Network Working Group B. Cheng
Internet-Draft D. Wiggins
Intended status: Standards Track Lincoln Laboratory
Expires: May 3, 2018 L. Berger, Ed.
LabN Consulting, L.L.C.
October 30, 2017
DLEP Control Plane Based Pause Extension
draft-ietf-manet-dlep-pause-extension-02
Abstract
This document defines an extension to the DLEP protocol 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.
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This Internet-Draft will expire on May 3, 2018.
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document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. Extension Type Value . . . . . . . . . . . . . . . . . . 9
5.2. Data Item Values . . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The Dynamic Link Event 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-credit-window]. 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, see [RFC2475], flow control. The extension defined in this
document is referred to as "Control Plane Based Pause". Note that
this mechanism only controls 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 Control Plane Based Pause
Extension is to be used, 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 on 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 identifies DSCPs based on groups of
logical queues, each of which is referred to via 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Queue Size Q0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 KB - Kilobytes (B/1024)
2 MB - Megabytes (KB/1024)
3 GB - Gigabytes (MB/1024)
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Reserved:
MUST be set to zero by the sender (a modem) and ignored by the
receiver (a router).
Queue Size Q0:
A 24-bit unsigned integer representing the size, in the octet
scale indicated by the Scale field, of queue index zero.
3.1.1. Queue Parameter Sub Data Item
Queue Parameter Sub Data Items are an ordered list composed of sub
data items with a common format. The first sub data item is assigned
a Queue Index value of 1, and subsequent data items are numbered
incrementally. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must be one (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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num DSCPs Qn | Queue Size Qn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DS Field Qn | DS Field Qn | ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: ... | DS Field Qn |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length: Variable
Copying [RFC8175], Length is the number of octets in the sub data
item, excluding the Type and Length fields.
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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).
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.
DS Field Qn:
The data item contains a sequence of 8 bit DS Fields. The
position in the sequence identifies the associated queue index.
The number of DS Fields present should 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. An example of when a modem might send
this data item is when an internal queue length exceeds a particular
threshold.
A modem may 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 MAY send the Pause Data Item in a Session
Update Message. To indicate that suppression applies to a particular
destination a modem MAY 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
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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 0, 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:
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 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
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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. This includes that to
indicate that transmission can resume to all destinations, a modem
MAY 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 MAY send the Pause Restart Item in a
Destination Update Message. Finally, the same rules apply to queue
indexes.
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.
4. Security Considerations
The extension introduces a new mechanism for flow control between a
router and modem using the DLEP protocol. The extension does not
inherently introduce any additional threats above those documented in
[RFC8175]. The approach taken to Security in that document applies
equally when running the extension defined in this document.
5. IANA Considerations
This document requests the assignment of 4 values by IANA. All
assignments are to registries defined by [RFC8175].
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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 Values" in the range with the
"Specification Required" policy. The requested values are as
follows:
+-----------+------------------+
| Type Code | Description |
+-----------+------------------+
| TBA2 | Queue Parameters |
| | |
| TBA3 | Pause |
| | |
| TBA4 | Restart |
+-----------+------------------+
Table 2: Requested Data Item 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>.
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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-credit-window]
Ratliff, S., "Credit Windowing extension for DLEP", draft-
ietf-manet-credit-window-07 (work in progress), November
2016.
[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>.
Appendix A. Acknowledgments
The sub data item format was inspired by Rick Taylor's "Data Item
Containers".
Authors' Addresses
Bow-Nan Cheng
Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02421-6426
Email: bcheng@ll.mit.edu
David Wiggins
Lincoln Laboratory
Massachusetts Institute of Technology
244 Wood Street
Lexington, MA 02420-9108
Email: David.Wiggins@ll.mit.edu
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Lou Berger (editor)
LabN Consulting, L.L.C.
Email: lberger@labn.net
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