   o  The Encrypted-Response message that is sent from the secure DHCPv6
      server to the secure DHCPv6 client.  The Encrypted-Response
      message contains the Encrypted-message option.

5.3.  Support for Algorithm Agility

   In order to provide a means of addressing problems that may emerge in
   the future with existing hash algorithms, as recommended in
   [RFC4270], this document provides a mechanism for negotiating the use
   of more secure hashes in the future.

   In addition to hash algorithm agility, this document also provides a
   mechanism for signature algorithm and encryption algorithm agility.

   The support for algorithm agility in this document is mainly a
   unilateral notification mechanism from sender to recipient.  A
   recipient MAY support various algorithms simultaneously among
   different senders, and the different senders in a same administrative
   domain may be allowed to use various algorithms simultaneously.  It
   is NOT RECOMMENDED that the same sender and recipient use various
   algorithms in a single communication session.

   If the server does not support the algorithm used by the client, the
   server SHOULD reply with an AlgorithmNotSupported status code
   (defined in Section 10.3) to the client.  Upon receiving this status
   code, the client MAY resend the message protected with the mandatory
   algorithm.

5.4.  Applicability

   In principle, Secure DHCPv6 is applicable in any environment where
   physical security on the link is not assured and attacks on achieve the wide
   deployment of secure DHCPv6.

   Secure DHCPv6
   are a concern.  In practice, however, it will rely on some
   operational assumptions mainly regarding public key distribution and
   management, until more lessons are learned provides authentication and more experiences are
   achieved. encryption based either on
   pre-sharing of authorized certificates, or else using trust-on-first-
   use.  The One feasible environment in an early deployment stage would
   be enterprise networks.  In such networks the security policy tends
   to be strict and it will be easier to manage client hosts.  One
   trivial deployment scenario is therefore to manually pre-configure
   client with the trusted servers' public key and manually register
   clients' public keys for the server.  It may also be possible to
   deploy an internal PKI to make this less reliant on manual
   operations, although it is currently subject to future study
   specifically how to integrate such a PKI into the DHCPv6 service for
   the network.

   Note that this deployment scenario based on manual operation is not
   different very much from the existing, shared-secret based
   authentication mechanisms defined in [RFC3315] in terms of
   operational costs.  However, Secure DHCPv6 is still securer than the
   shared-secret mechanism in that even if clients' keys stored for the
   server are stolen that does not mean an immediate threat as these are
   public keys.  In addition, if some kind of PKI is used with Secure
   DHCPv6, even if the initial installation of the certificates is done
   manually, it will help reduce operational costs of revocation in case
   a private key (especially that of the server) is compromised.

   It is believed that Secure DHCPv6 could be more widely applicable
   with integration of generic PKI so that it will be more easily
   deployed.  But such a deployment requires more general issues with
   PKI deployment be addressed, and it is currently unknown whether we
   can find practical deployment scenarios.  It is subject to future
   study and experiments, and out of scope of this document.

6.  DHCPv6 Client Behavior

   For the secure DHCPv6 client, a certificate is needed for client
   authentication.  The client is pre-configured with a certificate and
   its corresponding private key.  If the client is pre-configured with
   public key but not with a certificate, it can generate the self-
   signed certificate for client authentication.

   The secure DHCPv6 client sends Information-request message as per
   [RFC3315].  The Information-request message is used by the DHCPv6
   client to request the server's identity verification information
   without having addresses, prefixes or any non-security options
   assigned to it.  The Information-request message MUST NOT include any
   DHCPv6 options except ORO option to minimize client's privacy
   information leakage.  The Option Request option in the Information-
   request message MUST contain the option code of the Certificate
   option.

   When receiving the Reply messages from DHCPv6 servers, a secure
   DHCPv6 client discards any DHCPv6 messages that meet any of the
   following conditions:

   o  the Signature option is missing,

   o  multiple Signature options are present,

   o  the Certificate option is missing.

   And then the client first checks the support of the hash function,
   signature algorithm and encryption algorithm that the server used.
   If the check fails, the Reply message is dropped.  If all the
   algorithms are supported, the client then checks the authority of
   this server.  The client also uses the same algorithms in Behavior

   For the return
   messages. secure DHCPv6 client, a certificate is needed for client
   authentication.  The client validates the certificates through the is pre-configured
   local trusted certificates list or other methods.  A certificate that
   finds with a match in the local trust certificate list is treated as
   verified. and
   its corresponding private key.  If the client want to check server's certificate to see
   whether is pre-configured with
   public key but not with a certificate, it has been revoked, the OCSP stapling can be used. generate the self-
   signed certificate for client authentication.

   The secure DHCPv6 client sends Information-request message as per
   [RFC3315].  The Information-request message transaction-id is used as the identifier of the authenticated
   server's public key for encryption.  At this point, by the DHCPv6
   client has
   either recognized the certificate of to request the server, server's identity verification information
   without having addresses, prefixes or decided any non-security options
   assigned to drop
   the message. it.  The client Information-request message MUST now authenticate the server by verifying the
   signature and checking timestamp (see details in Section 9.1), if
   there is a Timestamp option.  The order of two procedures is left as
   an implementation decision.  It is RECOMMENDED NOT include any
   DHCPv6 options except ORO option to check timestamp
   first, because signature verification is much more computationally
   expensive. minimize client's privacy
   information leakage.  The Signature field verification MUST show that the signature has
   been calculated as specified Option Request option in Section 10.1.2.  Only the messages
   that get through both the signature verification and timestamp check
   (if there is a Timestamp option) are accepted.  Reply Information-
   request message that
   does not pass the above tests MUST be discarded.

   If there are multiple authenticated contain the option code of the Certificate
   option.

   When receiving the Reply messages from DHCPv6 servers, the a secure
   DHCPv6 client
   selects one discards any DHCPv6 server for messages that meet any of the
   following network parameters
   configuration.  The client can also choose other implementation
   method depending on the client's local policy if the defined protocol
   can also run normally.  For example, conditions:

   o  the client can try Signature option is missing,

   o  multiple
   transactions (each encrypted with different public key) at the "same"
   time.  If there Signature options are no authenticated DHCPv6 servers or existing
   servers failed authentication, present,

   o  the client should retry a number of
   times.  In this way, it Certificate option is difficult for the rogue server to beat out
   a busy "real" server. missing.

   And then the client takes some alternative
   action depending on its local policy, such as attempting to use an
   unsecured DHCPv6 server.  The client conducts first checks the server discovery
   process as per section 18.1.5 support of [RFC3315] to avoid the packet storm.

   Once hash algorithm,
   signature algorithm and encryption algorithm that the server has been authenticated, the DHCPv6 client sends used.
   If the
   Encrypted-Query message to check fails, the DHCPv6 server.  The Encrypted-Query Reply message contains the Encrypted-message option, which MUST be
   constructed as explained in Section 10.1.4, and Server Identifier
   option.  The Encrypted-message option contains is dropped.  If the DHCPv6 message
   that hash
   algorithm field is encrypted using zero, the selected server's public key. signature algorithm and hash algorithm
   are not separated.  The Server
   Identifier option corresponding hash algorithm is externally visible to avoid decryption cost by
   those unselected servers.

   For the encrypted DHCPv6 message sent from the DHCPv6 client to fixed
   according the
   DHCPv6 server, signature algorithm.  If all the first DHCPv6 message, such as Solicit message,
   MUST contain algorithms are
   supported, the Certificate option, Signature option and Timestamp
   option for client authentication. then checks the authority of this server.  The Certificate option MUST be
   constructed as explained in Section 10.1.1.  In addition, one and
   only one Signature option MUST be contained, which MUST be
   constructed as explained in Section 10.1.2.  One and only one
   Timestamp option SHOULD be contained, which MUST be constructed as
   explained
   client also uses the same algorithms in Section 10.1.3. the return messages.

   The Timestamp field SHOULD be set to client validates the current time, according to sender's real time clock.

   If certificates through the client has multiple pre-configured
   local trusted certificates with different public/private
   key pairs, list or other methods.  A certificate that
   finds a match in the local trust certificates list is treated as
   verified.  The message transaction-id is used as the identifier of
   the client's private authenticated server's public key for decryption.  In addition, the subsequent
   encrypted DHCPv6 further message can contain encryption.

   At this point, the Timestamp option to defend
   against replay attack.

   For client has either recognized the received Encrypted-Response message, certificate of
   the server, or decided to drop the message.

   The client extracts MUST now authenticate the
   Encrypted-message option server by verifying the
   signature and decrypts it using its private key checking increasing number, if there is a Increasing-
   number option.  The order of two procedures is left as an
   implementation decision.  It is RECOMMENDED to
   obtain check increasing
   number first, because signature verification is much more
   computationally expensive.  If the original DHCPv6 message.  Then decrypted message contains the
   Increasing-number option, the client checks it handles by comparing it with
   the message as
   per [RFC3315]. stored number on the client.  The client has one stable stored
   number for replay attack detection.  The initial value of the stable
   stored number is zero.  If the decrypted contained number is higher than the
   stored number, then the DHCPv6 message contains passes the
   Timestamp option, increasing-number
   check and the DHCPv6 client checks value of the timestamp according to stored number is changed into the rule defined in Section 9.1.  The DHCPv6 message, which fails value of
   the
   timestamp check, MUST be discarded. Increasing-number option.  If contained number is lower than the client fails to get the
   proper parameters from
   stored number on the chosen server, it sends the Encrypted-
   Query message to another authenticated server for parameters
   configuration until MUST drop the client obtains DHCPv6 message.

   The Signature field verification MUST show that the proper parameters.

   When signature has
   been calculated as specified in Section 9.1.2.  Only the client receives messages
   that get through both the signature verification and increasing
   number check (if there is a Increasing-number option) are accepted.
   Reply message with an error status code,
   the error status code indicates the failure reason on the server
   side.  According to that does not pass the received status code, above tests MUST be discarded.

   If there are multiple authenticated DHCPv6 certs, the client MAY take
   follow-up action:

   o  Upon receiving an AlgorithmNotSupported error status code, selects
   one DHCPv6 cert for the following network parameters configuration.
   The selected DHCPv6 cert may corresponds to multiple DHCPv6 servers.
   The client SHOULD resend can also choose other implementation method depending on
   the message protected with one of client's local policy if the
      mandatory algorithms.

   o  Upon receiving an AuthenticationFail error status code, defined protocol can also run
   normally.  For example, the client
      is not able to build up the secure communication can try multiple transactions
   (each encrypted with different public key) at the server.
      However, "same" time.

   If there may be other are no authenticated DHCPv6 servers available that
      successfully complete authentication. certs or existing servers fail
   authentication, the client should retry a number of times.  The
   client MAY use conducts the
      AuthenticationFail server discovery process as a hint and switch per section 18.1.5 of
   [RFC3315] to other certificate if avoid the packet storm.  In this way, it
      has another one; but otherwise treat is difficult
   for the message containing rogue server to beat out a busy "real" server.  And then the
      status code
   client takes some alternative action depending on its local policy,
   such as if it had attempting to use an unsecured DHCPv6 server.  In some
   scenario, such as laptops in coffee room, clients are always not been received.  But it SHOULD NOT
      retry with pre-
   configured the same certificate.  However, sufficient information for server authentication and
   can accept DHCPv6 encryption without DHCPv6 authentication.  In such
   scenario, if some DHCPv6 servers fail authentication because the client decides
      to retransmit using the same
   server's certificate after receiving
      AuthenticationFail, it MUST NOT retransmit immediately and MUST
      follow normal retransmission routines defined is not in [RFC3315].

   o  Upon receiving a DecryptionFail error status code, the trusted certs' list, and then the
   client MAY
      resend selects one DHCPv6 server and record the message following normal retransmission routines
      defined in [RFC3315].

   o  Upon receiving a TimestampFail error status code, server's public key
   for the future encrypted DHCPv6 configuration process.

   Once the server has been authenticated, the DHCPv6 client MAY
      resend sends the
   Encrypted-Query message with an adjusted timestamp according to the
      returned clock from the DHCPv6 server.  The client SHOULD NOT
      change its own clock, but only compute an offset for Encrypted-Query
   message contains the
      communication session.

   o  Upon receiving a SignatureFail error status code, Encrypted-message option, which MUST be
   constructed as explained in Section 9.1.4.  In addition, the client MAY
      resend Server
   Identifier option MUST be contained if it is in the original message following normal retransmission routines
      defined in [RFC3315].

7.  DHCPv6 Server Behavior

   For
   (i.e.  Request, Renew, Decline, Release) to avoid the extra
   decryption for the secure DHCPv6 server, a certificate is needed servers not for server
   authentication. it.  The server is pre-configured with a certificate and
   its corresponding private key.  If Encrypted-message
   option contains the server DHCPv6 message that is pre-configured with encrypted using the public
   key but not with a certificate, it can generate the self-
   signed certificate for server authentication.

   When contained in the selected cert.  The Server Identifier option is
   externally visible to avoid decryption cost by those unselected
   servers.  The Encrypted-Query message MUST NOT contain other DHCPv6 server receives
   option except the Information-request message Server Identifier option and Encrypted-Message
   option.

   If the contained Option Request option identifies received Reply message indicates the request is for of the
   server client's
   certificate information, it replies with a Reply information through the Option Request option, the first
   DHCPv6 message sent from the client to the client.  The Reply message server, such as Solicit
   message, MUST contain the requested Certificate option, which Signature option and
   Increasing-number option for client authentication.  The encryption
   text SHOULD be formatted as explain in [RFC5652].  The Certificate
   option MUST be constructed as explained in Section 10.1.1, and
   Server Identifier option. 9.1.1.  In
   addition, the Reply message MUST
   contain one and only one Signature option, option MUST be contained, which
   MUST be constructed as explained in Section 10.1.2.  Besides, the Reply message SHOULD
   contain one 9.1.2.  One and only one Timestamp option,
   Increasing-number option SHOULD be contained, which MUST be
   constructed as explained in Section 10.1.3.  The Timestamp field SHOULD be set to 9.1.3.

   If the current time, according to server's real time clock.

   Upon client has multiple certificates with different public/private
   key pairs, the receipt message transaction-id is used as the identifier of Encrypted-Query
   the client's private key for decryption.  In addition, the subsequent
   encrypted DHCPv6 message can contain the Increasing-number option to
   defend against replay attack.

   For the received Encrypted-Response message, the server checks client MUST drop the
   Encrypted-Response message if other DHCPv6 option except Encrypted-
   message option is contained.  Then, the
   Server Identifier option.  It decrypts client extracts the
   Encrypted-message option and decrypts it using its private key if it is to
   obtain the target server.  The original DHCPv6 server
   drops message.  Then it handles the message that is not for it, thus not paying cost to decrypt
   messages not for it. as
   per [RFC3315].  If the decrypted DHCPv6 message is a Solicit/Information-request message, contains the
   Increasing-number option, the secure DHCPv6 server discards client MUST drop the received DHCPv6
   message that meets any
   of the following conditions:

   o with the Signature option is missing,

   o  multiple Signature options are present,

   o lower number.  If the Certificate option is missing.

   In such failure, client fails to get the server replies with an UnspecFail (value 1,
   [RFC3315]) error status code.

   The server SHOULD first check proper
   parameters from the support of chosen server, it sends the hash function,
   signature algorithm, encryption algorithm that Encrypted-Query
   message to another authenticated server for parameters configuration
   until the client used.  If obtains the check fails, proper parameters.

   When the server SHOULD reply client receives a Reply message with an
   AlgorithmNotSupported error status code, defined in Section 10.3,
   back to the client.  If all
   the algorithms are supported, error status code indicates the server
   then checks failure reason on the authority of this client.

   The server validates
   side.  According to the client's public key through received status code, the local pre-
   configured trusted public keys list.  A public key that finds a match
   in client MAY take
   follow-up action:

   o  Upon receiving an AlgorithmNotSupported error status code, the local trust public keys list is treated as verified.  The
   message that fails public key validation MUST be dropped.  In such
   failure,
      client SHOULD resend the DHCPv6 server replies message protected with one of the
      mandatory algorithms.

   o  Upon receiving an AuthenticationFail error status code, defined in Section 10.3, back to the client.  At this
   point, client
      is not able to build up the server has either recognized secure communication with the authentication of server.
      However, there may be other DHCPv6 servers available that
      successfully complete authentication.  The client MAY use the
   client, or decided
      AuthenticationFail as a hint and switch to drop the message.

   If other certificate if it
      has another one; but otherwise treat the decrypted message contains containing the Timestamp option,
      status code as if it had not been received.  But it SHOULD NOT
      retry with the server
   checks same certificate.  However, if the timestamp according client decides
      to retransmit using the rule same certificate after receiving
      AuthenticationFail, it MUST NOT retransmit immediately and MUST
      follow normal retransmission routines defined in Section 9.1.
   If the timestamp check fails, [RFC3315].

   o  Upon receiving a TimestampFail DecryptionFail error status code,
   defined in Section 10.3, should be sent back to the client.
   Depending on server's local policy, the message without a Timestamp
   option client MAY be acceptable or rejected.  If
      resend the server rejects such a
   message, message following normal retransmission routines
      defined in [RFC3315].

   o  Upon receiving a TimestampFail IncreasingnumFail error status code should be sent back to code, the client
      MAY resend the
   client.  The Reply message that carries with an adjusted Increasing-number option
      according to the TimestampFail returned clock from the DHCPv6 server.

   o  Upon receiving a SignatureFail error status code carries a Timestamp option, which indicates the server's
   clock for code, the client to use.

   If the server does not send the Timestamp option, MAY
      resend the client ignores message following normal retransmission routines
      defined in [RFC3315].

7.  DHCPv6 Server Behavior

   For the timestamp check secure DHCPv6 server, a certificate is needed for server
   authentication.  The server is pre-configured with a certificate and verifies the signature.
   its corresponding private key.  If there the server is pre-configured with
   public key but not with a
   timestamp option, certificate, it can generate the self-
   signed certificate for server MUST now authenticate authentication.

   When the client by
   verifying DHCPv6 server receives the signature Information-request message and checking timestamp (see details in
   Section 9.1).  The order of two procedures is left as an
   implementation decision.  It is RECOMMENDED to check timestamp first,
   because signature verification is much more computationally
   expensive.  Depending on server's local policy,
   the message without a
   Timestamp contained Option Request option MAY be acceptable or rejected.  If identifies the request is for the
   server
   rejects such a message, certificate information, it replies with a TimestampFail error status code, defined in
   Section 10.3, should be sent back Reply message to
   the client.  The reply Reply message
   that carries MUST contain the TimestampFail error status code SHOULD carry a
   Timestamp requested Certificate
   option, which indicates the server's clock for the client
   to use.

   The Signature field verification MUST show that the signature has
   been calculated be constructed as specified explained in Section 10.1.2.  Only the clients
   that get through both the signature verification 9.1.1, and timestamp check
   (if there is a Timestamp option) are accepted as authenticated
   clients
   Server Identifier option.  In addition, the Reply message MUST
   contain one and continue to only one Signature option, which MUST be handled their message constructed
   as defined explained in
   [RFC3315].  Clients that do not pass Section 9.1.2.  Besides, the above tests MUST be treated
   as unauthenticated clients.  The DHCPv6 server Reply message SHOULD reply a
   SignatureFail error status code, defined
   contain one and only one Increasing-number option, which MUST be
   constructed as explained in Section 10.3, for 9.1.3.  In addition, if client
   authentication is needed, then the
   signature verification failure; or a TimestampFail error status code,
   defined ORO option in Section 10.3, for the timestamp check failure, back Reply message
   contains the code of the certificate option to indicate the
   client.

   Once request
   of the client has been authenticated, certificate information.

   Upon the receipt of Encrypted-Query message, the DHCPv6 server sends MUST drop the
   Encrypted-response
   message to if the other DHCPv6 client.  The Encrypted-
   response option except Server Identifier option
   and Encrypted-message option is contained.  Then, the server checks
   the Server Identifier option if the Encrypted-Query message contains
   the Encrypted-message option, which MUST be
   constructed as explained in Section 10.1.4. Server Identifier option.  The DHCPv6 server drops the message
   that is not for it, thus not paying cost to decrypt messages not for
   it.  It decrypts the Encrypted-message option using its private key
   if it is the target server.

   If the secure DHPCv6 need client authentication and decrypted message
   is a Solicit/Information-request message which contains the encrypted
   information for client authentication, the secure DHCPv6 server
   discards the received message that is encrypted using meets any of the authenticated client's public key.  To provide following
   conditions:

   o  the replay
   protection, Signature option is missing,

   o  multiple Signature options are present,

   o  the Timestamp Certificate option can be contained in is missing.

   In such failure, the encrypted
   DHCPv6 message.

8.  Relay Agent Behavior

   When a DHCPv6 relay agent receives server replies with an Encrypted-query or Encrypted-
   response message, it may not recognize this message. UnspecFail (value 1,
   [RFC3315]) error status code.

   The unknown
   messages MUST be forwarded as described in [RFC7283].

   When a DHCPv6 relay agent recognizes the Encrypted-query and
   Encrypted-response messages, it forwards server SHOULD first check the message according to
   section 20 support of [RFC3315].  There is nothing more the relay agents have
   to do, it neither needs to verify hash function,
   signature algorithm, encryption algorithm that the messages from client or server,
   nor add any secure DHCPv6 options.  Actually, by definition in this
   document, relay agents MUST NOT add any secure DHCPv6 options.

   Relay-forward and Relay-reply messages MUST NOT contain any
   additional Certificate option or Timestamp option, aside from those
   present in used.  If
   the innermost encapsulated messages from hash algorithm field is zero, then the client or
   server.

   Relay agent signature algorithm and
   hash algorithm are not separated.  The corresponding hash algorithm
   is RECOMMENDED to cache server announcements to form fixed according the
   list of signature algorithm.  If the check fails, the available DHCPv6
   server certs. SHOULD reply with an AlgorithmNotSupported error status code,
   defined in Section 9.3, back to the client.  If all the relay agent
   receives algorithms
   are supported, the Information-request message, server then it replies with a list checks the authority of server certs available locally.  In this way, client.

   The server validates the client can be
   confident of a quick response, and therefore treat client's certificate through the lack of local pre-
   configured trusted certificates list.  A certificate that finds a
   quick response
   match in the local trust certificates list is treated as an indication verified.
   The message that no authenticated DHCP servers
   exist.

9.  Processing Rules

9.1.  Timestamp Check fails authentication validation MUST be dropped.  In order
   such failure, the DHCPv6 server replies with an AuthenticationFail
   error status code, defined in Section 9.3, back to check the Timestamp client.  At
   this point, the server has either recognized the authentication of
   the client, or decided to drop the message.

   If the decrypted message contains the Increasing-number option, defined in Section 10.1.3,
   recipients SHOULD be configured the
   server checks it by comparing it with an allowed timestamp Delta
   value, a "fuzz factor" the stored number on the
   server.  The server has one stable stored number for comparisons, and an allowed clock drift
   parameter. replay attack
   detection.  The recommended default initial value for of the allowed Delta stable stored number is
   300 seconds (5 minutes); for fuzz factor 1 second; and for clock
   drift, 0.01 second.

   Note: zero.
   If the Timestamp mechanism contained number is based on higher than the assumption that
   communication peers have roughly synchronized clocks, within certain
   allowed clock drift.  So, an accurate clock stored number, the value
   of the stored number is not necessary. changed into the value of the Increasing-
   number option.  If one
   has a clock too far from contained number is lower than the current time, stored number
   on the timestamp mechanism
   would not work.

   To facilitate timestamp checking, each recipient SHOULD store server, the server MUST drop the
   following information for each sender, from which at least one
   accepted secure DHCPv6 message is successfully verified (for
   timestamp check and signature verification):

   o a
   IncreasingnumFail error status code, defined in Section 9.3, should
   be sent back to the client.  Depending on server's local policy, the
   message without a Increasing-number option MAY be acceptable or
   rejected.  If the server rejects such a message, a IncreasingnumFail
   error status code should be sent back to the client.  The receive time of Reply
   message that carries the last received and accepted DHCPv6 message.
      This is called RDlast.

   o IncreasingnumFail error status code carries
   a Increasing-number option, which indicates the server's storage
   number for the client to use.

   The timestamp Signature field verification MUST show that the signature has
   been calculated as specified in Section 9.1.2.  Only the last received clients that
   get through both the signature verification and accepted DHCPv6 message.
      This is called TSlast.

   A verified (for timestamp increasing number
   check (if there is a Increasing-number option) are accepted as
   authenticated clients and signature verification) secure
   DHCPv6 message initiates the update of the above variables continue to be handled their message as
   defined in [RFC3315].  Clients that do not pass the
   recipient's record.

   Recipients above tests MUST check the Timestamp field
   be treated as follows:

   o  When a message is received from unauthenticated clients.  The DHCPv6 server SHOULD
   reply a new peer (i.e., one that is not
      stored SignatureFail error status code, defined in Section 9.3, for
   the cache), signature verification failure.

   Once the received timestamp, TSnew, is checked,
      and client has been authenticated, the message is accepted if DHCPv6 server sends the timestamp is recent enough
   Encrypted-response message to the reception time of the packet, RDnew:

         -Delta < (RDnew - TSnew) < +Delta

      After the signature verification also succeeds, DHCPv6 client.  The Encrypted-
   response message MUST only contain the RDnew and
      TSnew values Encrypted-message option,
   which MUST be constructed as explained in Section 9.1.4.  The
   encryption text SHOULD be stored formatted as explain in [RFC5652].  The
   Encrypted-message option contains the cache as RDlast and TSlast.

   o  When a encrypted DHCPv6 message is received from a known peer (i.e., one that
      already has an entry in
   is encrypted using the authenticated client's public key.  To provide
   the cache), replay protection, the timestamp is checked
      against Increasing-number option can be contained
   in the previously received Secure encrypted DHCPv6 message:

         TSnew + fuzz > TSlast + (RDnew - RDlast) x (1 - drift) - fuzz

      If this inequality does not hold message.

8.  Relay Agent Behavior

   When a DHCPv6 relay agent receives an Encrypted-query or RDnew < RDlast, the recipient
      SHOULD silently discard the Encrypted-
   response message, it may not recognize this message.  If, on the other hand, the
      inequality holds,  The unknown
   messages MUST be forwarded as described in [RFC7283].

   When a DHCPv6 relay agent recognizes the recipient SHOULD process Encrypted-query and
   Encrypted-response messages, it forwards the message.

      Moreover, if message according to
   section 20 of [RFC3315].  There is nothing more the above inequality holds and TSnew > TSlast, relay agents have
   to do, it neither needs to verify the
      recipient SHOULD update RDlast messages from client or server,
   nor add any secure DHCPv6 options.  Actually, by definition in this
   document, relay agents MUST NOT add any secure DHCPv6 options.

   Relay-forward and TSlast after the signature
      verification also successes.  Otherwise, the recipient Relay-reply messages MUST NOT
      update RDlast contain any
   additional Certificate option or TSlast.

   An implementation MAY use some mechanism such as a timestamp cache Increasing-number option, aside from
   those present in the innermost encapsulated messages from the client
   or server.

   Relay agent is RECOMMENDED to
   strengthen resistance cache server announcements to replay attacks.  When there is a very large
   number form the
   list of nodes on the same link, or when a cache filling attack is
   in progress, it is possible that available DHCPv6 server certs.  If the cache holding relay agent
   receives the most recent
   timestamp per sender will become full. Information-request message, then it replies with a list
   of server certs available locally.  In this case, way, the node MUST
   remove some entries from client can be
   confident of a quick response, and therefore treat the cache or refuse some new requested
   entries.  The specific policy as to which entries are preferred over
   others is left lack of a
   quick response as an implementation decision.

   An implementation MAY statefully record the latest timestamps from
   senders.  In such implementation, the timestamps MUST be strictly
   monotonously increasing.  This is reasonable given indication that DHCPv6
   messages are rarely misordered.

10. no authenticated DHCP servers
   exist.

9.  Extensions for Secure DHCPv6

   This section describes the extensions to DHCPv6.  Four new DHCPv6
   options, two new DHCPv6 messages and five new status codes are
   defined.

10.1.

9.1.  New DHCPv6 Options

10.1.1.

9.1.1.  Certificate Option

   The Certificate option carries the certificate of the client/server.
   The format of the Certificate option is described as follows:

    0                   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_CERTIFICATE       |         option-len            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     EA-id     |                                               |
   +-+-+-+-+-+-+-+-+                                               .
   .                  Certificate (variable length)                .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code    OPTION_CERTIFICATE (TBA1).

   option-len     1 + Length of certificate in octets.

   EA-id          Encryption Algorithm id. The encryption algorithm
                  is used for the encrypted DHCPv6 configuration
                  process. This design is adopted in order to provide
                  encryption algorithm agility. The value is from the
                  Encryption Algorithm for Secure DHCPv6 registry in
                  IANA. A registry of the initial assigned values
                  is defined in Section 12.

   Certificate    A variable-length field containing certificate. The
                  encoding of certificate and certificate data MUST
                  be in format as defined in Section 3.6, [RFC7296].
                  The support of X.509 certificate is mandatory.

10.1.2.

9.1.2.  Signature option

   The Signature option allows a signature that is signed by the private
   key to be attached to a DHCPv6 message.  The Signature option could
   be in any place within the DHCPv6 message while it is logically
   created after the entire DHCPv6 header and options.  It protects the
   entire DHCPv6 header and options, including itself.  The format of
   the Signature option is described as follows:

    0                   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     OPTION_SIGNATURE          |        option-len             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     HA-id     |     SA-id     |     HA-id     |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   .                    Signature (variable length)                .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   option-code    OPTION_SIGNATURE (TBA2).

   option-len     2 + Length of Signature field in octets.

   HA-id          Hash

   SA-id          Signature Algorithm id. The hash signature algorithm is
                  used for computing the signature result. This
                  design is adopted in order to provide hash signature
                  algorithm agility. The value is from the Hash Signature
                  Algorithm for Secure DHCPv6 registry in IANA. The
                  support of SHA-256 RSASSA-PKCS1-v1_5 is mandatory. A
                  registry of the initial assigned values is defined
                  in Section 12.

   SA-id          Signature

   HA-id          Hash Algorithm id. The signature hash algorithm is used for
                  computing the signature result. This design is
                  adopted in order to provide signature hash algorithm agility.
                  The value is from the Signature Hash Algorithm for Secure
                  DHCPv6 registry in IANA. The support of RSASSA-PKCS1-v1_5 SHA-256 is
                  mandatory. A registry of the initial assigned values
                  is defined in Section 12. If the signature algorithm
                  and hash algorithm cannot be separated, the HA-id
                  field is zero. The hash algorithm is decided by the
                  corresponding signature algorithm.

   Signature      A variable-length field containing a digital
                  signature. The signature value is computed with
                  the hash algorithm and the signature algorithm,
                  as described in HA-id and SA-id. The signature
                  constructed by using the sender's private key
                  protects the following sequence of octets:

                  1. The DHCPv6 message header.

                  2. All DHCPv6 options including the Signature
                  option (fill the Signature field with zeroes)
                  except for the Authentication Option. zeroes).

                  The Signature field MUST be padded, with all 0, to
                  the next octet boundary if its size is not a
                  multiple of 8 bits. The padding length depends on
                  the signature algorithm, which is indicated in the
                  SA-id field.

   Note: If Secure DHCPv6 is used, the DHCPv6 message is encrypted in a
   way that the authentication mechanism defined in RFC3315 does not
   understand.  So the Authentication option SHOULD NOT be used if
   Secure DHCPv6 is applied.

10.1.3.  Timestamp

9.1.3.  Increasing-number Option

   The Timestamp Increasing-number option carries the current time number which is higher than
   the local stored number on the sender. client/server.  It adds the anti-replay anti-
   replay protection to the DHCPv6 messages.  It is optional.

 0                   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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     OPTION_TIMESTAMP   OPTION_INCREASINGNUM        |        option-len             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                     Timestamp (64-bit)                        |
   |                                                               |
   |                  InreasingNum (32-bit)                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

option-code    OPTION_TIMESTAMP    OPTION_INCREASINGNUM (TBA3).

   option-len     8, in octets.

   Timestamp      The current time of day (SeND-format timestamp
                  in UTC (Coordinated Universal Time). It can reduce

option-len     4, in octets.

IncreasingNum  A number which is higher than the local stored number on the
               client/server for the danger of replay attacks. The timestamp data MUST
                  be in format as defined in Section 5.3.1, [RFC3971].

10.1.4. attack detection.

9.1.4.  Encrypted-message Option

   The Encrypted-message option carries the encrypted DHCPv6 message
   with the recipient's public key.

   The format of the Encrypted-message option is:

      0                   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          option-code          |           option-len          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                  encrypted DHCPv6 message                     .
     .                       (variable)                              .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: Encrypted-message Option Format

   option-code  OPTION_ENCRYPTED_MSG (TBA4).

   option-len  Length of the encrypted DHCPv6 message.

   encrypted DHCPv6 message  A variable length field containing the
      encrypted DHCPv6 message sent by the client or the server.  In
      Encrypted-Query message, it contains encrypted DHCPv6 message sent
      by a client.  In Encrypted-response message, it contains encrypted
      DHCPv6 message sent by a server.

10.2.

9.2.  New DHCPv6 Messages

   Two new DHCPv6 messages are defined to achieve the DHCPv6 encryption:
   Encrypted-Query and Encrypted-Response.  Both the DHCPv6 messages
   defined in this document share the following format:

      0                   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    msg-type   |               transaction-id                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                             options                           .
     .                           (variable)                          .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 2: The format of Encrypted-Query and Encrypted-Response
                                 Messages

   msg-type        Identifier of the message type.  It can be either
                   Encrypted-Query (TBA5) or DHCPv6-Response (TBA6).

   transaction-id  The transaction ID for this message exchange.

   options         The Encrypted-Query message MUST only contain the
                   Server Identifier option and or Encrypted-message option.
                   The Encrypted-Response message MUST only contain the
                   Encrypted-message option.

10.3.

9.3.  Status Codes

   The following new status codes, see Section 5.4 of [RFC3315] are
   defined.

   o  AlgorithmNotSupported (TBD7): indicates that the DHCPv6 server
      does not support algorithms that sender used.

   o  AuthenticationFail (TBD8): indicates that the message from the
      DHCPv6 client fails authentication check.

   o  TimestampFail  IncreasingnumFail (TBD9): indicates the message from DHCPv6 client
      fails the timestamp increasing number check.

   o  SignatureFail (TBD10): indicates the message from DHCPv6 client
      fails the signature check.

   o  DecryptionFail (TBD11): indicates the message from DHCPv6 client
      fails the DHCPv6 message decryption.

11.

10.  Security Considerations

   This document provides the authentication and encryption mechanisms
   for DHCPv6.

   [RFC6273] has analyzed possible threats to the hash algorithms used
   in SEND.  Since Secure DHCPv6 defined in this document uses the same
   hash algorithms in similar way to SEND, analysis results could be
   applied as well: current attacks on hash functions do not constitute
   any practical threat to the digital signatures used in the signature
   algorithm in Secure DHCPv6.

   A server, whose local policy accepts messages without a Timestamp Increasing-
   number option, may have to face the risk of replay attacks.

   A window of vulnerability for replay attacks exists until the
   timestamp expires.  Secure DHCPv6 nodes are protected against replay
   attacks as long as they cache the state created by the message
   containing the timestamp.  The cached state allows the node to
   protect itself against replayed messages.  However, once the node
   flushes the state for whatever reason, an attacker can re-create the
   state by replaying an old message while the timestamp is still valid.
   In addition, the effectiveness of timestamps is largely dependent
   upon the accuracy of synchronization between communicating nodes.
   However, how the two communicating nodes can be synchronized is out
   of scope of this work.

   Attacks against time synchronization protocols such as NTP [RFC5905]
   may cause Secure DHCPv6 nodes to have an incorrect timestamp value.
   This can be used to launch replay attacks, even outside the normal
   window of vulnerability.  To protect against these attacks, it is
   recommended that Secure DHCPv6 nodes keep independently maintained
   clocks or apply suitable security measures for the time
   synchronization protocols.

   There are some mandatory algorithm for encryption algorithm in this
   document.  It may be at some point that the mandatory algorithm is no
   longer safe to use.

   If the client tries more than one cert for client authentication, the
   server can easily get a client that implements this to enumerate its
   entire cert list and probably learn a lot about a client that way.

12.

11.  IANA Considerations

   This document defines four new DHCPv6 [RFC3315] options.  The IANA is
   requested to assign values for these four options from the DHCPv6
   Option Codes table of the DHCPv6 Parameters registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters.  The four options
   are:

      The Certificate Option (TBA1), described in Section 10.1.1. 9.1.1.

      The Signature Option (TBA2), described in Section 10.1.2. 9.1.2.

      The Timestamp Increasing-number Option (TBA3),described in Section 10.1.3. 9.1.3.

      The Encrypted-message Option (TBA4), described in Section 10.1.4. 9.1.4.

   The IANA is also requested to assign value for these two messages
   from the DHCPv6 Message Types table of the DHCPv6 Parameters registry
   maintained in http://www.iana.org/assignments/dhcpv6-parameters.  The
   two messages are:

      The Encrypted-Query Message (TBA5), described in Section 10.2. 9.2.

      The Encrypted-Response Message (TBA6), described in Section 10.2. 9.2.

   The IANA is also requested to add three new registry tables to the
   DHCPv6 Parameters registry maintained in
   http://www.iana.org/assignments/dhcpv6-parameters.  The three tables
   are the Hash Algorithm for Secure DHCPv6 table, the Signature
   Algorithm for Secure DHCPv6 table and the Encryption Algorithm for
   Secure DHCPv6 table.

   Initial values for these registries are given below.  Future
   assignments are to be made through Standards Action [RFC5226].
   Assignments for each registry consist of a name, a value and a RFC
   number where the registry is defined.

   Hash Algorithm for Secure DHCPv6.  The values in this table are 8-bit
   unsigned integers.  The following initial values are assigned for
   Hash Algorithm for Secure DHCPv6 in this document:

             Name        |  Value  |  RFCs
      -------------------+---------+--------------
         SigAlg-Combined |   ox00  | this document
            SHA-256      |   0x01  | this document
            SHA-512      |   0x02  | this document

   Signature Algorithm for Secure DHCPv6.  The values in this table are
   8-bit unsigned integers.  The following initial values are assigned
   for Signature Algorithm for Secure DHCPv6 in this document:

             Name        |  Value  |  RFCs
      -------------------+---------+--------------
       RSASSA-PKCS1-v1_5 |   0x01  | this document

   Encryption algorithm for Secure DHCPv6.  The values in this table are
   8-bit unsigned integers.  The following initial values are assigned
   for encryption algorithm for Secure DHCPv6 in this document:

             Name        |  Value  |  RFCs
      -------------------+---------+--------------
              RSA        |    0   0x01  | this document

   IANA is requested to assign the following new DHCPv6 Status Codes,
   defined in Section 10.3, 9.3, in the DHCPv6 Parameters registry maintained
   in http://www.iana.org/assignments/dhcpv6-parameters:

         Code  |           Name        |   Reference
      ---------+-----------------------+--------------
         TBD7  | AlgorithmNotSupported | this document
         TBD8  |   AuthenticationFail  | this document
         TBD9  |     TimestampFail  IncreasingnumFail    | this document
         TBD10 |     SignatureFail     | this document
         TBD11 |    DecryptionFail     | this document

13.

12.  Acknowledgements

   The authors would like to thank Tomek Mrugalski, Bernie Volz,
   Jianping Wu, Randy Bush, Yiu Lee, Sean Shen, Ralph Droms, Jari Arkko,
   Sean Turner, Stephen Farrell, Christian Huitema, Stephen Kent, Thomas
   Huth, David Schumacher, Francis Dupont, Gang Chen, Suresh Krishnan,
   Fred Templin, Robert Elz, Nico Williams, Erik Kline, Alan DeKok,
   Bernard Aboba, Sam Hartman, Qi Sun, Zilong Liu and other members of
   the IETF DHC working group for their valuable comments.

   This document was produced using the xml2rfc tool [RFC2629].

14.  Change log [RFC Editor: Please remove] their valuable comments.

   This document was produced using the xml2rfc tool [RFC2629].

13.  Change log [RFC Editor: Please remove]

   draft-ietf-dhc-sedhcpv6-13: Change the Timestamp option into
   Increasing-number option and the corresponding check method; Delete
   the OCSP stampling part for the certificate check; Add the scenario
   where the hash and signature algorithms cannot be separated; Add the
   comparison with RFC7824 and RFC7844; Add the encryption text format
   and reference of RFC5652.  Add the consideration of scenario where
   multiple DHCPv6 servers share one common DHCPv6 server.  Add the
   statement that Encrypted-Query and Encrypted-Response messages can
   only contain certain options: Server Identifier option and Encrypted-
   message option.  Add opportunistic security for deployment
   consideration.  Besides authentication+encyrption mode, encryption-
   only mode is added.

   draft-ietf-dhc-sedhcpv6-12: Add the Signature option and timestamp
   option during server/client authentication process.  Add the hash
   function and signature algorithm.  Add the requirement: The
   Information-request message cannot contain any other options except
   ORO option.  Modify the use of "SHOULD"; Delete the reference of
   RFC5280 and modify the method of client/server cert verification; Add
   the relay agent cache function for the quick response when there is
   no authenticated server.  2016-4-24.

   draft-ietf-dhc-sedhcpv6-11: Delete the Signature option, because the
   encrypted DHCPv6 message and the Information-request message (only
   contain the Certificate option) don't need the Signature option for
   message integrity check; Rewrite the "Applicability" section; Add the
   encryption algorithm negotiation process; To support the encryption
   algorithm negotiation, the Certificate option contains the EA-
   id(encryption algorithm identifier) field; Reserve the Timestamp
   option to defend against the replay attacks for encrypted DHCPv6
   configuration process; Modify the client behavior when there is no
   authenticated DHCPv6 server; Add the DecryptionFail error code.
   2016-3-9.

   draft-ietf-dhc-sedhcpv6-10: merge DHCPv6 authentication and DHCPv6
   encryption.  The public key option is removed, because the device can
   generate the self-signed certificate if it is pre-configured the
   public key not the certificate. 2015-12-10.

   draft-ietf-dhc-sedhcpv6-09: change some texts about the deployment
   part.2015-12-10.

   draft-ietf-dhc-sedhcpv6-08: clarified what the client and the server
   should do if it receives a message using unsupported algorithm;
   refined the error code treatment regarding to AuthenticationFail and
   TimestampFail; added consideration on how to reduce the DoS attack
   when using TOFU; other general editorial cleanups. 2015-06-10.

   draft-ietf-dhc-sedhcpv6-07: removed the deployment consideration
   section; instead, described more straightforward use cases with TOFU
   in the overview section, and clarified how the public keys would be
   stored at the recipient when TOFU is used.  The overview section also
   clarified the integration of PKI or other similar infrastructure is
   an open issue.  2015-03-23.

   draft-ietf-dhc-sedhcpv6-06: remove the limitation that only clients
   use PKI- certificates and only servers use public keys.  The new text
   would allow clients use public keys and servers use PKI-certificates.
   2015-02-18.

   draft-ietf-dhc-sedhcpv6-05: addressed comments from mail list that
   responsed to the second WGLC. 2014-12-08.

   draft-ietf-dhc-sedhcpv6-04: addressed comments from mail list.
   Making timestamp an independent and optional option.  Reduce the
   serverside authentication to base on only client's certificate.
   Reduce the clientside authentication to only Leaf of Faith base on
   server's public key. 2014-09-26.

   draft-ietf-dhc-sedhcpv6-03: addressed comments from WGLC.  Added a
   new section "Deployment Consideration".  Corrected the Public Key
   Field in the Public Key Option.  Added consideration for large DHCPv6
   message transmission.  Added TimestampFail error code.  Refined the
   retransmission rules on clients. 2014-06-18.

   draft-ietf-dhc-sedhcpv6-02: addressed comments (applicability
   statement, redesign the error codes and their logic) from IETF89 DHC
   WG meeting and volunteer reviewers. 2014-04-14.

   draft-ietf-dhc-sedhcpv6-01: addressed comments from IETF88 DHC WG
   meeting.  Moved Dacheng Zhang from acknowledgement to be co-author.
   2014-02-14.

   draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19.

   draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent
   and server due to complexity, following the comments from Ted Lemon,
   Bernie Volz. 2013-10-16.

   draft-jiang-dhc-sedhcpv6-01: update according to review comments from
   Ted Lemon, Bernie Volz, Ralph Droms.  Separated Public Key/
   Certificate option into two options.  Refined many detailed
   processes.  2013-10-08.

   draft-jiang-dhc-sedhcpv6-00: original version, this draft is a
   replacement of draft-ietf-dhc-secure-dhcpv6, which reached IESG and
   dead because of consideration regarding to CGA.  The authors followed
   the suggestion from IESG making a general public key based mechanism.
   2013-06-29.

15.

14.  Open Issues [RFC Editor: Please remove]

   this protocol changes DHCPv6 message exchanges quite substantially:
   previously, the client first sends a Solicit message, gets possibly
   multiple Advertise messages, chooses the server (= sender of one of
   the Advertises) that would be best for the client, and then sends a
   Request to that chosen server.  Now the server selection is done at
   the key exchange phase (the initial Information-request and

   The Reply
   exchange), and message with the Solicit can be sent only to a single server.  If error status code may contain the client doesn't like the Advertise it could restart
   identifier option, then the whole
   process, but it will client's privacy information may be more expensive, and there's no guarantee that
   other servers can provide a better Advertise.

   One might argue that it's okay as "secure DHCPv6"
   disclosed.  The possible way is an "optional"
   extension.  But, with keeping in mind that the current IETF trend is
   to make everything privacy-aware (often by making everything
   encrypted), I'd personally say we should consider it to be encrypts the
   standard mode of DHCPv6 operation even Reply message.
   But if users can still disable it.
   From this point of view, I think we should either

   o  A. make the error is AlogorithmNotSupported, then the server selection behavior more compatible with cannot
   encrypt the
      pre-encryption protocol, or

   o  B. accept we give up message with the previous server selection feature for
      privacy (after careful assessment algorithm used by client.

   We need to add some explanation on why TOFU is out of its effect and with clear wg
      consensus), and explicitly note that.  we might even have scope
   currently.  TOFU is tricky to
      reflect that get it right.  If it is included, then
   operator may skip necessary setup for security.  TOFU may be included
   in rfc3315bis.

16. the future work.

15.  References

16.1.

15.1.  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>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [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>.

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <http://www.rfc-editor.org/info/rfc3971>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              DOI 10.17487/RFC4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <http://www.rfc-editor.org/info/rfc5652>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <http://www.rfc-editor.org/info/rfc5905>.

   [RFC7283]  Cui, Y., Sun, Q., and T. Lemon, "Handling Unknown DHCPv6
              Messages", RFC 7283, DOI 10.17487/RFC7283, July 2014,
              <http://www.rfc-editor.org/info/rfc7283>.

   [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, <http://www.rfc-editor.org/info/rfc7296>.

16.2.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <http://www.rfc-editor.org/info/rfc7435>.

   [RFC7824]  Krishnan, S., Mrugalski, T., and S. Jiang, "Privacy
              Considerations for DHCPv6", RFC 7824,
              DOI 10.17487/RFC7824, May 2016,
              <http://www.rfc-editor.org/info/rfc7824>.

   [RFC7844]  Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
              Profiles for DHCP Clients", RFC 7844,
              DOI 10.17487/RFC7844, May 2016,
              <http://www.rfc-editor.org/info/rfc7844>.

15.2.  Informative References

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              DOI 10.17487/RFC2629, June 1999,
              <http://www.rfc-editor.org/info/rfc2629>.

   [RFC4270]  Hoffman, P. and B. Schneier, "Attacks on Cryptographic
              Hashes in Internet Protocols", RFC 4270,
              DOI 10.17487/RFC4270, November 2005,
              <http://www.rfc-editor.org/info/rfc4270>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6273]  Kukec, A., Krishnan, S., and S. Jiang, "The Secure
              Neighbor Discovery (SEND) Hash Threat Analysis", RFC 6273,
              DOI 10.17487/RFC6273, June 2011,
              <http://www.rfc-editor.org/info/rfc6273>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <http://www.rfc-editor.org/info/rfc7258>.

   [RSA]      RSA Laboratories, "RSA Encryption Standard, Version 2.1,
              PKCS 1", November 2002.

Authors' Addresses

   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   CN

   Email: jiangsheng@huawei.com

   Lishan Li
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-15201441862
   Email: lilishan48@gmail.com
   Yong Cui
   Tsinghua University
   Beijing  100084
   P.R.China

   Phone: +86-10-6260-3059
   Email: yong@csnet1.cs.tsinghua.edu.cn

   Tatuya Jinmei
   Infoblox Inc.
   3111 Coronado Drive
   Santa Clara, CA
   US

   Email: jinmei@wide.ad.jp

   Ted Lemon
   Nominum, Inc.
   2000 Seaport Blvd
   Redwood City, CA  94063
   USA

   Phone: +1-650-381-6000
   Email: Ted.Lemon@nominum.com

   Dacheng Zhang
   Beijing
   CN

   Email: dacheng.zhang@gmail.com