Network Working Group F. Templin, Ed. Internet-Draft Boeing Research & Technology Obsoletes: rfc6706 (if approved) August 15, 2014 Intended status: Standards Track Expires: February 16, 2015 Transmission of IP Packets over AERO Links draft-templin-aerolink-31.txt Abstract This document specifies the operation of IP over tunnel virtual links using Asymmetric Extended Route Optimization (AERO). Nodes attached to AERO links can exchange packets via trusted intermediate routers that provide forwarding services to reach off-link destinations and redirection services for route optimization. AERO provides an IPv6 link-local address format known as the AERO address that supports operation of the IPv6 Neighbor Discovery (ND) protocol and links IPv6 ND to IP forwarding. Admission control and provisioning are supported by the Dynamic Host Configuration Protocol for IPv6 (DHCPv6), and node mobility is naturally supported through dynamic neighbor cache updates. Although DHCPv6 and IPv6 ND messaging is used in the control plane, both IPv4 and IPv6 are supported in the data plane. 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 February 16, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. Templin Expires February 16, 2015 [Page 1]
Internet-Draft AERO August 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Asymmetric Extended Route Optimization (AERO) . . . . . . . . 5 3.1. AERO Link Reference Model . . . . . . . . . . . . . . . . 5 3.2. AERO Node Types . . . . . . . . . . . . . . . . . . . . . 7 3.3. AERO Addresses . . . . . . . . . . . . . . . . . . . . . 8 3.4. AERO Interface Characteristics . . . . . . . . . . . . . 9 3.4.1. Coordination of Multiple Underlying Interfaces . . . 11 3.5. AERO Interface Neighbor Cache Maintenace . . . . . . . . 12 3.6. AERO Interface Sending Algorithm . . . . . . . . . . . . 13 3.7. AERO Interface Encapsulation, Re-encapsulation and Decapsulation . . . . . . . . . . . . . . . . . . . . . . 15 3.8. AERO Interface Data Origin Authentication . . . . . . . . 16 3.9. AERO Interface MTU Considerations . . . . . . . . . . . . 16 3.10. AERO Router Discovery, Prefix Delegation and Address Configuration . . . . . . . . . . . . . . . . . . . . . . 18 3.10.1. AERO DHCPv6 Service Model . . . . . . . . . . . . . 18 3.10.2. AERO Client Behavior . . . . . . . . . . . . . . . . 19 3.10.3. AERO Server Behavior . . . . . . . . . . . . . . . . 20 3.11. AERO Relay/Server Routing System . . . . . . . . . . . . 22 3.12. AERO Redirection . . . . . . . . . . . . . . . . . . . . 22 3.12.1. Reference Operational Scenario . . . . . . . . . . . 22 3.12.2. Concept of Operations . . . . . . . . . . . . . . . 24 3.12.3. Message Format . . . . . . . . . . . . . . . . . . . 24 3.12.4. Sending Predirects . . . . . . . . . . . . . . . . . 25 3.12.5. Re-encapsulating and Relaying Predirects . . . . . . 26 3.12.6. Processing Predirects and Sending Redirects . . . . 27 3.12.7. Re-encapsulating and Relaying Redirects . . . . . . 29 3.12.8. Processing Redirects . . . . . . . . . . . . . . . . 29 3.12.9. Server-Oriented Redirection . . . . . . . . . . . . 30 3.13. Neighbor Unreachability Detection (NUD) . . . . . . . . . 30 3.14. Mobility Management . . . . . . . . . . . . . . . . . . . 31 3.14.1. Announcing Link-Layer Address Changes . . . . . . . 31 3.14.2. Moving to a New Server . . . . . . . . . . . . . . . 33 3.15. Encapsulation Protocol Version Considerations . . . . . . 33 3.16. Multicast Considerations . . . . . . . . . . . . . . . . 33 Templin Expires February 16, 2015 [Page 2]
Internet-Draft AERO August 2014 3.17. Operation on AERO Links Without DHCPv6 Services . . . . . 34 3.18. Operation on Server-less AERO Links . . . . . . . . . . . 34 4. Implementation Status . . . . . . . . . . . . . . . . . . . . 34 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34 6. Security Considerations . . . . . . . . . . . . . . . . . . . 34 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 35 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 8.1. Normative References . . . . . . . . . . . . . . . . . . 36 8.2. Informative References . . . . . . . . . . . . . . . . . 37 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 39 1. Introduction This document specifies the operation of IP over tunnel virtual links using Asymmetric Extended Route Optimization (AERO). The AERO link can be used for tunneling to neighboring nodes over either IPv6 or IPv4 networks, i.e., AERO views the IPv6 and IPv4 networks as equivalent links for tunneling. Nodes attached to AERO links can exchange packets via trusted intermediate routers that provide forwarding services to reach off-link destinations and redirection services for route optimization that addresses the requirements outlined in [RFC5522]. AERO provides an IPv6 link-local address format known as the AERO address that supports operation of the IPv6 Neighbor Discovery (ND) [RFC4861] protocol and links IPv6 ND to IP forwarding. Admission control and provisioning are supported by the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315], and node mobility is naturally supported through dynamic neighbor cache updates. Although DHCPv6 and IPv6 ND message signalling is used in the control plane, either of IPv4 and IPv6 can be used in the data plane. The remainder of this document presents the AERO specification. 2. Terminology The terminology in the normative references applies; the following terms are defined within the scope of this document: AERO link a Non-Broadcast, Multiple Access (NBMA) tunnel virtual overlay configured over a node's attached IPv6 and/or IPv4 networks. All nodes on the AERO link appear as single-hop neighbors from the perspective of the virtual overlay. AERO interface a node's attachment to an AERO link. AERO address Templin Expires February 16, 2015 [Page 3]
Internet-Draft AERO August 2014 an IPv6 link-local address constructed as specified in Section 3.2 and applied to a Client's AERO interface. AERO node a node that is connected to an AERO link and that participates in IPv6 ND over the link. AERO Client ("Client") a node that applies an AERO address to an AERO interface and receives an IP prefix delegation. AERO Server ("Server") a node that configures an AERO interface to provide default forwarding and DHCPv6 services for AERO Clients. The Server applies the IPv6 link-local subnet router anycast address (fe80::) to the AERO interface and also applies an administratively assigned IPv6 link-local unicast address used for operation of the IPv6 ND protocol. AERO Relay ("Relay") a node that configures an AERO interface to relay IP packets between nodes on the same AERO link and/or forward IP packets between the AERO link and the native Internetwork. The Relay applies an administratively assigned IPv6 link-local unicast address to the AERO interface the same as for a Server. ingress tunnel endpoint (ITE) an AERO interface endpoint that injects tunneled packets into an AERO link. egress tunnel endpoint (ETE) an AERO interface endpoint that receives tunneled packets from an AERO link. underlying network a connected IPv6 or IPv4 network routing region over which the tunnel virtual overlay is configured. underlying interface an AERO node's interface point of attachment to an underlying network. link-layer address an IP address assigned to an AERO node's underlying interface. When UDP encapsulation is used, the UDP port number is also considered as part of the link-layer address. Link-layer addresses are used as the encapsulation header source and destination addresses. Templin Expires February 16, 2015 [Page 4]
Internet-Draft AERO August 2014 network layer address the source or destination address of the encapsulated IP packet. end user network (EUN) an internal virtual or external edge IP network that an AERO Client connects to the rest of the network via the AERO interface. AERO Service Prefix (ASP) an IP prefix associated with the AERO link and from which AERO Client Prefixes (ACPs) are derived (for example, the IPv6 ACP 2001:db8:1:2::/64 is derived from the IPv6 ASP 2001:db8::/32). AERO Client Prefix (ACP) a more-specific IP prefix taken from an ASP and delegated to a Client. Throughout the document, the simple terms "Client", "Server" and "Relay" refer to "AERO Client", "AERO Server" and "AERO Relay", respectively. Capitalization is used to distinguish these terms from DHCPv6 client/server/relay. Throughout the document, it is said that an address is "applied" to an AERO interface since the address need not always be "assigned" to the interface in the traditional sense. However, the address must at least be bound to the interface in some fashion for operation of DHCPv6 and the IPv6 ND protocol. The terminology of [RFC4861] (including the names of node variables and protocol constants) applies to this document. Also throughout the document, the term "IP" is used to generically refer to either Internet Protocol version (i.e., IPv4 or IPv6). 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]. 3. Asymmetric Extended Route Optimization (AERO) The following sections specify the operation of IP over Asymmetric Extended Route Optimization (AERO) links: 3.1. AERO Link Reference Model Templin Expires February 16, 2015 [Page 5]
Internet-Draft AERO August 2014 .-(::::::::) .-(:::: IP ::::)-. (:: Internetwork ::) `-(::::::::::::)-' `-(::::::)-' | +--------------+ +------+-------+ +--------------+ |AERO Server S1| | AERO Relay R | |AERO Server S2| | (default->R) | |(C->S1; D->S2)| | (default->R) | | Nbr: A | +-------+------+ | Nbr: B | +-------+------+ | +------+-------+ | | | X---+---+-------------------+------------------+---+---X | AERO Link | +-----+--------+ +--------+-----+ |AERO Client A | |AERO Client B | | default->S1 | | default->S2 | +--------------+ +--------------+ .-. .-. ,-( _)-. ,-( _)-. .-(_ IP )-. .-(_ IP )-. (__ EUN ) (__ EUN ) `-(______)-' `-(______)-' | | +--------+ +--------+ | Host C | | Host D | +--------+ +--------+ Figure 1: AERO Link Reference Model Figure 1 above presents the AERO link reference model. In this model: o Relay R associates with Servers S1 and S2, and connects the link to the rest of the IP Internetwork o Servers S1 and S2 associate with Relay R and also act as default routers for their associated Clients A and B. They further serve as DHCPv6 servers for the delegation of ACPs taken from the AERO link's ASPs o Clients A and B associate with Servers S1 and S2, respectively and also act as default routers for their associated EUNs o Hosts C and D attach to the EUNs served by Clients A and B, respectively Templin Expires February 16, 2015 [Page 6]
Internet-Draft AERO August 2014 In this model, there may be many additional Relays, Servers and Clients. Each Server peers with each Relay in a dynamic routing protocol session to advertise its list of associated Clients. Each Relay advertises the ASPs for the AERO link into the native IP Internetwork and serves as a gateway between the AERO link and the Internetwork. Clients may associate with only a single Server or with multiple Servers, e.g., for fault tolerance and/or load balancing. 3.2. AERO Node Types AERO Relays relay packets between nodes connected to the same AERO link and also forward packets between the AERO link and the native Internetwork. The relaying process entails re-encapsulation of IP packets that were received from a first AERO node and are to be forwarded without modification to a second AERO node. AERO Relays present the AERO link to the native Internetwork as a set of one or more ASPs. AERO Servers provide default routing and DHCPv6 services to AERO Clients. AERO Servers configure a DHCPv6 server function to facilitate Prefix Delegation (PD) exchanges with AERO Clients. Each delegated prefix becomes an AERO Client Prefix (ACP) taken from an ASP. AERO Clients act as requesting routers to receive ACPs through DHCPv6 PD exchanges with AERO Servers over the AERO link. (Each Client MAY associate with a single Server or with multiple Servers.) Each IPv6 AERO Client receives at least a /64 IPv6 ACP, and may receive even shorter prefixes. Similarly, each IPv4 AERO Client receives at least a /32 IPv4 ACP (i.e., a singleton IPv4 address), and may receive even shorter prefixes. AERO Clients that act as routers sub-delegate portions of their ACPs to links on EUNs. End system applications on AERO Clients that act as routers bind to EUN interfaces (i.e., and not the AERO interface). AERO Clients that act as ordinary hosts assign one or more IP addresses from their ACPs to the AERO interface but DO NOT assign the ACP itself to the AERO interface. Instead, the Client assigns the ACP to a "black hole" route so that unused portions of the prefix are nullified. End system applications on AERO Clients that act as hosts bind directly to the AERO interface. Templin Expires February 16, 2015 [Page 7]
Internet-Draft AERO August 2014 3.3. AERO Addresses An AERO address is an IPv6 link-local address with an embedded ACP and applied to a Client's AERO interface. The AERO address is formed as follows: fe80::[ACP] For IPv6, the AERO address begins with the prefix fe80::/64 and includes in its interface identifier the base prefix taken from the Client's IPv6 ACP. The base prefix is determined by masking the ACP with the prefix length. For example, if the AERO Client receives the IPv6 ACP: 2001:db8:1000:2000::/56 it constructs its AERO address as: fe80::2001:db8:1000:2000 For IPv4, the AERO address is formed as an IPv4-mapped IPv6 address [RFC4291] that includes the base prefix taken from the Client's IPv4 ACP. For example, if the AERO Client receives the IPv4 ACP: 192.0.2.32/28 it constructs its AERO address as: fe80::FFFF:192.0.2.32 The AERO address remains stable as the Client moves between topological locations, i.e., even if its link-layer addresses change. NOTE: In some cases, prospective neighbors may not have a priori knowledge of the Client's ACP length and may therefore send initial IPv6 ND messages with an AERO destination address that matches the ACP but does not correspond to the base prefix. In that case, the Client MUST accept the address as equivalent to the base address, but then use the base address as the source address of any IPv6 ND message replies. For example, if the Client receives the IPv6 ACP 2001:db8:1000:2000::/56 then subsequently receives an IPv6 ND message with destination address fe80::2001:db8:1000:2001, it accepts the message but uses fe80::2001:db8:1000:2000 as the source address of any IPv6 ND replies. Templin Expires February 16, 2015 [Page 8]
Internet-Draft AERO August 2014 3.4. AERO Interface Characteristics AERO interfaces use IP-in-IPv6 encapsulation [RFC2473] to exchange tunneled packets with AERO neighbors attached to an underlying IPv6 network, and use IP-in-IPv4 encapsulation [RFC2003][RFC4213] to exchange tunneled packets with AERO neighbors attached to an underlying IPv4 network. AERO interfaces can also coordinate secured tunnel types such as IPsec [RFC4301] or TLS [RFC5246]. When Network Address Translator (NAT) traversal and/or filtering middlebox traversal may be necessary, a UDP header is further inserted immediately above the IP encapsulation header. AERO interfaces maintain a neighbor cache, and AERO Clients and Servers use an adaptation of standard unicast IPv6 ND messaging. AERO interfaces use unicast Neighbor Solicitation (NS), Neighbor Advertisement (NA), Router Solicitation (RS) and Router Advertisement (RA) messages the same as for any IPv6 link. AERO interfaces use two redirection message types -- the first known as a Predirect message and the second being the standard Redirect message (see Section 3.9). AERO links further use link-local-only addressing; hence, AERO nodes ignore any Prefix Information Options (PIOs) they may receive in RA messages. AERO interface ND messages include Target Link-Layer Address Options (TLLAOs) formatted as shown in Figure 2: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 2 | Length = 3 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | Preference | UDP Port Number (or 0) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-- --+ | | +-- IP Address --+ | | +-- --+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: AERO Target Link-Layer Address Option (TLLAO) Format In this format, Link ID is an integer value between 0 and 255 corresponding to an underlying interface of the target node, and Preference is an integer value between 0 and 255 indicating the Templin Expires February 16, 2015 [Page 9]
Internet-Draft AERO August 2014 node's preference for this underlying interface, with 0 being highest preference and 255 being lowest. UDP Port Number and IP Address are set to the addresses used by the target node when it sends encapsulated packets over the underlying interface. When no UDP encapsulation is used, UDP Port Number is set to 0. When the encapsulation IP address family is IPv4, IP Address is formed as an IPv4-mapped IPv6 address [RFC4291]. When a Relay enables an AERO interface, it applies an administratively assigned link-local address fe80::ID to the interface for communicating with Servers on the link. Each fe80::ID address MUST be unique among all Relays and Servers on the link, and MUST NOT collide with any potential AERO addresses, e.g., the addresses could be assigned as fe80::1, fe80::2, fe80::3, etc. The Relay also maintains an IP forwarding table entry for each Client- Server association and maintains a neighbor cache entry for each Server on the link. Relays do not require the use of IPv6 ND messaging for reachability determination since Relays and Servers engage in a dynamic routing protocol over the AERO interface. At a minimum, however, Relays respond to NS messages by returning an NA. When a Server enables an AERO interface, it applies the address fe80:: to the interface as a link-local Subnet Router Anycast address, and also applies an administratively assigned link-local address fe80::ID to support the operation of DHCPv6 and the IPv6 ND protocol, as well as to communicate with Relays on the link. The Server configures a DHCPv6 server function to facilitate DHCPv6 PD exchanges with AERO Clients. The Server also maintains a neighbor cache entry for each Relay on the link, and also creates per-Client neighbor cache entries whenever it discovers a new Client. At a minimum, when the Server receives an NS/RS messages on the AERO interface it returns an NA/RA message. When the Server receives an IPv6 ND message, it also update timers in existing neighbor cache entries but does not create new neighbor cache entries nor update cached link-layer addresses. Servers also engage in a dynamic routing protocol with all Relays on the link. Finally, the Server provides a simple conduit between Clients and Relays, or between Clients and other Clients. Therefore, packets enter the Server's AERO interface from the link layer and are forwarded back out the link layer without ever leaving the AERO interface and therefore without ever disturbing the network layer. When a Client enables an AERO interface, it invokes DHCPv6 PD to receive an ACP from an AERO Server. Next, it applies the corresponding AERO address to the AERO interface, i.e., the prefix delegation bootstraps the provisioning of a unique link-local address. The Client maintains a neighbor cache entry for each of its Servers and each of its active peer Clients. When the Client Templin Expires February 16, 2015 [Page 10]
Internet-Draft AERO August 2014 receives Redirect/Predirect messages on the AERO interface it updates or creates neighbor cache entries, including link-layer address information. Unsolicited NA messages update the cached link-layer address for the neighbor Client (e.g., following a link-layer address change due to node mobility) but do not create new neighbor cache entries. RA messages as well as NS/NA messages used for Neighbor Unreachability Detection (NUD) update timers in existing neighbor cache entires but do not update link-layer addresses nor create new neighbor cache entries. Redirect, Predirect and unsolicited NA messages SHOULD include a Timestamp option (see Section 5.3 of [RFC3971]) that other AERO nodes can use to verify the message time of origin. Predirect, NS and RS messages SHOULD include a Nonce option (see Section 5.3 of [RFC3971]) that recipients echo back in corresponding responses. Finally, the Client need not maintain any IP forwarding table entries for neighboring Clients. Instead, it can set a single "route-to-interface" default route in the IP forwarding table pointing to the AERO interface, and all forwarding decisions can be made within the AERO interface based on neighbor cache entries. 3.4.1. Coordination of Multiple Underlying Interfaces AERO interfaces may be configured over multiple underlying interfaces. For example, common mobile handheld devices have both wireless local area network ("WLAN") and cellular wireless links. These links are typically used "one at a time" with low-cost WLAN preferred and highly-available cellular wireless as a standby. In a more complex example, aircraft frequently have many wireless data link types (e.g. satellite-based, terrestrial, air-to-air directional, etc.) with diverse performance and cost properties. If a Client's multiple underlying interfaces are used "one at a time" (i.e., all other interfaces are in standby mode while one interface is active), then Redirect, Predirect and unsolicited NA messages include only a single TLLAO with Link ID set to 0. If the Client has multiple active underlying interfaces, then from the perspective of IPv6 ND it would appear to have a single link- local address with multiple link-layer addresses. In that case, Redirect, Predirect and unsolicited NA messages MAY include multiple TLLAOs -- each with a different Link ID that corresponds to a specific underlying interface of the Client. Further details on coordination of multiple active underlying interfaces are outside the scope of this specification. Templin Expires February 16, 2015 [Page 11]
Internet-Draft AERO August 2014 3.5. AERO Interface Neighbor Cache Maintenace Each AERO interface maintains a conceptual neighbor cache that includes an entry for each neighbor it communicates with on the AERO link, the same as for any IPv6 interface [RFC4861]. Neighbor cache entries are created and maintained as follows: AERO Relays maintain a permanent neighbor cache entry for each Server on the link, and AERO Servers maintain a permanent neighbor cache entry for each Relay on the link. AERO Clients maintain a neighbor cache entry for each of their associated Servers, and AERO Servers maintain a neighbor cache for each of their associated Clients with a lifetime based on the DHCPv6 lease lifetime. AERO Clients maintain neighbor cache entries for each of their active correspondent Clients with lifetimes based on IPv6 ND messaging constants. When an AERO Server sends a DHCPv6 Reply message to an AERO Client containing a prefix delegation, it creates or updates a neighbor cache entry for the Client based on the AERO address corresponding to the Client's ACP as the network-layer address and with the Client's encapsulation IP address and UDP port number as the link-layer address. The Server also records the ACP's lease lifetime and prefix length in the neighbor cache entry. When an AERO Client receives a DHCPv6 Reply message from an AERO Server, it creates or updates a neighbor cache entry for the Server based on the Reply message link-local source address as the network- layer address, the lease lifetime as the neighbor cache entry lifetime, and the encapsulation IP source address and UDP source port number as the link-layer address. When an AERO Client receives a valid Predirect message it creates or updates a neighbor cache entry for the Predirect target network-layer and link-layer addresses plus prefix length. The node then sets an "AcceptTime" variable for the neighbor and uses this value to determine whether packets received from the predirected neighbor can be accepted. When an AERO Client receives a valid Redirect message it creates or updates a neighbor cache entry for the Redirect target network-layer and link-layer addresses plus prefix length. The node then sets a "ForwardTime" variable for the neighbor and uses this value to determine whether packets can be sent directly to the redirected neighbor. The node also maintains a "Retry" variable to limit the number of keepalives sent when a neighbor may have gone unreachable. Templin Expires February 16, 2015 [Page 12]
Internet-Draft AERO August 2014 When an AERO Client receives a valid NS message corresponding to a neighbor cache entry for another Client, it (re)sets AcceptTime for the neighbor to ACCEPT_TIME. When an AERO Client receives a valid solicited NA message corresponding to a neighbor cache entry for another Client, it (re)sets ForwardTime for the neighbor to FORWARD_TIME and sets Retry to MAX_RETRY. (When an AERO Client receives a valid unsolicited NA message, it updates the neighbor's link-layer address but DOES NOT reset ForwardTime or Retries.) It is RECOMMENDED that FORWARD_TIME be set to the default constant value 30 seconds to match the default REACHABLE_TIME value specified for IPv6 ND [RFC4861]. It is RECOMMENDED that ACCEPT_TIME be set to the default constant value 40 seconds to allow a 10 second window so that the AERO redirection procedure can converge before AcceptTime decrements below FORWARD_TIME. It is RECOMMENDED that MAX_RETRY be set to 3 the same as described for IPv6 ND address resolution in Section 7.3.3 of [RFC4861]. Different values for FORWARD_TIME, ACCEPT_TIME, and MAX_RETRY MAY be administratively set, if necessary, to better match the AERO link's performance characteristics; however, if different values are chosen, all nodes on the link MUST consistently configure the same values. Most importantly, ACCEPT_TIME SHOULD be set to a value that is sufficiently longer than FORWARD_TIME to allow the AERO redirection procedure to converge. For AERO Client<->Server neighbor cache entries, AcceptTime and ForwardTime are set based on the DHCPv6 lease lifetime and may be modified based on the Router Lifetime advertised in the Server's RA messages. 3.6. AERO Interface Sending Algorithm When an IP packet enters a Client's AERO interface from the network layer, the Client searches its neighbor cache for an entry with an AERO address that matches the packet's destination address. If there is a match, the Client uses the link-layer address in the neighbor cache entry as the link-layer address for encapsulation then admits the packet into the tunnel. If there is no match, the Client instead uses the link-layer address of a neighboring Server as the link-layer address for encapsulation. (Note that the Client caches the ASPs for the AERO link and can thus search the neighbor cache only for destination addresses that are covered by an ASP.) Templin Expires February 16, 2015 [Page 13]
Internet-Draft AERO August 2014 When an IP packet enters a Server's AERO interface from the link layer, the Server searches for a neighbor cache match the same as for a Client. If there is a match, the Server uses the link-layer address in the neighbor cache entry as the link-layer address for re- encapsulation. If there is no match, the Server instead uses the link-layer address of a neighboring Relay as the link-layer address for encapsulation. Servers also relay Predirect, Redirect and unsolicited Neighbor Advertisement messages received from a Client and with an AERO destination address. If the AERO destination address is the address of a neighbor, the Server changes the link- layer source address to its own address, changes the link-layer destination address to the address of the neighbor and forwards the message to the neighbor. If the AERO destination address is not a neighbor, the Server instead forwards the message to a Relay. When an AERO Relay forwards either a data packet or an IPv6 ND message to an AERO Server, the Server MUST NOT forward the packet back to the same or a different Relay. When an IP packet enters a Relay's AERO interface from the network layer, the Relay searches its IP forwarding table for an entry that is covered by an ASP and also matches the destination. If there is a match, the Relay uses the link-layer address in the neighbor cache entry for the next-hop Server as the link-layer address for encapsulation. When an IP packet enters a Relay's AERO interface from the link-layer, if the destination is not covered by an ASP the Relay forwards the packet to another IP link as indicated by the IP forwarding table. If the destination is covered by an ASP, and there is a more-specific forwarding table entry that matches the destination, the Relay uses the link-layer address in the neighbor cache entry for the next-hop Server as the link-layer address for encapsulation. If there is no more-specific entry, the Relay instead drops the packet. Relays also relay Predirect, Redirect and unsolicited Neighbor Advertisement messages by searching for an IP forwarding table entry that matches the message's AERO destination address. If there is a match, the Relay proxies the packet in the same manner as described for Servers above; otherwise, the Relay drops the packet. When an AERO Server forwards either a data packet or an IPv6 ND message to an AERO Relay, the Relay MUST NOT forward the packet back to the same Server. Note that in the above this tunnel exit determination is often based on consulting the neighbor cache instead of the IP forwarding table. IP forwarding is therefore linked to IPv6 ND via the AERO address. When an AERO node forwards a packet back out the same AERO interface the packet arrived on, the node MUST NOT decrement the network layer TTL/Hop-count. Templin Expires February 16, 2015 [Page 14]
Internet-Draft AERO August 2014 3.7. AERO Interface Encapsulation, Re-encapsulation and Decapsulation AERO interfaces encapsulate IP packets according to whether they are entering the AERO interface from the network layer or if they are being forwarded out the same AERO interface that they arrived on. This latter form of encapsulation is known as "re-encapsulation". AERO interfaces encapsulate packets per the specifications in [RFC2003][RFC2473][RFC4213][RFC4301][RFC5246] (etc.) except that the interface copies the "TTL/Hop Limit", "Type of Service/Traffic Class" and "Congestion Experienced" values in the packet's IP header into the corresponding fields in the encapsulation header. For packets undergoing re-encapsulation, the AERO interface instead copies the "TTL/Hop Limit", "Type of Service/Traffic Class" and "Congestion Experienced" values in the original encapsulation header into the corresponding fields in the new encapsulation header (i.e., the values are transferred between encapsulation headers and *not* copied from the encapsulated packet's network-layer header). When AERO UDP encapsulation is used, the AERO interface encapsulates the packet per the above tunneling specifications except that it inserts a UDP header between the encapsulation header and the packet's IP header. The AERO interface sets the UDP source port to a constant value that it will use in each successive packet it sends, sets the UDP checksum field to zero (see: [RFC6935][RFC6936]) and sets the UDP length field to the length of the IP packet plus 8 bytes for the UDP header itself. For packets sent via a Server, the AERO interface sets the UDP destination port to 8060 (i.e., the IANA- registered port number for AERO) when AERO-only encapsulation is used. For packets sent to a neighboring Client, the AERO interface sets the UDP destination port to the port value stored in the neighbor cache entry for this neighbor. The AERO interface next sets the IP protocol number in the encapsulation header to the appropriate value for the first protocol layer within the encapsulation (e.g., IPv4, IPv6, UDP, IPsec, etc.). When IPv6 is used as the encapsulation protocol, the interface then sets the flow label value in the encapsulation header the same as described in [RFC6438]. When IPv4 is used as the encapsulation protocol, the AERO interface sets the DF bit as discussed in Section 3.7. AERO interfaces decapsulate packets destined either to the node itself or to a destination reached via an interface other than the AERO interface the packet was received on. When AERO UDP encapsulation is used (i.e., when a UDP header with destination port 8060 is present) the interface examines the first octet of the encapsulated packet. If the most significant four bits of the first Templin Expires February 16, 2015 [Page 15]
Internet-Draft AERO August 2014 octet encode the value '0110' (i.e., the version number value for IPv6) or the value '0100' (i.e., the version number value for IPv4), the packet is accepted and the encapsulating UDP header is discarded; otherwise, the packet is discarded. Further decapsulation then proceeds according to the appropriate tunnel type per the above specifications. 3.8. AERO Interface Data Origin Authentication AERO nodes employ simple data origin authentication procedures for encapsulated packets they receive from other nodes. In particular, AERO Clients accept encapsulated packets with a link-layer source address belonging to one of their current AERO Servers, and AERO Clients and Servers accept encapsulated packets with a link-layer source address that is correct for the network-layer source address. The AERO node considers the link-layer source address correct for the network-layer source address if there is an AERO interface neighbor cache entry with an AERO address that matches the packet's network- layer source address prefix, with a link-layer address that matches the packet's link-layer source address, and AcceptTime is non-zero. An AERO Server also accepts packets with a link-layer source address that matches one of its associated Relays, and an AERO Relay accepts packets with a source address that matches one of its associated Servers. Note that this simple data origin authentication only applies to environments in which link-layer addresses cannot be spoofed. Additional security mitigations may be necessary in other environments. 3.9. AERO Interface MTU Considerations The AERO link Maximum Transmission Unit (MTU) is 64KB minus the encapsulation overhead for IPv4 as the link-layer [RFC0791] and 4GB minus the encapsulation overhead for IPv6 as the link layer [RFC2675]. This is the most that IPv4 and IPv6 (respectively) can convey within the constraints of protocol constants, but actual sizes available for tunneling will frequently be much smaller. The base tunneling specifications for IPv4 and IPv6 typically set a static MTU on the tunnel interface to 1500 bytes minus the encapsulation overhead or smaller still if the tunnel is likely to incur additional encapsulations on the path. This can result in path MTU related black holes when packets that are too large to be accommodated over the AERO link are dropped, but the resulting ICMP Templin Expires February 16, 2015 [Page 16]
Internet-Draft AERO August 2014 Packet Too Big (PTB) messages are lost on the return path. As a result, AERO nodes use the following MTU mitigations to accommodate larger packets. AERO nodes set their AERO interface MTU to the larger of the underlying interface MTU minus the encapsulation overhead, and 1500 bytes. (If there are multiple underlying interfaces, the node sets the AERO interface MTU according to the largest underlying interface MTU, or 64KB /4G minus the encapsulation overhead if the largest MTU cannot be determined.) AERO nodes optionally cache other per- neighbor MTU values in the underlying IP path MTU discovery cache initialized to the underlying interface MTU. AERO nodes admit packets that are no larger than 1280 bytes minus the encapsulation overhead (*) as well as packets that are larger than 1500 bytes into the tunnel without fragmentation, i.e., as long as they are no larger than the AERO interface MTU before encapsulation and also no larger than the cached per-neighbor MTU following encapsulation. For IPv4, the node sets the "Don't Fragment" (DF) bit to 0 for packets no larger than 1280 bytes minus the encapsulation overhead (*) and sets the DF bit to 1 for packets larger than 1500 bytes. If a large packet is lost in the path, the node may optionally cache the MTU reported in the resulting PTB message or may ignore the message, e.g., if there is a possibility that the message is spurious. For packets destined to an AERO node that are larger than 1280 bytes minus the encapsulation overhead (*) but no larger than 1500 bytes, the node uses IP fragmentation to fragment the encapsulated packet into two pieces (where the first fragment contains 1024 bytes of the original IP packet) then admits the fragments into the tunnel. If the link-layer protocol is IPv4, the node admits each fragment into the tunnel with DF set to 0 and subject to rate limiting to avoid reassembly errors [RFC4963][RFC6864]. For both IPv4 and IPv6, the node also sends a 1500 byte probe message (**) to the neighbor, subject to rate limiting. To construct a probe, the node prepares an NS message with a Nonce option plus trailing padding octets added to a length of 1500 bytes without including the length of the padding in the IPv6 Payload Length field. The node then encapsulates the NS in the encapsulation headers (while including the length of the padding in the encapsulation header length fields), sets DF to 1 (for IPv4) and sends the padded NS message to the neighbor. If the neighbor returns an NA message with a correct Nonce value, the node may then send whole packets within this size range and (for IPv4) relax the rate limiting requirement. (Note that the trailing padding SHOULD NOT be included within the Nonce option itself but rather as padding beyond Templin Expires February 16, 2015 [Page 17]
Internet-Draft AERO August 2014 the last option in the NS message; otherwise, the (large) Nonce option would be echoed back in the solicited NA message and may be lost at a link with a small MTU along the reverse path.) AERO nodes MUST be capable of reassembling packets up to 1500 bytes plus the encapsulation overhead length. It is therefore RECOMMENDED that AERO nodes be capable of reassembling at least 2KB. (*) Note that if it is known without probing that the minimum Path MTU to an AERO node is MINMTU bytes (where 1280 < MINMTU < 1500) then MINMTU can be used instead of 1280 in the fragmentation threshold considerations listed above. (**) It is RECOMMENDED that no probes smaller than 1500 bytes be used for MTU probing purposes, since smaller probes may be fragmented if there is a nested tunnel somewhere on the path to the neighbor. Probe sizes larger than 1500 bytes MAY be used, but may be unnecessary since original sources are expected to implement [RFC4821] when sending large packets. 3.10. AERO Router Discovery, Prefix Delegation and Address Configuration 3.10.1. AERO DHCPv6 Service Model Each AERO Server configures a DHCPv6 server function to facilitate PD requests from Clients. Each Server is pre-configured with an identical list of ACP-to-Client ID mappings for all Clients enrolled in the AERO system, as well as any information necessary to authenticate Clients. The configuration information is maintained by a central administrative authority for the AERO link and securely propagated to all Servers whenever a new Client is enrolled or an existing Client is deprecated. With these identical configurations, each Server can function independently of all other Servers, including the maintenance of active leases. Therefore, no Server-to-Server DHCPv6 state synchronization is necessary, and Clients can potentially hold separate leases for the same ACP from multiple Servers. In this way, Clients can easily associate with multiple Servers, and can receive new leases from new Servers before deprecating leases held through old Servers. This gives way to a graceful "make-before- break" capability. Templin Expires February 16, 2015 [Page 18]
Internet-Draft AERO August 2014 3.10.2. AERO Client Behavior AERO Clients discover the link-layer addresses of AERO Servers via static configuration, or through an automated means such as DNS name resolution. In the absence of other information, the Client resolves the Fully-Qualified Domain Name (FQDN) "linkupnetworks.[domainname]" where "linkupnetworks" is a constant text string and "[domainname]" is the connection-specific DNS suffix for the Client's underlying network connection. After discovering the link-layer addresses, the Client associates with one or more of the corresponding Servers. To associate with a Server, the Client acts as a requesting router to request an ACP through DHCPv6 PD [RFC3315][RFC3633][RFC6355] using 'fe80::ffff:ffff:ffff:ffff' as the IPv6 source address, 'All_DHCP_Relay_Agents_and_Servers' as the IPv6 destination address and the link-layer address of the Server as the link-layer destination address. The Client includes a DHCPv6 Unique Identifier (DUID) in the Client Identifier option of its DHCPv6 messages (as well as a DHCPv6 authentication option if necessary) to identify itself to the DHCPv6 server. If the Client is pre-provisioned with an ACP associated with the AERO service, it MAY also include the ACP in its DHCPv6 PD Request to indicate its preferred ACP to the DHCPv6 server. The Client then sends the encapsulated DHCPv6 Solicit/ Request message via an underlying interface. When the Client receives its ACP and the set of ASPs via a DHCPv6 Reply from the AERO Server, it creates a neighbor cache entry with the Server's link-local address (i.e., fe80::ID) as the network-layer address and the Server's encapsulation address as the link-layer address. The Client then records the lifetime for the ACP in the neighbor cache entry and marks the neighbor cache entry as "default", i.e., the Client considers the Server as a default router. If the Reply message contains a Vendor-Specific Information Option (see: Section 3.10.3) the Client also caches each ASP in the option. The Client then applies the AERO address to the AERO interface and sub-delegates the ACP to nodes and links within its attached EUNs (the AERO address thereafter remains stable as the Client moves). The Client also assigns a default IP route to the AERO interface as a route-to-interface, i.e., with no explicit next-hop. The next hop will then be determined after a packet has been submitted to the AERO interface by inspecting the neighbor cache (see above). The Client subsequently renews its ACP delegation through each of its Servers by performing DHCPv6 Renew/Reply exchanges with its AERO address as the IPv6 source address, 'All_DHCP_Relay_Agents_and_Servers' as the IPv6 destination address, Templin Expires February 16, 2015 [Page 19]
Internet-Draft AERO August 2014 the link-layer address of a Server as the link-layer destination address and the same DUID and authentication information. Since the Client's AERO address is configured from the unique ACP delegation it receives, there is no need for Duplicate Address Detection (DAD) on AERO links. Other nodes maliciously attempting to hijack an authorized Client's AERO address will be denied access to the network by the DHCPv6 server due to an unacceptable link-layer address and/or security parameters (see: Security Considerations). AERO Clients ignore the IP address and UDP port number in any S/TLLAO options in ND messages they receive directly from another AERO Client, but examine the Link ID and Preference values to match the message with the correct link-layer address information. When a source Client forwards a packet to a prospective destination Client (i.e., one for which the packet's destination address is covered by an ASP), the source Client initiates an AERO route optimization procedure as specified in Section 3.12. 3.10.3. AERO Server Behavior AERO Servers configure a DHCPv6 server function on their AERO links. AERO Servers arrange to add their encapsulation layer IP addresses (i.e., their link-layer addresses) to the DNS resource records for the FQDN "linkupnetworks.[domainname]" before entering service. When an AERO Server receives a prospective Client's DHCPv6 PD Solicit/Request message, it first authenticates the Client and ignores the request if authentication fails. Otherwise, the Server delegates the ACP then creates a neighbor cache entry for the Client's AERO address with the Client's link-layer address as the link-layer address and with lifetime set to no more than the lease lifetime. The Server then injects the ACP as an IP route into the inter-Server/Relay routing system (see: Section 3.11). Finally, the Server sends a DHCPv6 Reply message to the Client while using fe80::ID as the IPv6 source address, the Client's link-local address as the IPv6 destination address, and the Client's link-layer address as the destination link-layer address. When the Server sends the DHCPv6 Reply message, it also includes a DHCPv6 Vendor-Specific Information Option with 'enterprise-number' set to "TBD" (see: IANA Considerations). The option is formatted as shown in[RFC3315] and with the AERO enterprise-specific format shown in Figure 3: Templin Expires February 16, 2015 [Page 20]
Internet-Draft AERO August 2014 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_VENDOR_OPTS | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | enterprise-number ("TBD") | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + ASP (1) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + ASP (2) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + ASP (3) + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . (etc.) . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: AERO Vendor-Specific Information Option Per Figure 3, the option includes one or more ASP. The Prefix Length field must contain a value between 0 - 64, and the ASP field contains the IP prefix as it would appear in the interface identifier portion of the corresponding AERO address (see: Section 3.3). After the initial Solicit/Request/Reply exchange, the AERO Server maintains the neighbor cache entry and IP route for the Client as long as the lease lifetime remains current. If the Client issues a Renew/Reply exchange, the Server extends the lifetime. If the Client issues a Release/Reply exchange, or if the Client does not issue a Renew/Reply within the lease lifetime, the Server deletes the neighbor cache entry for the Client and withdraws the IP route from the routing system. Templin Expires February 16, 2015 [Page 21]
Internet-Draft AERO August 2014 3.11. AERO Relay/Server Routing System Relays require full topology information of all Client/Server associations, while individual Servers only require partial topology information, i.e., they only need to know the ACPs associated with their current set of associated Clients. This is accomplished through the use of an internal instance of the Border Gateway Protocol (BGP) [RFC4271] coordinated between Servers and Relays. This internal BGP instance does not interact with the public Internet BGP instance; therefore, the AERO link is presented to the IP Internetwork as a small set of ASPs as opposed to the full set of individual ACPs. In a reference BGP arrangement, each AERO Server is configured as an Autonomous System Border Router (ASBR) for a stub Autonomous System (AS) (possibly using a private AS Number (ASN) [RFC1930]), and each Server further peers with each Relay but does not peer with other Servers. Similarly, Relays need not peer with each other, since they will receive all updates from all Servers and will therefore have a consistent view of the AERO link ACP delegations. Each Server maintains a working set of associated Clients, and dynamically announces new ACPs and withdraws departed ACPs in its BGP updates to Relays. Relays do not send BGP updates to Servers, however, such that the BGP route reporting is unidirectional from the Servers to the Relays. The Relays therefore discover the full topology of the AERO link in terms of the working set of ACPs associated with each Server, while the Servers only discover the ACPs of their associated Clients. Since Clients are expected to remain associated with their current set of Servers for extended timeframes, the amount of BGP control messaging between Servers and Relays should be minimal. However, BGP peers SHOULD dampen any route oscillations caused by impatient Clients that repeatedly associate and disassociate with Servers. 3.12. AERO Redirection 3.12.1. Reference Operational Scenario Figure 4 depicts the AERO redirection reference operational scenario, using IPv6 addressing as the example (while not shown, a corresponding example for IPv4 addressing can be easily constructed). The figure shows an AERO Relay ('R'), two AERO Servers ('S1', 'S2'), two AERO Clients ('A', 'B') and two ordinary IPv6 hosts ('C', 'D'): Templin Expires February 16, 2015 [Page 22]
Internet-Draft AERO August 2014 +--------------+ +--------------+ +--------------+ | Server S1 | | Relay R | | Server S2 | | Nbr: A | |(C->S1; D->S2)| | Nbr: B | +--------------+ +--------------+ +--------------+ fe80::2 fe80::1 fe80::3 L2(S1) L2(R) L2(S2) | | | X-----+-----+------------------+-----------------+----+----X | AERO Link | L2(A) L2(B) fe80::2001:db8:0:0 fe80::2001:db8:1:0 +--------------+ +--------------+ | AERO Client A| | AERO Client B| | (default->S1)| | (default->S2)| +--------------+ +--------------+ 2001:DB8:0::/48 2001:DB8:1::/48 | | .-. .-. ,-( _)-. 2001:db8:0::1 2001:db8:1::1 ,-( _)-. .-(_ IP )-. +---------+ +---------+ .-(_ IP )-. (__ EUN )--| Host C | | Host D |--(__ EUN ) `-(______)-' +---------+ +---------+ `-(______)-' Figure 4: AERO Reference Operational Scenario In Figure 4, Relay ('R') applies the address fe80::1 to its AERO interface with link-layer address L2(R), Server ('S1') applies the address fe80::2 with link-layer address L2(S1),and Server ('S2') applies the address fe80::3 with link-layer address L2(S2). Servers ('S1') and ('S2') next arrange to add their link-layer addresses to a published list of valid Servers for the AERO link. AERO Client ('A') receives the ACP 2001:db8:0::/48 in a DHCPv6 PD exchange via AERO Server ('S1') then assigns the address fe80::2001:db8:0:0 to its AERO interface with link-layer address L2(A). Client ('A') configures a default route and neighbor cache entry via the AERO interface with next-hop address fe80::2 and link- layer address L2(S1), then sub-delegates the ACP to its attached EUNs. IPv6 host ('C') connects to the EUN, and configures the address 2001:db8:0::1. AERO Client ('B') receives the ACP 2001:db8:1::/48 in a DHCPv6 PD exchange via AERO Server ('S2') then assigns the address fe80::2001:db8:1:0 to its AERO interface with link-layer address L2(B). Client ('B') configures a default route and neighbor cache entry via the AERO interface with next-hop address fe80::3 and link- layer address L2(S2), then sub-delegates the ACP to its attached Templin Expires February 16, 2015 [Page 23]
Internet-Draft AERO August 2014 EUNs. IPv6 host ('D') connects to the EUN, and configures the address 2001:db8:1::1. 3.12.2. Concept of Operations Again, with reference to Figure 4, when source host ('C') sends a packet to destination host ('D'), the packet is first forwarded over the source host's attached EUN to Client ('A'). Client ('A') then forwards the packet via its AERO interface to Server ('S1') and also sends a Predirect message toward Client ('B') via Server ('S1'). Server ('S1') then re-encapsulates and forwards both the packet and the Predirect message out the same AERO interface toward Client ('B') via Relay ('R'). When Relay ('R') receives the packet and Predirect message, it consults its forwarding table to discover Server ('S2') as the next hop toward Client ('B'). Relay ('R') then forwards both messages to Server ('S2'), which then forwards them to Client ('B'). After Client ('B') receives the Predirect message, it process the message and returns a Redirect message toward Client ('A') via Server ('S2'). During the process, Client ('B') also creates or updates a neighbor cache entry for Client ('A'). When Server ('S2') receives the Redirect message, it re-encapsulates the message and forwards it on to Relay ('R'), which forwards the message on to Server ('S1') which forwards the message on to Client ('A'). After Client ('A') receives the Redirect message, it processes the message and creates or updates a neighbor cache entry for Client ('C'). Following the above Predirect/Redirect message exchange, forwarding of packets from Client ('A') to Client ('B') without involving any intermediate nodes is enabled. The mechanisms that support this exchange are specified in the following sections. 3.12.3. Message Format AERO Redirect/Predirect messages use the same format as for ICMPv6 Redirect messages depicted in Section 4.5 of [RFC4861], but also include a new "Prefix Length" field taken from the low-order 8 bits of the Redirect message Reserved field. (For IPv6, valid values for the Prefix Length field are 0 through 64; for IPv4, valid values are 0 through 32.) The Redirect/Predirect messages are formatted as shown in Figure 5: Templin Expires February 16, 2015 [Page 24]
Internet-Draft AERO August 2014 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (=137) | Code (=0/1) | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Target Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 5: AERO Redirect/Predirect Message Format 3.12.4. Sending Predirects When a Client forwards a packet with a source address from one of its ACPs toward a destination address covered by an ASP (i.e., toward another AERO Client connected to the same AERO link), the source Client MAY send a Predirect message forward toward the destination Client via the Server. In the reference operational scenario, when Client ('A') forwards a packet toward Client ('B'), it MAY also send a Predirect message forward toward Client ('B'), subject to rate limiting (see Section 8.2 of [RFC4861]). Client ('A') prepares the Predirect message as follows: o the link-layer source address is set to 'L2(A)' (i.e., the link- layer address of Client ('A')). o the link-layer destination address is set to 'L2(S1)' (i.e., the link-layer address of Server ('S1')). Templin Expires February 16, 2015 [Page 25]
Internet-Draft AERO August 2014 o the network-layer source address is set to fe80::2001:db8:0:0 (i.e., the AERO address of Client ('A')). o the network-layer destination address is set to fe80::2001:db8:1:0 (i.e., the AERO address of Client ('B')). o the Type is set to 137. o the Code is set to 1 to indicate "Predirect". o the Prefix Length is set to the length of the prefix to be applied to the Target Address. o the Target Address is set to fe80::2001:db8:0:0 (i.e., the AERO address of Client ('A')). o the Destination Address is set to the source address of the originating packet that triggered the Predirection event. (If the originating packet is an IPv4 packet, the address is constructed in IPv4-compatible IPv6 address format). o the message includes a TLLAO with Link ID and Preference set to appropriate values for Client ('A')'s underlying interface, and with UDP Port Number and IP Address set to 0'. o the message SHOULD include a Timestamp option. o the message includes a Redirected Header Option (RHO) that contains the originating packet truncated to ensure that at least the network-layer header is included but the size of the message does not exceed 1280 bytes. Note that the act of sending Predirect messages is cited as "MAY", since Client ('A') may have advanced knowledge that the direct path to Client ('B') would be unusable. If the direct path later becomes unusable after the initial route optimization, Client ('A') simply allows packets to again flow through Server ('S1'). 3.12.5. Re-encapsulating and Relaying Predirects When Server ('S1') receives a Predirect message from Client ('A'), it first verifies that the requested redirection is authorized. If the redirection is not permitted, Server ('S1') discards the message. Otherwise, Server ('S1') validates the message according to the ICMPv6 Redirect message validation rules in Section 8.1 of [RFC4861], except that the Predirect has Code=1. Server ('S1') also verifies that Client ('A') is authorized to use the Prefix Length in the Predirect when applied to the AERO address in the network-layer Templin Expires February 16, 2015 [Page 26]
Internet-Draft AERO August 2014 source address by searching for the AERO address in the neighbor cache. If validation fails, Server ('S1') discards the Predirect; otherwise, it copies the correct UDP Port number and IP Address for Client ('A') into the (previously empty) TLLAO. Server ('S1') then examines the network-layer destination address of the Predirect to determine the next hop toward Client ('B') by searching for the AERO address in the neighbor cache. Since Client ('B') is not one of its neighbors, Server ('S1') re-encapsulates the Predirect and relays it via Relay ('R') by changing the link-layer source address of the message to 'L2(S1)' and changing the link-layer destination address to 'L2(R)'. Server ('S1') finally forwards the re-encapsulated message to Relay ('R') without decrementing the network-layer TTL/Hop Limit field. When Relay ('R') receives the Predirect message from Server ('S1') it determines that Server ('S2') is the next hop toward Client ('B') by consulting its forwarding table. Relay ('R') then re-encapsulates the Predirect while changing the link-layer source address to 'L2(R)' and changing the link-layer destination address to 'L2(S2)'. Relay ('R') then relays the Predirect via Server ('S2'). When Server ('S2') receives the Predirect message from Relay ('R') it determines that Client ('B') is a neighbor by consulting its neighbor cache. Server ('S2') then re-encapsulates the Predirect while changing the link-layer source address to 'L2(S2)' and changing the link-layer destination address to 'L2(B)'. Server ('S2') then forwards the message to Client ('B'). 3.12.6. Processing Predirects and Sending Redirects When Client ('B') receives the Predirect message, it accepts the Predirect only if the message has a link-layer source address of one of its Servers (e.g., L2(S2)). Client ('B') further accepts the message only if it is willing to serve as a redirection target. Next, Client ('B') validates the message according to the ICMPv6 Redirect message validation rules in Section 8.1 of [RFC4861], except that it accepts the message even though Code=1 and even though the network-layer source address is not that of it's current first-hop router. In the reference operational scenario, when Client ('B') receives a valid Predirect message, it either creates or updates a neighbor cache entry that stores the Target Address of the message as the network-layer address of Client ('A') , stores the link-layer address found in the TLLAO as the link-layer address(es) of Client ('A') and stores the Prefix Length as the length to be applied to the network- Templin Expires February 16, 2015 [Page 27]
Internet-Draft AERO August 2014 layer address for forwarding purposes. Client ('B') then sets AcceptTime for the neighbor cache entry to ACCEPT_TIME. After processing the message, Client ('B') prepares a Redirect message response as follows: o the link-layer source address is set to 'L2(B)' (i.e., the link- layer address of Client ('B')). o the link-layer destination address is set to 'L2(S2)' (i.e., the link-layer address of Server ('S2')). o the network-layer source address is set to fe80::2001:db8:1:0 (i.e., the AERO address of Client ('B')). o the network-layer destination address is set to fe80::2001:db8:0:0 (i.e., the AERO address of Client ('A')). o the Type is set to 137. o the Code is set to 0 to indicate "Redirect". o the Prefix Length is set to the length of the prefix to be applied to the Target Address. o the Target Address is set to fe80::2001:db8:1:0 (i.e., the AERO address of Client ('B')). o the Destination Address is set to the destination address of the originating packet that triggered the Redirection event. (If the originating packet is an IPv4 packet, the address is constructed in IPv4-compatible IPv6 address format). o the message includes a TLLAO with Link ID and Preference set to appropriate values for Client ('B')'s underlying interface, and with UDP Port Number and IP Address set to '0'. o the message SHOULD include a Timestamp option. o the message includes as much of the RHO copied from the corresponding AERO Predirect message as possible such that at least the network-layer header is included but the size of the message does not exceed 1280 bytes. After Client ('B') prepares the Redirect message, it sends the message to Server ('S2'). Templin Expires February 16, 2015 [Page 28]
Internet-Draft AERO August 2014 3.12.7. Re-encapsulating and Relaying Redirects When Server ('S2') receives a Redirect message from Client ('B'), it first verifies that the requested redirection is authorized. If the redirection is not permitted, Server ('S2') discards the message. Otherwise, Server ('S2') validates the message according to the ICMPv6 Redirect message validation rules in Section 8.1 of [RFC4861]. Server ('S2') also verifies that Client ('B') is authorized to use the Prefix Length in the Redirect when applied to the AERO address in the network-layer source address by searching for the AERO address in the neighbor cache. If validation fails, Server ('S2') discards the Predirect; otherwise, it copies the correct UDP Port number and IP Address for Client ('B') into the (previously empty) TLLAO. Server ('S2') then examines the network-layer destination address of the Predirect to determine the next hop toward Client ('A') by searching for the AERO address in the neighbor cache. Since Client ('A') is not one of its neighbors, Server ('S2') re-encapsulates the Predirect and relays it via Relay ('R') by changing the link-layer source address of the message to 'L2(S2)' and changing the link-layer destination address to 'L2(R)'. Server ('S2') finally forwards the re-encapsulated message to Relay ('R') without decrementing the network-layer TTL/Hop Limit field. When Relay ('R') receives the Predirect message from Server ('S2') it determines that Server ('S1') is the next hop toward Client ('A') by consulting its forwarding table. Relay ('R') then re-encapsulates the Predirect while changing the link-layer source address to 'L2(R)' and changing the link-layer destination address to 'L2(S1)'. Relay ('R') then relays the Predirect via Server ('S1'). When Server ('S1') receives the Predirect message from Relay ('R') it determines that Client ('A') is a neighbor by consulting its neighbor cache. Server ('S1') then re-encapsulates the Predirect while changing the link-layer source address to 'L2(S1)' and changing the link-layer destination address to 'L2(A)'. Server ('S1') then forwards the message to Client ('A'). 3.12.8. Processing Redirects When Client ('A') receives the Redirect message, it accepts the message only if it has a link-layer source address of one of its Servers (e.g., ''L2(S1)'). Next, Client ('A') validates the message according to the ICMPv6 Redirect message validation rules in Section 8.1 of [RFC4861], except that it accepts the message even though the network-layer source address is not that of it's current first-hop router. Following validation, Client ('A') then processes the message as follows. Templin Expires February 16, 2015 [Page 29]
Internet-Draft AERO August 2014 In the reference operational scenario, when Client ('A') receives the Redirect message, it either creates or updates a neighbor cache entry that stores the Target Address of the message as the network-layer address of Client ('B'), stores the link-layer address found in the TLLAO as the link-layer address of Client ('B') and stores the Prefix Length as the length to be applied to the network-layer address for forwarding purposes. Client ('A') then sets ForwardTime for the neighbor cache entry to FORWARD_TIME. Now, Client ('A') has a neighbor cache entry with a valid ForwardTime value, while Client ('B') has a neighbor cache entry with a valid AcceptTime value. Thereafter, Client ('A') may forward ordinary network-layer data packets directly to Client ("B") without involving any intermediate nodes, and Client ('B') can verify that the packets came from an acceptable source. (In order for Client ('B') to forward packets to Client ('A'), a corresponding Predirect/Redirect message exchange is required in the reverse direction; hence, the mechanism is asymmetric.) 3.12.9. Server-Oriented Redirection In some environments, the Server nearest the destination Client may need to serve as the redirection target, e.g., if direct Client-to- Client communications are not possible. In that case, the Server prepares the Redirect message the same as if it were the destination Client (see: Section 3.9.6), except that it writes its own link-layer address in the TLLAO option. The Server must then maintain a neighbor cache entry for the redirected source Client. 3.13. Neighbor Unreachability Detection (NUD) AERO nodes perform NUD by sending unicast NS messages to elicit solicited NA messages from neighbors the same as described in [RFC4861]. When an AERO node sends an NS/NA message, it MUST use its AERO address as the IPv6 source address and the link-local address of the neighbor as the IPv6 destination address. When an AERO node receives an NS message or a solicited NA message, it accepts the message if it has a neighbor cache entry for the neighbor; otherwise, it ignores the message. When a source Client is redirected to a target Client it SHOULD test the direct path by sending an initial NS message to elicit a solicited NA response. While testing the path, the source Client can optionally continue sending packets via the Server, maintain a small queue of packets until target reachability is confirmed, or (optimistically) allow packets to flow directly to the target. The source Client SHOULD thereafter continue to test the direct path to Templin Expires February 16, 2015 [Page 30]
Internet-Draft AERO August 2014 the target Client (see Section 7.3 of [RFC4861]) periodically in order to keep neighbor cache entries alive. In particular, while the source Client is actively sending packets to the target Client it SHOULD also send NS messages separated by RETRANS_TIMER milliseconds in order to receive solicited NA messages. If the source Client is unable to elicit a solicited NA response from the target Client after MAX_RETRY attempts, it SHOULD set ForwardTime to 0 and resume sending packets via the Server which may or may not result in a new redirection event. Otherwise, the source Client considers the path usable and SHOULD thereafter process any link- layer errors as a hint that the direct path to the target Client has either failed or has become intermittent. When a target Client receives an NS message from a source Client, it resets AcceptTime to ACCEPT_TIME if a neighbor cache entry exists; otherwise, it discards the NS message. When a source Client receives a solicited NA message from a target Client, it resets ForwardTime to FORWARD_TIME if a neighbor cache entry exists; otherwise, it discards the NA message. When ForwardTime for a neighbor cache entry expires, the source Client resumes sending any subsequent packets via the Server and may (eventually) attempt to re-initiate the AERO redirection process. When AcceptTime for a neighbor cache entry expires, the target Client discards any subsequent packets received directly from the source Client. When both ForwardTime and AcceptTime for a neighbor cache entry expire, the Client deletes the neighbor cache entry. 3.14. Mobility Management 3.14.1. Announcing Link-Layer Address Changes When a Client needs to change its link-layer address, e.g., due to a mobility event, it performs an immediate DHCPv6 Rebind/Reply via each of its Servers using the new link-layer address as the source. The Server will re-authenticate the Client and (assuming authentication succeeds) update its neighbor cache and send a DHCPv6 Reply. Next, the Client sends unsolicited NA messages to each of its active neighbors using the same procedures as specified in Section 7.2.6 of [RFC4861], except that it sends the messages as unicast to each neighbor via a Server instead of multicast. In this process, the Client should send no more than MAX_NEIGHBOR_ADVERTISEMENT messages separated by no less than RETRANS_TIMER seconds to each neighbor. Templin Expires February 16, 2015 [Page 31]
Internet-Draft AERO August 2014 With reference to Figure 4, Client ('B') sends unicast unsolicited NA messages to Client ('A') via Server ('S2') as follows: o the link-layer source address is set to 'L2(B)' (i.e., the link- layer address of Client ('B')). o the link-layer destination address is set to 'L2(S2)' (i.e., the link-layer address of Server ('S2')). o the network-layer source address is set to fe80::2001:db8:1:0 (i.e., the AERO address of Client ('B')). o the network-layer destination address is set to fe80::2001:db8:0:0 (i.e., the AERO address of Client ('A')). o the Type is set to 136. o the Code is set to 0. o the Solicited flag is set to 0. o the Override flag is set to 1. o the Target Address is set to fe80::2001:db8:1:0 (i.e., the AERO address of Client ('B')). o the message includes a TLLAO with Link ID and Preference set to appropriate values for Client ('B')'s underlying interface, and with UDP Port Number and IP Address set to '0'. o the message SHOULD include a Timestamp option. When Server ('S1') receives the NA message, it relays the message in the same way as described for relaying Redirect messages in Section 3.12.7. In particular, Server ('S1') copies the correct UDP port number and IP address into the TLLAO, changes the link-layer source address to its own address, changes the link-layer destination address to the address of Relay ('R'), then forwards the NA message via the relaying chain the same as for a Redirect. When Client ('A') receives the NA message, it accepts the message only if it already has a neighbor cache entry for Client ('B') then updates the link-layer address for Client ('B') based on the address in the TLLAO. However, Client ('A') MUST NOT update ForwardTime since Client ('B') will not have updated AcceptTime. Note that these unsolicited NA messages are unacknowledged; hence, Client ('B') has no way of knowing whether Client ('A') has received Templin Expires February 16, 2015 [Page 32]
Internet-Draft AERO August 2014 them. If the messages are somehow lost, however, Client ('A') will soon learn of the mobility event via the NUD procedures specified in Section 3.13. 3.14.2. Moving to a New Server When a Client associates with a new Server, it issues a new DHCPv6 Solicit/Request message to the new Server. If authentication succeeds, the Server updates its neighbor cache and issues a DHCPv6 Reply containing the Client's ACP. When a Client disassociates with an existing Server, it sends a DHCPv6 Release message to the old Server. When the old Server receives the DHCPv6 Release, it first authenticates the message. If the message, is authentic, the old Server withdraws the IP route from the routing system and deletes the neighbor cache entry for the Client. The old Server then returns a DHCPv6 Reply message which the Client can use to verify that the termination signal has been processed. The client then deletes both the default route and the neighbor cache entry for the old Server. The old Server SHOULD impose a small delay before deleting the neighbor cache entry so that any packets already in the system can still be delivered to the Client. Clients SHOULD NOT move rapidly between Servers in order to avoid causing unpredictable oscillations in the Server/Relay routing system. Such oscillations could result in intermittent reachability for the Client itself, while causing little harm to the network due to routing protocol dampening. Examples of when a Client might wish to change to a different Server include a Server that has gone unreachable, topological movements of significant distance, etc. 3.15. Encapsulation Protocol Version Considerations A source Client may connect only to an IPvX underlying network, while the target Client connects only to an IPvY underlying network. In that case, the target and source Clients have no means for reaching each other directly (since they connect to underlying networks of different IP protocol versions) and so must ignore any redirection messages and continue to send packets via the Server. 3.16. Multicast Considerations When the underlying network does not support multicast, AERO nodes map IPv6 link-scoped multicast addresses (including 'All_DHCP_Relay_Agents_and_Servers') to the link-layer address of a Server. Templin Expires February 16, 2015 [Page 33]
Internet-Draft AERO August 2014 When the underlying network supports multicast, AERO nodes use the multicast address mapping specification found in [RFC2529] for IPv4 underlying networks and use a direct multicast mapping for IPv6 underlying networks. (In the latter case, "direct multicast mapping" means that if the IPv6 multicast destination address of the encapsulated packet is "M", then the IPv6 multicast destination address of the encapsulating header is also "M".) 3.17. Operation on AERO Links Without DHCPv6 Services When the AERO link does not provide DHCPv6 services, operation can still be accommodated through administrative configuration of ACPs on AERO Clients. In that case, administrative configurations of AERO interface neighbor cache entries on both the Server and Client are also necessary. However, this may interfere with the ability for Clients to dynamically change to new Servers, and can expose the AERO link to misconfigurations unless the administrative configurations are carefully coordinated. 3.18. Operation on Server-less AERO Links In some AERO link scenarios, there may be no Servers on the link and/ or no need for Clients to use a Server as an intermediary trust anchor. In that case, each Client acts as a Server unto itself to establish neighbor cache entries by performing direct Client-to- Client Predirect/Redirect exchanges, and some other form of trust basis must be applied so that each Client can verify that the prospective neighbor is authorized to use its claimed ACP. When there is no Server on the link, Clients must arrange to receive ACPs and publish them via a secure alternate prefix delegation authority through some means outside the scope of this document. 4. Implementation Status An application-layer implementation is in progress. 5. IANA Considerations The IANA is instructed to assign a 4-octet Enterprise Number "TBD" for AERO in the "enterprise-numbers" registry per [RFC3315]. 6. Security Considerations AERO link security considerations are the same as for standard IPv6 Neighbor Discovery [RFC4861] except that AERO improves on some aspects. In particular, AERO uses a trust basis between Clients and Servers, where the Clients only engage in the AERO mechanism when it Templin Expires February 16, 2015 [Page 34]
Internet-Draft AERO August 2014 is facilitated by a trust anchor. AERO also uses DHCPv6 authentication for Client authentication and network admission control. AERO links must be protected against link-layer address spoofing attacks in which an attacker on the link pretends to be a trusted neighbor. Links that provide link-layer securing mechanisms (e.g., IEEE 802.1X WLANs) and links that provide physical security (e.g., enterprise network wired LANs) provide a first line of defense that is often sufficient. In other instances, additional securing mechanisms such as Secure Neighbor Discovery (SeND) [RFC3971], IPsec [RFC4301] or TLS [RFC5246] may be necessary. AERO Clients MUST ensure that their connectivity is not used by unauthorized nodes on EUNs to gain access to a protected network, i.e., AERO Clients that act as routers MUST NOT provide routing services for unauthorized nodes. (This concern is no different than for ordinary hosts that receive an IP address delegation but then "share" the address with unauthorized nodes via a NAT function.) On some AERO links, establishment and maintenance of a direct path between neighbors requires secured coordination such as through the Internet Key Exchange (IKEv2) protocol [RFC5996] to establish a security association. 7. Acknowledgements Discussions both on IETF lists and in private exchanges helped shape some of the concepts in this work. Individuals who contributed insights include Mikael Abrahamsson, Fred Baker, Stewart Bryant, Brian Carpenter, Wojciech Dec, Ralph Droms, Brian Haberman, Joel Halpern, Sascha Hlusiak, Lee Howard, Andre Kostur, Ted Lemon, Joe Touch and Bernie Volz. Members of the IESG also provided valuable input during their review process that greatly improved the document. Special thanks go to Stewart Bryant, Joel Halpern and Brian Haberman for their shepherding guidance. This work has further been encouraged and supported by Boeing colleagues including Keith Bartley, Dave Bernhardt, Cam Brodie, Balaguruna Chidambaram, Claudiu Danilov, Wen Fang, Anthony Gregory, Jeff Holland, Ed King, Gen MacLean, Kent Shuey, Brian Skeen, Mike Slane, Julie Wulff, Yueli Yang, and other members of the BR&T and BIT mobile networking teams. Earlier works on NBMA tunneling approaches are found in [RFC2529][RFC5214][RFC5569]. Templin Expires February 16, 2015 [Page 35]
Internet-Draft AERO August 2014 8. References 8.1. Normative References [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, October 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for IPv6 Hosts and Routers", RFC 4213, October 2005. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node Requirements", RFC 6434, December 2011. Templin Expires February 16, 2015 [Page 36]
Internet-Draft AERO August 2014 8.2. Informative References [RFC0879] Postel, J., "TCP maximum segment size and related topics", RFC 879, November 1983. [RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", BCP 6, RFC 1930, March 1996. [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels", RFC 2529, March 1999. [RFC2675] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms", RFC 2675, August 1999. [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU Discovery", RFC 4821, March 2007. [RFC4963] Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly Errors at High Data Rates", RFC 4963, July 2007. [RFC4994] Zeng, S., Volz, B., Kinnear, K., and J. Brzozowski, "DHCPv6 Relay Agent Echo Request Option", RFC 4994, September 2007. [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, March 2008. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5494] Arkko, J. and C. Pignataro, "IANA Allocation Guidelines for the Address Resolution Protocol (ARP)", RFC 5494, April 2009. Templin Expires February 16, 2015 [Page 37]
Internet-Draft AERO August 2014 [RFC5522] Eddy, W., Ivancic, W., and T. Davis, "Network Mobility Route Optimization Requirements for Operational Use in Aeronautics and Space Exploration Mobile Networks", RFC 5522, October 2009. [RFC5569] Despres, R., "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)", RFC 5569, January 2010. [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010. [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, April 2011. [RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O. Troan, "Basic Requirements for IPv6 Customer Edge Routers", RFC 6204, April 2011. [RFC6355] Narten, T. and J. Johnson, "Definition of the UUID-Based DHCPv6 Unique Identifier (DUID-UUID)", RFC 6355, August 2011. [RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label for Equal Cost Multipath Routing and Link Aggregation in Tunnels", RFC 6438, November 2011. [RFC6691] Borman, D., "TCP Options and Maximum Segment Size (MSS)", RFC 6691, July 2012. [RFC6706] Templin, F., "Asymmetric Extended Route Optimization (AERO)", RFC 6706, August 2012. [RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field", RFC 6864, February 2013. [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and UDP Checksums for Tunneled Packets", RFC 6935, April 2013. [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement for the Use of IPv6 UDP Datagrams with Zero Checksums", RFC 6936, April 2013. [RFC6939] Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer Address Option in DHCPv6", RFC 6939, May 2013. Templin Expires February 16, 2015 [Page 38]
Internet-Draft AERO August 2014 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery", RFC 6980, August 2013. [RFC7078] Matsumoto, A., Fujisaki, T., and T. Chown, "Distributing Address Selection Policy Using DHCPv6", RFC 7078, January 2014. Author's Address Fred L. Templin (editor) Boeing Research & Technology P.O. Box 3707 Seattle, WA 98124 USA Email: fltemplin@acm.org Templin Expires February 16, 2015 [Page 39]