Source Address Validation Improvements (SAVI) J. Bi Internet-Draft J. Wu Intended status: Standards Track Tsinghua University Expires: May 14, 2022 T. Lin New H3C Technologies Co. Ltd Y. Wang L. He Tsinghua University November 10, 2021 A SAVI Solution for WLAN draft-bi-savi-wlan-22 Abstract This document describes a source address validation solution for WLANs where 802.11i or other security mechanisms are enabled to secure MAC addresses. This mechanism snoops NDP and DHCP packets to bind IP addresses to MAC addresses, and relies on the security of MAC addresses 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 https://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 May 14, 2022. Bi, et al. Expires May 14, 2022 [Page 1] Internet-Draft savi-wlan November 2021 Copyright Notice Copyright (c) 2021 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 (https://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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. IP-MAC Binding . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Data Structures . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. IP-MAC Mapping Table . . . . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . 5 4. Source Address Validation . . . . . . . . . . . . . . . . . . 6 5. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . 6 5.1. Centralized WLAN . . . . . . . . . . . . . . . . . . . . 7 5.1.1. AP Filtering . . . . . . . . . . . . . . . . . . . . 7 5.1.1.1. Candidate Binding . . . . . . . . . . . . . . . . 7 5.1.1.2. Packet Filtering . . . . . . . . . . . . . . . . 7 5.1.1.3. Negative Entries . . . . . . . . . . . . . . . . 8 5.1.1.4. CAPWAP Extension . . . . . . . . . . . . . . . . 8 5.1.1.5. Mobility Solution . . . . . . . . . . . . . . . . 11 5.1.2. AC Filtering . . . . . . . . . . . . . . . . . . . . 12 5.2. Autonomous WLAN . . . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7.1. Privacy Considerations . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Bi, et al. Expires May 14, 2022 [Page 2] Internet-Draft savi-wlan November 2021 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 addresses with authenticated MAC addresses. Static addresses are bound to the MAC addresses of corresponding hosts manually. Then the mechanism can check the validity of the source IP addresses in local packets according to the binding association. The security of MAC address is assured by 802.11i or other mechanisms, thus the binding association is secure. IP-MAC binding table in control plane and MAC-IP binding table in data plane are two important data structures, which are introduced in detail in the document. The situation that one interface 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 details are 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. Familiarity with SAVI-DHCP and its terminology, as defined in [RFC7513], is assumed. 2. Requirements Language 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]. Bi, et al. Expires May 14, 2022 [Page 3] Internet-Draft savi-wlan November 2021 3. IP-MAC Binding This section specifies the operations for creating and clearing bindings between IP addresses and 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 the control process. Before creating new IP- MAC bindings, this table must first be consulted in case of conflicts in binding entries. Also, this table must be consulted before doing any 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. The addresses snooped in DHCP address assignment procedure must record their state as "DHCPv6", and the addresses snooped in Duplicate Address Detection procedure must record their state as "SLAAC". 3.1.2. MAC-IP Mapping Table This table maps MAC addresses to the 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, 802.11i or other security mechanisms on link layer make MAC address a strong enough binding anchor. Bi, et al. Expires May 14, 2022 [Page 4] Internet-Draft savi-wlan November 2021 If MAC address has no protection, attackers can spoof MAC address to succeed in validation. 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 the binding of DHCP addresses to MAC addresses. This procedure snoops the DHCP address assignment process between attached hosts and DHCP server. DHCP snooping in WLANs is the same as that in wired networks specified in [RFC7513]. An individual procedure handles the binding of stateless addresses to MAC addresses. This procedure snoops Address Resolution procedure between attached hosts and neighbors as described in [RFC4861] or Duplicate Address Detection procedure as described in [RFC4862]. Based on the principle of roaming experience first in WLAN, the new binding anchor is preferred, and removing the security connection of the old binding anchor is triggered. In some deployment scenarios, the functions of address snooping and IP-MAC table maintenance may also be separated onto different devices. Thus, to prevent conflicts in binding entries, the device for address snooping must interact with the device that 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 the migration of binding entries when a mobile host moves from one access point to another. After the movement, the host will not perform another address allocation procedure to obtain new IP addresses, but continue to use the existing IP address(es). 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. If the host binds multiple entries, multiple entries will be migrated. For example, when the host is assigned multiple addresses, multiple binding entries will be generated, and these entries will be migrated. We will specify the details in Section 5, according to different deployment scenarios. 3.5. Binding Clearing Three kinds of events will trigger binding clearing: Bi, et al. Expires May 14, 2022 [Page 5] Internet-Draft savi-wlan November 2021 1. A host leaves explicitly this access point. The entries for all related MAC addresses in MAC-IP table MUST be cleared. 2. A DHCP RELEASE message is received from the owner of the corresponding IP address. This IP entry in IP-MAC mapping table and the corresponding entries in MAC-IP mapping table MUST be cleared. 3. A timeout message of AC's client idle-time is received. The entries for all related MAC addresses in MAC-IP table MUST be cleared. 4. Source Address Validation This section describes source address validation procedure on packets. 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. Otherwise, go to step 2. 2. Look up the IP address in the IP-MAC Mapping Table and check if the IP address exists. If not, 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. Otherwise, drop the packet. In step 2, after the packet is judged to be valid and forwarded, synchronization between the MAC-IP and IP-MAC mapping tables 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. 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 for each scenario. Bi, et al. Expires May 14, 2022 [Page 6] Internet-Draft savi-wlan November 2021 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, the validated data packets received by an AP do not go through the AC, and only control packets and the questionable data packets go through the AC. In this scenario, the AC maintains IP-MAC Mapping Table, while the AP maintains MAC-IP Mapping Table and performs address snooping. 5.1.1.1. Candidate Binding An AP executes the procedure specified in Section 3.3. The candidate bindings are generated after snooping procedure. Candidate bindings must be confirmed by the AC to be valid. After a candidate binding is generated, the 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, the AC notifies the corresponding AP. If the candidate binding is valid, the AC adds an entry into the IP- MAC Mapping Table and notifies the AP. Afterwards, the 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, an AP looks up the MAC address in the local MAC-IP Mapping Table and checks if the MAC-IP pair exists. If yes, the AP forwards the packet. Otherwise, the AP delivers the packet to the AC for further processing. When receiving a data packet from the AP, the AC looks up the IP address in the local IP-MAC Mapping Table and checks if the IP address exists. If not, the AC drops the packet. If yes, the AC checks whether the MAC address in the entry is the same as that in the frame. If yes, the AC forwards the packet. Otherwise, the AC drops the packet. After the AC forwards a valid packet, it synchronizes the 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 the AP without going to the AC. Bi, et al. Expires May 14, 2022 [Page 7] Internet-Draft savi-wlan November 2021 5.1.1.3. Negative Entries In the AP Filtering scenario, APs MAY drop packets directly without sending them to the AC by enabling the establishment of negative entries on APs. Specifically, APs may establish negative entries in the following circumstances. 1. When an AP receives a certain number 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 the AP drops all following packets that have the same MAC-IP pair as indicated in this negative entry without sending them to the AC for further processing. 2. When an AP receives a certain number 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 the AP drops all following packets that have the same MAC address as indicated in this negative entry without sending them to the 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 the AP and the AC. A new CAPWAP protocol message element is introduced, which extends [RFC5415]. The host IP message element is used by both the AP and the AC to exchange the binding information of hosts. The host IP message element can be used in the process of confirmation of candidate bindings. When the AP generates a candidate binding, it reports the MAC address and related IP addresses to the AC using this message, with suggestions of the state of each IP address as specified in Section 3.1.1. After the AC checks the validation of the candidate binding, it replies using a message of the same format to inform the AP of the validation of each IP address with a suggested state. The host IP message element can be used in the process of binding migration. When migration happens, the source device uses this message to report the MAC address and related IP addresses to the destination device, with suggestions for the state 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 Bi, et al. Expires May 14, 2022 [Page 8] Internet-Draft savi-wlan November 2021 of the same format to inform the source device the validation of each IP address with a suggested state. The host IP message element can also be used in other scenarios when the synchronization between MAC-IP and IP-MAC tables is required as specified in Section 3.5 and Section 4. When the synchronization from IP-MAC table to MAC-IP table is triggered, the source device which holds the IP-MAC table reports the MAC address and the related IP addresses to the destination device which holds the MAC-IP table using this message, with suggestions of the state of each IP address as specified in Section 3.1.1. The destination device replies using a message of the same format to acknowledge the source device. 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... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Bi, et al. Expires May 14, 2022 [Page 9] Internet-Draft savi-wlan November 2021 | IPv6 Address 1(128 bit) + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | blank ... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | lifetime + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 Address 2(128 bit) + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | blank ... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | lifetime + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ........ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 Address n(128 bit) + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | blank ... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | lifetime + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BSSID flag | Length | BSSID... + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BSSID + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 a description 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 and EUI-64 [EUI] 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. Bi, et al. Expires May 14, 2022 [Page 10] Internet-Draft savi-wlan November 2021 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. 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 unavailable, value 255 means candidate), and a 32-bit value for lifetime. Lifetime is a reserved field for future application under abnormal conditions. 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, a DHCPv6-assigned IP address represented by value 3 and a locally assigned IP address represented by value 4. 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 unavailable, value 255 means candidate), and a 32-bit value lifetime. Lifetime is a reserved field for future application under abnormal conditions. All IPv4 and IPv6 addresses bind to the MAC address that appears before them in the message. BSSID flag: An 8-bit value representing that the sub-field's type is BSSID, whose value is 5. Length: The length of the BSSID field. The formats and lengths specified in EUI-48 and EUI-64 [EUI] are supported. BSSID: A basic service set identifier representing the BSS. 5.1.1.5. Mobility Solution When a host moves from one AP to another, layer-2 association happens before the IP packets are forwarded. The home AP deletes the binding when mobile host is disconnected, and the foreign AP immediately requests the bound addresses with the associated MAC from the AC. The AC returns the binding with a suggested state. After the foreign AP get the addresses should be bound, the binding migration is completed. The protocol used for communication between the foreign AP and the AC is the same as described in Section 5.1.1.4, while in this scenario, the AC serves the role of the source device and the foreign AP serves the role of the destination device. Bi, et al. Expires May 14, 2022 [Page 11] Internet-Draft savi-wlan November 2021 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 5.1.1.4, while in this scenario the home AC serves the role of the source device and the foreign AC serves the role of the destination device. 5.1.2. AC Filtering In this scenario, an 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 the AC first. The AC executes the procedure specified in Section 3.3 and checks 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. The 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 5.1.1.4, while in this scenario the home AC serves the role of the source device and the foreign AC serves the role of the destination device. 5.2. Autonomous WLAN Autonomous WLAN is comprised of FAT Access Points. In this scenario, a FAT AP maintains both MAC-IP and IP-MAC Mapping Table and performs both address snooping and packet filtering. The FAT AP executes the procedure specified in Section 3.3 and checks 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. The 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 5.1.1.4, while in this scenario the home FAT AP Bi, et al. Expires May 14, 2022 [Page 12] Internet-Draft savi-wlan November 2021 serves the role of the source device and the 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 first. 7.1. 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, DOI 10.17487/RFC2119, March 1997, . 9.2. Informative References [EUI] IEEE Standards Association, "Guidelines for Use of Extended Unique Identifier (EUI), Organizationally Unique Identifier (OUI), and Company ID (CID)", 2017, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . Bi, et al. Expires May 14, 2022 [Page 13] Internet-Draft savi-wlan November 2021 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . [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, . [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, . Authors' Addresses Jun Bi Tsinghua University Beijing 100084 China Email: junbi@cernet.edu.cn Jianping Wu Tsinghua University Beijing 100084 China Email: jianping@cernet.edu.cn Tao Lin New H3C Technologies Co. Ltd 466 Changhe Road, Binjiang District Hangzhou, Zhejiang 310052 China Email: lintao@h3c.com Bi, et al. Expires May 14, 2022 [Page 14] Internet-Draft savi-wlan November 2021 You Wang Tsinghua University Beijing 100084 China Email: you@opennetworking.org Lin He Tsinghua University Beijing 100084 China Email: he-l14@mails.tsinghua.edu.cn Bi, et al. Expires May 14, 2022 [Page 15]