MEXT Working Group R. Wakikawa
Internet-Draft R. Kuntz
Intended status: Experimental Toyota ITC
Expires: March 5, 2012 Z. Zhu
L. Zhang
UCLA
September 2, 2011
Global HA to HA Protocol Specification
draft-wakikawa-mext-global-haha-spec-02
Abstract
This document presents a revised version of the global HAHA protocol
specification. Global HAHA allows the deployment of Home Agents over
the Internet for reliability, scalability and performance purposes.
This version clarifies several issues that were vague in the original
specification. Global HAHA makes use of the signaling defined by the
Home Agent Reliability protocol (HARP) although it is not designed to
operate in conjunction with HARP.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 5, 2012.
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Initial Binding Registration . . . . . . . . . . . . . . . 9
3.2. Primary Home Agent Switch . . . . . . . . . . . . . . . . 9
3.3. Routing Packets . . . . . . . . . . . . . . . . . . . . . 10
3.4. Differences between global HAHA and HARP . . . . . . . . . 11
4. Home Agent Configurations . . . . . . . . . . . . . . . . . . 12
4.1. Home Agent and Subnet Distributions . . . . . . . . . . . 12
4.2. Anycast Routing Consideration . . . . . . . . . . . . . . 13
5. Global HAHA Protocol . . . . . . . . . . . . . . . . . . . . . 14
5.1. Home Agents Bootstrap . . . . . . . . . . . . . . . . . . 14
5.2. Management of global Home Agent set . . . . . . . . . . . 14
5.2.1. Home Agent List for the global HAHA . . . . . . . . . 15
5.2.2. Modified HARP Message . . . . . . . . . . . . . . . . 15
5.2.3. Sending Home Agent Hello Messages . . . . . . . . . . 16
5.2.4. Receiving Hello Message . . . . . . . . . . . . . . . 16
5.3. Primary Home Agent Receiving Binding Update . . . . . . . 17
5.4. Global Binding Management . . . . . . . . . . . . . . . . 18
5.4.1. Global Binding . . . . . . . . . . . . . . . . . . . . 18
5.4.2. Modified State Synchronization Message and
Mobility Option . . . . . . . . . . . . . . . . . . . 19
5.4.3. Global Binding Registration . . . . . . . . . . . . . 19
5.5. Primary Home Agent Switch . . . . . . . . . . . . . . . . 21
5.6. Packet Interception and Delivery . . . . . . . . . . . . . 22
5.7. Home Agents Discovery . . . . . . . . . . . . . . . . . . 23
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1. Normative References . . . . . . . . . . . . . . . . . . . 26
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9.2. Informative References . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28
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1. Introduction
The global HAHA protocol aims at leveraging the global deployment of
Home Agents over the Internet, by proposing reliability, scalability
and better performances to Mobile IPv6 [RFC6275] deployments.
The original global HAHA protocol [I-D.thubert-mext-global-haha] has
been discussed for several years in MIP6, NEMO and now MEXT working
groups. Several documents [I-D.thubert-mext-global-haha]
[I-D.wakikawa-mip6-nemo-haha-spec]
[I-D.wakikawa-mext-haha-interop2008] have been published and
presented in past IETF meetings, and received valuable feedback.
This document presents a revised version of the global HAHA protocol
specification. This version clarified several issues that were vague
in the original specification [I-D.thubert-mext-global-haha].
Global HAHA makes use of the signaling defined by the Home Agent
Reliability protocol (HARP) [I-D.ietf-mip6-hareliability] which is
being standardized in the MEXT working group. On one hand, HARP
provides a redundancy mechanism for the Home Agents located on the
same layer-2 link (or in different layer-2 links provided that proper
routing updates are performed between links upon failure). On the
other hand, global HAHA builds on anycast routing to not only provide
redundancy but also achieve a better distributed mobility management
for Mobile IPv6. More specifically, global HAHA provides the
following advantages:
o It eliminates the single point of failure and bottleneck in Mobile
IPv6 and NEMO protocols. By distributing multiple Home Agents
over wide areas, scalability and robustness of the mobility
infrastructure can be improved.
o It provides very flexible deployment schemes. When home agents
are placed at Internet Exchange Points, they can improve the
performances of mobility over long distances (such as depicted in
aeronautics scenarios [RFC5522]) by minimizing triangle routing as
compared to the path utilizing a single home agent (so called dog-
leg routing). Alternatively, when home agents are placed closer
to the edge of the network, a more flat design can be achieved.
Offloading near the edge of the network becomes possible, to the
benefit of the core network load [I-D.kuntz-dmm-summary].
o It makes use of existing protocols (HARP signaling
[I-D.ietf-mip6-hareliability], Home Agent Switch messages
[RFC5142]) while confining the required changed to the home agent
only.
Global HAHA also provides reliability in case of a home agent
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failure. Whether it would be useful to be able to combine HARP with
global HAHA for local reliability of a home agent is open for future
discussion. Such combination can bring better performances in cases
that may be unlikely to happen often, at the cost of an increased
complexity. Furthermore, whether Global HAHA should be independent
from HARP and define its own signaling protocol is also open for
further discussion.
The global HAHA concept has been evaluated through prototype
implementations in several places [PAPER-CONEXT] and the results show
that the design is simple and effective in reducing triangle routing.
Several industry sectors such as aviation [RFC5522] and automobile
[I-D.ietf-mext-nemo-ro-automotive-req] have shown their interests in
using global HAHA to meet the need for their mobility managements.
As every coin has two sides, the global HAHA protocol is not an
exception. It achieves the above goals through utilizing anycast
routing, which has raised a concern on routing scalability, and it
introduces additional overheads due to the need to synchronize the
mobility state among distributed home agents. By presenting a
complete design together with the design justifications, we hope that
this document will help move the discussion towards a converged
understanding on the pros and cons of the global HAHA protocol.
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2. Terminology
This document uses terms defined in [RFC3753], [RFC6275], [RFC3963]
and and [I-D.ietf-mip6-hareliability]. A few new terms are also
introduced in this document:
Home subnet prefix
It is assigned to a home subnet, and the home agent unicast
address (defined below) of a mobile node is assigned out of this
prefix block. In this global HAHA specification, the home subnet
prefix is assumed to be a provider independent prefix.
Home agent unicast address
A unicast IP address created from the home subnet prefix and
assigned to a home agent. This is the address used by Mobile
nodes when sending Binding Updates to their Home Agent.
Home agent locator address
A unicast IP address assigned to a home agent by the ISP who
provides the Internet connectivity for the home agent. This
address is used to exchange mobility messages between globally
distributed home agents.
Home agent anycast address
The anycast address defined as per [RFC2526] and used by mobile
nodes for Dynamic Home Agent Address Discovery purposes.
Global home agent set
The set of home agents serving the same home subnet prefix. The
home agents are located in topologically and/or geographically
different locations. A global home agent set is identified with a
8-bit group ID.
HAHA link
All the home agents in the same global home agent set share the
same home subnet prefix although they may be located in different
parts on Internet. In order for each of them to reach all the
others directly as required by IP subnet definition, logical
connectivity links are created between each pair of home agents.
These logical links, called HAHA links, can be realized using IP
tunnel technologies such as IP tunnel, IPsec tunnel, L2TP, PPTP,
and so on. Data packets and Binding Updates that need to be
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forwarded between home agents are sent over these HAHA links.
Primary Home Agent
The home agent which a mobile node is currently registered with.
Among all the available home agents in the same set, this primary
home agent should be topologically closest to the mobile node. At
any given time each mobile node has one primary home agent.
Global Binding
When a mobile node registers with a primary home agent, the home
agent notifies this binding, called the global binding, to all the
other home agents in the same global home agent set. The receiver
of this global binging information learns the mapping between the
mobile node and its current primary home agent, and creates a
route entry for the mobile node with the next hop pointing to the
primary home agent locator address. This route entry has a
lifetime which can be different from the lifetime carried in the
original binding message. When the lifetime expires, the route is
deleted.
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3. Overview
Global HAHA relies on IP anycast routing between geographically and
topologically different home agent locations. The home subnet prefix
is announced by all the home agents in a deployed global HAHA system,
so that packets from and to mobile nodes are always routed towards
the closest home agents in a way that is completely transparent to
the mobile and correspondent nodes.
Global HAHA does not require any modification to mobile nodes and
mobile routers (i.e. end mobile entity). Supporting Mobile IPv6
[RFC6275] and Home Agent Switch message [RFC5142] is sufficient to
run mobile nodes with globally distributed home agents.
Figure 1 shows the protocol sequence of the global HAHA. As an
assumption, each home agent in the same global home agent set MUST
establish HAHA links for interconnecting other home agents. The
detail of HAHA link establishment is described in Section 5.1.
MN HA1 HA2 CN
| | | |
|----> (Primary) | | 1. Binding Update
|<--------| | | 2. Binding Acknowledgment
| |-------->| | 3. State Synchronization
|<========|<========|<--------| 4. From CN to MN
|========>|------------------>| 5. From MN to CN
| | | |
: : : : MN MOVEMENT
| | | |
|------------------+| | 6. Binding Update
| |<=======+| |
|<--------| | | 7. Binding Acknowledgment
|<--------| | | 8. Home Agent Switch
|--------------> (Primary) | 9. Binding Re-registration
| |<--------| | 10. State Synchronization
|<==================|<--------| 11. From CN to MN
|==================>|-------->| 12. From MN to CN
| | | |
==== for tunneling
---- for direct packets
Figure 1: Overview of global HAHA
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3.1. Initial Binding Registration
Global HAHA home agents can be reached by the mobile node through
both the home agent anycast address (e.g. obtained with Dynamic Home
Agent Address Discovery [RFC6275]) and the Home agent unicast address
(e.g. obtained from the DNS) created from the home agent home subnet
prefix (see Section 5.7). Note that the home agent locator address
is not known by the mobile nodes and is only used between global home
agents to exchange mobility messages among them.
When the mobile node attempts the binding registration to a home
agent using the HA anycast address (operation 1 in Figure 1), the
binding update is routed to the topologically closest home agent of
the mobile node via IP anycast routing. The closest home agent which
the mobile node registers its binding with is called a primary home
agent for the mobile node. This specification assumes that the route
of home subnet prefix is advertised from each of different locations
where an HAHA home agent resides.
After sending a binding Acknowledgment to the mobile node (operation
2 in Figure 1) and registering a binding cache for the mobile node,
the primary home agent (HA1) sends State Synchronization messages to
all the other home agent (i.e. HA2) in the same global home agent
set (operation 3 in Figure 1). Then, HA2 creates a global binding
for the mobile node and creates the mobile node's route entry with
the next hop set to the locator address of the primary home agent
(HA1). The global binding needs to be updated when a mobile node
changes its primary home agent. It must also be refreshed before its
lifetime expiration.
When HA2 receives packets from a correspondent node destined to the
mobile node, it forwards them to the primary home agent (HA1) over
the HAHA link according to the global binding (operation 4 in
Figure 1). When a mobile node sends data to the correspondent node,
the traffic is tunneled to the primary home agent, which then routes
directly to the destination (operation 5 in Figure 1).
If the mobile node obtained the home agent unicast address through
the DNS, and that address does not correspond to the topologically
closest home agent, a home agent switch will be performed as
described in the next section.
3.2. Primary Home Agent Switch
In this example, from the routing perspective, the closest home agent
of the mobile node is now changed from HA1 to HA2 after a mobile
node's movement. Thus, the primary home agent of the mobile node
needs to be updated from HA1 to HA2. This case can also happen if
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the home agent unicast address obtained from the DNS (during the
bootstrapping phase of the mobile node) is set to HA1 whereas the
mobile node is initially closer to HA2.
The Primary Home Agent switch operation consists of two binding
updates exchange. The first binding update is used to detect the
closer home agent by the current primary home agent. The second
binding update is to let the mobile node change its primary home
agent.
When a mobile node changes its point of attachment, it simply sends
the first Binding Update to its current primary home agent (i.e. HA1
in Figure 1) in order to renew its binding as per [RFC6275].
However, since HA2 also advertises the same home subnet prefix, the
Binding Update is first routed to the HA2 by IP anycast routing. HA2
knows that HA1 belongs to the same global Home Agent set, and thus
forwards the Binding Update to its destination (HA1) over the HAHA
link (operation 6 in Figure 1).
Due to fact that the binding update is forwarded from one of other
home agents in the same global home agent set, the HA1 now detects
that the primary home agent is changed to the HA2. The HA1 first
processes the Binding Update and returns a Binding Acknowledgment to
the mobile node (operation 7 in Figure 1). In parallel, it triggers
a Home Agent Switch message [RFC5142] to the mobile node (operation 8
in Figure 1). In the Home Agent switch message, the home agent
unicast address of HA2 is stored in the Home Agent Address field so
that the mobile node can associate with the closest home agent.
When the mobile node receives the Home Agent Switch message from the
HA1, it switches its home agent to the HA2 according to [RFC5142].
The mobile node sends another Binding Update to the HA2 (operation 9
in Figure 1). After receiving the Binding Update, the HA2 creates
the binding cache and sends a State Synchronization message to the
other Home Agents (i.e. HA1) in the global home agent set (operation
10 in Figure 1). The HA1 removes the binding cache entry of the
mobile node and creates a global binding as well as the route for the
mobile node with the next hop set to the locator address of HA2 over
the HAHA link.
3.3. Routing Packets
The packets originated by the mobile node are always routed through
the primary home agent as shown in operations 5 and 12 in Figure 1.
They are tunneled to the primary home agent and, then, routed
directly to the CN.
On the other hand, the packets originated by the correspondent node
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are routed to the closest home agent by IP anycast routing as shown
in operations 4 and 11 in Figure 1. If the home agent is not the
primary home agent of the mobile node (destination), the home agent
looks up the global binding and routes them to the primary home agent
of the mobile node over the HAHA link. Then, the primary home agent
routes the packets to the mobile node over the Mobile IPv6's bi-
directional tunnel.
In some scenario, the path between a mobile node and a correspondent
node becomes asymmetric. In the global HAHA, the primary home agent
does not have any specific information of the correspondent nodes and
does not forward the packets to the closest home agent of the
correspondent node.
3.4. Differences between global HAHA and HARP
The global HAHA protocol makes use of the signaling defined by the
Home Agent Reliability protocol (HARP) [I-D.ietf-mip6-hareliability]
which is being standardized in the MEXT working group. However,
global HAHA is not designed to be operated in conjunction with HARP.
HARP extends Mobile IPv6 [RFC6275] to provide reliability to home
agents. Its concept is similar to the router's redundancy protocols
such as VRRP and HSRP. When one home agent fails, another standby
home agent located in the same home link or in a different network
can immediately take over the function of the failed one, so that
ongoing sessions of mobile nodes will not be interrupted by any
single home agent failures.
Global HAHA can also achieve reliability by relying on IP anycast
routing. The home subnet prefix being announced by all the home
agents, packets from and to mobile nodes can be forwarded to
remaining functional home agents in a transparent manner. In
addition, global HAHA can achieve better scalability and provide
optimized paths between a mobile node and its correspondents, by
always associating the nearest home agent to the mobile node.
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4. Home Agent Configurations
4.1. Home Agent and Subnet Distributions
Figure 2 shows the subnet and home agent distribution in a global
HAHA system. Home agents are connected to a number of subnets
located in various places on Internet, they are all assigned the same
Provider-Independent (PI) prefix as their home subnet prefix. Each
home subnet is connected to the global Internet through an ISP who
also assigns a prefix out of its own address block to the home
subnet. We call this ISP assigned prefix "Locator Prefix" (LP).
Each home agent has two unicast IP addresses: one from its PI home
subnet prefix (the "home agent unicast address") and another from its
provider (the "home agent locator address"). Each ISP that hosts a
HAHA subnet also agrees to announce the HAHA's PI Home subnet prefix
to the global Internet, so that packets destined to any IP address
that belongs to the home subnet prefix are delivered to the
topologically closest home agent.
Home Link1 (2001:db8:0:1::/64)
HA1
|
--+--
| /|\ LP-1 Prefix
+--------+ |
| ISP1 |
+--------+ LP-2 Prefix
| -->
+--------+ +--------+ |
|Backbone|--| ISP2 |----+- HA2 Home Link2
+--------+ +--------+ | (2001:db8:0:1::/64)
|
+--------+
| ISP3 |
+--------+ | LP-3 Prefix
| \|/
--+--
|
HA3
Home Link3 (2001:db8:0:1::/64)
HA unicast address (PI) HA locator address (LP)
- HA1 2001:db8:0:1::1 LP-1Prefix::1
- HA2 2001:db8:0:1::2 LP-2Prefix::2
- HA3 2001:db8:0:1::3 LP-3Prefix::3
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Figure 2: Home Subnets and Agents Distribution
4.2. Anycast Routing Consideration
IP anycast routing has been widely used in recent years. As
documented in [RFC4786], anycast has become increasingly popular for
adding redundancy to DNS servers to complement the redundancy that
the DNS architecture itself already provides. Several root DNS
server operators have distributed their servers widely around the
Internet, and DNS queries are directed to the nearest functioning
servers. Another popular anycast usage is by web service providers,
where two or more web farms share the same IP prefix, so that when
all the sites are up, HTTP requests are forwarded to the web servers
closest to the browsers; when a site is down, requests are
automatically routed to next nearest web farm. Anycast routing
provides a simple and effective means to provide robust services.
A concept related to anycast is MOAS (Multi-Origin AS) prefixes, they
are prefixes advertised by more than one origin AS. A MOAS prefix
represents an anycast prefix, although the inverse is not necessarily
true, i.e. an anycast prefix may not be a MOAS prefix if the prefix
is announced to the routing system by one origin AS out of the AS's
multiple locations. Our measurement using BGP data collected by
RouteViews and RIPE observed about 2000 or so MOAS prefixes in
today's global routing system, which is a very small percentage of
the current routing table entries of about 300K entries.
One basic cost from providing anycast services is an additional entry
in the global routing table for each anycast prefix. When the number
of anycast applications is small, the impact on the global routing
system scalability is small. The use of anycast for important
infrastructure services, such as DNS root servers, is well justified.
Using anycast to bootstrap other important services may also be
justified, if the services are globally scoped are commonly used, and
the number of anycast prefixes needed is small. However anycast is
clearly not for everyone or for all applications usage. It is a
worthwhile investigation to consider where best to draw the line.
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5. Global HAHA Protocol
5.1. Home Agents Bootstrap
For the global HAHA protocol, each home agent SHOULD be configured
with the following information:
o An own home subnet prefix (Provider Independent prefix, PI)
o An own home agent unicast address (created from the PI)
o An own home agent locator address (created from the Locator
Prefix, LP)
o A home agent anycast address for Dynamic Home Agent Address
discovery mechanism (created as per [RFC2526])
o A Group ID of own global home agent set
o Home Agent locator addresses of all the other home agents in the
same global home agent set.
A home agent first establishes HAHA links with all the other home
agents. How to establish a HAHA link is out of scope in this
document. For instance, IP tunnel is established between two home
agent's locator addresses. This HAHA link is used to exchange data
packets destined to the mobile node and binding updates coming from
the mobile node. Although all the Binding Updates are already
securely exchanged, it is recommended to secure every packets
tunneled over this HAHA link. Note that Home Agent HELLO message and
State Synchronization message do not need to be tunneled over the
HAHA link as they can be sent directly using the Home Agent locator
addresses as source and destination addresses.
As soon as HAHA links are fully ready, the home agent now provides
its home agent service to a mobile node. Without HAHA links, a home
agent SHOULD NOT configure with its home subnet prefix and act as a
home agent of the home subnet prefix. The home agent now starts
sending its Home Agent HELLO message as described in Section 5.2 and
soliciting global bindings of all the other home agents as discussed
in Section 5.4.3.
5.2. Management of global Home Agent set
A home agent exchanges its availability with other home agents of the
same global home agent set. The status exchange is done with a Home
Agent HELLO message defined in the Home Agent Reliability protocol
[I-D.ietf-mip6-hareliability].
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5.2.1. Home Agent List for the global HAHA
[RFC6275] and [I-D.ietf-mip6-hareliability] specify and extend the
data structure named the Home Agent List. This list is used to
manage home agent information at a same home link. The following two
fields introduced in [RFC6275] are not used in this specification:
o The link-local IP address of a home agent
o The preference for this home agent
5.2.2. Modified HARP Message
This specification defines a new flag for the HARP HA-HELLO message
(Type 4):
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 | Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |A|R|V|M|G| Rsvd| Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Home Agent Preference | Home Agent Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hello Interval | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. Mobility Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: HARP Message
Home Agent Preference
In this specification, a same preference value is used among home
agents in a global home agent set. A home agent is selected by a
mobile node according to routing topology (i.e. anycast routing),
but not by these preference values. This value SHOULD be set to
0. The receiver SHOULD ignore this value.
Group Identifier
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This value is used to identify a particular global home agent set.
Global (G) flag
Global HA flag. If this flag is set, the home agent sending this
HA-HELLO message is operated with this specification.
5.2.3. Sending Home Agent Hello Messages
Each home agent periodically sends HA-HELLO to the other home agents
in the same global home agent set. Each home agent MUST also
generate HA-HELLO in the following cases:
o when a home agent receives a HA-HELLO with the G (Global HA) and R
(Request) flag set
o When a new home agent boots up, it SHOULD solicit HA-HELLO
messages by sending a HA-HELLO with the G and R-flag set in
parallel with sending its own HA-HELLO message.
When a home agent sends HA-HELLO, the following rule MUST be applied
in addition to the Section 4.3.2.1 of [I-D.ietf-mip6-hareliability].
o It MUST set G flag in HA-HELLO.
o It MUST specify its global home agent set's ID to the Group ID
field in HA-HELLO.
o The source and destination IPv6 addresses of the IPv6 header of
the HA-HELLO MUST be the source and destination home agent locator
addresses. They MUST belong to the same global home agent set.
o It MUST protect HA-HELLO by IPsec ESP.
5.2.4. Receiving Hello Message
When a home agent receives HA-HELLO, it follows the verification
described in Section 4.3.2.2 of [I-D.ietf-mip6-hareliability]. In
addition to this, it MUST process HA-HELLO which G flag is set as
follows:
o If the HA-HELLO is not protected by IPsec ESP, it MUST be
discarded.
o If the source IPv6 address of HA-HELLO does not belong to one of
the home agents in the redundant home agent set, the HA-HELLO MUST
be ignored.
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o If the Group ID field of the received HA-HELLO and the receiver's
Group ID are different, HA-HELLO MUST be discarded. HA-HELLO MUST
NOT be sent to home agents whose Group ID is different from the
sender.
o HA-HELLO satisfying all of above tests MUST be processed by
receiver. The receiver copies home agent information in HA-HELLO
to the corresponding home agent list entry. The home agent
locator address of the sender is retrieved from the source address
field of the IPv6 header of the HA-HELLO.
5.3. Primary Home Agent Receiving Binding Update
The binding update sent by a mobile node is routed to the one of home
agents in the global home agent set according to the anycast routing.
If the receiver does not have any binding cache entry nor global
binding for this mobile node, it processes the binding update
according to [RFC6275] and stores a binding cache entry for the
mobile node. After successful binding registration, the home agent
becomes a primary home agent for the mobile node. The primary home
agent has the following functional requirements:
o Delivering IP packets destined to the mobile node over the bi-
directional tunnel
o Updating the binding according to the mobile node's binding
refreshment
o Notifying the mobile node binding to the other home agents in the
same global home agent set
o Sending a Home Agent Switch message if another home agent is more
preferable to be the primary home agent. Usually, this is
trigerred by the reception of a valid Binding Update via another
home agent of the global home agent set
o Providing state synchronization information to other home agents
of the global home agent set when a binding is created, updated,
removed or upon request.
The binding registration and management are the same as specified in
[RFC6275]. The global HAHA requires to register global bindings of
the mobile node by sending the state synchronization message to all
the other home agents as described in the next section.
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5.4. Global Binding Management
5.4.1. Global Binding
A global binding has the following information. Any mobile node's
specific information can be potentially stored in the global binding.
The aim of this global binding is to forward the data packets of a
mobile node received at non-primary home agent to the primary home
agent of the mobile node. It is not used to deliver a packet
directly to a mobile node from the non-primary home agents.
Therefore, the mobile node's care-of address is not necessary in the
global binding, more than likely the primary home agent of the mobile
node is important in the global binding.
o The primary home agent locator address
o The mobile node's home address
o The mobile router's mobile network prefix(es)
o The binding sequence number of a binding update
o The flags of a binding update
o The lifetime of the global binding
o The mobile node's care-of address (optional)
The modified State Synchronization message
[I-D.ietf-mip6-hareliability] described in the next section is used
to exchange the global bindings among the home agents.
When a global binding is created, the home agent MAY use proxy
Neighbor Discovery or IP routing to intercept the packets addressed
to the mobile node's home address.
When a global binding is created, the home agent MUST create a mobile
node's route entry which next hop is set to the locator address of
the primary home agent. If a mobile node is a mobile router
[RFC3963], the following mobile node's routes are created: one for
the home address and one per mobile network prefix. If the mobile
router's home address is derived from its mobile network prefix
[RFC3963] (i.e. the operation of aggregated home network [RFC4887]),
only a single route for the mobile network prefix is sufficient.
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5.4.2. Modified State Synchronization Message and Mobility Option
Figure 4 shows the modified version of the state synchronization (SS)
message defined in [I-D.ietf-mip6-hareliability]. A new G flag is
introduced to explicitly indicate the global binding registration.
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 |A|G| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. .
. Mobility Options .
. .
. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: State Synchronization Message
Global (G) flag
When State Synchronization messages are exchanged for global
binding registration, the Global flag MUST be set.
Mobility Options
The Binding Cache Information Option as defined in
[I-D.ietf-mip6-hareliability] is mandatory for the State
Synchronization Request (SS-REQ) message (Type 0) as well as State
Synchronization Reply (SS-REP) message (Type 1).
Others options (e.g. AAA Information option, Vendor Specific
Mobility option, as well as the others referenced in
[I-D.ietf-mip6-hareliability]) can be used too.
The SS Status Option as defined in [I-D.ietf-mip6-hareliability]
MUST be used in the State Synchronization Reply-Ack (SS-ACK)
message (Type 2).
5.4.3. Global Binding Registration
If a primary home agent sends a SS-REP message for every binding
registration from a mobile node, it causes certain overhead to
exchange messages. Unless the binding information is changed (except
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for sequence number and lifetime), the state synchronization reply
message is not necessarily sent per mobile nodes' binding
refreshment. A SS-REP message MUST be sent by a primary home agent
to register a global binding at the following timing:
o When a primary home agent registers a binding for a mobile node
for the first time. The primary home agent MUST register a global
binding to the global home agent set.
o When a global binding is expired. The primary home agent MUST
refresh the global binding.
When a primary home agent receives a binding update from a mobile
node and registers a binding for it, it sends a State Synchronization
Reply message. SS-REP is sent to all the other home agents in the
global home agent set with the following rules:
o The A (Ack) and G (Global) flags MUST be set in SS-REP.
o At least, one Binding Cache Information Option MUST be stored in
the mobility option field. Multiple options can be stored in a
SS-REP.
o Other optional mobility options listed in Section 5.4.2 MAY be
stored in the mobility option field.
o IPsec ESP MUST be applied.
o The source and destination addresses of the SS-REP MUST be the
source and destination home agent locator addresses.
o The source and destination addresses MUST belong to the same
global home agent set.
When a home agent receives the SS-REP, the following rules must be
applied to the received SS-REP:
o If the SS-REP is not protected by IPsec ESP, it MUST be discarded.
o If no options are carried in SS-REP, the receiver MUST ignore the
SS-REP and MUST send SS-ACK with the Status Synchronization Status
option which status value is set to the newly defined value [131:
No Mobility Option].
o If the sender of SS-REP is not in the same global home agent set,
the receiver MUST reject the SS-REP and MUST send SS-ACK with the
Status Synchronization Status option which status value is set to
[130: Not in same global home agent set].
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o If the G flag is not set in RR-REP, the receiver MUST ignore the
SS-REP and MUST send SS-ACK with the Status Synchronization Status
option which status value is set to [129: Malformed SS-REP].
o If no errors are found in SS-REP, the receiver MUST register or
update the global binding per Binding Cache Information Option.
If the supplemental mobility options are specified for a mobile
node, the information MUST be stored in the global binding.
o After the successful global binding registration, it MUST create a
mobile node's route entry which next hop is set to the primary
home agent locator address (i.e. the sender of SS-REP). If a
mobile node is a mobile router [RFC3963], the following mobile
node's routes are created: one for the home address and one per
mobile network prefix. If the mobile router's home address is
derived from its mobile network prefix [RFC3963] (i.e. the
operation of aggregated home network [RFC4887], only a single
route for the mobile network prefix is sufficient.
o The receiver of SS-REP then sends SS-ACK with state
synchronization status mobility options for all the mobile nodes
registering its global binding.
When a home agent needs to solicit SS-REP, it can send SS-REQ to a
home agent. The rules to construct SS-REQ is described in Section
4.4.3 of [I-D.ietf-mip6-hareliability]. In addition, the following
rules MUST be applied:
o IPsec ESP MUST be applied.
o The source and destination addresses of the SS-REQ MUST be the
source and destination home agent locator addresses.
o The source and destination addresses MUST belong to the same
global home agent set.
5.5. Primary Home Agent Switch
Primary Home Agent switch operation consists of two binding update
exchanges. The first binding update is basically used by a primary
home agent to detect the better home agent in the same global home
agent set and to trigger sending a home agent switch message to
mobile nodes. The second one is to complete primary home agent
switch by registering the binding to the new primary home agent.
When a mobile node moves, it sends a binding update to its primary
home agent currently registering the binding. If the binding update
is directly routed to the destination (i.e. home agent), there is no
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need to start the primary home agent switch. On the other hand, if
the binding update is first routed to one of non-primary home agents,
the receiver of the binding update SHOULD become the primary home
agent of the mobile node from the routing perspective. The receiver
does not operate any inspection of the binding update and simply
forwards it to the destination address of the binding update over the
HAHA link.
Once the primary home agent receives the binding update forwarded by
one of home agents in the same global home agent set, it processes
the binding update as described in Section 5.3. In addition, it
starts sending a home agent switch message [RFC5142] for the primary
home agent switch operation. How to send the home agent switch
message is described in [RFC5142] and Section 4.5 of
[I-D.ietf-mip6-hareliability].
The mobile node receiving the home agent switch message simply
updates its home agent address and re-registers its binding to the
new primary home agent. The new primary home agent sends SS-REP to
all the other home agents to update its global binding. After
receiving SS-REP, the previous primary home agent SHOULD delete its
original binding and create a global binding for the mobile node.
According to [RFC5142], upon receipt of a Home Agent Switch message,
the mobile node must delete its home binding by sending a Binding
Update deregistration message. However, the mobile node SHOULD NOT
send this de-registration in this specification, since the previous
active home agent knows the primary home agent switch by receiving
the SS-REP. Although this represents a slight modification of the
mobile node side, this helps achieving minimum latency of the primary
home agent switch by eliminating the binding de-registration process.
5.6. Packet Interception and Delivery
When a home agent receives a packet destined to a mobile node, it
first check the binding cache. If it finds an original binding, it
tunnels the packet to the mobile node over the bi-directional tunnel.
Otherwise, it checks the global binding of the mobile node. If it
finds the global binding, it then routes the packet to the primary
home agent recorded in the global binding over the HAHA link. The
packet is delivered to the primary home agent by IP encapsulation.
In the outer IP header, the home agent source and destination locator
addresses should be used. If neither a binding nor a global binding
is found, the packet MUST be simply discarded. The home agent SHOULD
return an ICMP Destination Unreachable (Code 3) message to the
packet's source address (unless this source address is a multicast
address).
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5.7. Home Agents Discovery
When a mobile node boots up and needs to discover a home agent, it
can either use Dynamic Home Agent Address Discovery (DHAAD) or
perform a DNS lookup by home agent name or service name as specified
in [RFC5026].
In the DHAAD case, the mobile node simply sends a DHAAD request
message to the home agent anycast address. In that case, the DHAAD
request message is routed to the closest home agent via IP anycast
routing. The closest home agent SHOULD return its own unicast
address with the highest priority in the DHAAD reply message so that
the mobile node can use the closest home agent for its binding
registration.
In the DNS case, the lookup by home agent name or service name may
return either the home agent anycast address or a home agent unicast
address. In both cases, the binding update sent by the mobile node
will reach the closest home agent thanks to IP anycast routing.
However, in the second case, the binding update may be forwarded by
that home agent towards the owner of the home agent unicast address
used in the binding update. In that case, a primary home agent
switch may be initiated right after the registration of the mobile
node. In order to avoid this case, the DNS may be configured to
return only the home agent anycast address, or have the necessary
mechanisms to return the unicast address of the closest home agent
for the mobile node.
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6. IANA considerations
This document does not contain any actions for the IANA
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7. Security Considerations
TBA: Section 7 of [I-D.ietf-mip6-hareliability] gives useful
information.
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8. Acknowledgements
We would like to thank to Pascal Thubert and Vijay Devarapalli for
the original discussion of the global HAHA. We also thank to Arnaud
Ebalard for his review and valuable comments.
9. References
9.1. Normative References
[I-D.ietf-mip6-hareliability]
Wakikawa, R., "Home Agent Reliability Protocol (HARP)",
draft-ietf-mip6-hareliability-09 (work in progress),
May 2011.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
[RFC5142] Haley, B., Devarapalli, V., Deng, H., and J. Kempf,
"Mobility Header Home Agent Switch Message", RFC 5142,
January 2008.
[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.
9.2. Informative References
[I-D.ietf-mext-nemo-ro-automotive-req]
Baldessari, R., Ernst, T., Festag, A., and M. Lenardi,
"Automotive Industry Requirements for NEMO Route
Optimization", draft-ietf-mext-nemo-ro-automotive-req-02
(work in progress), January 2009.
[I-D.kuntz-dmm-summary]
Kuntz, R., Sudhakar, D., Wakikawa, R., and L. Zhang, "A
Summary of Distributed Mobility Management",
draft-kuntz-dmm-summary-01 (work in progress),
August 2011.
[I-D.thubert-mext-global-haha]
Thubert, P., Wakikawa, R., and V. Devarapalli, "Global HA
to HA protocol", draft-thubert-mext-global-haha-01 (work
in progress), July 2009.
[I-D.wakikawa-mext-haha-interop2008]
Wakikawa, R., Shima, K., and N. Shigechika, "The Global
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HAHA Operation at the Interop Tokyo 2008",
draft-wakikawa-mext-haha-interop2008-00 (work in
progress), July 2008.
[I-D.wakikawa-mip6-nemo-haha-spec]
Wakikawa, R., "Inter Home Agents Protocol Specification",
draft-wakikawa-mip6-nemo-haha-spec-01 (work in progress),
March 2006.
[PAPER-CONEXT]
Wakikawa, R., Valadon, G., and J. Murai, "Migrating Home
Agents towards Internet-Scale Mobility Deployments",
CoNEXT 2006 Conference on Future Networking Technologies,
December 2006.
[RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast
Addresses", RFC 2526, March 1999.
[RFC2991] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
Multicast Next-Hop Selection", RFC 2991, November 2000.
[RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, December 2006.
[RFC4885] Ernst, T. and H-Y. Lach, "Network Mobility Support
Terminology", RFC 4885, July 2007.
[RFC4887] Thubert, P., Wakikawa, R., and V. Devarapalli, "Network
Mobility Home Network Models", RFC 4887, July 2007.
[RFC4888] Ng, C., Thubert, P., Watari, M., and F. Zhao, "Network
Mobility Route Optimization Problem Statement", RFC 4888,
July 2007.
[RFC4889] Ng, C., Zhao, F., Watari, M., and P. Thubert, "Network
Mobility Route Optimization Solution Space Analysis",
RFC 4889, July 2007.
[RFC5026] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
Bootstrapping in Split Scenario", RFC 5026, October 2007.
[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.
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Authors' Addresses
Ryuji Wakikawa
Toyota InfoTechnology Center USA, Inc.
465 Bernardo Ave
Mountain View, California 94045
USA
Email: ryuji@us.toyota-itc.com
Romain Kuntz
Toyota InfoTechnology Center USA, Inc.
465 Bernardo Ave
Mountain View, California 94045
USA
Email: rkuntz@us.toyota-itc.com
Zhenkai Zhu
UCLA
420 Westwood Plaza
Los Angeles, California 90095
USA
Email: zhenkai@cs.ucla.edu
Lixia Zhang
UCLA
3713 Boelter Hall
Los Angeles, California 90095-1596
USA
Email: lixia@cs.ucla.edu
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