Internet DRAFT - draft-ietf-manet-dlep-multi-hop-extension
draft-ietf-manet-dlep-multi-hop-extension
Network Working Group B. Cheng
Internet-Draft MIT Lincoln Laboratory
Intended status: Standards Track L. Berger, Ed.
Expires: November 6, 2019 LabN Consulting, L.L.C.
May 5, 2019
Dynamic Link Exchange Protocol (DLEP) Multi-Hop Forwarding Extension
draft-ietf-manet-dlep-multi-hop-extension-07
Abstract
This document defines an extension to the Dynamic Link Exchange
Protocol (DLEP) that enables the reporting and control of Multi-Hop
Forwarding by DLEP capable modems.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 6, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Cheng & Berger Expires November 6, 2019 [Page 1]
Internet-Draft DLEP Multi-Hop Extension May 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extension Usage and Identification . . . . . . . . . . . . . 3
3. Extension Data Items . . . . . . . . . . . . . . . . . . . . 3
3.1. Hop Count . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Hop Control . . . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Reset . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2. Terminate . . . . . . . . . . . . . . . . . . . . . . 7
3.2.3. Direct Connection . . . . . . . . . . . . . . . . . . 7
3.2.4. Suppress Forwarding . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 8
5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 9
5.3. Hop Control Actions Registry . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The Dynamic Link Exchange Protocol (DLEP) is defined in [RFC8175].
It provides the exchange of link related control information between
a modem and a router. DLEP defines a base set of mechanisms as well
as support for possible extensions. This document defines one such
extension.
Some modem technologies support mobile ad hoc network (MANET)
forwarding where connectivity to destinations is provided via
forwarding in intermediate modems. This document refers to
forwarding by intermediate modems as 'multi-hop forwarding'. DLEP
Destination messages can be used to report such reachable
destinations, see [RFC8175], but do not provide any information
related to the number or capacity of the hops. The extension defined
in this document enables modems to inform routers when multi-hop
forwarding is being used, and routers to request that modems change
multi-hop forwarding behavior. The extension defined in this
document is referred to as "Multi-Hop Forwarding", where each modem
that transmits/sends data to reach a particular destination is
counted as a hop.
It is important to note that the use of the hop control mechanism
defined in this document can result in connectivity changes and even
loss of the ability to reach one or more destinations. The defined
Cheng & Berger Expires November 6, 2019 [Page 2]
Internet-Draft DLEP Multi-Hop Extension May 2019
mechanism will report such connectivity changes, but the details of
what a router does or how it reacts to such are out scope of this
document.
This document defines a new DLEP Extension Type Value in Section 2
which is used to indicate the use of the extension, and three new
DLEP Data Items in Section 3.
1.1. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Extension Usage and Identification
The use of the Multi-Hop Forwarding Extension SHOULD be configurable.
Per [RFC8175], to indicate that the extension is to be used, an
implementation includes the Multi-Hop Forwarding Extension Type Value
in the Extensions Supported Data Item. The Extensions Supported Data
Item is sent and processed according to [RFC8175].
The Multi-Hop Forwarding Extension Type Value is TBA1, see Section 5.
3. Extension Data Items
Three data items are defined by this extension. The Hop Count Data
Item is used by a modem to provide the number of modem hops traversed
to reach a particular destination. The Hop Control Data Item is used
by a router to request that a modem alter connectivity to a
particular destination. The Suppress Forwarding Data Item is used by
a router to request that a modem disable multi-hop forwarding on
either a device or destination basis.
3.1. Hop Count
The Hop Count Data Item is used by a modem to indicate the number of
modems that transmit/send data to reach a particular destination,
i.e., hops, between the modem and a specific destination. In other
words, each hop represents a transmission and the number of hops is
equal to the number of transmissions required to go from a router
connected modem to the destination's connected modem. The minimum
number of hops is 1, which represents transmission to destinations
that are directly reachable via the router's locally connected modem.
Cheng & Berger Expires November 6, 2019 [Page 3]
Internet-Draft DLEP Multi-Hop Extension May 2019
The data item also contains an indication of when a destination which
currently has a hop count of greater than one (1) could be made
directly reachable by a modem, e.g., by re-aiming an antenna.
The Hop Count Data Item SHOULD be carried in the Destination Up,
Destination Update, Destination Announce Response, and Link
Characteristics Response Messages when the Hop Count to a destination
is greater than one (1).
A router receiving a Hop Count Data Item can use this information in
its forwarding and routing decisions, and specific use is out of
scope of this document. When using this extension, the absence of
the Hop Count Data Item MUST be interpreted by the router as a Hop
Count value of one (1).
The format of the Hop Count Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P| Reserved | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA2
Length: 2
P:
The P-bit indicates that a destination is potentially directly
reachable. When the P-bit is set, the router MAY request a direct
link to the associated destination using the Hop Control Data Item
described below. This field MUST be ignored when the value
contained in the Hop Count field is one (1).
Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
Hop Count:
An unsigned 8-bit integer indicating the number of modem hops
required (i.e., number of times a packet will be transmitted) to
reach the destination indicated in the message. The special value
of 255 (0xFF) is used to indicate that the number of hops is an
Cheng & Berger Expires November 6, 2019 [Page 4]
Internet-Draft DLEP Multi-Hop Extension May 2019
unknown number greater than one (1). This field MUST contain a
value of at least one (1) if the associated destination is
reachable.
A value of zero (0) is used to indicate that processing of a Hop
Control action, see Section 3.2, has resulted in the destination
no longer being reachable. A zero value MUST NOT be used in any
message other than a Link Characteristics Response Message.
3.2. Hop Control
The Hop Control Data Item is used by a router to request a change in
connectivity to a particular destination, or in multi-hop processing
on a device wide basis. A router can request that a multi-hop
reachable destination be changed to a single hop. A router can also
indicate that the modem terminates a previous direct connectivity
request to a particular destination.
The Hop Control Data Item MAY be carried in a Session Update Message
sent by a router when the control applies to the whole device, or a
Link Characteristics Request Message when the control applies to a
particular destination.
A modem that receives the Hop Control Data Item in a Link
Characteristics Request Message SHOULD take whatever actions are
needed to make the change indicated by the data item for the
associated destination MAC address. Once the change is made, fails
or is rejected, the modem MUST respond with a Link Characteristics
Response Message containing an updated Hop Count Data Item. Note
that other destinations can be impacted as a result of the change and
such changes are reported in Destination Down and Destination Update
Messages. The modem MUST notify the router of each destination that
is not identified in the Link Characteristics Response Message and is
no longer reachable via a Destination Down Message. The modem MUST
also notify the router of each impacted destination that is not
identified in the Link Characteristics Response Message via a
Destination Update Message.
Failures may occur for multiple reasons, for example, the
transmission characteristics of the link don't support the one-hop
connection at the time of the request. Requests can be rejected by
local policy.
A modem that receives the Hop Control Data Item in a Session Update
Message SHOULD take whatever actions are needed to make the change
indicated by the data item for all known destinations. Once the
change is made, or fails or is rejected, the modem MUST respond with
a Session Update Response Message with an appropriate Status Code.
Cheng & Berger Expires November 6, 2019 [Page 5]
Internet-Draft DLEP Multi-Hop Extension May 2019
Destination specific impact resulting from the processing of a Hop
Control Data Item in a Session Update Message is provided via
Destination Down and Destination Update Messages. The modem MUST
notify the router of each destination that is no longer reachable via
a Destination Down Message. The modem MUST notify the router of any
changes in Hop Counts via Destination Update Messages.
The format of the Hop Control Data Item is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Item Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Control Actions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA3
Length: 2
Hop Control Actions:
An unsigned 16-bit value with the following meaning:
+-------+---------------------+
| Value | Action |
+-------+---------------------+
| 0 | Reset |
| | |
| 1 | Terminate |
| | |
| 2 | Direct Connection |
| | |
| 3 | Suppress Forwarding |
+-------+---------------------+
Table 1: Hop Control Actions Values
3.2.1. Reset
The Reset Action requests that the default behavior be restored.
When received in a Session Update Message message, a modem MUST clear
all control actions that have previously been processed on a device
wide basis, and revert to its configured behavior. When received in
a Link Characteristics Request Message, a modem MUST clear all
control actions that have previously been processed for the
destination indicated in the message.
Cheng & Berger Expires November 6, 2019 [Page 6]
Internet-Draft DLEP Multi-Hop Extension May 2019
3.2.2. Terminate
The Terminate Action is only valid on a per destination basis and
MUST NOT be sent in a Session Update Message message. It indicates
that a direct connection is no longer needed with the destination
identified in the message. This request has no impact for multi-hop
destinations and may fail even in a single hop case, i.e. can result
in the Hop Count to the destination not being impacted by the
processing of the request.
3.2.3. Direct Connection
The Direct Connection Action is only valid on a per destination basis
and MUST NOT be sent in a Session Update Message message. It
indicates that the modem SHOULD attempt to establish a direct
connection with the destination identified in the message. This
action SHOULD only be sent for destinations for which the Hop Count
is greater than 1 and has the P-Bit set in the previously received
Hop Count Data Item. Results of the request for the destination
identified in the message are provided as described above.
3.2.4. Suppress Forwarding
The Suppress Forwarding Action is used by a router to indicate to its
peer that multi-hop forwarding performed by the modem is to be
suppressed. A router can request that multi-hop forwarding may be
suppressed on a device wide or destination specific basis.
A modem that receives the Suppress Forwarding Data Item in a Session
Update Message MUST suppress multi-hop forwarding on a device wide
basis. This means that data traffic originating from the modem's
peer router SHALL only be sent by the modem to destinations that are
one modem hop away, and that any data traffic received by the modem
from another modem that is not destined to the peer router SHALL be
dropped. Impact to destination hop counts are provided to the router
by the modem as described above.
A modem that receives the Suppress Forwarding Data Item in a Link
Characteristics Request Message MUST suppress multi-hop forwarding
for only the destination indicated in the message. This means that
data traffic originating from the modem's peer router SHALL be sent
by the modem to the destination indicated in the Link Characteristics
Request Message only when it is one modem hop away. Notably, data
traffic received by the modem from another modem can be forwarded by
the modem per its normal processing. Results are provided as
described above.
Cheng & Berger Expires November 6, 2019 [Page 7]
Internet-Draft DLEP Multi-Hop Extension May 2019
4. Security Considerations
The extension enables the reporting and control of forwarding
information by DLEP capable modems. The extension does not
inherently introduce any additional vulnerabilities above those
documented in [RFC8175]. The approach taken to Security in that
document applies equally when running the extension defined in this
document.
This extension does define one mechanism that is worth particular
note. This extension includes a Hop Control mechanism, see
Section 3.2, that is similar to the Link Characteristics Request
Message defined in [RFC8175] in that it can impact the set of
destinations reported as reachable. With the Link Characteristics
Request Message, this risk is implicit. With the Hop Control
mechanism defined in this document it is more likely. From a
security perspective, implementations should be aware of this
increased risk and may choose to implement additional configuration
control mechanisms to ensure that the Hop Control mechanism is only
used under conditions intended by the network operator.
Implementations of the extension defined in this document MUST
support configuration of TLS usage, as describe in [RFC8175], in
order to protect configurations where injection attacks are possible,
i.e., when the link between a modem and router is not otherwise
protected.
Note that this extension does allow a compromised or impersonating
modem to suppress transmission by the router or a switch that
interconnects the modem and router. Similar attacks are generally
possible base DLEP, for example an impersonating modem may cause a
session reset or a compromised modem simply can drop all traffic
destined to, or sent by a router. [RFC8175] defines the use of TLS
to protect against the impersonating attacker.
5. IANA Considerations
This document requests the assignment of 3 values by IANA. All
assignments are to registries defined by [RFC8175]. It also requests
creation of one new registry.
5.1. Extension Type Value
This document requests 1 new assignment to the DLEP Extensions
Registry named "Extension Type Values" in the range with the
"Specification Required" policy. The requested value is as follows:
Cheng & Berger Expires November 6, 2019 [Page 8]
Internet-Draft DLEP Multi-Hop Extension May 2019
+------+----------------------+
| Code | Description |
+------+----------------------+
| TBA1 | Multi-Hop Forwarding |
+------+----------------------+
Table 2: Requested Extension Type Value
5.2. Data Item Values
This document requests 2 new assignments to the DLEP Data Item
Registry named "Data Item Type Values" in the range with the
"Specification Required" policy. The requested values are as
follows:
+-----------+-------------+
| Type Code | Description |
+-----------+-------------+
| TBA2 | Hop Count |
| | |
| TBA3 | Hop Control |
+-----------+-------------+
Table 3: Requested Data Item Values
5.3. Hop Control Actions Registry
Upon approval of this document, IANA is requested to create a new
DLEP registry, named "Hop Control Actions Values". The following
table provides initial registry values and the [RFC8126] defined
policies that should apply to the registry:
Cheng & Berger Expires November 6, 2019 [Page 9]
Internet-Draft DLEP Multi-Hop Extension May 2019
+-------------+------------------------+
| Value | Action/Policy |
+-------------+------------------------+
| 0 | Reset |
| | |
| 1 | Terminate |
| | |
| 2 | Direct Connection |
| | |
| 3 | Suppress Forwarding |
| | |
| 4-65519 | Specification Required |
| | |
| 65520-65534 | Private Use |
| | |
| 65535 | Reserved |
+-------------+------------------------+
Table 4: Hop Control Actions Values
6. References
6.1. Normative References
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B.
Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175,
DOI 10.17487/RFC8175, June 2017,
<https://www.rfc-editor.org/info/rfc8175>.
6.2. Informative References
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Acknowledgments
Cheng & Berger Expires November 6, 2019 [Page 10]
Internet-Draft DLEP Multi-Hop Extension May 2019
Helpful comments were received from members of the MANET working
grouping, including Henning Rogge, Victoria Pritchard and David
Wiggins.
Authors' Addresses
Bow-Nan Cheng
MIT Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02421-6426
Email: bcheng@ll.mit.edu
Lou Berger (editor)
LabN Consulting, L.L.C.
Email: lberger@labn.net
Cheng & Berger Expires November 6, 2019 [Page 11]
