IETF INTERNET-DRAFT Thierry Ernst
WIDE Project and INRIA
Hong-Yon Lach
Motorola Labs
July 2002
Network Mobility Support Terminology
draft-ernst-monet-terminology-01.txt
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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The list of current Internet-Drafts can be accessed at
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Abstract
This document proposes a terminology for defining the problem faced
by network mobility. Network mobility is concerned with situations
where an entire network changes its point of attachment to the
Internet and thus its reachability in the topology. We shall refer to
such a network as a mobile network. Network mobility support is to
maintain session continuity between nodes in the mobile network and
nodes in the global Internet.
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Contents
Status of This Memo
Abstract
1. Introduction
2. Terminology
2.1. Architecture Components
2.2. Nested Mobility
2.3. Miscellaneous Terms
3. Characteristics / Observations
4. Changes since last version of the draft
Acknowledgments
References
Author's Addresses
1. Introduction
A mobile network is an entire network, moving as a unit, which
changes its point of attachment to the Internet and thus its
reachability in the topology. A mobile network may be composed by one
or more IP-subnets and is connected to the global Internet via one or
more Mobile Routers (MR). Nodes behind the MR primarily comprise
fixed nodes (nodes unable to change their point of attachment while
maintaining ongoing sessions), and additionally mobile nodes (nodes
able to change their point of attachment while maintaining ongoing
sessions). The internal configuration of the mobile network is
assumed to be relatively stable with respect to the MR.
If network mobility is not explicitly supported by some mechanisms
once a MR changes its point of attachment, existing sessions between
CNs and nodes behind the MR are broken, and connectivity to the
global Internet is lost. In addition, fixed nodes behind the MR may
experiment dog-leg routing, whereas multiple levels of mobility may
cause multiple dog-leg routing. Traditional work on mobility support
as conducted in the Mobile IP working group is to provide continuous
Internet connectivity to mobile hosts only (host mobility support)
and are unable to support network mobility. It is thus proposed to
create a NEMO working group that would specify solutions for network
mobility support (the proposed name for the working group was renamed
from MONET to NEMO).
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Cases of mobile networks include networks attached to people
(Personal Area Network or PAN, i.e. a network composed by all
Internet appliances carried by people, like a PDA, a mobile phone, a
digital camera, a laptop, etc.) and networks of sensors deployed in
aircrafts, boats, busses, cars, trains, etc. An airline company that
provides permanent on-board Internet access is an example of a mobile
network. This allows passengers to use their laptops (this scenario
is mentioned in [Tanenbaum96] under section 1.2.4 and section 5.5.8;
[Perkins98] under section 5.12; [Solomon98] under section 11.2; and
[RFC2002] section 4.5), PDA, or mobile phone to connect to remote
hosts, download music or video, browse the web. Passengers could
themselves carry a network with them (a PAN). At the same time, air
control traffic could be exchanged between the aircraft and air
traffic control stations (this scenario has already been investigated
by Eurocontrol, the European Organization for the safety of air
navigation, [Quinot98]). During a transatlantic flight, the aircraft
changes its point of attachment to the Internet and may be reachable
by distinct Internet Service Providers (ISPs). Over the oceans, the
aircraft gets connected to the Internet through a geostationary
satellite; over the ground, it's through a radio link. Handoffs do
typically not occur very often (a radio link may cover 400-500
kilometers). Another similar scenario mentioning ships and aircrafts
can be found in [RFC1726, section 5.15]. Similarly, a bus, the
metropolitan public transport, or the taxi company could allow
passengers to connect their PAN to the Internet via the embarked
network, therefore ensuring, while on-board, an alternative to the
metropolitan cellular network, in terms of price or available
bandwidth, access control, etc. Meanwhile, a number of Internet
appliances deployed in the mobile network are used to collect traffic
and navigation data from the Internet while sensors within the mobile
network collect and transmit to the Internet live information, like
the current number of passengers, expected time to arrival, the
amount of petrol left in the tank, etc. For a number of reasons
(network management, security, performance,...), it is desirable to
interconnect the Internet appliances deployed in cars, trains, busses
by means of, for instance, an Ethernet cable, instead of connecting
them individually and directly to the Internet, therefore exhibiting
the need to displace an entire network.
To describe such kind of scenarios, we need to agree on a
terminology. However, there is presently no existing terminology to
define the issues, goals, architecture elements, problems and
requirements pertaining to the scenarios outlined here above, but one
is needed. It is therefore the object of this document to propose
such a new terminology and to highlight some characteristics of
mobile networks.
The material presented in this document is based on [Ernst01] and on
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our former internet-draft that was submitted in July 2001 [OLD-draft]
for the consideration of the Mobile IP Working Group. In addition to
the present terminology, this former draft was also presenting a set
of requirements and issues as an attempt to clarify the problem
caused by network mobility. We decided to split this former document
in two because requirements are more subject to discussion and
disagreements than the terminology on which we must agree on to base
our discussion. Our proposed requirements can therefore now be found
in [REQUIREMENTS-1]. Additional requirements may be found in
[REQUIREMENTS-2] and [REQUIREMENTS-3]. A comprehensive description of
the problem and issues posed by network mobility is discussed in
[SCOPE]. More information may be found on the MONET web page [WEB-
MONET].
2. Terminology
The new terms we introduce comply with the terminology already
defined in the IPv6 [RFC2460] and Mobile IPv6 [MIPv6] specifications.
Although our terminology is primarily targeted toward IPv6, it is not
necessarily limited to it. This list comprises terms that appeared on
the mailing list for the purpose of explaining the problem scope.
Some of them may only be useful for the purpose of defining the
problem scope and functional requirements of network mobility
support. Definitions will have to be refined once we agree on the
problem scope.
The first section introduces terms to define the architecture
components; the second introduces terms to discuss nested mobility;
the last section introduces a number of other terms useful to discuss
requirements.
2.1. Architecture Components
Mobile Network
An entire network, moving as a unit, which dynamically changes its
point of attachment to the Internet and thus its reachability in
the topology. The mobile network is connected to the global
Internet via one or more mobile router(s) (MR). The internal
configuration of the mobile network is assumed to be relatively
stable with respect to the MR and is not a matter of concern.
Mobile Network Node (MNN)
Any host or router located within the mobile network, either
permanently or temporarily. A MNN could be any of a MR, LFN, VMN,
or LMN. The distinction between LFN, LMN and VMN is necessary to
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discuss issues related to mobility management and access control,
but does not preclude that mobility should be handled differently.
Nodes are classified according to their function and capabilities.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
______|__ foreign __|_____________ home
link __|_ link
| |
| MR | Mobile Router
|____|
_________|_______ internal
__|__ __|__ link
| | | |
| MNN | | MNN | Mobile Network Nodes
|_____| |_____|
Figure 1: Terminology
Mobile Router (MR)
A router which changes its point of attachment to the Internet and
which acts as a gateway to route packets between the mobile
network and the rest of the Internet. The MR is NEMO-enabled and
maintains the Internet connectivity for the mobile network. It has
at least two interfaces, an egress interface, and an ingress
interface. When transmitting a packet to the Internet (i.e.
outside), it forwards it through the egress interface; when
transmitting it withing the mobile network (i.e. inside), it
forwards it through the ingress interface.
Local Fixed Node (LFN)
A standard IPv6 node, either a host (LFH) or a router (LFR), that
belongs to the mobile network and which has no mobility support
capabilities at all (i.e. it isn't NEMO-enabled nor
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MIPv6-enabled).
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
__|_ _____|_____________ home
| | _|__ link
| MN ] | | |
|____| |__| MR | Mobile Router
| |____|
| __|_____________ internal
| __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal
link 2
Figure 2: Larger Mobile Network with 2 subnets
Local Mobile Node (LMN)
A mobile node, either a host (LMH) or a router (LMR), that belongs
to the mobile network (i.e. its home link is within the mobile
network). It is MIPv6-enabled and may be NEMO-enabled.
Visiting Mobile Node (VMN)
A mobile node, either a host (VMH) or a router (VMR), that doesn't
belong to the mobile network (i.e. its home link is not within the
mobile network), and which gets attached to a link within the
mobile network and obtains an address on that link. It is
MIPv6-enabled and may be NEMO-enabled.
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____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
__|_ _____|_____________ home
| | _|__ link
| MN | | | |
|____| _____ |__| MR | Mobile Router
| |__| |____|
|--> | LMN | | __|_____________ internal
| |_____| | __|__ | link 1
| _____ | | |
| | |__| | LFN |
| | LFN | | |_____| |
| |_____| | |
| | internal |
| link 2 |
|------------------------------|
Figure 3: LMN changing subnet
Node behind the MR
Any MNN in a mobile network that is not a MR for this mobile
network.
Correspondent Node (CN)
Any node that is communicating with one or more MNNs located in
the same mobile network. A CN could itself be located within the
mobile network.
Access Router (AR)
Any subsequent point of attachment of the MR at the network layer.
Basically, a router on the home link or the foreign link.
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Home subnet prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the MR's home link within the Internet
topology (i.e. the IP subnet prefix corresponding to the mobile
node's home address, as defined in [MIPv6]).
Foreign subnet prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the MR's foreign link within the Internet
topology.
Mobile Network Prefix
A bit string that consists of some number of initial bits of an IP
address which identifies the entire mobile network within the
Internet topology. All MNNs necessarily have an address named
after this prefix.
Egress Interface of a MR
The interface attached to the home link if the MR is at home, or
attached to a foreign link if the MR is in a foreign network.
Ingress Interface of a MR
The interface attached to a link inside the mobile network. This
interface is configured with the Mobile Network Prefix.
The terminology is summarized in fig.1 to 3. Fig.1 shows a single
mobile subnetwork. Fig.2. shows a larger mobile network comprising
several subnetworks. Fig.3 illustrates a LMN changing its point of
attachment within the mobile network.
2.2. Nested Mobility
We speak about nested mobility when there are more than one level of
mobility, i.e. when a VMN gets attached to the mobile network. A MNN
acts as an Access Router for this VMN.
If the VMN is actually a VMR with nodes behind it, this is a mobile
network which gets attached to a larger mobile network. The former is
a sub-MONET, and the latter the parent-MONET. It is generally
assumed that the sub-MONET and the parent-MONET become a single
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aggregated mobile network, i.e. the sub-MONET is indeed a subservient
of the larger MONET in terms of getting address space.
The MR(s) used to directly connect the aggregated mobile network to
the fixed Internet is referred to as the Top-Level Mobile Router
(TLMR) The terms upstream-MONET, downstream-MONET, and root-MONET
have also been introduced.
____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ home
| _|__ link
| | | |
| _____ |__| MR | Mobile Router
| | |__| |____|
----------> | VMN | | __|_____________ internal
|_____| | __|__ __|__ link 1
_____ | | | | |
| |__| | LFN | | LMN |
| LFN | | |_____| |_____|
|_____| |
| internal
link 2
Figure 4: Nested Mobility: single VMN that attaches to a mobile network
As for an instance of nested mobility, when a passenger carrying a
mobile phone (VMN) or a PAN (sub-MONET) gets Internet access from
the public access network deployed in the bus (parent-MONET).
Fig.4 and 5. illustrate nested mobility. In fig.4, a single VMN
gets attached to the mobile network. In fig 5, a VMR carrying an
entire network, thus a sub-MONET.
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____
| |
| CN |
|____|
___|____________________
| |
| |
| Internet |
| |
|________________________|
__|_ __|_
| | Access | |
| AR | Router | AR |
|____| |____|
_____|_____________ home
_|__ link
| | |
| _____ |__| MR | Mobile Router (TLMR)
|_| |__| |____|
| | VMR | | __|_____________ internal
| |_____| | __|__ __|__ link 1
_____ | | | | | |
| | | | | LFN | | LMN |
| LFN |__| | |_____| |_____|
|_____| | |
| | internal
link 2
<------------------> <--------------------------->
sub-MONET parent-MONET
Figure 5: Nested Mobility: sub-MONET that attaches to a larger
mobile network
2.3. Miscellaneous Terms
NEMO-enabled node
a node that has been extended with NEtwork MObility support
capabilities and may take special actions based on that. (Details
of the capabilities are not known yet, but it will be based on
enhancements to Mobile IPv6 [MIPv6] and may be implementing some
sort of Route Optimization).
MIPv6-enabled node
A mobile node that implements the "MN Operation" of Mobile IPv6
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[MIPv6]. I.e. A node that only implements the "CN Operation" of
Mobile IPv6 is NOT considered MIPv6-enabled.
Multihoming
Multihoming, as currently defined by the IETF, covers site-
multihoming [MULTI6] and host multihoming. Within host-
multihoming, a host may be either:
- multi-addressed: multiple source addresses to choose between
on a given interface; all IPv6 nodes are multi-addressed due to
the presence of link-local addresses on all interfaces.
- multi-interfaced: multiple interfaces according to [RFC2460]
definition.
- multi-linked: just like multi-interfaced but all interfaces
are NOT connected to the same link.
- multi-sited: when using IPv6 site-local address and attached
to different sites
What is meant by a multihomed-MONET is not clear and is left for
open discussion. It depends on the possible configurations covered
by the revised problem scope. Future discussion will assess if a
MR may fall in all the above described cases and if multiple MRs
may be used to connect the mobile network to the Internet.
Local-Area Mobility
Mobility within a single administrative domain, i.e. between
subnetworks topologically close in the IP hierarchy. In the
literature, and depending on the definition of ``closeness'', this
is also termed intra-site mobility, intra-domain mobility, local
mobility or micro-mobility. As an instance of Local-Area Mobility,
the displacement of a node within a limited vicinity of adjacent
subnetworks, like in a campus, that belong to the same
organization or between ARs that belong to the same ISP.
Wide-Area Mobility
Mobility across domain boundaries, i.e. between subnetworks
topologically distant in the IP hierarchy. In the literature, and
depending on the definition of ``remoteness'', this is also termed
inter-site mobility, inter-domain mobility, or global mobility, or
macro-mobility. As an instance of Wide-Area Mobility, displacement
of a node between distinct ISPs or organizations, or between
widely separated sites of a single organization.
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Idle MNN
A MNN that does not engage in any communication.
Idle Mobile Network
A mobile network that does not engage in any communication outside
the network may be considered as idle from the point of view of
the Internet. This doesn't preclude that MNNs are themselves idle.
Internal traffic between any two MNNs located in the same mobile
network is not concerned by this statement.
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3. Observations
Structure of the mobile network
A MR changing its point of attachment does not cause the MNNs
behind the MR to change their own physical point of attachment.
Thus, the internal structure of a mobile network is not modified
as a result of the mobile network changing its point of
attachment. MNNs may or may not notice such a displacement, but
they must not be required to be NEMO-enabled. However, MNNs MAY
appear to move from the point of view of an observer in the
Internet. In addition, the internal structure of the mobile
network is assumed to be relatively stable (no dynamic change of
the topology).
Mobile Router is a transit point
All packets sent from a CN to a MNN necessarily transit through a
MR.
Size of the mobile network
A mobile network may comprise one or more subnets. Its size could
scale from a sole subnet with a few IP devices, such as in the
case of a PAN, to a collection of subnets with hundreds of IP
devices, such as in a train.
Large number of CNs
A mobile network may have a very large number of CNs. For
instance, each passenger in a train may be considered a MNN. Each
of them may be communicating with a few CNs. As a result, the
total number of CNs could be several times as large as the number
of MNNs and scale up to a few thousands.
Sparseness of the CNs
CNs are typically sparsely distributed in the Internet and belong
to distinct administrative domains.
Handoff frequency
Mobile networks may not move with the same speed and frequency.
For instance, a PAN connected to the Internet via a 802.11b WLAN
(e.g. user in a shopping mall) is likely to change its point of
attachment very frequently, while an aircraft or a boat may be
connected to the Internet via the same satellite link for a couple
of hours. Obviously, mobile networks may not move at all for a
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large amount of time.
Dog-leg Routing
As a result of mobility, routing between a CN in the global
Internet and a mobile node may not be optimal. Packets usually
transit via the home link of the mobile node if no routing
optimization is explicitly performed. In network mobility,
multiple dog-leg routing may be introduced by nested mobility. In
this case, packets intended to a VMN may first transit by the
VMN's home link, then being rerouted to the MR's home link.
Ad-Hoc Network
An Ad-hoc network as defined in the IETF MANET Working Group is
not to be confused with a mobile network. An ad-hoc network is an
autonomous system made of mobile nodes (i.e. routers) connected by
wireless links. The routers are free to move randomly and to
organize themselves arbitrary. Topologies are highly dynamic. In a
mobile network, some routers may effectively move arbitrary, but
this not a common case. However, an Ad-hoc network connected to
the Internet and that changes its point of attachment may be
considered as a special instance of a mobile network.
Network mobility support (NEMO) and Mobile Ad-hoc Networking
(MANET) have not the same objectives. Network mobility support
aims at providing Internet reachability to nodes in the mobile
network and at maintaining session continuity after the mobile
network has changed its point of attachment in the topology. On
the other hand, MANET aims at maintaining routes between highly
dynamic nodes.
Routers in the Mobile Network
All routers in the Internet are considered to run a number of
protocols such as a routing protocol, Neighbor Discovery, ICMP,
and others. This also applies to routers in the mobile network,
including the MR.
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4. Changes from previous draft
- updated definition of LFN, LMN, VMN, mobile network, mobile network
prefix, CN
- added terms NEMO-enabled and MIPv6-enabled.
- added a section (2.2) for terminology specific to nested mobility:
root-MONET, parent-MONET, sub-MONET, upstream, downstream.
- added a paragraph about multihoming
- removed mobile IP-subnet.
- added comments about Ad-Hoc network in section 3
- added comments about multiple dog-leg routing in section 3
Acknowledgments
The first author would like to thank both Motorola Labs Paris and
INRIA Rhône-Alpes, for the opportunity to bring this topic to the
IETF, and particularly Claude Castelluccia (INRIA) for its advices,
suggestions, and direction. We also acknowledge Alexandru Petrescu
(Motorola), Christophe Janneteau (Motorola), Hesham Soliman
(Ericsson) and Mattias Petterson (Ericsson) for their comments on
this draft. We also thank people on the MONET mailing list for their
discussion which helped to improve this draft.
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References
[Ernst01] Thierry Ernst
"Network Mobility Support in IPv6", PhD Thesis,
University Joseph Fourier Grenoble, France. October
2001.
[MIPv6] David B. Johnson and C. Perkins.
"Mobility Support in IPv6".
Internet Draft draft-ietf-mobileip-ipv6-14.txt, July
2001.
Work in progress.
[MULTI6] B. Black, V. Gill and J. Abley
"Requirements for IPv6 Site-Multihoming
Architectures"
draft-ietf-multi6-multihoming-requirements-03
May 2002. Work in progress
[OLD-draft] Thierry Ernst, Hong-Yon Lach, Claude Castelluccia
"Network Mobility Support in IPv6: Problem Statement
and
Requirements",
Internet-Draft draft-ernst-mobileip-monetv6-00.txt,
July 2001.
Expired.
[Perkins98] C. E. Perkins.
"Mobile IP, Design Principles and Practices."
Wireless Communications Series. Addison-Wesley,
1998.
ISBN 0-201-63469-4.
[Quinot98] Thomas Quinot.
"An IPv6 architecture for Aeronautical
Telecommunication Network"
Master's thesis,
Ecole Nationale Superieure des Telecommunications
Paris,
EUROCONTROL - European Organization for the Safety
of Air Navigation
ISA project (IPv6, Satellite communication and
ATMode for ATN),
1998. http://www.eurocontrol.fr/.
[RFC1726] C. Partridge
"Technical Criteria for Choosing IP the Next
Generation (IPng)",
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IETF RFC 1726 section 5.15, December 1994.
[RFC2460] S. Deering and R. Hinden.
"Internet Protocol Version 6 (IPv6) Specification".
IETF RFC 2460, December 1998.
[RFC2002] C. Perkins (Editor).
"IP Mobility Support".
IETF RFC 2002,October 1996.
[REQUIREMENTS-1] Thierry Ernst, Hong Yon Lach
"Requirements for Network Mobility Support",
Internet-Draft draft-ernst-monet-
requirements-00.txt,
February 2001. Work in progress.
[REQUIREMENTS-2] Hong-Yon Lach, Christophe Janneteau, Alexandru
Petrescu
"Mobile Network Scenarios, Scope and Requirements",
Internet-Draft draft-lach-monet-requirements-00.txt,
February 2002. Work in progress.
[REQUIREMENTS-3] T.J. Kniveton
draft-kniveton-monet-requirements.txt, February
2002.
Work in progress.
[SCOPE] Hesham Soliman
"Problem Scope",
Internet-Draft draft-soliman-monet-scope-00.txt,
February 2002. Work in progress.
[Solomon98] J. D. Solomon.
"Mobile IP, The Internet Unplugged".
Prentice Hall Series in Computer Networking and
Distributed Systems.
Prentice Hall PTR, 1998. ISBN 0-13-856246-6.
[Tanenbaum96] Andrew Tanenbaum
"Computer Networks",
Prentice-Hall, Third Edition. 1996
[WEB-MONET] NEMO web page
http://www.nal.motlabs.com/monet
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Author's Addresses
Questions about this document can be directed to the authors:
Thierry Ernst,
French National Institute for Research in Computer Science and Control
Visiting Researcher at WIDE Project
Jun Murai lab. Faculty of Environmental Information,
Keio University.
5322 Endo, Fujisawa-shi, Kanagawa 252-8520, Japan.
Phone : +81-466-49-1100
Fax : +81-466-49-1395
E-mail: ernst@sfc.wide.ad.jp
Web: http://www.sfc.wide.ad.jp/~ernst/
Hong-Yon Lach
Motorola Labs Paris, Lab Manager,
Networking and Applications Lab (NAL)
Espace Technologique - Saint Aubin
91193 Gif-sur-Yvette Cedex, France
Phone: +33-169-35-25-36
Email: Hong-Yon.Lach@crm.mot.com
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