< draft-thubert-tree-discovery-05.txt   draft-thubert-tree-discovery-06.txt >
NEMO Working Group P. Thubert NEMO Working Group P. Thubert
Internet-Draft Cisco Internet-Draft Cisco
Expires: October 7, 2007 C. Bontoux Expires: January 4, 2008 C. Bontoux
Fortinet Fortinet
N. Montavont N. Montavont
LSIIT - ULP LSIIT - ULP
April 5, 2007 July 3, 2007
Nested Nemo Tree Discovery Nested Nemo Tree Discovery
draft-thubert-tree-discovery-05.txt draft-thubert-tree-discovery-06.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 37 skipping to change at page 1, line 37
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 7, 2007. This Internet-Draft will expire on January 4, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This paper describes a simple distance vector protocol that exposes This paper describes a simple distance vector protocol that exposes
only a default route towards the infrastructure in a nested NEMO only a default route towards the infrastructure in a nested NEMO
configuration. The draft extends the Neighbor Discovery Protocol [1] configuration. The draft extends the Neighbor Discovery Protocol [1]
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terms and Abbreviations . . . . . . . . . . . . . . . . . . . 4 2. Terms and Abbreviations . . . . . . . . . . . . . . . . . . . 4
3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Multi-Homed nested mobile network . . . . . . . . . . . . 5 3.1. Multi-Homed nested mobile network . . . . . . . . . . . . 5
3.2. Loops in nested Nemo . . . . . . . . . . . . . . . . . . . 6 3.2. Loops in nested Nemo . . . . . . . . . . . . . . . . . . . 6
4. Router Advertisement extensions . . . . . . . . . . . . . . . 8 4. Tree Information Option . . . . . . . . . . . . . . . . . . . 8
4.1. Router Advertisement message . . . . . . . . . . . . . . . 8 4.1. TIO base option . . . . . . . . . . . . . . . . . . . . . 8
4.2. Tree Information Option . . . . . . . . . . . . . . . . . 8 4.2. TIO suboptions . . . . . . . . . . . . . . . . . . . . . . 11
4.3. TIO suboption . . . . . . . . . . . . . . . . . . . . . . 11 4.2.1. Format . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3.1. Format . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2.2. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3.2. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.3. PadN . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.3.3. PadN . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2.4. Bandwidth Suboption . . . . . . . . . . . . . . . . . 12
4.3.4. Bandwidth Suboption . . . . . . . . . . . . . . . . . 12 4.2.5. Stable time Suboption . . . . . . . . . . . . . . . . 13
4.3.5. Stable time Suboption . . . . . . . . . . . . . . . . 13 4.2.6. Tree Group ID Suboption . . . . . . . . . . . . . . . 14
4.3.6. Tree Group ID Suboption . . . . . . . . . . . . . . . 14 4.2.7. Path Free Medium Time Suboption . . . . . . . . . . . 14
4.3.7. Path Free Medium Time Suboption . . . . . . . . . . . 14 4.2.8. Uniform Path Metric Suboption . . . . . . . . . . . . 15
5. Tree Discovery . . . . . . . . . . . . . . . . . . . . . . . . 16 5. Tree Discovery . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1. tree selection . . . . . . . . . . . . . . . . . . . . . . 17 5.1. tree selection . . . . . . . . . . . . . . . . . . . . . . 18
5.2. Sub-tree mobility . . . . . . . . . . . . . . . . . . . . 18 5.2. Sub-tree mobility . . . . . . . . . . . . . . . . . . . . 19
5.3. Administrative depth . . . . . . . . . . . . . . . . . . . 18 5.3. Administrative depth . . . . . . . . . . . . . . . . . . . 20
5.4. DRL entries states and stability . . . . . . . . . . . . . 18 5.4. DRL entries states and stability . . . . . . . . . . . . . 20
5.4.1. Held-Up . . . . . . . . . . . . . . . . . . . . . . . 19 5.4.1. Held-Up . . . . . . . . . . . . . . . . . . . . . . . 20
5.4.2. Held-Down . . . . . . . . . . . . . . . . . . . . . . 20 5.4.2. Held-Down . . . . . . . . . . . . . . . . . . . . . . 21
5.4.3. Collision . . . . . . . . . . . . . . . . . . . . . . 20 5.4.3. Collision . . . . . . . . . . . . . . . . . . . . . . 21
5.4.4. Instability . . . . . . . . . . . . . . . . . . . . . 21 5.4.4. Instability . . . . . . . . . . . . . . . . . . . . . 22
5.5. Legacy Routers . . . . . . . . . . . . . . . . . . . . . . 21 5.5. Legacy Routers . . . . . . . . . . . . . . . . . . . . . . 23
6. Directed Acyclic Graph Discovery . . . . . . . . . . . . . . . 21 6. Directed Acyclic Graph Discovery . . . . . . . . . . . . . . . 23
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Changes from version 00 to 01 . . . . . . . . . . . . . . 22 9.1. Changes from version 00 to 01 . . . . . . . . . . . . . . 24
9.2. Changes from version 01 to 02 . . . . . . . . . . . . . . 22 9.2. Changes from version 01 to 02 . . . . . . . . . . . . . . 24
9.3. Changes from version 02 to 03 . . . . . . . . . . . . . . 22 9.3. Changes from version 02 to 03 . . . . . . . . . . . . . . 24
9.4. Changes from version 03 to 04 . . . . . . . . . . . . . . 23 9.4. Changes from version 03 to 04 . . . . . . . . . . . . . . 24
9.5. Changes from version 04 to 05 . . . . . . . . . . . . . . 23 9.5. Changes from version 04 to 05 . . . . . . . . . . . . . . 24
9.6. Changes from version 05 to 06 . . . . . . . . . . . . . . 24
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
11.1. Normative Reference . . . . . . . . . . . . . . . . . . . 24 11.1. Normative Reference . . . . . . . . . . . . . . . . . . . 26
11.2. Informative Reference . . . . . . . . . . . . . . . . . . 24 11.2. Informative Reference . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . . . . . 26 Intellectual Property and Copyright Statements . . . . . . . . . . 28
1. Introduction 1. Introduction
As per Nemo Basic support [3], a Mobile Router autoconfigures a As per Nemo Basic support [3], a Mobile Router autoconfigures a
single Care of Address (CoA) to register to its Home Agent and single Care of Address (CoA) to register to its Home Agent and
terminate its Mobile Router-Home Agent tunnel. That Care of Address terminate its Mobile Router-Home Agent tunnel. That Care of Address
is the Mobile Router point of attachment to the nested Nemo. is the Mobile Router point of attachment to the nested Nemo.
Consequently, if loops are avoided, the nested Nemo assumes the shape Consequently, if loops are avoided, the nested Nemo assumes the shape
of a tree. The nodes of the tree are Mobile Routers, the root is of a tree. The nodes of the tree are Mobile Routers, the root is
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Attachment Router: The Router that is selected as Access Router by a Attachment Router: The Router that is selected as Access Router by a
Mobile Router, making it its parent in the nested NEMO tree. Mobile Router, making it its parent in the nested NEMO tree.
Propagation: The action by a Mobile Router that consists in Propagation: The action by a Mobile Router that consists in
receiving a Router Advertisement Tree Information Option from its receiving a Router Advertisement Tree Information Option from its
Attachment Router, recomputing a few specific fields, removing Attachment Router, recomputing a few specific fields, removing
unknown suboptions, and appending the resulting TIO to RAs sent unknown suboptions, and appending the resulting TIO to RAs sent
over the ingress interfaces. over the ingress interfaces.
Uniform Path Metric: A multihop metric that can be used by Tree
Discovery plug-ins to select feasible successors and specifically
an Attachment Router.
3. Motivations 3. Motivations
3.1. Multi-Homed nested mobile network 3.1. Multi-Homed nested mobile network
A nested mobile network that is made of multiple Mobile Routers A nested mobile network that is made of multiple Mobile Routers
having a direct connection to the Internet is said to be multi-homed. having a direct connection to the Internet is said to be multi-homed.
Multihoming in Nemo offers useful properties to Mobile Network Nodes. Multihoming in Nemo offers useful properties to Mobile Network Nodes.
The NEMO multihoming issues [7] draft lists potential multi-homed The NEMO multihoming issues [7] draft lists potential multi-homed
configurations for Nemo and explains the different problems and configurations for Nemo and explains the different problems and
advantages that some configurations may introduce. Multihoming advantages that some configurations may introduce. Multihoming
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of the router (low, medium or high). Furthermore, the same flag can of the router (low, medium or high). Furthermore, the same flag can
be set in the Route Information option indicating the preference of a be set in the Route Information option indicating the preference of a
specific prefix. Therefore, any node can determine its best default specific prefix. Therefore, any node can determine its best default
router(s) according to a given destination and its best router for router(s) according to a given destination and its best router for
default, which will be used by default. default, which will be used by default.
However this preference is only useful in a flat topology; It gives a However this preference is only useful in a flat topology; It gives a
way to the node to choose between different attachment routers way to the node to choose between different attachment routers
advertising prefixes on the node link. But if the node is inside a advertising prefixes on the node link. But if the node is inside a
hierarchical topology the node can not learn the depth of each hierarchical topology the node can not learn the depth of each
attachment router, and might not select the most efficient path. attachment router, and might not select the most efficient path. In
particular, there is a need for Uniform Path Metric that accounts for
a multihop wireless path.
One of the usage of the new option introduced in this document is to One of the usage of the new option introduced in this document is to
distribute information on the hierarchy of Mobile Routers. This distribute information on the hierarchy of Mobile Routers. This
information can be distributed to Attachment Routers, Mobile Routers information can be distributed to Attachment Routers, Mobile Routers
and Mobile Network Nodes as well in order to allow better route and Mobile Network Nodes as well in order to allow better route
selection and to increase the knowledge of the Nemo topology on each selection and to increase the knowledge of the Nemo topology on each
node. node.
3.2. Loops in nested Nemo 3.2. Loops in nested Nemo
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Each Mobile Router should be able to make its own attachment router Each Mobile Router should be able to make its own attachment router
selection based on its own condition (eg battery level), its own set selection based on its own condition (eg battery level), its own set
of constraints that may not apply to other Mobile Routers in the of constraints that may not apply to other Mobile Routers in the
tree, and in general its own algorithm. As a result, the tree, and in general its own algorithm. As a result, the
standardization effort should concentrate on a common minimum set of standardization effort should concentrate on a common minimum set of
rules that must be common to all Mobile Routers in order to prevent rules that must be common to all Mobile Routers in order to prevent
routing loops in the nested NEMO while leaving Mobile Routers routing loops in the nested NEMO while leaving Mobile Routers
independent in their Attachment Router selection algorithms. independent in their Attachment Router selection algorithms.
4. Router Advertisement extensions 4. Tree Information Option
New extensions of Router Advertisement are proposed to distribute the
knowledge of the Mobile Router hierarchy inside a nested Nemo. These
extensions are defined in different options/sub-options: a flag bit
from the reserved flag field of Router Advertisement message is used
to indicate whether the sending router is a Mobile Router or not; a
new option is defined to transport minimum information on the tree to
avoid loops generation;
4.1. Router Advertisement message
We propose to use a reserved flag of the Router Advertisement message
to inform whether the sending router is a Mobile Router or not.
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 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O|H|N|Reservd| Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options ...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 1: Router Advertisement
Nemo enabled router (N)
The Nemo enabled router (N) bit is set when the sending router is a
Mobile Router.
4.2. Tree Information Option
The Tree Information Option carries a number of metrics and other The Tree Information Option carries a number of metrics and other
information that allows a Mobile Router to discover a tree and select information that allows a Mobile Router to discover a tree and select
its point of attachment while avoiding loop generation. its point of attachment while avoiding loop generation.
The option is a container option, which might contain a number of 4.1. TIO base option
suboptions. The base option regroups the minimum information set
that is mandatory in all cases.
A TIO can also be used by Mobile Network Nodes to select their best The Tree Information Option is a container option, which might
default router. If the default router of a non-Mobile Router sends contain a number of suboptions. The base option regroups the minimum
Router Advertisements with a Tree Information Option, the non-Mobile information set that is mandatory in all cases.
Router MUST set the N flag of its own Router Advertisement to 0 and
copy the Tree Discovery Option in its own Router Advertisement.
0 1 2 3 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 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 | Length |G|H|B| Reserved| Sequence | | Type | Length |G|H|B| Reserved| Sequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TreePref. | BootTimeRandom | | TreePref. | BootTimeRandom |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MR Preference | TreeDepth | TreeDelay | | MR Preference | TreeDepth | TreeDelay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+ + + +
| TreeID | | TreeID |
+ + + +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-option(s)... | sub-option(s)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: RA Tree Information Option Figure 1: TIO base option
Type: 8-bit unsigned integer set to 10 by the clusterhead. Value is Type: 8-bit unsigned integer set to 10 by the clusterhead. Value is
"TBD". "TBD".
Length: 8-bit unsigned integer set to 4 when there is no suboption. Length: 8-bit unsigned integer set to 4 when there is no suboption.
The length of the option (including the type and length fields and The length of the option (including the type and length fields and
the suboptions) in units of 8 octets. the suboptions) in units of 8 octets.
Grounded (G): The Grounded (G) flag is set when the clusterhead is Grounded (G): The Grounded (G) flag is set when the clusterhead is
attached to a fixed network infrastructure (such as the Internet). attached to a fixed network infrastructure (such as the Internet).
Home (H): The Home (H) flag is set when the clusterhead is attached Home (H): The Home (H) flag is set when the Mobile Router is bound
to its home network. to its home network over NEMO. With NEMO Basic Support,a MR that
is not bound Home cuts off its visitors from the Internet as well.
This can be solved by techniques such as Reverse Routing Header
[8].
Battery (B): The Battery (B) flag is indicates that a parent in the Battery (B): The Battery (B) flag is indicates that a parent in the
tree operates on batteries, an indication of a costly operation. tree operates on batteries, an indication of a costly operation.
It is set by a mobile router which operates on battery and when It is set by a mobile router which operates on battery and when
set, it is left set as it is propagated down the tree. set, it is left set as it is propagated down the tree.
Reserved: 13-bit unsigned integer set to 0 by the clusterhead. Reserved: 5-bit unsigned integer set to 0 by the clusterhead.
Sequence Number: 8-bit unsigned integer set by the clusterhead and Sequence Number: 8-bit unsigned integer set by the clusterhead and
incremented with each new TIO it sends on a link and propagated incremented with each new TIO it sends on a link and propagated
with no change down the tree. with no change down the tree.
TreePreference: 8-bit unsigned integer set by the clusterhead to its TreePreference: 8-bit unsigned integer set by the clusterhead to its
preference and unchanged at propagation. Default is 0 (lowest preference and unchanged at propagation. Default is 0 (lowest
preference). The tree preference provides a mechanism to engineer preference). The tree preference provides a mechanism to engineer
the mesh of mobile routers, for instance indicating the most the mesh of mobile routers, for instance indicating the most
preferred home gateway or the communication ship in a fleet at preferred home gateway or the communication ship in a fleet at
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TreeID: 128-bit unsigned integer which uniquely identify a tree. TreeID: 128-bit unsigned integer which uniquely identify a tree.
This value is set by the clusterhead. The global IPv6 home This value is set by the clusterhead. The global IPv6 home
address of the clusterhead can be used. address of the clusterhead can be used.
The following values MUST not change during the propagation of the The following values MUST not change during the propagation of the
TIO down the tree: Type, Length, G, H, TreePreference, TreeDelay and TIO down the tree: Type, Length, G, H, TreePreference, TreeDelay and
TreeID. All other fields of the TIO are updated at each hop of the TreeID. All other fields of the TIO are updated at each hop of the
propagation. propagation.
4.3. TIO suboption 4.2. TIO suboptions
In addition to the minimum options presented in the base option, a In addition to the minimum options presented in the base option, a
number of suboptions are defined for the TIO: number of suboptions are defined for the TIO:
4.3.1. Format 4.2.1. Format
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subopt. Type | Subopt Length | Suboption Data... | Subopt. Type | Subopt Length | Suboption Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: TIO suboption generic format Figure 2: TIO suboption generic format
Suboption Type: 8-bit identifier of the type of mobility option. Suboption Type: 8-bit identifier of the type of mobility option.
When processing a TIO containing a suboption for which the When processing a TIO containing a suboption for which the
suboption Type value is not recognized by the receiver, the suboption Type value is not recognized by the receiver, the
receiver MUST silently ignore and skip over the suboption, receiver MUST silently ignore and skip over the suboption,
correctly handling any remaining options in the message. correctly handling any remaining options in the message.
Suboption Length: 8-bit unsigned integer, representing the length in Suboption Length: 8-bit unsigned integer, representing the length in
octets of the suboption, not including the suboption Type and octets of the suboption, not including the suboption Type and
Length fields. Length fields.
skipping to change at page 12, line 6 skipping to change at page 11, line 46
Implementations MUST silently ignore any TIO suboptions options that Implementations MUST silently ignore any TIO suboptions options that
they do not understand. they do not understand.
TIO suboptions may have alignment requirements. Following the TIO suboptions may have alignment requirements. Following the
convention in IPv6, these options are aligned in a packet so that convention in IPv6, these options are aligned in a packet so that
multi-octet values within the Option Data field of each option fall multi-octet values within the Option Data field of each option fall
on natural boundaries (i.e., fields of width n octets are placed at on natural boundaries (i.e., fields of width n octets are placed at
an integer multiple of n octets from the start of the header, for n = an integer multiple of n octets from the start of the header, for n =
1, 2, 4, or 8). 1, 2, 4, or 8).
4.3.2. Pad1 4.2.2. Pad1
The Pad1 suboption does not have any alignment requirements. Its The Pad1 suboption does not have any alignment requirements. Its
format is as follows: format is as follows:
0 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| Type = 0 | | Type = 0 |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 4: Pad 1 Figure 3: Pad 1
NOTE! the format of the Pad1 option is a special case - it has NOTE! the format of the Pad1 option is a special case - it has
neither Option Length nor Option Data fields. neither Option Length nor Option Data fields.
The Pad1 option is used to insert one octet of padding in the TIO to The Pad1 option is used to insert one octet of padding in the TIO to
enable suboptions alignment. If more than one octet of padding is enable suboptions alignment. If more than one octet of padding is
required, the PadN option, described next, should be used rather than required, the PadN option, described next, should be used rather than
multiple Pad1 options. multiple Pad1 options.
4.3.3. PadN 4.2.3. PadN
The PadN option does not have any alignment requirements. Its format The PadN option does not have any alignment requirements. Its format
is as follows: is as follows:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
| Type = 1 | Subopt Length | Subopt Data | Type = 1 | Subopt Length | Subopt Data
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - -
Figure 5: Pad N Figure 4: Pad N
The PadN option is used to insert two or more octets of padding in The PadN option is used to insert two or more octets of padding in
the TIO to enable suboptions alignment. For N (N > 1) octets of the TIO to enable suboptions alignment. For N (N > 1) octets of
padding, the Option Length field contains the value N-2, and the padding, the Option Length field contains the value N-2, and the
Option Data consists of N-2 zero-valued octets. PadN Option data Option Data consists of N-2 zero-valued octets. PadN Option data
MUST be ignored by the receiver. MUST be ignored by the receiver.
4.3.4. Bandwidth Suboption 4.2.4. Bandwidth Suboption
This suboption carries the maximum bandwidth available up the tree This suboption carries the maximum bandwidth available up the tree
via a specific parent. It is the lowest speed of the links on the via a specific parent. It is the lowest speed of the links on the
way and does not reflect the actual use of those links in run time. way and does not reflect the actual use of those links in run time.
The value is expressed in the log base 2 of the speed, expressed in The value is expressed in the log base 2 of the speed, expressed in
bps. The Bandwidth suboption does not have any alignment bps. The Bandwidth suboption does not have any alignment
requirements. Its format is as follows: requirements. Its format is as follows:
0 1 2 0 1 2
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+
| Type = 2 | Length = 1 | Bandwidth | | Type = 2 | Length = 1 | Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+
Figure 6: Bandwidth Suboption Figure 5: Bandwidth Suboption
Type: Set to 2 for the Bandwidth suboption. Type: Set to 2 for the Bandwidth suboption.
Length: Set to 1 for the Bandwidth suboption. Length: Set to 1 for the Bandwidth suboption.
Bandwidth: 8-bit unsigned integer. The Log2 of the speed of the Bandwidth: 8-bit unsigned integer. The Log2 of the speed of the
path expressed in bps. The clusterhead initializes that field path expressed in bps. The clusterhead initializes that field
using the speed of the link to the Access Router to which it is using the speed of the link to the Access Router to which it is
attached or 0xFF if it is floating. An attached MR propagates it attached or 0xFF if it is floating. An attached MR propagates it
as the minimum of the Bandwidth as received in the TIO from the as the minimum of the Bandwidth as received in the TIO from the
parent and the access speed between the MR and the parent. As a parent and the access speed between the MR and the parent. As a
result, the value received from a candidate AR is that of the result, the value received from a candidate AR is that of the
bottleneck between that AR and the wire access. bottleneck between that AR and the wire access.
4.3.5. Stable time Suboption 4.2.5. Stable time Suboption
This suboption carries an indicator of the stability of a network. This suboption carries an indicator of the stability of a network.
This indicator is the time since the branch to which the MR is This indicator is the time since the branch to which the MR is
attached has remained unchanged. The value is expressed in the log attached has remained unchanged. The value is expressed in the log
base 2 of that duration, expressed in milliseconds. The Stable time base 2 of that duration, expressed in milliseconds. The Stable time
suboption does not have any alignment requirements. Its format is as suboption does not have any alignment requirements. Its format is as
follows: follows:
0 1 2 0 1 2
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+
| Type = 3 | Length = 1 | Stable time | | Type = 3 | Length = 1 | Stable time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------+
Figure 7: Stable time Figure 6: Stable time
Type: Set to 3 for the Stable time suboption. Type: Set to 3 for the Stable time suboption.
Length: Set to 1 for the Stable time suboption. Length: Set to 1 for the Stable time suboption.
Stable time: 8-bit unsigned integer. The Log2 of the time since the Stable time: 8-bit unsigned integer. The Log2 of the time since the
last change in the attachment branch, expressed in milliseconds. last change in the attachment branch, expressed in milliseconds.
This is set by the MR as it propagates the TIO down the tree, This is set by the MR as it propagates the TIO down the tree,
indicating for how long the PathDigest in the TIO from its parent indicating for how long the PathDigest in the TIO from its parent
has remained unchanged. has remained unchanged.
4.3.6. Tree Group ID Suboption 4.2.6. Tree Group ID Suboption
This suboption carries the Group ID for the tree. It is set by the This suboption carries the Group ID for the tree. It is set by the
clusterhead and is left unchanged by the MR that propagates the TIO clusterhead and is left unchanged by the MR that propagates the TIO
down the tree. The Tree Group ID Suboption has an alignment down the tree. The Tree Group ID Suboption has an alignment
requirement of 8n+6. Its format is as follows: requirement of 8n+6. Its format is as follows:
0 1 2 3 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 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 = 4 | Length = 16 | | Type = 4 | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| Tree | | Tree |
+ Group ID + + Group ID +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Tree Group ID Suboption Figure 7: Tree Group ID Suboption
Type: 8-bit unsigned integer. Its value is 4 for the Tree Group ID Type: 8-bit unsigned integer. Its value is 4 for the Tree Group ID
suboption. suboption.
Length: 8-bit unsigned integer. Its value is 16 for the Tree Group Length: 8-bit unsigned integer. Its value is 16 for the Tree Group
ID suboption. ID suboption.
Tree Group ID: 128-bit unsigned integer which identify a group for a Tree Group ID: 128-bit unsigned integer which identify a group for a
tree. This value is set by the clusterhead. It can be set tree. This value is set by the clusterhead. It can be set
administratively, for instance to an IPv6 multicast group. administratively, for instance to an IPv6 multicast group.
4.3.7. Path Free Medium Time Suboption 4.2.7. Path Free Medium Time Suboption
This suboption carries the Free Medium Time available up the tree via This suboption carries the Free Medium Time available up the tree via
a specific parent at a given point of time. It is an indication of a specific parent at a given point of time. It is an indication of
whether bandwidth is available to place VoIP calls for instance. As whether bandwidth is available to place VoIP calls for instance. As
defined by the Quality of Service (QoS) Task Group of the Wi-Fi defined by the Quality of Service (QoS) Task Group of the Wi-Fi
Alliance, the Medium Time describes the amount of time admitted to Alliance, the Medium Time describes the amount of time admitted to
access the medium, in units of 32 microsecond periods per second. access the medium, in units of 32 microsecond periods per second.
The Free Medium Time is the amount of time left the medium, in other The Free Medium Time is the amount of time left the medium, in other
words ((1000000/32) - SIGMA(MT)). The Path Free Medium Time is the words ((1000000/32) - SIGMA(MT)). The Path Free Medium Time is the
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The Path Free Medium Time suboption does not have any alignment The Path Free Medium Time suboption does not have any alignment
requirements. Its format is as follows: requirements. Its format is as follows:
0 1 2 3 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 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 = 5 | Length = 2 | Path Free Medium Time | | Type = 5 | Length = 2 | Path Free Medium Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Path Free Medium Time Suboption Figure 8: Path Free Medium Time Suboption
Type: Set to 5 for the Path Free Medium Time Suboption. Type: Set to 5 for the Path Free Medium Time Suboption.
Length: Set to 2 for the Path Free Medium Time Suboption. Length: Set to 2 for the Path Free Medium Time Suboption.
Path Free MT: 16-bit unsigned integer. The amount of Medium Time Path Free MT: 16-bit unsigned integer. The amount of Medium Time
that is available along the path to the clusterhead in units of 32 that is available along the path to the clusterhead in units of 32
microsecond periods per second. The clusterhead initializes that microsecond periods per second. The clusterhead initializes that
field to the Free MT on the link where the TIO is issued. An field to the Free MT on the link where the TIO is issued. An
attached MR propagates it as the minimum of the Path Free MT as attached MR propagates it as the minimum of the Path Free MT as
received in the TIO from the parent and the Path Free MT on the received in the TIO from the parent and the Path Free MT on the
link on which the TIO is propagated. As a result, the value link on which the TIO is propagated. As a result, the value
received from a candidate AR is that of the bottleneck between received from a candidate AR is that of the bottleneck between
that AR and the clusterhead. that AR and the clusterhead.
4.2.8. Uniform Path Metric Suboption
This suboption carries the Uniform Path Metric for the path along the
tree. It is set to zero by the clusterhead and incremented as the
TIO is propagated down the tree. The Uniform Path Metric Suboption
has an alignment requirement of 4n+2. Its format is as follows:
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 = 6 | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Uniform Path Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Uniform Path Metric Suboption
Type: 8-bit unsigned integer. Its value is 6 for the Uniform Path
Metric.
Length: 8-bit unsigned integer. Its value is 4 for the Uniform Path
Metric suboption.
Uniform Path Metric: 32-bit unsigned integer aggragating the cost of
multiple radio hops.
5. Tree Discovery 5. Tree Discovery
Here follows a set of rules and definitions that MUST be followed by Tree Discovery is a form of distance vector protocol for use in
all Mobile Routers: wireless mesh networks. TD locates the nearest exit and forms a
Directed Acyclic Graphs towards that exit, usually a tree. TD
enables Mobile Routers to implement different policies for selecting
their preferred parent in the Tree by introducing the concept of
plug-in, and does not specify the plug-in operation. Rather, TD
specifies a set of rules to be implemented by all plug-ins to ensure
interoperation. TD also standardizes the format that is used to
advertize the most common information that is used by the plug-ins in
order to perform the parent selection.
One of these information, the tree depth, is used by Tree Discovery
to provide loop avoidance between plug-ins even if they implement
different policies, and even if these policies do not use the depth
as a routing metric. For instance, a MR might use the Uniform Path
Metric to select the nearest exit and the best parent from the
standpoint of that metric. Once attached to that parent, the MR
exposes a depth which is incremented from the parent's depth, and
that depth provides a comparable basis with routers which would not
use UPM at all.
In order organize and maintain loopless structure, the selection
plug-ins in the Mobile Routers MUST obey to the following rules and
definitions:
1. A Mobile Router that is not attached to an Attachment Router is 1. A Mobile Router that is not attached to an Attachment Router is
the Nemo clusterhead of its own floating tree. It's depth is 1. the Nemo clusterhead of its own floating tree. It's depth is 1.
A Mobile Router will end up in that situation when it looses its A Mobile Router will end up in that situation when it looses its
current parent and there is no alternate parent that it can current parent and there is no alternate parent that it can
attach to. In that case, the MR remembers the treeID and the attach to. In that case, the MR remembers the treeID and the
sequence counter in the TIO of the lost parent for a period of sequence counter in the TIO of the lost parent for a period of
time which covers multiple TIO. time which covers multiple TIO.
2. A Mobile Router that is attached to an Attachment Router that 2. A Mobile Router that is attached to an Attachment Router that
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time and with no delay in order to get closer to the clusterhead time and with no delay in order to get closer to the clusterhead
of its current tree - i.e. in order to reduce its own tree depth. of its current tree - i.e. in order to reduce its own tree depth.
But A Mobile Router MUST NOT move down the tree that it is But A Mobile Router MUST NOT move down the tree that it is
attached to. Mobile Routers MUST ignore RAs that are received attached to. Mobile Routers MUST ignore RAs that are received
from other routers located deeper within the same tree. from other routers located deeper within the same tree.
6. A Mobile Router may move from its current tree into any different 6. A Mobile Router may move from its current tree into any different
tree at any time and whatever the depth it reaches in the new tree at any time and whatever the depth it reaches in the new
tree, but it may have to wait for a Tree Hop timer to elapse in tree, but it may have to wait for a Tree Hop timer to elapse in
order to do so. If the MR was clusterhead of its own floating order to do so. If the MR was clusterhead of its own floating
tree, it may not join its previous identified by the last parent tree, it may not join its previous tree (identified by the last
treeID tree unless the sequence number is the TIO was parent treeID) unless the sequence number is the TIO was
incrememented since the MR left that tree, indicating that the incrememented since the MR left that tree, indicating that the
candidate parent was not attached behind this MR and kept getting candidate parent was not attached behind this MR and kept getting
subsequent TIOs from the same tree. The Mobile Router will join subsequent TIOs from the same tree. The Mobile Router will join
that other tree if it is more preferable for reasons of that other tree if it is more preferable for reasons of
connectivity, configured preference, free Medium Time, size, connectivity, configured preference, free Medium Time, size,
security, bandwidth, tree depth, or whatever metrics the Mobile security, bandwidth, tree depth, or whatever metrics the Mobile
Router cares to use. Router cares to use.
7. If a Mobile Router has selected a new attachment router but has 7. If a Mobile Router has selected a new attachment router but has
not moved yet (because it is waiting for Tree Hop timer to not moved yet (because it is waiting for Tree Hop timer to
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does so, a MR can elect a number of alternate parents as feasible does so, a MR can elect a number of alternate parents as feasible
successors. A feasible successor belongs to the same tree as the MR successors. A feasible successor belongs to the same tree as the MR
parent, and has a depth that is less than that of the MR. parent, and has a depth that is less than that of the MR.
The links MR to feasible successors complete the tree as built by TD The links MR to feasible successors complete the tree as built by TD
into a DAG towards the clusterhead. The DAG enables alternate exit into a DAG towards the clusterhead. The DAG enables alternate exit
paths for a multihomed Mobile Router. paths for a multihomed Mobile Router.
7. IANA Considerations 7. IANA Considerations
Section 4.2. requires the definition of a new option to Neighbor Section 4.1. requires the definition of a new option to Neighbor
discovery [1] messages, the Router Advertisement - Tree Information discovery [1] messages, the Router Advertisement - Tree Information
Option (RA-TIO). The Router Advertisement - Tree Information Option Option (RA-TIO). The Router Advertisement - Tree Information Option
has been assigned the value TBD within the numbering space for IPv6 has been assigned the value TBD within the numbering space for IPv6
Neighbor Discovery Option Formats. Neighbor Discovery Option Formats.
8. Security Considerations 8. Security Considerations
At the current level of this draft, the TIO bears the security level At the current level of this draft, the TIO bears the security level
of the RA and the link. Nothing is added to it. A deeper threat of the RA and the link. Nothing is added to it. A deeper threat
analysis would be required to eventually propose additional security. analysis would be required to eventually propose additional security.
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Added suboptions for Path Free Medium Time. Added suboptions for Path Free Medium Time.
9.5. Changes from version 04 to 05 9.5. Changes from version 04 to 05
Added a sequence counter which provides additional loop protection Added a sequence counter which provides additional loop protection
based on a comment by Christipher Dearlove. For the sake of the based on a comment by Christipher Dearlove. For the sake of the
discussion, note that if a loop were to occur, the count to discussion, note that if a loop were to occur, the count to
infinity would actually cause the MR taht reaches the max depth to infinity would actually cause the MR taht reaches the max depth to
detach and that would resolve the issue anyway. detach and that would resolve the issue anyway.
9.6. Changes from version 05 to 06
Added the Uniform Path Metric. Removed the N bit in RA and
changed the semantics of the H bit in TIO. Added some test at teh
beginning of the Tree Discovery section to explain the role of the
depth vs. the plug-ins.
10. Acknowledgments 10. Acknowledgments
The authors wish to thank Marco Molteni and Patrick Wetterwald The authors wish to thank Marco Molteni and Patrick Wetterwald
(cisco) for their participation to this design and the review of the (cisco) for their participation to this design and the review of the
document, Massimo Villari (university of Messina), for his early work document, Massimo Villari (university of Messina), for his early work
on simulation and research on the subject and Julien Abeille for his on simulation and research on the subject and Julien Abeille for his
advanced participation in simulation and real testing. Also the advanced participation in simulation and real testing. Also the
authors wish to thank Christopher Dearlove for his suggestion to add authors wish to thank Christopher Dearlove for his suggestion for
a sequence counter which provides additional protection against loop additional protection against loops in TD. This work is also based
formation. This work is also based on prior publications, in on prior publications, in particular HMRA [6] by Hosik Cho and Eun-
particular HMRA [6] by Hosik Cho and Eun-Kyoung Paik from Seoul Kyoung Paik from Seoul National University and other non IETF
National University and other non IETF publications coauthored with publications coauthored with Thierry Ernst and Thomas Noel. Finally,
Thierry Ernst and Thomas Noel. Finally, thanks to Marcelo Bagnulo the authors heartily thank Marcelo Bagnulo Braun and Teco Boot for
Braun for his constructive review. their very constructive reviews.
11. References 11. References
11.1. Normative Reference 11.1. Normative Reference
[1] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery [1] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998. for IP Version 6 (IPv6)", RFC 2461, December 1998.
[2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in [2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004. IPv6", RFC 3775, June 2004.
skipping to change at page 24, line 33 skipping to change at page 26, line 33
[5] Draves, R. and D. Thaler, "Default Router Preferences and More- [5] Draves, R. and D. Thaler, "Default Router Preferences and More-
Specific Routes", RFC 4191, November 2005. Specific Routes", RFC 4191, November 2005.
11.2. Informative Reference 11.2. Informative Reference
[6] Cho, H., "Hierarchical Mobile Router Advertisement for nested [6] Cho, H., "Hierarchical Mobile Router Advertisement for nested
mobile networks", draft-cho-nemo-hmra-00 (work in progress), mobile networks", draft-cho-nemo-hmra-00 (work in progress),
January 2004. January 2004.
[7] Ng, C., "Analysis of Multihoming in Network Mobility Support", [7] Ng, C., "Analysis of Multihoming in Network Mobility Support",
draft-ietf-nemo-multihoming-issues-06 (work in progress), draft-ietf-nemo-multihoming-issues-07 (work in progress),
June 2006. February 2007.
[8] Thubert, P. and M. Molteni, "IPv6 Reverse Routing Header and its
application to Mobile Networks",
draft-thubert-nemo-reverse-routing-header-07 (work in progress),
February 2007.
Authors' Addresses Authors' Addresses
Pascal Thubert Pascal Thubert
Cisco Systems Cisco Systems
Village d'Entreprises Green Side Village d'Entreprises Green Side
400, Avenue de Roumanille 400, Avenue de Roumanille
Batiment T3 Batiment T3
Biot - Sophia Antipolis 06410 Biot - Sophia Antipolis 06410
FRANCE FRANCE
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