Network Working Group F. Templin, Ed.
Internet-Draft Boeing Phantom Works
Intended status: Informational December 23, 2008
Expires: June 26, 2009
Virtual Enterprise Traversal (VET)
draft-templin-autoconf-dhcp-25.txt
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Abstract
Enterprise networks connect routers over various link types, and may
also connect to provider networks and/or the global Internet. Nodes
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in enterprise networks must have a way to automatically provision IP
addresses/prefixes and other information, and must also support post-
autoconfiguration operations even for highly-dynamic networks. This
document specifies a Virtual Enterprise Traversal (VET) abstraction
for autoconfiguration and operation of nodes in enterprise networks.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Enterprise Characteristics . . . . . . . . . . . . . . . . . . 7
4. Autoconfiguration . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Enterprise Interior Router (EIR) Autoconfiguration . . . . 9
4.2. Enterprise Border Router (EBR) Autoconfiguration . . . . . 10
4.2.1. VET Interface Autoconfiguration . . . . . . . . . . . 10
4.2.2. Provider-Aggregated Prefix Autoconfiguration . . . . . 12
4.2.3. Provider-Independent Prefix Autoconfiguration . . . . 12
4.3. Enterprise Border Gateway (EBG) Autoconfiguration . . . . 13
4.4. VET Host Autoconfiguration . . . . . . . . . . . . . . . . 13
5. Post-Autoconfiguration Operation . . . . . . . . . . . . . . . 13
5.1. Routing Protocol Participation . . . . . . . . . . . . . . 13
5.2. DHCP Prefix Delegation Maintenance . . . . . . . . . . . . 14
5.3. Forwarding Packets . . . . . . . . . . . . . . . . . . . . 14
5.4. IPv6 Prefix Mapping . . . . . . . . . . . . . . . . . . . 15
5.5. IPv6 Router Discovery . . . . . . . . . . . . . . . . . . 16
5.6. Fortifying VET with SEAL . . . . . . . . . . . . . . . . . 17
5.7. Enterprise-Local Communications . . . . . . . . . . . . . 17
5.8. Multicast . . . . . . . . . . . . . . . . . . . . . . . . 18
5.9. Service Discovery . . . . . . . . . . . . . . . . . . . . 18
5.10. Enterprise Partitioning . . . . . . . . . . . . . . . . . 18
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. Related Work . . . . . . . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 20
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.1. Normative References . . . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . . 21
Appendix A. Duplicate Address Detection (DAD) Considerations . . 24
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 24
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 28
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1. Introduction
Enterprise networks [RFC4852] connect routers over various link types
(see: [RFC4861], Section 2.2). Certain Mobile Ad-hoc Networks
(MANETs) [RFC2501] can be considered as a challenging example of an
enterprise network, in that their topologies may change dynamically
over time and that they may employ little/no active management by a
centralized network administrative authority. These specialized
characteristics for MANETs require careful consideration, but the
same principles apply equally to other enterprise network scenarios.
This document specifies a Virtual Enterprise Traversal (VET)
abstraction for autoconfiguration and runtime operation of nodes in
enterprises, where addresses of different scopes may be assigned on
various types of interfaces with diverse properties. Both IPv4
[RFC0791] and IPv6 [RFC2460] are discussed within this context. The
use of standard DHCP [RFC2131][RFC3315] and neighbor discovery
[RFC0826][RFC4861] mechanisms is assumed unless otherwise specified.
Provider-edge Interfaces
x x x
| | |
+--------------------+---+--------+----------+ E
| | | | | n
| I | | .... | | t
| n +---+---+--------+---+ | e
| t | +--------+ /| | r
| e I x----+ | Host | I /*+------+--< p I
| r n | |Function| n|**| | r n
| n t | +--------+ t|**| | i t
| a e x----+ V e|**+------+--< s e
| l r . | E r|**| . | e r
| f . | T f|**| . | f
| V a . | +--------+ a|**| . | I a
| i c . | | Router | c|**| . | n c
| r e x----+ |Function| e \*+------+--< t e
| t s | +--------+ \| | e s
| u +---+---+--------+---+ | r
| a | | .... | | i
| l | | | | o
+--------------------+---+--------+----------+ r
| | |
x x x
Enterprise-edge Interfaces
Figure 1: Enterprise Router Architecture
Figure 1 above depicts the architectural model for an enterprise
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router. As shown in the figure, an enterprise router may have a
variety of interface types including enterprise-edge, enterprise-
interior, provider-edge, internal-virtual, as well as VET interfaces
used for encapsulation of inner IP packets within outer IP headers.
The different types of interfaces are defined, and the
autoconfiguration mechanisms used for each type are specified. This
architecture applies equally for MANET routers, in which enterprise-
interior interfaces correspond to the wireless multihop radio
interfaces typically associated with MANETs. Out of scope for this
document is the autoconfiguration of provider interfaces, which must
be coordinated in a manner specific to the service provider's
network.
The VET specification represents a functional superset of 6over4
[RFC2529] and ISATAP [RFC5214], and further supports additional
encapsulations such as IPsec [RFC4301], SEAL [I-D.templin-seal], etc.
As a result, VET provides a map-and-encaps architecture using
IP-in-IP tunneling based on both forwarding table and mapping service
lookups (defined herein).
The VET principles can be either directly or indirectly traced to the
deliberations of the ROAD group in January 1992, and also to still
earlier works including NIMROD [RFC1753], the Catenet model for
internetworking [CATENET][IEN48][RFC2775], etc. [RFC1955] captures
the high-level architectural aspects of the ROAD group deliberations
in a "New Scheme for Internet Routing and Addressing [ENCAPS] for
IPNG".
VET is related to the present-day activites of the IETF autoconf,
dhc, ipv6, manet and v6ops working groups.
2. Terminology
The mechanisms within this document build upon the fundamental
principles of IP-within-IP encapsulation. The terms "inner" and
"outer" are used throughout this document to respectively refer to
the innermost IP {address, protocol, header, packet, etc.} *before*
encapsulation, and the outermost IP {address, protocol, header,
packet, etc.} *after* encapsulation. VET also supports the inclusion
of "mid-layer" encapsulations between the inner and outer layers,
including IPSec [RFC4301], the Subnetwork Encapsulation and
Adaptation Layer (SEAL) [I-D.templin-seal], etc.
The terminology in the normative references apply; the following
terms are defined within the scope of this document:
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subnetwork
the same as defined in [RFC3819].
enterprise
the same as defined in [RFC4852].
site
a logical and/or physical grouping of interfaces that connect a
topological area less than or equal to the enterprise in scope. A
site within an enterprise can be considered as an enterprise unto
itself.
Mobile Ad-hoc Network (MANET)
a connected topology of mobile or fixed routers that maintain a
routing structure among themselves over MANET link types
[I-D.clausen-manet-linktype], where a wide variety of MANETs share
common properties with enterprise networks. Further information
on MANETs can be found in [RFC2501].
enterprise/site/MANET
throughout the remainder of this document, the term "enterprise"
is used to collectively refer to any of enterprise/site/MANET,
i.e., the VET mechanisms and operational principles apply equally
to enterprises, sites and MANETs.
enterprise router
an Enterprise Interior Router, Enterprise Border Router, or
Enterprise Border Gateway. As depicted in Figure 1, an enterprise
router comprises a router function, a host function, one or more
enterprise-interior interfaces and zero or more internal virtual,
enterprise-edge, provider-edge and VET interfaces.
Enterprise Interior Router (EIR)
a fixed or mobile enterprise router that forwards packets over one
or more sets of enterprise-interior interface; each set connected
to a distinct enterprise.
Enterprise Border Router (EBR)
an EIR that connects edge networks to the enterprise, and/or
connects multiple enterprises together. An EBR configures a
seperate VET interface over each set of enterprise-interior
interfaces that connect the EBR to each distinct enterprise, i.e.,
an EBR may configure mulitple VET interfaces - one for each
distinct enterprise. All EBRs are also EIRs.
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Enterprise Border Gateway (EBG)
an EBR that either directly or indirectly connects the enterprise
to provider networks and can delegate addresses/prefixes to other
EBRs within the enterprise. All EBGs are also EBRs.
internal-virtual interface
a virtual interface that is a special case of either an
enterprise-edge or an enterprise-interior interface. Internal-
virtual interfaces that are also enterprise-edge interfaces are
often loopback interfaces of some form. Internal-virtual
interfaces that are also enterprise-interior interfaces are often
tunnel interfaces of some form configured over another enterprise-
interior interface.
enterprise-edge interface
an EBR's attachment to a link (e.g., an ethernet, a wireless
personal area network, etc.) on an arbitrarily-complex edge
network that the EBR connects to an enterprise and/or to provider
networks.
provider-edge interface
an EBR's attachment to the Internet, or to a provider network
outside of the enterprise via which the Internet can be reached.
enterprise-interior interface
a EIR's attachment to a link within an enterprise. An enterprise-
interior interface is "neutral" in its orientation, i.e., it is
inherently neither an enterprise-edge nor provider-edge interface.
In particular, a packet may need to be forwarded over several
enterprise-interior interfaces before it is forwarded via either
an enterprise-edge or provider-edge interface.
Enterprise Local Address (ELA)
an enterprise-scoped IP address (e.g., an IPv6 Unique Local
Address [RFC4193], an IPv4 privacy address [RFC1918], etc.) that
is assigned to an enterprise-interior interface and unique within
the enterprise. ELAs are used as identifiers for operating the
routing protocol and/or locators for packet forwarding within the
scope of the enterprise; ELAs are also used as *outer* IP
addresses during encapsulation.
Virtual Enterprise Traversal (VET)
an abstraction that uses IP-in-IP encapsulation to span a multi-
link enterprise in a single (inner) IP hop.
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VET interface
an EBR's Non-Broadcast, Multiple Access interface used for Virtual
Enterprise Traversal. The EBR configures a VET interface over a
set of underlying enterprise-interior interface(s) belonging to
the same enterprise. When there are multiple distinct enterprises
(each with their own distinct set of enterprise-interior
interfaces), the EBR configures a separate VET interface over each
set of enterprise-interior interfaces, i.e., the EBR configures
multiple VET interfaces.
The VET interface encapsulates each inner IP packet in any mid-
layer headers plus an outer IP header then forwards it on an
underlying enterprise-interior interface such that the TTL/Hop
Limit in the inner header is not decremented as the packet
traverses the enterprise. The VET interface presents an automatic
tunneling abstraction that represents the enterprise as a single
IP hop.
The following additional acronyms are used throughout the document:
CGA - Cryptographically Generated Address
DHCP[v4,v6] - the Dynamic Host Configuration Protocol
FIB - Forwarding Information Base
ISATAP - Intra-Site Automatic Tunnel Addressing Protocol
ND - Neighbor Discovery
PIO - Prefix Information Option
PRL - Potential Router List
RIO - Route Information Option
RS/RA - IPv6 Neighbor Discovery Router Solicitation/Advertisement
SEAL - Subnetwork Encapsulation and Adaptation Layer
SLAAC - IPv6 StateLess Address AutoConfiguation
3. Enterprise Characteristics
Enterprises consist of links that are connected by enterprise routers
as depicted in Figure 1. All enterprise routers are also Enterprise
Interior Routers (EIRs), and typically participate in a routing
protocol over enterprise-interior interfaces to discover routes that
may include multiple Layer-2 or Layer-3 forwarding hops. Enterprise
Border Routers (EBRs) are EIRs that connect edge networks and/or join
multiple enterprises together, while Enterprise Border Gateways
(EBGs) are EBRs that either directly or indirectly connect
enterprises to provider networks.
An enterprise may be as simple as a small collection of enterprise
routers (and their attached edge networks); an enterprise may also
contain other enterprises and/or be a subnetwork of a larger
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enterprise. An enterprise may further encompass a set of branch
offices and/or nomadic hosts connected to a home office over one or
several service providers, e.g., through Virtual Private Network
(VPN) tunnels.
Enterprises that comprise link types with sufficiently similar
properties (e.g., Layer-2 (L2) address formats, maximum transmission
units (MTUs), etc.) can configure a sub-IP layer routing service such
that IP sees the enterprise as an ordinary shared link the same as
for a (bridged) campus LAN. In that case, a single IP hop is
sufficient to traverse the enterprise without IP layer encapsulation.
Enterprises that comprise link types with diverse properties and/or
configure multiple IP subnets must also provide a routing service
that operates as an IP layer mechanism. In that case, multiple IP
hops may be necessary to traverse the enterprise such that specific
autoconfiguration procedures are necessary to avoid multilink subnet
issues [RFC4903]. In particular, we describe herein the use of IP-
in-IP encapsulation to span the enterprise in a single (inner) IP hop
in order to avoid the multilink subnet issues that arise when
enterprise-interior interfaces are used directly by applications.
Conceptually, an enterprise router (i.e, an EIR/EBR/EBG) embodies
both a host function and router function. The host function supports
global-scoped communications over any of the enterprise router's non-
enterprise-interior interfaces according to the weak end system model
[RFC1122] and also supports enterprise-local-scoped communications
over its enterprise-interior interfaces. The router function
connects the enterprise router's attached edge networks to the
enterprise and/or connects the enterprise to other networks including
the Internet (see: Figure 1).
In addition to other interface types, EBRs configure VET interfaces
that view all other EBRs in an enterprise as single-hop neighbors,
where the enterprise can also appear as a single IP hop within
another enterprise. EBRs configure a separate VET interface for each
distinct enterprise to which they connect, and discover a list of
EBRs for each VET interface that can be used for forwarding packets
to off-enterprise destinations. The following sections present the
Virtual Enterprise Traversal approach.
4. Autoconfiguration
EIRs configure enterprise-interior interfaces. An EBR is an EIR that
also configures enterprise-edge and VET interfaces. An EBG is an EBR
that also either directly or indirectly connects the enterprise to a
provider network. EIRs, EBRs and EBGs configure themselves for
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operation according to the following subsections:
4.1. Enterprise Interior Router (EIR) Autoconfiguration
EIRs configure enterprise-interior interfaces and engage in routing
protocols over those interfaces.
When an EIR joins an enterprise, it first configures a unique IPv6
link-local address on each enterprise-interior interface that
requires an IPv6 link-local capability and an IPv4 link-local address
on each enterprise-interior interface that requires an IPv4 link-
local capability. IPv6 link-local address generation mechanisms that
provide sufficient uniqueness include Cryptographically Generated
Addresses (CGAs) [RFC3972], IPv6 Privacy Addresses [RFC4941],
StateLess Address AutoConfiguration (SLAAC) using EUI-64 interface
identifiers [RFC4862], etc. The mechanisms specified in [RFC3927]
provide an IPv4 link-local address generation capability.
Next, the EIR configures an Enterprise Local Address (ELA) of the
outer IP protocol version on each of its enterprise-interior
interfaces and engages in any routing protocols on those interfaces.
The EIR can configure an ELA via explicit management, DHCP
autoconfiguration, pseudo-random self-generation from a suitably
large address pool, or through an alternate autoconfiguration
mechanism. In some enterprise use cases (e.g., highly dynamic
MANETs), assignment of ELAs as singleton addresses (i.e., as /32s for
IPv4 and /128s for IPv6) may be necessary to avoid multilink subnet
issues.
EIRs that configure ELAs using DHCP may require relay support from
other EIRs within the enterprise; the EIR can alternatively configure
both a DHCP client and relay that are connected, e.g., via a pair of
back-to-back connected ethernet interfaces, a tun/tap interface, a
loopback interface, custom S/W coding, etc. For DHCPv6, relays that
do not already know the ELA of a server relay requests to the
'All_DHCP_Servers' site-scoped IPv6 multicast group. For DHCPv4,
relays that do not already know the ELA of a server relay requests to
the site-scoped IPv4 multicast group address TBD (see: Section 6).
DHCPv4 servers that delegate ELAs join the TBD multicast group and
service any DHCPv4 messages received for that group.
Self-generation of ELAs for IPv6 can be from a large IPv6 local-use
address range, e.g., IPv6 Unique Local Addresses [RFC4193]. Self-
generation of ELAs for IPv4 can be from a large IPv4 private address
range (e.g., [RFC1918]). When self-generation is used alone, the EIR
must continuously monitor the ELAs for uniqueness, e.g., by
monitoring the routing protocol, but care must be taken in the
interaction of this monitoring with existing mechanisms.
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A combined approach using both DHCP and self-generation is also
possible in which the EIR first self-generates a temporary ELA used
only for the purpose of procuring an actual ELA taken from a disjoint
addressing range. The EIR then assigns the temporary ELA to an
enterprise-interior interface, engages in the routing protocol and
performs a DHCP client/relay exchange using the temporary ELA as the
address of the relay. When the DHCP server delegates an actual ELA,
the EIR abandons the temporary ELA, assigns the actual ELA to the
enterprise-interior interface and re-engages in the routing protocol.
4.2. Enterprise Border Router (EBR) Autoconfiguration
EBRs are EIRs that configure VET interfaces over distinct sets of
underlying enterprise-interior interfaces; an EBR can connect to
multiple enterprises, in which case it would configure multiple VET
interfaces. EBRs perform the following autoconfiguration operations:
4.2.1. VET Interface Autoconfiguration
VET interface autoconfiguration entails: 1) interface initialization,
2) EBG discovery and enterprise identification, and 3) IPv6 stateless
address autoconfiguration. These functions are specified in the
following sections:
4.2.1.1. Interface Initialization
EBRs configure a VET interface over a set of underlying enterprise-
interior interfaces belonging to the same enterprise, where the VET
interface presents a virtual view of all EBRs in the enterprise as
single hop neighbors through the use of IP-in-IP encapsulation.
When IPv6 and IPv4 are used as the inner/outer protocols
(respectively), the EBR autoconfigures an ISATAP link-local address
([RFC5214], Section 6.2) on the VET interface to support packet
forwarding and operation of the IPv6 neighbor discovery protocol.
The ISATAP link-local address embeds an IPv4 ELA assigned to an
underlying enterprise-interior interface, and need not be checked for
uniqueness since the IPv4 ELA itself was already determined to be
unique (see: Section 4.1). Link-local address configuration for
other inner/outer IP protocol combinations is through administrative
configuration or through an unspecified alternate method.
After the EBR configures a VET interface, it can communicate with
other EBRs as single-hop neighbors from the viewpoint of the inner IP
protocol (where discovery of other EBRs is discussed in Section 5.5).
The EBR can also confirm reachability of other EBRs through Neighbor
Discovery (ND) and/or DHCP exchanges over the VET interface, or
through other means such as information conveyed in the routing
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protocol.
The EBR must be able to detect and recover from the loss of VET
interface neighbors due to, e.g., network partitions, node failures,
etc. Mechanisms specified outside of this document such as
monitoring the routing protocol, ND beaconing/polling, DHCP renewals/
leasequeries, upper layer protocol hints of forward progress,
bidirectional forward detection, detection of network attachment,
etc. can be used according to the particular deployment scenario.
4.2.1.2. Enterprise Border Gateway Discovery and Enterprise
Identification
The EBR next discovers a list of EBGs for each of its VET interfaces,
i.e., for each enterprise it connects to. The list can be discovered
through information conveyed in the routing protocol and/or through
the Potential Router List (PRL) discovery mechanisms outlined in
[RFC5214], Section 8.3.2. In multicast-capable enterprises, they can
also listen for advertisements on the 'rasadv' [RASADV] IPv4
multicast group address.
In particular, whether or not routing information is available the
EBR can discover the list of EBGs by resolving an identifying name
for the enterprise using an enterprise local name resolution service
(e.g., an enterprise-local DNS service, LLMNR [RFC4759], etc.). In
the absence of other identifying names, the EBR can resolve either
the hostname "isatap" or the FQDN "isatap.example.com" if an
enterprise-specific suffix "example.com" is known.
Identifying names along with addresses of EBGs and/or the prefixes
they aggregate serve as an identifier for the enterprise.
4.2.1.3. IPv6 Stateless Address Autoconfiguration (SLAAC)
When IPv6 is used as the inner protocol, the EBR sends unicast IPv6
Router Solicitation (RS) messages over its VET interface(s) to
receive Router Advertisements (RAs) from EBGs. When the EBR receives
an RA containing Prefix Information Options (PIOs) with the 'A' and
'L' bits set to 1, it autoconfigures IPv6 addresses from the prefixes
using SLAAC and assigns them to the VET interface. (When IPv4 is
used as the outer IP protocol, the addresses are autoconfigured and
assigned as ISATAP addresses the same as specified in [RFC5214].)
The use of DHCPv6 for address configuration on VET interfaces is
undefined.
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4.2.2. Provider-Aggregated Prefix Autoconfiguration
EBRs acquire provider-aggregated prefixes through autoconfiguration
exchanges with EBGs over VET interfaces. When IPv4 is used as the
inner IP protocol, the EBR acquires provider-aggregated prefixes via
an unspecified automated IPv4 prefix delegation exchange, explicit
management, etc.
When IPv6 is used as the inner IP protocol, the EBR acquires
provider-aggregated prefixes via IPv6 Neighbor Discovery and DHCPv6
Prefix Delegation exchanges. If the EBR receives an RA from an EBG
that contains PIOs with the 'L' bit set to 0, it can use the PIOs as
hints of prefixes the DHCPv6 server may be willing to delegate (see:
Section 5.5). Whether or not such hints are available, the EBR
(acting as a requesting router) can use DHCPv6 prefix delegation
[RFC3633] over the VET interface to obtain Provider-Aggregated IPv6
prefixes from the server (acting as a delegating router).
The EBR obtains prefixes using either a 2-message or 4-message DHCPv6
exchange [RFC3315]. For example, to perform the 2-message exchange
the EBR's DHCPv6 client forwards a Solicit message with an IA_PD
option to its DHCPv6 relay, i.e., the EBR acts as a combined client/
relay (see: Section 4.1). The relay then forwards the message over
the VET interface to the EBG. The forwarded Solicit message will
elicit a reply from the server containing provider-aggregated IPv6
prefix delegations.
The EBR can propose a specific prefix to the DHCPv6 server per
Section 7 of [RFC3633], e.g., if a prefix delegation hint is
available. The server will check the proposed prefix for consistency
and uniqueness, then return it in the reply to the EBR if it was able
to perform the delegation.
After the EBR received provider-aggregated prefix delegations, it can
provision the prefixes on its enterprise-edge interfaces as well as
on other VET interfaces for which it is configured as an EBG.
4.2.3. Provider-Independent Prefix Autoconfiguration
Independent of any provider-aggregated prefixes (see: Section 4.2.2),
EBRs can also acquire and use provider-independent and/or self-
configured prefixes (e.g., IPv6 Unique Local Addresses (ULAs)
[RFC4193][I-D.ietf-ipv6-ula-central]).
EBRs can retain their provider-independent addresses/prefixes as they
travel between visited enterprise networks as long as they register
the prefixes with new enterprises and (preferrably) withdraw the
prefixes from departed enterprises. EBRs can use Secure Neighbor
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Discovery (SEND) [RFC3971] to prove ownership of their provider-
independent prefixes and can use DHCPv6 prefix delegation to register
the prefixes in the new enterprise. EBRs can also act as delegating
routers to sub-delegate portions of their provider-independent
prefixes to requesting routers on their enterprise edge interfaces
and on VET interfaces for which they are configured as EBGs.
4.3. Enterprise Border Gateway (EBG) Autoconfiguration
EBGs are EBRs that connect enterprises to a service provider either
directly via provider-edge interfaces or indirectly via another
enterprise. EBGs configure provider-edge interfaces in a manner that
is specific to its provider connections. EBGs also configure a DHCP
relay/server that can service prefix delegation requests.
For each VET interface on which it is configured as an EBG, the EBG
must arrange to add its enterprise-interior interface addresses to
the PRL (see: Section 4.2.1.2), and must maintain these resource
records in accordance with ([RFC5214], Section 9). In particular,
for each such VET interface the EBG adds its enterprise-interior
interface addresses to the hostname "isatap" and/or the FQDN
"isatap.example.com".
4.4. VET Host Autoconfiguration
Non-routing hosts that cannot be attached via an EBR's enterprise-
edge interface (e.g., nomadic laptops that connect to a home office
via a Virtual Private Network (VPN)) can instead be configured for
operation as a simple host connected to the VET interface. Such VET
hosts configure one or more VET interfaces over corresponding sets of
enterprise-interior interfaces exactly as for EBRs, but they do not
configure a router function nor provide packet forwarding services.
VET hosts can then send packets to other hosts on the VET interface,
or to off-enterprise destinations via a next-hop EBR.
5. Post-Autoconfiguration Operation
The following sections discuss post-autoconfiguration operations:
5.1. Routing Protocol Participation
After an EIR has been autoconfigured, it participates in any routing
protocols over enterprise-interior interfaces and forwards outer IP
packets within the enterprise as for any ordinary router.
EBRs can additionally engage in any inner IP routing protocols over
enterprise-edge, provider-edge and VET interfaces, and can use those
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interfaces for forwarding inner IP packets to off-enterprise
destinations. Note that these inner IP routing protocols are
separate and distinct from any enterprise-interior routing protocols.
5.2. DHCP Prefix Delegation Maintenance
When DHCP prefix delegation is used, the DHCP server ensures that the
delegations are unique and that the EBG's router function will
forward IP packets over the VET interface to the EBRs to which the
prefixes were delegated. The EBRs can then sub-delegate the prefixes
to other requesting routers.
The DHCP prefix delegations remain active as long as the EBR
continues to issue renewals over the VET interface before lease
lifetimes expire. The lease lifetime also keeps the delegation state
active even if communications between the EBR and DHCP server are
disrupted for a period of time (e.g., due to an enterprise network
partition) before being reestablished (e.g., due to an enterprise
network merge). When the EBR leaves the enterprise, it should first
release its delegated provider-dependent prefixes and unregister its
provider-independent prefixes to avoid black-holing future
communications.
Since the DHCP client and relay are co-resident on the same EBR, no
special coordination is necessary for the EBG to maintain routing
information. The EBG simply retains Forwarding Information Base
(FIB) entries that identify the EBR as the next-hop toward the
prefixes over the VET interface.
5.3. Forwarding Packets
VET nodes forward packets by consulting the FIB to determine a
specific EBR/EBG as the next-hop router on the VET interface. When
multiple next-hop routers are available, VET nodes can use default
router preferences, routing protocol information, traffic engineering
configurations, etc. to select the best exit router. When there is
no FIB information available, VET nodes can discover the next-hop
EBR/EBG through the mechanisms specified in Section 5.5.
VET interfaces encapsulate inner IP packets in any mid-layer headers
followed by an outer IP header according to the specific
encapsulation type (e.g., [RFC4301][RFC5214][I-D.templin-seal]); they
next submit the encapsulated packet to the outer IP forwarding engine
for transmission on an underlying enterprise-interior interface.
For forwarding to next-hop addresses over VET interfaces that use
IPv6-in-IPv4 encapsulation, VET nodes determine the outer destination
address through static extraction of the IPv4 address embedded in the
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next-hop ISATAP address. For other IP-in-IP encapsulations,
determination of the outer destination address is through
administrative configuration or through an unspecified alternate
method.
5.4. IPv6 Prefix Mapping
For each of the /64 prefixes they aggregate, EBRs must respond to
messages addressed to the prefix's IPv6 subnet router anycast address
[RFC4291]. EBRs must also publish the prefixes in the enterprise-
local name service using the domain name suffix 'isatap.example.com';
for publications within the global DNS itself, the domain name suffix
'isatap.net' is used instead.
EBRs in enterprises that are managed under a cooperative
administrative authority should publish their prefixes in the
enterprise name service (e.g., the DNS [RFC1035]). EBRs in
enterprises that are managed in a distributed fashion should
implement their own distributed name resolution services (e.g., LLMNR
[RFC4759]).
The EBR publishes the prefix as a domain name consisting of a
sequence of 16 nibbles in reverse order the same as in ([RFC3596],
Section 2.5). For example, the EBR publishes the prefix '2001:
DB8::/64' as:
'0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.isatap.example.com'.
The EBR (or one of a group of EBRs that service the same prefix)
includes in each prefix publication IPv4 addresses (e.g., in DNS A
records) taken from the EBRs' enterprise interior interfaces. In
enterprises with a cooperative administrative authority, EBRs
coordinate their publications with an administrator and/or by using a
secure automated name service update mechanism (e.g., [RFC3007]). In
enterprises that are managed in a distributed fashion, EBRs publish
their prefixes through direct responses to distributed name
resoultion service queries via a mechanism such as LLMNR. In this
way, the enterprise name service itself becomes an extension of the
enterprise's PRL, and the global DNS serves as the PRL for the entire
Internet.
Prefix publication in new enterprises should be coordinated in
conjunction with prefix withdrawls in recently departed enterprises
such that mobility events are handled gracefully. In this way, all
of the EBRs/EBGs on the path from the VET node to the Internet core
can adjust their forwarding information to track the node's provider-
independent prefixes as it moves between enterprises.
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5.5. IPv6 Router Discovery
EBGs follow the router and prefix discovery procedures specified in
([RFC5214], Section 8.2). They send RAs over VET interfaces for
which they are gateways with PIOs for SLAAC, with the 'M' flag set to
0 and with the 'O' flag set to indicate whether "other" DHCP services
are available. EBGs can also include PIOs with the 'L' bit set to 0
and with a prefix such as '2001:DB8::/48' as a hint of an aggregated
prefix from which it is willing to delegate longer prefixes.
VET nodes follow the router and prefix discovery procedures specified
in ([RFC5214], Section 8.3). They discover EBGs within the
enterprise as specified in Section 4.2.1.2 and they can also discover
destination-specific next-hop EBRs within the enterprise by querying
the name service for the /64 IPv6 prefix corresponding to a packet's
destination address. For example, for the IPv6 destination address
'2001:DB8:1:2::1' the VET node can lookup the domain name:
'2.0.0.0.1.0.0.0.8.b.d.0.1.0.0.2.isatap.example.com'.
If the name service lookup succeeds, it will return IPv4 addresses
(e.g., in DNS A records) that correspond to the enterprise interior
interfaces of potential next-hop EBRs. If the lookup fails, the VET
node can continue to forward its packets to a default EBG.
When a VET node forwards a packet to an EBG that has a mapping for
the destination, the EBG forwards the packet to a next-hop EBR on the
VET interface and returns an ICMP redirect. If the packet's source
address is on-link on the VET interface (i.e., the VET node is a
host), the EBG returns an ordinary "router-to-host" redirect with the
source address of the packet as its destination. If the packet's
source address is not on-link (i.e., the VET node is an EBR), the EBG
instead returns a "router-to-router" redirect with the link-local
ISATAP address of the originating EBR as its destination. The EBG
also includes in the redirect one or more link-layer address options
containing IPv4 addresses of candidate next-hop EBRs that were
discovered through the mapping lookup, where the target link-layer
address options are formatted exactly as specified in [RFC2529].
That is to say, the redirect may contain multiple target link-layer
address options; each representing the link-layer address of a
candidate next-hop EBR.
When the VET node receives a redirect, it discovers the link layer
addresses of candidate next-hop EBRs by examining the target link-
layer address options included in the redirect. The VET node then
sends a SEND-protected RS to a candidate next-hop EBR over the VET
interface with a link-local CGA address as the source, the IPv6
subnet router anycast address corresponding to the original packet's
destination address as the destination, and a link-layer (i.e., IPv4)
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destination corresponding to the candidate EBR. The VET node also
includes a Route Information Option (RIO) [RFC4191] in the RS that
contains the /64 prefix of the original packet's source address.
When the next-hop EBR receives the RS, it uses SEND to verify the
signature then installs the IPv6 prefix in the RIO as an egress
filter entry. The next-hop EBR then sends a SEND-protected RA back
to the VET node with an RIO containing an IPv6 prefix for the
original packet's destination. The VET node verifies the RA's
signature, then installs the prefix in its FIB. If the VET node does
not receive an RA, it can try again by sending an RS to another
candidate next-hop EBR over the VET interface.
After the initial RS/RA exchange, the VET node should send periodic
RS's to elicit RA's from the next-hop EBR and refresh prefix
lifetimes as long as traffic is flowing. If the VET node detects
that the path is failing, it should delete the route from the FIB and
allow subsequent packets to flow through a default EBG again until
another redirect is received. If the next-hop EBR receives a packet
for which it has somehow lost its routing information for the final
destination, it sends a SEND-proteceted RA back to the VET node with
an RIO containing an IPv6 prefix with router lifetime set to 0. This
will cause the node to delete the route from the FIB, and allows for
graceful handling of mobility events.
VET nodes must only accept PIOs, M/O flag settings and default router
preferences in RAs that are received from EBGs; they MUST NOT accept
them from ordinary EBRs.
5.6. Fortifying VET with SEAL
Enterprises should use SEAL encapsulation [I-D.templin-seal] in
conjunction with VET to accommdate path MTU diversity, and to defend
against rogue routers and source address spoofing. In particular,
EBRs can track the SEAL_ID sequence in packets sent by trusted
routers and discard packets that have SEAL_ID values outside of the
sender's current window. They can also use egress filtering based on
prefix information received in SEND-protected RAs to detect source
address spoofing.
To maintain synchronization, the EBR resets its cached SEAL_IDs for
correspondent EBRs/EBGs within the enterprise whenever it receives a
fresh SEND-protected RS/RA.
5.7. Enterprise-Local Communications
When permitted by policy, end systems that configure the endpoints of
enterprise-local communications can avoid VET interface encapsulation
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by directly invoking the outer IP protocol using ELAs assigned to
their enterprise-interior interfaces. For example, when the outer
protocol is IPv4, end systems can use IPv4 ELAs for enterprise-local
communications over their enterprise-interior interfaces without
using the VET interface.
5.8. Multicast
In multicast-capable deployments, EIRs provide an enterprise-wide
multicasting service such as Simplified Multicast Forwarding (SMF)
[I-D.ietf-manet-smf] over their enterprise-interior interfaces such
that outer IP multicast messages of site- or greater scope will be
propagated across the enterprise. For such deployments, VET hosts
and EBRs can also provide an inner IP multicast/broadcast capability
over their VET interfaces through mapping of the inner IP multicast
address space to the outer IP multicast address space.
VET hosts and EBRs encapsulate inner IP multicast messages sent over
the VET interface in any mid-layer headers (e.g., IPsec, SEAL, etc.)
plus an outer IP header with a site-scoped outer IP multicast address
as the destination. For the case of IPv6 and IPv4 as the inner/outer
protocols (respectively), [RFC2529] provides mappings from the IPv6
multicast address space to the IPv4 multicast address space. For
other IP-in-IP encapsulations, mappings are established through
administrative configuration or through an unspecified alternate
method.
For multicast-capable enterprises, use of the inner IP multicast
service for operating the ND protocol over the VET interface is
available but should be used sparingly to minimize enterprise-wide
flooding.
5.9. Service Discovery
VET hosts and EBRs can peform enterprise-wide service discovery using
a suitable name-to-address resolution service. Examples of flooding-
based services include the use of LLMNR [RFC4759] over the VET
interface or mDNS [I-D.cheshire-dnsext-multicastdns] over an
underlying enterprise-interior interface. More scalable and
efficient service discovery mechanisms are for further study.
5.10. Enterprise Partitioning
EBGs can physically partition an enterprise by configuring multiple
VET interfaces over multiple distinct sets of underlying interfaces.
In that case, each partition (i.e., each VET interface) must
configure its own distinct PRL zone (e.g., 'zone1.example.com',
'zone2.example.com', etc.).
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EBGs can logically partition an enterprise using a single VET
interface by sending RAs with PIOs containing different IPv6 subnet
prefixes to nodes in different logical partitions. EBGs can identify
partitions, e.g., by examining IPv4 prefixes, observing the
interfaces over which RSs are received, etc. In that case, a single
PRL zone can cover all partitions.
6. IANA Considerations
A Site-Local Scope IPv4 multicast group (TBD) for DHCPv4 server
discovery is requested. The allocation should be taken from the
239.255.000.000-239.255.255.255 Site-Local Scope range in the IANA
'multicast-addresses' registry.
7. Security Considerations
Security considerations for MANETs are found in [RFC2501].
Security considerations with tunneling that apply also to VET are
found in [RFC2529][RFC5214]. In particular, VET nodes must verify
that the outer IP source address of a packet received on a VET
interface is correct for the inner IP source address using the
procedures specified in ([RFC5214], Section 7.3).
The securing methods specified in Section 5.6 provide additional
mitigation against both rogue EBRs (via SEND) and source address
spoofing (via the SEAL_ID and prefix-based egress filtering).
8. Related Work
The authors acknowledge the work done by Brian Carpenter and Cyndi
Jung in [RFC2529] that introduced the concept of intra-site automatic
tunneling. This concept was later called: "Virtual Ethernet" and
investigated by Quang Nguyen under the guidance of Dr. Lixia Zhang.
As for this document, these architectural principles also follow from
earlier works articulated by the ROAD group deliberations of 1992.
Telcordia has proposed DHCP-related solutions for the CECOM MOSAIC
program. The Naval Research Lab (NRL) Information Technology
Division uses DHCP in their MANET research testbeds. Various
proposals within the IETF have suggested similar mechanisms.
[I-D.ietf-v6ops-tunnel-security-concerns] discusses security concerns
regarding tunneling mechanisms that may subvert security through
Network Address Translator (NAT) traversal.
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An automated IPv4 prefix delegation mechanism is proposed in
[I-D.ietf-dhc-subnet-alloc].
9. Acknowledgements
The following individuals gave direct and/or indirect input that was
essential to the work: Jari Arkko, Teco Boot, Emmanuel Bacelli, Brian
Carpenter, James Bound, Thomas Clausen, Joel Halpern, Bob Hinden,
Sapumal Jayatissa, Dan Jen, Tony Li, Joe Macker, Thomas Narten,
Alexandru Petrescu, John Spence, Jinmei Tatuya, Dave Thaler, Ole
Troan, Michaela Vanderveen, Lixia Zhang and others in the IETF
AUTOCONF and MANET working groups. Many others have provided
guidance over the course of many years.
10. Contributors
The following individuals have contributed to this document:
Eric Fleischman (eric.fleischman@boeing.com)
Thomas Henderson (thomas.r.henderson@boeing.com)
Steven Russert (steven.w.russert@boeing.com)
Seung Yi (seung.yi@boeing.com)
Ian Chakeres (ian.chakeres@gmail.com) contributed to earlier versions
of the document.
11. References
11.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC0826] Plummer, D., "Ethernet Address Resolution Protocol: Or
converting network protocol addresses to 48.bit Ethernet
address for transmission on Ethernet hardware", STD 37,
RFC 826, November 1982.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
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(IPv6) Specification", RFC 2460, December 1998.
[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.
[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.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", RFC 3596,
October 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.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, November 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[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.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
11.2. Informative References
[CATENET] Pouzin, L., "A Proposal for Interconnecting Packet
Switching Networks", May 1974.
[I-D.cheshire-dnsext-multicastdns]
Cheshire, S. and M. Krochmal, "Multicast DNS",
draft-cheshire-dnsext-multicastdns-07 (work in progress),
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September 2008.
[I-D.clausen-manet-linktype]
Clausen, T., "The MANET Link Type",
draft-clausen-manet-linktype-00 (work in progress),
October 2008.
[I-D.ietf-autoconf-manetarch]
Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc
Network Architecture", draft-ietf-autoconf-manetarch-07
(work in progress), November 2007.
[I-D.ietf-dhc-subnet-alloc]
Johnson, R., "Subnet Allocation Option",
draft-ietf-dhc-subnet-alloc-07 (work in progress),
July 2008.
[I-D.ietf-ipv6-ula-central]
Hinden, R., "Centrally Assigned Unique Local IPv6 Unicast
Addresses", draft-ietf-ipv6-ula-central-02 (work in
progress), June 2007.
[I-D.ietf-manet-smf]
Macker, J. and S. Team, "Simplified Multicast Forwarding
for MANET", draft-ietf-manet-smf-08 (work in progress),
November 2008.
[I-D.ietf-v6ops-tunnel-security-concerns]
Hoagland, J., Krishnan, S., and D. Thaler, "Security
Concerns With IP Tunneling",
draft-ietf-v6ops-tunnel-security-concerns-01 (work in
progress), October 2008.
[I-D.templin-seal]
Templin, F., "The Subnetwork Encapsulation and Adaptation
Layer (SEAL)", draft-templin-seal-23 (work in progress),
August 2008.
[IEN48] Cerf, V., "The Catenet Model for Internetworking",
July 1978.
[RASADV] Microsoft, "Remote Access Server Advertisement (RASADV)
Protocol Specification", October 2008.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1753] Chiappa, J., "IPng Technical Requirements Of the Nimrod
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Routing and Addressing Architecture", RFC 1753,
December 1994.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC1955] Hinden, R., "New Scheme for Internet Routing and
Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.
[RFC2501] Corson, M. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.
[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
February 2000.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
Wood, "Advice for Internet Subnetwork Designers", BCP 89,
RFC 3819, July 2004.
[RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
Configuration of IPv4 Link-Local Addresses", RFC 3927,
May 2005.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4759] Stastny, R., Shockey, R., and L. Conroy, "The ENUM Dip
Indicator Parameter for the "tel" URI", RFC 4759,
December 2006.
[RFC4852] Bound, J., Pouffary, Y., Klynsma, S., Chown, T., and D.
Green, "IPv6 Enterprise Network Analysis - IP Layer 3
Focus", RFC 4852, April 2007.
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[RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
June 2007.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
Appendix A. Duplicate Address Detection (DAD) Considerations
A-priori uniqueness determination (also known as "pre-service DAD")
for an ELA assigned on an enterprise-interior interface (such as
specified in [RFC4862]) would require either flooding the entire
enterprise or somehow discovering a link in the enterprise on which a
node that configures a duplicate address is attached and performing a
localized DAD exchange on that link. But, the control message
overhead for such an enterprise-wide DAD would be substantial and
prone to false-negatives due to packet loss and intermittent
connectivity. An alternative to pre-service DAD is to autoconfigure
pseudo-random ELAs on enterprise-interior interfaces and employ a
passive in-service DAD (e.g., one that monitors routing protocol
messages for duplicate assignments).
Pseudo-random IPv6 ELAs can be generated with mechanisms such as
CGAs, IPv6 privacy addresses, etc. with very small probability of
collision. Pseudo-random IPv4 ELAs can be generated through random
assignment from a suitably large IPv4 prefix space.
Consistent operational practices can assure uniqueness for EBG-
aggregated addresses/prefixes, while statistical properties for
pseudo-random address self-generation can assure uniqueness for the
ELAs assigned on an EIR's enterprise-interior interfaces. Still, an
ELA delegation authority should be used when available, while a
passive in-service DAD mechanism should be used to detect ELA
duplications when there is no ELA delegation authority.
Appendix B. Change Log
(Note to RFC editor - this section to be removed before publication
as an RFC.)
Changes from -23 to 24:
o Clarifications on router discovery.
Changes from -22 to 23:
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o Clarifications on prefix mapping.
Changes from -21 to 22:
o Using SEAL to secure VET
Changes from -20 to 21:
o Enterprise partitioning.
o Mapping and name service management.
Changes from -18 to 20:
o Added support for simple hosts.
o Added EBG name service maintenace procedures
o Added router and prefix maintenace procedures
Changes from -17 to 18:
o adjusted section headings to group autoconf operations under EIR/
EBR/EBG.
o clarified M/O bits
o clarified EBG roles
Changes from -15 to 17:
o title change to "Virtual Enterprise Traversal (VET)".
o changed document focus from MANET-centric to the much-broader
Enterprise-centric, where "Enterprise" is understood to also cover
a wide range of MANET types.
Changes from -14 to 15:
o title change to "Virtual Enterprise Traversal (VET) for MANETs".
o Address review comments
Changes from -12 to 14:
o title change to "The MANET Virtual Ethernet Abstraction".
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o Minor section rearrangement.
o Clartifications on portable and self-configured prefixes.
o Clarifications on DHCPv6 prefix delegation procedures.
Changes from -11 to 12:
o title change to "MANET Autoconfiguration using Virtual Ethernet".
o DHCP prefix delegation for both IPv4 and IPv6 as primary address
delegation mechanism.
o IPv6 SLAAC for address autoconfiguration on the VET interface.
o fixed editorials based on comments received.
Changes from -10 to 11:
o removed the transparent/opaque VET portal abstractions.
o removed routing header as an option for MANET exit router
selection.
o included IPv6 SLAAC as an endorsed address configuration mechanism
for the VET interface.
Changes from -08 to -09:
o Introduced the term "VET".
o Changed address delegation language to speak of "MNBR-aggregated"
instead of global/local.
o Updated figures 1-3.
o Explained why a MANET interface is "neutral".
o Removed DHCPv4 "MLA Address option". Now, MNBRs can only be
DHCPv4 servers; not relays.
Changes from -07 to -08:
o changed terms "unenhanced" and "enhanced" to "transparent" and
"opaque".
o revised MANET Router diagram.
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o introduced RFC3753 terminology for Mobile Router; ingress/egress
interface.
o changed abbreviations to "MNR" and "MNBR".
o added text on ULAs and ULA-Cs to "Self-Generated Addresses".
o rearranged Section 3.1.
o various minor text cleanups
Changes from -06 to -07:
o added MANET Router diagram.
o added new references
o various minor text cleanups
Changed from -05 to -06:
o Changed terms "raw" and "cooked" to "unenhanced" and "enhanced".
o minor changes to preserve generality
Changed from -04 to -05:
o introduced conceptual "virtual ethernet" model.
o support "raw" and "cooked" modes as equivalent access methods on
the virutal ethernet.
Changed from -03 to -04:
o introduced conceptual "imaginary shared link" as a representation
for a MANET.
o discussion of autonomous system and site abstractions for MANETs
o discussion of autoconfiguration of CGAs
o new appendix on IPv6 StateLess Address AutoConfiguration
Changes from -02 to -03:
o updated terminology based on RFC2461 "asymmetric reachability"
link type; IETF67 MANET Autoconf wg discussions.
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Internet-Draft VET December 2008
o added new appendix on IPv6 Neighbor Discovery and Duplicate
Address Detection
o relaxed DHCP server deployment considerations allow DHCP servers
within the MANET itself
Changes from -01 to -02:
o minor updates for consistency with recent developments
Changes from -00 to -01:
o new text on DHCPv6 prefix delegation and multilink subnet
considerations.
o various editorial changes
Author's Address
Fred L. Templin (editor)
Boeing Phantom Works
P.O. Box 3707 MC 7L-49
Seattle, WA 98124
USA
Email: fltemplin@acm.org
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