Internet DRAFT - draft-ietf-roll-capabilities
draft-ietf-roll-capabilities
ROLL R.A. Jadhav, Ed.
Internet-Draft Huawei
Intended status: Standards Track P. Thubert
Expires: 13 May 2022 Cisco
M. Richardson
Sandelman Software Works
R.N. Sahoo
Juniper
9 November 2021
RPL Capabilities
draft-ietf-roll-capabilities-09
Abstract
This draft enables the discovery, advertisement and query of
capabilities for RPL nodes.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 13 May 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language and Terminology . . . . . . . . . . 3
1.2. What are Capabilities? . . . . . . . . . . . . . . . . . 4
2. Requirements for this document . . . . . . . . . . . . . . . 4
2.1. How are Capabilities different from existing RPL
primitives? . . . . . . . . . . . . . . . . . . . . . . . 4
3. Capabilities . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Capability Control Message Option . . . . . . . . . . . . 5
3.2. Capabilities Handshake . . . . . . . . . . . . . . . . . 6
4. Querying Capabilities . . . . . . . . . . . . . . . . . . . . 6
4.1. Capability Query (CAPQ) . . . . . . . . . . . . . . . . . 6
4.1.1. Capability Type List Control Option . . . . . . . . . 7
4.1.2. Secure CAPQ . . . . . . . . . . . . . . . . . . . . . 7
4.1.3. Base rules for CAPQ handling . . . . . . . . . . . . 7
4.2. Capability Set Response (CAPS) . . . . . . . . . . . . . 7
4.2.1. Secure CAPS . . . . . . . . . . . . . . . . . . . . . 8
5. Guidelines for defining new capabilities . . . . . . . . . . 8
5.1. Handling Capability flags . . . . . . . . . . . . . . . . 8
5.1.1. Rules to handle capabilities flag . . . . . . . . . . 9
6. Node Capabilities . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Capability Indicators . . . . . . . . . . . . . . . . . . 9
6.1.1. Format of Capability Indicators . . . . . . . . . . . 9
6.2. Routing Resource Capability . . . . . . . . . . . . . . . 10
6.2.1. Format of Routing Resource Capability . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8.1. New option: Capabilities . . . . . . . . . . . . . . . . 11
8.2. Capability Sub-Type . . . . . . . . . . . . . . . . . . . 12
8.3. New Registry for CAPQ Flags . . . . . . . . . . . . . . . 12
8.4. New Registry for Capabilities Flags . . . . . . . . . . . 12
8.5. New Registry for Capabilities Indicators . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Capability Handshake Example . . . . . . . . . . . . 14
A.1. Query supported Cap Types . . . . . . . . . . . . . . . . 14
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A.2. Query specific Cap Set . . . . . . . . . . . . . . . . . 15
A.3. CAPS with partial Cap Set . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
RPL [RFC6550] specifies a proactive distance-vector based routing
scheme. The protocol creates a DAG-like structure which operates
with a given "Mode of Operation" (MOP) determining the minimal and
mandatory set of primitives to be supported by all the participating
nodes.
This document adds a notion of capabilities using which nodes in the
network could inform its peers about its additional capabilities.
This document highlights the differences of capabilities from that of
Mode of operation and explains the necessity of it.
1.1. Requirements Language and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
MOP: Mode of Operation. Identifies the MOP of the RPL Instance as
administratively provisioned at and distributed by the DODAG root.
MOPex: Extended MOP: As defined in [I-D.ietf-roll-mopex].
Capabilities: Additional features or capabilities that are supported
by the node.
Cap: Abbreviated term used for Capability.
Caps: Abbreviated term used for Capabilities.
DAO: DODAG Advertisement Object. An RPL message used to advertise
the target information in order to establish routing adjacencies.
DIO: DODAG Information Object. An RPL message initiated by the root
and is used to advertise the network configuration information.
Current parent: Parent 6LR node before switching to the new path.
NPDAO: No-Path DAO. A DAO message which has target with lifetime 0.
Upstream path/direction: Path or direction from the node to the Root
in a DAG.
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Downstream path/direction: Path or direction to the node from the
Root in a DAG.
This document uses terminology described in [RFC6550]. For the sake
of readability all the known relevant terms are repeated in this
section.
1.2. What are Capabilities?
Currently RPL specification does not have a mechanism whereby a node
can signal the set of features that are available on its end. Such a
mechanism could help the root to advertise its capabilities and in
response also determine some advanced information about the
capabilities of the joining nodes. This document defines
Capabilities which could be supported by the nodes and handshaked as
part of RPL signaling. Capabilities are embedded as an RPL Control
Message Option as defined in Section 6.7 of [RFC6550].
2. Requirements for this document
Following are the requirements considered for this documents:
REQ1: Backwards compatibility. The new options and new fields in
the DIO message should be backward compatible i.e. if there
are nodes which support old MOPs they could still operate in
their own instances.
REQ2: Optional capabilities handshake. Capabilities are features,
possibly optional, which could be handshaked between the nodes
and the root within an RPL Instance.
REQ3: Capabilities handshake could be optionally added with existing
MOPs. Capabilities been optional in nature could be put to
use with existing MOPs. Capabilities and MOP-extension is
mutually independent i.e. a DIO can have a capabilities
option, MOP-extension option or both in the same message.
REQ4: Capabilities could be explicitly queried.
2.1. How are Capabilities different from existing RPL primitives?
The Mode of Operation (MOP) field in RPL mandates the operational
requirement for the nodes joining as routers. MOP and DIO
Configuration Option is strictly controlled by the Root node in RPL.
Intermediate 6LRs cannot modify these fields. Also, the MOP never
changes for the lifetime of the RPL Instance. Changes in DIO
Configuration Option are possible but are rare. Capabilities, on the
other hand, might change more dynamically.
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RPL DIO message also carries routing metrics and constraints as
specified in [RFC6551]. Metrics and constraints are used as part of
objective function which aids in node's rank calculation. A router
may use capabilities carried in DIO message as additional metrics/
constraints. However, capabilities have a larger scope and may be
carried in other messages other than DIO and can flow in both the
directions (upstream and downstream).
3. Capabilities
Handling of Capabilities MUST be supported if the network uses MOPex
[I-D.ietf-roll-mopex].
Note that capabilities and MOPex are mutually exclusive and it is
possible for an implementation to support either or both of the
options.
3.1. Capability Control Message Option
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 = TODO | Option Length | Capabilities TLVs
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Capabilities Option
Multiple capabilities could be sent in the same message. The length
field allows the message parser to skip the capability TLV parsing.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CapType | Len |J|I|C| Flags | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Capabilities TLV
Every capability is identified by its type and it may have an
optional Capability Info. Note that a given capability may or may
not be diseminated with additional information depending on the scope
of the capability indicated by the I bit.
Len: 8-bit unsigned integer, representing the length in octets of the
TLV, not including the CapType, Length and Flags fields.
J = Join only as leaf if capability not understood.
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I = Ignore the message if this capability is not understood.
C = Flag indicating that the capability MUST be copied in the
downstream message.
3.2. Capabilities Handshake
The root node could advertise the set of capabilities it supports in
the DIO message. A node could take advantage of the knowledge that
the root supports a particular capability. Similarly a node could
advertise its capabilities in the DAO message using the capability
control message option defined in this document. Capabilities
advertised by non-root nodes are strictly a subset of the
capabilities advertised by the root.
In storing MOP, the DAO message from the 6LR could contain multiple
target options because of the DAO-Aggregation. The targets of the
capabilities option are indicated by one or more Target options that
precede the Capabilities Option. This handling is similar to the
Transit Information Option as supported in Section 6.7.8. of
[RFC6550].
4. Querying Capabilities
Nodes may be interested in knowing the capabilities of another node
before taking an action. For e.g., Consider
[I-D.ietf-roll-dao-projection], the Root may want to know the
capabilities of the nodes along a network segment before it initiates
a projected DAO to install the routes along that segment.
Caps can be carried in existing RPL Control messages as Control
Options, however Caps can also be queried explicitly. This section
provides a way for a node to query capability set of another node.
The capability query and subsequent response messages are directly
addressed between the two peers.
4.1. Capability Query (CAPQ)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID | Flags | reserved | CAPQSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 3: CAPQ base object
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CAPQSequence: One byte, Sequence number sent by the CAPQ sender
which is reflected back by the responder in the CAPS message.
Flags: One byte, set to zero by sender, ignored by receiver.
reserved: One byte, set to zero by sender, ignored by receiver.
CAPQ base object may be followed by one or more options. The
Capability Type List Control Option Figure 4 is used to carry a set
of capability types to query about.
If the sender does not send Figure 4 option, this would indicate that
the node intends to query the capability type list Figure 4 supported
by the target node.
4.1.1. Capability Type List Control Option
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 = TODO | Option Length | CapType1 | CapType2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CapType3 | .....
+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Capability Type List Control Option
4.1.2. Secure CAPQ
A Secure CAPQ message follows the format in [RFC6550] Figure 7, where
the base message format is the CAPQ message shown in Figure 3.
4.1.3. Base rules for CAPQ handling
A CAPQ message may get dropped or lost in the transit. The sender of
CAPQ MAY retry the CAPQ message after some delay. The delay SHOULD
NOT be less than 1 second.
4.2. Capability Set Response (CAPS)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RPLInstanceID | Flags | Reserved | CAPQSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
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Figure 5: CAPS base object
Flags: One byte, set to zero by sender, ignored by receiver.
reserved: One byte, set to zero by sender, ignored by receiver.
CAPQSequence: One byte, Sequence number copied from CAPQSequence
received in the CAPQ message.
CAPS message SHOULD contain the capability set Figure 1 queried by
the CAPQ sender. If the target node does not support subset of the
queried capabilities then the Figure 4 option with the unsupported
cap-types SHOULD be sent back indicating the queried capabilities
not-supported by the target node. For an example, check Appendix A.3
If the CAPQ message does not contain any Figure 4 option then the
receiver MUST respond with the cap types it supports using Figure 4.
If the capability set cannot be transmitted in a single message (for
e.g., because of MTU limitations) then multiple CAPS messages could
be used. All the CAPS message MUST use the same CAPQSequence number
copied from the corresponding CAPQ message.
4.2.1. Secure CAPS
A Secure CAPS message follows the format in [RFC6550] Figure 7, where
the base message format is the CAPS message shown in Figure 5.
5. Guidelines for defining new capabilities
This section provides guidelines/recommendations towards defining new
capabilities. Note that the capabilities might be carried as part of
the multicast messaging such as DIO and hence the set should be used
in restrictive manner as far as possible.
5.1. Handling Capability flags
A node MUST drop or discard the message with an unknown capability
with 'D' flag set. The message MUST be discarded silently.
The 'J' (join) flag can be set in context to a capability either by a
6LR or the root. The 'J' flag indicates that if the capability is
not supported by a node then it can join the instance only as a 6LN
(or do not join as 6LR).
The 'C' (copy) flag is set by the node indicating that the
capabilities MUST be copied downstream by the node even if the node
does not understand the capability.
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5.1.1. Rules to handle capabilities flag
On receiving a capability it does not support, the node MUST check
the 'J' flag of the capability before joining the Instance. If the
'J' flag is set then it can only join as a 6LN.
If the node is operating as 6LR and subsequently it receives a
capability from its preferred parent which it does not understand
with 'J' flag set, then the node has to switch itself to 6LN mode.
During switching the node needs to inform its downstream peers of its
changed status by sending a DIO with infinite rank as mentioned in
RFC6550. Alternatively, a node may decide to switch to another
parent with compatible and known capabilities.
Capabilities are used to indicate a feature that is supported by the
node. Capabilities are not meant for configuration management for
e.g., setting a threshold.
6. Node Capabilities
6.1. Capability Indicators
Capability Indicators indicates the capabilities supported by the
node in the form of simple flags. Capabilities who do not have
additional information to be specified could make use of these flags
to indicate their support.
6.1.1. Format of Capability Indicators
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CapType=0x01 | Len |J|I|C| Flags |T|..Indicators..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Capability Indicators TLV
Flags: LRs MUST set it to 0. I bit will always be set to 0.
T flag (Bit 1): Indicates whether the node supports 6LoRH [RFC8138].
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6.2. Routing Resource Capability
Storing mode of operation requires each intermediate router in the
LLN to maintain routing states' information in the routing table.
LLN routers typically operate with constraints on processing power,
memory, and energy (battery power). Memory limits the number of
routing states an LR and BR can maintain. When the routing table of
an LR or BR is full, it will either reject the new DAO messages
received or will use some replacement policy to remove a routing
entry and add the new one. Rejection of DAO messages will lead to an
increase in DAO message transmission that impacts the energy and
network convergence time. Routing state replacement leads to
downward path downtime.
One possible way to solve problems due to routing table size
constraint is to use this information to add neighbors to the DAO
parent set. Routing resource capability can be used by LR and BR to
advertise their current routing table usage details in the network.
LR or LNs in LLN can use this information in the selection of the DAO
parent set. PCE can use this information to select intermediate
routers for the projected routes. Routing Resource is an optional
capability.
Routing resource capabablity sent in DIO message has link local scope
and it MUST not be forwarded. The 'C' bit of this capability MUST be
set to 0.
6.2.1. Format of Routing Resource Capability
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CapType=0x02 | Len=3 |J|I|C| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Total Capacity |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Routing Resource Capability TLV
Type: 0x02.
Flags: I bit MUST be set to 0. C bit MUST be set to 0.
Len: 8-bit unsigned integer, representing the length in octets of the
option, not including the Option Type and Length/flags fields.
Resvd: 8-bit unused field. It MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
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Total Capacity: 16 bit unsigned integer representing the routing
table size.
7. Acknowledgements
Thanks to Georgios Papadopoulos, Li Zhao for early review and
feedback.
8. IANA Considerations
IANA is requested to allocate new codes for the CAPQ and CAPS
messages from the RPL Control Codes registry.
+======+============================+===============+
| Code | Description | Reference |
+======+============================+===============+
| TBD1 | Capability Query | This document |
+------+----------------------------+---------------+
| TBD2 | Capability Response | This document |
+------+----------------------------+---------------+
| TBD3 | Secure Capability Query | This document |
+------+----------------------------+---------------+
| TBD4 | Secure Capability Response | This document |
+------+----------------------------+---------------+
Table 1: New RPL Control Messages
The MSB of the codes allocated to "Secure" messages above should be
set.
8.1. New option: Capabilities
New entry is required for supporting new Capabilities option and new
Capability Type List Option in the "RPL Control Message Options"
space [RFC6550].
+=======+=============================+===============+
| Value | Meaning | Reference |
+=======+=============================+===============+
| TODO | Capability Option | This document |
+-------+-----------------------------+---------------+
| TODO | Capability Type List Option | This document |
+-------+-----------------------------+---------------+
Table 2: New options
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8.2. Capability Sub-Type
IANA is requested to create a registry for the Capabilities Type as
described in Figure 2 of this document. This registry should be
located in TODO. New Capabilities types may be allocated only by an
IETF review.
+=======+=============================+===============+
| Value | Meaning | Reference |
+=======+=============================+===============+
| 0x01 | Capability Indicators | This document |
+-------+-----------------------------+---------------+
| 0x02 | Routing Resource Capability | This document |
+-------+-----------------------------+---------------+
Table 3: Type
8.3. New Registry for CAPQ Flags
IANA is requested to create a registry for the Capabilities flags as
described in Section 4.1 of this document. This registry should be
located in TODO. New Capabilities flags may be allocated only by an
IETF review. Currently no flags are defined by this document. Each
value is tracked with the following qualities:
* Flag
* Description
* Defining RFC
8.4. New Registry for Capabilities Flags
IANA is requested to create a registry for the Capabilities flags as
described in Section 2.1 of this document. This registry should be
located in TODO. New Capabilities flags may be allocated only by an
IETF review. Currently no flags are defined by this document. Each
value is tracked with the following qualities:
* Flag
* Description
* Defining RFC
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8.5. New Registry for Capabilities Indicators
IANA is requested to create a registry for the Capabilities
Indicators as described in Section 6.1 of this document. This
registry should be located in TODO. New Capabilities indicators may
be allocated only by an IETF review. Each value is tracked with the
following qualities:
* Flag
* Description
* Defining RFC
9. Security Considerations
The options defined in this document are carried in the base message
objects as defined in [RFC6550]. The RPL control message options are
protected by the same security mechanisms that protect the base
messages.
Capabilities flag can reveal that the node has been upgraded or is
running a old feature set. This document assumes that the base
messages that carry these options are protected by RPL security
mechanisms and thus are not visible to a malicious node.
[TODO] implications of malicious attack involving setting the
capability flags.
10. References
10.1. Normative References
[I-D.ietf-roll-mopex]
Jadhav, R. A., Thubert, P., and M. Richardson, "Mode of
Operation extension", Work in Progress, Internet-Draft,
draft-ietf-roll-mopex-03, 31 March 2021,
<https://www.ietf.org/archive/id/draft-ietf-roll-mopex-
03.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
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Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>.
10.2. Informative References
[I-D.ietf-lwig-nbr-mgmt-policy]
Jadhav, R. A., Sahoo, R. N., Duquennoy, S., and J.
Eriksson, "Neighbor Management Policy for 6LoWPAN", Work
in Progress, Internet-Draft, draft-ietf-lwig-nbr-mgmt-
policy-03, 21 February 2019,
<https://www.ietf.org/archive/id/draft-ietf-lwig-nbr-mgmt-
policy-03.txt>.
[I-D.ietf-roll-dao-projection]
Thubert, P., Jadhav, R. A., and M. Gillmore, "Root
initiated routing state in RPL", Work in Progress,
Internet-Draft, draft-ietf-roll-dao-projection-21, 27
September 2021, <https://www.ietf.org/archive/id/draft-
ietf-roll-dao-projection-21.txt>.
[I-D.thubert-roll-turnon-rfc8138]
Thubert, P. and L. Zhao, "Configuration option for RFC
8138", Work in Progress, Internet-Draft, draft-thubert-
roll-turnon-rfc8138-03, 8 July 2019, <http://www.ietf.org/
internet-drafts/draft-thubert-roll-turnon-rfc8138-03.txt>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6551>.
Appendix A. Capability Handshake Example
A.1. Query supported Cap Types
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Root 6LR/6LN
| |
| CAPQ(seq=1, opts=nil) |
|---------------------------------->|
| |
| |
| CAPS(seq=1, opts={CapTypeList}) |
|<----------------------------------|
| |
Figure 8: Query supported Cap Types
CAPQ message with no CapTypeList Option results in the peer
responding with a CAPS message with CapTypeList Option indicating all
the capability set it supports.
A.2. Query specific Cap Set
Root 6LR/6LN
| |
| CAPQ(seq=2, |
| opts={CapTypeList=[Cap1, Cap2]})|
|---------------------------------->|
| |
| |
| CAPS(seq=2, |
| opts={Cap1=Cap1Value, |
| Cap2=Cap2Value}) |
|<----------------------------------|
| |
Figure 9: Query specific Cap Set
This flow indicates the case where the Root probes for specific
Capabilities of the peer node and the peer node responds with the
value of indicated Capability set.
A.3. CAPS with partial Cap Set
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Root 6LR/6LN
| |
| CAPQ(seq=3, |
| opts={CapTypeList=[Cap1, Cap2, |
| Cap3, Cap4]})|
|---------------------------------->|
| |
| |
| CAPS(seq=3, |
| opts={Cap2=Cap2Value, |
| Cap3=Cap3Value, |
| CapTypeList=[Cap1,Cap4]})|
|<----------------------------------|
| |
Figure 10: Partial Capability Set handshake
Assume that Root queries for capabilities {Cap1, Cap2, Cap3, Cap4}
from the peer node. However the peer node does not support or does
not understand capability {cap1, cap4}. In this case the peer node
will respond back with value of Cap2 and Cap3 (which it understands)
and set the CapTypeList option with {Cap1, Cap4} type.
Authors' Addresses
Rahul Arvind Jadhav (editor)
Huawei
Kundalahalli Village, Whitefield,
Bangalore 560037
Karnataka
India
Phone: +91-080-49160700
Email: rahul.ietf@gmail.com
Pascal Thubert
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
06254 MOUGINS - Sophia Antipolis
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
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Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
Rabi Narayan Sahoo
Juniper
Email: rabinarayans0828@gmail.com
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