RADIUS Attribute for 6rd
draft-ietf-softwire-6rd-radius-attrib-08

Network Working Group                                       Dayong Guo 
Internet Draft                                    Sheng Jiang (Editor) 
Intended status: Standards Track          Huawei Technologies Co., Ltd 
Expires: June 11, 2013                                      R. Despres 
                                                             RD-IPtech 
                                                           R. Maglione 
                                                        Telecom Italia 
                                                     December 10, 2012 
                                    

                        RADIUS Attribute for 6rd 
                                    
              draft-ietf-softwire-6rd-radius-attrib-08.txt 

Status of this Memo 

   This Internet-Draft is submitted in full conformance with the 
   provisions of BCP 78 and BCP 79. 

   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF). Note that other groups may also distribute working 
   documents as Internet-Drafts. The list of current Internet-Drafts is 
   at http://datatracker.ietf.org/drafts/current/. 

   Internet-Drafts are draft documents valid for a maximum of six months 
   and may be updated, replaced, or obsoleted by other documents at any 
   time. It is inappropriate to use Internet-Drafts as reference 
   material or to cite them other than as "work in progress." 

   This Internet-Draft will expire on June 11, 2013. 

Copyright Notice 

   Copyright (c) 2012 IETF Trust and the persons identified as the 
   document authors. All rights reserved. 

   This document is subject to BCP 78 and the IETF Trust's Legal 
   Provisions Relating to IETF Documents 
   (http://trustee.ietf.org/license-info) in effect on the date of 
   publication of this document. Please review these documents 
   carefully, as they describe your rights and restrictions with respect 
   to this document. Code Components extracted from this document must 
   include Simplified BSD License text as described in Section 4.e of 
   the Trust Legal Provisions and are provided without warranty as 
   described in the Simplified BSD License. 

 
 
 
Jiang, et al.           Expires June 11, 2013                 [Page 1] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

    

Abstract 

   IPv6 Rapid Deployment (6rd) provides both IPv4 and IPv6 connectivity 
   services simultaneously during the IPv4/IPv6 co-existing period. The 
   Dynamic Host Configuration Protocol (DHCP) 6rd option has been 
   defined to configure 6rd Customer Edge (CE). However, in many 
   networks, the configuration information may be stored in 
   Authentication Authorization and Accounting (AAA) servers while user 
   configuration is mainly from Broadband Network Gateway (BNG) through 
   DHCP protocol. This document defines a Remote Authentication Dial In 
   User Service (RADIUS) attribute that carries 6rd configuration 
   information from AAA server to BNG. 

    

Table of Contents 

   1. Introduction ................................................ 3 
   2. Terminology ................................................. 3 
   3. IPv6 6rd Configuration with RADIUS .......................... 3 
   4. Attributes .................................................. 5 
      4.1. IPv6-6rd-Configuration Attribute ....................... 5 
      4.2. Table of attributes .................................... 8 
   5. Diameter Considerations ..................................... 9 
   6. Security Considerations ..................................... 9 
   7. IANA Considerations ......................................... 9 
   8. Acknowledgments ............................................. 9 
   9. References ................................................. 10 
      9.1. Normative References .................................. 10 
      9.2. Informative References ................................ 10 
    

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 2] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

    
1. Introduction 

   Recently providers have started to deploy IPv6 and consider how to 
   transit to IPv6. IPv6 Rapid Deployment (6rd) [RFC5969] provides both 
   IPv4 and IPv6 connectivity services simultaneously during the 
   IPv4/IPv6 co-existing period. 6rd is used to provide IPv6 
   connectivity service through legacy IPv4-only infrastructure. 6rd 
   adopts Dynamic Host Configuration Protocol (DHCP) [RFC2131] as auto-
   configuring protocol. The 6rd Customer Edge (CE) uses the DHCP 6rd 
   option [RFC5969] to discover 6rd border relay and to configure IPv6 
   prefix and address. 

   In many networks, user configuration information is managed by AAA 
   (Authentication, Authorization, and Accounting) servers. The Remote 
   Authentication Dial-In User Service (RADIUS) protocol [RFC2865] is 
   usually used by AAA servers to communicate with network elements. In 
   a fixed line broadband network, the Broadband Network Gateways (BNGs) 
   act as the access gateway of users. The BNGs are assumed to embed a 
   DHCP server function that allows them to locally handle any DHCP 
   requests issued by hosts. 

   Since the 6rd configuration information is stored in AAA servers and 
   user configuration is mainly through DHCP protocol between BNGs and 
   hosts/CEs, new RADIUS attributes are needed to propagate the 
   information from AAA servers to BNGs. 

2. Terminology 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in [RFC2119]. 

   The terms 6rd Customer Edge (6rd CE) and 6rd Border Relay (BR) are 
   defined in [RFC5969]. 

3. IPv6 6rd Configuration with RADIUS 

   The below Figure 1 illustrates how the RADIUS protocol and DHCP 
   cooperate to provide 6rd CE with 6rd configuration information. 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 3] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

      6rd CE                       BNG                       AAA Server 
         |                          |                             | 
         |-------DHCPDISCOVER------>|                             | 
         |(Parameter Request w/ 6rd option)                       | 
         |                          |--Access-Request(6rd Attr)-->| 
         |                          |                             | 
         |                          |<--Access-Accept(6rd Attr)---| 
         |<-------DHCPOFFER---------|                             | 
         |      (6rd option)        |                             | 
         |                          |                             | 
                   DHCP                         RADIUS  
             Figure 1: the cooperation between DHCP and RADIUS 
                       combining with RADIUS authentication 

   The BNG acts as a client of RADIUS and as a DHCP server for DHCP 
   protocol. First, the 6rd CE initiates a DHCPDISCOVER message that 
   includes a Parameter Request option (55) [RFC2132] with 6rd option 
   [RFC5969]. When the BNG receives the DHCPDISCOVER, it initiates a 
   Radius Access-Request message to the Radius server, requesting normal 
   authentication as defined in [RFC2865] and IPv6-6rd-Configuration 
   attribute, defined in the next Section, in the desired attribute  
   list. If the authentication request is approved by the AAA server, an 
   Access-Accept message is acknowledged with the IPv6-6rd-Configuration 
   Attribute. Then, the BNG responds to the 6rd CE with a DHCPOFFER 
   message, which contains DHCP 6rd option. 

   Figure 2 describes another scenario - later re-authorize, in which 
   the authorization operation is not coupled with authentication. 6rd 
   relevant authorization is done independently after the authentication 
   process. 

      6rd CE                       BNG                       AAA Server 
         |                          |                             | 
         |--------DHCPREQUEST------>|                             | 
         |(Parameter Request w/ 6rd option)                       | 
         |                          |--Access-Request(6rd Attr)-->| 
         |                          |                             | 
         |                          |<--Access-Accept(6rd Attr)---| 
         |                          |                             | 
         |<---------DHCPACK---------|                             | 
         |      (6rd option)        |                             | 
         |                          |                             | 
                   DHCP                         RADIUS 
              Figure 2: the cooperation between DHCP and RADIUS 
                        decoupled with RADIUS authentication 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 4] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

   In the abovementioned scenario, the Access-Request packet contains a 
   Service-Type attribute with the value Authorize Only (17); thus, 
   according to [RFC5080], the Access-Request packet MUST contain a 
   State attribute that succeeds from the previous authentication 
   process. 

   In both abovementioned scenarios, after receiving the IPv6-6rd-
   Configuration Attribute in the initial Access-Accept, the BNG MUST 
   store the received 6rd configuration parameters locally. When the 6rd 
   CE sends a DHCP Request message to request an extension of the 
   lifetime for the assigned address, the BNG does not have to initiate 
   a new Access-Request towards the AAA server to request the 6rd 
   configuration parameters. The BNG retrieves the previously stored 6rd 
   configuration parameters and use them in its reply. 

   If the BNG does not receive the IPv6-6rd-Configuration Attribute in 
   the Access-Accept it MAY fallback to a pre-configured default 6rd 
   configuration, if any. If the BNG does not have any pre-configured 
   default 6rd configuration or if the BNG receives an Access-Reject, 
   the tunnel cannot be established. 

   As specified in [RFC2131, section 4.4.5, "Reacquisition and 
   expiration", if the DHCP server to which the DHCP Request message was 
   sent at time T1 has not responded by time T2 (typically 
   0.375*duration_of_lease after T1), the 6rd CE (the DHCP client) 
   enters the REBINDING state and attempts to contact any server.  In 
   this situation, the secondary BNG receiving the new DHCP message MUST 
   initiate a new Access-Request towards the AAA server. The secondary 
   BNG MAY include the IPv6-6rd-Configuration Attribute in its Access-
   Request. 

4. Attributes 

   This section defines IPv6-6rd-Configuration Attribute which is used 
   in the both abovementioned scenarios. The attribute design follows 
   [RFC6158]. 

4.1. IPv6-6rd-Configuration Attribute 

   The IPv6-6rd-Configuration Attribute is structured as follows (The 
   specification requires that multiple IPv4 addresses are associated 
   strongly with one IPv6 prefix. Given that RADIUS currently has no 
   recommended way of grouping multiple attributes, the below design 
   appears to be a reasonable compromise.): 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 5] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

    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 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |      Type     |    Length     |    SubType1   |    SubLen1    | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                          IPv4MaskLen                          | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |    SubType2   |    SubLen2    |  Reserved     |  6rdPrefixLen | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   +                                                               + 
   |                                                               | 
   +                           6rdPrefix                           + 
   |                                                               | 
   +                                                               + 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |   SubType3    |    SubLen3    |        6rdBRIPv4Address       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |        6rdBRIPv4Address       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 

       Type 

         TBD 

       Length 

         28 + n*6 (the length of the entire attribute in octets; n 
         stands the number of BR IPv4 addresses, minimum n is 1). 

       SubType1 

         1 (SubType number, for the IPv4 Mask Length suboption) 

       SubLen1 

         6 (the length of the IPv4 Mask Length suboption) 

       IPv4MaskLen 

         The number of high-order bits that are identical across all CE 
         IPv4 addresses within a given 6rd domain. This may be any value 
         between 0 and 32. Any value greater than 32 is invalid. Since 
         [RFC6158] Section A.2.1 has forbidden 8-bit fields, 32-bit 
         field is used here. 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 6] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

       SubType2 

         2 (SubType number, for the 6rd prefix suboption) 

       SubLen2 

         20 (the length of the 6rd prefix suboption) 

       Reserved 

         Set to be all 0 for now. Reserved for the future use. To be 
         compatible with other IPv6 prefix attributes in the RADIUS 
         Protocol. The bits MUST be set to zero by the sender and MUST 
         be ignored by the receiver. 

       6rdPrefixLen 

         The IPv6 Prefix length of the Service Provider's 6rd IPv6 
         prefix in number of bits. The 6rdPrefixLen MUST be less than or 
         equal to 128. 

       6rdPrefix 

         The Service Provider's 6rd IPv6 prefix represented as a 16 
         octet IPv6 address. The bits after the 6rdPrefixlen number of 
         bits in the prefix SHOULD be set to zero. 

       SubType3 

         3 (SubType number, for the 6rd Border Relay IPv4 address 
         suboption) 

       SubLen3 

         6 (the length of the 6rd Border Relay IPv4 address suboption) 

       6rdBRIPv4Address 

         One or more IPv4 addresses of the 6rd Border Relay(s) for a 
         given 6rd domain. The maximum RADIUS Attribute length of 255 
         octets results in a limit of 37 IPv4 addresses. 

   Since the subtypes have values, they can appear in any order. If 
   multiple 6rdBRIPv4Address (subtype 3) appear, they are RECOMMENDED to 
   be placed together. 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 7] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

   The IPv6-6rd-Configuration Attribute is normally used in the  
   Access-Accept messages. It MAY be used in Access-Request packets as a 
   hint to the RADIUS server; for example if the BNG is pre-configured 
   with a default 6rd configuration, these parameters MAY be inserted in 
   the attribute. The RADIUS server MAY ignore the hint sent by the BNG 
   and it MAY assign different 6rd parameters. 

   If the BNG includes the IPv6-6rd-Configuration Attribute, but the AAA 
   server does not recognize it, this attribute MUST be ignored by the 
   AAA Server. 

   If the BNG does not receive IPv6-6rd-Configuration Attribute in the 
   Access-Accept it MAY fallback to a pre-configured default 6rd 
   configuration, if any. If the BNG does not have any pre-configured 
   default 6rd configuration, the 6rd tunnel cannot be established. 

   If the BNG is pre-provisioned with a default 6rd configuration and 
   the 6rd configuration received in Access-Accept is different from the 
   configured default, then the 6rd configuration received in the 
   Access-Accept message MUST be used for the session. 

   If the BNG cannot support the received 6rd configuration for any 
   reason, the tunnel SHOULD NOT be established. 

4.2. Table of attributes 

   The following table adds to the one in [RFC2865], Section 5.44, 
   providing a guide to the quantity of IPv6-6rd-Configuration 
   attributes that may be found in each kind of packet. 

   Request Accept Reject Challenge Accounting  #  Attribute 
                                    Request 
    0-1     0-1     0      0         0-1      TBD  IPv6-6rd- 
                                                   Configuration 

   The following table defines the meanings of the above table entries. 

   0     This attribute MUST NOT be present in packet. 
   0+    Zero or more instances of this attribute MAY be present in 
         packet. 
   0-1   Zero or one instance of this attribute MAY be present in 
         packet. 
   1     Exactly one instance of this attribute MUST be present in 
         packet. 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 8] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

5. Diameter Considerations 

   This attribute is usable within either RADIUS or Diameter [RFC6733]. 
   Since the Attributes defined in this document will be allocated from 
   the standard RADIUS type space, no special handling is required by 
   Diameter entities. 

6. Security Considerations 

   In 6rd scenarios, both CE and BNG are within a provider network, 
   which can be considered as a close and less security threat 
   environment. The similar consideration can be applied to the Radius 
   message exchanging between BNG and the AAA server. 

   In 6rd scenarios, the RADIUS protocol is run over IPv4. Known 
   security vulnerabilities of the RADIUS protocol are discussed in 
   [RFC2607], [RFC2865], and [RFC2869]. Use of IPsec [RFC4301] for 
   providing security when RADIUS is carried in IPv6 is discussed in 
   [RFC3162]. 

   Security considerations for the Diameter protocol are discussed in 
   [RFC6733]. 

7. IANA Considerations 

   This document requires the assignment of one new RADIUS Attribute 
   Types in the "Radius Types" registry (currently located at 
   http://www.iana.org/assignments/radius-types for the following 
   attributes: 

      o  IPv6-6rd-Configuration 

   IANA should allocate the number from the standard RADIUS Attributes 
   range (values 1-191).  The RFC Editor should use the assigned value 
   to replace "TBD" in Sections 4.1 and 4.2, and should remove this 
   paragraph. 

8. Acknowledgments 

   The authors would like to thank Alan DeKok, Yong Cui, Leaf Yeh, Sean 
   Turner, Joseph Salowey, Glen Zorn, Dave Nelson, Bernard Aboba, Benoit 
   Claise, Barry Lieba, Stephen Farrell, Adrian Farrel, Ralph Droms and 
   other members of Softwire WG, RadiusExt WG, AAA-Doctors and Secdir 
   for valuable comments. 

 
 
Jiang, et al.           Expires June 11, 2013                 [Page 9] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

9. References 

9.1. Normative References 

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 
             Requirement Levels", BCP 14, RFC 2119, March 1997. 

   [RFC2131] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131, 
             March 1997. 

   [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor 
             Extensions", RFC 2132, March 1997. 

   [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 
             "Remote Authentication Dial In User Service (RADIUS)", RFC 
             2865, June 2000. 

   [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", RFC 
             3162, August 2001. 

   [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 
             Internet Protocol", RFC 4301, December 2005. 

   [RFC5080] Nelson, D. and DeKok A., "Common Remote Authentication Dial 
             In User Service (RADIUS) Implementation Issues and 
             Suggested Fixes", RFC 5080, December 2007. 

   [RFC5969] Townsley, M. and O. Troan, "IPv6 Rapid Deployment on IPv4 
             Infrastructures (6rd) -- Protocol Specification", RFC5969, 
             August 2010. 

   [RFC6158] DeKok, A. and G. Weber, "RADIUS Design Guidelines", RFC 
             6158, March 2011. 

   [RFC6733] V. Fajardo, Ed., J. Arkko, J. Loughney, G. Zorn, Ed., 
             "Diameter Base Protocol", RFC 6733, October 2012. 

9.2. Informative References 

   [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy 
             Implementation in Roaming", RFC 2607, June 1999. 

   [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS 
             Extensions", RFC 2869, June 2000. 
 

 
Jiang, et al.           Expires June 11, 2013                [Page 10] 


Internet-Draft draft-ietf-softwire-6rd-radius-attrib-08   December 2012 
    

   Author's Addresses 

   Dayong Guo 
   Huawei Technologies Co., Ltd 
   Q14 Huawei Campus, 156 BeiQi Road, 
   ZhongGuan Cun, Hai-Dian District, Beijing 100095 
   P.R. China 
   Email: guoseu@huawei.com 
    
   Sheng Jiang (Editor) 
   Huawei Technologies Co., Ltd 
   Q14 Huawei Campus, 156 BeiQi Road, 
   ZhongGuan Cun, Hai-Dian District, Beijing 100095 
   P.R. China 
   Email: jiangsheng@huawei.com 
    
   Remi Despres 
   RD-IPtech 
   3 rue du President Wilson 
   Levallois, 
   France 
   Email: despres.remi@laposte.net 
    
   Roberta Maglione 
   Telecom Italia 
   Via Reiss Romoli 274 
   Torino 10148 
   Italy 
   Email: roberta.maglione@telecomitalia.it 

 
 
Jiang, et al.           Expires June 11, 2013                [Page 11]