Network Working Group B. Cheng
Internet-Draft D. Wiggins
Intended status: Standards Track MIT Lincoln Laboratory
Expires: October 5, 2019 L. Berger, Ed.
LabN Consulting, L.L.C.
April 3, 2019
DLEP Control Plane Based Pause Extension
draft-ietf-manet-dlep-pause-extension-06
Abstract
This document defines an extension to the Dynamic Link Exchange
Protocol (DLEP) that enables a modem to use DLEP messages to pause
and resume data traffic coming from its peer router.
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
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 5, 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extension Usage and Identification . . . . . . . . . . . . . 3
3. Extension Data Items . . . . . . . . . . . . . . . . . . . . 3
3.1. Queue Parameters . . . . . . . . . . . . . . . . . . . . 3
3.1.1. Queue Parameter Sub Data Item . . . . . . . . . . . . 5
3.2. Pause . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Restart . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 9
5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 9
5.3. Queue Parameters Sub Data Item Values . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 11
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
DLEP peers. DLEP peers are comprised of 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.
The base DLEP specification does not include any data plane flow
control capability. Various flow control methods are possible, e.g.,
see [I-D.ietf-manet-dlep-da-credit-extension]. The extension defined
in this document supports flow control of data traffic based on
explicit messages sent via DLEP by a modem to indicate when a router
should hold off sending traffic, and when it should resume. The
extension also optionally supports DSCP (differentiated services
codepoint) aware flow control. For general background on
Differentiated Services see [RFC2475]. The extension defined in this
document is referred to as "Control Plane Based Pause". Note that
this mechanism only applies to traffic that is to be transmitted on
the modem's attached data channel and not to DLEP control messages
themselves.
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.
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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 Control Plane Based Pause Extension SHOULD be
configurable. To indicate that the implementation supports use of
the Control Plane Based Pause Extension, an implementation MUST
include the Control Plane Based Pause Extension Type Value in the
Extensions Supported Data Item. The Extensions Supported Data Item
is sent and processed according to [RFC8175].
The Control Plane Based Pause Extension Type Value is TBA1, see
Section 5.
3. Extension Data Items
Three data items are defined by this extension. The Queue Parameters
Data Item is used by a modem to provide information about the DSCPs
it uses in forwarding. The Pause Data Item is used by a modem to
indicate when a router should cease sending packets and the Restart
Data Item is used by a modem to indicate when a router can resume
sending packets.
3.1. Queue Parameters
The Queue Parameters Data Item is used by a modem to indicate DSCP
values that may be independently paused. This data item MUST be
included in a Session Initialization Response Message that also
contains the Control Plane Based Pause Extension Type Value in the
Extensions Supported Data Item. Updates to these parameters MAY be
sent by a modem by including the data item in Session Update
Messages.
The Queue Parameters Data Item groups DSCPs into logical queues, each
of which is identified by a "Queue Index". The number of logical
queues, or queue indexes, is variable as is the number of DSCPs
associated with each queue. A queue size (in bytes) is provided for
informational purposes. Queue Indexes are numbered sequentially from
zero, where queue index zero is a special case covering DSCPs which
are not otherwise associated with Queue Index.
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An implementation that does not support DSCPs would indicate 1 queue
with 0 DSCPs, and the number of bytes that may be in its associated
link transmit queue. Additional logical queues are represented in a
variable series of Queue Parameter sub data items.
The format of the Queue Parameters 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num Queues | Scale | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Parameter Sub Data Item 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Parameter Sub Data Item n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA2
Length: Variable
Per [RFC8175] Length is the number of octets in the data item,
excluding the Type and Length fields.
Num Queues:
An 8-bit unsigned integer indicating the number of queues
represented in the data item. This field MUST contain a value of
at least one (1), and is equal to one greater than the number of
included Queue Parameter Sub Data Items.
Scale:
An 4-bit unsigned integer indicating the scale used in the Queue
Size fields. The valid values are:
Value Scale
------------
0 B - Bytes (Octets)
1 KiB - Kilobytes (1024 B)
2 MiB - Megabytes (1024 KiB)
3 GiB - Gigabytes (1024 MiB)
Reserved:
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MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
3.1.1. Queue Parameter Sub Data Item
Queue Parameter Sub Data Items are an unordered list composed of sub
data items with a common format. The format of the Queue Parameter
Sub Data Item is patterned after the standard DLEP data item format,
see [RFC8175] Section 11.3. Any errors or inconsistencies
encountered in parsing Sub Data Items are handled in the same fashion
as any other Data Item parsing error encountered in DLEP.
The format of the Queue Parameter Sub 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub Data Item Type (1) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
and Value has the format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Index | Queue Size Qn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num DSCPs Qn | DS Field Qn | ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... | DS Field Qn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub Data Item Type:
A 16-bit unsigned integer that indicates the type and
corresponding format of the Sub Data Item's Value field. Sub Data
Item Types are scoped within the Data Item in which they are
carried, i.e., the Sub Data Item Type field MUST be used together
with the Queue Parameters Data Item Type to identify the format of
the Sub Data Item. This field MUST be set to one (1) for the
Queue Parameter Sub Data Item.
Length: Variable
Length is the number of octets in the sub data item, excluding the
Type and Length fields.
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Queue Index:
An 8-bit field indicating the queue index of the queue parameter
represented in the sub data item. Only the first instance of a
particular Queue Index value is meaningful. Subsequent sub data
items containing the same Queue Index values, if present, MAY be
logged via a management interface and MUST otherwise be ignored.
Note that the value 255 is reserved and MUST NOT be used in this
field.
Queue Size Qn:
A 24-bit unsigned integer representing the size, in the octet
scale indicated by the Scale field, of the queue supporting
traffic with the DSCPs associated with the queue index.
Num DSCPs Qn:
An 8-bit unsigned integer indicating the number of DSCPs
associated with the queue index associated with the sub data item.
This field MUST contain a value of at least one (1).
DS Field Qn:
The data item contains a sequence of 8 bit DS Fields. The number
of DS Fields present MUST equal the sum of all Num DSCPs field
values.
The DS Field structure is the same as [RFC2474].
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| DSCP | CU |
+---+---+---+---+---+---+---+---+
DSCP: differentiated services codepoint
CU: currently unused, MUST be zero
3.2. Pause
The Pause Data Item is used by a modem to indicate to its peer that
traffic is to be suppressed. The motivating use case is for this
data item is when a modem's internal queue length exceeds a
particular threshold. Other use cases are possible, e.g., when there
a non queue related congestion points within a modem, but such are
not explicitly described in this document.
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A modem can indicate that traffic is to be suppressed on a device-
wide or destination-specific basis. An example of when a modem might
use device wide indications is when output queues are shared across
all destinations, and destination specific might be used when per
destination queuing is used. To indicate that suppression applies to
all destinations, a modem MUST send the Pause Data Item in a Session
Update Message. To indicate that suppression applies to a particular
destination a modem MUST send the Pause Data Item in a Destination
Update Message.
Each Pause Data Item identifies the traffic to be suppressed by the
Queue Index defined by Section 3.1, which in turn indicates a set of
traffic identified by DSCPs. The special value of 255 is used to
indicate that all traffic is to be suppressed.
While there is no restriction on the number of Messages containing
Pause Data Item that may be sent by a modem, a modem SHOULD include
multiple queue indexes in the same message when possible.
A router which receives the Pause Data Item MUST cease sending the
identified traffic to the modem. This may of course translate into
the router's queues exceeding their own thresholds. If a received
Pause Data Item contains a Queue Index value other than 255, or a
queue index established by a Session Initialization or Session Update
Message, the router MUST terminate the session with a Status Data
Item indicating Invalid Data.
The format of the Pause 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Index | ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... | Queue Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA3
Length: Variable
Per [RFC8175] Length is the number of octets in the data item,
excluding the Type and Length fields. It will equal the number of
Queue Index fields carried in the data item.
Queue Index:
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One or more 8-bit fields used to indicate a queue index defined by
a Queue Parameters Data Item. The special value of 255 indicates
all traffic is to be suppressed to the modem, when the data item
is carried in a Session Update Message, or is to be suppressed to
a destination, when the data item is carried in Destination Update
Message.
3.3. Restart
The Restart Data Item is used by a modem to indicate to its peer that
transmission of previously suppressed traffic may be resumed. An
example of when a modem might send this data item is when an internal
queue length drops below a particular threshold.
The sending of this data item parallels the Pause Data Item, see the
previous section, and follows the same rules. As above, to indicate
that transmission can resume to all destinations, a modem MUST send
the Restart Data Item in a Session Update Message. It also includes
that to indicate that transmission can resume to a particular
destination a modem MUST send the Pause Restart Item in a Destination
Update Message. Finally, queue indexes are interpreted in the same
way as in the Pause Data Item..
A router which receives the Restart Data Item SHOULD resume
transmission of the identified traffic to the modem.
The format of the Restart Data Item matches the Pause Data Item and
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Index | ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... | Queue Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Data Item Type: TBA4
Length: See Section 3.2.
Queue Index: See Section 3.2.
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4. Security Considerations
The extension introduces a new mechanism for flow control between a
router and modem using DLEP. 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.
Note that this extension does allow a compromised or impersonating
modem to suppress transmission by the router, but this is not a
substantively different attack by such a compromised modem simply
dropping 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 4 values by IANA. All
assignments are to registries defined by [RFC8175].
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:
+------+---------------------------+
| Code | Description |
+------+---------------------------+
| TBA1 | Control Plane Based Pause |
+------+---------------------------+
Table 1: Requested Extension Type Value
5.2. Data Item Values
This document requests 3 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:
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+-----------+------------------+
| Type Code | Description |
+-----------+------------------+
| TBA2 | Queue Parameters |
| | |
| TBA3 | Pause |
| | |
| TBA4 | Restart |
+-----------+------------------+
Table 2: Requested Data Item Values
5.3. Queue Parameters Sub Data Item Values
Upon approval of this document, IANA is requested to create a new
DLEP registry, named "Queue Parameters Sub Data Item Type Values".
The following table provides initial registry values and the
[RFC8126] defined policies that should apply to the registry:
+-------------+------------------------+
| Type Code | Description/Policy |
+-------------+------------------------+
| 0 | Reserved |
| | |
| 1 | Queue Parameter |
| | |
| 2-65407 | Specification Required |
| | |
| 65408-65534 | Private Use |
| | |
| 65535 | Reserved |
+-------------+------------------------+
Table 3
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>.
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[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
[I-D.ietf-manet-dlep-da-credit-extension]
Cheng, B., Wiggins, D., and L. Berger, "DLEP DiffServ
Aware Credit Window Extension", draft-ietf-manet-dlep-da-
credit-extension-07 (work in progress), March 2019.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[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
The sub data item format was inspired by Rick Taylor's "Data Item
Containers" idea.
Authors' Addresses
Bow-Nan Cheng
MIT Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02421-6426
Email: bcheng@ll.mit.edu
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David Wiggins
MIT Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02420-9108
Email: David.Wiggins@ll.mit.edu
Lou Berger (editor)
LabN Consulting, L.L.C.
Email: lberger@labn.net
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