draft-ietf-dime-ovli-08.txt   draft-ietf-dime-ovli-09.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: August 8, 2015 B. Campbell Expires: February 7, 2016 B. Campbell
Oracle Oracle
L. Morand L. Morand
Orange Labs Orange Labs
February 4, 2015 August 6, 2015
Diameter Overload Indication Conveyance Diameter Overload Indication Conveyance
draft-ietf-dime-ovli-08.txt draft-ietf-dime-ovli-09.txt
Abstract Abstract
This specification defines a base solution for Diameter overload This specification defines a base solution for Diameter overload
control, referred to as Diameter Overload Indication Conveyance control, referred to as Diameter Overload Indication Conveyance
(DOIC). (DOIC).
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 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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 August 8, 2015. This Internet-Draft will expire on February 7, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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 . . . . . . . . . . . . . . . . 4 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
3. Conventions Used in This Document . . . . . . . . . . . . . . 5 3. Conventions Used in This Document . . . . . . . . . . . . . . 5
4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5 4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 6
4.2. DOIC Capability Announcement . . . . . . . . . . . . . . 7 4.2. DOIC Capability Announcement . . . . . . . . . . . . . . 7
4.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9 4.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9
4.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 11 4.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 11
4.5. Simplified Example Architecture . . . . . . . . . . . . . 11 4.5. Simplified Example Architecture . . . . . . . . . . . . . 11
5. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12 5. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12
5.1. Capability Announcement . . . . . . . . . . . . . . . . . 12 5.1. Capability Announcement . . . . . . . . . . . . . . . . . 12
5.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 13 5.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 13
5.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 13 5.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 13
5.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 14 5.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 14
5.2. Overload Report Processing . . . . . . . . . . . . . . . 15 5.2. Overload Report Processing . . . . . . . . . . . . . . . 15
5.2.1. Overload Control State . . . . . . . . . . . . . . . 15 5.2.1. Overload Control State . . . . . . . . . . . . . . . 15
5.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 19 5.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 19
5.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 20 5.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 20
5.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 22 5.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 22
6. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 22 6. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 23
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 23 6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 23
6.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 23 6.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 24
6.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 24 6.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 24
7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 24 7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 25
7.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 25 7.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 25
7.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 25 7.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 25
7.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 25 7.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 26
7.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 26 7.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 26
7.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 26 7.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 26
7.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 26 7.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 27
7.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 27 7.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 27
7.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 27 7.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 27
8. Error Response Codes . . . . . . . . . . . . . . . . . . . . 28 8. Error Response Codes . . . . . . . . . . . . . . . . . . . . 28
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
9.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 28 9.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 29
9.2. New registries . . . . . . . . . . . . . . . . . . . . . 29 9.2. New registries . . . . . . . . . . . . . . . . . . . . . 29
10. Security Considerations . . . . . . . . . . . . . . . . . . . 29 10. Security Considerations . . . . . . . . . . . . . . . . . . . 30
10.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 30 10.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 30
10.2. Denial of Service Attacks . . . . . . . . . . . . . . . 31 10.2. Denial of Service Attacks . . . . . . . . . . . . . . . 31
10.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . 31 10.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . 32
10.4. End-to End-Security Issues . . . . . . . . . . . . . . . 32 10.4. End-to End-Security Issues . . . . . . . . . . . . . . . 32
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 33 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 33
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
12.1. Normative References . . . . . . . . . . . . . . . . . . 33 12.1. Normative References . . . . . . . . . . . . . . . . . . 34
12.2. Informative References . . . . . . . . . . . . . . . . . 33 12.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Issues left for future specifications . . . . . . . 34 Appendix A. Issues left for future specifications . . . . . . . 35
A.1. Additional traffic abatement algorithms . . . . . . . . . 34 A.1. Additional traffic abatement algorithms . . . . . . . . . 35
A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 34 A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 35
A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 34 A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 35
Appendix B. Deployment Considerations . . . . . . . . . . . . . 34 Appendix B. Deployment Considerations . . . . . . . . . . . . . 35
Appendix C. Requirements Conformance Analysis . . . . . . . . . 35 Appendix C. Considerations for Applications Integrating the DOIC
C.1. Deferred Requirements . . . . . . . . . . . . . . . . . . 35 Solution . . . . . . . . . . . . . . . . . . . . . . 36
C.2. Detection of non-supporting Intermediaries . . . . . . . 35 C.1. Application Classification . . . . . . . . . . . . . . . 36
C.3. Implicit Application Indication . . . . . . . . . . . . . 36 C.2. Application Type Overload Implications . . . . . . . . . 37
C.4. Stateless Operation . . . . . . . . . . . . . . . . . . . 36 C.3. Request Transaction Classification . . . . . . . . . . . 38
C.5. No New Vulnerabilities . . . . . . . . . . . . . . . . . 36 C.4. Request Type Overload Implications . . . . . . . . . . . 39
C.6. Detailed Requirements . . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
C.6.1. General . . . . . . . . . . . . . . . . . . . . . . . 36
C.6.2. Performance . . . . . . . . . . . . . . . . . . . . . 38
C.6.3. Heterogeneous Support for Solution . . . . . . . . . 40
C.6.4. Granular Control . . . . . . . . . . . . . . . . . . 42
C.6.5. Priority and Policy . . . . . . . . . . . . . . . . . 43
C.6.6. Security . . . . . . . . . . . . . . . . . . . . . . 43
C.6.7. Flexibility and Extensibility . . . . . . . . . . . . 44
Appendix D. Considerations for Applications Integrating the DOIC
Solution . . . . . . . . . . . . . . . . . . . . . . 46
D.1. Application Classification . . . . . . . . . . . . . . . 46
D.2. Application Type Overload Implications . . . . . . . . . 47
D.3. Request Transaction Classification . . . . . . . . . . . 48
D.4. Request Type Overload Implications . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
1. Introduction 1. Introduction
This specification defines a base solution for Diameter overload This specification defines a base solution for Diameter overload
control, referred to as Diameter Overload Indication Conveyance control, referred to as Diameter Overload Indication Conveyance
(DOIC), based on the requirements identified in [RFC7068]. (DOIC), based on the requirements identified in [RFC7068].
This specification addresses Diameter overload control between This specification addresses Diameter overload control between
Diameter nodes that support the DOIC solution. The solution, which Diameter nodes that support the DOIC solution. The solution, which
is designed to apply to existing and future Diameter applications, is designed to apply to existing and future Diameter applications,
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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.
Note that the overload 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 does not address all the requirements listed in [RFC7068]. A number
of overload control related features are left for future of overload control related features are left for future
specifications. See Appendix A for a list of extensions that are specifications. See Appendix A for a list of extensions that are
currently being considered. See Appendix C for an analysis of currently being considered.
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
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occurrence of overload control. occurrence of overload control.
Diversion Diversion
An overload abatement treatment where the reacting node selects An overload abatement treatment where the reacting node selects
alternate destinations or paths for requests. alternate destinations or paths for requests.
Host-Routed Requests Host-Routed Requests
Requests that a reacting node knows will be served by a particular Requests that a reacting node knows will be served by a particular
host, either due to the presence of a Destination-Host AVP, or by host, either due to the presence of a Destination-Host Attribute
some other local knowledge on the part of the reacting node. Value Pair (AVP), or by some other local knowledge on the part of
the reacting node.
Overload Control State (OCS) Overload Control State (OCS)
Internal state maintained by a reporting or reacting node Internal state maintained by a reporting or reacting node
describing occurrences of overload control. describing occurrences of overload control.
Overload Report (OLR) Overload Report (OLR)
Overload control information for a particular overload occurrence Overload control information for a particular overload occurrence
sent by a reporting node. sent by a reporting node.
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service the request. 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
An abatement treatment that limits the number of requests sent by An abatement treatment that limits the number of requests sent by
the DIOC reacting node. Throttling can include a Diameter Client the reacting node. Throttling can include a Diameter Client
choosing to not send requests, or a Diameter Agent or Server choosing to not send requests, or a Diameter Agent or Server
rejecting requests with appropriate error responses. In both rejecting requests with appropriate error responses. In both
cases the result of the throttling is a permanent rejection of the cases the result of the throttling is a permanent rejection of the
transaction. transaction.
3. Conventions Used in This Document 3. Conventions Used in This Document
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].
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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 that are in response to a request that by the reporting node that are in response to a request that
contained the OC-Supported-Features AVP. Reporting nodes may include contained the OC-Supported-Features AVP. Reporting nodes may include
overload reports using the OC-OLR AVP in answer messages. overload reports using the OC-OLR AVP in answer 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. sent by a "reporting node"). "reacting node") or an answer (i.e., sent 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.
4.2. DOIC Capability Announcement 4.2. 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
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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.
Note: As discussed elsewhere in the document, agents in the path Note: As discussed elsewhere in the document, agents in the path
of the request can modify the OC-Supported-Features AVP. of the request can modify the OC-Supported-Features AVP.
Note: The DOIC solution must support deployments where Diameter Note: The DOIC solution must support deployments where Diameter
Clients and/or Diameter Servers do not support the DOIC solution. Clients and/or Diameter Servers do not support the DOIC solution.
In this scenario, Diameter Agents that support the DOIC solution In this scenario, Diameter Agents that support the DOIC solution
may handle overload abatement for the non supporting Diameter may handle overload abatement for the non-supporting Diameter
nodes. In this case the DOIC agent will insert the OC-Supported- nodes. In this case the DOIC agent will insert the OC-Supported-
Features AVP in requests that do not already contain one, telling Features AVP in requests that do not already contain one, telling
the reporting node that there is a DOIC node that will handle the reporting node that there is a DOIC node that will handle
overload abatement. For transactions where there was an OC- overload abatement. For transactions where there was an OC-
Supporting-Features AVP in the request, the agent will insert the Supporting-Features AVP in the request, the agent will insert the
OC-Supported-Features AVP in answers, telling the reacting node OC-Supported-Features AVP in answers, telling the reacting node
that there is a reporting node. that there is a reporting node.
The OC-Feature-Vector AVP will always contain an indication of The OC-Feature-Vector AVP will always contain an indication of
support for the loss overload abatement algorithm defined in this support for the loss overload abatement algorithm defined in this
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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 can update the OC- path of a request differ. In this case, the agent can update the OC-
Supported-Features 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.
Note: The logic to determine if the content of the OC-Supported- Note: The logic to determine if the content of the OC-Supported-
Features AVP should be changed is out-of-scope for this document, Features AVP should be changed is out-of-scope for this document,
as is the logic to determine the content of a modified OC- as is the logic to determine the content of a modified OC-
Supported-Features AVP. These are left to implementation Supported-Features AVP. These are left to implementation
decisions. Care must be taken not to introduce interoperability decisions. Care must be taken not to introduce interoperability
issues for downstream or upstream DOIC nodes. issues for downstream or upstream DOIC nodes. As such, the agent
must act as a fully compliant reporting node to the downstream
reacting node and as a fully compliant reacting node to the
upstream reporting node.
4.3. DOIC Overload Condition Reporting 4.3. DOIC Overload Condition Reporting
As with DOIC capability announcement, overload condition reporting As with DOIC capability announcement, overload condition reporting
uses new AVPs (Section 7.3) to indicate an overload condition. uses new AVPs (Section 7.3) 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.
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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 abatement is no longer needed. ended and abatement 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.
Note that erroneous overload reports can be used for DoS attacks.
This includes the ability to indicate that a significant reduction in
traffic, up to and including a request for no traffic, should be sent
to a reporting node. As such, care should be taken to verify the
sender of overload reports.
4.4. DOIC Extensibility 4.4. 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, along is based on existing Diameter based extensibility mechanisms, along
with the DOIC capability announcement mechanism. 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 the definition of new scopes 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.
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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.
A reporting node knows what overload control functionality is A reporting node knows what overload control functionality is
supported by the reacting node based on the content or absence of the supported by the reacting node based on the content or absence of the
OC-Feature-Vector AVP within the OC-Supported-Features AVP in the OC-Feature-Vector AVP within the OC-Supported-Features AVP in the
request message. request message.
A reporting node MUST indicate support for one and only one abatement A reporting node MUST A reporting node MUST select a single abatement
algorithm in the OC-Feature-Vector AVP. The abatement algorithm algorithm in the OC-Feature-Vector AVP. The abatement algorithm
selected MUST indicate the abatement algorithm the reporting node selected MUST indicate the abatement algorithm the reporting node
wants the reacting node to use when the reporting node enters an wants the reacting node to use when the reporting node enters an
overload condition. overload condition.
The abatement algorithm selected MUST be from the set of abatement The abatement algorithm selected MUST be from the set of abatement
algorithms contained in the request message's OC-Feature-Vector AVP. algorithms contained in the request message's OC-Feature-Vector AVP.
A reporting node that selects the loss algorithm may do so by A reporting node that selects the loss algorithm may do so by
including the OC-Feature-Vector AVP with an explicit indication of including the OC-Feature-Vector AVP with an explicit indication of
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Diameter Agents that support DOIC can ensure that all messages Diameter Agents that support DOIC can ensure that all messages
relayed by the agent contain the OC-Supported-Features AVP. relayed by the agent contain the OC-Supported-Features AVP.
A Diameter Agent MAY take on reacting node behavior for Diameter A Diameter Agent MAY take on reacting node behavior for Diameter
endpoints that do not support the DOIC solution. A Diameter Agent endpoints that do not support the DOIC solution. A Diameter Agent
detects that a Diameter endpoint does not support DOIC reacting node detects that a Diameter endpoint does not support DOIC reacting node
behavior when there is no OC-Supported-Features AVP in a request behavior when there is no OC-Supported-Features AVP in a request
message. message.
For a Diameter Agent to be a reacting node for a non supporting For a Diameter Agent to be a reacting node for a non-supporting
Diameter endpoint, the Diameter Agent MUST include the OC-Supported- Diameter endpoint, the Diameter Agent MUST include the OC-Supported-
Features AVP in request messages it relays that do not contain the Features AVP in request messages it relays that do not contain the
OC-Supported-Features AVP. OC-Supported-Features AVP.
A Diameter Agent MAY take on reporting node behavior for Diameter A Diameter Agent MAY take on reporting node behavior for Diameter
endpoints that do not support the DOIC solution. The Diameter Agent endpoints that do not support the DOIC solution. The Diameter Agent
MUST have visibility to all traffic destined for the non supporting MUST have visibility to all traffic destined for the non-supporting
host in order to become the reporting node for the Diameter endpoint. host in order to become the reporting node for the Diameter endpoint.
A Diameter Agent detects that a Diameter endpoint does not support A Diameter Agent detects that a Diameter endpoint does not support
DOIC reporting node behavior when there is no OC-Supported-Features DOIC reporting node behavior when there is no OC-Supported-Features
AVP in an answer message for a transaction that contained the OC- AVP in an answer message for a transaction that contained the OC-
Supported-Features AVP in the request message. Supported-Features AVP in the request message.
If a request already has the OC-Supported-Features AVP, a Diameter If a request already has the OC-Supported-Features AVP, a Diameter
agent MAY modify it to reflect the features appropriate for the agent MAY modify it to reflect the features appropriate for the
transaction. Otherwise, the agent relays the OC-Supported-Features transaction. Otherwise, the agent relays the OC-Supported-Features
AVP without change. AVP without change.
skipping to change at page 17, line 45 skipping to change at page 17, line 45
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 a reacting node sequence number stored in the matching OCS entry then a reacting 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 a 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 reacting node determines that the sequence number has rolled
over then the reacting node MUST update the matching OCS entry. This
can be determined by recognizing that the number has changed from
something close to the maximum value in the OC-Sequence-Number AVP to
something close to the minimum value in the OC-Sequence-Number AVP.
If the received OLR is for a new overload condition then a 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 this means a reacting node creates on OCS entry For a host-report this means a reacting node creates on OCS entry
with the application-id in the received message and DiameterIdentity with the application-id in the received message and DiameterIdentity
of 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.
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Origin-Realm in the received message. Origin-Realm in the received message.
If the received OLR contains a validity duration of zero ("0") then a If the received OLR contains a validity duration of zero ("0") then a
reacting node MUST update the OCS entry as being expired. reacting node MUST update the OCS entry as being expired.
Note: It is not necessarily appropriate to delete the OCS entry, Note: It is not necessarily appropriate to delete the OCS entry,
as there is recommended behavior that the reacting node slowly as there is recommended behavior that the reacting node slowly
returns to full traffic when ending an overload abatement period. returns to full traffic when ending an overload abatement 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").
5.2.1.4. Reporting Node Maintenance of Overload Control State 5.2.1.4. 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.
Note: If a reporting node knows through absence of the OC- Note: If a reporting node knows through absence of the OC-
Supported-Features AVP in received messages that there are no Supported-Features AVP in received messages that there are no
reacting nodes supporting DOIC then the reporting node can choose reacting nodes supporting DOIC then the reporting node can choose
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the request is to receive overload abatement treatment. 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 6 for the overload abatement algorithm logic applied. Section 6 for the overload abatement algorithm logic applied.
If the overload abatement algorithm selects the request for overload If the overload abatement algorithm selects the request for overload
abatement treatment then the reacting node MUST apply overload abatement treatment then the reacting node MUST apply overload
abatement treatment on the request. The abatement treatment applied abatement treatment on the request. The abatement treatment applied
depends on the context of the request. depends on the context of the request.
If diversion abatement treatment is possible (i.e. a different path If diversion abatement treatment is possible (i.e., a different path
for the request can be selected where the overloaded node is not part for the request can be selected where the overloaded node is not part
of the different path), then the reacting node SHOULD apply diversion of the different path), then the reacting node SHOULD apply diversion
abatement treatment to the request. The reacting node MUST apply abatement treatment to the request. The reacting node MUST apply
throttling abatement treatment to requests identified for abatement throttling abatement treatment to requests identified for abatement
treatment when diversion treatment is not possible or was not treatment when diversion treatment is not possible or was not
applied. applied.
Note: This only addresses the case where there are two defined Note: This only addresses the case where there are two defined
abatement treatments, diversion and throttling. Any extension abatement treatments, diversion and throttling. Any extension
that defines a new abatement treatment must also defined the that defines a new abatement treatment must also define the
interaction of the new abatement treatment with existing interaction of the new abatement treatment with existing
treatments. treatments.
If the overload abatement treatment results in throttling of the If the overload abatement treatment results in throttling of the
request and if the reacting node is an agent then the agent MUST send request and if the reacting node is an agent then the agent MUST send
an appropriate error as defined in Section 8. an appropriate error as defined in Section 8.
Diameter endpoints that throttle requests need to do so according to Diameter endpoints that throttle requests need to do so according to
the rules of the client application. Those rules will vary by the rules of the client application. Those rules will vary by
application, and are beyond the scope of this document. application, and are beyond the scope of this document.
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matches the application-id in any active OCS entry and if the matches the application-id in any active OCS entry and if the
report-type in the OCS entry matches a report-type supported by report-type in the OCS entry matches a report-type supported by
the reporting 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 depend on the selected algorithm. The contents of the OC-OLR AVP depend on the selected algorithm.
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 the Note: In some cases (e.g., when there are one or more agents in
path between reporting and reacting nodes, or when overload the path between reporting and reacting nodes, or when overload
reports are discarded by reacting nodes) a reporting node may not reports are discarded by reacting nodes) a reporting node may 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: A reacting node implicitly advertises support for the host Note: A reacting node implicitly advertises support for the host
and realm report types by including the OC-Supported-Features AVP and realm report types by including the OC-Supported-Features AVP
in the request. Support for other report types will be explicitly in the request. Support for other report types will be explicitly
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before terminating the OLR, or it might send a series of OLRs before terminating the OLR, or it might send a series of OLRs
indicating progressively less overload severity. indicating progressively less overload severity.
5.3. Protocol Extensibility 5.3. Protocol Extensibility
The DOIC solution can be extended. Types of potential extensions The DOIC solution can be extended. Types of potential extensions
include new traffic abatement algorithms, new report types or other include new traffic abatement algorithms, new report types or other
new functionality. new functionality.
When defining a new extension that requires new normative behavior, When defining a new extension that requires new normative behavior,
the specification MUST define a new feature for the OC-Feature- the specification must define a new feature for the OC-Feature-
Vector. This feature bit is used to communicate support for the new Vector. This feature bit is used to communicate support for the new
feature. 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 or SHOULD be defined to be extensions to the OC-Supported-Features or
OC-OLR AVPs defined in this document. OC-OLR AVPs defined in this document.
[RFC6733] defined Grouped AVP extension mechanisms apply. This [RFC6733] defined Grouped AVP extension mechanisms apply. This
allows, for example, defining a new feature that is mandatory to be allows, for example, defining a new feature that is mandatory to be
understood even when piggybacked on an existing application. understood even when piggybacked on an existing application.
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 OC-OLR AVP handling.
The OC-Supported-Feature and OC-OLR AVPs can be expanded with The OC-Supported-Feature and OC-OLR AVPs can be expanded with
optional sub-AVPs only if a legacy DOIC implementation can safely optional sub-AVPs only if a legacy DOIC implementation can safely
ignore them without breaking backward compatibility for the given OC- ignore them without breaking backward compatibility for the given OC-
Report-Type AVP value. Any new sub-AVPs MUST NOT require that the Report-Type AVP value. Any new sub-AVPs must not require that the
M-bit be set. M-bit be set.
Documents that introduce new report types MUST describe any Documents that introduce new report types must describe any
limitations on their use across non-supporting agents. limitations on their use across non-supporting agents.
As with any Diameter specification, RFC6733 requires all new AVPs to As with any Diameter specification, RFC6733 requires all new AVPs to
be registered with IANA. See Section 9 for the required procedures. be registered with IANA. See Section 9 for the required procedures.
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. types (in the OC-Report-Type AVP) MUST be registered with IANA.
6. Loss Algorithm 6. Loss Algorithm
This section documents the Diameter overload loss abatement This section documents the Diameter overload loss abatement
algorithm. algorithm.
6.1. Overview 6.1. Overview
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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 overload abatement treatment 4. The reacting node determines if overload abatement treatment
should be applied to the request. One approach that could be should be applied to the request. One approach that could be
taken for each request is to select a random number between 1 and taken for each request is to select a uniformly selected random
100. If the random number is less than or equal to the indicated number between 1 and 100. If the random number is less than or
reduction percentage then the request is given abatement equal to the indicated reduction percentage then the request is
treatment, otherwise the request is given normal routing given abatement treatment, otherwise the request is given normal
treatment. routing treatment.
6.2. Reporting Node Behavior 6.2. Reporting Node Behavior
The method a reporting node 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 reduction in traffic, it includes an determines the need to request a reduction in traffic, it includes an
OC-OLR AVP in answer messages as described in Section 5.2.3. OC-OLR AVP in answer messages as described in Section 5.2.3.
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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.
If reacting node comes out of the 100 percent traffic reduction as a If reacting node comes out of the 100 percent traffic reduction,
result of the overload report timing out, the reacting node sending meaning it has received an OLR indicating that no traffic should be
the traffic SHOULD be conservative and, for example, first send sent, as a result of the overload report timing out the reacting node
"probe" messages to learn the overload condition of the overloaded sending the traffic SHOULD be conservative and, for example, first
node before converging to any traffic amount/rate decided by the send "probe" messages to learn the overload condition of the
sender. Similar concerns apply in all cases when the overload report overloaded node before converging to any traffic amount/rate decided
times out unless the previous overload report stated 0 percent by the sender. Similar concerns apply in all cases when the overload
report times out unless the previous overload report stated 0 percent
reduction. reduction.
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.
7. Attribute Value Pairs 7. 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
document. document.
Refer to section 4 of [RFC6733] for more information on AVPs and AVP
data types.
7.1. OC-Supported-Features AVP 7.1. OC-Supported-Features AVP
The OC-Supported-Features AVP (AVP code TBD1) is of type 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 >
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7.4. OC-Sequence-Number AVP 7.4. OC-Sequence-Number AVP
The OC-Sequence-Number AVP (AVP code TBD4) is of type Unsigned64. The OC-Sequence-Number AVP (AVP code TBD4) 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 5.2. Section 5.2.
From the functionality point of view, the OC-Sequence-Number AVP is From the functionality point of view, the OC-Sequence-Number AVP is
used as a non-volatile increasing counter for a sequence of overload used as a non-volatile increasing counter for a sequence of overload
reports between two DOIC nodes for the same overload occurrence. reports between two DOIC nodes for the same overload occurrence.
Sequence numbers are treated in a uni-directional manner, i.e. two Sequence numbers are treated in a uni-directional manner, i.e., two
sequence numbers on each direction between two DOIC nodes are not sequence numbers on each direction between two DOIC nodes are not
related or correlated. related or correlated.
7.5. OC-Validity-Duration AVP 7.5. OC-Validity-Duration AVP
The OC-Validity-Duration AVP (AVP code TBD5) is of type Unsigned32 The OC-Validity-Duration AVP (AVP code TBD5) is of type Unsigned32
and indicates in seconds the validity time of the overload report. and indicates in seconds the validity time of the overload report.
The number of seconds is measured after reception of the first OC-OLR The number of seconds is measured after reception of the first OC-OLR
AVP with a given value of OC-Sequence-Number AVP. The default value AVP with a given value of OC-Sequence-Number AVP. The default value
for the OC-Validity-Duration AVP is 30 seconds. When the OC- for the OC-Validity-Duration AVP is 30 seconds. When the OC-
Validity-Duration AVP is not present in the OC-OLR AVP, the default Validity-Duration AVP is not present in the OC-OLR AVP, the default
value applies. The maximum value for the OC-Validity-Duration AVP is value applies. The maximum value for the OC-Validity-Duration AVP is
86,400 seconds (24 hours). 86,400 seconds (24 hours). If the value received in the OC-Validity-
Duration is greater than the maximum value then the default value
applies.
7.6. OC-Report-Type AVP 7.6. OC-Report-Type AVP
The OC-Report-Type AVP (AVP code TBD6) is of type Enumerated. The The OC-Report-Type AVP (AVP code TBD6) 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:
HOST_REPORT 0 The overload report is for a host. Overload abatement HOST_REPORT 0 The overload report is for a host. Overload abatement
treatment applies to host-routed requests. treatment applies to host-routed requests.
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The OC-Reduction-Percentage AVP (AVP code TBD7) is of type Unsigned32 The OC-Reduction-Percentage AVP (AVP code TBD7) 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
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.
7.8. Attribute Value Pair flag rules 7.8. 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 7.1 Grouped | | V | |OC-Supported-Features TBD1 7.1 Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Feature-Vector TBD2 7.2 Unsigned64 | | V | |OC-Feature-Vector TBD2 7.2 Unsigned64 | | V |
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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.
If the request arrived at the reporting node with a Destination- If the request arrived at the reporting node with a Destination-
Host AVP populated with its own Diameter identity then the Host AVP populated with its own Diameter identity then the
reporting node can assume that retrying the request would result reporting node can assume that retrying the request would 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.
9. IANA Considerations 9. IANA Considerations
9.1. AVP codes 9.1. AVP codes
New AVPs defined by this specification are listed in Section 7. All New AVPs defined by this specification are listed in Section 7. All
AVP codes are 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.
9.2. New registries 9.2. 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.
A new "Overload Control Feature Vector" registry is required. The A new "Overload Control Feature Vector" registry is required. The
registry must contain the following: registry must contain the following:
Feature Vector Value Name
Feature Vector Value Feature Vector Value
Specification - the specification that defines the new value. Specification - the specification that defines the new value.
See Section 7.2 for the initial Feature Vector Value in the registry. See Section 7.2 for the initial Feature Vector Value in the registry.
This specification is the specification defining the value. New This specification is the specification defining the value. New
values can be added into the registry using the Specification values can be added into the registry using the Specification
Required policy. [RFC5226]. Required policy. [RFC5226].
A new "Overload Report Type" registry is required. The registry must A new "Overload Report Type" registry is required. The registry must
contain the following: contain the following:
Report Type Value Name
Report Type Value Report Type Value
Specification - the specification that defines the new value. Specification - the specification that defines the new value.
See Section 7.6 for the initial assignment in the registry. New See Section 7.6 for the initial assignment in the registry. New
types can be added using the Specification Required policy [RFC5226]. types can be added using the Specification Required policy [RFC5226].
10. Security Considerations 10. Security Considerations
DOIC gives Diameter nodes the ability to request that downstream DOIC gives Diameter nodes the ability to request that downstream
nodes send fewer Diameter requests. Nodes do this by exchanging nodes send fewer Diameter requests. Nodes do this by exchanging
overload reports that directly effect this reduction. This exchange overload reports that directly effect this reduction. This exchange
is potentially subject to multiple methods of attack, and has the is potentially subject to multiple methods of attack, and has the
potential to be used as a Denial-of-Service (DoS) attack vector. potential to be used as a Denial-of-Service (DoS) attack vector. For
instance, a series of injected realm OLRs with a requested reduction
percentage of 100% could be used to completely eliminate any traffic
from being sent to that realm.
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.
10.1. Potential Threat Modes 10.1. 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 servers may be peers, that is, they may share a direct transport
(e.g. TCP or SCTP) connection, or the messages may traverse one or (e.g., TCP or SCTP) connection, or the messages may traverse one or
more intermediaries, known as Diameter Agents. Diameter nodes use more intermediaries, known as Diameter Agents. Diameter nodes use
TLS, DTLS, or IPsec to authenticate peers, and to provide TLS, DTLS, or IPsec to authenticate peers, and to provide
confidentiality and integrity protection of traffic between peers. confidentiality and integrity protection of traffic between peers.
Nodes can make authorization decisions based on the peer identities Nodes can make authorization decisions based on the peer identities
authenticated at the transport layer. authenticated at the transport layer.
When agents are involved, this presents an effectively transitive 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.
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A similar attack involves a compromised but otherwise authorized node A similar attack involves a compromised but otherwise authorized node
that sends an inappropriate overload report. For example, a server that sends an inappropriate overload report. For example, a server
for the realm "example.com" might send an overload report indicating for the realm "example.com" might send an overload report indicating
that a competitor's realm "example.net" is overloaded. If other that a competitor's realm "example.net" is overloaded. If other
nodes act on the report, they may falsely believe that "example.net" nodes act on the report, they may falsely believe that "example.net"
is overloaded, effectively reducing that realm's capacity. is overloaded, effectively reducing that realm's capacity.
Therefore, it's critical that nodes validate that an overload report Therefore, it's critical that nodes validate that an overload report
received from a peer actually falls within that peer's responsibility received from a peer actually falls within that peer's responsibility
before acting on the report or forwarding the report to other peers. before acting on the report or forwarding the report to other peers.
For example, an overload report from a peer that applies to a realm For example, an overload report from a peer that applies to a realm
not handled by that peer is suspect. not handled by that peer is suspect. This may require out-of-band,
non Diameter agreements and/or mechanisms.
This attack is partially mitigated by the fact that the This attack is partially mitigated by the fact that the
application, as well as host and realm, for a given OLR is application, as well as host and realm, for a given OLR is
determined implicitly by respective AVPs in the enclosing answer. determined implicitly by respective AVPs in the enclosing answer.
If a reporting node modifies any of those AVPs, the enclosing If a reporting node modifies any of those AVPs, the enclosing
transaction will also be affected. transaction will also be affected.
10.2. Denial of Service Attacks 10.2. Denial of Service Attacks
Diameter overload reports, especially realm-reports, can cause a node Diameter overload reports, especially realm-reports, can cause a node
to cease sending some or all Diameter requests for an extended to cease sending some or all Diameter requests for an extended
period. This makes them a tempting vector for DoS attacks. period. This makes them a tempting vector for DoS attacks.
Furthermore, since Diameter is almost always used in support of other Furthermore, since Diameter is almost always used in support of other
protocols, a DoS attack on Diameter is likely to impact those protocols, a DoS attack on Diameter is likely to impact those
protocols as well. Therefore, Diameter nodes MUST NOT honor or protocols as well. In the worst case, where the Diameter application
forward OLRs received from peers that are not trusted to send them. is being used for access control into an IP network, a coordinated
DOS attack could result in the blockage of all traffic into that
network. Therefore, Diameter nodes MUST NOT honor or forward OLRs
received from peers that are not trusted to send them.
An attacker might use the information in an OLR to assist in DoS An attacker might use the information in an OLR to assist in DoS
attacks. For example, an attacker could use information about attacks. For example, an attacker could use information about
current overload conditions to time an attack for maximum effect, or current overload conditions to time an attack for maximum effect, or
use subsequent overload reports as a feedback mechanism to learn the use subsequent overload reports as a feedback mechanism to learn the
results of a previous or ongoing attack. Operators need the ability results of a previous or ongoing attack. Operators need the ability
to ensure that OLRs are not leaked to untrusted parties. to ensure that OLRs are not leaked to untrusted parties.
10.3. Non-Compliant Nodes 10.3. Non-Compliant Nodes
skipping to change at page 31, line 47 skipping to change at page 32, line 31
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 When a Diameter node sends an overload report, it cannot assume that
all nodes will comply, even if they indicate support for DOIC. A all nodes will comply, even if they indicate support for DOIC. A
non-compliant node might continue to send requests with no reduction non-compliant node might continue to send requests with no reduction
in load. Such non-compliance could be done accidentally, or in load. Such non-compliance could be done accidentally, or
maliciously to gain an unfair advantage over compliant nodes. maliciously to gain an unfair advantage over compliant nodes.
Requirement 28 [RFC7068] indicates that the overload control solution Requirement 28 [RFC7068] indicates that the overload control solution
cannot assume that all Diameter nodes in a network are trusted, and cannot assume that all Diameter nodes in a network are trusted. It
that malicious nodes not be allowed to take advantage of the overload also requires that malicious nodes not be allowed to take advantage
control mechanism to get more than their fair share of service. of the overload control mechanism to get more than their fair share
of service.
10.4. End-to End-Security Issues 10.4. End-to End-Security Issues
The lack of end-to-end integrity features makes it difficult to The lack of end-to-end integrity features makes it difficult to
establish trust in overload reports received from non-adjacent nodes. establish trust in overload reports received from non-adjacent nodes.
Any agents in the message path may insert or modify overload reports. Any agents in the message path may insert or modify overload reports.
Nodes must trust that their adjacent peers perform proper checks on Nodes must trust that their adjacent peers perform proper checks on
overload reports from their peers, and so on, creating a transitive- overload reports from their peers, and so on, creating a transitive-
trust requirement extending for potentially long chains of nodes. trust requirement extending for potentially long chains of nodes.
Network operators must determine if this transitive trust requirement Network operators must determine if this transitive trust requirement
skipping to change at page 32, line 43 skipping to change at page 33, line 27
non-supporting agent. If nodes on the other side of that agent non-supporting agent. If nodes on the other side of that agent
send OC-Supported-Features AVPs, the agent is likely to forward send OC-Supported-Features AVPs, the agent is likely to forward
them as unknown AVPs. Messages received across the non-supporting them as unknown AVPs. Messages received across the non-supporting
agent may be indistinguishable from messages received across a agent may be indistinguishable from messages received across a
DOIC supporting agent, giving the false impression that the non- DOIC supporting agent, giving the false impression that the non-
supporting agent actually supports DOIC. This complicates the supporting agent actually supports DOIC. This complicates the
transitive-trust nature of DOIC. Operators need to be careful to transitive-trust nature of DOIC. Operators need to be careful to
avoid situations where a non-supporting agent is mistakenly avoid situations where a non-supporting agent is mistakenly
trusted to enforce DOIC related authorization policies. trusted to enforce DOIC related authorization policies.
At the time of this writing, the DIME working group is studying It is expected that work on end-to-end Diameter security might make
requirements for adding end-to-end security features it easier to establish trust in non-adjacent nodes for overload
[I-D.ietf-dime-e2e-sec-req] to Diameter. These features, when they control purposes. Readers should be reminded, however, that the
become available, might make it easier to establish trust in non- overload control mechanism allows Diameter agents to modify AVPs in,
adjacent nodes for overload control purposes. Readers should be or insert additional AVPs into, existing messages that are originated
reminded, however, that the overload control mechanism encourages by other nodes. If end-to-end security is enabled, there is a risk
Diameter agents to modify AVPs in, or insert additional AVPs into, that such modification could violate integrity protection. The
existing messages that are originated by other nodes. If end-to-end details of using any future Diameter end-to-end security mechanism
security is enabled, there is a risk that such modification could with overload control will require careful consideration, and are
violate integrity protection. The details of using any future beyond the scope of this document.
Diameter end-to-end security mechanism with overload control will
require careful consideration, and are beyond the scope of this
document.
11. Contributors 11. Contributors
The following people contributed substantial ideas, feedback, and The following people contributed substantial ideas, feedback, and
discussion to this document: discussion to this document:
o Eric McMurry o Eric McMurry
o Hannes Tschofenig o Hannes Tschofenig
skipping to change at page 33, line 34 skipping to change at page 34, line 15
o Nirav Salot o Nirav Salot
o Susan Shishufeng o Susan Shishufeng
12. References 12. References
12.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012. Ed., "Diameter Base Protocol", RFC 6733,
DOI 10.17487/RFC6733, October 2012,
<http://www.rfc-editor.org/info/rfc6733>.
12.2. Informative References 12.2. Informative References
[Cx] 3GPP, , "ETSI TS 129 229 V11.4.0", August 2013. [Cx] 3GPP, , "ETSI TS 129 229 V11.4.0", August 2013.
[I-D.ietf-dime-e2e-sec-req] [I-D.ietf-dime-e2e-sec-req]
Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay, Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay,
"Diameter AVP Level Security: Scenarios and Requirements", "Diameter AVP Level Security: Scenarios and Requirements",
draft-ietf-dime-e2e-sec-req-01 (work in progress), October draft-ietf-dime-e2e-sec-req-01 (work in progress), October
2013. 2013.
[PCC] 3GPP, , "ETSI TS 123 203 V11.12.0", December 2013. [PCC] 3GPP, , "ETSI TS 123 203 V11.12.0", December 2013.
[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
Loughney, "Diameter Credit-Control Application", RFC 4006, Loughney, "Diameter Credit-Control Application", RFC 4006,
August 2005. DOI 10.17487/RFC4006, August 2005,
<http://www.rfc-editor.org/info/rfc4006>.
[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, DOI 10.17487/RFC7068, November
2013, <http://www.rfc-editor.org/info/rfc7068>.
[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. The following sub- left for future specification and protocol work. The following sub-
sections define some of the potential extensions to the DOIC sections define some of the potential extensions to the DOIC
solution. solution.
skipping to change at page 34, line 41 skipping to change at page 35, line 30
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
This specification indicates the use of existing error messages when This specification indicates the use of existing error messages when
nodes reject requests due to overload. The DIME working group is nodes reject requests due to overload. There is an expectation that
considering defining additional error codes or AVPs to indicate that additional error codes or AVPs will be defined in a separate
overload was the reason for the rejection of the message. specification 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, network operators should enable DOIC at agents that perform agent, network operators should enable DOIC at agents that perform
server selection first. server selection first.
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 Inter Realm/Administrative Domain Considerations
There are likely to be special considerations for handling DOIC
This section contains the result of an analysis of the DOIC solutions signaling across administrative boundaries. This includes
conformance to the requirements defined in [RFC7068]. considerations for whether or not information included in the DOIC
signaling should be sent across those boundaries. In addition
C.1. Deferred Requirements consideration should be taken as to whether or not a reacting node
in one realm can be trusted to implement the requested overload
The 3GPP has adopted an early version of this document as normative abatement handling for overload reports received from a separately
references in various Diameter related specifications to support the administered realm.
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 C. 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 C.1. Application Classification
The following is a classification of Diameter applications and The following is a classification of Diameter applications and
request types. This discussion is meant to document factors that request types. This discussion is meant to document factors that
play into decisions made by the Diameter identity responsible for play into decisions made by the Diameter entity responsible for
handling overload reports. handling overload reports.
Section 8.1 of [RFC6733] defines two state machines that imply two Section 8.1 of [RFC6733] defines two state machines that imply two
types of applications, session-less and session-based applications. types of applications, session-less and session-based applications.
The primary difference between these types of applications is the The primary difference between these types of applications is the
lifetime of Session-Ids. lifetime of Session-Ids.
For session-based applications, the Session-Id is used to tie For session-based applications, the Session-Id is used to tie
multiple requests into a single session. multiple requests into a single session.
The Credit-Control application defined in [RFC4006] is an example of The Credit-Control application defined in [RFC4006] is an example of
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
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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 C.2.
D.2. Application Type Overload Implications C.2. Application Type Overload Implications
This section discusses considerations for mitigating overload This section discusses considerations for mitigating overload
reported by a Diameter entity. This discussion focuses on the type reported by a Diameter entity. This discussion focuses on the type
of application. Appendix D.3 discusses considerations for handling of application. Appendix C.3 discusses considerations for handling
various request types when the target server is known to be in an various request types when the target server is known to be in an
overloaded state. overloaded state.
These discussions assume that the strategy for mitigating the These discussions assume that the strategy for mitigating the
reported overload is to reduce the overall workload sent to the reported overload is to reduce the overall workload sent to the
overloaded entity. The concept of applying overload treatment to overloaded entity. The concept of applying overload treatment to
requests targeted for an overloaded Diameter entity is inherent to requests targeted for an overloaded Diameter entity is inherent to
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
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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 cleanup procedures. the session and any resulting session cleanup procedures.
D.3. Request Transaction Classification C.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:
A session-initiating request is the initial message that A session-initiating request is the initial message that
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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.
D.4. Request Type Overload Implications C.4. Request Type Overload Implications
The request classes identified in Appendix D.3 have implications on The request classes identified in Appendix C.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
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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.
Implementers 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 cleanup 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
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