draft-ietf-dime-ovli-04.txt   draft-ietf-dime-ovli-05.txt 
Diameter Maintenance and Extensions (DIME) J. Korhonen, Ed. Diameter Maintenance and Extensions (DIME) J. Korhonen, Ed.
Internet-Draft Broadcom Internet-Draft Broadcom
Intended status: Standards Track S. Donovan, Ed. Intended status: Standards Track S. Donovan, Ed.
Expires: April 30, 2015 B. Campbell Expires: June 6, 2015 B. Campbell
Oracle Oracle
L. Morand L. Morand
Orange Labs Orange Labs
October 27, 2014 December 3, 2014
Diameter Overload Indication Conveyance Diameter Overload Indication Conveyance
draft-ietf-dime-ovli-04.txt draft-ietf-dime-ovli-05.txt
Abstract Abstract
This specification documents a Diameter Overload Control (DOC) base This specification defines a base solution for Diameter overload
solution and the dissemination of the overload report information. control, referred to as Diameter Overload Indication Conveyance
(DOIC).
Requirements Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 41 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 30, 2015. This Internet-Draft will expire on June 6, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Piggybacking Principle . . . . . . . . . . . . . . . . . 7 3.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 7
3.2. DOIC Capability Announcement . . . . . . . . . . . . . . 8 3.2. DOIC Capability Announcement . . . . . . . . . . . . . . 8
3.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9 3.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9
3.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 10 3.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 11
3.5. Simplified Example Architecture . . . . . . . . . . . . . 11 3.5. Simplified Example Architecture . . . . . . . . . . . . . 12
4. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12 4. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12
4.1. Capability Announcement . . . . . . . . . . . . . . . . . 12 4.1. Capability Announcement . . . . . . . . . . . . . . . . . 12
4.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 12 4.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 13
4.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 12 4.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 13
4.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 13 4.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 14
4.2. Overload Report Processing . . . . . . . . . . . . . . . 14 4.2. Overload Report Processing . . . . . . . . . . . . . . . 15
4.2.1. Overload Control State . . . . . . . . . . . . . . . 14 4.2.1. Overload Control State . . . . . . . . . . . . . . . 15
4.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 18 4.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 19
4.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 18 4.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 20
4.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 20 4.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 21
5. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 21 5. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 22
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 21 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 22 5.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 23
5.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 22 5.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 24
6. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 23 6. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 25
6.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 23 6.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 25
6.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 24 6.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 25
6.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 24 6.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 26
6.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 25 6.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 26
6.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 25 6.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 27
6.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 25 6.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 27
6.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 26 6.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 27
6.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 27 6.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 27
7. Error Response Codes . . . . . . . . . . . . . . . . . . . . 27 7. Error Response Codes . . . . . . . . . . . . . . . . . . . . 28
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
8.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 28 8.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 29
8.2. New registries . . . . . . . . . . . . . . . . . . . . . 28 8.2. New registries . . . . . . . . . . . . . . . . . . . . . 29
9. Security Considerations . . . . . . . . . . . . . . . . . . . 29 9. Security Considerations . . . . . . . . . . . . . . . . . . . 30
9.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 29 9.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 30
9.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 30 9.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 31
9.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 30 9.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 32
9.4. End-to End-Security Issues . . . . . . . . . . . . . . . 31 9.4. End-to End-Security Issues . . . . . . . . . . . . . . . 32
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 33
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
11.1. Normative References . . . . . . . . . . . . . . . . . . 32 11.1. Normative References . . . . . . . . . . . . . . . . . . 34
11.2. Informative References . . . . . . . . . . . . . . . . . 32 11.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Issues left for future specifications . . . . . . . 33 Appendix A. Issues left for future specifications . . . . . . . 34
A.1. Additional traffic abatement algorithms . . . . . . . . . 33 A.1. Additional traffic abatement algorithms . . . . . . . . . 35
A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 33 A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 35
A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 33 A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 35
Appendix B. Deployment Considerations . . . . . . . . . . . . . 34 Appendix B. Deployment Considerations . . . . . . . . . . . . . 35
Appendix C. Requirements Conformance Analysis . . . . . . . . . 34 Appendix C. Requirements Conformance Analysis . . . . . . . . . 35
C.1. Deferred Requirements . . . . . . . . . . . . . . . . . . 36
C.2. Detection of non-supporting Intermediaries . . . . . . . 36
C.3. Implicit Application Indication . . . . . . . . . . . . . 36
C.4. Stateless Operation . . . . . . . . . . . . . . . . . . . 37
C.5. No New Vulnerabilities . . . . . . . . . . . . . . . . . 37
C.6. Detailed Requirements . . . . . . . . . . . . . . . . . . 37
C.6.1. General . . . . . . . . . . . . . . . . . . . . . . . 37
C.6.2. Performance . . . . . . . . . . . . . . . . . . . . . 39
C.6.3. Heterogeneous Support for Solution . . . . . . . . . 41
C.6.4. Granular Control . . . . . . . . . . . . . . . . . . 43
C.6.5. Priority and Policy . . . . . . . . . . . . . . . . . 43
C.6.6. Security . . . . . . . . . . . . . . . . . . . . . . 44
C.6.7. Flexibility and Extensibility . . . . . . . . . . . . 45
Appendix D. Considerations for Applications Integrating the DOIC Appendix D. Considerations for Applications Integrating the DOIC
Solution . . . . . . . . . . . . . . . . . . . . . . 34 Solution . . . . . . . . . . . . . . . . . . . . . . 46
D.1. Application Classification . . . . . . . . . . . . . . . 34 D.1. Application Classification . . . . . . . . . . . . . . . 47
D.2. Application Type Overload Implications . . . . . . . . . 35 D.2. Application Type Overload Implications . . . . . . . . . 48
D.3. Request Transaction Classification . . . . . . . . . . . 36 D.3. Request Transaction Classification . . . . . . . . . . . 49
D.4. Request Type Overload Implications . . . . . . . . . . . 37 D.4. Request Type Overload Implications . . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction 1. Introduction
This specification defines a base solution for Diameter Overload This specification defines a base solution for Diameter overload
Control (DOC), referred to as Diameter Overload Indication Conveyance control, referred to as Diameter Overload Indication Conveyance
(DOIC). The requirements for the solution are described and (DOIC), based on the requirements identified in [RFC7068].
discussed in the corresponding design requirements document
[RFC7068]. Note that the overload control solution defined in this
specification does not address all the requirements listed in
[RFC7068]. A number of overload control related features are left
for the future specifications. See Appendix A for a list of
extensions that are currently being considered. See Appendix C for
an analysis of the conformance to the requirements specified in
[RFC7068].
The solution defined in this specification addresses Diameter This specification addresses Diameter overload control between
overload control between Diameter nodes that support the DOIC Diameter nodes that support the DOIC solution. The solution, which
solution. Furthermore, the solution which is designed to apply to is designed to apply to existing and future Diameter applications,
existing and future Diameter applications, requires no changes to the requires no changes to the Diameter base protocol [RFC6733] and is
Diameter base protocol [RFC6733] and is deployable in environments deployable in environments where some Diameter nodes do not implement
where some Diameter nodes do not implement the Diameter overload the Diameter overload control solution defined in this specification.
control solution defined in this specification.
Note that the overload control solution defined in this specification
does not address all the requirements listed in [RFC7068]. A number
of overload control related features are left for future
specifications. See Appendix A for a list of extensions that are
currently being considered. See Appendix C for an analysis of
conformance to the requirements specified in [RFC7068].
2. Terminology and Abbreviations 2. Terminology and Abbreviations
Abatement Abatement
Reaction to receipt of an overload report resulting in a reduction Reaction to receipt of an overload report resulting in a reduction
in traffic sent to the reporting node. Abatement actions include in traffic sent to the reporting node. Abatement actions include
diversion and throttling. diversion and throttling.
Abatement Algorithm Abatement Algorithm
An mechanism requested by reporting nodes and used by reacting A mechanism requested by reporting nodes and used by reacting
nodes to reduce the amount of traffic sent during an occurrence of nodes to reduce the amount of traffic sent during an occurrence of
overload control. overload control.
Diversion Diversion
Abatement of traffic sent to a reporting node by a reacting node A mechanism used for overload abatement by selecting a different
in response to receipt of an overload report. The abatement is path for requests.
achieved by diverting traffic from the reporting node to another
Diameter node that is able to process the request.
Host-Routed Request Host-Routed Requests
The set of requests that a reacting node knows will be served by a Requests that a reacting node knows will be served by a particular
particular host, either due to the presence of a Destination-Host host, either due to the presence of a Destination-Host AVP, or by
AVP, or by some other local knowledge on the part of the reacting some other local knowledge on the part of the reacting node.
node.
Overload Control State (OCS) Overload Control State (OCS)
Reporting and reacting node internally maintained state describing Reporting and reacting node internally maintained state describing
occurrences of overload control. occurrences of overload control.
Overload Report (OLR) Overload Report (OLR)
Information sent by a reporting node indicating the start, Overload control information for a particular overload occurrence
continuation or end of an occurrence of overload control. sent by a reporting node.
Reacting Node Reacting Node
A Diameter node that acts upon an overload report. A Diameter node that acts upon an overload report.
Realm-Routed Request Realm-Routed Requests
Requests that a reacting node does not know the host that will
The set of requests that a reacting node does not know the host service the request.
that will service the request.
Reporting Node Reporting Node
A Diameter node that generates an overload report. (This may or A Diameter node that generates an overload report. (This may or
may not be the overloaded node.) may not be the overloaded node.)
Throttling Throttling
Throttling is the reduction of the number of requests sent to an A mechanism for overload abatement that limits the number of
entity. Throttling can include a Diameter Client or Diameter requests sent by the DIOC reacting node. Throttling can include a
Server dropping requests, or a Diameter Agent rejecting requests Diameter Client not sending requests, or a Diameter Agent or
with appropriate error responses. In extreme cases reporting Server rejecting requests with appropriate error responses. In
nodes can also throttle requests when the requested reductions in both cases the result of the throttling is a permanent rejection
traffic does not sufficiently address the overload scenario. of the transaction.
3. Solution Overview 3. Solution Overview
The Diameter Overload Information Conveyance (DOIC) solution allows The Diameter Overload Information Conveyance (DOIC) solution allows
Diameter nodes to request other nodes to perform overload abatement Diameter nodes to request other Diameter nodes to perform overload
actions, that is, actions to reduce the load offered to the abatement actions, that is, actions to reduce the load offered to the
overloaded node or realm. overloaded node or realm.
A Diameter node that supports DOIC is known as a "DOIC node". Any A Diameter node that supports DOIC is known as a "DOIC node". Any
Diameter node can act as a DOIC node, including clients, servers, and Diameter node can act as a DOIC node, including Diameter Clients,
agents. DOIC nodes are further divided into "Reporting Nodes" and Diameter Servers, and Diameter Agents. DOIC nodes are further
"Reacting Nodes." A reporting node requests overload abatement by divided into "Reporting Nodes" and "Reacting Nodes." A reporting
sending an Overload Report (OLR) to one or more reacting nodes. node requests overload abatement by sending Overload Reports (OLR).
A reacting node acts upon OLRs, and performs whatever actions are A reacting node acts upon OLRs, and performs whatever actions are
needed to fulfil the abatement requests included in the OLRs. A needed to fulfill the abatement requests included in the OLRs. A
Reporting node may report overload on its own behalf, or on behalf of Reporting node may report overload on its own behalf, or on behalf of
other (typically upstream) nodes. Likewise, a reacting node may other nodes. Likewise, a reacting node may perform overload
perform overload abatement on its own behalf, or on behalf of other abatement on its own behalf, or on behalf of other nodes.
(typically downstream) nodes.
A node's role as a DOIC node is independent of its Diameter role. A Diameter node's role as a DOIC node is independent of its Diameter
For example, Diameter Relay and Proxy Agents may act as DOIC nodes, role. For example, Diameter Agents may act as DOIC nodes, even
even though they are not endpoints in the Diameter sense. Since though they are not endpoints in the Diameter sense. Since Diameter
Diameter enables bi-directional applications, where Diameter Servers enables bi-directional applications, where Diameter Servers can send
can send requests towards Diameter Clients, a given Diameter node can requests towards Diameter Clients, a given Diameter node can
simultaneously act as a reporting node and a reacting node. simultaneously act as both a reporting node and a reacting node.
Likewise, a relay or proxy agent may act as a reacting node from the Likewise, a Diameter Agent may act as a reacting node from the
perspective of upstream nodes, and a reporting node from the perspective of upstream nodes, and a reporting node from the
perspective of downstream nodes. perspective of downstream nodes.
DOIC nodes do not generate new messages to carry DOIC related DOIC nodes do not generate new messages to carry DOIC related
information. Rather, they "piggyback" DOIC information over existing information. Rather, they "piggyback" DOIC information over existing
Diameter messages by inserting new AVPs into existing Diameter Diameter messages by inserting new AVPs into existing Diameter
requests and responses. Nodes indicate support for DOIC, and any requests and responses. Nodes indicate support for DOIC, and any
needed DOIC parameters by inserting an OC_Supported_Features AVP needed DOIC parameters, by inserting an OC-Supported-Features AVP
(Section 6.2) into existing requests and responses. Reporting nodes (Section 6.2) into existing requests and responses. Reporting nodes
send OLRs by inserting OC-OLR AVPs (Section 6.3). send OLRs by inserting OC-OLR AVPs (Section 6.3).
A given OLR applies to the Diameter realm and application of the A given OLR applies to the Diameter realm and application of the
Diameter message that carries it. If a reporting node supports more Diameter message that carries it. If a reporting node supports more
than one realm and/or application, it reports independently for each than one realm and/or application, it reports independently for each
combination of realm and application. Similarly, the OC-Supported- combination of realm and application. Similarly, the OC-Supported-
Features AVP applies to the realm and application of the enclosing Features AVP applies to the realm and application of the enclosing
message. This implies that a node may support DOIC for one message. This implies that a node may support DOIC for one
application and/or realm, but not another, and may indicate different application and/or realm, but not another, and may indicate different
DOIC parameters for each application and realm for which it supports DOIC parameters for each application and realm for which it supports
DOIC. DOIC.
Reacting nodes perform overload abatement according to an agreed-upon Reacting nodes perform overload abatement according to an agreed-upon
abatement algorithm. An abatement algorithm defines the meaning of abatement algorithm. An abatement algorithm defines the meaning of
the parameters of an OLR and the procedures required for overload some of the parameters of an OLR and the procedures required for
abatement. This document specifies a single must-support algorithm, overload abatement. An overload abatement algorithm separates
namely the "loss" algorithm (Section 5). Future specifications may Diameter requests into two sets. The first set contains the requests
introduce new algorithms. that are to undergo overload abatement treatment of either throttling
or diversion. The second set contains the requests that are to be
given normal routing treatment. This document specifies a single
must-support algorithm, namely the "loss" algorithm (Section 5).
Future specifications may introduce new algorithms.
Overload conditions may vary in scope. For example, a single Overload conditions may vary in scope. For example, a single
Diameter node may be overloaded, in which case reacting nodes may Diameter node may be overloaded, in which case reacting nodes may
reasonably attempt to send requests to other destinations or via attempt to send requests to other destinations. On the other hand,
other agents. On the other hand, an entire Diameter realm may be an entire Diameter realm may be overloaded, in which case such
overloaded, in which case such attempts would do harm. DOIC OLRs attempts would do harm. DOIC OLRs have a concept of "report type"
have a concept of "report type" (Section 6.6), where the type defines (Section 6.6), where the type defines such behaviors. Report types
such behaviors. Report types are extensible. This document defines are extensible. This document defines report types for overload of a
report types for overload of a specific server, and for overload of specific host, and for overload of an entire realm.
an entire realm.
A report of type host is sent to indicate the overload of a specific A report of type "HOST_REPORT" is sent to indicate the overload of a
server for the application-id indicated in the transaction. When specific host, identified by the Origin-Host AVP of the message
receiving an OLR of type host, a reacting node applies overload containing the OLR, for the application-id indicated in the
abatement to what is referred to in this document as host-routed transaction. When receiving an OLR of type "HOST_REPORT", a reacting
requests. This is the set of requests that the reacting node knows node applies overload abatement treatment to the host-routed requests
will be served by a particular host, either due to the presence of a identified by the overload abatement algorithm (see definition in
Destination-Host AVP, or by some other local knowledge on the part of Section 2) sent for this application to the overloaded host.
the reacting node. The reacting node applies overload abatement on
those host-routed requests which the reacting node knows will be
served by the server that matches the Origin-Host AVP of the received
message that contained the received OLR of type host.
A report type of realm is sent to indicate the overload of all A report of type "REALM_REPORT" is sent to indicate the overload of a
servers in a realm for the application-id. When receiving an OLR of realm for the application-id indicated in the transaction. The
type realm, a reacting node applies overload abatement to what is overloaded realm is identified by the Destination-Realm AVP of the
referred to in this document as realm-routed requests. This is the message containing the OLR. When receiving an OLR of type
set of requests that are not host-routed as defined in the previous "REALM_REPORT", a reacting node applies overload abatement treatment
paragraph. to realm-routed requests identified by the overload abatement
algorithm (see definition in Section 2) sent for this application to
the overloaded realm.
While a reporting node sends OLRs to "adjacent" reacting nodes, nodes While a reporting node sends OLRs to "adjacent" reacting nodes, nodes
that are "adjacent" for DOIC purposes may not be adjacent from a that are "adjacent" for DOIC purposes may not be adjacent from a
Diameter, or transport, perspective. For example, one or more Diameter, or transport, perspective. For example, one or more
Diameter agents that do not support DOIC may exist between a given Diameter agents that do not support DOIC may exist between a given
pair of reporting and reacting nodes, as long as those agents pass pair of reporting and reacting nodes, as long as those agents pass
unknown AVPs through unchanged. The report types described in this unknown AVPs through unchanged. The report types described in this
document can safely pass through non-supporting agents. This may not document can safely pass through non-supporting agents. This may not
be true for report types defined in future specifications. Documents be true for report types defined in future specifications.
that introduce new report types MUST describe any limitations on
their use across non-supporting agents.
3.1. Piggybacking Principle 3.1. Piggybacking
The overload control AVPs defined in this specification have been There is no new Diameter application defined to carry overload
designed to be piggybacked on top of existing application messages. related AVPs. The overload control AVPs defined in this
This is made possible by adding overload control top-level AVPs, the specification have been designed to be piggybacked on top of existing
OC-OLR AVP and the OC-Supported-Features AVP, as optional AVPs into application messages. This is made possible by adding overload
existing commands when the corresponding Command Code Format (CCF) control AVPs, the OC-OLR AVP and the OC-Supported-Features AVP, as
specification allows adding new optional AVPs (see Section 1.3.4 of optional AVPs into existing commands when the corresponding Command
[RFC6733]). Code Format (CCF) specification allows adding new optional AVPs (see
Section 1.3.4 of [RFC6733]).
Reacting nodes indicate support for DOIC by including the OC- Reacting nodes indicate support for DOIC by including the OC-
Supported-Features AVP in all request messages originated or relayed Supported-Features AVP in all request messages originated or relayed
by the reacting node. by the reacting node.
Reporting nodes indicate support for DOIC by including the OC- Reporting nodes indicate support for DOIC by including the OC-
Supported-Features AVP in all answer messages originated or relayed Supported-Features AVP in all answer messages originated or relayed
by the reporting node. Reporting nodes also include overload reports by the reporting node that are in response to a request that
using the OC-OLR AVP in answer messages. contained the OC-Supported-Features AVP. Reporting nodes also
include overload reports using the OC-OLR AVP in answer messages.
Note: There is no new Diameter application defined to carry
overload related AVPs. The DOIC AVPs are carried in existing
Diameter application messages.
Note that the overload control solution does not have fixed server Note that the overload control solution does not have fixed server
and client roles. The DOIC node role is determined based on the and client roles. The DOIC node role is determined based on the
message type: whether the message is a request (i.e. sent by a message type: whether the message is a request (i.e. sent by a
"reacting node") or an answer (i.e. send by a "reporting node"). "reacting node") or an answer (i.e. send by a "reporting node").
Therefore, in a typical "client-server" deployment, the Diameter Therefore, in a typical "client-server" deployment, the Diameter
Client MAY report its overload condition to the Diameter Server for Client MAY report its overload condition to the Diameter Server for
any Diameter Server initiated message exchange. An example of such any Diameter Server initiated message exchange. An example of such
is the Diameter Server requesting a re-authentication from a Diameter is the Diameter Server requesting a re-authentication from a Diameter
Client. Client.
3.2. DOIC Capability Announcement 3.2. DOIC Capability Announcement
The DOIC solution supports the ability for Diameter nodes to The DOIC solution supports the ability for Diameter nodes to
determine if other nodes in the path of a request support the determine if other nodes in the path of a request support the
solution. This capability is referred to as DOIC Capability solution. This capability is referred to as DOIC Capability
Announcement (DCA) and is separate from Diameter Capability Exchange. Announcement (DCA) and is separate from Diameter Capability Exchange.
The DCA solution uses the OC-Supported-Features AVPs to indicate the The DCA mechanism uses the OC-Supported-Features AVPs to indicate the
Diameter overload features supported. Diameter overload features supported.
The first node in the path of a Diameter request that supports the The first node in the path of a Diameter request that supports the
DOIC solution inserts the OC-Supported-Feature AVP in the request DOIC solution inserts the OC-Supported-Features AVP in the request
message. This includes an indication that it supports the loss message.
overload abatement algorithm defined in this specification (see
Section 5). This ensures that there is at least one commonly
supported overload abatement algorithm between the reporting node and
the reacting nodes in the path of the request.
DOIC must support deployments where Diameter Clients and/or Note: As discussed elsewhere in the document, agents in the path
Diameter Servers do not support the DOIC solution. In this of the request can modify the OC-Supported-Features AVP.
scenario, it is assumed that Diameter Agents that support the DOIC
solution will handle overload abatement for the non supporting
Diameter nodes. In this case the DOIC agent will insert the OC-
Supporting-Features AVP in requests that do not already contain
one, telling the reporting node that there is a DOIC node that
will handle overload abatement.
The reporting node inserts the OC-Supported-Feature AVP in all answer Note: The DOIC solution must support deployments where Diameter
messages to requests that contained the OC-Supported-Feature AVP. Clients and/or Diameter Servers do not support the DOIC solution.
The contents of the reporting node's OC-Supported-Feature AVP In this scenario, Diameter Agents that support the DOIC solution
indicate the set of Diameter overload features supported by the may handle overload abatement for the non supporting Diameter
reporting node with one exception. nodes. In this case the DOIC agent will insert the OC-Supported-
Features AVP in requests that do not already contain one, telling
the reporting node that there is a DOIC node that will handle
overload abatement. For transactions where there was an OC-
Supporting-Features AVP in the request, the agent will insert the
OC-Supported-Features AVP in answers, telling the reacting node
that there is a reporting node.
The reporting node only includes an indication of support for one The OC-Feature-Vector AVP will contain an indication of support for
overload abatement algorithm. This is the algorithm that the the loss overload abatement algorithm defined in this specification
reporting node intends to use should it enter an overload condition (see Section 5). This ensures that there is at least one commonly
or requests to use while it actually is in an overload condition. supported overload abatement algorithm between the reporting node and
the reacting node(s) in the path of the request.
The reporting node inserts the OC-Supported-Features AVP in all
answer messages to requests that contained the OC-Supported-Features
AVP. The contents of the reporting node's OC-Supported-Features AVP
indicate the set of Diameter overload features supported by the
reporting node. This specification defines one exception - the
reporting node only includes an indication of support for one
overload abatement algorithm, independent of the number of overload
abatement algorithms actually supported by the reacting node. The
overload abatement algorithm indicated is the algorithm that the
reporting node intends to use should it enter an overload condition.
Reacting nodes can use the indicated overload abatement algorithm to Reacting nodes can use the indicated overload abatement algorithm to
prepare for possible overload reports and must use the indicated prepare for possible overload reports and must use the indicated
overload abatement algorithm if traffic reduction is actually overload abatement algorithm if traffic reduction is actually
requested. requested.
Note that the loss algorithm defined in this document is a Note that the loss algorithm defined in this document is a
stateless abatement algorithm. As a result it does not require stateless abatement algorithm. As a result it does not require
any actions by reacting nodes prior to the receipt of an overload any actions by reacting nodes prior to the receipt of an overload
report. Stateful abatement algorithms that base the abatement report. Stateful abatement algorithms that base the abatement
logic on a history of request messages sent might require reacting logic on a history of request messages sent might require reacting
nodes to maintain state to ensure that overload reports can be nodes to maintain state in advance of receiving an overload report
properly handled. to ensure that the overload reports can be properly handled.
Reporting nodes are allowed to change the overload abatement
algorithm indicated in the OC-Feature-Vector AVP if the reporting
node is not currently in an overload condition and sending overload
reports. The reporting node is not allowed to change the overload
abatement algorithm while the reporting node is in an overload
condition.
The individual features supported by the DOIC nodes are indicated in The individual features supported by the DOIC nodes are indicated in
the OC-Feature-Vector AVP. Any semantics associated with the the OC-Feature-Vector AVP. Any semantics associated with the
features will be defined in extension specifications that introduce features will be defined in extension specifications that introduce
the features. the features.
The DCA mechanism must also support the scenario where the set of The DCA mechanism must also allow the scenario where the set of
features supported by the sender of a request and by agents in the features supported by the sender of a request and by agents in the
path of a request differ. In this case, the agent updates the OC- path of a request differ. In this case, the agent updates the OC-
Supported-Feature AVP to reflect the mixture of the two sets of Supported-Features AVP to reflect the mixture of the two sets of
supported features. supported features.
The logic to determine the content of the modified OC-Supported- Note: The logic to determine the content of the modified OC-
Feature AVP is out-of-scope for this specification and is left to Supported-Features AVP is out-of-scope for this specification and
implementation decisions. Care must be taken not to introduce is left to implementation decisions. Care must be taken not to
interoperability issues for downstream or upstream DOIC nodes. introduce interoperability issues for downstream or upstream DOIC
nodes.
3.3. DOIC Overload Condition Reporting 3.3. DOIC Overload Condition Reporting
As with DOIC Capability Announcement, Overload Condition Reporting As with DOIC capability announcement, overload condition reporting
uses new AVPs (Section 6.3) to indicate an overload condition. uses new AVPs (Section 6.3) to indicate an overload condition.
The OC-OLR AVP is referred to as an overload report. The OC-OLR AVP The OC-OLR AVP is referred to as an overload report. The OC-OLR AVP
includes the type of report, a sequence number, the length of time includes the type of report, a sequence number, the length of time
that the report is valid and abatement algorithm specific AVPs. that the report is valid and abatement algorithm specific AVPs.
Two types of overload reports are defined in this document, host Two types of overload reports are defined in this document, host
reports and realm reports. reports and realm reports.
A report of type host is sent to indicate the overload of a specific A report of type "HOST_REPORT" is sent to indicate the overload of a
Diameter node for the application-id indicated in the transaction. specific Diameter node for the application-id indicated in the
When receiving an OLR of type host, a reacting node applies overload transaction. When receiving an OLR of type host, a reacting node
abatement to what is referred to in this document as host-routed applies overload abatement to what is referred to in this document as
requests. This is the set of requests that the reacting node knows host-routed requests. The reacting node applies overload abatement
will be served by a particular host, either due to the presence of a on those host-routed requests which the reacting node knows will be
Destination-Host AVP, or by some other local knowledge on the part of
the reacting node. The reacting node applies overload abatement on
those host-routed requests which the reacting node knows will be
served by the server that matches the Origin-Host AVP of the received served by the server that matches the Origin-Host AVP of the received
message that contained the received OLR of type host. message that contained the received OLR of type host.
Realm reports apply to realm-routed requests for a specific realm as A report of type "REALM_REPORT" applies to realm-routed requests for
indicated in the Destination-Realm AVP. a specific realm as indicated in the Destination-Realm AVP.
This document assumes that there is a single source for realm-reports
for a given realm, or that if multiple nodes can send realm reports,
that each such node has full knowledge of the overload state of the
entire realm. A reacting node cannot distinguish between receiving
realm-reports from a single node, or from multiple nodes.
Note: Known issues exist if multiple sources for overload reports
which apply to the same Diameter entity exist. Reacting nodes
have no way of determining the source and, as such, will treat
them as coming from a single source. Variance in sequence numbers
between the two sources can then cause incorrect overload
abatement treatment to be applied for indeterminate periods of
time.
Reporting nodes are responsible for determining the need for a Reporting nodes are responsible for determining the need for a
reduction of traffic. The method for making this determination is reduction of traffic. The method for making this determination is
implementation specific and depend on the type of overload report implementation specific and depend on the type of overload report
being generated. A host report, for instance, will generally be being generated. A host-report, for instance, will generally be
generated by tracking utilization of resources required by the host generated by tracking utilization of resources required by the host
to handle transactions for the Diameter application. A realm report to handle transactions for the Diameter application. A realm-report
will generally impact the traffic sent to multiple hosts and, as generally impacts the traffic sent to multiple hosts and, as such,
such, will typically require tracking the capacity of the servers requires tracking the capacity all servers for realm-routed requests
able to handle realm-routed requests for the application. for the application and realm.
Once a reporting node determines the need for a reduction in traffic, Once a reporting node determines the need for a reduction in traffic,
it uses the DOIC defined AVPs to report on the condition. These AVPs it uses the DOIC defined AVPs to report on the condition. These AVPs
are included in answer messages sent or relayed by the reporting are included in answer messages sent or relayed by the reporting
node. The reporting node indicates the overload abatement algorithm node. The reporting node indicates the overload abatement algorithm
that is to be used to handle the traffic reduction in the OC- that is to be used to handle the traffic reduction in the OC-
Supported-Features AVP. The OC-OLR AVP is used to communicate Supported-Features AVP. The OC-OLR AVP is used to communicate
information about the requested reduction. information about the requested reduction.
Reacting nodes, upon receipt of an overload report, are responsible Reacting nodes, upon receipt of an overload report, are responsible
for applying the abatement algorithm to traffic impacted by the for applying the overload abatement algorithm to traffic impacted by
overload report. The method used for that abatement is dependent on the overload report. The method used to determine the requests that
the abatement algorithm. The loss abatement algorithm is defined in are to receive overload abatement treatment is dependent on the
this document (Section 5). Other abatement algorithms can be defined abatement algorithm. The loss abatement algorithm is defined in this
in extensions to the DOIC solutions. document (Section 5). Other abatement algorithms can be defined in
extensions to the DOIC solutions.
Two types of overload abatement treatment are defined, diversion and
throttling. Reacting nodes are responsible for determining which
treatment is appropriate for individual requests.
As the conditions that lead to the generation of the overload report As the conditions that lead to the generation of the overload report
change the reporting node can send new overload reports requesting change the reporting node can send new overload reports requesting
greater reduction if the condition gets worse or less reduction if greater reduction if the condition gets worse or less reduction if
the condition improves. The reporting node sends an overload report the condition improves. The reporting node sends an overload report
with a duration of zero to indicate that the overload condition has with a duration of zero to indicate that the overload condition has
ended and use of the abatement algorithm is no longer needed. ended and need for use of the abatement algorithm to reduce traffic
sent is no longer needed.
The reacting node also determines when the overload report expires The reacting node also determines when the overload report expires
based on the OC-Validity-Duration AVP in the overload report and based on the OC-Validity-Duration AVP in the overload report and
stops applying the abatement algorithm when the report expires. stops applying the abatement algorithm when the report expires.
3.4. DOIC Extensibility 3.4. DOIC Extensibility
The DOIC solution is designed to be extensible. This extensibility The DOIC solution is designed to be extensible. This extensibility
is based on existing Diameter based extensibility mechanisms. is based on existing Diameter based extensibility mechanisms, along
with the DOIC capability announcement mechanism.
There are multiple categories of extensions that are expected. This There are multiple categories of extensions that are expected. This
includes the definition of new overload abatement algorithms, the includes the definition of new overload abatement algorithms, the
definition of new report types and new definitions of the scope of definition of new report types and the definition of new scopes of
messages impacted by an overload report. messages impacted by an overload report.
The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes
to communicate supported features. The specific features supported to communicate supported features. The specific features supported
by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC
extensions must define new values for the OC-Feature-Vector AVP. extensions that require new normative behavior define new values for
the OC-Feature-Vector AVP. DOIC extensions also have the ability to
DOIC extensions also have the ability to add new AVPs to the OC- add new AVPs to the OC-Supported-Features AVP, if additional
Supported-Features AVP, if additional information about the new information about the new feature is required.
feature is required.
Reporting nodes use the OC-OLR AVP to communicate overload Reporting nodes use the OC-OLR AVP to communicate overload
occurrences. This AVP can also be extended to add new AVPs allowing occurrences. This AVP can also be extended to add new AVPs allowing
a reporting nodes to communicate additional information about reporting nodes to communicate additional information about handling
handling an overload condition. an overload condition.
If necessary, new extensions can also define new top-level AVPs. It If necessary, new extensions can also define new AVPs that are not
is, however, recommended that DOIC extensions use the OC-Supported- part of the OC-Supported-Features and OC-OLR group AVPs. It is,
Features and OC-OLR to carry all DOIC related AVPs. however, recommended that DOIC extensions use the OC-Supported-
Features AVP and OC-OLR AVP to carry all DOIC related AVPs.
3.5. Simplified Example Architecture 3.5. Simplified Example Architecture
Figure 1 illustrates the simplified architecture for Diameter Figure 1 illustrates the simplified architecture for Diameter
overload information conveyance. overload information conveyance.
Realm X Same or other Realms Realm X Same or other Realms
<--------------------------------------> <----------------------> <--------------------------------------> <---------------------->
+--^-----+ : (optional) : +--^-----+ : (optional) :
skipping to change at page 11, line 42 skipping to change at page 12, line 29
|Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+ |Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+
|Server B| : : |Server B| : :
+---^----+ : : +---^----+ : :
End-to-end Overload Indication End-to-end Overload Indication
1) <-----------------------------------------------> 1) <----------------------------------------------->
Diameter Application Y Diameter Application Y
Overload Indication A Overload Indication A' Overload Indication A Overload Indication A'
2) <----------------------> <----------------------> 2) <----------------------> <---------------------->
standard base protocol standard base protocol Diameter Application Y Diameter Application Y
Figure 1: Simplified architecture choices for overload indication Figure 1: Simplified architecture choices for overload indication
delivery delivery
In Figure 1, the Diameter overload indication can be conveyed (1) In Figure 1, the Diameter overload indication can be conveyed (1)
end-to-end between servers and clients or (2) between servers and end-to-end between servers and clients or (2) between servers and
Diameter agent inside the realm and then between the Diameter agent Diameter agent inside the realm and then between the Diameter agent
and the clients. and the clients.
4. Solution Procedures 4. Solution Procedures
This section outlines the normative behavior associated with the DOIC This section outlines the normative behavior for the DOIC solution.
solution.
4.1. Capability Announcement 4.1. Capability Announcement
This section defines DOIC Capability Announcement (DCA) behavior. This section defines DOIC Capability Announcement (DCA) behavior.
4.1.1. Reacting Node Behavior 4.1.1. Reacting Node Behavior
A reacting node MUST include the OC-Supported-Features AVP in all A reacting node MUST include the OC-Supported-Features AVP in all
request messages. requests. It MAY include the OC-Feature-Vector AVP. If it does so,
it MUST indicate support for the "loss" algorithm. If the reacting
A reacting node MAY include the OC-Feature-Vector AVP with an node is configured to support features (including other algorithms)
indication of the loss algorithm. A reacting node MUST include the in addition to the loss algorithm, it MUST indicate such support in
OC-Feature-Vector AVP to indicate support for abatement algorithms in an OC-Feature-Vector AVP.
addition to the loss algorithm.
A reacting node SHOULD indicate support for all other DOIC features
it supports.
Not all DOIC features will necessarily apply to all transactions.
For instance, there may be a future extension that only applies to
session based applications. A reacting node that supports this
extension can choose to not include it for non session based
applications.
An OC-Supported-Features AVP in answer messages indicates there is a An OC-Supported-Features AVP in answer messages indicates there is a
reporting node for the transaction. The reacting node MAY take reporting node for the transaction. The reacting node MAY take
action based on the features indicated in the OC-Feature-Vector AVP. action, for example creating state for some stateful abatement
algorithm, based on the features indicated in the OC-Feature-Vector
AVP.
Note that the loss abatement algorithm is the only feature Note: The loss abatement algorithm does not require stateful
described in this document and it does not require action to be behavior when there is no active overload report. This behavior
taken when there is an active overload report. This behavior is is described in Section 4.2 and Section 5.
described in Section 4.2 and Section 5.
4.1.2. Reporting Node Behavior 4.1.2. Reporting Node Behavior
Upon receipt of a request message, a reporting node determines if Upon receipt of a request message, a reporting node determines if
there is a reacting node for the transaction based on the presence of there is a reacting node for the transaction based on the presence of
the OC-Supported-Features AVP. the OC-Supported-Features AVP in the request message.
If the request message contains an OC-Supported-Features AVP then the If the request message contains an OC-Supported-Features AVP then a
reporting node MUST include the OC-Supported-Features AVP in the reporting node MUST include the OC-Supported-Features AVP in the
answer message for that transaction. answer message for that transaction.
The reporting node MUST NOT include the OC-Supported-Features AVP, A reporting node MUST NOT include the OC-Supported-Features AVP, OC-
OC-OLR AVP or any other overload control AVPs defined in extension OLR AVP or any other overload control AVPs defined in extension
drafts in response messages for transactions where the request drafts in response messages for transactions where the request
message does not include the OC-Supported-Features AVP. Lack of the message does not include the OC-Supported-Features AVP. Lack of the
OC-Supported-Features AVP in the request message indicates that there OC-Supported-Features AVP in the request message indicates that there
is no reacting node for the transaction. is no reacting node for the transaction.
Based on the content of the OC-Supported-Features AVP in the request A reporting node knows what overload control functionality is
message, the reporting node knows what overload control functionality supported by the reacting node based on the content of the OC-
is supported by the reacting node. The reporting node then acts Feature-Vector AVP in the request message.
accordingly for the subsequent answer messages it initiates.
The reporting node MUST indicate support for one and only one A reporting node MUST indicate support for one and only one abatement
abatement algorithm in the OC-Feature-Vector AVP. The abatement algorithm in the OC-Feature-Vector AVP. The abatement algorithm
algorithm included MUST be from the set of abatement algorithms selected MUST indicate the abatement algorithm the reporting node
contained in the request message's OC-Supported-Features AVP. The wants the reacting node to use when the reporting node enters an
abatement algorithm included MUST indicate the abatement algorithm overload condition.
the reporting node wants the reacting node to use when the reporting
node enters an overload condition.
For an ongoing overload state, a reacting node MUST keep the The abatement algorithm selected MUST be from the set of abatement
algorithm that was selected by the reporting node in further requests algorithms contained in the request message's OC-Feature-Vector AVP.
towards the reporting node. The reporting node SHOULD NOT change the
selected algorithm during a period of time that it is in an overload A reporting node that selects the loss algorithm may do so by
condition and, as a result, is sending OC-OLR AVPs in answer including the OC-Feature-Vector AVP with an explicit indication of
the loss algorithm, or it MAY omit OC-Feature-Vector. If it selects
a different algorithm, it MUST include the OC-Feature-Vector AVP with
an explicit indication of the selected algorithm.
For an ongoing overload condition, a reporting node MUST NOT change
the selected algorithm during the period of time that it is in an
overload condition and, as a result, is sending OC-OLR AVPs in answer
messages. messages.
The reporting node MAY change the overload abatement algorithm
indicated in the OC-Supported-Features AVP at any time as long as no
previously sent OLRs may be active.
The reporting node SHOULD indicate support for other DOIC features The reporting node SHOULD indicate support for other DOIC features
defined in extension drafts that it supports and that apply to the defined in extension drafts that it supports and that apply to the
transaction. transaction.
Note that not all DOIC features will apply to all Diameter Note: Not all DOIC features will apply to all Diameter
applications or deployment scenarios. The features included in applications or deployment scenarios. The features included in
the OC-Feature-Vector AVP are based on local reporting node the OC-Feature-Vector AVP are based on local reporting node
policy. policy.
4.1.3. Agent Behavior 4.1.3. Agent Behavior
Diameter agents that support DOIC MUST ensure that all messages have Diameter Agents that support DOIC SHOULD ensure that all messages
the OC-Supporting-Features AVP. If a message handled by the DOIC relayed by the agent contain the OC-Supported-Features AVP.
agent does not include the OC-Supported-Features AVP then the DOIC
agent inserts the AVP. If the message already has the AVP then the
agent either leaves it unchanged in the relayed message or modifies
it to reflect a mixed set of DOIC features.
An agent MAY modify the OC-Supported-Features AVP carried in answer A Diameter Agent SHOULD take on reacting node behavior for Diameter
messages. endpoints that do not support the DOIC solution. A Diameter Agent
detects that a Diameter endpoint does not support DOIC reacting node
behavior when there is no OC-Supported-Features AVP in a request
message.
For a Diameter Agent to be a reacting node for a non supporting
Diameter endpoint, the Diameter Agent MUST include the OC-Supported-
Features AVP in request messages it receives that do not contain the
OC-Supported-Features AVP.
A Diameter Agent SHOULD take on reporting node behavior for Diameter
endpoints that do not support the DOIC solution. A Diameter Agent
detects that a Diameter endpoint does not support DOIC reporting node
behavior when there is no OC-Supported-Features AVP in an answer
message for a transaction that contained the OC-Supported-Features
AVP in the request message.
For a Diameter Agent to take on reporting node behavior for a non
supporting Diameter endpoint the Diameter Agent MUST include the OC-
Supported-Features AVP in answer messages it receives that do not
contain the OC-Supported-Features AVP.
As with a Diameter endpoint taking on reporting node behavior, a
Diameter Agent MUST only include the OC-Supported-Features AVP in
answer messages for transactions where the request message received
by the Diameter Agent had an OC-Supported-Features AVP.
If a request message already has the OC-Supported-Features AVP then a
Diameter Agent MAY leave it unchanged in the relayed message or MAY
modify it to reflect the features appropriate for the transaction.
For instance, if the agent supports a superset of the features For instance, if the agent supports a superset of the features
reported by the reacting node then the agent might choose, based reported by the reacting node then the agent might choose, based
on local policy, to advertise that superset of features to the on local policy, to advertise that superset of features to the
reporting node. reporting node.
If the agent modifies the OC-Supported-Features AVP sent to the If the Diameter Agent changes the OC-Supported-Features AVP in a
reporting node then it might also need to modify the OC-Supported- request message then it is likely it will also need to modify the OC-
Features AVP sent to a reacting node in the subsequent answer Supported-Features AVP in the answer message for the transaction. As
message, as it cannot send an indication of support for features such, a Diameter Agent MAY modify the OC-Supported-Features AVP
that are not supported by the reacting node. carried in answer messages.
Editor's note: There is an open issue on the wording around agent When making changes to the OC-Supported-Features AVP the Diameter
behavior in this case that needs to be resolved prior to finishing Agent needs to ensure that there is no ambiguity in DOIC behavior for
this document. both upstream and downstream DOIC nodes.
4.2. Overload Report Processing 4.2. Overload Report Processing
4.2.1. Overload Control State 4.2.1. Overload Control State
Both reacting and reporting nodes maintain Overload Control State Both reacting and reporting nodes maintain Overload Control State
(OCS) for active overload conditions. (OCS) for active overload conditions. The following sections define
behavior associated with that OCS.
4.2.1.1. Overload Control State for Reacting Nodes 4.2.1.1. Overload Control State for Reacting Nodes
A reacting node SHOULD maintain the following OCS per supported A reacting node SHOULD maintain the following OCS per supported
Diameter application: Diameter application:
o A host-type OCS entry for each Destination-Host to which it sends o A host-type OCS entry for each Destination-Host to which it sends
host-type requests and host-type requests and
o A realm-type OCS entry for each Destination-Realm to which it o A realm-type OCS entry for each Destination-Realm to which it
sends realm-type requests. sends realm-type requests.
A host-type OCS entry is identified by the pair of Application-Id and A host-type OCS entry is identified by the pair of application-id and
Host-Id. the node's DiameterIdentity.
A realm-type OCS entry is identified by the pair of Application-Id A realm-type OCS entry is identified by the pair of application-d and
and Realm-Id. realm.
The host-type and realm-type OCS entries MAY include the following The host-type and realm-type OCS entries MAY include the following
information (the actual information stored is an implementation information (the actual information stored is an implementation
decision): decision):
o Sequence number (as received in OC-OLR) o Sequence number (as received in OC-OLR)
o Time of expiry (derived from OC-Validity-Duration AVP received in o Time of expiry (derived from OC-Validity-Duration AVP received in
the OC-OLR AVP and time of reception of the message carrying OC- the OC-OLR AVP and time of reception of the message carrying OC-
OLR AVP) OLR AVP)
o Selected Abatement Algorithm (as received in OC-Supported-Features o Selected Abatement Algorithm (as received in the OC-Supported-
AVP) Features AVP)
o Abatement Algorithm specific input data (as received within the o Abatement Algorithm specific input data (as received in the OC-OLR
OC-OLR AVP, for example, OC-Reduction-Percentage for the Loss AVP, for example, OC-Reduction-Percentage for the Loss abatement
abatement algorithm) algorithm)
4.2.1.2. Overload Control State for Reporting Nodes 4.2.1.2. Overload Control State for Reporting Nodes
A reporting node SHOULD maintain OCS entries per supported Diameter A reporting node SHOULD maintain OCS entries per supported Diameter
application, per supported (and eventually selected) Abatement application, per supported (and eventually selected) Abatement
Algorithm and per report-type. Algorithm and per report-type.
An OCS entry is identified by the pair of Application-Id and An OCS entry is identified by the tuple of Application-Id, Report-
Abatement Algorithm. Type and Abatement Algorithm and MAY include the following
information (the actual information stored is an implementation
The OCS entry for a given pair of Application and Abatement Algorithm decision):
MAY include the information (the actual information stored is an
implementation decision):
o Report type
o Sequence number o Sequence number
o Validity Duration o Validity Duration
o Expiration Time o Expiration Time
o Algorithm specific input data (for example, the Reduction o Algorithm specific input data (for example, the Reduction
Percentage for the Loss Abatement Algorithm) Percentage for the Loss Abatement Algorithm)
4.2.1.3. Reacting Node Maintenance of Overload Control State 4.2.1.3. Reacting Node Maintenance of Overload Control State
When a reacting node receives an OC-OLR AVP, it MUST determine if it When a reacting node receives an OC-OLR AVP, it MUST determine if it
is for an existing or new overload condition. is for an existing or new overload condition.
For the remainder of this section the term OLR referres to the Note: For the remainder of this section the term OLR refers to the
combination of the contents of the received OC-OLR AVP and the combination of the contents of the received OC-OLR AVP and the
abatement algorithm indicated in the received OC-Supported- abatement algorithm indicated in the received OC-Supported-
Features AVP. Features AVP.
The OLR is for an existing overload condition if the reacting node When receiving an answer message with multiple OLRs or different
has an OCS that matches the received OLR. types, a reporting node MUST process each received OLR.
For a host report-type this means it matches the app-id and host-id When receiving an OC-OLR AVPs with unknown values, a reacting node
in an existing host OCS entry. SHOULD be silently discarded by reacting nodes and the event SHOULD
be logged.
For a realm report-type this means it matches the app-id and realm-id The OLR is for an existing overload condition if a reacting node has
in an existing realm OCS entry. an OCS that matches the received OLR.
If the OLR is for an existing overload condition then it MUST For a host-report this means it matches the application-id and the
determine if the OLR is a retransmission or an update to the existing host's DiameterIdentity in an existing host OCS entry.
OLR.
For a realm-report this means it matches the application-id and the
realm in an existing realm OCS entry.
If the OLR is for an existing overload condition then a reacting node
MUST determine if the OLR is a retransmission or an update to the
existing OLR.
If the sequence number for the received OLR is greater than the If the sequence number for the received OLR is greater than the
sequence number stored in the matching OCS entry then the reacting sequence number stored in the matching OCS entry then a reacting node
node MUST update the matching OCS entry. MUST update the matching OCS entry.
If the sequence number for the received OLR is less than or equal to If the sequence number for the received OLR is less than or equal to
the sequence number in the matching OCS entry then the reacting node the sequence number in the matching OCS entry then a reacting node
MUST silently ignore the received OLR. The matching OCS MUST NOT be MUST silently ignore the received OLR. The matching OCS MUST NOT be
updated in this case. updated in this case.
If the received OLR is for a new overload condition then the reacting If the received OLR is for a new overload condition then a reacting
node MUST generate a new OCS entry for the overload condition. node MUST generate a new OCS entry for the overload condition.
For a host report-type this means it creates on OCS entry with the For a host-report this means a reacting node creates on OCS entry
app-id of the application-id in the received message and host-id of with the application-id in the received message and DiameterIdentity
the Origin-Host in the received message. of the Origin-Host in the received message.
Note: This solution assumes that the Origin-Host AVP in the answer Note: This solution assumes that the Origin-Host AVP in the answer
message included by the reporting node is not changed along the message included by the reporting node is not changed along the
path to the reacting node. path to the reacting node.
For a realm report-type this means it creates on OCS entry with the For a realm-report this means a reacting node creates on OCS entry
app-id of the application-id in the received message and realm-id of with the application-id in the received message and realm of the
the Origin-Realm in the received message. Origin-Realm in the received message.
If the received OLR contains a validity duration of zero ("0") then If the received OLR contains a validity duration of zero ("0") then a
the reacting node MUST update the OCS entry as being expired. reacting node MUST update the OCS entry as being expired.
Note that it is not necessarily appropriate to delete the OCS Note: It is not necessarily appropriate to delete the OCS entry,
entry, as there is recommended behavior that the reacting node as there is recommended behavior that the reacting node slowly
slowly returns to full traffic when ending an overload abatement returns to full traffic when ending an overload abatement period.
period.
The reacting node does not delete an OCS when receiving an answer The reacting node does not delete an OCS when receiving an answer
message that does not contain an OC-OLR AVP (i.e. absence of OLR message that does not contain an OC-OLR AVP (i.e. absence of OLR
means "no change"). means "no change").
4.2.1.4. Reporting Node Maintenance of Overload Control State 4.2.1.4. Reporting Node Maintenance of Overload Control State
A reporting node SHOULD create a new OCS entry when entering an A reporting node SHOULD create a new OCS entry when entering an
overload condition. overload condition.
If the reporting node knows through absence of the OC-Supported- Note: If a reporting node knows through absence of the OC-
Features AVP in received messages that there are no reacting nodes Supported-Features AVP in received messages that there are no
supporting DOIC then the reporting node can choose to not create reacting nodes supporting DOIC then the reporting node can choose
OCS entries. to not create OCS entries.
When generating a new OCS entry the sequence number MAY be set to any When generating a new OCS entry the sequence number SHOULD be set to
value if there is no unexpired overload report for previous overload zero ("0").
conditions sent to any reacting node for the same application and
report-type.
When generating sequence numbers for new overload conditions, the new When generating sequence numbers for new overload conditions, the new
sequence number MUST be greater than any sequence number in an active sequence number MUST be greater than any sequence number in an active
(unexpired) overload report previously sent by the reporting node. (unexpired) overload report for the same application and report-type
This property MUST hold over a reboot of the reporting node. previously sent by the reporting node. This property MUST hold over
a reboot of the reporting node.
The reporting node MUST update an OCS entry when it needs to adjust Note: One way of addressing this over a reboot of a reporting node
the validity duration of the overload condition at reacting nodes. is to use a time stamp for the first overload condition that
occurs after the report and to start using sequence numbers of
zero for subsequent overload conditions.
For instance, if the reporting node wishes to instruct reacting A reporting node MUST update an OCS entry when it needs to adjust the
validity duration of the overload condition at reacting nodes.
For instance, if a reporting node wishes to instruct reacting
nodes to continue overload abatement for a longer period of time nodes to continue overload abatement for a longer period of time
that originally communicated. This also applies if the reporting than originally communicated. This also applies if the reporting
node wishes to shorten the period of time that overload abatement node wishes to shorten the period of time that overload abatement
is to continue. is to continue.
A reporting node MUST NOT update the abatement algorithm in an active A reporting node MUST NOT update the abatement algorithm in an active
OCS entry. OCS entry.
A reporting node MUST update an OCS entry when it wishes to adjust A reporting node MUST update an OCS entry when it wishes to adjust
any abatement algorithm specific parameters, including the reduction any abatement algorithm specific parameters, including the reduction
percentage used for the Loss abatement algorithm. percentage used for the Loss abatement algorithm.
For instance, if the reporting node wishes to change the reduction For instance, if a reporting node wishes to change the reduction
percentage either higher, if the overload condition has worsened, percentage either higher, if the overload condition has worsened,
or lower, if the overload condition has improved, then the or lower, if the overload condition has improved, then the
reporting node would update the appropriate OCS entry. reporting node would update the appropriate OCS entry.
The reporting node MUST update the sequence number associated with A reporting node MUST update the sequence number associated with the
the OCS entry anytime the contents of the OCS entry are changed. OCS entry anytime the contents of the OCS entry are changed. This
This will result in a new sequence number being sent to reacting will result in a new sequence number being sent to reacting nodes,
nodes, instructing the reacting nodes to process the OC-OLR AVP. instructing reacting nodes to process the OC-OLR AVP.
A reporting node SHOULD update an OCS entry with a validity duration A reporting node SHOULD update an OCS entry with a validity duration
of zero ("0") when the overload condition ends. of zero ("0") when the overload condition ends.
If the reporting node knows that the OCS entries in the reacting Note: If a reporting node knows that the OCS entries in the
nodes are near expiration then the reporting node can decide to reacting nodes are near expiration then the reporting node might
delete the OCS entry. decide not to send an OLR with a validity duration of zero.
The reporting node MUST keep an OCS entry with a validity duration of A reporting node MUST keep an OCS entry with a validity duration of
zero ("0") for a period of time long enough to ensure that any non- zero ("0") for a period of time long enough to ensure that any non-
expired reacting node's OCS entry created as a result of the overload expired reacting node's OCS entry created as a result of the overload
condition in the reporting node is deleted. condition in the reporting node is deleted.
4.2.2. Reacting Node Behavior 4.2.2. Reacting Node Behavior
When a reacting node sends a request it MUST determine if that When a reacting node sends a request it MUST determine if that
request matches an active OCS. request matches an active OCS.
If the request matches and active OCS then the reacting node MUST If the request matches an active OCS then the reacting node MUST use
apply abatement treatment on the request. The abatement treatment the overload abatement algorithm indicated in the OCS to determine if
applied depends on the abatement algorithm stored in the OCS. the request is to receive overload abatement treatment.
For the Loss abatement algorithm defined in this specification, see For the Loss abatement algorithm defined in this specification, see
Section 5 for the abatement logic applied. Section 5 for the overload abatement algorithm logic applied.
If the abatement treatment results in throttling of the request and If the overload abatement algorithm selects the request for overload
if the reacting node is an agent then the agent MUST send an abatement treatment then the reacting node MUST apply overload
appropriate error as defined in section Section 7. abatement treatment on the request. The abatement treatment applied
depends on the context of the request.
In the case that the OCS entry validity duration expires or has a If the request is a host-routed request then the reacting node SHOULD
validity duration of zero ("0"), meaning that it the reporting node apply throttling abatement treatment to the request.
has explicitly signaled the end of the overload condition then
If the request is a realm-routed request then the reacting node
SHOULD apply diversion abatement treatment to the request.
If the overload abatement treatment results in throttling of the
request and if the reacting node is an agent then the agent MUST send
an appropriate error as defined in Section 7.
The behavior of reacting nodes that are Diameter endpoints when
throttling requests depends on the application and is outside the
scope of this specification.
In the case that the OCS entry indicated no traffic was to be sent to
the overloaded entity and the validity duration expires or has a
validity duration of zero ("0"), meaning that the reporting node has
explicitly signaled the end of the overload condition then overload
abatement associated with the overload abatement MUST be ended in a abatement associated with the overload abatement MUST be ended in a
controlled fashion. controlled fashion.
4.2.3. Reporting Node Behavior 4.2.3. Reporting Node Behavior
The operation on the reporting node is straight forward. If there is an active OCS entry then a reporting node SHOULD include
the OC-OLR AVP in all answer messages to requests that contain the
If there is an active OCS entry then the reporting node SHOULD OC-Supported-Features AVP and that match the active OCS entry.
include the OC-OLR AVP in all answer messages to requests that
contain the OC-Supported-Features AVP and that match the active OCS
entry.
A request matches if the application-id in the request matches the Note: A request matches if the application-id in the request
application-id in any active OCS entry and if the report-type in matches the application-id in any active OCS entry and if the
the OCS entry matches a report-type supported by the reporting report-type in the OCS entry matches a report-type supported by
node as indicated in the OC-Supported-Features AVP. the reporting node as indicated in the OC-Supported-Features AVP.
The contents of the OC-OLR AVP MUST contain all information necessary The contents of the OC-OLR AVP depend on the selected algorithm.
for the abatement algorithm indicated in the OC-Supported-Features
AVP that is also included in the answer message.
A reporting node MAY choose to not resend an overload report to a A reporting node MAY choose to not resend an overload report to a
reacting node if it can guarantee that this overload report is reacting node if it can guarantee that this overload report is
already active in the reacting node. already active in the reacting node.
Note - In some cases (e.g. when there are one or more agents in Note: In some cases (e.g. when there are one or more agents in the
the path between reporting and reacting nodes, or when overload path between reporting and reacting nodes, or when overload
reports are discarded by reacting nodes) the reporting node may reports are discarded by reacting nodes) a reporting node may not
not be able to guarantee that the reacting node has received the be able to guarantee that the reacting node has received the
report. report.
A reporting node MUST NOT send overload reports of a type that has A reporting node MUST NOT send overload reports of a type that has
not been advertised as supported by the reacting node. not been advertised as supported by the reacting node.
Note that a reacting node advertises support for the host and Note: A reacting node implicitly advertises support for the host
realm report types by including the OC-Supported-Features AVP in and realm report types by including the OC-Supported-Features AVP
the request. Support for other report types must be explicitly in the request. Support for other report types will be explicitly
indicated by new feature bits in the OC-Feature-Vector AVP. indicated by new feature bits in the OC-Feature-Vector AVP.
A reporting node MAY rely on the OC-Validity-Duration AVP values for A reporting node MAY rely on the OC-Validity-Duration AVP values for
the implicit overload control state cleanup on the reacting node. the implicit overload control state cleanup on the reacting node.
However, it is RECOMMENDED that the reporting node always explicitly
indicates the end of a overload condition.
The reporting node SHOULD indicate the end of an overload occurrence A reporting node SHOULD explicitly indicate the end of an overload
by sending a new OLR with OC-Validity-Duration set to a value of zero occurrence by sending a new OLR with OC-Validity-Duration set to a
("0"). The reporting node SHOULD ensure that all reacting nodes value of zero ("0"). The reporting node SHOULD ensure that all
receive the updated overload report. reacting nodes receive the updated overload report.
All OLRs sent have an expiration time calculated by adding the Note: All OLRs sent have an expiration time calculated by adding
validity-duration contained in the OLR to the time the message was the validity-duration contained in the OLR to the time the message
sent. Transit time for the OLR can be safely ignored. The was sent. Transit time for the OLR can be safely ignored. The
reporting node can ensure that all reacting nodes have received reporting node can ensure that all reacting nodes have received
the OLR by continuing to send it in answer messages until the the OLR by continuing to send it in answer messages until the
expiration time for all OLRs sent for that overload condition have expiration time for all OLRs sent for that overload condition have
expired. expired.
When a reporting node sends an OLR, it effectively delegates any When a reporting node sends an OLR, it effectively delegates any
necessary throttling to downstream nodes. Therefore, the reporting necessary throttling to downstream nodes. If the reporting node also
node SHOULD NOT apply throttling to the set of messages to which the locally throttles the same set of messages, the overall number of
OLR applies. That is, the same candidate set of messages SHOULD NOT throttled requests may be higher than intended. Therefore, before
be throttled multiple times. applying local message throttling, a reporting node needs to check if
these messages match existing OCS entries, indicating that these
messages have survived throttling applied by downstream nodes that
have received the related OLR.
However, when the reporting node sends and OLR downstream, it MAY However, even if the set of messages match existing OCS entries, the
still be responsible to apply other abatement methods such as reporting node can still apply other abatement methods such as
diversion. The reporting node might also need to throttle requests diversion. The reporting node might also need to throttle requests
for reasons other then overload. For example, an agent or server for reasons other than overload. For example, an agent or server
might have a configured rate limit for each client, and throttle might have a configured rate limit for each client, and throttle
requests that exceed that limit, even if such requests had already requests that exceed that limit, even if such requests had already
been candidates for throttling by downstream nodes. been candidates for throttling by downstream nodes. The reporting
node also has the option to send new OLRs requesting greater
This document assumes that there is a single source for realm-reports reductions in traffic, reducing the need for local throttling.
for a given realm, or that if multiple nodes can send realm reports,
that each such node has full knowledge of the overload state of the
entire realm. A reacting node cannot distinguish between receiving
realm-reports from a single node, or from multiple nodes.
Editor's Note: There is not yet consensus on the above two A reporting node SHOULD decrease requested overload abatement
paragraphs. Two alternatives are under consideration -- treatment in a controlled fashion to avoid oscillations in traffic.
synchronization of sequence numbers and attribution of reports.
If no consensus is reached then it will be left to be addressed as
an extension.
4.3. Protocol Extensibility 4.3. Protocol Extensibility
The overload control solution can be extended, e.g. with new traffic The DOIC solution can be extended. Types of potential extensions
abatement algorithms, new report types or other new functionality. include new traffic abatement algorithms, new report types or other
new functionality.
When defining a new extension a new feature bit MUST be defined for When defining a new extension that requires new normative behavior,
the OC-Feature-Vector. This feature bit is used to communicate the specification MUST define a new feature for the OC-Feature-
support for the new feature. Vector. This feature bit is used to communicate support for the new
feature.
The extension MAY define new AVPs for use in DOIC Capability The extension MAY define new AVPs for use in DOIC Capability
Announcement and for use in DOIC Overload reporting. These new AVPs Announcement and for use in DOIC Overload reporting. These new AVPs
SHOULD be defined to be extensions to the OC-Supported-Features and SHOULD be defined to be extensions to the OC-Supported-Features and
OC-OLR AVPs defined in this document. OC-OLR AVPs defined in this document.
It should be noted that [RFC6733] defined Grouped AVP extension [RFC6733] defined Grouped AVP extension mechanisms apply. This
mechanisms apply. This allows, for example, defining a new feature allows, for example, defining a new feature that is mandatory to be
that is mandatory to be understood even when piggybacked on an understood even when piggybacked on an existing application.
existing application.
The handling of feature bits in the OC-Feature-Vector AVP that are The handling of feature bits in the OC-Feature-Vector AVP that are
not associated with overload abatement algorithms MUST be specified not associated with overload abatement algorithms MUST be specified
by the extensions that define the features. by the extensions that define the features.
When defining new report type values, the corresponding specification When defining new report type values, the corresponding specification
MUST define the semantics of the new report types and how they affect MUST define the semantics of the new report types and how they affect
the OC-OLR AVP handling. The specification MUST also reserve a the OC-OLR AVP handling. The specification MUST also reserve a
corresponding new feature bit in the OC-Feature-Vector AVP. corresponding new feature bit in the OC-Feature-Vector AVP.
The OC-OLR AVP can be expanded with optional sub-AVPs only if a The OC-OLR AVP can be expanded with optional sub-AVPs only if a
legacy DOIC implementation can safely ignore them without breaking legacy DOIC implementation can safely ignore them without breaking
backward compatibility for the given OC-Report-Type AVP value. If backward compatibility for the given OC-Report-Type AVP value. If
the new sub-AVPs imply new semantics for handling the indicated the new sub-AVPs imply new semantics for handling the indicated
report type, then a new OC-Report-Type AVP value MUST be defined. report type, then a new OC-Report-Type AVP value MUST be defined.
Documents that introduce new report types MUST describe any
limitations on their use across non-supporting agents.
New features (feature bits in the OC-Feature-Vector AVP) and report New features (feature bits in the OC-Feature-Vector AVP) and report
types (in the OC-Report-Type AVP) MUST be registered with IANA. As types (in the OC-Report-Type AVP) MUST be registered with IANA. As
with any Diameter specification, new AVPs MUST also be registered with any Diameter specification, RFC6733 requires all new AVPs to be
with IANA. See Section 8 for the required procedures. registered with IANA. See Section 8 for the required procedures.
5. Loss Algorithm 5. Loss Algorithm
This section documents the Diameter overload loss abatement This section documents the Diameter overload loss abatement
algorithm. algorithm.
5.1. Overview 5.1. Overview
The DOIC specification supports the ability for multiple overload The DOIC specification supports the ability for multiple overload
abatement algorithms to be specified. The abatement algorithm used abatement algorithms to be specified. The abatement algorithm used
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overload report. overload report.
Reporting nodes use a strategy of applying abatement logic to the Reporting nodes use a strategy of applying abatement logic to the
requested percentage of request messages sent (or handled in the case requested percentage of request messages sent (or handled in the case
of agents) by the reacting node that are impacted by the overload of agents) by the reacting node that are impacted by the overload
report. report.
From a conceptual level, the logic at the reacting node could be From a conceptual level, the logic at the reacting node could be
outlined as follows. outlined as follows.
1. An overload report is received and the associated overload state 1. An overload report is received and the associated OCS is either
is either saved or updated (if required) by the reacting node. saved or updated (if required) by the reacting node.
2. A new Diameter request is generated by the application running on 2. A new Diameter request is generated by the application running on
the reacting node. the reacting node.
3. The reacting node determines that an active overload report 3. The reacting node determines that an active overload report
applies to the request, as indicated by the corresponding OCS applies to the request, as indicated by the corresponding OCS
entry. entry.
4. The reacting node determines if abatement should be applied to 4. The reacting node determines if overload abatement treatment
the request. One approach that could be taken for each request should be applied to the request. One approach that could be
is to select a random number between 1 and 100. If the random taken for each request is to select a random number between 1 and
number is less than the indicated reduction percentage then the 100. If the random number is less than the indicated reduction
request is given abatement treatment, otherwise the request is percentage then the request is given abatement treatment,
given normal routing treatment. otherwise the request is given normal routing treatment.
5.2. Reporting Node Behavior 5.2. Reporting Node Behavior
The method a reporting nodes uses to determine the amount of traffic The method a reporting node uses to determine the amount of traffic
reduction required to address an overload condition is an reduction required to address an overload condition is an
implementation decision. implementation decision.
When a reporting node that has selected the loss abatement algorithm When a reporting node that has selected the loss abatement algorithm
determines the need to request a traffic reduction it includes an OC- determines the need to request a reduction in traffic, it includes an
OLR AVP in response messages as described in Section 4.2.3. OC-OLR AVP in response messages as described in Section 4.2.3.
The reporting node MUST indicate a percentage reduction in the OC- When sending the OC-OLR AVP, the reporting node MUST indicate a
Reduction-Percentage AVP. percentage reduction in the OC-Reduction-Percentage AVP.
The reporting node MAY change the reduction percentage in subsequent The reporting node MAY change the reduction percentage in subsequent
overload reports. When doing so the reporting node must conform to overload reports. When doing so the reporting node must conform to
overload report handing specified in Section 4.2.3. overload report handing specified in Section 4.2.3.
When the reporting node determines it no longer needs a reduction in
traffic the reporting node SHOULD send an overload report indicating
the overload report is no longer valid, as specified in
Section 4.2.3.
5.3. Reacting Node Behavior 5.3. Reacting Node Behavior
The method a reacting node uses to determine which request messages The method a reacting node uses to determine which request messages
are given abatement treatment is an implementation decision. are given abatement treatment is an implementation decision.
When receiving an OC-OLR in an answer message where the algorithm When receiving an OC-OLR in an answer message where the algorithm
indicated in the OC-Supported-Features AVP is the loss algorithm, the indicated in the OC-Supported-Features AVP is the loss algorithm, the
reacting node MUST apply abatement treatment to the requested reacting node MUST apply abatement treatment to the requested
percentage of request messages sent. percentage of request messages sent.
Note: the loss algorithm is a stateless algorithm. As a result, Note: The loss algorithm is a stateless algorithm. As a result,
the reacting node does not guarantee that there will be an the reacting node does not guarantee that there will be an
absolute reduction in traffic sent. Rather, it guarantees that absolute reduction in traffic sent. Rather, it guarantees that
the requested percentage of new requests will be given abatement the requested percentage of new requests will be given abatement
treatment. treatment.
When applying overload abatement treatment for the load abatement When applying overload abatement treatment for the load abatement
algorithm, the reacting node MUST abate, either by throttling or algorithm, the reacting node MUST abate the requested percentage of
diversion, the requested percentage of requests that would have requests that would have otherwise been sent to the reporting host or
otherwise been sent to the reporting host or realm. realm.
If reacting node comes out of the 100 percent traffic reduction as a If reacting node comes out of the 100 percent traffic reduction as a
result of the overload report timing out, the following concerns are result of the overload report timing out, the following concerns are
RECOMMENDED to be applied. The reacting node sending the traffic RECOMMENDED to be applied. The reacting node sending the traffic
should be conservative and, for example, first send "probe" messages should be conservative and, for example, first send "probe" messages
to learn the overload condition of the overloaded node before to learn the overload condition of the overloaded node before
converging to any traffic amount/rate decided by the sender. Similar converging to any traffic amount/rate decided by the sender. Similar
concerns apply in all cases when the overload report times out unless concerns apply in all cases when the overload report times out unless
the previous overload report stated 0 percent reduction. the previous overload report stated 0 percent reduction.
If the reacting node does not receive an OLR in messages sent to the If the reacting node does not receive an OLR in messages sent to the
formerly overloaded node then the reacting node SHOULD slowly formerly overloaded node then the reacting node SHOULD slowly
increase the rate of traffic sent to the overloaded node. increase the rate of traffic sent to the overloaded node.
It is suggested that the reacting node decrease the amount of traffic When an active overload report expires, it is suggested that the
given abatement treatment by 20% each second until the reduction is reacting node progressively decrease the amount of traffic given
completely removed and no traffic is given abatement treatment. abatement treatment, until the reduction is completely removed and no
traffic is given abatement treatment.
The goal of this behavior is to reduce the probability of overload The goal of this behavior is to reduce the probability of overload
condition thrashing where an immediate transition from 100% condition thrashing where an immediate transition from 100%
reduction to 0% reduction results in the reporting node moving reduction to 0% reduction results in the reporting node moving
quickly back into an overload condition. quickly back into an overload condition.
6. Attribute Value Pairs 6. Attribute Value Pairs
This section describes the encoding and semantics of the Diameter This section describes the encoding and semantics of the Diameter
Overload Indication Attribute Value Pairs (AVPs) defined in this Overload Indication Attribute Value Pairs (AVPs) defined in this
skipping to change at page 23, line 39 skipping to change at page 25, line 20
A new application specification can incorporate the overload control A new application specification can incorporate the overload control
mechanism specified in this document by making it mandatory to mechanism specified in this document by making it mandatory to
implement for the application and referencing this specification implement for the application and referencing this specification
normatively. It is the responsibility of the Diameter application normatively. It is the responsibility of the Diameter application
designers to define how overload control mechanisms works on that designers to define how overload control mechanisms works on that
application. application.
6.1. OC-Supported-Features AVP 6.1. OC-Supported-Features AVP
The OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and The OC-Supported-Features AVP (AVP code TBD1) is of type Grouped and
serves two purposes. First, it announces a node's support for the serves two purposes. First, it announces a node's support for the
DOIC solution in general. Second, it contains the description of the DOIC solution in general. Second, it contains the description of the
supported DOIC features of the sending node. The OC-Supported- supported DOIC features of the sending node. The OC-Supported-
Features AVP MUST be included in every Diameter request message a Features AVP MUST be included in every Diameter request message a
DOIC supporting node sends. DOIC supporting node sends.
OC-Supported-Features ::= < AVP Header: TBD1 > OC-Supported-Features ::= < AVP Header: TBD1 >
[ OC-Feature-Vector ] [ OC-Feature-Vector ]
* [ AVP ] * [ AVP ]
The OC-Feature-Vector sub-AVP is used to announce the DOIC features The OC-Feature-Vector sub-AVP is used to announce the DOIC features
supported by the DOIC node, in the form of a flag bits field in which supported by the DOIC node, in the form of a flag-bits field in which
each bit announces one feature or capability supported by the node each bit announces one feature or capability supported by the node
(see Section 6.2). The absence of the OC-Feature-Vector AVP (see Section 6.2). The absence of the OC-Feature-Vector AVP
indicates that only the default traffic abatement algorithm described indicates that only the default traffic abatement algorithm described
in this specification is supported. in this specification is supported.
6.2. OC-Feature-Vector AVP 6.2. OC-Feature-Vector AVP
The OC-Feature-Vector AVP (AVP code TBD6) is type of Unsigned64 and The OC-Feature-Vector AVP (AVP code TBD6) is of type Unsigned64 and
contains a 64 bit flags field of announced capabilities of a DOIC contains a 64 bit flags field of announced capabilities of a DOIC
node. The value of zero (0) is reserved. node. The value of zero (0) is reserved.
The OC-Feature-Vector sub-AVP is used to announce the DOIC features
supported by the DOIC node, in the form of a flag-bits field in which
each bit announces one feature or capability supported by the node
(see Section 6.2). The absence of the OC-Feature-Vector AVP
indicates that only the default traffic abatement algorithm described
in this specification is supported.
The following capabilities are defined in this document: The following capabilities are defined in this document:
OLR_DEFAULT_ALGO (0x0000000000000001) OLR_DEFAULT_ALGO (0x0000000000000001)
When this flag is set by the DOIC node it means that the default When this flag is set by the a DOIC reacting node it means that
traffic abatement (loss) algorithm is supported. the default traffic abatement (loss) algorithm is supported. When
this flag is set by a DOIC reporting node it means that the loss
algorithm will be used for requested overload abatement.
6.3. OC-OLR AVP 6.3. OC-OLR AVP
The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the The OC-OLR AVP (AVP code TBD2) is of type Grouped and contains the
information necessary to convey an overload report on an overload information necessary to convey an overload report on an overload
condition at the reporting node. The OC-OLR AVP does not explicitly condition at the reporting node. The OC-OLR AVP does not explicitly
contain all information needed by the reacting node to decide whether contain all information needed by the reacting node to decide whether
a subsequent request must undergo a throttling process with the a subsequent request must undergo abatement using the received
received reduction percentage. The value of the OC-Report-Type AVP reduction percentage. The value of the OC-Report-Type AVP within the
within the OC-OLR AVP indicates which implicit information is OC-OLR AVP indicates which implicit information is relevant for this
relevant for this decision (see Section 6.6). The application the decision (see Section 6.6). The application the OC-OLR AVP applies
OC-OLR AVP applies to is the same as the Application-Id found in the to is the same as the Application-Id found in the Diameter message
Diameter message header. The host or realm the OC-OLR AVP concerns header. The host or realm the OC-OLR AVP concerns is determined from
is determined from the Origin-Host AVP and/or Origin-Realm AVP found the Origin-Host AVP and/or Origin-Realm AVP found in the
in the encapsulating Diameter command. The OC-OLR AVP is intended to encapsulating Diameter command. The OC-OLR AVP is intended to be
be sent only by a reporting node. sent only by a reporting node.
OC-OLR ::= < AVP Header: TBD2 > OC-OLR ::= < AVP Header: TBD2 >
< OC-Sequence-Number > < OC-Sequence-Number >
< OC-Report-Type > < OC-Report-Type >
[ OC-Reduction-Percentage ] [ OC-Reduction-Percentage ]
[ OC-Validity-Duration ] [ OC-Validity-Duration ]
* [ AVP ] * [ AVP ]
Note that if a Diameter command were to contain multiple OC-OLR AVPs
they all MUST have different OC-Report-Type AVP value. OC-OLR AVPs
with unknown values SHOULD be silently discarded by reacting nodes
and the event SHOULD be logged.
6.4. OC-Sequence-Number AVP 6.4. OC-Sequence-Number AVP
The OC-Sequence-Number AVP (AVP code TBD3) is type of Unsigned64. The OC-Sequence-Number AVP (AVP code TBD3) is of type Unsigned64.
Its usage in the context of overload control is described in Its usage in the context of overload control is described in
Section 4.2. Section 4.2.
From the functionality point of view, the OC-Sequence-Number AVP MUST From the functionality point of view, the OC-Sequence-Number AVP is
be used as a non-volatile increasing counter for a sequence of used as a non-volatile increasing counter for a sequence of overload
overload reports between two DOIC nodes for the same overload reports between two DOIC nodes for the same overload occurrence. The
occurrence. The sequence number is only required to be unique sequence number is only required to be unique between two DOIC nodes.
between two DOIC nodes. Sequence numbers are treated in a uni- Sequence numbers are treated in a uni-directional manner, i.e. two
directional manner, i.e. two sequence numbers on each direction sequence numbers on each direction between two DOIC nodes are not
between two DOIC nodes are not related or correlated. related or correlated.
6.5. OC-Validity-Duration AVP 6.5. OC-Validity-Duration AVP
The OC-Validity-Duration AVP (AVP code TBD4) is type of Unsigned32 The OC-Validity-Duration AVP (AVP code TBD4) is of type Unsigned32
and indicates in milliseconds the validity time of the overload and indicates in milliseconds the validity time of the overload
report. The number of milliseconds is measured after reception of report. The number of milliseconds is measured after reception of
the first OC-OLR AVP with a given value of OC-Sequence-Number AVP. the first OC-OLR AVP with a given value of OC-Sequence-Number AVP.
The default value for the OC-Validity-Duration AVP is 5000 (i.e., 5 The default value for the OC-Validity-Duration AVP is 30000 (i.e.; 30
seconds). When the OC-Validity-Duration AVP is not present in the seconds). When the OC-Validity-Duration AVP is not present in the
OC-OLR AVP, the default value applies. Validity duration with values OC-OLR AVP, the default value applies.
above 86400 (i.e.; 24 hours) MUST NOT be used. Invalid duration
values are treated as if the OC-Validity-Duration AVP were not
present and result in the default value being used.
Editor's note: There is an open discussion on whether to have an
upper limit on the OC-Validity-Duration value, beyond that which can
be indicated by an Unsigned32.
A timeout of the overload report has specific concerns that need to
be taken into account by the DOIC node acting on the earlier received
overload report(s). Section 6.7 discusses the impacts of timeout in
the scope of the traffic abatement algorithms.
6.6. OC-Report-Type AVP 6.6. OC-Report-Type AVP
The OC-Report-Type AVP (AVP code TBD5) is type of Enumerated. The The OC-Report-Type AVP (AVP code TBD5) is of type Enumerated. The
value of the AVP describes what the overload report concerns. The value of the AVP describes what the overload report concerns. The
following values are initially defined: following values are initially defined:
0 A host report. The overload treatment should apply to requests HOST_REPORT 0 The overload report is for a host. Overload abatement
for which all of the following conditions are true: treatment applies to host-routed requests.
Either the Destination-Host AVP is present in the request and its
value matches the value of the Origin-Host AVP of the received
message that contained the OC-OLR AVP; or the Destination-Host is
not present in the request but the value of the peer identity
associated with the connection used to send the request matches
the value of the Origin-Host AVP of the received message that
contained the OC-OLR AVP.
The value of the Destination-Realm AVP in the request matches the
value of the Origin-Realm AVP of the received message that
contained the OC-OLR AVP.
The value of the Application-ID in the Diameter Header of the
request matches the value of the Application-ID of the Diameter
Header of the received message that contained the OC-OLR AVP.
1 A realm report. The overload treatment should apply to requests
for which all of the following conditions are true:
The Destination-Host AVP is absent in the requestand the value of
the peer identity associated with the connection used to send the
request does not match a server that could serve the request.
The value of the Destination-Realm AVP in the request matches the
value of the Origin-Realm AVP of the received message that
contained the OC-OLR AVP.
The value of the Application-ID in the Diameter Header of the
request matches the value of the Application-ID of the Diameter
Header of the received message that contained the OC-OLR AVP.
The OC-Report-Type AVP is envisioned to be useful for situations REALM_REPORT 1 The overload report is for a realm. Overload
where a reacting node needs to apply different overload treatments abatement treatment applies to realm-routed requests.
for different overload contexts. For example, the reacting node(s)
might need to throttle differently requests sent to a specific server
(identified by the Destination-Host AVP in the request) and requests
that can be handled by any server in a realm.
6.7. OC-Reduction-Percentage AVP 6.7. OC-Reduction-Percentage AVP
The OC-Reduction-Percentage AVP (AVP code TBD8) is type of Unsigned32 The OC-Reduction-Percentage AVP (AVP code TBD8) is of type Unsigned32
and describes the percentage of the traffic that the sender is and describes the percentage of the traffic that the sender is
requested to reduce, compared to what it otherwise would send. The requested to reduce, compared to what it otherwise would send. The
OC-Reduction-Percentage AVP applies to the default (loss) algorithm OC-Reduction-Percentage AVP applies to the default (loss) algorithm
specified in this specification. However, the AVP can be reused for specified in this specification. However, the AVP can be reused for
future abatement algorithms, if its semantics fit into the new future abatement algorithms, if its semantics fit into the new
algorithm. algorithm.
The value of the Reduction-Percentage AVP is between zero (0) and one The value of the Reduction-Percentage AVP is between zero (0) and one
hundred (100). Values greater than 100 are ignored. The value of hundred (100). Values greater than 100 are ignored. The value of
100 means that all traffic is to be throttled, i.e. the reporting 100 means that all traffic is to be throttled, i.e. the reporting
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hundred (100). Values greater than 100 are ignored. The value of hundred (100). Values greater than 100 are ignored. The value of
100 means that all traffic is to be throttled, i.e. the reporting 100 means that all traffic is to be throttled, i.e. the reporting
node is under a severe load and ceases to process any new messages. node is under a severe load and ceases to process any new messages.
The value of 0 means that the reporting node is in a stable state and The value of 0 means that the reporting node is in a stable state and
has no need for the reacting node to apply any traffic abatement. has no need for the reacting node to apply any traffic abatement.
The default value of the OC-Reduction-Percentage AVP is 0. When the The default value of the OC-Reduction-Percentage AVP is 0. When the
OC-Reduction-Percentage AVP is not present in the overload report, OC-Reduction-Percentage AVP is not present in the overload report,
the default value applies. the default value applies.
6.8. Attribute Value Pair flag rules 6.8. Attribute Value Pair flag rules
+---------+ +---------+
|AVP flag | |AVP flag |
|rules | |rules |
+----+----+ +----+----+
AVP Section | |MUST| AVP Section | |MUST|
Attribute Name Code Defined Value Type |MUST| NOT| Attribute Name Code Defined Value Type |MUST| NOT|
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Supported-Features TBD1 x.x Grouped | | V | |OC-Supported-Features TBD1 6.1 Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-OLR TBD2 x.x Grouped | | V | |OC-OLR TBD2 6.3 Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Sequence-Number TBD3 x.x Unsigned64 | | V | |OC-Sequence-Number TBD3 6.4 Unsigned64 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Validity-Duration TBD4 x.x Unsigned32 | | V | |OC-Validity-Duration TBD4 6.5 Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Report-Type TBD5 x.x Enumerated | | V | |OC-Report-Type TBD5 6.6 Enumerated | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Reduction | | | |OC-Reduction | | |
| -Percentage TBD8 x.x Unsigned32 | | V | | -Percentage TBD8 6.7 Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Feature-Vector TBD6 x.x Unsigned64 | | V | |OC-Feature-Vector TBD6 6.2 Unsigned64 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
As described in the Diameter base protocol [RFC6733], the M-bit As described in the Diameter base protocol [RFC6733], the M-bit usage
setting for a given AVP is relevant to an application and each for a given AVP in a given command may be defined by the
command within that application that includes the AVP. application..
The Diameter overload control AVPs SHOULD always be sent with the
M-bit cleared when used within existing Diameter applications to
avoid backward compatibility issues. Otherwise, when reused in newly
defined Diameter applications, the DOC related AVPs SHOULD have the
M-bit set.
7. Error Response Codes 7. Error Response Codes
When a DOIC node rejects a Diameter request due to overload, the DOIC When a DOIC node rejects a Diameter request due to overload, the DOIC
node MUST select an appropriate error response code. This node MUST select an appropriate error response code. This
determination is made based on the probability of the request determination is made based on the probability of the request
succeeding if retried on a different path. succeeding if retried on a different path.
A reporting node rejecting a Diameter request due to an overload A reporting node rejecting a Diameter request due to an overload
condition SHOULD send a DIAMETER-TOO-BUSY error response, if it can condition SHOULD send a DIAMETER-TOO-BUSY error response, if it can
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SHOULD be used. Retrying would consume valuable resources during an SHOULD be used. Retrying would consume valuable resources during an
occurrence of overload. occurrence of overload.
For instance, if the request arrived at the reporting node without For instance, if the request arrived at the reporting node without
a Destination-Host AVP then the reporting node might determine a Destination-Host AVP then the reporting node might determine
that there is an alternative Diameter node that could successfully that there is an alternative Diameter node that could successfully
process the request and that retrying the transaction would not process the request and that retrying the transaction would not
negatively impact the reporting node. DIAMETER_TOO_BUSY would be negatively impact the reporting node. DIAMETER_TOO_BUSY would be
sent in this case. sent in this case.
For instance, if the request arrived at the reporting node with a If the request arrived at the reporting node with a Destination-
Destination-Host AVP populated with its own Diameter identity then Host AVP populated with its own Diameter identity then the
the reporting node can assume that retrying the request would reporting node can assume that retrying the request would result
result in it coming to the same reporting node. in it coming to the same reporting node.
DIAMETER_UNABLE_TO_COMPLY would be sent in this case. DIAMETER_UNABLE_TO_COMPLY would be sent in this case.
A second example is when an agent that supports the DOIC solution A second example is when an agent that supports the DOIC solution
is performing the role of a reacting node for a non supporting is performing the role of a reacting node for a non supporting
client. Requests that are rejected as a result of DOIC throttling client. Requests that are rejected as a result of DOIC throttling
by the agent in this scenario would generally be rejected with a by the agent in this scenario would generally be rejected with a
DIAMETER_UNABLE_TO_COMPLY response code. DIAMETER_UNABLE_TO_COMPLY response code.
8. IANA Considerations 8. IANA Considerations
8.1. AVP codes 8.1. AVP codes
New AVPs defined by this specification are listed in Section 6. All New AVPs defined by this specification are listed in Section 6. All
AVP codes allocated from the 'Authentication, Authorization, and AVP codes are allocated from the 'Authentication, Authorization, and
Accounting (AAA) Parameters' AVP Codes registry. Accounting (AAA) Parameters' AVP Codes registry.
8.2. New registries 8.2. New registries
Two new registries are needed under the 'Authentication, Two new registries are needed under the 'Authentication,
Authorization, and Accounting (AAA) Parameters' registry. Authorization, and Accounting (AAA) Parameters' registry.
Section 6.2 defines a new "Overload Control Feature Vector" registry A new "Overload Control Feature Vector" registry is required. The
including the initial assignments. New values can be added into the registry must contain the following:
registry using the Specification Required policy [RFC5226]. See
Section 6.2 for the initial assignment in the registry.
Section 6.6 defines a new "Overload Report Type" registry with its Feature Vector Value
initial assignments. New types can be added using the Specification
Required policy [RFC5226]. Specification - the specification that defines the new value.
See Section 6.2 for the initial Feature Vector Value in the registry.
This specification is the specification defining the value. New
values can be added into the registry using the Specification
Required policy. [RFC5226].
A new "Overload Report Type" registry is required. The registry must
contain the following:
Report Type Value
Specification - the specification that defines the new value.
See Section 6.2 for the initial assignment in the registry. New
types can be added using the Specification Required policy [RFC5226].
9. Security Considerations 9. Security Considerations
This mechanism gives Diameter nodes the ability to request that DOIC gives Diameter nodes the ability to request that downstream
downstream nodes send fewer Diameter requests. Nodes do this by nodes send fewer Diameter requests. Nodes do this by exchanging
exchanging overload reports that directly affect this reduction. overload reports that directly effect this reduction. This exchange
This exchange is potentially subject to multiple methods of attack, is potentially subject to multiple methods of attack, and has the
and has the potential to be used as a Denial-of-Service (DoS) attack potential to be used as a Denial-of-Service (DoS) attack vector.
vector.
Overload reports may contain information about the topology and Overload reports may contain information about the topology and
current status of a Diameter network. This information is current status of a Diameter network. This information is
potentially sensitive. Network operators may wish to control potentially sensitive. Network operators may wish to control
disclosure of overload reports to unauthorized parties to avoid its disclosure of overload reports to unauthorized parties to avoid its
use for competitive intelligence or to target attacks. use for competitive intelligence or to target attacks.
Diameter does not include features to provide end-to-end Diameter does not include features to provide end-to-end
authentication, integrity protection, or confidentiality. This may authentication, integrity protection, or confidentiality. This may
cause complications when sending overload reports between non- cause complications when sending overload reports between non-
adjacent nodes. adjacent nodes.
9.1. Potential Threat Modes 9.1. Potential Threat Modes
The Diameter protocol involves transactions in the form of requests The Diameter protocol involves transactions in the form of requests
and answers exchanged between clients and servers. These clients and and answers exchanged between clients and servers. These clients and
servers may be peers, that is,they may share a direct transport (e.g. servers may be peers, that is, they may share a direct transport
TCP or SCTP) connection, or the messages may traverse one or more (e.g. TCP or SCTP) connection, or the messages may traverse one or
intermediaries, known as Diameter Agents. Diameter nodes use TLS, more intermediaries, known as Diameter Agents. Diameter nodes use
DTLS, or IPSec to authenticate peers, and to provide confidentiality TLS, DTLS, or IPsec to authenticate peers, and to provide
and integrity protection of traffic between peers. Nodes can make confidentiality and integrity protection of traffic between peers.
authorization decisions based on the peer identities authenticated at Nodes can make authorization decisions based on the peer identities
the transport layer. authenticated at the transport layer.
When agents are involved, this presents an effectively hop-by-hop When agents are involved, this presents an effectively transitive
trust model. That is, a Diameter client or server can authorize an trust model. That is, a Diameter client or server can authorize an
agent for certain actions, but it must trust that agent to make agent for certain actions, but it must trust that agent to make
appropriate authorization decisions about its peers, and so on. appropriate authorization decisions about its peers, and so on.
Since confidentiality and integrity protection occurs at the Since confidentiality and integrity protection occurs at the
transport layer. Agents can read, and perhaps modify, any part of a transport layer, agents can read, and perhaps modify, any part of a
Diameter message, including an overload report. Diameter message, including an overload report.
There are several ways an attacker might attempt to exploit the There are several ways an attacker might attempt to exploit the
overload control mechanism. An unauthorized third party might inject overload control mechanism. An unauthorized third party might inject
an overload report into the network. If this third party is upstream an overload report into the network. If this third party is upstream
of an agent, and that agent fails to apply proper authorization of an agent, and that agent fails to apply proper authorization
policies, downstream nodes may mistakenly trust the report. This policies, downstream nodes may mistakenly trust the report. This
attack is at least partially mitigated by the assumption that nodes attack is at least partially mitigated by the assumption that nodes
include overload reports in Diameter answers but not in requests. include overload reports in Diameter answers but not in requests.
This requires an attacker to have knowledge of the original request This requires an attacker to have knowledge of the original request
in order to construct a response. Therefore, implementations SHOULD in order to construct an answer. Such an answer would also need to
validate that an answer containing an overload report is a properly arrive at a Diameter node via a protected transport connection.
constructed response to a pending request prior to acting on the Therefore, implementations MUST validate that an answer containing an
overload report. overload report is a properly constructed response to a pending
request prior to acting on the overload report, and that the answer
was received via an appropriate transport connection.
A similar attack involves an otherwise authorized Diameter node that A similar attack involves a compromised but otherwise authorized node
sends an inappropriate overload report. For example, a server for that sends an inappropriate overload report. For example, a server
the realm "example.com" might send an overload report indicating that for the realm "example.com" might send an overload report indicating
a competitor's realm "example.net" is overloaded. If other nodes act that a competitor's realm "example.net" is overloaded. If other
on the report, they may falsely believe that "example.net" is nodes act on the report, they may falsely believe that "example.net"
overloaded, effectively reducing that realm's capacity. Therefore, is overloaded, effectively reducing that realm's capacity.
it's critical that nodes validate that an overload report received Therefore, it's critical that nodes validate that an overload report
from a peer actually falls within that peer's responsibility before received from a peer actually falls within that peer's responsibility
acting on the report or forwarding the report to other peers. For before acting on the report or forwarding the report to other peers.
example, an overload report from a peer that applies to a realm not For example, an overload report from a peer that applies to a realm
handled by that peer is suspect. not handled by that peer is suspect.
An attacker might use the information in an overload report to assist This attack is partially mitigated by the fact that the
in certain attacks. For example, an attacker could use information application, as well as host and realm, for a given OLR is
about current overload conditions to time a DoS attack for maximum determined implicitly by respective AVPs in the enclosing answer.
effect, or use subsequent overload reports as a feedback mechanism to If a reporting node modifies any of those AVPs, the enclosing
learn the results of a previous or ongoing attack. transaction will also be affected.
9.2. Denial of Service Attacks 9.2. Denial of Service Attacks
Diameter overload reports can cause a node to cease sending some or Diameter overload reports, especially realm-reports, can cause a node
all Diameter requests for an extended period. This makes them a to cease sending some or all Diameter requests for an extended
tempting vector for DoS tacks. Furthermore, since Diameter is almost period. This makes them a tempting vector for DoS attacks.
always used in support of other protocols, a DoS attack on Diameter Furthermore, since Diameter is almost always used in support of other
is likely to impact those protocols as well. Therefore, Diameter protocols, a DoS attack on Diameter is likely to impact those
nodes MUST NOT honor or forward overload reports from unauthorized or protocols as well. Therefore, Diameter nodes MUST NOT honor or
otherwise untrusted sources. forward OLRs received from peers that are not trusted to send them.
9.3. Non-Compliant Nodes An attacker might use the information in an OLR to assist in DoS
attacks. For example, an attacker could use information about
current overload conditions to time an attack for maximum effect, or
use subsequent overload reports as a feedback mechanism to learn the
results of a previous or ongoing attack. Operators need the ability
to ensure that OLRs are not leaked to untrusted parties.
When a Diameter node sends an overload report, it cannot assume that 9.3. Non-Compliant Nodes
all nodes will comply. A non-compliant node might continue to send
requests with no reduction in load. Requirement 28 [RFC7068]
indicates that the overload control solution cannot assume that all
Diameter nodes in a network are necessarily trusted, and that
malicious nodes not be allowed to take advantage of the overload
control mechanism to get more than their fair share of service.
In the absence of an overload control mechanism, Diameter nodes need In the absence of an overload control mechanism, Diameter nodes need
to implement strategies to protect themselves from floods of to implement strategies to protect themselves from floods of
requests, and to make sure that a disproportionate load from one requests, and to make sure that a disproportionate load from one
source does not prevent other sources from receiving service. For source does not prevent other sources from receiving service. For
example, a Diameter server might reject a certain percentage of example, a Diameter server might throttle a certain percentage of
requests from sources that exceed certain limits. Overload control requests from sources that exceed certain limits. Overload control
can be thought of as an optimization for such strategies, where can be thought of as an optimization for such strategies, where
downstream nodes never send the excess requests in the first place. downstream nodes never send the excess requests in the first place.
However, the presence of an overload control mechanism does not However, the presence of an overload control mechanism does not
remove the need for these other protection strategies. remove the need for these other protection strategies.
When a Diameter node sends an overload report, it cannot assume that
all nodes will comply, even if they indicate support for DOIC. A
non-compliant node might continue to send requests with no reduction
in load. Such non-compliance could be done accidentally, or
maliciously to gain an unfair advantage over compliant nodes.
Requirement 28 [RFC7068] indicates that the overload control solution
cannot assume that all Diameter nodes in a network are trusted, and
that malicious nodes not be allowed to take advantage of the overload
control mechanism to get more than their fair share of service.
9.4. End-to End-Security Issues 9.4. End-to End-Security Issues
The lack of end-to-end security features makes it far more difficult The lack of end-to-end integrity features makes it difficult to
to establish trust in overload reports that originate from non- establish trust in overload reports received from non-adjacent nodes.
adjacent nodes. Any agents in the message path may insert or modify Any agents in the message path may insert or modify overload reports.
overload reports. Nodes must trust that their adjacent peers perform Nodes must trust that their adjacent peers perform proper checks on
proper checks on overload reports from their peers, and so on, overload reports from their peers, and so on, creating a transitive-
creating a transitive-trust requirement extending for potentially trust requirement extending for potentially long chains of nodes.
long chains of nodes. Network operators must determine if this Network operators must determine if this transitive trust requirement
transitive trust requirement is acceptable for their deployments. is acceptable for their deployments. Nodes supporting Diameter
Nodes supporting Diameter overload control MUST give operators the overload control MUST give operators the ability to select which
ability to select which peers are trusted to deliver overload peers are trusted to deliver overload reports, and whether they are
reports, and whether they are trusted to forward overload reports trusted to forward overload reports from non-adjacent nodes. DOIC
from non-adjacent nodes. nodes MUST strip DOIC AVPs from messages received from peers that are
not trusted for DOIC purposes.
The lack of end-to-end confidentiality protection means that any The lack of end-to-end confidentiality protection means that any
Diameter agent in the path of an overload report can view the Diameter agent in the path of an overload report can view the
contents of that report. In addition to the requirement to select contents of that report. In addition to the requirement to select
which peers are trusted to send overload reports, operators MUST be which peers are trusted to send overload reports, operators MUST be
able to select which peers are authorized to receive reports. A node able to select which peers are authorized to receive reports. A node
MUST not send an overload report to a peer not authorized to receive MUST not send an overload report to a peer not authorized to receive
it. Furthermore, an agent MUST remove any overload reports that it. Furthermore, an agent MUST remove any overload reports that
might have been inserted by other nodes before forwarding a Diameter might have been inserted by other nodes before forwarding a Diameter
message to a peer that is not authorized to receive overload reports. message to a peer that is not authorized to receive overload reports.
A DOIC node cannot always automatically detect that a peer also
supports DOIC. For example, a node might have a peer that is a
non-supporting agent. If nodes on the other side of that agent
send OC-Supported-Features AVPs, the agent is likely to forward
them as unknown AVPs. Messages received across the non-supporting
agent may be indistinguishable from messages received across a
DOIC supporting agent, giving the false impression that the non-
supporting agent actually supports DOIC. This complicates the
transitive-trust nature of DOIC. Operators need to be careful to
avoid situations where a non-supporting agent is mistakenly
trusted to enforce DOIC related authorization policies.
At the time of this writing, the DIME working group is studying At the time of this writing, the DIME working group is studying
requirements for adding end-to-end security requirements for adding end-to-end security features
[I-D.ietf-dime-e2e-sec-req] features to Diameter. These features, [I-D.ietf-dime-e2e-sec-req] to Diameter. These features, when they
when they become available, might make it easier to establish trust become available, might make it easier to establish trust in non-
in non-adjacent nodes for overload control purposes. Readers should adjacent nodes for overload control purposes. Readers should be
be reminded, however, that the overload control mechanism encourages reminded, however, that the overload control mechanism encourages
Diameter agents to modify AVPs in, or insert additional AVPs into, Diameter agents to modify AVPs in, or insert additional AVPs into,
existing messages that are originated by other nodes. If end-to-end existing messages that are originated by other nodes. If end-to-end
security is enabled, there is a risk that such modification could security is enabled, there is a risk that such modification could
violate integrity protection. The details of using any future violate integrity protection. The details of using any future
Diameter end-to-end security mechanism with overload control will Diameter end-to-end security mechanism with overload control will
require careful consideration, and are beyond the scope of this require careful consideration, and are beyond the scope of this
document. document.
10. Contributors 10. Contributors
skipping to change at page 33, line 30 skipping to change at page 34, line 52
[RFC7068] McMurry, E. and B. Campbell, "Diameter Overload Control [RFC7068] McMurry, E. and B. Campbell, "Diameter Overload Control
Requirements", RFC 7068, November 2013. Requirements", RFC 7068, November 2013.
[S13] 3GPP, , "ETSI TS 129 272 V11.9.0", December 2012. [S13] 3GPP, , "ETSI TS 129 272 V11.9.0", December 2012.
Appendix A. Issues left for future specifications Appendix A. Issues left for future specifications
The base solution for the overload control does not cover all The base solution for the overload control does not cover all
possible use cases. A number of solution aspects were intentionally possible use cases. A number of solution aspects were intentionally
left for future specification and protocol work. left for future specification and protocol work. The following sub-
sections define some of the potential extensions to the DOIC
solution.
A.1. Additional traffic abatement algorithms A.1. Additional traffic abatement algorithms
This specification describes only means for a simple loss based This specification describes only means for a simple loss based
algorithm. Future algorithms can be added using the designed algorithm. Future algorithms can be added using the designed
solution extension mechanism. The new algorithms need to be solution extension mechanism. The new algorithms need to be
registered with IANA. See Sections 6.1 and 8 for the required IANA registered with IANA. See Sections 6.1 and 8 for the required IANA
steps. steps.
A.2. Agent Overload A.2. Agent Overload
This specification focuses on Diameter endpoint (server or client) This specification focuses on Diameter endpoint (server or client)
overload. A separate extension will be required to outline the overload. A separate extension will be required to outline the
handling of the case of agent overload. handling of the case of agent overload.
A.3. New Error Diagnostic AVP A.3. New Error Diagnostic AVP
The proposal was made to add a new Error Diagnostic AVP to supplement This specification indicates the use of existing error messages when
the error responces to be able to indicate that overload was the nodes reject requests due to overload. The DIME working group is
reason for the rejection of the message. considering defining additional error codes or AVPs to indicate that
overload was the reason for the rejection of the message.
Appendix B. Deployment Considerations Appendix B. Deployment Considerations
Non supporting agents Non Supporting Agents
Due to the way that realm-routed requests are handled in Diameter Due to the way that realm-routed requests are handled in Diameter
networks, with the server selection for the request done by an networks with the server selection for the request done by an
agent, it is recommended that deployments enable all agents that agent, network operators should enable DOIC at agents that perform
do server selection to support the DOIC solution prior to enabling server selection first.
the DOIC solution in the Diameter network.
Topology hiding interactions Topology Hiding Interactions
There exist proxies that implement what is referred to as Topology There exist proxies that implement what is referred to as Topology
Hiding. This can include cases where the agent modifies the Hiding. This can include cases where the agent modifies the
Origin-Host in answer messages. The behavior of the DOIC solution Origin-Host in answer messages. The behavior of the DOIC solution
is not well understood when this happens. As such, the DOIC is not well understood when this happens. As such, the DOIC
solution does not address this scenario. solution does not address this scenario.
Appendix C. Requirements Conformance Analysis Appendix C. Requirements Conformance Analysis
This section contains the result of an analysis of the DOIC solutions This section contains the result of an analysis of the DOIC solutions
conformance to the requirements defined in [RFC7068]. conformance to the requirements defined in [RFC7068].
To be completed. C.1. Deferred Requirements
The 3GPP has adopted an early version of this document as normative
references in various Diameter related specifications to support the
overload control mechanism in their release 12 framework. The DIME
working group has therefore decided to defer certain requirements in
order to complete the design of an extensible, generic solution
before the deadline scheduled by the 3GPP for the completion of the
release 12 protocol work by the end of 2014. The deferred work
includes the following:
o Agent Overload - The ability for an agent to report an overload
condition of the agent itself.
o Load Information - The ability for a node to report its load level
when not overloaded.
At the time of this writing, DIME has begun separate work efforts for
these requirements.
C.2. Detection of non-supporting Intermediaries
The DOIC mechanism as currently defined does not allow supporting
nodes to automatically determine whether OC-Supported-Features or OC-
OLR AVPs are originated by a peer node, or by a non-peer node and
sent across a non-supporting peer. This makes it impossible to
detect the presence of non-supporting nodes between supporting nodes,
except by configuration. The working group determined that such a
configuration requirement is acceptable.
This limits full compliance with certain requirements related to the
limitation of new configuration, deployment in environments with
mixed support, operating across non-supporting agents, and
authorization.
C.3. Implicit Application Indication
The working group elected to determine the application for an
overload report from that of the enclosing message. This prevents
sending an OLR for an application when there are no transactions for
that application.
As a consequence, DOIC does not comply with the requirement to be
able to report overload information across quiescent connections.
DOIC does not fully comply with requirements to operate on up-to-date
information, since if an OLR causes all transactions to stop for an
application, the only way traffic will resume is for the OLR to
expire.
C.4. Stateless Operation
RFC7068 explicitly discourages the sending of OLRs in every answer
message, as part of the requirement to avoid additional work for
overloaded nodes. DOIC recommends exactly that behavior during
active overload conditions. The working group determined that doing
otherwise would reduce reliability and increase statefulness. (Note
that DOIC does allow nodes to avoid sending OLRs in every answer if
they have some other method of ensuring that OLRs get to all relevant
reacting nodes.)
C.5. No New Vulnerabilities
The working group believes that DOIC is compliant with the
requirement to avoid introducing new vulnerabilities. However, this
requirement may warrant an early security expert review.
C.6. Detailed Requirements
[RFC Editor: Please remove this section and subsections prior to
publication as an RFC.]
C.6.1. General
REQ 1: The solution MUST provide a communication method for Diameter
nodes to exchange load and overload information.
*Partially Compliant*. The mechanism uses new AVPs
piggybacked on existing Diameter messages to exchange
overload information. It does not currently support "load"
information or the ability to report overload of an agent.
These have been left for future extensions.
REQ 2: The solution MUST allow Diameter nodes to support overload
control regardless of which Diameter applications they
support. Diameter clients and agents must be able to use the
received load and overload information to support graceful
behavior during an overload condition. Graceful behavior
under overload conditions is best described by REQ 3.
*Partially Compliant*. The DOIC AVPs can be used in any
application that allows the extension of AVPs. However,
"load" information is not currently supported.
REQ 3: The solution MUST limit the impact of overload on the overall
useful throughput of a Diameter server, even when the
incoming load on the network is far in excess of its
capacity. The overall useful throughput under load is the
ultimate measure of the value of a solution.
*Compliant*. DOIC provides information that nodes can use to
reduce the impact of overload.
REQ 4: Diameter allows requests to be sent from either side of a
connection, and either side of a connection may have need to
provide its overload status. The solution MUST allow each
side of a connection to independently inform the other of its
overload status.
*Compliant*. DOIC AVPs can be included regardless of
transaction "direction"
REQ 5: Diameter allows nodes to determine their peers via dynamic
discovery or manual configuration. The solution MUST work
consistently without regard to how peers are determined.
*Compliant*. DOIC contains no assumptions about how peers are
discovered.
REQ 6: The solution designers SHOULD seek to minimize the amount of
new configuration required in order to work. For example, it
is better to allow peers to advertise or negotiate support
for the solution, rather than to require that this knowledge
to be configured at each node.
*Partially Compliant*. Most DOIC parameters are advertised
using the DOIC capability announcement mechanism. However,
there are some situations where configuration is required.
For example, a DOIC node detect the fact that a peer may not
support DOIC when nodes on the other side of the non-
supporting node do support DOIC without configuration.
C.6.2. Performance
REQ 7: The solution and any associated default algorithm(s) MUST
ensure that the system remains stable. At some point after
an overload condition has ended, the solution MUST enable
capacity to stabilize and become equal to what it would be in
the absence of an overload condition. Note that this also
requires that the solution MUST allow nodes to shed load
without introducing non-converging oscillations during or
after an overload condition.
*Compliant*. The specification offers guidance that
implementations should apply hysteresis when recovering from
overload, and avoid sudden ramp ups in offered load when
recovering.
REQ 8: Supporting nodes MUST be able to distinguish current overload
information from stale information.
*Partially Compliant*. DOIC overload reports are "soft
state", that is they expire after an indicated period. DOIC
nodes may also send reports that end existing overload
conditions. DOIC requires reporting nodes to ensure that all
relevant reacting nodes receive overload reports.
However, since DOIC does not allow reporting nodes to send
OLRs in watchdog messages, if an overload condition results
in zero offered load, the reporting node cannot update the
condition until the expiration of the original OLR.
REQ 9: The solution MUST function across fully loaded as well as
quiescent transport connections. This is partially derived
from the requirement for stability in REQ 7.
*Not Compliant*. DOIC does not allow OLRs to be sent over
quiescent transport connections. This is due to the fact
that OLRs cannot be sent outside of the application to which
they apply.
REQ 10: Consumers of overload information MUST be able to determine
when the overload condition improves or ends.
*Partially Compliant*. (See response to previous two
requirements.)
REQ 11: The solution MUST be able to operate in networks of different
sizes.
*Compliant*. DOIC makes no assumptions about the size of the
network. DOIC can operate purely between clients and
servers, or across agents.
REQ 12: When a single network node fails, goes into overload, or
suffers from reduced processing capacity, the solution MUST
make it possible to limit the impact of the affected node on
other nodes in the network. This helps to prevent a small-
scale failure from becoming a widespread outage.
*Partially Compliant*. DOIC allows overload reports for an
entire realm, where abated traffic will not be redirected
towards another server. But in situations where nodes choose
to divert traffic to other nodes, DOIC offers no way of
knowing whether the new recipients can handle the traffic if
they have not already indicated overload. This may be
mitigated with the use of a future "load" extension, or with
the use of proprietary dynamic load-balancing mechanisms.
REQ 13: The solution MUST NOT introduce substantial additional work
for a node in an overloaded state. For example, a
requirement for an overloaded node to send overload
information every time it received a new request would
introduce substantial work.
*Not Compliant*. DOIC does in fact encourage an overloaded
node to send an OLR in every response. The working group
that other mechanisms to ensure that every relevant node
receives an OLR would create even more work. [Note: This
needs discussion.]
REQ 14: Some scenarios that result in overload involve a rapid
increase of traffic with little time between normal levels
and levels that induce overload. The solution SHOULD provide
for rapid feedback when traffic levels increase.
*Compliant*. The piggyback mechanism allows OLRs to be sent
at the same rate as application traffic.
REQ 15: The solution MUST NOT interfere with the congestion control
mechanisms of underlying transport protocols. For example, a
solution that opened additional TCP connections when the
network is congested would reduce the effectiveness of the
underlying congestion control mechanisms.
*Compliant*. DOIC does not require or recommend changes in
the handling of transport protocols or connections.
C.6.3. Heterogeneous Support for Solution
REQ 16: The solution is likely to be deployed incrementally. The
solution MUST support a mixed environment where some, but not
all, nodes implement it.
*Partially Compliant*. DOIC works with most mixed-deployment
scenarios. However, it cannot work across a non-supporting
proxy that modifies Origin-Host AVPs in answer messages.
DOIC will have limited impact in networks where the nodes
that perform server selections do not support the mechanism.
REQ 17: In a mixed environment with nodes that support the solution
and nodes that do not, the solution MUST NOT result in
materially less useful throughput during overload as would
have resulted if the solution were not present. It SHOULD
result in less severe overload in this environment.
*Compliant*. In most mixed-support deployment, DOIC will
offer at least some value, and will not make things worse.
REQ 18: In a mixed environment of nodes that support the solution and
nodes that do not, the solution MUST NOT preclude elements
that support overload control from treating elements that do
not support overload control in an equitable fashion relative
to those that do. Users and operators of nodes that do not
support the solution MUST NOT unfairly benefit from the
solution. The solution specification SHOULD provide guidance
to implementers for dealing with elements not supporting
overload control.
*Compliant*. DOIC provides mechanisms to abate load from non-
supporting sources. Furthermore, it recommends that
reporting nodes will still need to be able to apply whatever
protections they would ordinarily apply if DOIC were not in
use.
REQ 19: It MUST be possible to use the solution between nodes in
different realms and in different administrative domains.
*Partially Compliant*. DOIC allows sending OLRs across
administrative domains, and potentially to nodes in other
realms. However, an OLR cannot indicate overload for realms
other than the one in the Origin-Realm AVP of the containing
answer.
REQ 20: Any explicit overload indication MUST be clearly
distinguishable from other errors reported via Diameter.
*Compliant*. DOIC sends explicit overload indication in
overload reports. It does not depend on error result codes.
REQ 21: In cases where a network node fails, is so overloaded that it
cannot process messages, or cannot communicate due to a
network failure, it may not be able to provide explicit
indications of the nature of the failure or its levels of
overload. The solution MUST result in at least as much
useful throughput as would have resulted if the solution were
not in place.
*Compliant*. DOIC overload reports have the primary effect of
suppressing message retries in overload conditions. DOIC
recommends that messages never be silently dropped if at all
possible.
C.6.4. Granular Control
REQ 22: The solution MUST provide a way for a node to throttle the
amount of traffic it receives from a peer node. This
throttling SHOULD be graded so that it can be applied
gradually as offered load increases. Overload is not a
binary state; there may be degrees of overload.
*Compliant*. The "loss" algorithm expresses a percentage
reduction.
REQ 23: The solution MUST provide sufficient information to enable a
load-balancing node to divert messages that are rejected or
otherwise throttled by an overloaded upstream node to other
upstream nodes that are the most likely to have sufficient
capacity to process them.
*Not Compliant*. DOIC provides no built in mechanism to
determine the best place to divert messages that would
otherwise be throttled. This can be accomplished with a
future "load" extension, or with proprietary load balancing
mechanisms.
REQ 24: The solution MUST provide a mechanism for indicating load
levels, even when not in an overload condition, to assist
nodes in making decisions to prevent overload conditions from
occurring.
*Not Compliant*. "Load" information has been left for a
future extension.
C.6.5. Priority and Policy
REQ 25: The base specification for the solution SHOULD offer general
guidance on which message types might be desirable to send or
process over others during times of overload, based on
application-specific considerations. For example, it may be
more beneficial to process messages for existing sessions
ahead of new sessions. Some networks may have a requirement
to give priority to requests associated with emergency
sessions. Any normative or otherwise detailed definition of
the relative priorities of message types during an overload
condition will be the responsibility of the application
specification.
*Compliant*. The specification offers guidance on how
requests might be prioritized for different types of
applications.
REQ 26: The solution MUST NOT prevent a node from prioritizing
requests based on any local policy, so that certain requests
are given preferential treatment, given additional
retransmission, not throttled, or processed ahead of others.
*Compliant*. Nothing in the specification prevents
application-specific, implementation-specific, or local
policies.
C.6.6. Security
REQ 27: The solution MUST NOT provide new vulnerabilities to
malicious attack or increase the severity of any existing
vulnerabilities. This includes vulnerabilities to DoS and
DDoS attacks as well as replay and man-in-the-middle attacks.
Note that the Diameter base specification [RFC6733] lacks
end-to-end security and this must be considered (see the
Security Considerations in [RFC7068]). Note that this
requirement was expressed at a high level so as to not
preclude any particular solution. It is expected that the
solution will address this in more detail.
*Compliant*. The working group is not aware of any such
vulnerabilities. [This may need further analysis.]
REQ 28: The solution MUST NOT depend on being deployed in
environments where all Diameter nodes are completely trusted.
It SHOULD operate as effectively as possible in environments
where other nodes are malicious; this includes preventing
malicious nodes from obtaining more than a fair share of
service. Note that this does not imply any responsibility on
the solution to detect, or take countermeasures against,
malicious nodes.
*Partially Compliant*. Since all Diameter security is
currently at the transport layer, nodes must trust immediate
peers to enforce trust policies. However, there are
situations where a DOIC node cannot determine if an immediate
peer supports DOIC. The authors recommend an expert security
review.
REQ 29: It MUST be possible for a supporting node to make
authorization decisions about what information will be sent
to peer nodes based on the identity of those nodes. This
allows a domain administrator who considers the load of their
nodes to be sensitive information to restrict access to that
information. Of course, in such cases, there is no
expectation that the solution itself will help prevent
overload from that peer node.
*Partially Compliant*. (See response to previous
requirement.)
REQ 30: The solution MUST NOT interfere with any Diameter-compliant
method that a node may use to protect itself from overload
from non-supporting nodes or from denial-of-service attacks.
*Compliant*. The specification recommends that any such
protection mechanism needed without DOIC should continue to
be employed with DOIC.
C.6.7. Flexibility and Extensibility
REQ 31: There are multiple situations where a Diameter node may be
overloaded for some purposes but not others. For example,
this can happen to an agent or server that supports multiple
applications, or when a server depends on multiple external
resources, some of which may become overloaded while others
are fully available. The solution MUST allow Diameter nodes
to indicate overload with sufficient granularity to allow
clients to take action based on the overloaded resources
without unreasonably forcing available capacity to go unused.
The solution MUST support specification of overload
information with granularities of at least "Diameter node",
"realm", and "Diameter application" and MUST allow
extensibility for others to be added in the future.
*Partially Compliant*. All DOIC overload reports are scoped
to the specific application and realm. Inside that scope,
overload can be reported at the specific server or whole
realm scope. As currently specified, DOIC cannot indicate
local overload for an agent. At the time of this writing,
the DIME working group has plans to work on an agent-overload
extension.
DOIC allows new "scopes" through the use of extended report
types.
REQ 32: The solution MUST provide a method for extending the
information communicated and the algorithms used for overload
control.
*Compliant*. DOIC allows new report types and abatement
algorithms to be created. These may be indicated using the
OC-Supported-Features AVP.
REQ 33: The solution MUST provide a default algorithm that is
mandatory to implement.
*Compliant*. The "loss" algorithm is mandatory to implement.
REQ 34: The solution SHOULD provide a method for exchanging overload
and load information between elements that are connected by
intermediaries that do not support the solution.
*Partially Compliant*. DOIC information can traverse non-
supporting agents, as long as those agents do not modify
certain AVPs. (e.g., Origin-Host). DOIC does not provide a
way for supporting nodes to detect such modification.
Appendix D. Considerations for Applications Integrating the DOIC Appendix D. Considerations for Applications Integrating the DOIC
Solution Solution
This section outlines considerations to be taken into account when This section outlines considerations to be taken into account when
integrating the DOIC solution into Diameter applications. integrating the DOIC solution into Diameter applications.
D.1. Application Classification D.1. Application Classification
The following is a classification of Diameter applications and The following is a classification of Diameter applications and
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a Diameter session-based application. a Diameter session-based application.
In session-less applications, the lifetime of the Session-Id is a In session-less applications, the lifetime of the Session-Id is a
single Diameter transaction, i.e. the session is implicitly single Diameter transaction, i.e. the session is implicitly
terminated after a single Diameter transaction and a new Session-Id terminated after a single Diameter transaction and a new Session-Id
is generated for each Diameter request. is generated for each Diameter request.
For the purposes of this discussion, session-less applications are For the purposes of this discussion, session-less applications are
further divided into two types of applications: further divided into two types of applications:
Stateless applications: Stateless Applications:
Requests within a stateless application have no relationship to Requests within a stateless application have no relationship to
each other. The 3GPP defined S13 application is an example of a each other. The 3GPP defined S13 application is an example of a
stateless application [S13], where only a Diameter command is stateless application [S13], where only a Diameter command is
defined between a client and a server and no state is maintained defined between a client and a server and no state is maintained
between two consecutive transactions. between two consecutive transactions.
Pseudo-session applications: Pseudo-Session Applications:
Applications that do not rely on the Session-Id AVP for Applications that do not rely on the Session-Id AVP for
correlation of application messages related to the same session correlation of application messages related to the same session
but use other session-related information in the Diameter requests but use other session-related information in the Diameter requests
for this purpose. The 3GPP defined Cx application [Cx] is an for this purpose. The 3GPP defined Cx application [Cx] is an
example of a pseudo-session application. example of a pseudo-session application.
The handling of overload reports must take the type of application The handling of overload reports must take the type of application
into consideration, as discussed in Appendix D.2. into consideration, as discussed in Appendix D.2.
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this discussion. The method used to reduce offered load is not this discussion. The method used to reduce offered load is not
specified here but could include routing requests to another Diameter specified here but could include routing requests to another Diameter
entity known to be able to handle them, or it could mean rejecting entity known to be able to handle them, or it could mean rejecting
certain requests. For a Diameter agent, rejecting requests will certain requests. For a Diameter agent, rejecting requests will
usually mean generating appropriate Diameter error responses. For a usually mean generating appropriate Diameter error responses. For a
Diameter client, rejecting requests will depend upon the application. Diameter client, rejecting requests will depend upon the application.
For example, it could mean giving an indication to the entity For example, it could mean giving an indication to the entity
requesting the Diameter service that the network is busy and to try requesting the Diameter service that the network is busy and to try
again later. again later.
Stateless applications: Stateless Applications:
By definition there is no relationship between individual requests By definition there is no relationship between individual requests
in a stateless application. As a result, when a request is sent in a stateless application. As a result, when a request is sent
or relayed to an overloaded Diameter entity - either a Diameter or relayed to an overloaded Diameter entity - either a Diameter
Server or a Diameter Agent - the sending or relaying entity can Server or a Diameter Agent - the sending or relaying entity can
choose to apply the overload treatment to any request targeted for choose to apply the overload treatment to any request targeted for
the overloaded entity. the overloaded entity.
Pseudo-session applications: Pseudo-Session Applications:
For pseudo-session applications, there is an implied ordering of For pseudo-session applications, there is an implied ordering of
requests. As a result, decisions about which requests towards an requests. As a result, decisions about which requests towards an
overloaded entity to reject could take the command code of the overloaded entity to reject could take the command code of the
request into consideration. This generally means that request into consideration. This generally means that
transactions later in the sequence of transactions should be given transactions later in the sequence of transactions should be given
more favorable treatment than messages earlier in the sequence. more favorable treatment than messages earlier in the sequence.
This is because more work has already been done by the Diameter This is because more work has already been done by the Diameter
network for those transactions that occur later in the sequence. network for those transactions that occur later in the sequence.
Rejecting them could result in increasing the load on the network Rejecting them could result in increasing the load on the network
as the transactions earlier in the sequence might also need to be as the transactions earlier in the sequence might also need to be
repeated. repeated.
Session-based applications: Session-Based Applications:
Overload handling for session-based applications must take into Overload handling for session-based applications must take into
consideration the work load associated with setting up and consideration the work load associated with setting up and
maintaining a session. As such, the entity sending requests maintaining a session. As such, the entity sending requests
towards an overloaded Diameter entity for a session-based towards an overloaded Diameter entity for a session-based
application might tend to reject new session requests prior to application might tend to reject new session requests prior to
rejecting intra-session requests. In addition, session ending rejecting intra-session requests. In addition, session ending
requests might be given a lower probability of being rejected as requests might be given a lower probability of being rejected as
rejecting session ending requests could result in session status rejecting session ending requests could result in session status
being out of sync between the Diameter clients and servers. being out of sync between the Diameter clients and servers.
Application designers that would decide to reject mid-session Application designers that would decide to reject mid-session
requests will need to consider whether the rejection invalidates requests will need to consider whether the rejection invalidates
the session and any resulting session clean-up procedures. the session and any resulting session cleanup procedures.
D.3. Request Transaction Classification D.3. Request Transaction Classification
Independent Request: Independent Request:
An independent request is not correlated to any other requests An independent request is not correlated to any other requests
and, as such, the lifetime of the session-id is constrained to an and, as such, the lifetime of the session-id is constrained to an
individual transaction. individual transaction.
Session-Initiating Request: Session-Initiating Request:
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Correlated Session-Initiating Request: Correlated Session-Initiating Request:
There are cases when multiple session-initiated requests must be There are cases when multiple session-initiated requests must be
correlated and managed by the same Diameter server. It is notably correlated and managed by the same Diameter server. It is notably
the case in the 3GPP PCC architecture [PCC], where multiple the case in the 3GPP PCC architecture [PCC], where multiple
apparently independent Diameter application sessions are actually apparently independent Diameter application sessions are actually
correlated and must be handled by the same Diameter server. correlated and must be handled by the same Diameter server.
Intra-Session Request: Intra-Session Request:
An intra session request is a request that uses the same Session- An intra-session request is a request that uses the same Session-
Id than the one used in a previous request. An intra session Id than the one used in a previous request. An intra-session
request generally needs to be delivered to the server that handled request generally needs to be delivered to the server that handled
the session creating request for the session. The STR message the session creating request for the session. The STR message
defined in [RFC6733] is an example of an intra-session requests. defined in [RFC6733] is an example of an intra-session request.
Pseudo-Session Requests: Pseudo-Session Requests:
Pseudo-session requests are independent requests and do not use Pseudo-session requests are independent requests and do not use
the same Session-Id but are correlated by other session-related the same Session-Id but are correlated by other session-related
information contained in the request. There exists Diameter information contained in the request. There exists Diameter
applications that define an expected ordering of transactions. applications that define an expected ordering of transactions.
This sequencing of independent transactions results in a pseudo This sequencing of independent transactions results in a pseudo
session. The AIR, MAR and SAR requests in the 3GPP defined Cx session. The AIR, MAR and SAR requests in the 3GPP defined Cx
[Cx] application are examples of pseudo-session requests. [Cx] application are examples of pseudo-session requests.
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D.4. Request Type Overload Implications D.4. Request Type Overload Implications
The request classes identified in Appendix D.3 have implications on The request classes identified in Appendix D.3 have implications on
decisions about which requests should be throttled first. The decisions about which requests should be throttled first. The
following list of request treatment regarding throttling is provided following list of request treatment regarding throttling is provided
as guidelines for application designers when implementing the as guidelines for application designers when implementing the
Diameter overload control mechanism described in this document. The Diameter overload control mechanism described in this document. The
exact behavior regarding throttling is a matter of local policy, exact behavior regarding throttling is a matter of local policy,
unless specifically defined for the application. unless specifically defined for the application.
Independent requests: Independent Requests:
Independent requests can generally be given equal treatment when Independent requests can generally be given equal treatment when
making throttling decisions, unless otherwise indicated by making throttling decisions, unless otherwise indicated by
application requirements or local policy. application requirements or local policy.
Session-initiating requests: Session-Initiating Requests:
Session-initiating requests often represent more work than Session-initiating requests often represent more work than
independent or intra-session requests. Moreover, session- independent or intra-session requests. Moreover, session-
initiating requests are typically followed by other session- initiating requests are typically followed by other session-
related requests. Since the main objective of the overload related requests. Since the main objective of the overload
control is to reduce the total number of requests sent to the control is to reduce the total number of requests sent to the
overloaded entity, throttling decisions might favor allowing overloaded entity, throttling decisions might favor allowing
intra-session requests over session-initiating requests. In the intra-session requests over session-initiating requests. In the
absence of local policies or application specific requirements to absence of local policies or application specific requirements to
the contrary, Individual session-initiating requests can be given the contrary, Individual session-initiating requests can be given
equal treatment when making throttling decisions. equal treatment when making throttling decisions.
Correlated session-initiating requests: Correlated Session-Initiating Requests:
A Request that results in a new binding, where the binding is used A Request that results in a new binding, where the binding is used
for routing of subsequent session-initiating requests to the same for routing of subsequent session-initiating requests to the same
server, represents more work load than other requests. As such, server, represents more work load than other requests. As such,
these requests might be throttled more frequently than other these requests might be throttled more frequently than other
request types. request types.
Pseudo-session requests: Pseudo-Session Requests:
Throttling decisions for pseudo-session requests can take into Throttling decisions for pseudo-session requests can take into
consideration where individual requests fit into the overall consideration where individual requests fit into the overall
sequence of requests within the pseudo session. Requests that are sequence of requests within the pseudo session. Requests that are
earlier in the sequence might be throttled more aggressively than earlier in the sequence might be throttled more aggressively than
requests that occur later in the sequence. requests that occur later in the sequence.
Intra-session requests: Intra-Session Requests:
There are two types of intra-sessions requests, requests that There are two types of intra-sessions requests, requests that
terminate a session and the remainder of intra-session requests. terminate a session and the remainder of intra-session requests.
Implementors and operators may choose to throttle session- Implementers and operators may choose to throttle session-
terminating requests less aggressively in order to gracefully terminating requests less aggressively in order to gracefully
terminate sessions, allow clean-up of the related resources (e.g. terminate sessions, allow cleanup of the related resources (e.g.
session state) and avoid the need for additional intra-session session state) and avoid the need for additional intra-session
requests. Favoring session-termination requests may reduce the requests. Favoring session-termination requests may reduce the
session management impact on the overloaded entity. The default session management impact on the overloaded entity. The default
handling of other intra-session requests might be to treat them handling of other intra-session requests might be to treat them
equally when making throttling decisions. There might also be equally when making throttling decisions. There might also be
application level considerations whether some request types are application level considerations whether some request types are
favored over others. favored over others.
Authors' Addresses Authors' Addresses
Jouni Korhonen (editor) Jouni Korhonen (editor)
Broadcom Broadcom
Porkkalankatu 24 Porkkalankatu 24
Helsinki FIN-00180 Helsinki FIN-00180
Finland Finland
Email: jouni.nospam@gmail.com Email: jouni.nospam@gmail.com
Steve Donovan (editor) Steve Donovan (editor)
Oracle Oracle
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