Internet Engineering Task Force (IETF) L. Bertz
Request for Comments: 7660 S. Manning
Category: Standards Track Sprint
ISSN: 2070-1721 B. Hirschman
October 2015
Diameter Congestion and Filter Attributes
Abstract
This document defines optional Diameter attributes that can be used
to help manage networks that use Explicit Congestion Notification
(ECN) or Diameter traffic filters. These new attributes allow for
improved data traffic identification, support of ECN, and minimal
Diameter filter administration.
RFC 5777 defines a Filter-Rule Attribute Value Pair (AVP) that
accommodates extensions for classification, conditions, and actions.
It, however, does not support traffic identification for packets
using Explicit Congestion Notification as defined in RFC 3168 and
does not provide specific actions when the flow(s) described by the
Filter-Rule are congested.
Further, a Filter-Rule can describe multiple flows but not the exact
number of flows. Flow count and other associated data (e.g.,
packets) are not captured by accounting applications, leaving
administrators without useful information regarding the effectiveness
or appropriateness of the filter definition.
The optional attributes defined in this document are forward and
backwards compatible with RFC 5777.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7660.
Bertz Standards Track [Page 1]RFC 7660 Congestion and Filter Attributes October 2015
Copyright Notice
Copyright (c) 2015 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. ECN-IP-Codepoint, Congestion-Treatment and Filter Attributes . 4
3.1. ECN-IP-Codepoint AVP . . . . . . . . . . . . . . . . . . . 4
3.2. Congestion-Treatment AVP . . . . . . . . . . . . . . . . . 4
3.3. Flow-Count AVP . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Packet-Count AVP . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Classifier Example . . . . . . . . . . . . . . . . . . . . 6
5.2. Diameter Credit Control (CC) with Congestion Information . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Two optional AVPs related to Explicit Congestion Notification (ECN)
[RFC3168] are specified in this document. The first AVP provides
direct support for filtering ECN-marked traffic [RFC3168] and the
second AVP provides the ability to define alternate traffic treatment
when congestion is experienced.
This document also defines two optional AVPs, Flow-Count and Packet-
Count, used for conveying flow information within the Diameter
protocol [RFC6733]. These AVPs were found to be useful for a wide
range of applications. The AVPs provide a way to convey information
of the group of flows described by the Filter-Rule, IPFilterRule, or
other Diameter traffic filters.
The semantics and encoding of all AVPs can be found in Section 3.
Such AVPs are, for example, needed by some congestion-management
functions to determine the number of flows congested or used by
administrators to determine the impact of filter definitions.
Additional parameters may be defined in future documents as the need
arises. All parameters are defined as Diameter-encoded Attribute
Value Pairs (AVPs), which are described using a modified version of
the Augmented Backus-Naur Form (ABNF), see [RFC6733]. The data types
are also taken from [RFC6733].
2. 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 RFC2119 [RFC2119].
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RFC 7660 Congestion and Filter Attributes October 2015
3. ECN-IP-Codepoint, Congestion-Treatment, and Filter Attributes
3.1. ECN-IP-Codepoint AVP
The ECN-IP-Codepoint AVP (AVP Code 628) is of type Enumerated and
specifies the ECN codepoint values to match in the IP header.
Value | Binary | Keyword | References
-----------------------------------------------------------------
0 | 00 | Not-ECT (Not ECN-Capable Transport)| [RFC3168]
1 | 01 | ECT(1) (ECN-Capable Transport) | [RFC3168]
2 | 10 | ECT(0) (ECN-Capable Transport) | [RFC3168]
3 | 11 | CE (Congestion Experienced) | [RFC3168]
When this AVP is used for classification in the Filter-Rule, it MUST
be part of the Classifier Grouped AVP as defined in RFC 5777.
3.2. Congestion-Treatment AVP
The Congestion-Treatment AVP (AVP Code 629) is of type Grouped. It
indicates how to treat traffic IP (5-tuple) flow(s) when congestion
is detected. The detection of congestion can be based on the
reception of IP packets with the Congestion Experience (CE) codepoint
set (see [RFC3168]) or by any other administratively defined
criteria.
A Filter-Rule may contain a Classifier that describes one or many
5-tuples per RFC 5777. This treatment applies to all packets
associated to all 5-tuples (flows) captured by the Filter-Rule.
If the Congestion-Treatment AVP is absent, the treatment of the
congested traffic is left to the discretion of the node performing
quality-of-service (QoS) treatment.
Congestion-Treatment ::= < AVP Header: 629 >
{ Treatment-Action }
[ QoS-Profile-Template ]
[ QoS-Parameters ]
* [ AVP ]
Treatment-Action, QoS-Profile-Template, and QoS-Parameters are
defined in RFC 5777. The Congestion-Treatment AVP is an action and
MUST be an attribute of the Filter-Rule Grouped AVP as defined in RFC
5777.
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3.3. Flow-Count AVP
The Flow-Count AVP (AVP Code 630) is of type Unsigned64.
It indicates the number of protocol-specific flows. The protocol is
determined by the filter (e.g., IPFilterRule, Filter-Id, etc.).
3.4. Packet-Count AVP
The Packet-Count AVP (AVP Code 631) is of type Unsigned64.
It indicates the number of protocol-specific packets. The protocol
is determined by the filter (e.g., IPFilterRule, Filter-Id, etc.).
4. IANA Considerations
4.1. AVP Codes
IANA allocated AVP codes in the IANA-controlled namespace registry
specified in Section 11.1.1 of [RFC6733] for the following AVPs that
are defined in this document.
+------------------------------------------------------------------+
| AVP Section |
|AVP Code Defined Data Type |
+------------------------------------------------------------------+
|ECN-IP-Codepoint 628 3.1 Enumerated |
|Congestion-Treatment 629 3.2 Grouped |
|Flow-Count 630 3.3 Unsigned64 |
|Packet-Count 631 3.4 Unsigned64 |
+------------------------------------------------------------------+
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RFC 7660 Congestion and Filter Attributes October 2015
5. Examples
The following examples illustrate the use of the AVPs defined in this
document.
5.1. Classifier Example
The Classifier AVP (AVP Code 511) specified in RFC 5777 is a grouped
AVP that consists of a set of attributes that specify how to match a
packet. The addition of the ECN-IP-Codepoint is shown here.
Classifier ::= < AVP Header: 511 >
{ Classifier-ID }
[ Protocol ]
[ Direction ]
[ ECN-IP-Codepoint ]
* [ From-Spec ]
* [ To-Spec ]
* [ Diffserv-Code-Point ]
[ Fragmentation-Flag ]
* [ IP-Option ]
* [ TCP-Option ]
[ TCP-Flags ]
* [ ICMP-Type ]
* [ ETH-Option ]
* [ AVP ]
Setting the ECN-IP-Codepoint value to 'CE' would permit the capture
of CE flags in the Flow.
Another Classifier with the ECN-IP-Codepoint value of 'ECT' could be
specified and, when coupled with the Flow-Count AVP, reports the
number of ECT-capable flows.
5.2. Diameter Credit Control (CC) with Congestion Information
Diameter nodes using Credit Control can use the Congestion-Treatment
AVP to trigger specific actions when congestion occurs. This is
similar to the Excess-Treatment Action. The ability to detect when
congestion occurs is specific to the AVPs in the Filter-Rule and
Diameter Client and is no different than how 'Excess' can be
determined for Excess-Treatment. If conditions associated with
Excess-Treatment [RFC5777] or Congestion-Treatment have occurred,
Diameter Clients may autonomously send Credit-Control Requests (CCRs)
during the Service Delivery session as interim events. This is shown
in Figure 1.
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Service Element
End User (CC Client) CC Server
| | |
|(1) Service Request | |
|-------------------->| |
| |(2) CCR (Initial, |
| | QoS-Resources(QoS-Desired)) |
| |--------------------------------->|
| |(3) CCA (Granted-Units, |
| | QoS-Resources(QoS-Authorized))|
| |<---------------------------------|
|(4) Service Delivery | |
|<------------------->| |
| (5) Congestion Detected |
| (6) Congestion Treatment Occurs |
| |(7) CCR (Termination, Used-Units, |
| | Flow-Count, Packet-Count, |
| | QoS-Resources(QoS-Delivered)) |
| |--------------------------------->|
| |(8) CCA |
| |<-------------------------------->|
| | |
| | |
|(9) End of Service | |
|-------------------->| |
| |(10)CCR (Termination, Used-Units, |
| | Flow-Count, Packet-Count, |
| | QoS-Resources(QoS-Delivered)) |
| |--------------------------------->|
| |(11) CCA |
| |<---------------------------------|
Figure 1: Example of a Diameter Credit Control with
Congestion Information
The 'Used-Service-Units' described in RFC 5777 examples is
customarily a Service-Units, Time-Units, or Byte-Count AVP. This is
insufficient to represent network state and does not differentiate
between throughput and good-put (good or quality throughput) even
though the filters may imply good or poor throughput.
Flow-Count and Packet-Count AVPs defined in this document could be
sent with a CCR when the triggering event is related to Congestion-
Treatment. This provides the CC Server with a better view of the
type of congested traffic for improved decision making and charging.
Sending such AVPs under any condition permits rudimentary traffic
profiling regardless of network conditions. For instance, low byte
counts per packet is indicative of web traffic and high byte counts
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per packet with a small number of flows may be indicative of video
traffic. Enriched reporting described here provides relief from Deep
Packet Inspection load and loss of information as traffic becomes
increasingly encrypted.
Some services, e.g., streaming services, limit the number of flows,
Flow-Count, as opposed to other units, i.e. Byte-Count. In such a
case, the Flow-Count AVP may be used in place of Service-Units.
6. Security Considerations
This document describes an extension of RFC 5777 that introduces a
new filter parameter applied to ECN as defined by [RFC3168]. It also
defines a new Grouped AVP that expresses what action to take should
congestion be detected. The Grouped AVP reuses attributes defined in
RFC 5777. As these are extensions to RFC 5777, they do not raise new
security concerns.
The Flow-Count and Packet-Count AVPs can be provided in conjunction
with customary AVPs, e.g., Bytes, Time, Service units, during
accounting activities as described in the base protocol [RFC6733] or
other Diameter applications. These new AVPs provide more information
that can be privacy sensitive. The privacy sensitivity is directly
related to traffic captured by filters and associated reports.
Narrow filtering, which creates the highest level of privacy
sensitivity, is too resource intensive to be widely applied on large
networks. Paradoxically, improving reporting information lessens the
depth of inspection required to characterize traffic for many
congestion management activities as noted in Section 5.2.
If an administrator can provide congestion actions without the need
to report them to a Diameter application, they should use the
Congestion-Treatment AVP, which also reduces Diameter traffic during
congestion events.
The Security Considerations of the Diameter protocol itself have been
discussed in RFC 6733 [RFC6733]. Use of the AVPs defined in this
document MUST take into consideration the security issues and
requirements of the Diameter base protocol.
7. 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,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733,
DOI 10.17487/RFC6733, October 2012,
<http://www.rfc-editor.org/info/rfc6733>.
[RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M.,
Ed., and A. Lior, "Traffic Classification and Quality of
Service (QoS) Attributes for Diameter", RFC 5777,
DOI 10.17487/RFC5777, February 2010,
<http://www.rfc-editor.org/info/rfc5777>.
Acknowledgements
We would like to thank Avi Lior for his guidance and feedback during
the development of this specification.
Authors' Addresses
Lyle Bertz
Sprint
6220 Sprint Parkway
Overland Park, KS 66251
United States
Email: lyleb551144@gmail.com
Serge Manning
Sprint
6220 Sprint Parkway
Overland Park, KS 66251
United States
Email: sergem913@gmail.com
Brent Hirschman
Email: Brent.Hirschman@gmail.com
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