draft-docdt-dime-ovli-00.txt   draft-docdt-dime-ovli-01.txt 
Diameter Maintenance and Extensions (DIME) J. Korhonen, Ed. Diameter Maintenance and Extensions J. Korhonen, Ed.
Internet-Draft Broadcom Communications (DIME) Broadcom Communications
Intended status: Standards Track S. Donovan Internet-Draft S. Donovan
Expires: April 24, 2014 B. Campbell Intended status: Standards Track B. Campbell
Oracle Expires: May 8, 2014 Oracle
October 21, 2013 November 4, 2013
Diameter Overload Indication Conveyance Diameter Overload Indication Conveyance
draft-docdt-dime-ovli-00.txt draft-docdt-dime-ovli-01.txt
Abstract Abstract
This specification documents a Diameter Overload Information This specification documents a Diameter Overload Control (DOC) base
Conveyance (DOIC) base solution and the dissemination of the overload solution and the dissemination of the overload report information.
report information.
Requirements Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 April 24, 2014. This Internet-Draft will expire on May 8, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Architectural Assumptions . . . . . . . . . . . . . . . . 6 3.1. Architectural Assumptions . . . . . . . . . . . . . . . . 6
3.1.1. Application Classification . . . . . . . . . . . . . 6 3.1.1. Application Classification . . . . . . . . . . . . . . 7
3.1.2. Application Type Overload Implications . . . . . . . 7 3.1.2. Application Type Overload Implications . . . . . . . . 8
3.1.3. Request Transaction Classification . . . . . . . . . 8 3.1.3. Request Transaction Classification . . . . . . . . . . 9
3.1.4. Request Type Overload Implications . . . . . . . . . 9 3.1.4. Request Type Overload Implications . . . . . . . . . . 10
3.1.5. Diameter Deployment Scenarios . . . . . . . . . . . . 10 3.1.5. Diameter Deployment Scenarios . . . . . . . . . . . . 11
3.1.6. Diameter Agent Behaviour . . . . . . . . . . . . . . 11 3.1.6. Diameter Agent Behaviour . . . . . . . . . . . . . . . 12
3.1.7. Simplified Example Architecture . . . . . . . . . . . 12 3.1.7. Simplified Example Architecture . . . . . . . . . . . 13
3.2. Conveyance of the Overload Indication . . . . . . . . . . 13 3.2. Conveyance of the Overload Indication . . . . . . . . . . 14
3.2.1. Negotiation and Versioning . . . . . . . . . . . . . 13 3.2.1. Negotiation and Versioning . . . . . . . . . . . . . . 14
3.2.2. Transmission of the Attribute Value Pairs . . . . . . 13 3.2.2. Transmission of the Attribute Value Pairs . . . . . . 14
3.3. Overload Condition Indication . . . . . . . . . . . . . . 14 3.3. Overload Condition Indication . . . . . . . . . . . . . . 15
4. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 14 4. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 15
4.1. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 14 4.1. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 15
4.2. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 16 4.2. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3. TimeStamp AVP . . . . . . . . . . . . . . . . . . . . . . 16 4.3. TimeStamp AVP . . . . . . . . . . . . . . . . . . . . . . 17
4.4. ValidityDuration AVP . . . . . . . . . . . . . . . . . . 17 4.4. ValidityDuration AVP . . . . . . . . . . . . . . . . . . . 17
4.5. ReportType AVP . . . . . . . . . . . . . . . . . . . . . 17 4.5. ReportType AVP . . . . . . . . . . . . . . . . . . . . . . 17
4.6. OC-Algorithm AVP . . . . . . . . . . . . . . . . . . . . 18 4.6. Reduction-Percentage AVP . . . . . . . . . . . . . . . . . 18
4.7. Algorithm-ID AVP . . . . . . . . . . . . . . . . . . . . 18 4.7. Attribute Value Pair flag rules . . . . . . . . . . . . . 19
4.8. Reduction-Percentage AVP . . . . . . . . . . . . . . . . 19 5. Overload Control Operation . . . . . . . . . . . . . . . . . . 19
4.9. Attribute Value Pair flag rules . . . . . . . . . . . . . 19 5.1. Overload Control Endpoints . . . . . . . . . . . . . . . . 19
5. Overload Control Operation . . . . . . . . . . . . . . . . . 20 5.2. Piggybacking Principle . . . . . . . . . . . . . . . . . . 23
5.1. Overload Control Endpoints . . . . . . . . . . . . . . . 20 5.3. Capability Announcement . . . . . . . . . . . . . . . . . 23
5.2. Piggybacking Principle . . . . . . . . . . . . . . . . . 20 5.3.1. Request Message Initiator Endpoint Considerations . . 24
5.3. Capability Negotiation . . . . . . . . . . . . . . . . . 21 5.3.2. Answer Message Initiating Endpoint Considerations . . 24
5.3.1. Request Message Initiator Endpoint Considerations . . 21 5.4. Protocol Extensibility . . . . . . . . . . . . . . . . . . 25
5.3.2. Answer Message Initiating Endpoint Considerations . . 22 5.5. Overload Report Processing . . . . . . . . . . . . . . . . 25
5.4. Protocol Extensibility . . . . . . . . . . . . . . . . . 23 5.5.1. Sender Endpoint Considerations . . . . . . . . . . . . 25
5.5. Overload Report Processing . . . . . . . . . . . . . . . 23 5.5.2. Receiver Endpoint Considerations . . . . . . . . . . . 25
5.5.1. Sender Endpoint Considerations . . . . . . . . . . . 23 6. Transport Considerations . . . . . . . . . . . . . . . . . . . 25
5.5.2. Receiver Endpoint Considerations . . . . . . . . . . 23 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
6. Transport Considerations . . . . . . . . . . . . . . . . . . 23 7.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 26
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 7.2. New registries . . . . . . . . . . . . . . . . . . . . . . 26
7.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 24 8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
7.2. New registries . . . . . . . . . . . . . . . . . . . . . 24 8.1. Potential Threat Modes . . . . . . . . . . . . . . . . . . 27
8.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 28
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24 8.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 28
8.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 25 8.4. End-to End-Security Issues . . . . . . . . . . . . . . . . 28
8.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 26 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 26 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30
8.4. End-to End-Security Issues . . . . . . . . . . . . . . . 26 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28 11.1. Normative References . . . . . . . . . . . . . . . . . . . 30
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 11.2. Informative References . . . . . . . . . . . . . . . . . . 31
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 Appendix A. Issues left for future specifications . . . . . . . . 31
11.1. Normative References . . . . . . . . . . . . . . . . . . 28 A.1. Additional traffic abatement algorithms . . . . . . . . . 31
11.2. Informative References . . . . . . . . . . . . . . . . . 29 A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . . 31
Appendix A. Issues left for future specifications . . . . . . . 29 A.3. DIAMETER_TOO_BUSY clarifications . . . . . . . . . . . . . 31
A.1. Additional traffic abatement algorithms . . . . . . . . . 29 Appendix B. Conformance to Requirements . . . . . . . . . . . . . 32
A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 29 Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 41
A.3. DIAMETER_TOO_BUSY clarifications . . . . . . . . . . . . 29 C.1. 3GPP S6a interface overload indication . . . . . . . . . . 41
A.4. Load . . . . . . . . . . . . . . . . . . . . . . . . . . 30 C.2. 3GPP PCC interfaces overload indication . . . . . . . . . 41
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 30 C.3. Mix of Destination-Realm routed requests and
B.1. 3GPP S6a interface overload indication . . . . . . . . . 30 Destination-Host reouted requests . . . . . . . . . . . . 41
B.2. 3GPP PCC interfaces overload indication . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41
B.3. Mix of Destination-Realm routed requests and Destination-
Host reouted requests . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction 1. Introduction
This specification defines a base solution for the Diameter Overload This specification defines a base solution for the Diameter Overload
Information Conveyance (DOIC). The requirements for the solution are Control (DOC). The requirements for the solution are described and
described and discussed in the corresponding design requirements discussed in the corresponding design requirements document
document [I-D.ietf-dime-overload-reqs]. Note that the overload [I-D.ietf-dime-overload-reqs]. Note that the overload control
control solution defined in this specification does not address all solution defined in this specification does not address all the
the requirements listed in [I-D.ietf-dime-overload-reqs]. A number requirements listed in [I-D.ietf-dime-overload-reqs]. A number of
of overload control related features are left for the future overload control related features are left for the future
specifications. See Appendix A for more detailed discussion on specifications. See Appendix A for more detailed discussion on
those. those.
The solution defined in this specification addresses the Diameter
overload control between two endpoints (see Section 5.1).
Furthermore, the solution is designed to apply to existing and future
Diameter applications, requires no changes to the Diameter base
protocol [RFC6733] and is deployable in environments where some
Diameter nodes do not implement the Diameter overload control
solution defined in this specification.
2. Terminology and Abbreviations 2. Terminology and Abbreviations
Server Farm Server Farm
A set of Diameter servers that can handle any request for a given A set of Diameter servers that can handle any request for a given
set of Diameter applications. While these servers support the set of Diameter applications. While these servers support the
same set of applications, they do not necessarily all have the same set of applications, they do not necessarily all have the
same capacity. An individual server farm might also support a same capacity. An individual server farm might also support a
subset of the users for a Diameter Realm. subset of the users for a Diameter Realm.
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Overload Management: Overload Management:
The SFE is the entity that understands the consolidated overload The SFE is the entity that understands the consolidated overload
state for the server farm. Just as it is outside the scope of state for the server farm. Just as it is outside the scope of
this document to specify how a Diameter server calculates its this document to specify how a Diameter server calculates its
overload state, it is also outside the scope of this document to overload state, it is also outside the scope of this document to
specify how an SFE calculates the overload state for the set of specify how an SFE calculates the overload state for the set of
servers. This document describes how the SFE communicates servers. This document describes how the SFE communicates
Overload information to Diameter Clients. Overload information to Diameter Clients.
[OpenIssue: Does this mean the way servers communicate overload
info to an SFE is also out of scope? It would be nice if the
mechanism is useful for that purpose.]
Topology Hiding: Topology Hiding:
Topology Hiding is loosely defined as ensuring that no Diameter Topology Hiding is loosely defined as ensuring that no Diameter
topology information about the server farm can be discovered from topology information about the server farm can be discovered from
Diameter messages sent outside a predefined boundary (typically an Diameter messages sent outside a predefined boundary (typically an
administrative domain). This includes obfuscating identifiers and administrative domain). This includes obfuscating identifiers and
address information of Diameter entities in the server farm. It address information of Diameter entities in the server farm. It
can also include hiding the number of various Diameter entities in can also include hiding the number of various Diameter entities in
the server farm. Identifying information can occur in many the server farm. Identifying information can occur in many
Diameter Attribute-Value Pairs (AVPs), including Origin-Host, Diameter Attribute-Value Pairs (AVPs), including Origin-Host,
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agent rejecting requests with appropriate error responses. agent rejecting requests with appropriate error responses.
Clients and agents can also choose to redirect throttled requests Clients and agents can also choose to redirect throttled requests
to some other entity or entities capable of handling them. to some other entity or entities capable of handling them.
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 actually overloaded node.) may not be the actually overloaded node.)
Reacting Node Reacting Node
A Diameter node that consumes and acts upon a report. Note that A Diameter node that consumes and acts upon a report. Note that
"act upon" does not necessarily mean the reacting node applies an "act upon" does not necessarily mean the reacting node applies an
abatement algorithm; it might decide to delegate that downstream, abatement algorithm; it might decide to delegate that downstream,
in which case it also becomes a "reporting node". in which case it also becomes a "reporting node".
OLR Oveload Report.
3. Solution Overview 3. Solution Overview
3.1. Architectural Assumptions 3.1. Architectural Assumptions
This section describes the high-level architectural and semantic This section describes the high-level architectural and semantic
assumptions that underly the Diameter Overload Control Mechanism. assumptions that underly the Diameter Overload Control Mechanism.
3.1.1. Application Classification 3.1.1. Application Classification
The following is a classification of Diameter applications and The following is a classification of Diameter applications and
requests. This discussion is meant to document factors that play requests. This discussion is meant to document factors that play
into decisions made by the Diameter entity responsible for handling into decisions made by the Diameter identity responsible for handling
overload reports. 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. The primary types of applications, session-less and session-based. The primary
differentiator between these types of applications is the lifetime of differentiator between these types of applications is the lifetime of
Session-IDs. 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.
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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: Requests within a stateless application have Stateless applications: Requests within a stateless application have
no relationship to each other. The 3GPP defined S13 application no relationship to each other. The 3GPP defined S13 application
is an example of a stateless application. is an example of a stateless application.
Pseudo-session applications: While this class of application does Pseudo-session applications: While this class of application does
not use the Diameter Session-ID AVP to correlate requests, there not use the Diameter Session-ID AVP to correlate requests, there
is an implied ordering of transactions defined by the application. is an implied ordering of transactions defined by the application.
Transactions in a pseudo-session typically need to be handled by The 3GPP defined Cx application [reference] is an example of a
the same server. The 3GPP defined Cx application [reference] is pseudo-session application.
an example of a pseudo-session application.
[OpenIssue: Do we assume that all requests in a pseudo-session
typically need to go to the same server?]
The accounting application defined in [RFC6733] and the Credit- The accounting application defined in [RFC6733] and the Credit-
Control application defined in [RFC4006] are examples of Diameter Control application defined in [RFC4006] are examples of Diameter
session-based applications. session-based applications.
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 Section 3.1.2. into consideration, as discussed in Section 3.1.2.
3.1.2. Application Type Overload Implications 3.1.2. Application Type Overload Implications
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generally means that transactions later in the sequence of generally means that transactions later in the sequence of
transactions should be given more favorable treatment than transactions should be given more favorable treatment than
messages earlier in the sequence. This is because more work has messages earlier in the sequence. This is because more work has
already been done by the Diameter network for those transactions already been done by the Diameter network for those transactions
that occur later in the sequence. Rejecting them could result in that occur later in the sequence. Rejecting them could result in
increasing the load on the network as the transactions earlier in increasing the load on the network as the transactions earlier in
the sequence might also need to be repeated. the sequence might also need to be repeated.
Stateful applications: Overload handling for stateful applications Stateful applications: Overload handling for stateful applications
must take into consideration the work associated with setting up must take into consideration the work associated with setting up
an maintaining a session. As such, the Diameter entity handling an maintaining a session. As such, the entity handling overload
overload for a stateful application might tend to reject new of a Diameter entity for a stateful application might tend to
session requests before rejecting intra-session requests. In reject new session requests before rejecting intra-session
addition, session ending requests might be given a lower chance of requests. In addition, session ending requests might be given a
being rejected, since rejecting session ending requests could lower priority of being rejected as rejecting session ending
result in session status being out of sync between the Diameter requests could result in session status being out of sync between
clients and servers, while successful execution might actually the Diameter clients and servers. Nodes that reject mid-session
free up resources. Nodes that reject mid-session requests will requests will need to consider whether the rejection invalidates
need to consider whether the rejection invalidates the session, the session, and any session clean-up that may be required.
and any session clean-up that may be required.
3.1.3. Request Transaction Classification 3.1.3. Request Transaction Classification
Independent Request: An independent request is not a part of a Independent Request: An independent request is not a part of a
Diameter session and, as such, the lifetime of the session-id is Diameter session and, as such, the lifetime of the session-id is
constrained to an individual transaction. constrained to an individual transaction.
Session-Initiating Request: A session-initiating request is the Session-Initiating Request: A session-initiating request is the
initial message that establishes a Diameter session. The ACR initial message that establishes a Diameter session. The ACR
message defined in [RFC6733] is an example of a session-initiating message defined in [RFC6733] is an example of a session-initiating
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Correlated Session-Initiating Request: There are cases, most notably Correlated Session-Initiating Request: There are cases, most notably
in the 3GPP PCC architecture, where multiple Diameter sessions are in the 3GPP PCC architecture, where multiple Diameter sessions are
correlated and must be handled by the same Diameter server. This correlated and must be handled by the same Diameter server. This
is a special case of a Session-Initiating Request. Gx CCR-I is a special case of a Session-Initiating Request. Gx CCR-I
requests and Rx AAR messages are examples of correlated session- requests and Rx AAR messages are examples of correlated session-
initiating requests. initiating requests.
[OpenIssue: The previous paragraph needs references.] [OpenIssue: The previous paragraph needs references.]
Intra-Session Request: An intra-session request is a request that Intra-Session Request: An intra session request is a request that
uses a session-id for an already established session. An intra uses a session-id for an already established request. An intra
session request generally needs to be delivered to the server that session request generally needs to be delivered to the server that
handled the session creating request for the session. The STR handled the session creating request for the session. The STR
message defined in [RFC6733] is an example of an intra-session message defined in [RFC6733] is an example of an intra-session
requests. CCR-U and CCR-T requests defined in [RFC4006] are requests. CCR-U and CCR-T requests defined in [RFC4006] are
further examples of intra-session requests. further examples of intra-session requests.
Pseudo-Session Requests: Pseudo session requests are independent Pseudo-Session Requests: Pseudo session requests are independent
requests and, as such, the request transactions are not tied requests and, as such, the request transactions are not tied
together using the Diameter session-id. There exist Diameter together using the Diameter session-id. There exist 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
application are examples of pseudo-session requests. application are examples of pseudo-session requests.
[OpenIssue: This section offers discusses priorities around
throttling of requests. Should we also discuss considerations for
diverting requests non-overloaded destinations?]
3.1.4. Request Type Overload Implications 3.1.4. Request Type Overload Implications
The request classes identified in Section 3.1.3 have implications on The request classes identified in Section 3.1.3 have implications on
decisions about which requests should be throttled first. decisions about which requests should be throttled first.
Independent requests: Independent requests can be given equal Independent requests: Independent requests can be given equal
treatment when making throttling decisions. treatment when making throttling decisions.
Session-creating requests: Session-creating requests represent more Session-creating requests: Session-creating requests represent more
work than independent or intra-session requests. As such, work than independent or intra-session requests. As such,
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3.1.5. Diameter Deployment Scenarios 3.1.5. Diameter Deployment Scenarios
This section discusses various Diameter network deployment scenarios This section discusses various Diameter network deployment scenarios
and the implications of those deployment models on handling of and the implications of those deployment models on handling of
overload reports. overload reports.
The scenarios vary based on the following: The scenarios vary based on the following:
o The presence or absence of Diameter agents o The presence or absence of Diameter agents
o Which Diameter entities support the DOIC extension o Which Diameter entities support the DOC extension
o The amount of the network topology understood by Diameter clients o The amount of the network topology understood by Diameter clients
o The complexity of the Diameter server deployment for a Diameter o The complexity of the Diameter server deployment for a Diameter
application application
o Number of Diameter applications supported by Diameter clients and o Number of Diameter applications supported by Diameter clients and
Diameter servers Diameter servers
Without consideration for which elements support the DOIC extension, Without consideration for which elements support the DOC extension,
the following is a representative list of deployment scenarios: the following is a representative list of deployment scenarios:
o Client --- Server o Client --- Server
o Client --- Multiple equivalent servers o Client --- Multiple equivalent servers
o Client --- Agent --- Multiple equivalent servers o Client --- Agent --- Multiple equivalent servers
o Client --- Agent [ --- Agent ] --- Partitioned server o Client --- Agent [ --- Agent ] --- Partitioned server
o Client --- Edge Agent [ --- Edge Agent] --- { Multiple Equivalent o Client --- Edge Agent [ --- Edge Agent] --- { Multiple Equivalent
Servers | Partitioned Servers } Servers | Partitioned Servers }
o Client --- Session Correlating Agent --- Multiple Equivalent o Client --- Session Correlating Agent --- Multiple Equivalent
Servers Servers
[OpenIssue: Do the "multiple equivalent servers" cases change for [OpenIssue: Do the "multiple equivalent servers" cases change for
session-stateful applications? Do we need to distinguish equivalence session-stateful applications? Do we need to distinguish equivalence
for session-initiation requests vs intra-session requests?] for session-initiation requests vs intra-session requests?]
skipping to change at page 11, line 14 skipping to change at page 12, line 9
o Client --- Edge Agent [ --- Edge Agent] --- { Multiple Equivalent o Client --- Edge Agent [ --- Edge Agent] --- { Multiple Equivalent
Servers | Partitioned Servers } Servers | Partitioned Servers }
o Client --- Session Correlating Agent --- Multiple Equivalent o Client --- Session Correlating Agent --- Multiple Equivalent
Servers Servers
[OpenIssue: Do the "multiple equivalent servers" cases change for [OpenIssue: Do the "multiple equivalent servers" cases change for
session-stateful applications? Do we need to distinguish equivalence session-stateful applications? Do we need to distinguish equivalence
for session-initiation requests vs intra-session requests?] for session-initiation requests vs intra-session requests?]
The following is a list of representative DOIC deployment scenarios: The following is a list of representative DOC deployment scenarios:
o Direct connection between a DOIC client and a DOIC server
o DOIC client --- one or more non-DOIC agent(s) --- DOIC server o Direct connection between a DOC client and a DOC server
o DOIC client --- DOIC agent --- DOIC server o DOC client --- non-DOC agent --- DOC server
o Non-DOIC client --- DOIC agent --- DOIC server o DOC client --- DOC agent --- DOC server
o Non-DOIC client --- DOIC agent --- Mix of DOIC and non-DOIC o Non-DOC client --- DOC agent --- DOC server
servers
o DOIC client --- DOIC agent --- Partitioned/Segmented DOIC server o Non-DOC client --- DOC agent --- Mix of DOC and non-DOC servers
o DOIC client --- DOIC agent --- DOIC agent --- Partitioned/ o DOC client --- agent --- Partitioned/Segmented DOC server
Segmented DOIC server
o DOIC client --- DOIC edge agent --- DOIC edge agent --- DOIC o DOC client --- agent --- agent --- Partitioned/Segmented DOC
server server
o DOC client --- edge agent --- edge agent --- DOC server
[OpenIssue: In the last 3 list entries, are the agents DOC or non-
DOC?]
3.1.6. Diameter Agent Behaviour 3.1.6. Diameter Agent Behaviour
In the context of the Diameter Overload Indication Conveyance (DOIC) In the context of the Diameter Overload Indication Conveyance (DOIC)
and reacting to the overload information, the functional behaviour of and reacting to the overload information, the functional behaviour of
Diameter agents in front of servers, especially Diameter proxies, Diameter agents in front of servers, especially Diameter proxies,
needs to be defined. This is important because agents may actively needs to be common. This is important because agents may actively
participate in the handling of overload conditions. For example, participate in the handling of an overload conditions. For example,
they may make intelligent next hop selection decisions based on they may make intelligent next hop selection decisions based on
overload conditions, or aggregate overload information to be overload conditions, or aggregate overload information to be
disseminated downstream. Diameter agents may have other deployment disseminated downstream. Diameter agents may have other deployment
related tasks that are not defined in the Diameter base protocol related tasks that are not defined in the Diameter base protocol
[RFC6733]. These include, among other tasks, topology hiding, and [RFC6733]. These include, among other tasks, topology hiding, and
acting as a server front end for a server farm of real Diameter acting as a server front end for a server farm of real Diameter
servers. servers.
Since the solution defined in this specification must not break the Since the solution defined in this specification must not break the
Diameter base protocol assumptions at any time, great care has to be Diameter base protocol [RFC6733] at any time, great care has to be
taken not to assume functionality from the Diameter agents that would taken not to assume functionality from the Diameter agents that would
break base protocol behavior, or to assume agent functionality beyond break base protocol behavior, or to assume agent functionality beyond
the Diameter base protocol. Effectively this means the following the Diameter base protocol. Effectively this means the following
from a Diameter agent: from a Diameter agent:
o If a Diameter agent presents itself as the "end node", perhaps o If a Diameter agent presents itself as the "end node", perhaps
acting as a topology hiding SFE, the DOIC mechanism MUST NOT leak acting as an topology hiding SFE, the DOC mechanism MUST NOT leak
information of the Diameter nodes behind it. From the Diameter information of the Diameter nodes behind it. From the Diameter
client point of view the final destination to its requests and the client point of view the final destination to its requests and the
original source for the answers MUST be the Diameter agent. This original source for the answers MUST be the Diameter agent. This
requirement means that such a Diameter agent acts as a back-to- requirement means that such a Diameter agent acts as a back-to-
back-agent for DOIC purposes. How the agent in this case appears back-agent for DOC purposes. How the agent in this case appears
to the Diameter nodes it is representing (i.e. the real Diameter to the Diameter nodes it is representing (i.e. the real Diameter
servers), is an implementation and a deployment specific within servers), is an implementation and a deployment specific within
the realm the Diameter agent is deployed. the realm the Diameter agent is deployed.
o This requirement also implies that if the Diameter agent does not o This requirement also implies that if the Diameter agent does not
impersonate the servers behind it, the Diameter dialogue is impersonate the servers behind it, the Diameter dialogue is
established between clients and servers and any overload established between clients and servers and any overload
information received by a client would be from a given server information received by a client would be from a given server
identified by the Origin-Host identity. identified by the Origin-Host identity.
skipping to change at page 12, line 38 skipping to change at page 13, line 34
topology hiding or SFIM in order to do so. We cannot assume that an topology hiding or SFIM in order to do so. We cannot assume that an
OLR is always "from" or "about" the Origin-Host. Also, the section OLR is always "from" or "about" the Origin-Host. Also, the section
seems to assume that topology hiding agents act as b2b overload seems to assume that topology hiding agents act as b2b overload
agents, but non-topology hiding agents never do. It don't think agents, but non-topology hiding agents never do. It don't think
that's the right abstraction. It's possible that topology-hiding that's the right abstraction. It's possible that topology-hiding
agents must do this, but I don't think we can preclude non-topology agents must do this, but I don't think we can preclude non-topology
hiding agents from also doing it, at least some of the time.] hiding agents from also doing it, at least some of the time.]
3.1.7. Simplified Example Architecture 3.1.7. Simplified Example Architecture
Figure 1 illustrates the simplified architecture for Diameter
overload control. See Section 5.1 for more discussion and details
how different Diameter nodes fit into the architecture from the DOIC
point of view.
Realm X Other Realms Realm X Other Realms
<--------------------------------------> <----------------------> <--------------------------------------> <---------------------->
+--^-----+ : (optional) : +--^-----+ : (optional) :
|Diameter| : : |Diameter| : :
|Server A|--+ .--. : +---^----+ : .--. |Server A|--+ .--. : +---^----+ : .--.
+--------+ | _( `. : |Diameter| : _( `. +---^----+ +--------+ | _( `. : |Diameter| : _( `. +---^----+
+--( )--:-| Agent |-:--( )--|Diameter| +--( )--:-| Agent |-:--( )--|Diameter|
+--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client | +--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client |
|Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+ |Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+
|Server B| : : |Server B| : :
+---^----+ : : +---^----+ : :
Overload Indication A Overload Indication A' Overload Indication A Overload Indication A'
1) <----------------------> <----------------------> 1) <----------------------> <---------------------->
standard base protocol standard base protocol standard base protocol standard base protocol
End-to-end Overload Indication End-to-end Overload Indication
2) <-----------------------------------------------> 2) <----------------------------------------------->
standard base protocol standard base protocol
Simplified architecture choices for overload indication delivery Figure 1: Simplified architecture choices for overload indication
delivery
[OpenIssue: Need to clarify the meaning of option 2 with the agent in
place. Does this mean the agent is not an Overload Endpoint?]
3.2. Conveyance of the Overload Indication 3.2. Conveyance of the Overload Indication
The following features describe new Diameter AVPs used for sending The following features describe new Diameter AVPs used for sending
overload reports, and for declaring support for certain DOIC overload reports, and for declaring support for certain DOC features.
features.
3.2.1. Negotiation and Versioning 3.2.1. Negotiation and Versioning
Since the Diameter overload control mechanism is also designed to Since the Diameter overload control mechanism is also designed to
work over existing application (i.e., the piggybacking principle), a work over existing application (i.e., the piggybacking principle), a
proper negotiation is hard to accomplish. The "capability proper negotiation is hard to accomplish. The "capability
negotiation" is based on the existense of specific non-mandatory negotiation" is based on the existense of specific non-mandatory APV,
APVs, such as the OC-Feature-Vector AVP (see Section 4.1. Although such as the OC-Feature-Vector AVP (see Section 4.1. Although the OC-
the OC-Feature-Vector AVP can be used to advertise a certain set of Feature-Vector AVP can be used to advertise a certain set of new or
new or existing Diameter overload control capabilities, it is not a existing Diameter overload control capabilities, it is not a
versioning solution per se, however, it can be used to achieve the versioning solution per se, however, it can be used to achieve the
same result. same result.
3.2.2. Transmission of the Attribute Value Pairs 3.2.2. Transmission of the Attribute Value Pairs
The Diameter overload control APVs SHOULD always be sent as an The Diameter overload control APVs SHOULD always be sent as an
optional AVPs. This requirement stems from the fact that optional AVPs. This requirement stems from the fact that
piggybacking overload control information on top of existing piggybacking overload control information on top of existing
application cannot really use AVPs with the M-bit set. However, application cannot really use AVPs with the M-bit set. However,
there are certain exceptions as explained in Section 5.4. there are certain exceptions as explained in Section 5.4.
From the Diameter overload control functionality point of view, the From the Diameter overload control functionality point of view, the
"Reacting node" is always the requester of the overload report "Reacting node" is always the requester of the overload report
information and the "Reporting node" is the provider of the overload information and the "Reporting node" is the provider of the overload
report. The overload report or the capability information in the report. The overload report or the capability information in the
request message is always interpreted as an announcement of a request message is always interpreted as an announcement of a
"capability". The capability information and the overload report in "capability". The overload report and the capability information in
the answer is always interpreted respectively as a report of the answer is always interpreted as a report of supported commond
supported common functionality and as a status report of an overload functionality and as a status report of an overload condition (of a
condition. node).
3.3. Overload Condition Indication 3.3. Overload Condition Indication
Diameter nodes can request a reduction in offered load by indicating Diameter nodes can request a reduction in offered load by indicating
an overload condition in the form of an overload report. The an overload condition in the form of an overload report. The
overload report contains information about how much load should be overload report contains information about how much load should be
reduced, and may contain other information about the overload reduced, and may contain other information about the overload
condition. This information is encoded in Diameter Attribute Value condition. This information is encoded in Diameter Attribute Value
Pairs (AVPs). Pairs (AVPs).
skipping to change at page 14, line 35 skipping to change at page 15, line 37
capabilities and extensions. capabilities and extensions.
4. Attribute Value Pairs 4. Attribute Value Pairs
This section describes the encoding and semantics of Overload This section describes the encoding and semantics of Overload
Indication Attribute Value Pairs (AVPs). Indication Attribute Value Pairs (AVPs).
4.1. OC-Feature-Vector AVP 4.1. OC-Feature-Vector AVP
The OC-Feature-Vector AVP (AVP code TBD1) is type of Unsigned64 and The OC-Feature-Vector AVP (AVP code TBD1) is type of Unsigned64 and
contains a 64 bit flags field of supported capabilities of an contains a 64 bit flags field of announced capabilities of an
overload control endpoint. Receiving the OC-Feature-Vector AVP with overload control endpoint. Sending or receiving the OC-Feature-
the value 0 indicates that two endpoints do not share a single common Vector AVP with the value 0 indicates that the endpoint only support
capability (or a capability they could agree based on the local the capabilities defined in this specification.
policy and/or configuration). A request message initiating endpoint
(a reacting node) MUST NOT send the OC-Feature-Vector AVP with the
value 0.
[OpenIssue: We need further discussion on whether the "no shared
capability" case is allowed, or if we guarantee certain basic levels
of compatibility by using mandatory-to-support defaults.]
An overload control endpoint (a reacting node) MAY include this AVP
to indicate its capabilities to the other overload control endpoint
(the reporting node). For example, the endpoint (reacting node) may
indicate which traffic abatement algorithms it supports in addition
to the default.
[OpenIssue: There is an ongoing discussion as to whether the OC- An overload control endpoint (a reacting node) includes this AVP to
Feature-Vector AVP should be an optional (MAY vs MUST) way to declare indicate its capabilities to the other overload control endpoint (the
support, where new Diameter applications could define other ways, or reporting node). For example, the endpoint (reacting node) may
whether this should be the "one true" way. The latter approach indicate which (future defined) traffic abatement algorithms it
prevents agents that are not application aware from supporting DOIC, supports in addition to the default.
but the latter may reduce the flexibility for defining new
applications.]
During the message exchange the overload control endpoints express During the message exchange the overload control endpoints express
their common set of supported capabilities. The endpoint sending a their common set of supported capabilities. The endpoint sending a
request (the reacting node) includes the OC-Feature-Vector AVP with request (the reacting node) includes the OC-Feature-Vector AVP with
those flags set that correspond what it supports. The endpoint that those flags set that correspond what it supports. The endpoint that
sends the answer (the reporting node) also includes the OC-Feature- sends the answer (the reporting node) also includes the OC-Feature-
Vector AVP with flags set to describe the capabilities it both Vector AVP with flags set to describe the capabilities it both
supports and agrees with the request sender (e.g., based on the local supports and agrees with the request sender (e.g., based on the local
policy and/or configuration). The answer sending endpoint (the policy and/or configuration). The answer sending endpoint (the
reporting node) does not need to advertise those capabilities it is reporting node) does not need to advertise those capabilities it is
not going to use with the request sending endpoint (the reacting not going to use with the request sending endpoint (the reacting
node). node).
Note that when the OC-Feature-Vector AVP is used together with the This specification does not define any additional capability flag.
OC-OLR AVPs, the contents of the announced features and the contents The implicity capability (all flags set to zero) indicates the
of the OC-OLR AVPs MUST NOT contradict each other. In a case they support for this specification only.
do, the receiver of contradicting information SHOULD discard the AVPs
as if they were not present to start with and log the event.
In some cases a single flag bit in the OC-Feature-Vector AVP is not
verbose enough to describe all of the advertised capability. This
concerns the situation where the OC-Feature-Vector AVP is sent in a
request message. In this particular case, the OC-OLR AVP MUST
contain the rest of the required parameters. For example, if the
advertised capability concerns an abatement algorithm that needs more
algorithm specific parameters to agree on, then the OC-OLR abatement
algorithm specific AVPs MUST contain the rest of the parameter
information.
The following capabilities are defined in this document:
OLR_DEFAULT_ALGO (0x0000000000000001)
When this flag is set by the overload control endpoint it means
that the default traffic abatement (loss) algorithm is supported.
4.2. OC-OLR AVP 4.2. OC-OLR AVP
The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the
necessary information to convey an overload report. OC-OLR may also necessary information to convey an overload report. OC-OLR may also
be used to convey additional information about an extension that is be used to convey additional information about an extension that is
declared in the OC-Feature-Vector AVP. declared in the OC-Feature-Vector AVP.
Since the OC-OLR AVP contains information that may be critical for
handling overload conditions, reporting nodes SHOULD place the AVP as
early in the Diameter message as possible.
The OC-OLR AVP does not contain explicit information to which The OC-OLR AVP does not contain explicit information to which
application it applies to and who inserted the AVP or whom the application it applies to and who inserted the AVP or whom the
specific OC-OLR AVP concerns to. Both these information is specific OC-OLR AVP concerns to. Both these information is
implicitly learned from the encapsulating Diameter message/command. implicitly learned from the encapsulating Diameter message/command.
The application the OC-OLR AVP applies to is the same as the The application the OC-OLR AVP applies to is the same as the
Application-Id found in the Diameter message header. The identity Application-Id found in the Diameter message header. The identity
the OC-OLR AVP concerns is determined from the Origin-Host AVP found the OC-OLR AVP concerns is determined from the Origin-Host AVP found
from the encapsulating Diameter message. from the encapsulating Diameter command.
[OpenIssue: There is ongoing discussion on whether it's best to infer
information like application, realm, reporting node identity, etc,
from the enclosing Diameter message vs making the overload reports
self-contained.]
OC-OLR ::= < AVP Header: TBD2 > OC-OLR ::= < AVP Header: TBD2 >
< TimeStamp > < TimeStamp >
[ Reduction-Percentage ]
[ ValidityDuration ] [ ValidityDuration ]
[ ReportType ] [ ReportType ]
* [ OC-Algorithm ]
* [ AVP ] * [ AVP ]
The TimeStamp AVP indicates when the original OC-OLR AVP with the The TimeStamp AVP indicates when the original OC-OLR AVP with the
current content was created. It is possible to replay the same OC- current content was created. It is possible to replay the same OC-
OLR AVP multiple times between the overload endpoints, however, when OLR AVP multiple times between the overload endpoints, however, when
the OC-OLR AVP content changes or the other information sending the OC-OLR AVP content changes or the other information sending
endpoint wants the receiving endpoint to update its overload control endpoint wants the receiving endpoint to update its overload control
information, then the TimeStamp AVP MUST contain a new value. information, then the TimeStamp AVP MUST contain a new value.
[OpenIssue: Is this necessarily a timestamp, or is it just a sequence [OpenIssue: Is this necessarily a timestamp, or is it just a sequence
number that can be implemented as a timestamp? We should also number that can be implemented as a timestamp? Is this timestamp
used to calculate expiration time? (propose no.). We should also
consider whether either a timestamp or sequence number is needed for consider whether either a timestamp or sequence number is needed for
protection against replay attacks.] protection against replay attacks.]
4.3. TimeStamp AVP 4.3. TimeStamp AVP
The TimeStamp AVP (AVP code TBD3) is type of Time. Its usage in the The TimeStamp AVP (AVP code TBD3) is type of Time. Its usage in the
context of the overload control is described in Section 4.2. From context of the overload control is described in Section 4.2. From
the functionality point of view, the TimeStamp AVP is merely used as the functionality point of view, the TimeStamp AVP is merely used as
a non-volatile increasing counter between two overload control a non-volatile increasing counter between two overload control
endpoints. endpoints.
4.4. ValidityDuration AVP 4.4. ValidityDuration AVP
The ValidityDuration AVP (AVP code TBD4) is type of Unsigned32 and The ValidityDuration AVP (AVP code TBD4) is type of Unsigned32 and
describes the number of seconds the OC-OLR AVP and its content is describes the number of seconds the OC-OLR AVP and its content is
skipping to change at page 17, line 19 skipping to change at page 17, line 23
4.4. ValidityDuration AVP 4.4. ValidityDuration AVP
The ValidityDuration AVP (AVP code TBD4) is type of Unsigned32 and The ValidityDuration AVP (AVP code TBD4) is type of Unsigned32 and
describes the number of seconds the OC-OLR AVP and its content is describes the number of seconds the OC-OLR AVP and its content is
valid since the creation of the OC-OLR AVP (as indicated by the valid since the creation of the OC-OLR AVP (as indicated by the
TimeStamp AVP). TimeStamp AVP).
A timeout of the overload report has specific concerns that need to A timeout of the overload report has specific concerns that need to
be taken into account by the endpoint acting on the earlier received be taken into account by the endpoint acting on the earlier received
overload report(s). Section 4.8 discusses the impacts of timeout in overload report(s). Section 4.6 discusses the impacts of timeout in
the scope of the traffic abatement algorithms. the scope of the traffic abatement algorithms.
As a general guidance for implementations it is RECOMMENDED never to As a general guidance for implementations it is RECOMMENDED never to
let any overload report to timeout. Rather, an overload endpoint let any overload report to timeout. Rather, an overload endpoint
should explicitly signal either the continuance of the overload should explicitly signal, e.g. the end of overload condition. This
condition by sending an new overload report. This new report would leaves no need for the other overload endpoint to reason or guess the
indicate a continuance of the overload condition by including a non- condition the other endpoint is at.
zero ValidityDuration value, or indicate the end of the condition by
including a zero value. This approach leaves no need for the
reacting node to reason or guess the current condition of the
reporting node.
4.5. ReportType AVP 4.5. ReportType AVP
The ReportType AVP (AVP code TBD5) is type of Enumerated. The value The ReportType AVP (AVP code TBD5) is type of Enumerated. The value
of the AVP describes what the overload report concerns. The of the AVP describes what the overload report concerns. The
following values are initially defined: following values are initially defined:
0 Reserved. 0 Reserved.
1 Destination-Host report. The overload treatment should apply to 1 Destination-Host report. The overload treatment should apply to
skipping to change at page 18, line 6 skipping to change at page 18, line 6
2 Realm (aggregated) report. The overload treatment should apply to 2 Realm (aggregated) report. The overload treatment should apply to
all requests bound for the overloaded realm. all requests bound for the overloaded realm.
The ReportType AVP is envisioned to be useful for situations where a The ReportType AVP is envisioned to be useful for situations where a
reacting node needs to apply different overload treatments for reacting node needs to apply different overload treatments for
different "types" of overload. For example, the reacting node(s) different "types" of overload. For example, the reacting node(s)
might need to throttle requests that are targeted to a specific might need to throttle requests that are targeted to a specific
server by the presence of a Destination-Host AVP than for requests server by the presence of a Destination-Host AVP than for requests
that can be handled by any server in a realm. The example in that can be handled by any server in a realm. The example in
Appendix B.3 illustrates this usage. Appendix C.3 illustrates this usage.
[OpenIssue: There is an ongoing discussion about whether the [OpenIssue: There is an ongoing discussion about whether the
ReportType AVP is the right way to solve that issue, and whether it's ReportType AVP is the right way to solve that issue, and whether it's
needed at all.] needed at all.]
[OpenIssue: ReportType should probably be extensible, and have its 4.6. Reduction-Percentage AVP
own IANA table.]
4.6. OC-Algorithm AVP
The OC-Algorithm AVP (AVP code TBD6) is type of Grouped. The AVP
contains the necessary sub-AVPs and information for the use for the
traffic abatement algorithm. The OC-Algorithm AVP serves as a
generic template for all future traffic abatement algorithms.
This specification defines an identifier for the default (loss)
algorithm (see Section 4.1 for the OC-Feature-Vector flag
corresponding to the algorithm), as well as the format and meaning of
that algorithm's input parameter.
OC-Algorithm ::= < AVP Header: TBD6 >
< Algorithm-ID >
[ Reduction-Percentage ]
* [ AVP ]
As already discussed in Section 4.1 in certain cases, the Algorithm
AVP MAY be used in a request message together with the OC-Feature-
Vector AVP to describe the detailed parameterization of the abatement
algorithm to the other endpoint (i.e. to the reporting node). This
implies, the possible future algorithms and their sub-AVPs must be
designed accordingly.
4.7. Algorithm-ID AVP
The Algorithm-ID AVP (AVP code TBD7) is type of Enumerated and
identifies the traffic abatement algorithm the OC-Algorithm AVP
"describes" and implements. This specification defines the following
algorithms:
0 Reserved.
1 Default (loss) algorithm.
4.8. Reduction-Percentage AVP
The Reduction-Percentage AVP (AVP code TBD8) is type of Unsigned32 The Reduction-Percentage AVP (AVP code TBD8) is type of 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 have sent. requested to reduce, compared to what it otherwise would have sent.
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 interpreted as 100. The hundred (100). Values greater than 100 are interpreted as 100. The
value of 100 means that no traffic is expected, i.e. the sender of value of 100 means that no traffic is expected, i.e. the sender of
the information is under a severe load and ceases to process any new the information is under a severe load and ceases to process any new
messages. The value of 0 means that the sender of the information is messages. The value of 0 means that the sender of the information is
in a stable state and has no requests to the other endpoint to apply in a stable state and has no requests to the other endpoint to apply
any traffic abatement. any traffic abatement.
[OpenIssue: We should consider an algorithm independent way to end an [Open Issue: We should consider an algorithm independent way to end
overload condition. Perhaps setting the validitytime to zero? an overload condition. Perhaps setting the validitytime to zero?
Counter comment; since the abatement is based on a specific Counter comment; since the abatement is based on a specific
algorithm, it is natural to indicate that from the abatement algorithm, it is natural to indicate that from the abatement
algorithm point of view status quo has been reached.] algorithm point of view status quo has been reached.]
Since a Reduction-Percentage of 100% prevents the reporting node from If an overload control endpoint comes out of the 100 percent traffic
explicitly ending the overload condition, such a condition can only reduction as a result of the overload report timing out, the
end due to a report timeout. When an overload control endpoint comes following concerns are RECOMMENDED to be applied. The endpoint
out of the 100 percent traffic reduction as a result, the following sending the traffic should be conservative and, for example, first
concerns are RECOMMENDED to be applied. The endpoint sending the send few "probe" messages to learn the overload condition of the
traffic should be conservative and, for example, first send few other endpoint before converging to any traffic amount/rate decided
"probe" messages to learn the overload condition of the other by the sender. Similar concerns actually apply in all cases when the
endpoint before converging to any traffic level decided by the
sender. Similar concerns actually apply in all cases when the
overload report times out unless the previous overload report stated overload report times out unless the previous overload report stated
0 percent reduction. 0 percent reduction.
4.9. Attribute Value Pair flag rules [Open Issue: It is still open whether we need an AVP to indicate the
exact used traffic abatement algorithm. Currently it assumed that
the reacting node is able to figure out what to do based on the
Reducttion-Percentage AVP and possible other embedded information
inside the OC-OLR AVP.]
4.7. 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-Feature-Vector TBD1 x.x Unsigned64 | | V | |OC-Feature-Vector TBD1 x.x Unsigned64 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-OLR TBD2 x.x Grouped | | V | |OC-OLR TBD2 x.x Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|TimeStamp TBD3 x.x Time | | V | |TimeStamp TBD3 x.x Time | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|ValidityPeriod TBD4 x.x Unsigned32 | | V | |ValidityPeriod TBD4 x.x Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|ReportType TBD5 x.x Enumerated | | V | |ReportType TBD5 x.x Enumerated | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Algorithm TBD6 x.x Grouped | | V |
+--------------------------------------------------+----+----+
|Algorithm-ID TBD7 x.x Enumerated | | V |
+--------------------------------------------------+----+----+
|Reduction | | | |Reduction | | |
| -Percentage TBD8 x.x Unsigned32 | | V | | -Percentage TBD8 x.x Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
5. Overload Control Operation 5. Overload Control Operation
5.1. Overload Control Endpoints 5.1. Overload Control Endpoints
The overload control solution can be considered as an overlay on top The overload control solution can be considered as an overlay on top
of an arbitrary Diameter network. An overload control "association" of an arbitrary Diameter network. The overload control information
exists between two Diameter nodes that exchanging overload control is exchanged over on a "DOIC association" between two communicatin
information. These nodes are called "overload control endpoints". endpoints. The endpoints, namely the "reacting node" and the
These endpoints, namely the "reacting node" and the "reporting node" "reporting node" do not need to be adjacent Diameter peer nodes, nor
do not need to be adjacent Diameter peer nodes, nor do they need to they need to be the end-to-end Diameter nodes in a typical "client-
be the end-to-end Diameter nodes in a typical "client-server" server" deployment with multiple intermediate Diameter agent nodes in
deployment with multiple intermediate Diameter agent nodes in
between. The overload control endpoint are the two Diameter nodes between. The overload control endpoint are the two Diameter nodes
that decide to exchange overload control information between each that decide to exchange overload control information between each
other. How the endpoints are determined is specific to a deployment, other. How the endpoints are determined is specific to a deployment,
a Diameter node role in that deployment and local configuration. a Diameter node role in that deployment and local configuration.
[Editor's note: a picture illustrating the endpoint concept would The following diagrams illustrate the concept of Diameter Overload
be useful.] End-Points and how they differ from the standard [RFC6733] defined
client, server and agent Diameter nodes. The following is the key to
the elements in the diagrams:
C Diameter client as defined in [RFC6733].
S Diameter server as defined in [RFC6733].
A Diameter agent, in either a relay or proxy mode, as defined in
[RFC6733].
DEP Diameter Overload End-Point as defined in this document. In the
following figures a DEP may terminate two different DOIC
associations being a reporter and reactor at the same time.
Diameter Session A Diameter session as defined in [RFC6733].
DOIC Association A DOIC association exists between two Diameter
Overload End-Points. One of the end-points is the overload
reporter and the other is the overload reactor.
Figure 2 illustrates the most basic configuration where a client is
connected directly to a server. In this case, the session and
association are both between the client and server.
+-----+ +-----+
| C | | S |
+-----+ +-----+
| DEP | | DEP |
+--+--+ +--+--+
| |
| |
|{Diameter Session}|
| |
|{DOIC Association}|
| |
Figure 2: Basic DOIC deployment
In Figure 3 there is an agent that is not participating directly in
the exchange of overload reports. As a result, the DOIC association
is still between the client and the server.
+-----+ +-----+ +-----+
| C | | A | | S |
+-----+ +--+--+ +-----+
| DEP | | | DEP |
+--+--+ | +--+--+
| | |
| | |
|----------{Diameter Session}---------|
| | |
|----------{DOIC Association}---------|
| | |
Figure 3: DOIC deployment with non participating agent
Figure 4 illustrates the case where the client does not support
Diameter overload. In this case, the DOIC association is between the
agent and the server. The agent handles the role of the reactor for
overload reports generated by the server.
+-----+ +-----+ +-----+
| C | | A | | S |
+--+--+ +-----+ +-----+
| | DEP | | DEP |
| +--+--+ +--+--+
| | |
| | |
|----------{Diameter Session}---------|
| | |
| |{DOIC Association}|
| | |
Figure 4: DOIC deployment with non-DOIC client and DOIC enabled agent
In Figure 5 there is a DOIC association between the client and the
agent and a second DOIC association between the agent and the server.
One use case requiring this configuration is when the agent is
serving as a SFE/SFIM for a set of servers.
+-----+ +-----+ +-----+
| C | | A | | S |
+-----+ +-----+ +-----+
| DEP | | DEP | | DEP |
+--+--+ +--+--+ +--+--+
| | |
| | |
|----------{Diameter Session}---------|
| | |
|{DOIC Association}|{DOIC Association}|
| | |
Figure 5: A deployment where all nodes support DOIC
Figure 6 illustrates a deployment where some clients support Diameter
overload control and some do not. In this case the agent must
support Diameter overload control for the non supporting client. It
might also need to have a DOIC association with the server, as shown
here, to handle overload for a server farm and/or for managing Realm
overload.
+-----+ +-----+ +-----+ +-----+
| C1 | | C2 | | A | | S |
+-----+ +--+--+ +-----+ +-----+
| DEP | | | DEP | | DEP |
+--+--+ | +--+--+ +--+--+
| | | |
| | | |
|-------------------{Diameter Session}-------------------|
| | | |
| |--------{Diameter Session}-----------|
| | | |
|---------{DOIC Association}----------|{DOIC Association}|
| | | |
Figure 6: A deployment with DOIC and non-DOIC supporting clients
Figure 7 illustrates a deployment where some agents support Diameter
overload control and others do not.
+-----+ +-----+ +-----+ +-----+
| C | | A | | A | | S |
+-----+ +--+--+ +-----+ +-----+
| DEP | | | DEP | | DEP |
+--+--+ | +--+--+ +--+--+
| | | |
| | | |
|-------------------{Diameter Session}-------------------|
| | | |
| | | |
|---------{DOIC Association}----------|{DOIC Association}|
| | | |
Figure 7: A deployment with DOIC and non-DOIC supporting agents
5.2. Piggybacking Principle 5.2. Piggybacking Principle
The overload control solution defined AVPs are essentially The overload control solution defined AVPs are essentially
piggybacked on top of existing application message exchanges. This piggybacked on top of existing application message exchanges. This
is made possible by adding overload control top level AVPs, the OC- is made possible by adding overload control top level AVPs, the OC-
OLR AVP and the OC-Feature-Vector AVP into existing commands (this OLR AVP and the OC-Feature-Vector AVP into existing commands (this
has an assumption that the application CCF allows adding new AVPs has an assumption that the application CCF allows adding new AVPs
into the Diameter messages. into the Diameter messages.
In a case of newly defined Diameter applications, it is RECOMMENDED In a case of newly defined Diameter applications, it is RECOMMENDED
to add and define how overload control mechanisms works on that to add and defined how overload control mechanisms works on that
application. Using OC-Feature-Vector and OC-OLR AVPs is optional, application. using OC-Feature-Vector and OC-OLR AVPs in a non-
and is intended only existing applications. mandatory manner is intended only existing applications.
[OpenIssue: The guidance in the previous paragraph depends on the
outcome of the open issue mentioned at the definition of OC-Feature-
Vector.]
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 overload control endpoint role is determined and client roles. The endpoint role is determined based on the sent
based on the sent message type: whether the message is a request for message type: whether the message is a request (i.e. sent by a
overload information (i.e. sent by a "reacting node") or an overload "reacting node") or an answer (i.e. send by a "reporting node").
report (i.e. send by a "reporting node"). Therefore, in a typical Therefore, in a typical "client-server" deployment, the "client" MAY
"client-server" deployment, the "client" MAY report its overload report its overload condition to the "server" for any server
condition to the "server" for any server initiated message exchange. initiated message exchange. An example of such is the server
An example of such is the server requesting a re-authentication from requesting a re-authentication from a client.
a client.
5.3. Capability Negotiation 5.3. Capability Announcement
Since the overload control solution relies on the piggybacking Since the overload control solution relies on the piggybacking
principle for the overload reporting and the overload control principle for the overload reporting and the overload control
endpoint are likely not adjacent peers, finding out whether the other endpoint are likely not adjacent peers, finding out whether the other
endpoint supports the overload control or what is the common traffic endpoint supports the overload control or what is the common traffic
abatement algorithm to apply for the traffic. The approach defined abatement algorithm to apply for the traffic. The approach defined
in this specification for the end-to-end capability negotiation or in this specification for the end-to-end capability capability
rather the capability announcement relies on the exchange of the OC- announcement relies on the exchange of the OC-Feature-Vector between
Feature-Vector and OC-OLR AVPs between the endpoints. The the endpoints. The feature announcement solution also works when
negotiation solution also works when carried out on existing carried out on existing applications. For the newly defined
applications. For the newly defines application the negotiation can application the negotiation can be more exact based on the
be more exact based on the application specification. The negotiated application specification. The announced set of capabilities MUST
set of capabilities MUST NOT change during the life time of the NOT change during the life time of the Diameter session (or
Diameter session (or transaction in a case of non-session maintaining transaction in a case of non-session maintaining applications).
applications).
[OpenIssue: Some of the guidance in the previous paragraph depends on
the outcome of the open issue mentioned at the definition of OC-
Feature-Vector.]
[OpenIssue: We need to think more about the general flow for
capabilities negotiation. Call flows would be helpful here. A
counter comment: the text in Section 4.1 should be rather clear now
regarding the capability negotiation.]
5.3.1. Request Message Initiator Endpoint Considerations 5.3.1. Request Message Initiator Endpoint Considerations
The basic principle is that the request message initiating endpoint The basic principle is that the request message initiating endpoint
(i.e. the "reacting node") announces its support for the overload (i.e. the "reacting node") announces its support for the overload
control mechanism by including in a Diameter request message the OC- control mechanism by including in the request message the OC-Feature-
Feature-Vector AVP with those capability flag bits set that it Vector AVP with those capability flag bits set that it supports and
supports and is willing to use for this Diameter session (or is willing to use for this Diameter session (or transaction in a case
transaction in a case of a non-session state maintaining of a non-session state maintaining applications). In a case of
applications). In a case of session maintaining applications the session maintaining applications the request message initiating
request message initiating endpoint does not need to do the endpoint does not need to do the capability announcement more than
capability announcement more than once for the lifetime of the once for the lifetime of the Diameter session. In a case of non-
Diameter session. In a case of non-session maintaining applications, session maintaining applications, it is RECOMMENDED that the request
it is RECOMMENDED that the request message initiating endpoint message initiating endpoint includes the capability announcement into
includes the capability announcement into every request regardless it every request regardless it has had prior message exchanges with the
has had prior message exchanges with the give remote endpoint. give remote endpoint.
[OpenIssue: We need to think about the lifetime of a capabilities [OpenIssue: We need to think about the lifetime of a capabilities
declaration. It's probably not the same as for a session. We have declaration. It's probably not the same as for a session. We have
had proposals that the feature vector needs to go into every request had proposals that the feature vector needs to go into every request
sent by an OC node. For peer to peer cases, this can be associated sent by an OC node. For peer to peer cases, this can be associated
with connection lifetime, but it's more complex for non-adjacent OC with connection lifetime, but it's more complex for non-adjacent OC
support.] support.]
If the OC-Feature-Vector AVP does not have enough information about
the supported feature or the traffic abatement algorithm, then the
request message initiating endpoint MUST also include the OC-OLR AVP
with an appropriate content in it (such as a rate based abatement
algorithm would include the desired rate information AVPs inside the
OC-OLR AVP). See the discussion in Section 4.1 and in Section 4.6.
Once the endpoint that initiated the request message receives an Once the endpoint that initiated the request message receives an
answer message from the remote endpoint, it can detect from the answer message from the remote endpoint, it can detect from the
received answer message whether the remote endpoint supports the received answer message whether the remote endpoint supports the
overload control solution and in a case it does, what features are overload control solution and in a case it does, what features are
supported. The support for the overload control solution is based on supported. The support for the overload control solution is based on
the presence of the OC-Feature-Vector and/or OC-OLR AVPs in the the presence of the OC-Feature-Vector AVP in the Diameter answer for
Diameter answer for existing application. For the newly defined existing application. For the newly defined applications the support
applications the support for the overload control is already part of for the overload control MAY already be part of the application
the application specification. Based on capability knowledge the specification. Based on capability knowledge the request message
request message initiating endpoint can select the preferred common initiating endpoint can select the preferred common traffic abatement
traffic abatement algorithm and act accordingly for the subsequent algorithm and act accordingly for the subsequent message exchanges.
message exchanges.
5.3.2. Answer Message Initiating Endpoint Considerations 5.3.2. Answer Message Initiating Endpoint Considerations
When a remote endpoint (i.e. a "reporting node") receives a request When a remote endpoint (i.e. a "reporting node") receives a request
message in can detect whether the request message initiating endpoint message in can detect whether the request message initiating endpoint
has support for the overload control solution based on the presence has support for the overload control solution based on the presence
of the OC-Feature-Vector AVP and possibly the OC-OLR AVP. For the of the OC-Feature-Vector AVP. For the newly defined applications the
newly defined applications the overload control solution support can overload control solution support can be part of the application
be part of the application specification. Based on the content of specification. Based on the content of the OC-Feature-Vector AVP the
the OC-Feature-Vector AVP and optionally the contents of the OC-OLR request message receiving endpoint knows what overload control
AVP, the request message receiving endpoint knows what overload functionality the other endpoint supports and then act accordingly
control functionality the other endpoint supports and then act for the subsequent answer messages it initiates. It is RECOMMENDED
accordingly for the subsequent answer messages it initiates. It is that the answer message initiating endpoint selects one common
RECOMMENDED that the answer message initiating endpoint selects one traffic abatement algorithm even if it would support multiple. The
common traffic abatement algorithm even if it would support multiple. answer message initiating endpoint MUST NOT include any overload
The answer message initiating endpoint MUST NOT include any overload
control solution defined AVPs into its answer messages if the request control solution defined AVPs into its answer messages if the request
message initiating endpoint has not indicated support at the message initiating endpoint has not indicated support at the
beginning of the the created session (or transaction in a case of beginning of the the created session (or transaction in a case of
non-session state maintaining applications). non-session state maintaining applications).
5.4. Protocol Extensibility 5.4. Protocol Extensibility
The overload control solution can be extended, e.g. with new traffic The overload control solution can be extended, e.g. with new traffic
abatement algorithms or new functionality. The new features and abatement algorithms or new functionality. The new features and
algorithms MUST be registered with the IANA and for the possible use algorithms MUST be registered with the IANA and for the ppossible use
with the OC-Feature-Vector for announcing the support for the new with the OC-Feature-Vector for announcing the support for the new
features (see Section 7 for the required procedures). features (see Section 7 for the required procedures).
It should be noted that [RFC6733] defined Grouped AVP extension It should be noted that [RFC6733] defined Grouped AVP extension
mechanisms also apply. This allows, for example, defining a new mechanisms also apply. This allows, for example, defining a new
feature that is mandatory to understand even when piggybacked on an feature that is mandatory to understand even when piggybacked on an
existing applications. More specifically, the sub-AVPs inside the existing applications. More specifically, the sub-AVPs inside the
OC-OLR AVP MAY have the M-bit set. However, when overload control OC-OLR AVP MAY have the M-bit set. However, when overload control
AVPs are piggybacked on top of an existing applications, setting AVPs are piggybacked on top of an existing applications, setting
M-bit in sub-AVPs is NOT RECOMMENDED. M-bit in sub-AVPs is NOT RECOMMENDED.
skipping to change at page 23, line 38 skipping to change at page 25, line 44
5.5.1. Sender Endpoint Considerations 5.5.1. Sender Endpoint Considerations
5.5.2. Receiver Endpoint Considerations 5.5.2. Receiver Endpoint Considerations
[OpenIssue: did we now agree that e.g. a server can refrain sending [OpenIssue: did we now agree that e.g. a server can refrain sending
OLR in answers based on some magical algorithm? (Note: We seem to OLR in answers based on some magical algorithm? (Note: We seem to
have consensus that a server MAY repeat OLRs in subsequent messages, have consensus that a server MAY repeat OLRs in subsequent messages,
but is not required to do so, based on local policy.)] but is not required to do so, based on local policy.)]
[OpenIssue: We need to define some rules about throttling at an
agent. In particular, that the agent needs to send errors back
downstream if it drops requests, and propose a specific error code
for this purpose.]
6. Transport Considerations 6. Transport Considerations
In order to reduce overload control introduced additional AVP and In order to reduce overload control introduced additional AVP and
message processing it might be desirable/beneficial to signal whether message processing it might be desirable/beneficial to signal whether
the Diameter command carries overload control information that should the Diameter command carries overload control information that should
be of interest of an overload aware Diameter node. be of interest of an overload aware Diameter node.
Should such indication be include is not part of this specification. Should such indication be include is not part of this specification.
It has not either been concluded at what layer such possible It has not either been concluded at what layer such possible
indication should be. Obvious candidates include transport layer indication should be. Obvious candidates include transport layer
skipping to change at page 24, line 29 skipping to change at page 26, line 32
Authorization, and Accounting (AAA) Parameters' registry. Authorization, and Accounting (AAA) Parameters' registry.
Section 4.1 defines a new "Overload Control Feature Vector" registry Section 4.1 defines a new "Overload Control Feature Vector" registry
including the initial assignments. New values can be added into the including the initial assignments. New values can be added into the
registry using the Specification Required policy [RFC5226]. registry using the Specification Required policy [RFC5226].
Section 4.5 defines a new "Overload Report Type" registry with its Section 4.5 defines a new "Overload Report Type" registry with its
initial assignments. New types can be added using the Specification initial assignments. New types can be added using the Specification
Required policy [RFC5226]. Required policy [RFC5226].
Section 4.7 defines a new "Overload Control Algorithm" registry with
its initial assignments. New types can be added using the
Specification Required policy [RFC5226].
8. Security Considerations 8. Security Considerations
This mechanism gives Diameter nodes the ability to request that This mechanism gives Diameter nodes the ability to request that
downstream nodes send fewer Diameter requests. Nodes do this by downstream nodes send fewer Diameter requests. Nodes do this by
exchanging overload reports that directly affect this reduction. exchanging overload reports that directly affect this reduction.
This exchange is potentially subject to multiple methods of attack, This exchange is potentially subject to multiple methods of attack,
and has the potential to be used as a Denial-of-Service (DoS) attack and has the potential to be used as a Denial-of-Service (DoS) attack
vector. vector.
Overload reports may contain information about the topology and Overload reports may contain information about the topology and
current status of a Diameter network. This information is current status of a Diameter network. This information is
potentially sensitive. Network operators may wish to control potentially sensitive. Network operators may wish to control
disclosure of overload reports to unauthorized parties to avoid its disclosure of overload reports to unauthorized parties to avoid its
use for competitive intelligence or to target attacks. use for competitive intelligence or to target attacks.
Diameter does not currently 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.
8.1. Potential Threat Modes 8.1. 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.
(e.g. TCP or SCTP) connection, or the messages may traverse one or TCP or SCTP) connection, or the messages may traverse one or more
more intermediaries, known as Diameter Agents. Diameter nodes use intermediaries, known as Diameter Agents. Diameter nodes use TLS,
TLS, DTLS, or IPSec to authenticate peers, and to provide DTLS, or IPSec to authenticate peers, and to provide confidentiality
confidentiality and integrity protection of traffic between peers. and integrity protection of traffic between peers. Nodes can make
Nodes can make authorization decisions based on the peer identities authorization decisions based on the peer identities authenticated at
authenticated at the transport layer. the transport layer.
When agents are involved, this presents an effectively hop-by-hop When agents are involved, this presents an effectively hop-by-hop
trust model. That is, a Diameter client or server can authorize an trust model. That is, a Diameter client or server can authorize an
agent for certain actions, but it must trust that agent to make agent for certain actions, but it must trust that agent to make
appropriate authorization decisions about its peers, and so on. appropriate authorization decisions about its peers, and so on.
Since confidentiality and integrity protection occurs at the Since confidentiality and integrity protection occurs at the
transport layer, agents can read, and perhaps modify, any part of a transport layer. Agents can read, and perhaps modify, any part of a
Diameter message, including an overload report. Diameter message, including an overload report.
There are several ways an attacker might attempt to exploit the There are several ways an attacker might attempt to exploit the
overload control mechanism. An unauthorized third party might inject overload control mechanism. An unauthorized third party might inject
an overload report into the network. If this third party is upstream an overload report into the network. If this third party is upstream
of an agent, and that agent fails to apply proper authorization of an agent, and that agent fails to apply proper authorization
policies, downstream nodes may mistakenly trust the report. This policies, downstream nodes may mistakenly trust the report. This
attack is at least partially mitigated by the assumption that nodes attack is at least partially mitigated by the assumption that nodes
include overload reports in Diameter answers but not in requests. include overload reports in Diameter answers but not in requests.
This requires an attacker to have knowledge of the original request This requires an attacker to have knowledge of the original request
skipping to change at page 29, line 33 skipping to change at page 31, line 36
The base solution for the overload control does not cover all The base solution for the overload control does not cover all
possible use cases. A number of solution aspects were intentionally possible use cases. A number of solution aspects were intentionally
left for future specification and protocol work. left for future specification and protocol work.
A.1. Additional traffic abatement algorithms A.1. Additional traffic abatement algorithms
This specification describes only means for a simple loss based This specification describes only means for a simple loss based
algorithm. Future algorithms can be added using the designed algorithm. Future algorithms can be added using the designed
solution extension mechanism. The new algorithms need to be solution extension mechanism. The new algorithms need to be
registered with IANA. See Sections 4.1, 4.7 and 7 for the required registered with IANA. See Sections 4.1 and 7 for the required IANA
IANA steps. steps.
A.2. Agent Overload A.2. Agent Overload
This specification focuses on Diameter end-point (server or client) This specification focuses on Diameter end-point (server or client)
overload. A separate extension will be required to outline the overload. A separate extension will be required to outline the
handling the case of agent overload. handling the case of agent overload.
A.3. DIAMETER_TOO_BUSY clarifications A.3. DIAMETER_TOO_BUSY clarifications
The current [RFC6733] behaviour in a case of DIAMETER_TOO_BUSY is The current [RFC6733] behaviour in a case of DIAMETER_TOO_BUSY is
somewhat underspecified. For example, there is no information how somewhat underspecified. For example, there is no information how
long the specific Diameter node is willing to be unavailable. A long the specific Diameter node is willing to be unavailable. A
specification updating [RFC6733] should clarify the handling of specification updating [RFC6733] should clarify the handling of
DIAMETER_TOO_BUSY from the error answer initiating Diameter node DIAMETER_TOO_BUSY from the error answer initiating Diameter node
point of view and from the original request initiating Diameter node point of view and from the original request initiating Diameter node
point of view. Further, the inclusion of possible additional point of view. Further, the inclusion of possible additional
information providing APVs should be discussed and possible be information providing APVs should be discussed and possible be
recommended to be used. recommended to be used.
A.4. Load Appendix B. Conformance to Requirements
This specification defines the mechanism for a Diameter end-point to The following section analyses, which Diameter Overload Control
request a reduction in traffic. The full solution envisioned by the requirements [I-D.ietf-dime-overload-reqs] are met by this
Diameter overload requirements also included a mechanism to specification.
communicate load that a Diameter node is able to handle. This
capability is expected to help to decrease the oscillation of
overload events. This load capability has been left for follow on
work.
Appendix B. Examples Key:
B.1. 3GPP S6a interface overload indication S - Supported
P - Partial
N - Not supported
+------+----+-------------------------------------------------------+
| Rqmt | S/ | Notes |
| # | P/ | |
| | N | |
+------+----+-------------------------------------------------------+
| REQ | P | The DOIC solution only addresses overload |
| 1 | | information. Load information is left as future |
| | | work. In addition, the DOIC solution does not |
| | | address agent overload scenarios. |
| | | - |
| REQ | P | The DOIC solution supports overload reports that |
| 2 | | implicitly indicate the application impacted by the |
| | | report. The DOIC solution does not support reporting |
| | | load information. The DOIC solution is thought to |
| | | support graceful behavior. Allowing an application |
| | | specific capabilities negotiation mechanism violates |
| | | application-independence. Suggested different |
| | | wording: The DOIC solution supports overload reports |
| | | that are applicable to any Diameter application. The |
| | | DOIC solution does not support reporting load |
| | | information. The DOIC solution allows to support |
| | | graceful behavior; this will be enhanced when the |
| | | Load information will be defined. Comment: Can we |
| | | removed the words "is thought"? |
| | | - |
| REQ | S | The DOIC solution is thought to address this |
| 3 | | requirement. Comment: Can we removed the words "is |
| | | thought"? |
| | | - |
| REQ | P | The DOIC solution does allow for both both a Diameter |
| 4 | | server and a Diameter client to send overload |
| | | reports. The DOIC solution only addresses Diameter |
| | | end-point (server and client) overload. Agent |
| | | overload is being addressed in a separate draft. |
| | | - |
| REQ | S | The DOIC solution does not depend on how the |
| 5 | | end-points are discovered. Comment: it might be |
| | | worth working through at least one use case showing |
| | | DNS based dynamic peer discovery to make sure we |
| | | haven't missed anything. |
| | | - |
| REQ | ? | Need to update text as some configuation is required. |
| 6 | | Need to determin if the current discussion on |
| | | overload application id increases the amount of |
| | | configuration which would change this to a N. |
| | | - |
| REQ | S | The DOIC solution supports the loss algorithm, which |
| 7 | | is expected to address this requirement. There is |
| | | concern about the ability to address oscillations. |
| | | Wording is included for how a reacting node starts to |
| | | increase traffic after an overload report expires to |
| | | address this concern. Suggested different wording: |
| | | The DOIC solution supports a baseline mechanism |
| | | relying on traffic reduction percentage that is a |
| | | loss algorithm, which allows to address this |
| | | requirement. Oscillations are avoided or quite |
| | | minimized by sending successive OLR reports with the |
| | | values to converge to the optimal traffic or to |
| | | smoothly come back to normal traffic conditions when |
| | | overload decreases and ends. |
| | | - |
| REQ | ? | The DOIC solution supports a timestamp which is meant |
| 8 | | to serve as a report version indication to address |
| | | this requirement. Comment: The use of the timestamp |
| | | is under discussion. |
| | | - |
| REQ | ? | The DOIC solution uses a piggybacking strategy for |
| 9 | | carrying overload reports, which scales lineraly with |
| | | the amount of traffic. As such, the first part of |
| | | the requirement is addressed. The DOIC solution does |
| | | not support a mechanism for sending overload reports |
| | | over a quiescent transport connections or, more |
| | | generally, to Diameter nodes that are not producing |
| | | traffic. Suggested different wording: The DOIC |
| | | solution uses a piggybacking strategy for carrying |
| | | overload reports. As such, the first part of the |
| | | requirement is addressed. For a connection that has |
| | | become quiescent due to OLRs with a 100% traffic |
| | | reduction, the validity timer allows to handle this |
| | | case. Other cases of quiescent connections are |
| | | outside the scope of Diameter overload (e.g. their |
| | | handling may be done through the watch dog of the |
| | | Diameter base protocol). |
| | | - |
| REQ | S | The DOIC solution supports two methods for managing |
| 10 | | the length of an overload condition. First, all |
| | | overload reports must contain a duration indication, |
| | | after which the node reacting to the report can |
| | | consider the overload condition as ended. Secondly, |
| | | the solution supports the method for the node |
| | | originating the overload report to explicitly |
| | | communicate that the condition has ended. This |
| | | latter mechanism depends on traffic to be sent from |
| | | the reacting node and, as such, can not be depended |
| | | upon in all circumstances. |
| | | - |
| REQ | ? | The DOIC solution works well for small network |
| 11 | | configurations and for network configurations with a |
| | | single Diameter agent hop. More analysis is required |
| | | to determine how well the DOIC solution handles very |
| | | large Diameter network with partitioned or segmented |
| | | server farms requiring multiple hops through Diameter |
| | | agents. |
| | | - |
| REQ | P | The DOIC solution focuses on Diameter end-point |
| 12 | | overload and meets this requirement for those |
| | | Diameter nodes. The DOIC solution does not address |
| | | Diameter Agent overload and does not meet this |
| | | requirement for those Diameter nodes. |
| | | - |
| REQ | ? | The DOIC solution requires including of the overload |
| 13 | | report in all answer messages in some situations. It |
| | | is not agreed, however, that this constitutes |
| | | substantial work. This can also be mitigated by the |
| | | sender of the overload report keeping state to record |
| | | who has received overload reports. It is left to |
| | | implementation decisions as to which approach is |
| | | taken -- send in all messages or send once with a |
| | | record of who has received the report. Another way |
| | | is to let the request sender (reacting node) insert |
| | | information in the request to say whether a |
| | | throttling is actually performed. The reporting node |
| | | then can base its decision on information received in |
| | | the request; no need for keeping state to record who |
| | | has received overload reports. The DOIC solution |
| | | also requires capabilities negotiation in every |
| | | request and response message, which increases the |
| | | baseline work required for any node supporting the |
| | | DOIC solution. Suggested additional text: It does |
| | | not, however, require that the information be |
| | | recalculated or updated with each message. The |
| | | update frequency is up to the implementation, and |
| | | each implementation can make decisions on balancing |
| | | the update of overload information along with its |
| | | other priorities. It is expected that using a |
| | | periodically updated OLR report added to all messages |
| | | sent to overload control endpoints will not add |
| | | substantial additional work. Piggyback base |
| | | transport also does not require composition, sending, |
| | | or parsing of new Diameter messages for the purpose |
| | | of conveying overload control information. There is |
| | | still discussion on the substantial additional work |
| | | due to have OLR in each answer message. |
| | | - |
| REQ | S | The DOIC solution uses the piggybacking method to |
| 14 | | deliver overload report, which scales lineraly with |
| | | the amount of traffic. This allows for immediate |
| | | feedback to any node generating traffic toward |
| | | another overloaded node. |
| | | - |
| REQ | S | The DOIC solution does not interfere with transport |
| 15 | | protocols. |
| | | - |
| REQ | ? | The DOIC solution allows for a mixed network of |
| 16 | | supporting and non supporting Diameter end-points. |
| | | It isn't clear how realm overload is handled in a |
| | | network with agents that do not support the DOIC |
| | | solution. Suggested additional wording: Evaluation |
| | | of Realm overload may require a DA supporting DOIC, |
| | | if the realm overload is not evaluated by the client. |
| | | Realm overload handling is still under discussion. |
| | | - |
| REQ | ? | Suggested wording: The DOIC solution addresses this |
| 17 | | requirement through the loss algorithm (DOIC baseline |
| | | mechanism) with the following possibilities. A DA |
| | | supporting DOIC can act on behalf of clients not |
| | | supporting DOIC. A reporting node is also aware of |
| | | the nodes not supporting the DOIC as there is no |
| | | advertisement of the DOIC support. It may then apply |
| | | a particular throttling of the requests coming from |
| | | these non supporting DOIC clients. |
| | | - |
| REQ | ? | It isn't clear yet that if this requirement is |
| 18 | | addressed. There has been a proposal to mark |
| | | messages that survived overload throttling as one |
| | | method for an overloaded node to address fairness but |
| | | this proposal is not yet part of the solution. It is |
| | | also possible that the overloaded node could use |
| | | state gathered as part of the capability |
| | | advertisement mechanism to know if the sending node |
| | | supports the DOIC solution and if not, to apply a |
| | | particular throttling of the requests coming from |
| | | these non supporting DOIC clients. |
| | | - |
| REQ | S | The DOIC solution supports the ability for the |
| 19 | | overloaded node and the reacting node to be in |
| | | different administrative domains. |
| | | - |
| REQ | ? | This mechanism is still under discussion. Comment 1: |
| 20 | | I think this is a "S". OLRs are clearly |
| | | distinguishable from any error code. The fact that |
| | | an agent would need to send errors if it throttles is |
| | | not an overload indication per se. It needs to do |
| | | that even without DoC. OTOH, if we apply some DOC |
| | | related fix to TOO_BUSY, we probably need a new code. |
| | | Comment 2: New AVPs conveys overload control |
| | | information, and this is transported on existing |
| | | answer messages, so distinguishable from Diameter |
| | | errors. |
| | | - |
| REQ | S | The inability for a node to send overload reports |
| 21 | | will result in equivalent through put to a network |
| | | that does not support the DOIC solution. |
| | | - |
| REQ | S | The DOIC solution gives this node generating the |
| 22 | | overload report the ability to control the amount of |
| | | throttling done by the reacting node using the |
| | | reduction percentage parameter in the overload |
| | | report. |
| | | - |
| REQ | ? | Initial text: The DOIC mechanism supports two |
| 23 | | abatement strategies by reacting nodes, routing to an |
| | | alternative node or dropping traffic. The routing to |
| | | an alternative node will be enhanced when the Load |
| | | extension is defined. Comment: This is a N. There's |
| | | no good way to determine which nodes are likely to |
| | | have sufficient capacity without some sort of load |
| | | metric for non-overloaded nodes. |
| | | - |
| REQ | N | The DOIC solution does not address delivering load |
| 24 | | information. |
| | | - |
| REQ | S | The DOIC solution contains some guideance. |
| 25 | | |
| | | - |
| REQ | S | The DOIC solution does not constrain a nodes ability |
| 26 | | to determine which requests are trottled. |
| | | - |
| REQ | ? | Initial text: The DOIC solution does add a new line |
| 27 | | of attack in the ability for a malicious entity to |
| | | insert overload reports that would reduce or |
| | | eliminate traffic. This, however, is no worse than |
| | | an attacker that would assert erroneous error |
| | | responses such as a TOO BUSY response. It is |
| | | recognized that the end-to-end security solution |
| | | currently being worked on by the DIME working group |
| | | is needed to close these types of vulurabilities. |
| | | Comment: Sending a malicious OLR with a type of |
| | | "realm" will have considerably more impact than a |
| | | TOO_BUSY. Personally, I don't think we can achieve |
| | | this requirement without either being hop-by-hop or |
| | | requiring e2e security. We probably need further |
| | | analysis of the security implications of the |
| | | capabilities negotiation as well. Suggested |
| | | additional verbage: An OLR only relates to the |
| | | traffic between a reporting node and a reacting node |
| | | and can effectively block the traffic from a client |
| | | which would be an important impact. Nevertheless |
| | | OLRs are regularly sent in all answers, so a |
| | | malicious OLR will have a short transient effect, as |
| | | quickly overridden by a new OLR. To have a |
| | | significant impact would require a continuous flow of |
| | | answers with malicious OLRs. There is the exception |
| | | of the OLR with a value of 100% reduction traffic |
| | | which has a higher vulnerability and the use of which |
| | | should be avoided when possible. In addition such |
| | | malicious OLRs must be in answers, which means the |
| | | capability to insert the malicious OLR in an existing |
| | | answer rather than to create an answer which is much |
| | | less easy than to create a request. To have a |
| | | network wide applicability would request to generate |
| | | malicious OLRs messages towards all reacting nodes. |
| | | It can be considered that the baseline mechanism |
| | | offer a relevant level of security. Further analysis |
| | | with a security expertise would be beneficial. |
| | | - |
| REQ | ? | See REQ 18 and REQ 27. Suggested additional verbage: |
| 28 | | Guidance may be provided for detection of non |
| | | compliant/abnormal use of OLRs, not only by endpoints |
| | | but also by intermediate DA that can be aware of |
| | | OLRs, an example being edge DAs with external |
| | | networks. Further analysis with a security expertise |
| | | would be beneficial. |
| | | - |
| REQ | ? | This requirement is not explicitly addressed by the |
| 29 | | DOIC solution. There is nothing in the DOIC solution |
| | | that would prevent the goals of this requirement from |
| | | being achieved. Non-adjacent DOIC without e2e |
| | | security could be an issue here. |
| | | - |
| REQ | ? | It isn't clear how a solution would interfere. |
| 30 | | Suggested wording: A node can have methods on how to |
| | | protect from overload from nodes non supporting DOIC. |
| | | The DOIC mechanism used with DOIC supporting nodes |
| | | will not interfere with the appliance of these |
| | | methods. There is the remark that the use of these |
| | | methods may impact the global overload of the node |
| | | and the evaluation of the traffic reduction that the |
| | | reporting node will send in OLRs. If a node has |
| | | methods to protect against denial of service attacks, |
| | | the use of DOIC will not interfere with them. A |
| | | denial of service attack concerning the DOIC itself |
| | | is addressed in REQ 27. |
| | | - |
| REQ | ? | Initial text with an S: The DOIC solution addresses |
| 31 | | node and realm directly. The application to which a |
| | | report applies is implicitly determined based on the |
| | | application level message carrying the report. Note |
| | | that there is no way with DOIC for an overloaded node |
| | | to communicate multiple nodes, realms or applications |
| | | in a single overload report. So the inverse of this |
| | | requirement is not supported. Comment: The inverse |
| | | is also not _required_ :-) But I think we are "P" |
| | | here, in that we don't support "node" per se. we do |
| | | support "server." "Node" includes agents. (I also |
| | | interpreted this to mean that each granularity needed |
| | | to be supported independently--that is, a potential |
| | | to say "all traffic to a realm" or "all traffic to a |
| | | host" independently of application.) |
| | | - |
| REQ | ? | Initial text with an S: The DOIC solution supports |
| 32 | | extensibility of both the information communicated |
| | | and in the definition of new overload abatement |
| | | algorithms. Comment 1: Recent discussions have made |
| | | this a ?. It can be changed to S/N/P once these |
| | | discussions come to a conclusion and new text is |
| | | added to the draft. Comment 2: Suggested wording - |
| | | The DOIC solution supports extensibility of both the |
| | | information communicated and in the definition of new |
| | | overload abatement algorithms or strategies. It |
| | | should be noted that, according to the applications |
| | | or to reacting node implementations, many algorithms |
| | | may be applied on top of the DOIC baseline solution |
| | | (without contradicting it), e.g. regarding which type |
| | | of request to throttle, prioritized messages |
| | | handling, mapping of the reduction % to an internal |
| | | algorithm (eg 1 message out of ten etc..) but such |
| | | algorithms are out of scope of DOIC. |
| | | - |
| REQ | ? | Initial text with P: The DOIC solution currently |
| 33 | | defines the loss algorithm as the default algorithm. |
| | | It does not specify it as mandatory to implement. |
| | | Comment 1: Then I think that's a "n". The MTI part |
| | | is the crux of the requirement. Comment 2: Suggested |
| | | wording: In the DOIC baseline solution, the reacting |
| | | node has to apply the received Reduction-Percentage, |
| | | and for achieving this, the reacting node can do |
| | | requests rerouting (when it is possible) or |
| | | drop/reject requests. This DOIC baseline solution is |
| | | a loss algorithm and DOIC should not require further |
| | | specification. The answer to REQ32 indicates the |
| | | possibility to add other algorithms on top of the |
| | | DOIC baseline solution. The DOIC solution currently |
| | | defines this loss algorithm as the default algorithm. |
| | | It is still under discussion to make it as mandatory |
| | | to implement. |
| | | - |
| REQ | P | The ability to communicate overload reports between |
| 34 | | supporting Diameter nodes does not require agents to |
| | | support the DOIC solution. Load information exchange |
| | | is not currently defined. |
+------+----+-------------------------------------------------------+
Table 1
Appendix C. Examples
C.1. 3GPP S6a interface overload indication
[TBD: Would cover S6a MME-HSS communication with several topology [TBD: Would cover S6a MME-HSS communication with several topology
choices (such as with or without DRA, and with "generic" agents).] choices (such as with or without DRA, and with "generic" agents).]
B.2. 3GPP PCC interfaces overload indication C.2. 3GPP PCC interfaces overload indication
[TBD: Would cover Gx/Rx and maybe S9..] [TBD: Would cover Gx/Rx and maybe S9..]
B.3. Mix of Destination-Realm routed requests and Destination-Host C.3. Mix of Destination-Realm routed requests and Destination-Host
reouted requests reouted requests
[TBD: Add example showing the use of Destination-Host type OLRs and [TBD: Add example showing the use of Destination-Host type OLRs and
Realm type OLRs.] Realm type OLRs.]
Authors' Addresses Authors' Addresses
Jouni Korhonen (editor) Jouni Korhonen (editor)
Broadcom Communications Broadcom Communications
Porkkalankatu 24 Porkkalankatu 24
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