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Network Working Group                                              J. Bi
Internet-Draft                                                     J. Wu
Intended status: Standards Track                                 Y. Wang
Expires: September 26, 2018                          Tsinghua University
                                                                  T. Lin
                                            New H3C Technologies Co. Ltd
                                                          March 25, 2018


                        A SAVI Solution for WLAN
                         draft-bi-savi-wlan-14

Abstract

   This document describes a source address validation solution for WLAN
   enabling 802.11i or other security mechanisms.  This mechanism snoops
   NDP and DHCP packets to bind IP address to MAC address, and relies on
   the security of MAC address guaranteed by 802.11i or other mechanisms
   to filter IP spoofing packets.  It can work in the special situations
   described in the charter of SAVI(Source Address Validation
   Improvements) workgroup, such as multiple MAC addresses on one
   interface.  This document describes three different deployment
   scenarios, with solutions for migration of binding entries when hosts
   move from one access point to another.

Status of This Memo

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

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

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

   This Internet-Draft will expire on September 26, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  IP-MAC Binding  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Data Structures . . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  IP-MAC Mapping Table  . . . . . . . . . . . . . . . .   3
       3.1.2.  MAC-IP Mapping Table  . . . . . . . . . . . . . . . .   4
     3.2.  Pre-conditions for binding  . . . . . . . . . . . . . . .   4
     3.3.  Binding IP addresses to MAC addresses . . . . . . . . . .   5
     3.4.  Binding Migration . . . . . . . . . . . . . . . . . . . .   5
     3.5.  Binding Clearing  . . . . . . . . . . . . . . . . . . . .   6
   4.  Source Address Validation . . . . . . . . . . . . . . . . . .   6
   5.  Deployment Scenarios  . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Centralized WLAN  . . . . . . . . . . . . . . . . . . . .   7
       5.1.1.  AP Filtering  . . . . . . . . . . . . . . . . . . . .   7
       5.1.2.  AC Filtering  . . . . . . . . . . . . . . . . . . . .  11
     5.2.  Autonomous WLAN . . . . . . . . . . . . . . . . . . . . .  12
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
     7.1.  Issues with Triggerring Establishment of Binding Entries
           by Data Packets . . . . . . . . . . . . . . . . . . . . .  12
     7.2.  Privacy Considerations  . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   This document describes a mechanism to perform per packet IP source
   address validation in WLAN.  This mechanism performs ND snooping or
   DHCP snooping to bind allocated IP address with authenticated MAC
   address.  Static addresses are bound to the MAC addresses of
   corresponding hosts manually.  Then the mechanism can check validity
   of source IP address in local packets according to the binding



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   association.  The security of MAC address is assured by 802.11i or
   other mechanisms, thus the binding association is secure.

   The situation that one interfaces with multiple MAC addresses is a
   special case mentioned in the charter of SAVI.  And this situation is
   the only special case that challenges MAC-IP binding.  The mechanism
   to handle this situation is specified in the document.

   There are three deployment scenarios specified in this document.  The
   mechanism is deployed on different devices in different scenarios.
   The deployment detail is described in the document.

   When hosts move from one access point to another, the migration of
   binding entries may be triggered according to the specific mobility
   scenario.  The mechanism to handle host mobility is specified in the
   document according to different deployment scenarios.

1.1.  Terminology

   FIT Access Points: the name of Access Points in Centralized WLAN
   deployment scenario.

   FAT Access Points: the name of Access Points in Autonomous WLAN
   deployment scenario.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].

3.  IP-MAC Binding

   This section specifies the operations for creating and clearing of
   bindings between IP addresses to MAC addresses.

3.1.  Data Structures

3.1.1.  IP-MAC Mapping Table

   This table maps IP addresses to corresponding MAC addresses.  IP
   address is the index of the table.  One IP address can only have one
   corresponding MAC address, while different IP addresses can be mapped
   to the same MAC address.

   This table is used in control process.  Before creating new IP-MAC
   bindings, this table must first be consulted in case of conflict in
   binding entries.  Also, this table must be consulted before doing any



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   packet filtering.  This table must be synchronized with the MAC-IP
   table specified in Section 3.1.2.

   Each entry in IP-MAC mapping table must also record the binding state
   of the IP address.  Addresses snooped in DHCP address assignment
   procedure must record its state as "DHCPv6", and addresses snooped in
   Duplicate Address Detection procedure must record its state as
   "SLAAC".

   Each entry in IP-MAC mapping table has its lifetime.  According to
   RFC3315 [RFC3315], the address allocated by DHCP has a limited
   lifetime, so the related entry records its lifetime the same as that
   of the address.  According to RFC4862 [RFC4862], stateless address
   also has a limited lifetime, and the host set this lifetime by
   itself.  Thus the related entry also records its lifetime the same as
   that of the address.

3.1.2.  MAC-IP Mapping Table

   This table maps MAC addresses to corresponding IP addresses.  MAC
   address is the index of the table.  It is a one-to-many mapping
   table, which means a MAC address can be mapped to multiple IP
   addresses.  Though multiple MAC addresses may exist on one interface,
   these MAC addresses must be mapped to different IP addresses.

   This table is used for filtering.  Different from wired network, MAC-
   IP mapping table and IP-MAC mapping table can be maintained
   separately on different devices.  Mechanisms for synchronization
   between the two tables must be employed for the consistency of the
   bindings.  We will specify the details in Section 5 according to
   different deployment scenarios.

3.2.  Pre-conditions for binding

   In the binding based mechanism, the security of IP address is based
   on the security of the binding anchor.  In WLAN, a number of security
   mechanisms on link layer make MAC address a strong enough binding
   anchor, for instance, 802.11i, WAPI, WEP.

   If MAC address has no protection, attackers can spoof MAC address to
   succeed in validation.  However, in general cases, if MAC address is
   not protected, more serious attack can be launched than IP spoofing
   attack.








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3.3.  Binding IP addresses to MAC addresses

   All the static IP-MAC address pairs are configured into the IP-MAC
   Mapping Table with the mechanism enabled.

   An individual procedure handles binding DHCP addresses to MAC
   addresses.  This procedure snoops the DHCP address assignment
   procedure between attached hosts and DHCP server.  DHCP snooping in
   WLAN is the same as that in wired network specified in RFC7513
   [RFC7513].

   An individual procedure handles binding stateless addresses to MAC
   addresses.  This procedure snoops Duplicate Address Detection
   procedure.  ND snooping in WLAN is the same as that in wired network
   specified in [RFC6620] [RFC6620].

   Data packets MAY also trigger the establishment of new IP-MAC binding
   entries.  Data packet with non-bound source IP address with a limited
   rate is collected to handle DAD message loss in SLAAC procedure,
   which can be quite frequent in wireless network.  The detail of the
   procedure is specified in Section 4.  However, this mechanism will
   bring potential security risks (e.g. attacks that aimed at exhausting
   available IP addresses).  Thus, it is optional whether to enable the
   mechanism, and if it is enabled, additional security mechanisms MUST
   also be employed to cope with the risks.  Related security
   considerations are discussed in Section 6.

   In some deployment scenarios, the function of address snooping and
   IP-MAC table maintaining may also be separated onto different
   devices.  Thus to prevent conflictions in binding entries, the device
   snoops addresses must have interactions with the device maintains the
   IP-MAC table.  We will specify the details in Section 5.1.1.

3.4.  Binding Migration

   Different from wired network, SAVI for WLAN must handle migration of
   binding entries when mobile hosts move from one access point to
   another.  After movement, hosts will not perform another address
   allocation procedure to obtain new IP addresses, but continue to use
   the existing IP address.  Thus binding entries in the foreign device
   that the mobile hosts access to cannot be established by snooping.  A
   new mechanism is needed to correctly migrate the binding entry
   related to the IP address of the mobile host from the home device to
   the foreign device.  We will specify the details in Section 5,
   according to different deployment scenarios.






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3.5.  Binding Clearing

   Three kinds of events will trigger binding clearing:

   1.  The lifetime of an IP address in one entry has expired.  This IP
       entry in IP-MAC mapping table and corresponding entries in MAC-IP
       mapping table MUST be cleared.

   2.  A host leaves this access point.  The entries for all related MAC
       addresses in MAC-IP table MUST be cleared.

   3.  A DHCP RELEASE message is received from the owner of
       corresponding IP address.  This IP entry in IP-MAC mapping table
       and corresponding entries in MAC-IP mapping table MUST be
       cleared.

4.  Source Address Validation

   This section describes source address validation procedure on packet.
   In this procedure, all the frames are assumed to have passed the
   verifications of 802.11i or other security mechanisms.

   This procedure has the following steps:

   1.  Extract the IP source and MAC source from the frame.  Lookup the
       MAC address in the MAC-IP Mapping Table and check if the MAC-IP
       pair exists.  If yes, forward the packet.  Or else go to step 2.

   2.  Lookup the IP address in the IP-MAC Mapping Table and check if
       the IP address exists.  If no, go to step 3.  If yes, check
       whether The MAC address in the entry is the same as that in the
       frame.  If yes, forward the packet.  Else drop the packet.

   3.  If the mechanism that allows data packets to trigger the
       establishment of new IP-MAC binding entries is enabled, insert a
       new entry into the IP-MAC Mapping Table and forward the packet.
       Otherwise drop the packet.

   In step 2, after the packet is judged valid and forwarded,
   synchronization between the MAC-IP and IP-MAC mapping table should be
   triggered.  The MAC-IP binding of the packet should be synchronized
   from IP-MAC mapping table to MAC-IP mapping table and thus the
   following packets with the same MAC-IP pair will be forwarded without
   going to step 2.

   Also in step 3, if a new IP-MAC binding entry is established, it
   should be synchronized to MAC-IP mapping table.




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5.  Deployment Scenarios

   This section specifies three deployment scenarios including two under
   centralized WLAN and one under autonomous WLAN.  The deployment
   details and solutions for host mobility between access points are
   described respectively in each scenario.

5.1.  Centralized WLAN

   Centralized WLAN is comprised of FIT Access Points (AP) and Access
   Controllers (AC).  In this scenario, this document proposes the
   following two deployment solutions.

5.1.1.  AP Filtering

   With this deployment solution, data packets received by the APs do
   not go through the ACs and only control packets (including
   questionable data packets) go through the ACs.  In this scenario, AC
   maintains IP-MAC Mapping Table while AP maintains MAC-IP Mapping
   Table and perform address snooping.

5.1.1.1.  Candidate Binding

   AP executes the procedure specified in Section 3.3.  Candidate
   binding is generated after snooping procedure.  Candidate binding
   must be confirmed by AC to be valid.

   After a candidate binding is generated, AC is notified and checks
   whether the binding is valid or not.  The validity of a candidate
   binding is determined if the binding does not violate any existing
   bindings in the IP-MAC Mapping Table.  Otherwise if an address is not
   suitable for a host to use, AC notifies the corresponding AP.  If the
   candidate binding is valid, AC adds an entry into the IP-MAC Mapping
   Table and notifies AP.  Afterwards AP also adds an entry into the
   local MAC-IP Mapping Table.

5.1.1.2.  Packet Filtering

   As specified in Section 4, for incoming data packets, AP looks up the
   MAC address in the local MAC-IP Mapping Table and check if the MAC-IP
   pair exists.  If yes, AP forwards the packet.  Or else AP delivers
   the packet to AC for further processing.

   When receiving data packets from AP, AC Looks up the IP address in
   the local IP-MAC Mapping Table and checks if the IP address exists.
   If no, according to whether the AC is configured to allow data
   packets to trigger binding entry creations, AC establishes a new IP-
   MAC entry then forwards the packet, or drop the packet.  If yes, AC



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   checks whether The MAC address in the entry is the same as that in
   the frame.  If yes, AC forwards the packet.  Else AC drops the
   packet.

   After AC forwards a valid packet, it synchronizes related MAC-IP
   binding to the MAC-IP mapping table on the AP from which the packet
   comes.  Following packets with the same MAC-IP pair will be forwarded
   directly by AP without going to AC.

5.1.1.3.  Negative Entries

   In the AP Filtering scenario, APs MAY drop packets directly without
   sending them to AC by enabling the establishment of negative entries
   on APs.  Specifically, APs may establish negative entries in the
   following circumstances.

   1.  When AP receives a certain amount of packets within a certain
       amount of time with the same MAC-IP pair that does not exist in
       the local MAC-IP Table, it establishes a negative entry for this
       MAC-IP pair.  Then AP drops all following packets that have the
       same MAC-IP pair as indicated in this negative entry without
       sending them to AC for further processing.

   2.  When AP receives a certain amount of packets within a certain
       amount of time with the same MAC address but different MAC-IP
       pairs and none of these MAC-IP pairs exist in the local MAC-IP
       Table, it establishes a negative entry for this MAC address.
       Then AP drops all following packets that have the same MAC
       address as indicated in this negative entry without sending them
       to AC for further processing.

   Each negative entry has a limited lifetime.  The number of packets
   and duration of time to trigger the establishment of the negative
   entry, and the lifetime of the negative entry are configurable.

5.1.1.4.  CAPWAP Extension

   CAPWAP protocol is used for communication between AP and AC.  A new
   CAPWAP protocol message element is introduced, which extends RFC5415
   [RFC5415].  The host IP message element is used by both AP and AC to
   exchange the binding information of hosts.

   The host IP message element can be used in the process of
   confirmation of candidate binding.  When AP generates a candidate
   binding, it reports the MAC address and related IP addresses to AC
   using this message, with suggestions of the state and lifetime of
   each IP address as specified in Section 3.1.1.  After AC checks the
   validation of the candidate binding, it replies using a message of



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   the same format to inform AP the validation of each IP address with
   suggestions of its state and lifetime.

   The host IP message element can be used in the process of binding
   migration.  When migration happens, the source device reports the MAC
   address and related IP addresses to the destination device using this
   message, with suggestions of the state and lifetime of each IP
   address as specified in Section 3.1.1.  After the destination device
   checks the validation of the candidate binding, it replies using a
   message of the same format to inform the source device the validation
   of each IP address with suggestions of its state and lifetime.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Radio ID   |                 Total Length                  +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Sender ID   |     Length    |         Description           +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    MAC flag   |     Length    |        MAC Address...         +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     MAC Address...                            +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    IPv4 flag  |     Length    |        blank       ...        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 Address 1(32 bit)                     +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 Address 2(32 bit)                     +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    ........                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 Address n(32 bit)                     +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    IPv6 flag  |     Length    |        IPv6 Address...        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv6 Address 1(128 bit)                    +



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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv6 Address 2(128 bit)                    +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    ........                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv6 Address n(128 bit)                    +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    State      |        blank       ...                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    lifetime                                   +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Radio ID: An 8-bit value representing the radio, whose value is
   between 1 and 31.

   Total Length: Total length of the following fields.

   Sender ID: An 8-bit value representing the sender of the message.  AP
   is represented by value 1 and AC is represented by value 2.

   Length: The length of the Value field.

   Description: A 16-bit value for descriptions of the sender (AP or
   AC).

   MAC flag: An 8-bit value representing that the sub-field's type is
   MAC address, whose value is 1.

   Length: The length of the MAC Address field.  The formats and lengths
   specified in EUI-48 [EUI-48] and EUI-64 [EUI-64] are supported.

   MAC Address: A MAC address of the host.  At least one MAC address
   block MUST appear in the message, otherwise the message is considered
   as invalid.

   IPv4 flag: An 8-bit value representing that the sub-field's type is
   IPv4 address, whose value is 2.

   Length: The length of the IPv4 Address field.




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   IPv4 Address: An IPv4 address of the host.  There may exist many
   entries, and each entry is comprised of an IPv4 address, an 8-bit
   value for address state (value 1 means available, value 0 means
   obsoluted), and a 32-bit value for lifetime.  It is required to list
   all IPv4 addresses before IPv6 address blocks.

   IPv6 flag: An 8-bit value representing that the sub-field's type is
   IPv6 address, whose value is 3.

   Length: The length of the IPv6 Address field.

   IPv6 Address: An IPv6 address of the host.  There may exist many
   entries, and each entry is comprised of an IPv6 address, an 8-bit
   value of address state (value 1 means available, value 0 means
   obsoluted), and a 32-bit value lifetime.  All IPv4 and IPv6 addresses
   bind to the MAC address that appears before them in the message.

5.1.1.5.  Mobility Solution

   When a host moves from one AP to another, layer-2 association happens
   before IP packet transfer.  Home AP deletes the binding when mobile
   host is disconnected, and foreign AP immediately requests the bound
   addresses with the associated MAC from AC.  AC returns the binding
   with suggestions of its state and lifetime.  After AP get the
   addresses should be bound, the binding migration is completed.  The
   protocol used for communication between foreign AP and AC is the same
   as described in Section 5.1.1.3, while in this scenario AC serves the
   role of the source device and foreign AP serves the role of the
   destination device.

   In WLAN, a host can move from an AC to another AC while keeping using
   the same IP address.  To be compatible with such scenario, ACs must
   communicate to perform the binding migration.  The protocol used for
   communication between ACs is the same as described in
   Section 5.1.1.3, while in this scenario home AC serves the role of
   the source device and foreign AC serves the role of the destination
   device.

5.1.2.  AC Filtering

   In this scenario, AC maintains both MAC-IP and IP-MAC Mapping
   Table and performs both address snooping and packet filtering.  So
   all the packets must be forwarded to AC firstly.

   AC executes the procedure specified in Section 3.3 and check the
   validity of IP-MAC pairs by consulting the local IP-MAC mapping
   table.  No extra procedure is needed to establish the IP-MAC
   bindings.



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   AC executes the procedure specified in Section 4 for packet filtering
   and no extra procedure is involved.

   Mobility within one AC does not trigger any binding migration.
   Mobility between different ACs triggers binding migration.  ACs must
   communicate to perform the binding migration.  The protocol used for
   communication between ACs is the same as described in
   Section 5.1.1.3, while in this scenario home AC serves the role of
   the source device and foreign AC serves the role of the destination
   device.

5.2.  Autonomous WLAN

   Autonomous WLAN is comprised of FAT Access Points.  In this scenario,
   FAT AP maintains both MAC-IP and IP-MAC Mapping Table and performs
   both address snooping and packet filtering.

   FAT AP executes the procedure specified in Section 3.3 and check the
   validity of IP-MAC pairs by consulting the local IP-MAC mapping
   table.  No extra procedure is needed to establish the IP-MAC
   bindings.

   FAT AP executes the procedure specified in Section 4 for packet
   filtering and no extra procedure is involved.

   Mobility between different FAT APs will trigger binding migration.
   FAT APs must communicate to perform the binding migration.  The
   protocol used for communication between FAT APs is the same as
   described in Section 5.1.1.3, while in this scenario home FAT AP
   serves the role of the source device and foreign FAT AP serves the
   role of the destination device.

6.  IANA Considerations

   There is no IANA Consideration currently.

7.  Security Considerations

   The security of address allocation methods matters the security of
   this mechanism.  Thus it is necessary to improve the security of
   stateless auto-configuration and DHCP firstly.

7.1.  Issues with Triggerring Establishment of Binding Entries by Data
      Packets

   In Section 3.3, a mechanism is described to allow data packets to
   trigger the establishment of new binding entries.  If the mechanism
   is enabled, it can be used to launch attacks which may finally leads



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   to exhaustion of available IP addresses.  If no restriction is taken,
   the attacker can make as many IP-MAC bindings as possible with the
   same MAC address.  In this way, other hosts may fail to trigger any
   binding entry establishment and thus cannot get their packets pass
   the SAVI device.  To cope with the potential security risks,
   additional mechanism MUST be employed, e.g. to limit the maximum
   number of IP addresses that one MAC address can bind to.

7.2.  Privacy Considerations

   A SAVI device MUST delete binding anchor information as soon as
   possible, except where there is an identified reason why that
   information is likely to be involved in the detection, prevention, or
   tracing of actual source-address spoofing.  Information about hosts
   that never spoof (probably the majority of hosts) SHOULD NOT be
   logged.

8.  Acknowledgements

   The authors would like to thank Guang Yao, Yang Shi and Hao Wang for
   their contributions to this document.

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.

   [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, <https://www.rfc-editor.org/info/rfc3315>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, DOI 10.17487/
              RFC4862, September 2007, <https://www.rfc-editor.org/info/
              rfc4862>.

   [RFC5415]  Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
              Ed., "Control And Provisioning of Wireless Access Points
              (CAPWAP) Protocol Specification", RFC 5415, DOI 10.17487/
              RFC5415, March 2009, <https://www.rfc-editor.org/info/
              rfc5415>.







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   [RFC6620]  Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS
              SAVI: First-Come, First-Served Source Address Validation
              Improvement for Locally Assigned IPv6 Addresses", RFC
              6620, DOI 10.17487/RFC6620, May 2012, <https://www.rfc-
              editor.org/info/rfc6620>.

   [RFC7513]  Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address
              Validation Improvement (SAVI) Solution for DHCP", RFC
              7513, DOI 10.17487/RFC7513, May 2015, <https://www.rfc-
              editor.org/info/rfc7513>.

9.2.  Informative References

   [EUI-48]   "Guidelines For 48-bit Global Identifier (EUI-48)",
              http://standards.ieee.org/develop/regauth/tut/eui48.pdf

   [EUI-64]   "Guidelines For 64-bit Global Identifier (EUI-64)",
              http://standards.ieee.org/develop/regauth/tut/eui64.pdf

Authors' Addresses

   Jun Bi
   Tsinghua University
   Network Research Center, Tsinghua University
   Beijing  100084
   China

   Email: junbi@cernet.edu.cn


   Jianping Wu
   Tsinghua University
   Computer Science, Tsinghua University
   Beijing  100084
   China

   Email: jianping@cernet.edu.cn


   You Wang
   Tsinghua University
   Network Research Center, Tsinghua University
   Beijing  100084
   China

   Email: wangyou10@mails.tsinghua.edu.cn





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   Tao Lin
   New H3C Technologies Co. Ltd
   466 Changhe Road, Binjiang District
   Hangzhou, Zhejiang Province  310052
   China

   Email: lintao@h3c.com












































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