Softwire                                                          Y. Lee
Internet-Draft                                                   Comcast
Intended status: Informational                               R. Maglione
Expires: July 21, 2013                                    Telecom Italia
                                                             C. Williams
                                                               MCSR Labs
                                                            C. Jacquenet
                                                            M. Boucadair
                                                          France Telecom
                                                        January 17, 2013

             Deployment Considerations for Dual-Stack Lite


   This document discusses the deployment issues and describes
   requirements for the deployment and operation of Dual-Stack Lite.
   This document describes the various deployment considerations and
   applicability of the Dual-Stack Lite architecture.

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
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   Drafts is at

   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 July 21, 2013.

Copyright Notice

   Copyright (c) 2013 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
   ( in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  AFTR Deployment Considerations . . . . . . . . . . . . . . . .  3
     2.1.  Interface Consideration  . . . . . . . . . . . . . . . . .  3
     2.2.  MTU and Fragmentation Considerations . . . . . . . . . . .  4
     2.3.  Logging at the AFTR  . . . . . . . . . . . . . . . . . . .  4
     2.4.  Blacklisting a Shared IPv4 Address . . . . . . . . . . . .  5
     2.5.  AFTR's Policies  . . . . . . . . . . . . . . . . . . . . .  5
       2.5.1.  Outgoing Policy  . . . . . . . . . . . . . . . . . . .  5
       2.5.2.  Incoming Policy  . . . . . . . . . . . . . . . . . . .  6
     2.6.  AFTR Impacts on Accounting Process . . . . . . . . . . . .  6
     2.7.  Reliability Considerations of AFTR . . . . . . . . . . . .  7
     2.8.  Strategic Placement of AFTR  . . . . . . . . . . . . . . .  8
     2.9.  AFTR Considerations for Geographically Aware Services  . .  8
     2.10. Impacts on QoS Policy  . . . . . . . . . . . . . . . . . .  9
     2.11. Port Forwarding Considerations . . . . . . . . . . . . . .  9
     2.12. DS-Lite Tunnel Security  . . . . . . . . . . . . . . . . . 10
     2.13. IPv6-only Network Considerations . . . . . . . . . . . . . 10
   3.  B4 Deployment Considerations . . . . . . . . . . . . . . . . . 11
     3.1.  DNS Deployment Considerations  . . . . . . . . . . . . . . 11
     3.2.  IPv4 Service Monitoring  . . . . . . . . . . . . . . . . . 11
       3.2.1.  B4 Remote Management . . . . . . . . . . . . . . . . . 11
       3.2.2.  IPv4 Connectivity Check  . . . . . . . . . . . . . . . 12
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   5.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

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1.  Overview

   Dual-stack Lite (DS-Lite) [RFC6333] is a transition technique that
   enable operators to multiplex public IPv4 addresses while
   provisioning only IPv6 to users.  DS-Lite is designed to continue
   offering IPv4 services while operators upgrading their network
   incrementally to IPv6.  DS-Lite combines IPv4-in-IPv6 softwire
   [RFC2473] and NAT44 [RFC3022] to enable more than one user to share a
   public IPv4 address.

   While Appendix A of [RFC6333] explains how to deploy DS-Lite within
   specific scenarios, the purpose of this document is to describe
   problems that arise when deploying DS-Lite and what guidance should
   be taken to mitigate those issues.  The information is based on real
   deployment experience and compiled in one comprehensive document so
   that operators aren't required to search through various RFCs
   deciding which sections are applicable and impact their DS-Lite

2.  AFTR Deployment Considerations

2.1.  Interface Consideration

   Address Family Transition Router (AFTR) is a network element that
   deployed inside the operator's network.  AFTR can be a standalone
   device or embedded into a router.  AFTR is the IPv4-in-IPv6 tunnel
   termination point and the NAT44 device.  It is deployed at the IPv4-
   IPv6 network border where the tunnel interface is IPv6 and the
   external NAT44 interface is IPv4.  The B4 element [RFC6333] is a
   function implemented on a dual-stack capable node, either a host
   device or a home gateway that creates a tunnel to an AFTR.  Although
   an operator can configure both softwire tunnel termination and
   interface for NAT44 functions on a single physical interface (yet
   logically separated), there are scenarios we recommend to configure
   two individual interfaces (i.e. one dedicated for IPv4 and one
   dedicated for IPv6) to segregate the functions.

   o  The access network between the B4 and AFTR is an IPv6-only network
      and the network between AFTR and IPv4 network is either IPv4-only
      network.  In this deployment scenario, the AFTR interface to the
      IPv6-only network and the interface to the IPv4 network should use
      two physical interfaces on AFTR.

   o  Operators may use Operations Support System (OSS) tools (e.g.,
      Multi Router Traffic Grapher) to collect interface data packet
      count information.  If an operator wants to separate the softwire
      function and NAT44 function on different physical interfaces for

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      collecting data packet count and the AFTR does not support packet
      count for logical interfaces, they should use two physical
      interfaces on AFTR.

2.2.  MTU and Fragmentation Considerations

   DS-Lite is part tunneling protocol.  Tunneling introduces overhead to
   the packet and decreases the effective MTU size after encapsulation.
   The DS-lite users may experience problems with applications such as
   not being able to download Internet pages or transfer large files.

   Since fragmentation and reassembly is not optimal, the operator
   should do everything possible to eliminate the need for it.  If the
   operator uses simple IPv4-in-IPv6 softwire [RFC2473], it is
   recommended that the MTU size of the IPv6 network between the B4 and
   the AFTR account for the additional overhead (40 bytes).  If the
   access network MTU size is fixed and cannot be changed, the operator
   should be aware that the B4 element and the AFTR must support
   fragmentation as defined in [RFC6333].  The operator should also be
   aware that reassembly at Tunnel Exit-Point is resource intensive as a
   large number of B4 may terminate on the same AFTR.  Scalability of
   the AFTR is advised in this scenario.

2.3.  Logging at the AFTR

   Source-Specific Log is essential for back tracking specific users
   when a problem is identified with one of the AFTR's NAT-ed addresses.
   Source-specific log contains the B4 IPv6 source address, transport
   protocol, source port, and source IPv4 address after NAT-ed.  Using
   the Source-specific log, operators can uniquely identify a specific
   user when a DS-Lite user experiences problem to access IPv4 network.
   To maximize IPv4 shared radio, an operator may configure a short
   timeout value for NAT44 entries.  This will result a large numbers of
   log created by the AFTR.  For operators who desire to aggregate the
   logs, they can configure AFTR to pre-allocate a range of ports to
   each user.  This range of ports will be used in the NAT44 function
   and the AFTR will create one log entry for the whole port-range.
   This aggregation can significantly reduce the log size for Source-
   specific logging.

   Some operators may require to log both source and destination
   information for user's connections.  This is called Destination-
   Specific Log. Destination-specific log contains the B4's IPv6
   address, transport protocol, source port, source IPv4 address after
   NAT-ed, destination port and destination IPv4 address.  Destination-
   specific log is session-based, the operators should be aware that
   they will not be able to aggregate log entries.  When using
   destination-specific log, the operator must be careful of the large

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   number of log entries created by the AFTR.  Some AFTR implementations
   may keep the logs in main memory.  This may be CPU and memory
   resource intensive.  We suggest the operators must configure the AFTR
   to periodically send logs to storage facility and then purge them
   from AFTR.

2.4.  Blacklisting a Shared IPv4 Address

   AFTR is a NAT device.  It enables multiple users to share a single
   public IPv4 address.  [RFC6269] discusses some considerations when
   sharing an IPv4 address.  When a public IPv4 address is blacklisted
   by a remote peer, this may affect multiple B4 elements sharing the
   same IPv4 address.  Operators deploying DS-Lite should be aware that
   Internet hosts may rely solely on source IP address to identify an
   abusive household and may not be aware that a given single IPv4
   address is actually shared by multiple households.  A content
   provider may block services for a shared IPv4 address and this will
   impact all households sharing this particular IPv4 address.  The
   operator may receive calls of service outage and will need to take
   appropriate actions.  Such corrective actions include but not limited
   to notifying the content provider to combine the IPv4 address with
   transport (e.g., TCP) and application protocol (e.g., HTTP) to
   identify abusive household.  [RFC6302].
   [I-D.ietf-intarea-nat-reveal-analysis] analyzes different approaches
   to identify a user in a shared address environment.

2.5.  AFTR's Policies

   There are two types of AFTR policies:

   o  Outgoing Policies apply to packets originating from B4 to AFTR.
      These policies should be provisioned on the AFTR's IPv6 interface
      connected to the B4 elements.

   o  Incoming Policies apply to packets originating from IPv4 network
      to B4s.  These policies should be provisioned on the IPv4
      Interface connected to the IPv4 network.

2.5.1.  Outgoing Policy

   Outgoing policies may include Access Control List (ACL) and Qualify
   of Service (QoS) settings.  These policies control the packets from
   B4 elements to the AFTR.  For example, the operator may configure the
   AFTR only to accept B4's connections originated from specific IPv6
   prefixes configured in the AFTR.  More discussion of this use case
   can be found in Section 2.12.  An operator may configure the AFTR to
   give priority to the packets marked by certain DSCP values [RFC2475].
   Furthermore, an AFTR may also apply outgoing policy to limit the rate

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   of port allocation for a single B4's IPv6 address.

   Some operators offer different service level agreements (SLA) to
   users to meet their requirements.  Some users may require more ports
   and some may require different service priority.  In this deployment
   scenario, the operator can implement outgoing policies specified to a
   user's B4 element or a group of B4 elements sharing the same

2.5.2.  Incoming Policy

   Similar to Outgoing Policy, Incoming Policy may also include ACL and
   QoS settings.  Outgoing Policy controls packets coming from IPv4
   network to the B4 elements.  Incoming packets are normally treated
   equally, so these policies are globally applied.  For example, an
   operator wants to use a pre-defined DSCP value to signal the IPv6
   access network to apply certain traffic policies.  In this deployment
   scenario, the operator can configure the AFTR to mark the incoming
   packets with the pre-defined DSCP value.  This policy will apply to
   all incoming packets from the IPv4 network.

2.6.  AFTR Impacts on Accounting Process

   This section discusses IPv4 and IPv6 traffic accounting in DS-Lite
   environment.  In a typical broadband access scenario (e.g.  DSL or
   Cable), the B4 element is embedded in the Residential Gateway and the
   edge router (e.g., Broadband Network Gateway or Cable Modem
   Termination System) is the IPv6 edge router.  The edge router is
   usually responsible for IPv6 accounting and the user management
   functions such as authentication, authorization and accounting (AAA).
   However, given the fact that IPv4 traffic is encapsulated in an IPv6
   packet at the B4 and only decapsulated at the ATFR, the edge router
   will require additional function to associate IPv4 accounting
   information to the B4 IPv6 address.  If DS-lite is the only
   application using IPv4-in-IPv6 protocol in the IPv6 access network,
   the operator can configure the edge router to check the IPv6 Next
   Header field in the IPv6 header and identify the protocol type (i.e.
   0x04) and collect IPv4 accounting information.

   Alternatively, AFTR may perform accounting for IPv4 traffic.
   However, operators must be aware that this will introduce some
   challenges especially in DSL deployment.  In DSL deployment, the AAA
   transaction normally happens between the edge router (i.e., Broadband
   Network Gateway) and AAA server.  [RFC6333] does not require the AFTR
   to interact with the AAA server or edge router.  Thus, AFTR may not
   have the AAA parameters (e.g., Account Session ID) associated to
   users to generate IPv4 accounting record.  The accounting process at
   the AFTR is only necessary if the operator requires separating per

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   user accounting records for IPv4 and IPv6 traffic.  If the per user
   IPv6 accounting records, collected by the edge router, are
   sufficient, and the additional complexity of enabling IPv4 accounting
   at the ATFR is not required.  It is important to notice that, since
   the IPv4 traffic is encapsulated in IPv6 packets, the data collected
   by the edge router for IPv6 traffic already contain the total amount
   of traffic (i.e.  IPv4 and IPv6).

   Even if detailed accounting records collection for IPv4 traffic may
   not be required, it would be useful for an operator in some scenarios
   to have information the edge router generates that for the IPv6
   traffic and can be used to identify the AFTR who is handling the IPv4
   traffic for that user.  This can be achieved by adding additional
   information to the IPv6 accounting records.  For example: operators
   can use RADIUS attribute information specified in [RFC6519] or a new
   attribute to be specified in Internet Protocol Detailed Record

2.7.  Reliability Considerations of AFTR

   For robustness, reliability and load distribution purposes, operators
   may deploy multiple AFTRs.  In such case, the same IPv6 prefixes and
   algorithm to build the tunneling mechanisms will be configured on
   those AFTRs.  In [RFC6333] A.3 mentions High Availability (HA) is the
   operator's responsibility.  Since DS-lite is a stateful mechanism,
   all requirements for load-balancing and failover mechanism apply.
   There are many ways to implement HA in stateful mechanism, most
   common are Cold Standby mode and Hot Standby mode.  More discussion
   on deploying of these two modes for NAT can be found in
   [I-D.xu-behave-stateful-nat-standby] In Cold Standby mode the AFTR
   states are not replicated from the Primary AFTR to the Backup AFTR.
   When the Primary AFTR fails, all the existing established sessions
   will be flushed out.  The internal hosts are required to re-establish
   sessions with the external hosts.  In Hot Standby mode the user's
   states are replicated on-the-fly from the Primary AFTR to the Backup
   AFTR.  When the Primary AFTR fails, the Backup AFTR will take over
   all the existing established sessions.  In this mode the internal
   hosts are not required to re-establish sessions with the external

   For operators, the decision to use Cold Standby mode or Hot Standby
   mode depends on the trade-off between capital cost and operational
   cost.  Cold Standby mode does not require a Backup Standby AFTR to
   synchronize user states.  This simplifies the operational model.
   When the Primary AFTR went down, any AFTR with extra capacity could
   take over.  Hot Standby mode provides a smoother failover experience
   to users, the cost for the operators is more careful failover
   planning.  For most deployment scenarios, we believe that Cold

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   Standby mode should be sufficient enough and thus recommended.

2.8.  Strategic Placement of AFTR

   In DS-Lite environment, AFTR is the logical next-hop router of the B4
   elements to access IPv4 network, so the placement of the AFTR will
   affect the traffic flows in the access network and overall network
   design.  In general, there are two placement models to deploy AFTR.
   Model One is to deploy the AFTR in the edge of the network to cover a
   small region.  Model Two is to deploy the AFTR in the core of network
   to cover a large region.

   When an operator considers where to deploy the AFTR, it must make
   trade-offs.  AFTR in Model One serves fewer B4 elements, thus, it
   requires less powerful AFTR.  Moreover, the traffic flows are more
   evenly distributed to the AFTRs.  However, it requires deploying more
   AFTRs to cover the entire network.  Often the operation cost
   increases proportionally with to the number of network equipment.

   AFTR in Model Two covers a larger area, thus, it serves more B4
   elements.  The operator could deploy only few AFTRs to support the
   entire user base.  However, this model requires more powerful AFTR to
   sustain the load at peak hours.  Since AFTR would support B4 elements
   from different regions, AFTR would be deployed closer to the core

   DS-Lite framework can be incrementally deployed.  An operator may
   consider to start with Model Two. When the demand increases, the
   operator could push the AFTR closer to the edge, which would
   effectively become Model One.

2.9.  AFTR Considerations for Geographically Aware Services

   By centralizing public IPv4 addresses in AFTR, remote services can no
   longer rely on an IPv4 address and IPv4 routing information to derive
   a user's geographical information.  For example, the IPv6 access
   network and the AFTR may be in two different cities.  If the remote
   services rely on the IPv4 address to locate a user, they may have
   thought the user was in a different city.  [RFC6269] Section 7
   describe the problem in more details.  Applications could explicitly
   ask users to enter location information such as postal code or
   telephone number before offering geographical service.  In contrast,
   applications could use HELD [RFC5985] to get the location information
   from the Location Information Server and give this information to the
   remote peer.  [RFC6280] describes an architecture to enable location-
   based services.  However to mitigate the impact, we recommend
   operators to deploy AFTR as close to users as possible.

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2.10.  Impacts on QoS Policy

   This section describes the application of [RFC2983] to DS-Lite
   deployment model.  Operators must ensure that the QoS policy that is
   in place operates properly within the DS-Lite deployment.  In this
   regard, operators commonly use DSCP [RFC2475] to classify and
   prioritize different types of traffic in their networks.  DS-Lite
   tunnel can be seen as a particular case of uniform conceptual tunnel
   model described in section 3.1 of [RFC2983].  The uniform model views
   an IP tunnel as just a necessary mechanism to forward traffic to its
   destination, but the tunnel has no significant impact on traffic
   conditioning.  In this model, any packet has exactly one DSCP Field
   that is used for traffic conditioning at any point and it is the
   field in the outermost IP header.  In DS-Lite model this is the
   Traffic Class field in IPv6 header.  According to [RFC2983]
   implementations of this model copy the DSCP value to the outer IP
   header at encapsulation and copy the outer header's DSCP value to the
   inner IP header at decapsulation.

   Operators should use this model by provisioning the network such that
   the AFTR copies the DSCP value in the IPv4 header to the Traffic
   Class field in the IPv6 header after the encapsulation for the
   downstream traffic.  Similarly the B4 copies the DSCP value in the
   IPv4 header to the Traffic Class field to the IPv6 header after the
   encapsulation for the upstream traffic.  Traffic identification and
   classification can be done by examining the outer IPv6 header in the
   IPv6 access network.

2.11.  Port Forwarding Considerations

   Some applications behind the B4 element require the B4 element to
   accept incoming requests.  If the remote application wants to
   communicate to the application behind the B4 element, the remote
   application must know both the NAT-ed IPv4 address used by the B4
   element and the IPv4 destination port.  Some applications use
   Universal Plug and Play (UPnP) (e.g., popular gaming consoles) or ICE
   [RFC5245] to request incoming ports.  Some applications rely on
   Application Level Gateway (ALG) or manual port configuration to
   reserve a port in the NAT.  For the DS-Lite deployment scenario
   whereby the B4 does not own a dedicated public IPv4 address or all
   the available ports, the operator will manage port-forwarding in the
   serving AFTR.  Operators may use Port Control Protocol (PCP)
   [I-D.ietf-pcp-base] as guidance to provide port-forwarding service.
   Operators will deploy PCP client in the B4 elements.  PCP permits PCP
   server to be deployed in a standalone server.  However, we recommend
   the operators to consider deploying the PCP server in the AFTR.  This
   will ease the overhead to design a global configuration for PCP
   server for many AFTRs because each PCP server will be dedicated to

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   the collocated AFTR.

   When sharing an IPv4 address, not all the ports are available to a
   user.  Some restricted ports (i.e., 0-1023) are well-known such as
   TCP port 25 and 80.  Many users may want to be provisioned with the
   restricted ports.  For fairness, we recommend operators to configure
   the AFTR not to allocate the restricted ports to regular DS-Lite
   users.  This operation model ensures that DS-lite users will have
   uniform configuration, which can simplify provisioning and operation.
   For users who want to use the restricted ports, operators can
   consider to provision a full IPv4 address to those users.  If an
   operator still want to provision restricted ports to specific users,
   it may require to implement static user's configuration in the AFTR
   to match the B4's IPv6 address to the NAT rules.  Alternatively, the
   B4 element may dynamically allocate the ports and the AFTR
   authenticates the user's request using PCP [I-D.ietf-pcp-base].

2.12.  DS-Lite Tunnel Security

   [RFC6333] Section 11 describes security issues associated to DS-Lite
   mechanism.  To restrict the service offered by AFTR only to
   registered users, an operator can implement Outgoing Policy on the
   AFTR's tunnel interface to accept only the IPv6 prefixes defined in
   the policy.  For static provisioning, the operator will need to know
   in advance the IPv6 prefixes provisioned to the users for the
   softwire in order to configure the policy.  To simplify operation,
   operators should configure the AFTRs in the same region with the same
   IPv6 prefixes Outgoing Policy.  The AFTRs will accept both regular
   connections and failover connections from the B4 elements in the same
   service region.

2.13.  IPv6-only Network Considerations

   In environments where the operator wants to deploy AFTR in the IPv6-
   only network, the AFTR nodes may not have direct IPv4 connectivity.
   In this scenario the operator extends the IPv6-only boundary to the
   border of the network and only the border routers have IPv4
   connectivity.  For both scalability and performance purposes, AFTR is
   located in the IPv6-only network closer to B4 elements.  In this
   scenario the AFTR has only IPv6 connectivity and must be able to send
   and receive IPv4 packets.  Enhancements to the DS-Lite AFTR are
   required to achieve this.  [I-D.boucadair-softwire-dslite-v6only]
   describes such issues and enhancements to DS-Lite in IPv6-only

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3.  B4 Deployment Considerations

   In order to configure the IPv4-in-IPv6 tunnel, the B4 element needs
   the IPv6 address of the AFTR element.  This IPv6 address can be
   configured using a variety of methods, ranging from an out-of-band
   mechanism, manual configuration, DHCPv6 option to RADIUS.  If an
   operator uses DHCPv6 to provision the B4, the B4 element must
   implement the DHCPv6 option defined in [RFC6334].  If an operator
   uses RADIUS to provision the B4, the B4 element must implement

3.1.  DNS Deployment Considerations

   [RFC6333] recommends the B4 element should send DNS queries to an
   external recursive resolver over IPv6.  The B4 element should
   implement proxy resolver that will proxy DNS query from IPv4
   transport to the DNS server in the IPv6 network.  [RFC6333] does not
   describe the DNS proxy behavior.  In deployment, the operator must
   ensure that the DNS proxy implementation must follow [RFC5625].  This
   is important especially for operators who have deployed or consider
   to deploy DNSSEC [RFC4035].

   Some operators may want to give clients behind the B4's element an
   IPv4 address of an external DNS recursive resolver.  The B4 element
   will treat the DNS packets as normal IP packets and forward over the
   softwire.  Note that there is no effective way to provision an IPv4
   DNS address to the B4 over IPv6, operators who use this DNS
   deployment model must be aware that it is undefined how to provision
   an IPv4 DNS address over an IPv6 network, so it will introduce
   additional complexity in B4 provisioning.  Moreover, this will
   increase load to AFTR by creating entries in the NAT table for DNS
   sessions.  Operators may deploy a local DNS caching resolver in AFTR
   to reduce the load in the NAT table.  Nonetheless, this DNS model is
   not covered in [RFC6333] and is not recommended.

3.2.  IPv4 Service Monitoring

3.2.1.  B4 Remote Management

   B4 is connected to IPv6 access network to offer IPv4 services.  When
   users experience IPv4 connectivity issue, operators must be able to
   remotely access (e.g.  TR-069) the B4 element to verify its B4's
   configuration and status.  Operators should access B4 elements using
   native IPv6.  Operators should not access B4 over the softwire.

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3.2.2.  IPv4 Connectivity Check

   DS-Lite framework provides IPv4 services over IPv6 access network.
   Operators and users must be able to check the IPv4 connectivity from
   the B4 element to its AFTR using PING and IPv4 Traceroute.  AFTR
   should be configured with an IPv4 address to enable PING test and
   Traceroute test.  Operators should assign the same IPv4 address
   (i.e., to all AFTRs.  IANA allocates
   [RFC6333] Section 5.7 that can be used for this purpose.

4.  Security Considerations

   This document does not present any new security issues.  [RFC6333]
   discusses DS-Lite related security issues.

5.  Acknowledgement

   Thanks to Mr. Nejc Skoberne and Dr. Maoke Chen for their thorough
   review and helpful comments.  We also want to thank Mr. Hu Jie for
   sharing his DS-Lite deployment experience to us.  He gave us
   recommendations what his company learned while testing DS-Lite in the
   production network.

6.  IANA Considerations

   This memo includes no request to IANA.

7.  References

7.1.  Normative References

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, August 2011.

   [RFC6519]  Maglione, R. and A. Durand, "RADIUS Extensions for Dual-
              Stack Lite", RFC 6519, February 2012.

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7.2.  Informative References

              Boucadair, M., Jacquenet, C., Grimault, J., Kassi-Lahlou,
              M., Levis, P., Cheng, D., and Y. Lee, "Deploying Dual-
              Stack Lite in IPv6 Network",
              draft-boucadair-softwire-dslite-v6only-01 (work in
              progress), April 2011.

              Boucadair, M., Touch, J., Levis, P., and R. Penno,
              "Analysis of Solution Candidates to Reveal a Host
              Identifier (HOST_ID) in Shared Address Deployments",
              draft-ietf-intarea-nat-reveal-analysis-04 (work in
              progress), August 2012.

              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)",
              draft-ietf-pcp-base-29 (work in progress), November 2012.

              Xu, X., Boucadair, M., Lee, Y., and G. Chen, "Redundancy
              Requirements and Framework for Stateful Network Address
              Translators (NAT)",
              draft-xu-behave-stateful-nat-standby-06 (work in
              progress), October 2010.

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, December 1998.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.

   [RFC2983]  Black, D., "Differentiated Services and Tunnels",
              RFC 2983, October 2000.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              January 2001.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)

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              Traversal for Offer/Answer Protocols", RFC 5245,
              April 2010.

   [RFC5625]  Bellis, R., "DNS Proxy Implementation Guidelines",
              BCP 152, RFC 5625, August 2009.

   [RFC5985]  Barnes, M., "HTTP-Enabled Location Delivery (HELD)",
              RFC 5985, September 2010.

   [RFC6269]  Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
              Roberts, "Issues with IP Address Sharing", RFC 6269,
              June 2011.

   [RFC6280]  Barnes, R., Lepinski, M., Cooper, A., Morris, J.,
              Tschofenig, H., and H. Schulzrinne, "An Architecture for
              Location and Location Privacy in Internet Applications",
              BCP 160, RFC 6280, July 2011.

   [RFC6302]  Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
              "Logging Recommendations for Internet-Facing Servers",
              BCP 162, RFC 6302, June 2011.

Authors' Addresses

   Yiu L. Lee
   One Comcast Center
   Philadelphia, PA  19103


   Roberta Maglione
   Telecom Italia
   Via Reiss Romoli 274
   Torino  10148


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   Carl Williams
   MCSR Labs


   Christian Jacquenet
   France Telecom


   Mohamed Boucadair
   France Telecom


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