draft-ietf-dime-ovli-03.txt   draft-ietf-dime-ovli-04.txt 
Diameter Maintenance and Extensions (DIME) J. Korhonen, Ed. Diameter Maintenance and Extensions (DIME) J. Korhonen, Ed.
Internet-Draft Broadcom Internet-Draft Broadcom
Intended status: Standards Track S. Donovan, Ed. Intended status: Standards Track S. Donovan, Ed.
Expires: January 4, 2015 B. Campbell Expires: April 30, 2015 B. Campbell
Oracle Oracle
L. Morand L. Morand
Orange Labs Orange Labs
July 3, 2014 October 27, 2014
Diameter Overload Indication Conveyance Diameter Overload Indication Conveyance
draft-ietf-dime-ovli-03.txt draft-ietf-dime-ovli-04.txt
Abstract Abstract
This specification documents a Diameter Overload Control (DOC) base This specification documents a Diameter Overload Control (DOC) base
solution and the dissemination of the overload report information. solution and the dissemination of the overload 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
skipping to change at page 1, line 41 skipping to change at page 1, line 41
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This Internet-Draft will expire on January 4, 2015. This Internet-Draft will expire on April 30, 2015.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Overload Control Endpoints (Non normative) . . . . . . . 6 3.1. Piggybacking Principle . . . . . . . . . . . . . . . . . 7
3.2. Piggybacking Principle (Non normative) . . . . . . . . . 10 3.2. DOIC Capability Announcement . . . . . . . . . . . . . . 8
3.3. DOIC Capability Announcement (Non normative) . . . . . . 11 3.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9
3.4. DOIC Overload Condition Reporting (Non normative) . . . . 12 3.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 10
3.5. DOIC Extensibility (Non normative) . . . . . . . . . . . 13 3.5. Simplified Example Architecture . . . . . . . . . . . . . 11
3.6. Simplified Example Architecture (Non normative) . . . . . 14 4. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12
3.7. Considerations for Applications Integrating the DOIC 4.1. Capability Announcement . . . . . . . . . . . . . . . . . 12
Solution (Non normative) . . . . . . . . . . . . . . . . 15 4.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 12
3.7.1. Application Classification (Non normative) . . . . . 15 4.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 12
3.7.2. Application Type Overload Implications (Non 4.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 13
normative) . . . . . . . . . . . . . . . . . . . . . 16 4.2. Overload Report Processing . . . . . . . . . . . . . . . 14
3.7.3. Request Transaction Classification (Non normative) . 18 4.2.1. Overload Control State . . . . . . . . . . . . . . . 14
3.7.4. Request Type Overload Implications (Non normative) . 18 4.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 18
4. Solution Procedures (Normative) . . . . . . . . . . . . . . . 20 4.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 18
4.1. Capability Announcement (Normative) . . . . . . . . . . . 20 4.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 20
4.1.1. Reacting Node Behavior (Normative) . . . . . . . . . 20 5. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 21
4.1.2. Reporting Node Behavior (Normative) . . . . . . . . 21 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1.3. Agent Behavior (Normative) . . . . . . . . . . . . . 22 5.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 22
4.2. Overload Report Processing (Normative) . . . . . . . . . 22 5.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 22
4.2.1. Overload Control State (Normative) . . . . . . . . . 22 6. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 23
4.2.2. Reacting Node Behavior (Normative) . . . . . . . . . 24 6.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 23
4.2.3. Reporting Node Behavior (Normative) . . . . . . . . 26 6.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 24
4.2.4. Agent Behavior (Normative) . . . . . . . . . . . . . 26 6.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 24
4.3. Protocol Extensibility (Normative) . . . . . . . . . . . 27 6.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 25
5. Loss Algorithm (Normative) . . . . . . . . . . . . . . . . . 28 6.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 25
5.1. Overview (Non normative) . . . . . . . . . . . . . . . . 28 6.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 25
5.2. Use of OC-Reduction-Percentage AVP . . . . . . . . . . . 29 6.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 26
5.3. Reporting Node Behavior (Normative) . . . . . . . . . . . 29 6.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 27
5.4. Reacting Node Behavior (Normative) . . . . . . . . . . . 29 7. Error Response Codes . . . . . . . . . . . . . . . . . . . . 27
6. Attribute Value Pairs (Normative) . . . . . . . . . . . . . . 30 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
6.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 31 8.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 31 8.2. New registries . . . . . . . . . . . . . . . . . . . . . 28
6.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 32 9. Security Considerations . . . . . . . . . . . . . . . . . . . 29
6.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 33 9.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 29
6.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 33 9.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 30
6.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 34 9.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 30
6.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 35 9.4. End-to End-Security Issues . . . . . . . . . . . . . . . 31
6.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 35 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32
7. Error Response Codes . . . . . . . . . . . . . . . . . . . . 36 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 11.1. Normative References . . . . . . . . . . . . . . . . . . 32
8.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 36 11.2. Informative References . . . . . . . . . . . . . . . . . 32
8.2. New registries . . . . . . . . . . . . . . . . . . . . . 37 Appendix A. Issues left for future specifications . . . . . . . 33
9. Security Considerations . . . . . . . . . . . . . . . . . . . 37 A.1. Additional traffic abatement algorithms . . . . . . . . . 33
9.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 37 A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 33
9.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 38 A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 33
9.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 39 Appendix B. Deployment Considerations . . . . . . . . . . . . . 34
9.4. End-to End-Security Issues . . . . . . . . . . . . . . . 39 Appendix C. Requirements Conformance Analysis . . . . . . . . . 34
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 40 Appendix D. Considerations for Applications Integrating the DOIC
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 40 Solution . . . . . . . . . . . . . . . . . . . . . . 34
11.1. Normative References . . . . . . . . . . . . . . . . . . 40 D.1. Application Classification . . . . . . . . . . . . . . . 34
11.2. Informative References . . . . . . . . . . . . . . . . . 41 D.2. Application Type Overload Implications . . . . . . . . . 35
Appendix A. Issues left for future specifications . . . . . . . 41 D.3. Request Transaction Classification . . . . . . . . . . . 36
A.1. Additional traffic abatement algorithms . . . . . . . . . 41 D.4. Request Type Overload Implications . . . . . . . . . . . 37
A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
A.3. DIAMETER_TOO_BUSY clarifications . . . . . . . . . . . . 42
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 42
B.1. Mix of Destination-Realm routed requests and Destination-
Host routed requests . . . . . . . . . . . . . . . . . . 42
Appendix C. Restructuring of -02 version of the draft . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 48
1. Introduction 1. Introduction
This specification defines a base solution for Diameter Overload This specification defines a base solution for Diameter Overload
Control (DOC), refered to as Diameter Overload Indication Conveyance Control (DOC), referred to as Diameter Overload Indication Conveyance
(DOIC). The requirements for the solution are described and (DOIC). The requirements for the solution are described and
discussed in the corresponding design requirements document discussed in the corresponding design requirements document
[RFC7068]. Note that the overload control solution defined in this [RFC7068]. Note that the overload control solution defined in this
specification does not address all the requirements listed in specification does not address all the requirements listed in
[RFC7068]. A number of overload control related features are left [RFC7068]. A number of overload control related features are left
for the future specifications. for the future specifications. See Appendix A for a list of
extensions that are currently being considered. See Appendix C for
an analysis of the conformance to the requirements specified in
[RFC7068].
The solution defined in this specification addresses Diameter The solution defined in this specification addresses Diameter
overload control between two endpoints (see Section 3.1). overload control between Diameter nodes that support the DOIC
Furthermore, the solution is designed to apply to existing and future solution. Furthermore, the solution which is designed to apply to
Diameter applications, requires no changes to the Diameter base existing and future Diameter applications, requires no changes to the
protocol [RFC6733] and is deployable in environments where some Diameter base protocol [RFC6733] and is deployable in environments
Diameter nodes do not implement the Diameter overload control where some Diameter nodes do not implement the Diameter overload
solution defined in this specification. control solution defined in this specification.
2. Terminology and Abbreviations 2. Terminology and Abbreviations
Abatement
Reaction to receipt of an overload report resulting in a reduction
in traffic sent to the reporting node. Abatement actions include
diversion and throttling.
Abatement Algorithm Abatement Algorithm
An algorithm requested by reporting nodes and used by reacting An mechanism requested by reporting nodes and used by reacting
nodes to reduce the amount of traffic sent during an occurrence of nodes to reduce the amount of traffic sent during an occurrence of
overload control. overload control.
Throttling Diversion
Throttling is the reduction of the number of requests sent to an Abatement of traffic sent to a reporting node by a reacting node
entity. Throttling can include a client dropping requests, or an in response to receipt of an overload report. The abatement is
agent rejecting requests with appropriate error responses. achieved by diverting traffic from the reporting node to another
Clients and agents can also choose to redirect throttled requests Diameter node that is able to process the request.
to some other entity or entities capable of handling them.
Editor's note: Propose to add a definition of Abatement to include Host-Routed Request
both throttling and diversion (redirecting of messages) actions.
Then to modify this definition to include just the rejecting of
requests and adding a definition of diversion.
Reporting Node The set of requests that a reacting node knows will be served by a
particular host, either due to the presence of a Destination-Host
AVP, or by some other local knowledge on the part of the reacting
node.
A Diameter node that generates an overload report. (This may or Overload Control State (OCS)
may not be the overloaded node.)
Reporting and reacting node internally maintained state describing
occurrences of overload control.
Overload Report (OLR)
Information sent by a reporting node indicating the start,
continuation or end of an occurrence of overload control.
Reacting Node Reacting Node
A Diameter node that consumes and acts upon a report. Note that A Diameter node that acts upon an overload report.
"act upon" does not necessarily mean the reacting node applies an
abatement algorithm; it might decide to delegate that downstream,
in which case it also becomes a "reporting node".
Overload Control State (OCS) Realm-Routed Request
State describing an occurrence of overload control maintained by The set of requests that a reacting node does not know the host
reporting and reacting nodes. that will service the request.
Overload Report (OLR) Reporting Node
A set of AVPs sent by a reporting node indicating the start or A Diameter node that generates an overload report. (This may or
continuation of an occurrence of overload control. may not be the overloaded node.)
Throttling
Throttling is the reduction of the number of requests sent to an
entity. Throttling can include a Diameter Client or Diameter
Server dropping requests, or a Diameter Agent rejecting requests
with appropriate error responses. In extreme cases reporting
nodes can also throttle requests when the requested reductions in
traffic does not sufficiently address the overload scenario.
3. Solution Overview 3. Solution Overview
The Diameter Overload Information Conveyance (DOIC) mechanism allows The Diameter Overload Information Conveyance (DOIC) solution allows
Diameter nodes to request other nodes to perform overload abatement Diameter nodes to request other nodes to perform overload abatement
actions, that is, actions to reduce the load offered to the actions, that is, actions to reduce the load offered to the
overloaded node or realm. overloaded node or realm.
A Diameter node that supports DOIC is known as a "DOIC endpoint". A Diameter node that supports DOIC is known as a "DOIC node". Any
Any Diameter node can act as a DOIC endpoint, including clients, Diameter node can act as a DOIC node, including clients, servers, and
servers, and agents. DOIC endpoints are further divided into agents. DOIC nodes are further divided into "Reporting Nodes" and
"Reporting Nodes" and "Reacting Nodes." A reporting node requests "Reacting Nodes." A reporting node requests overload abatement by
overload abatement by sending an Overload Report (OLR) to one or more sending an Overload Report (OLR) to one or more reacting nodes.
reacting nodes.
A reacting node consumes OLRs, and performs whatever actions are A reacting node acts upon OLRs, and performs whatever actions are
needed to fulfill the abatement requests included in the OLRs. A needed to fulfil the abatement requests included in the OLRs. A
Reporting node may report overload on its own behalf, or on behalf of Reporting node may report overload on its own behalf, or on behalf of
other (typically upstream) nodes. Likewise, a reacting node may other (typically upstream) nodes. Likewise, a reacting node may
perform overload abatement on its own behalf, or on behalf of other perform overload abatement on its own behalf, or on behalf of other
(typically downstream) nodes. (typically downstream) nodes.
A node's role as a DOIC endpoint is independent of its Diameter role. A node's role as a DOIC node is independent of its Diameter role.
For example, Diameter relay and proxy agents may act as DOIC For example, Diameter Relay and Proxy Agents may act as DOIC nodes,
endpoints, even though they are not endpoints in the Diameter sense. even though they are not endpoints in the Diameter sense. Since
Since Diameter enables bi-directional applications, where Diameter Diameter enables bi-directional applications, where Diameter Servers
servers can send requests towards Diameter clients, a given Diameter can send requests towards Diameter Clients, a given Diameter node can
node can simultaneously act as a reporting node and a reacting node. simultaneously act as a reporting node and a reacting node.
Likewise, a relay or proxy agent may act as a reacting node from the Likewise, a relay or proxy agent may act as a reacting node from the
perspective of upstream nodes, and a reporting node from the perspective of upstream nodes, and a reporting node from the
perspective of downstream nodes. perspective of downstream nodes.
DOIC endpoints do not generate new messages to carry DOIC related DOIC nodes do not generate new messages to carry DOIC related
information. Rather, they "piggyback" DOIC information over existing information. Rather, they "piggyback" DOIC information over existing
Diameter messages by inserting new AVPs into existing Diameter Diameter messages by inserting new AVPs into existing Diameter
requests and responses. Nodes indicate support for DOIC, and any requests and responses. Nodes indicate support for DOIC, and any
needed DOIC parameters by inserting an OC_Supported_Features AVP needed DOIC parameters by inserting an OC_Supported_Features AVP
(Section 6.2) into existing requests and responses. Reporting nodes (Section 6.2) into existing requests and responses. Reporting nodes
send OLRs by inserting OC-OLR AVPs (Section 6.3). send OLRs by inserting OC-OLR AVPs (Section 6.3).
A given OLR applies to the Diameter realm and application of the A given OLR applies to the Diameter realm and application of the
Diameter message that carries it. If a reporting node supports more Diameter message that carries it. If a reporting node supports more
than one realm and/or application, it reports independently for each than one realm and/or application, it reports independently for each
combination of realm and application. Similarly, OC-Feature-Vector combination of realm and application. Similarly, the OC-Supported-
AVPs apply to the realm and application of the enclosing message. Features AVP applies to the realm and application of the enclosing
This implies that a node may support DOIC for one application and/or message. This implies that a node may support DOIC for one
realm, but not another, and may indicate different DOIC parameters application and/or realm, but not another, and may indicate different
for each application and realm for which it supports DOIC. DOIC parameters for each application and realm for which it supports
DOIC.
Reacting nodes perform overload abatement according to an agreed-upon Reacting nodes perform overload abatement according to an agreed-upon
abatement algorithm. An abatement algorithm defines the meaning of abatement algorithm. An abatement algorithm defines the meaning of
the parameters of an OLR, and the procedures required for overload the parameters of an OLR and the procedures required for overload
abatement. This document specifies a single must-support algorithm, abatement. This document specifies a single must-support algorithm,
namely the "loss" algorithm Section 5). Future specifications may namely the "loss" algorithm (Section 5). Future specifications may
introduce new algorithms. introduce new algorithms.
Overload conditions may vary in scope. For example, a single Overload conditions may vary in scope. For example, a single
Diameter node may be overloaded, in which case reacting nodes may Diameter node may be overloaded, in which case reacting nodes may
reasonably attempt to send throttled requests to other destinations reasonably attempt to send requests to other destinations or via
or via other agents. On the other hand, an entire Diameter realm may other agents. On the other hand, an entire Diameter realm may be
be overloaded, in which case such attempts would do harm. DOIC OLRs overloaded, in which case such attempts would do harm. DOIC OLRs
have a concept of "report type" (Section 6.6), where the type defines have a concept of "report type" (Section 6.6), where the type defines
such behaviors. Report types are extensible. This document defines such behaviors. Report types are extensible. This document defines
report types for overload of a specific server, and for overload of report types for overload of a specific server, and for overload of
an entire realm. an entire realm.
A report of type host is sent to indicate the overload of a specific
server for the application-id indicated in the transaction. When
receiving an OLR of type host, a reacting node applies overload
abatement to what is referred to in this document as host-routed
requests. This is the set of requests that the reacting node knows
will be served by a particular host, either due to the presence of a
Destination-Host AVP, or by some other local knowledge on the part of
the reacting node. The reacting node applies overload abatement on
those host-routed requests which the reacting node knows will be
served by the server that matches the Origin-Host AVP of the received
message that contained the received OLR of type host.
A report type of realm is sent to indicate the overload of all
servers in a realm for the application-id. When receiving an OLR of
type realm, a reacting node applies overload abatement to what is
referred to in this document as realm-routed requests. This is the
set of requests that are not host-routed as defined in the previous
paragraph.
While a reporting node sends OLRs to "adjacent" reacting nodes, nodes While a reporting node sends OLRs to "adjacent" reacting nodes, nodes
that are "adjacent" for DOIC purposes may not be adjacent from a that are "adjacent" for DOIC purposes may not be adjacent from a
Diameter, or transport, perspective. For example, one or more Diameter, or transport, perspective. For example, one or more
Diameter agents that do not support DOIC may exist between a given Diameter agents that do not support DOIC may exist between a given
pair of reporting and reacting nodes, as long as those agents pass pair of reporting and reacting nodes, as long as those agents pass
unknown AVPs through unmolested. The report types described in this unknown AVPs through unchanged. The report types described in this
document can safely pass through non-supporting agents. This may not document can safely pass through non-supporting agents. This may not
be true for report types defined in future specifications. Documents be true for report types defined in future specifications. Documents
that introduce new report types MUST describe any limitations on that introduce new report types MUST describe any limitations on
their use across non-supporting agents. their use across non-supporting agents.
3.1. Overload Control Endpoints (Non normative) 3.1. Piggybacking Principle
The overload control solution can be considered as an overlay on top
of an arbitrary Diameter network. The overload control information
is exchanged over on a "DOIC association" established between two
communication endpoints. The endpoints, namely the "reacting node"
and the "reporting node" do not need to be adjacent Diameter peer
nodes, nor they need to be the end-to-end Diameter nodes in a typical
"client-server" deployment with multiple intermediate Diameter agent
nodes in between. The overload control endpoints are the two
Diameter nodes that decide to exchange overload control information
between each other. How the endpoints are determined is specific to
a deployment, a Diameter node role in that deployment and local
configuration.
The following diagrams illustrate the concept of Diameter Overload
Endpoints 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 Endpoint 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 Endpoints. One of the endpoints is the overload reporter
and the other is the overload reactor.
Figure 1 illustrates the most basic configuration where a client is
connected directly to a server. In this case, the Diameter session
and the DOIC association are both between the client and server.
+-----+ +-----+
| C | | S |
+-----+ +-----+
| DEP | | DEP |
+--+--+ +--+--+
| |
| |
|{Diameter Session}|
| |
|{DOIC Association}|
| |
Figure 1: Basic DOIC deployment
In Figure 2 there is an agent that is not participating directly in
the exchange of overload reports. As a result, the Diameter session
and the DOIC association are still established between the client and
the server.
+-----+ +-----+ +-----+
| C | | A | | S |
+-----+ +--+--+ +-----+
| DEP | | | DEP |
+--+--+ | +--+--+
| | |
| | |
|----------{Diameter Session}---------|
| | |
|----------{DOIC Association}---------|
| | |
Figure 2: DOIC deployment with non participating agent
Figure 3 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 3: DOIC deployment with non-DOIC client and DOIC enabled agent
In Figure 4 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 for a set of servers.
+-----+ +-----+ +-----+
| C | | A | | S |
+-----+ +-----+ +-----+
| DEP | | DEP | | DEP |
+--+--+ +--+--+ +--+--+
| | |
| | |
|----------{Diameter Session}---------|
| | |
|{DOIC Association}|{DOIC Association}|
| | and/or
|----------{DOIC Association}---------|
| | |
Figure 4: A deployment where all nodes support DOIC
Figure 5 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}|
| | | and/or
|-------------------{DOIC Association}-------------------|
| | | |
Figure 5: A deployment with DOIC and non-DOIC supporting clients
Editor's note: Propose to remove C1, which is already shown in a
previous figure. Have this focus just on the non supporting client
scenario.
Figure 6 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}|
| | | and/or
|-------------------{DOIC Association}-------------------|
| | | |
Figure 6: A deployment with DOIC and non-DOIC supporting agents
Editor's note: Propose to add a non supporting server scenario.
3.2. Piggybacking Principle (Non normative)
The overload control AVPs defined in this specification have been The overload control AVPs defined in this specification have been
designed to be piggybacked on top of existing application message designed to be piggybacked on top of existing application messages.
exchanges. This is made possible by adding overload control top This is made possible by adding overload control top-level AVPs, the
level AVPs, the OC-OLR AVP and the OC-Supported-Features AVP as OC-OLR AVP and the OC-Supported-Features AVP, as optional AVPs into
optional AVPs into existing commands when the corresponding Command existing commands when the corresponding Command Code Format (CCF)
Code Format (CCF) specification allows adding new optional AVPs (see specification allows adding new optional AVPs (see Section 1.3.4 of
Section 1.3.4 of [RFC6733]). [RFC6733]).
Reacting nodes indicate support for DOIC by including the OC- Reacting nodes indicate support for DOIC by including the OC-
Supported-Features AVP all request messages originated or relayed by Supported-Features AVP in all request messages originated or relayed
the Diameter node. by the reacting node.
Reporting nodes indicate support for DOIC by including the OC- Reporting nodes indicate support for DOIC by including the OC-
Supported-Features AVP in all answer messages originated or relayed Supported-Features AVP in all answer messages originated or relayed
by the Diameter node. Reporting nodes also include overload reports by the reporting node. Reporting nodes also include overload reports
using the OC-OLR AVP in answer messages. using the OC-OLR AVP in answer messages.
Note: There is no new Diameter application defined to carry Note: There is no new Diameter application defined to carry
overload related AVPs. The DOIC AVPs are carried in existing overload related AVPs. The DOIC AVPs are carried in existing
Diameter application messages. Diameter application messages.
Note that the overload control solution does not have fixed server Note that the overload control solution does not have fixed server
and client roles. The endpoint role is determined based on the and client roles. The DOIC node role is determined based on the
message type: whether the message is a request (i.e. sent by a message type: whether the message is a request (i.e. sent by a
"reacting node") or an answer (i.e. send by a "reporting node"). "reacting node") or an answer (i.e. send by a "reporting node").
Therefore, in a typical "client-server" deployment, the "client" MAY Therefore, in a typical "client-server" deployment, the Diameter
report its overload condition to the "server" for any server Client MAY report its overload condition to the Diameter Server for
initiated message exchange. An example of such is the server any Diameter Server initiated message exchange. An example of such
requesting a re-authentication from a client. is the Diameter Server requesting a re-authentication from a Diameter
Client.
3.3. DOIC Capability Announcement (Non normative) 3.2. DOIC Capability Announcement
The DOIC solutions supports the ability for Diameter nodes to The DOIC solution supports the ability for Diameter nodes to
determine if other nodes in the path of a request support the determine if other nodes in the path of a request support the
solution. This capability is refered to as DOIC Capability solution. This capability is referred to as DOIC Capability
Announcement (DCA) and is separate from Diameter Capability Exchange. Announcement (DCA) and is separate from Diameter Capability Exchange.
The DCA mechanism is built around the piggybacking principle used for The DCA solution uses the OC-Supported-Features AVPs to indicate the
transporting Diameter overload AVPs. This includes both DCA AVPs and
AVPs associated with Diameter overload reports. This allows for the
DCA AVPs to be carried across Diameter nodes that do not support the
DOIC solution.
The DCA mechanism uses the OC-Supported-Features AVPs to indicate the
Diameter overload features supported. Diameter overload features supported.
The first node in the path of a Diameter request that supports the The first node in the path of a Diameter request that supports the
DOIC solution inserts the OC-Supported-Feature AVP in the request DOIC solution inserts the OC-Supported-Feature AVP in the request
message. This includes an indication that it supports the loss message. This includes an indication that it supports the loss
overload abatement algorithm defined in this specification (see overload abatement algorithm defined in this specification (see
Section 5). This insures that there is at least one commonly Section 5). This ensures that there is at least one commonly
supported overload abatement algorithm between the reporting node and supported overload abatement algorithm between the reporting node and
the reacting nodes in the path of the request. the reacting nodes in the path of the request.
DOIC must support deployments where Diameter Clients and/or DOIC must support deployments where Diameter Clients and/or
Diameter servers do not support the DOIC solution. In this Diameter Servers do not support the DOIC solution. In this
scenario, it is assumed that Diameter Agents that support the DOIC scenario, it is assumed that Diameter Agents that support the DOIC
solution will handle overload abatement for the non supporting solution will handle overload abatement for the non supporting
clients. In this case the DOIC agent will insert the OC- Diameter nodes. In this case the DOIC agent will insert the OC-
Supporting-Features AVP in requests that do not already contain Supporting-Features AVP in requests that do not already contain
one, telling the reporting node that there is a DOIC node that one, telling the reporting node that there is a DOIC node that
will handle overload abatement. will handle overload abatement.
The reporting node inserts the OC-Supported-Feature AVP in all answer The reporting node inserts the OC-Supported-Feature AVP in all answer
messages to requests that contained the OC-Supported-Feature AVP. messages to requests that contained the OC-Supported-Feature AVP.
The contents of the reporting node's OC-Supported-Feature AVP The contents of the reporting node's OC-Supported-Feature AVP
indicate the set of Diameter overload features supported by the indicate the set of Diameter overload features supported by the
reporting node with one exception. reporting node with one exception.
The reporting node only includes an indication of support for one The reporting node only includes an indication of support for one
overload abatement algorithm. This is the algorithm that the overload abatement algorithm. This is the algorithm that the
reporting node intends to use should it enter an overload condition. reporting node intends to use should it enter an overload condition
or requests to use while it actually is in an overload condition.
Reacting nodes can use the indicated overload abatement algorithm to Reacting nodes can use the indicated overload abatement algorithm to
prepare for possible overload reports. prepare for possible overload reports and must use the indicated
overload abatement algorithm if traffic reduction is actually
requested.
Note that the loss algorithm defined in this document is a Note that the loss algorithm defined in this document is a
stateless abatement algorithm. As a result it does not require stateless abatement algorithm. As a result it does not require
any actions by reacting nodes prior to the receipt of an overload any actions by reacting nodes prior to the receipt of an overload
report. Stateful abatement algorithms that base the abatement report. Stateful abatement algorithms that base the abatement
logic on a history of request messages sent might require reacting logic on a history of request messages sent might require reacting
nodes to maintain state to insure that overload reports can be nodes to maintain state to ensure that overload reports can be
properly handled. properly handled.
The individual features supported by the DOIC nodes are indicated in The individual features supported by the DOIC nodes are indicated in
the OC-Feature-Vector AVP. Any semantics associated with the the OC-Feature-Vector AVP. Any semantics associated with the
features will be defined in extension specifications that introduce features will be defined in extension specifications that introduce
the features. the features.
The DCA mechanism must also support the scenario where the set of The DCA mechanism must also support the scenario where the set of
features supported by the sender of a request and by agents in the features supported by the sender of a request and by agents in the
path of a request differ. In this case, the agent updates the OC- path of a request differ. In this case, the agent updates the OC-
Supported-Feature AVP to reflect the mixture of the two sets of Supported-Feature AVP to reflect the mixture of the two sets of
supported features. supported features.
The logic to determine the content of the modified OC-Supported- The logic to determine the content of the modified OC-Supported-
Feature AVP is out-of-scope for this specification and is left to Feature AVP is out-of-scope for this specification and is left to
implementation decisions. Care must be taken in doing so not to implementation decisions. Care must be taken not to introduce
introduce interoperability issues for downstream or upstream DOIC interoperability issues for downstream or upstream DOIC nodes.
nodes.
3.4. DOIC Overload Condition Reporting (Non normative) 3.3. DOIC Overload Condition Reporting
As with DOIC Capability Announcement, Overload Condition Reporting As with DOIC Capability Announcement, Overload Condition Reporting
uses new AVPs (Section 6.3) to indicate an overload condition. uses new AVPs (Section 6.3) to indicate an overload condition.
The OC-OLR AVP is referred to as an overload report. The OC-OLR AVP The OC-OLR AVP is referred to as an overload report. The OC-OLR AVP
includes the type of report, an overload report ID, the length of includes the type of report, a sequence number, the length of time
time that the report is valid and abatement algorithm specific AVPs. that the report is valid and abatement algorithm specific AVPs.
Two types of overload reports are defined in this document, host Two types of overload reports are defined in this document, host
reports and realm reports. reports and realm reports.
Host reports apply to traffic that is sent to a specific Diameter A report of type host is sent to indicate the overload of a specific
host. The applies to requests that contain the Destination-Host AVP Diameter node for the application-id indicated in the transaction.
that contains a DiameterIdentity that matches that of the overload When receiving an OLR of type host, a reacting node applies overload
report. These requests are referred to as host-routed requests. A abatement to what is referred to in this document as host-routed
host report also applies to realm-routed requests, requests that do requests. This is the set of requests that the reacting node knows
not have a Destination-Host AVP, when the selected route for the will be served by a particular host, either due to the presence of a
request is a connection to the impacted host. Destination-Host AVP, or by some other local knowledge on the part of
the reacting node. The reacting node applies overload abatement on
those host-routed requests which the reacting node knows will be
served by the server that matches the Origin-Host AVP of the received
message that contained the received OLR of type host.
Realm reports apply to realm-routed requests for a specific realm as Realm reports apply to realm-routed requests for a specific realm as
indicated in the Destination-Realm AVP. indicated in the Destination-Realm AVP.
Reporting nodes are responsible for determining the need for a Reporting nodes are responsible for determining the need for a
reduction of traffic. The method for making this determination is reduction of traffic. The method for making this determination is
implementation specific and depend on the type of overload report implementation specific and depend on the type of overload report
being generated. A host report, for instance, will generally be being generated. A host report, for instance, will generally be
generated by tracking utilization of resources required by the host generated by tracking utilization of resources required by the host
to handle transactions for the the Diameter application. A realm to handle transactions for the Diameter application. A realm report
report will generally impact the traffic sent to multiple hosts and, will generally impact the traffic sent to multiple hosts and, as
as such, will typically require tracking the capacity of the servers such, will typically require tracking the capacity of the servers
able to handle realm-routed requests for the application. able to handle realm-routed requests for the application.
Once a reporting node determines the need for a reduction in traffic, Once a reporting node determines the need for a reduction in traffic,
it uses the DOIC defined AVPs to report on the condition. These AVPs it uses the DOIC defined AVPs to report on the condition. These AVPs
are included in answer messages sent or relayed by the reporting are included in answer messages sent or relayed by the reporting
node. The reporting node indicates the overload abatement algorithm node. The reporting node indicates the overload abatement algorithm
that is to be used to handle the traffic reduction in the OC- that is to be used to handle the traffic reduction in the OC-
Supported-Features AVP. The OC-OLR AVP is used to communicate Supported-Features AVP. The OC-OLR AVP is used to communicate
information about the requested reduction. information about the requested reduction.
skipping to change at page 13, line 37 skipping to change at page 10, line 31
for applying the abatement algorithm to traffic impacted by the for applying the abatement algorithm to traffic impacted by the
overload report. The method used for that abatement is dependent on overload report. The method used for that abatement is dependent on
the abatement algorithm. The loss abatement algorithm is defined in the abatement algorithm. The loss abatement algorithm is defined in
this document (Section 5). Other abatement algorithms can be defined this document (Section 5). Other abatement algorithms can be defined
in extensions to the DOIC solutions. in extensions to the DOIC solutions.
As the conditions that lead to the generation of the overload report As the conditions that lead to the generation of the overload report
change the reporting node can send new overload reports requesting change the reporting node can send new overload reports requesting
greater reduction if the condition gets worse or less reduction if greater reduction if the condition gets worse or less reduction if
the condition improves. The reporting node sends an overload report the condition improves. The reporting node sends an overload report
with a duration of zero to indicate that the overlaod condition has with a duration of zero to indicate that the overload condition has
ended and use of the abatement algorithm is no longer needed. ended and use of the abatement algorithm is no longer needed.
The reacting node also determines when the overload report expires The reacting node also determines when the overload report expires
based on the OC-Validaty-Duration AVP in the overload report and based on the OC-Validity-Duration AVP in the overload report and
stops applying the abatement algorithm when the report expires. stops applying the abatement algorithm when the report expires.
3.5. DOIC Extensibility (Non normative) 3.4. DOIC Extensibility
The DOIC solutions is designed to be extensible. This extensibility The DOIC solution is designed to be extensible. This extensibility
is based on existing Diameter based extensibility mechanisms. is based on existing Diameter based extensibility mechanisms.
There are multiple categories of extensions that are expected. This There are multiple categories of extensions that are expected. This
includes the definition of new overload abatement algorithms, the includes the definition of new overload abatement algorithms, the
definition of new report types and new definitions of the scope of definition of new report types and new definitions of the scope of
messages impacted by an overload report. messages impacted by an overload report.
The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes
to communicate supported features. The specific features supported to communicate supported features. The specific features supported
by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC
skipping to change at page 14, line 9 skipping to change at page 11, line 4
There are multiple categories of extensions that are expected. This There are multiple categories of extensions that are expected. This
includes the definition of new overload abatement algorithms, the includes the definition of new overload abatement algorithms, the
definition of new report types and new definitions of the scope of definition of new report types and new definitions of the scope of
messages impacted by an overload report. messages impacted by an overload report.
The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes
to communicate supported features. The specific features supported to communicate supported features. The specific features supported
by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC by the DOIC node are indicated in the OC-Feature-Vector AVP. DOIC
extensions must define new values for the OC-Feature-Vector AVP. extensions must define new values for the OC-Feature-Vector AVP.
DOIC extensions also have the ability to add new AVPs to the OC- DOIC extensions also have the ability to add new AVPs to the OC-
Supported-Features AVP, if additional information about the new Supported-Features AVP, if additional information about the new
feature is required to be communicate. feature is required.
Overload abatement algorithms use the OC-OLR AVP to communicate Reporting nodes use the OC-OLR AVP to communicate overload
overload occurances. This AVP can also be extended to add new AVPs occurrences. This AVP can also be extended to add new AVPs allowing
allowing a reporting nodes to communicate additional information a reporting nodes to communicate additional information about
about handling an overload condition. handling an overload condition.
If necessary, new extensions can also define new top level AVPs. It If necessary, new extensions can also define new top-level AVPs. It
is, however, recommended that DOIC extensions use the OC-Supported- is, however, recommended that DOIC extensions use the OC-Supported-
Features and OC-OLR to carry all DOIC related AVPs. Features and OC-OLR to carry all DOIC related AVPs.
3.6. Simplified Example Architecture (Non normative) 3.5. Simplified Example Architecture
Figure 7 illustrates the simplified architecture for Diameter Figure 1 illustrates the simplified architecture for Diameter
overload information conveyance. See Section 3.1 for more discussion overload information conveyance.
and details how different Diameter nodes fit into the architecture
from the DOIC point of view.
Realm X Same or other Realms Realm X Same or other Realms
<--------------------------------------> <----------------------> <--------------------------------------> <---------------------->
+--^-----+ : (optional) : +--^-----+ : (optional) :
|Diameter| : : |Diameter| : :
|Server A|--+ .--. : +---^----+ : .--. |Server A|--+ .--. : +---^----+ : .--.
+--------+ | _( `. : |Diameter| : _( `. +---^----+ +--------+ | _( `. : |Diameter| : _( `. +---^----+
+--( )--:-| Agent |-:--( )--|Diameter| +--( )--:-| Agent |-:--( )--|Diameter|
+--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client | +--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client |
skipping to change at page 15, line 26 skipping to change at page 11, line 44
+---^----+ : : +---^----+ : :
End-to-end Overload Indication End-to-end Overload Indication
1) <-----------------------------------------------> 1) <----------------------------------------------->
Diameter Application Y Diameter Application Y
Overload Indication A Overload Indication A' Overload Indication A Overload Indication A'
2) <----------------------> <----------------------> 2) <----------------------> <---------------------->
standard base protocol standard base protocol standard base protocol standard base protocol
Figure 7: Simplified architecture choices for overload indication Figure 1: Simplified architecture choices for overload indication
delivery delivery
In Figure 7, the Diameter overload indication can be conveyed (1) In Figure 1, the Diameter overload indication can be conveyed (1)
end-to-end between servers and clients or (2) between servers and end-to-end between servers and clients or (2) between servers and
Diameter agent inside the realm and then between the Diameter agent Diameter agent inside the realm and then between the Diameter agent
and the clients when the Diameter agent acting as back-to-back-agent and the clients.
for DOIC purposes.
3.7. Considerations for Applications Integrating the DOIC Solution (Non
normative)
THis section outlines considerations to be taken into account when
integrating the DOIC solution into Diameter applications.
3.7.1. Application Classification (Non normative)
The following is a classification of Diameter applications and
requests. This discussion is meant to document factors that play
into decisions made by the Diameter identity responsible for handling
overload reports.
Section 8.1 of [RFC6733] defines two state machines that imply two
types of applications, session-less and session-based applications.
The primary difference between these types of applications is the
lifetime of Session-Ids.
For session-based applications, the Session-Id is used to tie
multiple requests into a single session.
In session-less applications, the lifetime of the Session-Id is a
single Diameter transaction, i.e. the session is implicitly
terminated after a single Diameter transaction and a new Session-Id
is generated for each Diameter request.
For the purposes of this discussion, session-less applications are
further divided into two types of applications:
Stateless applications:
Requests within a stateless application have no relationship to
each other. The 3GPP defined S13 application is an example of a
stateless application [S13], --> where only a Diameter command is
defined between a client and a server and no state is maintained
between two consecutive transactions.
Pseudo-session applications:
Applications that do not rely on the Session-Id AVP for
correlation of application messages related to the same session
but use other session-related information in the Diameter requests
for this purpose. The 3GPP defined Cx application [Cx] is an
example of a pseudo-session application.
The Credit-Control application defined in [RFC4006] is an example of
a Diameter session-based application.
The handling of overload reports must take the type of application
into consideration, as discussed in Section 3.7.2.
3.7.2. Application Type Overload Implications (Non normative)
This section discusses considerations for mitigating overload
reported by a Diameter entity. This discussion focuses on the type
of application. Section 3.7.3 discusses considerations for handling
various request types when the target server is known to be in an
overloaded state.
These discussions assume that the strategy for mitigating the
reported overload is to reduce the overall workload sent to the
overloaded entity. The concept of applying overload treatment to
requests targeted for an overloaded Diameter entity is inherent to
this discussion. The method used to reduce offered load is not
specified here but could include routing requests to another Diameter
entity known to be able to handle them, or it could mean rejecting
certain requests. For a Diameter agent, rejecting requests will
usually mean generating appropriate Diameter error responses. For a
Diameter client, rejecting requests will depend upon the application.
For example, it could mean giving an indication to the entity
requesting the Diameter service that the network is busy and to try
again later.
Stateless applications:
By definition there is no relationship between individual requests
in a stateless application. As a result, when a request is sent
or relayed to an overloaded Diameter entity - either a Diameter
Server or a Diameter Agent - the sending or relaying entity can
choose to apply the overload treatment to any request targeted for
the overloaded entity.
Pseudo-session applications:
For pseudo-session applications, there is an implied ordering of
requests. As a result, decisions about which requests towards an
overloaded entity to reject could take the command code of the
request into consideration. This generally means that
transactions later in the sequence of transactions should be given
more favorable treatment than messages earlier in the sequence.
This is because more work has already been done by the Diameter
network for those transactions that occur later in the sequence.
Rejecting them could result in increasing the load on the network
as the transactions earlier in the sequence might also need to be
repeated.
Session-based applications:
Overload handling for session-based applications must take into
consideration the work load associated with setting up and
maintaining a session. As such, the entity sending requests
towards an overloaded Diameter entity for a session-based
application might tend to reject new session requests prior to
rejecting intra-session requests. In addition, session ending
requests might be given a lower probability of being rejected as
rejecting session ending requests could result in session status
being out of sync between the Diameter clients and servers.
Application designers that would decide to reject mid-session
requests will need to consider whether the rejection invalidates
the session and any resulting session clean-up procedures.
3.7.3. Request Transaction Classification (Non normative)
Independent Request:
An independent request is not correlated to any other requests
and, as such, the lifetime of the session-id is constrained to an
individual transaction.
Session-Initiating Request:
A session-initiating request is the initial message that
establishes a Diameter session. The ACR message defined in
[RFC6733] is an example of a session-initiating request.
Correlated Session-Initiating Request:
There are cases when multiple session-initiated requests must be
correlated and managed by the same Diameter server. It is notably
the case in the 3GPP PCC architecture [PCC], where multiple
apparently independent Diameter application sessions are actually
correlated and must be handled by the same Diameter server.
Intra-Session Request:
An intra session request is a request that uses the same Session-
Id than the one used in a previous request. An intra session
request generally needs to be delivered to the server that handled
the session creating request for the session. The STR message
defined in [RFC6733] is an example of an intra-session requests.
Pseudo-Session Requests:
Pseudo-session requests are independent requests and do not use
the same Session-Id but are correlated by other session-related
information contained in the request. There exists Diameter
applications that define an expected ordering of transactions.
This sequencing of independent transactions results in a pseudo
session. The AIR, MAR and SAR requests in the 3GPP defined Cx
[Cx] application are examples of pseudo-session requests.
3.7.4. Request Type Overload Implications (Non normative)
The request classes identified in Section 3.7.3 have implications on
decisions about which requests should be throttled first. The
following list of request treatment regarding throttling is provided
as guidelines for application designers when implementing the
Diameter overload control mechanism described in this document. The
exact behavior regarding throttling is a matter of local policy,
unless specifically defined for the application.
Independent requests:
Independent requests can be given equal treatment when making
throttling decisions.
Session-initiating requests:
Session-initiating requests represent more work than independent
or intra-session requests. Moreover, session-initiating requests
are typically followed by other session-related requests. As
such, as the main objective of the overload control is to reduce
the total number of requests sent to the overloaded entity,
throttling decisions might favor allowing intra-session requests
over session-initiating requests. Individual session-initiating
requests can be given equal treatment when making throttling
decisions.
Correlated session-initiating requests:
A Request that results in a new binding, where the binding is used
for routing of subsequent session-initiating requests to the same
server, represents more work load than other requests. As such,
these requests might be throttled more frequently than other
request types.
Pseudo-session requests:
Throttling decisions for pseudo-session requests can take into
consideration where individual requests fit into the overall
sequence of requests within the pseudo session. Requests that are
earlier in the sequence might be throttled more aggressively than
requests that occur later in the sequence.
Intra-session requests
There are two classes of intra-sessions requests. The first class
consists of requests that terminate a session. The second one
contains the set of requests that are used by the Diameter client
and server to maintain the ongoing session state. Session
terminating requests should be throttled less aggressively in
order to gracefully terminate sessions, allow clean-up of the
related resources (e.g. session state) and get rid of the need for
other intra-session requests, reducing the session management
impact on the overloaded entity. The default handling of other
intra-session requests might be to treat them equally when making
throttling decisions. There might also be application level
considerations whether some request types are favored over others.
4. Solution Procedures (Normative) 4. Solution Procedures
This section outlines the normative behavior associated with the DOIC This section outlines the normative behavior associated with the DOIC
solution. solution.
4.1. Capability Announcement (Normative) 4.1. Capability Announcement
This section defines DOIC Capability Announcement (DCA) behavior. This section defines DOIC Capability Announcement (DCA) behavior.
The DCA procedures are used to indicate support for DOIC and support 4.1.1. Reacting Node Behavior
for DOIC features. The DOIC features include overload abatement
algorithms supported. It might also include new report types or
other extensions documented in the future.
Diameter nodes indicate support for DOIC by including the OC-
Supported-Features AVP in messages sent or handled by the node.
Diameter agents that support DOIC MUST ensure that all messages have
the OC-Supporting-Features AVP. If a message handled by the DOIC
agent does not include the OC-Supported-Features AVP then the DOIC
agent inserts the AVP. If the message already has the AVP then the
agent either leaves it unchanged in the relayed message or modifies
it to reflect a mixed set of DOIC features.
4.1.1. Reacting Node Behavior (Normative)
A reacting node MUST include the OC-Supported-Features AVP in all A reacting node MUST include the OC-Supported-Features AVP in all
request messages. request messages.
A reacting node MUST include the OC-Feature-Vector AVP with an A reacting node MAY include the OC-Feature-Vector AVP with an
indication of the loss algorithm. indication of the loss algorithm. A reacting node MUST include the
OC-Feature-Vector AVP to indicate support for abatement algorithms in
addition to the loss algorithm.
A reacting node SHOULD indicate support for all other DOIC features A reacting node SHOULD indicate support for all other DOIC features
it supports. it supports.
Not all DOIC features will necessarily apply to all transactions.
For instance, there may be a future extension that only applies to
session based applications. A reacting node that supports this
extension can choose to not include it for non session based
applications.
An OC-Supported-Features AVP in answer messages indicates there is a An OC-Supported-Features AVP in answer messages indicates there is a
reporting node for the transaction. The reacting node MAY take reporting node for the transaction. The reacting node MAY take
action based on the features indicated in the OC-Feature-Vector AVP. action based on the features indicated in the OC-Feature-Vector AVP.
Note that the loss abatement algorithm is the only feature Note that the loss abatement algorithm is the only feature
described in this document and it does not require action to be described in this document and it does not require action to be
taken by the reacting node except when the answer message also has taken when there is an active overload report. This behavior is
an overload report. This behavior is described in Section 4.2 and described in Section 4.2 and Section 5.
Section 5.
4.1.2. Reporting Node Behavior (Normative) 4.1.2. Reporting Node Behavior
Upon receipt of a request message, a reporting node determines if Upon receipt of a request message, a reporting node determines if
there is a reacting node for the transaction based on the presence of there is a reacting node for the transaction based on the presence of
the OC-Supported-Features AVP. the OC-Supported-Features AVP.
If the request message contains an OC-Supported-Features AVP then the
reporting node MUST include the OC-Supported-Features AVP in the
answer message for that transaction.
The reporting node MUST NOT include the OC-Supported-Features AVP,
OC-OLR AVP or any other overload control AVPs defined in extension
drafts in response messages for transactions where the request
message does not include the OC-Supported-Features AVP. Lack of the
OC-Supported-Features AVP in the request message indicates that there
is no reacting node for the transaction.
Based on the content of the OC-Supported-Features AVP in the request Based on the content of the OC-Supported-Features AVP in the request
message, the reporting node knows what overload control functionality message, the reporting node knows what overload control functionality
supported by reacting node(s). The reporting node then acts is supported by the reacting node. The reporting node then acts
accordingly for the subsequent answer messages it initiates. accordingly for the subsequent answer messages it initiates.
If the reqeust message contains an OC-Supported-Features AVP then the
reporting node MUST include the OC-Supported-Features AVP in the
answer message for that transaction.
The reporting node MUST indicate support for one and only one The reporting node MUST indicate support for one and only one
abatement algorithm in the OC-Feature-Vector AVP. The abatement abatement algorithm in the OC-Feature-Vector AVP. The abatement
algorithm included MUST be from the set of abatement algorithms algorithm included MUST be from the set of abatement algorithms
contained in the request messages OC-Supported-Features AVP. The contained in the request message's OC-Supported-Features AVP. The
abatement algorithm included indicates the abatement algorithm the abatement algorithm included MUST indicate the abatement algorithm
reporting node wants the reacting node to use when the reporting node the reporting node wants the reacting node to use when the reporting
enters an overload condition. node enters an overload condition.
The reporting node MUST NOT change the selected algorithm during a For an ongoing overload state, a reacting node MUST keep the
period of time that it is in an overload condition and, as a result, algorithm that was selected by the reporting node in further requests
is sending OC-OLR AVPs in answer messages. towards the reporting node. The reporting node SHOULD NOT change the
selected algorithm during a period of time that it is in an overload
condition and, as a result, is sending OC-OLR AVPs in answer
messages.
The reporting node SHOULD indicate support for other DOIC features it The reporting node SHOULD indicate support for other DOIC features
supports and that apply to the transaction. defined in extension drafts that it supports and that apply to the
transaction.
Note that not all DOIC features will apply to all Diameter Note that not all DOIC features will apply to all Diameter
applications or deployment scenarios. The features included in applications or deployment scenarios. The features included in
the OC-Feature-Vector AVP is based on local reporting node policy. the OC-Feature-Vector AVP are based on local reporting node
policy.
The reporting node MUST NOT include the OC-Supported-Features AVP, 4.1.3. Agent Behavior
OC-OLR AVP or any other overload control AVPs defined in extension
drafts in response messages for transactions where the request Diameter agents that support DOIC MUST ensure that all messages have
message does not include the OC-Supported-Features AVP. Lack of the the OC-Supporting-Features AVP. If a message handled by the DOIC
OC-Supported-Features AVP in the request message indicates that there agent does not include the OC-Supported-Features AVP then the DOIC
is no reacting node for the transaction. agent inserts the AVP. If the message already has the AVP then the
agent either leaves it unchanged in the relayed message or modifies
it to reflect a mixed set of DOIC features.
An agent MAY modify the OC-Supported-Features AVP carried in answer An agent MAY modify the OC-Supported-Features AVP carried in answer
messages. messages.
4.1.3. Agent Behavior (Normative) For instance, if the agent supports a superset of the features
reported by the reacting node then the agent might choose, based
on local policy, to advertise that superset of features to the
reporting node.
Editor's note -- Need to add this section. If the agent modifies the OC-Supported-Features AVP sent to the
reporting node then it might also need to modify the OC-Supported-
Features AVP sent to a reacting node in the subsequent answer
message, as it cannot send an indication of support for features
that are not supported by the reacting node.
4.2. Overload Report Processing (Normative) Editor's note: There is an open issue on the wording around agent
behavior in this case that needs to be resolved prior to finishing
this document.
4.2.1. Overload Control State (Normative) 4.2. Overload Report Processing
Both reacting and reporting nodes maintain an overload control state 4.2.1. Overload Control State
(OCS) for each endpoint (a host or a realm) they communicate with and
both endpoints have announced support for DOIC. See Sections 6.1 and Both reacting and reporting nodes maintain Overload Control State
4.1 for discussion about how the support for DOIC is determined. (OCS) for active overload conditions.
4.2.1.1. Overload Control State for Reacting Nodes 4.2.1.1. Overload Control State for Reacting Nodes
A reacting node maintains the following OCS per supported Diameter A reacting node SHOULD maintain the following OCS per supported
application: Diameter application:
o A host-type Overload Control State for each Destination-Host o A host-type OCS entry for each Destination-Host to which it sends
towards which it sends host-type requests and host-type requests and
o A realm-type Overload Control State for each Destination-Realm o A realm-type OCS entry for each Destination-Realm to which it
towards which it sends realm-type requests. sends realm-type requests.
A host-type Overload Control State may be identified by the pair of A host-type OCS entry is identified by the pair of Application-Id and
Application-Id and Destination-Host. A realm-type Overload Control Host-Id.
State may be identified by the pair of Application-Id and
Destination-Realm. The host-type/realm-type Overload Control State A realm-type OCS entry is identified by the pair of Application-Id
for a given pair of Application and Destination-Host / Destination- and Realm-Id.
Realm could include the following information:
The host-type and realm-type OCS entries MAY include the following
information (the actual information stored is an implementation
decision):
o Sequence number (as received in OC-OLR) o Sequence number (as received in OC-OLR)
o Time of expiry (derived from OC-Validity-Duration AVP received in
the OC-OLR AVP and time of reception of the message carrying OC-
OLR AVP)
o Time of expiry (deviated from validity duration as received in OC- o Selected Abatement Algorithm (as received in OC-Supported-Features
OLR and time of reception) AVP)
o Selected Abatement Algorithm (as received in OC-Supported- o Abatement Algorithm specific input data (as received within the
Features) OC-OLR AVP, for example, OC-Reduction-Percentage for the Loss
abatement algorithm)
o Algorithm specific input data (as received within OC-OLR, e.g. 4.2.1.2. Overload Control State for Reporting Nodes
Reduction Percentage for Loss)
4.2.1.2. Overload Control States for Reporting Nodes A reporting node SHOULD maintain OCS entries per supported Diameter
application, per supported (and eventually selected) Abatement
Algorithm and per report-type.
A reporting node maintains per supported Diameter application and per An OCS entry is identified by the pair of Application-Id and
supported (and eventually selected) Abatement Algorithm an Overload Abatement Algorithm.
Control State.
An Overload Control State may be identified by the pair of The OCS entry for a given pair of Application and Abatement Algorithm
Application-Id and supported Abatement Algorithm. MAY include the information (the actual information stored is an
implementation decision):
The Overload Control State for a given pair of Application and o Report type
Abatement Algorithm could include the information:
o Sequence number o Sequence number
o Validity Duration and Expiry Time o Validity Duration
o Algorithm specific input data (e.g. Reduction Percentage for o Expiration Time
Loss)
Overload Control States for reporting nodes containing a validity o Algorithm specific input data (for example, the Reduction
duration of 0 sec. should not expire before any previously sent Percentage for the Loss Abatement Algorithm)
(stale) OLR has timed out at any reacting node.
Editor's note: This statement is unclear and contradictory with other 4.2.1.3. Reacting Node Maintenance of Overload Control State
statements. A validity timer of zero seconds indicates that the
overload condition has ended and abatement is no longer requested.
4.2.1.3. Maintaining Overload Control State When a reacting node receives an OC-OLR AVP, it MUST determine if it
is for an existing or new overload condition.
Reacting nodes create a host-type OCS identified by OCS-Id = (app- For the remainder of this section the term OLR referres to the
id,host-id) when receiving an answer message of application app-id combination of the contents of the received OC-OLR AVP and the
containing an Orig-Host of host-id and a host-type OC-OLR AVP unless abatement algorithm indicated in the received OC-Supported-
such host-type OCS already exists. Features AVP.
Reacting nodes create a realm-type OCS identified by OCS-Id = (app- The OLR is for an existing overload condition if the reacting node
id,realm-id) when receiving an answer message of application app-id has an OCS that matches the received OLR.
containing an Orig-Realm of realm-id and a realm-type OC-OLR AVP
unless such realm type OCS already exists.
Reacting nodes delete an OCS when it expires (i.e. when current time For a host report-type this means it matches the app-id and host-id
minus reception time is greater than validity duration). in an existing host OCS entry.
Editor's note: Reacting nodes also delete on OCS with an updated OLR For a realm report-type this means it matches the app-id and realm-id
is received with a validity duration of zero. in an existing realm OCS entry.
Reacting nodes update the host-type OCS identified by OCS-Id = (app- If the OLR is for an existing overload condition then it MUST
id,host-id) when receiving an answer message of application app-id determine if the OLR is a retransmission or an update to the existing
containing an Orig-Host of host-id and a host-type OC-OLR AVP with a OLR.
sequence number higher than the stored sequence number.
Reacting nodes update the realm-type OCS identified by OCS-Id = (app- If the sequence number for the received OLR is greater than the
id,realm-id) when receiving an answer message of application app-id sequence number stored in the matching OCS entry then the reacting
containing an Orig-Realm of realm-id and a realm-type OC-OLR AVP with node MUST update the matching OCS entry.
a sequence number higher than the stored sequence number.
Reacting nodes do not delete an OCS when receiving an answer message If the sequence number for the received OLR is less than or equal to
that does not contain an OC-OLR AVP (i.e. absence of OLR means "no the sequence number in the matching OCS entry then the reacting node
change"). MUST silently ignore the received OLR. The matching OCS MUST NOT be
updated in this case.
Reporting nodes create an OCS identified by OCS-Id = (app-id,Alg) If the received OLR is for a new overload condition then the reacting
when receiving a request of application app-id containing an OC- node MUST generate a new OCS entry for the overload condition.
Supported-Features AVP indicating support of the Abatement Algorithm
Alg (which the reporting node selects) while being overloaded, unless
such OCS already exists.
Reporting nodes delete an OCS when it expires. For a host report-type this means it creates on OCS entry with the
app-id of the application-id in the received message and host-id of
the Origin-Host in the received message.
Editor's note: Reporting nodes should send updated overload reports Note: This solution assumes that the Origin-Host AVP in the answer
with a validity duration of zero for a period of time after an OCS message included by the reporting node is not changed along the
expires or is removed due to the overload condition ending. path to the reacting node.
Reporting nodes update the OCS identified by OCS-Id = (app-id,Alg) For a realm report-type this means it creates on OCS entry with the
when they detect the need to modify the requested amount of app-id of the application-id in the received message and realm-id of
application app-id traffic reduction. the Origin-Realm in the received message.
4.2.2. Reacting Node Behavior (Normative) If the received OLR contains a validity duration of zero ("0") then
the reacting node MUST update the OCS entry as being expired.
Once a reacting node receives an OC-OLR AVP from a reporting node, it Note that it is not necessarily appropriate to delete the OCS
applies traffic abatement based on the selected algorithm with the entry, as there is recommended behavior that the reacting node
reporting node and the current overload condition. The reacting node slowly returns to full traffic when ending an overload abatement
learns the reporting node supported abatement algorithms directly period.
from the received answer message containing the OC-Supported-Features
AVP.
The received OC-Supported-Features AVP does not change the existing The reacting node does not delete an OCS when receiving an answer
overload condition and/or traffic abatement algorithm settings if the message that does not contain an OC-OLR AVP (i.e. absence of OLR
OC-Sequence-Number AVP contains a value that is equal to the means "no change").
previously received/recorded value. If the OC-Supported-Features AVP
is received for the first time for the reporting node or the OC-
Sequence-Number AVP value is less than the previously received/
recorded value (and is outside the valid overflow window), then the
sequence number is stale (e.g. an intentional or unintentional
replay) and SHOULD be silently discarded.
As described in Section 6.3, the OC-OLR AVP contains the necessary 4.2.1.4. Reporting Node Maintenance of Overload Control State
information for the overload condition on the reporting node.
From the OC-Report-Type AVP contained in the OC-OLR AVP, the reacting A reporting node SHOULD create a new OCS entry when entering an
node learns whether the overload condition report concerns a specific overload condition.
host (as identified by the Origin-Host AVP of the answer message
containing the OC-OLR AVP) or the entire realm (as identified by the
Origin-Realm AVP of the answer message containing the OC-OLR AVP).
The reacting node learns the Diameter application to which the
overload report applies from the Application-ID of the answer message
containing the OC-OLR AVP. The reacting node MUST use this
information as an input for its traffic abatement algorithm. The
idea is that the reacting node applies different handling of the
traffic abatement, whether sent request messages are targeted to a
specific host (identified by the Diameter-Host AVP in the request) or
to any host in a realm (when only the Destination-Realm AVP is
present in the request). Note that future specifications MAY define
new OC-Report-Type AVP values that imply different handling of the
OC-OLR AVP. For example, in a form of new additional AVPs inside the
Grouped OC-OLR AVP that would define report target in a finer
granularity than just a host.
Editor's note: The above behavior for Realm reports is If the reporting node knows through absence of the OC-Supported-
inconsistent with the definition of realm reports in section Features AVP in received messages that there are no reacting nodes
Section 6.6. supporting DOIC then the reporting node can choose to not create
OCS entries.
If the OC-OLR AVP is received for the first time, the reacting node When generating a new OCS entry the sequence number MAY be set to any
MUST create overload control state associated with the related realm value if there is no unexpired overload report for previous overload
or a specific host in the realm identified in the message carrying conditions sent to any reacting node for the same application and
the OC-OLR AVP, as described in Section 4.2.1. report-type.
If the value of the OC-Sequence-Number AVP contained in the received When generating sequence numbers for new overload conditions, the new
OC-OLR AVP is equal to or less than the value stored in an existing sequence number MUST be greater than any sequence number in an active
overload control state, the received OC-OLR AVP SHOULD be silently (unexpired) overload report previously sent by the reporting node.
discarded. If the value of the OC-Sequence-Number AVP contained in This property MUST hold over a reboot of the reporting node.
the received OC-OLR AVP is greater than the value stored in an
existing overload control state or there is no previously recorded
sequence number, the reacting node MUST update the overload control
state associated with the realm or the specific node in the realm.
When an overload control state is created or updated, the reacting The reporting node MUST update an OCS entry when it needs to adjust
node MUST apply the traffic abatement requested in the OC-OLR AVP the validity duration of the overload condition at reacting nodes.
using the algorithm announced in the OC-Supported-Features AVP
contained in the received answer message along with the OC-OLR AVP.
The validity duration of the overload information contained in the For instance, if the reporting node wishes to instruct reacting
OC-OLR AVP is either explicitly indicated in the OC-Validity-Duration nodes to continue overload abatement for a longer period of time
AVP or is implicitly equals to the default value (5 seconds) if the that originally communicated. This also applies if the reporting
OC-Validity-Duration AVP is absent. The reacting node MUST maintain node wishes to shorten the period of time that overload abatement
the validity duration in the overload control state. Once the is to continue.
validity duration times out, the reacting node MUST assume the
overload condition reported in a previous OC-OLR AVP has ended.
A value of zero ("0") received in the OC-Validity-Duration in an A reporting node MUST NOT update the abatement algorithm in an active
updated overload report indicates that the overload condition has OCS entry.
ended and that the overload state is no longer valid.
In the case that the validity duration expires or is explicitly A reporting node MUST update an OCS entry when it wishes to adjust
signaled as being no longer valid the state associated with the any abatement algorithm specific parameters, including the reduction
overload report MUST be removed and any abatement associated with the percentage used for the Loss abatement algorithm.
overload report MUST be ended in a controlled fashion. After
removing the overload state the sequence number MUST NOT be used for
future comparisons of sequence numbers.
4.2.3. Reporting Node Behavior (Normative) For instance, if the reporting node wishes to change the reduction
percentage either higher, if the overload condition has worsened,
or lower, if the overload condition has improved, then the
reporting node would update the appropriate OCS entry.
A reporting node is a Diameter node inserting an OC-OLR AVP in a The reporting node MUST update the sequence number associated with
Diameter message in order to inform a reacting node about an overload the OCS entry anytime the contents of the OCS entry are changed.
condition and request Diameter traffic abatement. This will result in a new sequence number being sent to reacting
nodes, instructing the reacting nodes to process the OC-OLR AVP.
The operation on the reporting node is straight forward. The A reporting node SHOULD update an OCS entry with a validity duration
reporting node learns the capabilities of the reacting node when it of zero ("0") when the overload condition ends.
receives the OC-Supported-Features AVP as part of any Diameter
request message. If the reporting node shares at least one common
feature with the reacting node, then the DOIC can be enabled between
these two endpoints. See Section 4.1 for further discussion on the
capability and feature announcement between two endpoints.
When a traffic reduction is required due to an overload condition and If the reporting node knows that the OCS entries in the reacting
the overload control solution is supported by the sender of the nodes are near expiration then the reporting node can decide to
Diameter request, the reporting node MUST include an OC-Supported- delete the OCS entry.
Features AVP and an OC-OLR AVP in the corresponding Diameter answer.
The OC-OLR AVP contains the required traffic reduction and the OC- The reporting node MUST keep an OCS entry with a validity duration of
Supported-Features AVP indicates the traffic abatement algorithm to zero ("0") for a period of time long enough to ensure that any non-
apply. This algorithm MUST be one of the algorithms advertised by expired reacting node's OCS entry created as a result of the overload
the request sender. condition in the reporting node is deleted.
4.2.2. Reacting Node Behavior
When a reacting node sends a request it MUST determine if that
request matches an active OCS.
If the request matches and active OCS then the reacting node MUST
apply abatement treatment on the request. The abatement treatment
applied depends on the abatement algorithm stored in the OCS.
For the Loss abatement algorithm defined in this specification, see
Section 5 for the abatement logic applied.
If the abatement treatment results in throttling of the request and
if the reacting node is an agent then the agent MUST send an
appropriate error as defined in section Section 7.
In the case that the OCS entry validity duration expires or has a
validity duration of zero ("0"), meaning that it the reporting node
has explicitly signaled the end of the overload condition then
abatement associated with the overload abatement MUST be ended in a
controlled fashion.
4.2.3. Reporting Node Behavior
The operation on the reporting node is straight forward.
If there is an active OCS entry then the reporting node SHOULD
include the OC-OLR AVP in all answer messages to requests that
contain the OC-Supported-Features AVP and that match the active OCS
entry.
A request matches if the application-id in the request matches the
application-id in any active OCS entry and if the report-type in
the OCS entry matches a report-type supported by the reporting
node as indicated in the OC-Supported-Features AVP.
The contents of the OC-OLR AVP MUST contain all information necessary
for the abatement algorithm indicated in the OC-Supported-Features
AVP that is also included in the answer message.
A reporting node MAY choose to not resend an overload report to a
reacting node if it can guarantee that this overload report is
already active in the reacting node.
Note - In some cases (e.g. when there are one or more agents in
the path between reporting and reacting nodes, or when overload
reports are discarded by reacting nodes) the reporting node may
not be able to guarantee that the reacting node has received the
report.
A reporting node MUST NOT send overload reports of a type that has
not been advertised as supported by the reacting node.
Note that a reacting node advertises support for the host and
realm report types by including the OC-Supported-Features AVP in
the request. Support for other report types must be explicitly
indicated by new feature bits in the OC-Feature-Vector AVP.
A reporting node MAY rely on the OC-Validity-Duration AVP values for A reporting node MAY rely on the OC-Validity-Duration AVP values for
the implicit overload control state cleanup on the reacting node. the implicit overload control state cleanup on the reacting node.
However, it is RECOMMENDED that the reporting node always explicitly However, it is RECOMMENDED that the reporting node always explicitly
indicates the end of a overload condition. indicates the end of a overload condition.
The reporting node SHOULD indicate the end of an overload occurrence The reporting node SHOULD indicate the end of an overload occurrence
by sending a new OLR with OC-Validity-Duration set to a value of zero by sending a new OLR with OC-Validity-Duration set to a value of zero
("0"). The reporting node SHOULD insure that all reacting nodes ("0"). The reporting node SHOULD ensure that all reacting nodes
receive the updated overload report. receive the updated overload report.
4.2.4. Agent Behavior (Normative) All OLRs sent have an expiration time calculated by adding the
validity-duration contained in the OLR to the time the message was
sent. Transit time for the OLR can be safely ignored. The
reporting node can ensure that all reacting nodes have received
the OLR by continuing to send it in answer messages until the
expiration time for all OLRs sent for that overload condition have
expired.
Editor's note -- Need to add this section. When a reporting node sends an OLR, it effectively delegates any
necessary throttling to downstream nodes. Therefore, the reporting
node SHOULD NOT apply throttling to the set of messages to which the
OLR applies. That is, the same candidate set of messages SHOULD NOT
be throttled multiple times.
4.3. Protocol Extensibility (Normative) However, when the reporting node sends and OLR downstream, it MAY
still be responsible to apply other abatement methods such as
diversion. The reporting node might also need to throttle requests
for reasons other then overload. For example, an agent or server
might have a configured rate limit for each client, and throttle
requests that exceed that limit, even if such requests had already
been candidates for throttling by downstream nodes.
This document assumes that there is a single source for realm-reports
for a given realm, or that if multiple nodes can send realm reports,
that each such node has full knowledge of the overload state of the
entire realm. A reacting node cannot distinguish between receiving
realm-reports from a single node, or from multiple nodes.
Editor's Note: There is not yet consensus on the above two
paragraphs. Two alternatives are under consideration --
synchronization of sequence numbers and attribution of reports.
If no consensus is reached then it will be left to be addressed as
an extension.
4.3. Protocol Extensibility
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, new report types or other new functionality. abatement algorithms, new report types or other new functionality.
When defining a new extension a new feature bit MUST be defined for When defining a new extension a new feature bit MUST be defined for
the OC-Feature-Vector. This feature bit is used to communicate the OC-Feature-Vector. This feature bit is used to communicate
support for the new feature. support for the new feature.
The extention may also define new AVPs for use in DOIC Capability The extension MAY define new AVPs for use in DOIC Capability
Anouncement and for use in DOIC Overload reporting. These new AVP Announcement and for use in DOIC Overload reporting. These new AVPs
should be defined to be extensions to the OC-Supported-Features and SHOULD be defined to be extensions to the OC-Supported-Features and
OC-OLR AVPs defined in this document. OC-OLR AVPs defined in this document.
It should be noted that [RFC6733] defined Grouped AVP extension It should be noted that [RFC6733] defined Grouped AVP extension
mechanisms apply. This allows, for example, defining a new feature mechanisms apply. This allows, for example, defining a new feature
that is mandatory to be understood even when piggybacked on an that is mandatory to be understood even when piggybacked on an
existing applications. More specifically, the sub-AVPs inside the existing application.
OC-Supported-Features and OC-OLR AVP MAY have the M-bit set.
However, when overload control AVPs are piggybacked on top of an
existing applications, setting M-bit in sub-AVPs is NOT RECOMMENDED.
The handling of feature bits in the OC-Feature-Vector AVP that are The handling of feature bits in the OC-Feature-Vector AVP that are
not associated with overload abatement algorithms MUST be specified not associated with overload abatement algorithms MUST be specified
by the extensions that define the features. by the extensions that define the features.
When defining new report type values, the corresponding specification When defining new report type values, the corresponding specification
MUST define the semantics of the new report types and how they affect MUST define the semantics of the new report types and how they affect
the OC-OLR AVP handling. The specification MUST also reserve a the OC-OLR AVP handling. The specification MUST also reserve a
corresponding new feature, see the OC-Supported-Features and OC- corresponding new feature bit in the OC-Feature-Vector AVP.
Feature-Vector AVPs.
The OC-OLR AVP can be expanded with optional sub-AVPs only if a The OC-OLR AVP can be expanded with optional sub-AVPs only if a
legacy implementation can safely ignore them without breaking legacy DOIC implementation can safely ignore them without breaking
backward compatibility for the given OC-Report-Type AVP value implied backward compatibility for the given OC-Report-Type AVP value. If
report handling semantics. If the new sub-AVPs imply new semantics the new sub-AVPs imply new semantics for handling the indicated
for handling the indicated report type, then a new OC-Report-Type AVP report type, then a new OC-Report-Type AVP value MUST be defined.
value MUST be defined.
New features (feature bits in the OC-Feature-Vector AVP) and report New features (feature bits in the OC-Feature-Vector AVP) and report
types (in the OC-Report-Type AVP) MUST be registered with IANA. As types (in the OC-Report-Type AVP) MUST be registered with IANA. As
with any Diameter specification, new AVPs MUST also be registered with any Diameter specification, new AVPs MUST also be registered
with IANA. See Section 8 for the required procedures. with IANA. See Section 8 for the required procedures.
5. Loss Algorithm (Normative) 5. Loss Algorithm
This section documents the Diameter overload loss abatement This section documents the Diameter overload loss abatement
algorithm. algorithm.
5.1. Overview (Non normative) 5.1. Overview
The DOIC specification supports the ability for multiple overload The DOIC specification supports the ability for multiple overload
abatement algorithms to be specified. The abatement algorithm used abatement algorithms to be specified. The abatement algorithm used
for any instance of overload is determined by the Diameter Overload for any instance of overload is determined by the Diameter Overload
Capability Announcement process documented in Section 4.1. Capability Announcement process documented in Section 4.1.
The loss algorithm described in this section is the default algorithm The loss algorithm described in this section is the default algorithm
that must be supported by all Diameter nodes that support DOIC. that must be supported by all Diameter nodes that support DOIC.
The loss algorithm is designed to be a straightforward and stateless The loss algorithm is designed to be a straightforward and stateless
skipping to change at page 28, line 32 skipping to change at page 21, line 37
request a percentage reduction in the amount of traffic sent. The request a percentage reduction in the amount of traffic sent. The
traffic impacted by the requested reduction depends on the type of traffic impacted by the requested reduction depends on the type of
overload report. overload report.
Reporting nodes use a strategy of applying abatement logic to the Reporting nodes use a strategy of applying abatement logic to the
requested percentage of request messages sent (or handled in the case requested percentage of request messages sent (or handled in the case
of agents) by the reacting node that are impacted by the overload of agents) by the reacting node that are impacted by the overload
report. report.
From a conceptual level, the logic at the reacting node could be From a conceptual level, the logic at the reacting node could be
outlined as follows. In this discussion assume that the reacting outlined as follows.
node is also the sending node.
1. An overload report is received and the associated overload state 1. An overload report is received and the associated overload state
is saved by the reacting node. is either saved or updated (if required) by the reacting node.
2. A new Diameter request is generated by the application running on 2. A new Diameter request is generated by the application running on
the reacting node. the reacting node.
3. The reacting node determines that an active overload report 3. The reacting node determines that an active overload report
applies to the request. applies to the request, as indicated by the corresponding OCS
entry.
4. The reacting node determines if abatement should be applied to 4. The reacting node determines if abatement should be applied to
the request. One approach that could be taken would be to select the request. One approach that could be taken for each request
a random number between 1 and 100. If the random number is less is to select a random number between 1 and 100. If the random
than the indicated reduction percentage then the request is given number is less than the indicated reduction percentage then the
abatement treatment, otherwise the request is given normal request is given abatement treatment, otherwise the request is
routing treatment. given normal routing treatment.
5.2. Use of OC-Reduction-Percentage AVP
A reporting node using the loss algorithm must use the OC-Reduction-
Percentage AVP (Section 6.7 to indicated the desired percentage of
traffic reduction.)
Editor's note: The above duplicates what is in the OC-Reduction-
Percentage AVP section can probably be removed.
5.3. Reporting Node Behavior (Normative) 5.2. Reporting Node Behavior
The method a reporting nodes uses to determine the amount of traffic The method a reporting nodes uses to determine the amount of traffic
reduction required to address an overload condition is an reduction required to address an overload condition is an
implementation decision. implementation decision.
When a reporting node that has selected the loss abatement algorithm When a reporting node that has selected the loss abatement algorithm
determines the need to request a traffic reduction it must include an determines the need to request a traffic reduction it includes an OC-
OC-OLR AVP in all response messages. OLR AVP in response messages as described in Section 4.2.3.
The reporting node must indicate a percentage reduction in the OC- The reporting node MUST indicate a percentage reduction in the OC-
Reduction-Percentage AVP. Reduction-Percentage AVP.
The reporting node may change the reduction percentage in subsequent The reporting node MAY change the reduction percentage in subsequent
overload reports. When doing so the reporting node must conform to overload reports. When doing so the reporting node must conform to
overload report handing specified in Section 4.2.3. overload report handing specified in Section 4.2.3.
When the reporting node determines it no longer needs a reduction in When the reporting node determines it no longer needs a reduction in
traffic the reporting node should send an overload report indicating traffic the reporting node SHOULD send an overload report indicating
the overload report is no longer valid, as specified in the overload report is no longer valid, as specified in
Section 4.2.3. Section 4.2.3.
5.4. Reacting Node Behavior (Normative) 5.3. Reacting Node Behavior
The method a reacting node uses to determine which request messages The method a reacting node uses to determine which request messages
are given abatement treatment is an implementation decision. are given abatement treatment is an implementation decision.
When receiving an OC-OLR in an answer message where the algorithm When receiving an OC-OLR in an answer message where the algorithm
indicated in the OC-Supported-Features AVP is the loss algorithm, the indicated in the OC-Supported-Features AVP is the loss algorithm, the
reacting node must attempt to apply abatement treatment to the reacting node MUST apply abatement treatment to the requested
requested percentage of request messages sent. percentage of request messages sent.
Note: the loss algorithm is a stateless algorithm. As a result, Note: the loss algorithm is a stateless algorithm. As a result,
the reacting node does not guarantee that there will be an the reacting node does not guarantee that there will be an
absolute reduction in traffic sent. Rather, it guarantees that absolute reduction in traffic sent. Rather, it guarantees that
the requested percentage of new requests will be given abatement the requested percentage of new requests will be given abatement
treatment. treatment.
When applying overload abatement treatment for the load abatement
algorithm, the reacting node MUST abate, either by throttling or
diversion, the requested percentage of requests that would have
otherwise been sent to the reporting host or realm.
If reacting node comes out of the 100 percent traffic reduction as a If reacting node comes out of the 100 percent traffic reduction as a
result of the overload report timing out, the following concerns are result of the overload report timing out, the following concerns are
RECOMMENDED to be applied. The reacting node sending the traffic RECOMMENDED to be applied. The reacting node sending the traffic
should be conservative and, for example, first send "probe" messages should be conservative and, for example, first send "probe" messages
to learn the overload condition of the overloaded node before to learn the overload condition of the overloaded node before
converging to any traffic amount/rate decided by the sender. Similar converging to any traffic amount/rate decided by the sender. Similar
concerns apply in all cases when the overload report times out unless concerns apply in all cases when the overload report times out unless
the previous overload report stated 0 percent reduction. the previous overload report stated 0 percent reduction.
Editor's note: Need to add additional guidance to slowly increase If the reacting node does not receive an OLR in messages sent to the
the rate of traffic sent to avoid a sudden spike in traffic, as formerly overloaded node then the reacting node SHOULD slowly
the spike in traffic could result in oscillation of the need for
overload control.
If the reacting node does not receive a an OLR in messages sent to
the formally overloaded node then the reacting node should slowly
increase the rate of traffic sent to the overloaded node. increase the rate of traffic sent to the overloaded node.
It is suggested that the reacting node decrease the amount of traffic It is suggested that the reacting node decrease the amount of traffic
given abatement treatment by 20% each second until the reduction is given abatement treatment by 20% each second until the reduction is
completely removed and no traffic is given abatement treatment. completely removed and no traffic is given abatement treatment.
The goal of this behavior is to reduce the probability of overload The goal of this behavior is to reduce the probability of overload
condition thrashing where an immediate transition from 100% condition thrashing where an immediate transition from 100%
reduction to 0% reduction results in the reporting node moving reduction to 0% reduction results in the reporting node moving
quickly back into an overload condition. quickly back into an overload condition.
6. Attribute Value Pairs (Normative) 6. Attribute Value Pairs
This section describes the encoding and semantics of the Diameter This section describes the encoding and semantics of the Diameter
Overload Indication Attribute Value Pairs (AVPs) defined in this Overload Indication Attribute Value Pairs (AVPs) defined in this
document. document.
When added to existing commands, both OC-Feature-Vector and OC-OLR
AVPs SHOULD have the M-bit flag cleared to avoid backward
compatibility issues.
A new application specification can incorporate the overload control A new application specification can incorporate the overload control
mechanism specified in this document by making it mandatory to mechanism specified in this document by making it mandatory to
implement for the application and referencing this specification implement for the application and referencing this specification
normatively. In such a case, the OC-Feature-Vector and OC-OLR AVPs normatively. It is the responsibility of the Diameter application
reused in newly defined Diameter applications SHOULD have the M-bit designers to define how overload control mechanisms works on that
flag set. However, it is the responsibility of the Diameter application.
application designers to define how overload control mechanisms works
on that application.
6.1. OC-Supported-Features AVP 6.1. OC-Supported-Features AVP
The OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and The OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and
serves for two purposes. First, it announces a node's support for serves two purposes. First, it announces a node's support for the
the DOIC in general. Second, it contains the description of the DOIC solution in general. Second, it contains the description of the
supported DOIC features of the sending node. The OC-Supported- supported DOIC features of the sending node. The OC-Supported-
Features AVP MUST be included in every Diameter message a DOIC Features AVP MUST be included in every Diameter request message a
supporting node sends. DOIC supporting node sends.
OC-Supported-Features ::= < AVP Header: TBD1 > OC-Supported-Features ::= < AVP Header: TBD1 >
[ OC-Feature-Vector ] [ OC-Feature-Vector ]
* [ AVP ] * [ AVP ]
The OC-Feature-Vector sub-AVP is used to announce the DOIC features The OC-Feature-Vector sub-AVP is used to announce the DOIC features
supported by the endpoint, in the form of a flag bits field in which supported by the DOIC node, in the form of a flag bits field in which
each bit announces one feature or capability supported by the node each bit announces one feature or capability supported by the node
(see Section 6.2). The absence of the OC-Feature-Vector AVP (see Section 6.2). The absence of the OC-Feature-Vector AVP
indicates that only the default traffic abatement algorithm described indicates that only the default traffic abatement algorithm described
in this specification is supported. in this specification is supported.
A reacting node includes this AVP to indicate its capabilities to a
reporting node. For example, the endpoint (reacting node) may
indicate which (future defined) traffic abatement algorithms it
supports in addition to the default.
During the message exchange the overload control endpoints express
their common set of supported capabilities. The reacting node
includes the OC-Supported-Features AVP that announces what it
supports. The reporting node that sends the answer also includes the
OC-Supported-Features AVP that describes the capabilities it
supports. The set of capabilities advertised by the reporting node
depends on local policies. At least one of the announced
capabilities MUST match. If there is no single matching capability
the reacting node MUST act as if it does not implement DOIC and cease
inserting any DOIC related AVPs into any Diameter messages with this
specific reacting node.
Editor's note: The last sentence conflicts with the last sentence
two paragraphs up. In reality, there will always be at least one
matching capability as all nodes supporting DOIC must support the
loss algorithm. Suggest removing the last sentence.
6.2. OC-Feature-Vector AVP 6.2. OC-Feature-Vector AVP
The OC-Feature-Vector AVP (AVP code TBD6) is type of Unsigned64 and The OC-Feature-Vector AVP (AVP code TBD6) is type of Unsigned64 and
contains a 64 bit flags field of announced capabilities of an contains a 64 bit flags field of announced capabilities of a DOIC
overload control endpoint. The value of zero (0) is reserved. node. The value of zero (0) is reserved.
The following capabilities are defined in this document: The following capabilities are defined in this document:
OLR_DEFAULT_ALGO (0x0000000000000001) OLR_DEFAULT_ALGO (0x0000000000000001)
When this flag is set by the overload control endpoint it means When this flag is set by the DOIC node it means that the default
that the default traffic abatement (loss) algorithm is supported. traffic abatement (loss) algorithm is supported.
6.3. OC-OLR AVP 6.3. OC-OLR AVP
The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the
necessary information to convey an overload report. The OC-OLR AVP information necessary to convey an overload report on an overload
does not explicitly contain all information needed by the reacting condition at the reporting node. The OC-OLR AVP does not explicitly
node to decide whether a subsequent request must undergo a throttling contain all information needed by the reacting node to decide whether
process with the received reduction percentage. The value of the OC- a subsequent request must undergo a throttling process with the
Report-Type AVP within the OC-OLR AVP indicates which implicit received reduction percentage. The value of the OC-Report-Type AVP
information is relevant for this decision (see Section 6.6). The within the OC-OLR AVP indicates which implicit information is
application the OC-OLR AVP applies to is the same as the Application- relevant for this decision (see Section 6.6). The application the
Id found in the Diameter message header. The identity the OC-OLR AVP OC-OLR AVP applies to is the same as the Application-Id found in the
concerns is determined from the Origin-Host AVP (and Origin-Realm AVP Diameter message header. The host or realm the OC-OLR AVP concerns
as well) found from the encapsulating Diameter command. The OC-OLR is determined from the Origin-Host AVP and/or Origin-Realm AVP found
AVP is intended to be sent only by a reporting node. in the encapsulating Diameter command. The OC-OLR AVP is intended to
be sent only by a reporting node.
OC-OLR ::= < AVP Header: TBD2 > OC-OLR ::= < AVP Header: TBD2 >
< OC-Sequence-Number > < OC-Sequence-Number >
< OC-Report-Type > < OC-Report-Type >
[ OC-Reduction-Percentage ] [ OC-Reduction-Percentage ]
[ OC-Validity-Duration ] [ OC-Validity-Duration ]
* [ AVP ] * [ AVP ]
The OC-Validity-Duration AVP indicates the validity time of the
overload report associated with a specific sequence number, measured
after reception of the OC-OLR AVP. The validity time MUST NOT be
updated after reception of subsequent OC-OLR AVPs with the same
sequence number. The default value for the OC-Validity-Duration AVP
value is 5 (i.e., 5 seconds). When the OC-Validity-Duration AVP is
not present in the OC-OLR AVP, the default value applies.
Note that if a Diameter command were to contain multiple OC-OLR AVPs Note that if a Diameter command were to contain multiple OC-OLR AVPs
they all MUST have different OC-Report-Type AVP value. OC-OLR AVPs they all MUST have different OC-Report-Type AVP value. OC-OLR AVPs
with unknown values SHOULD be silently discarded and the event SHOULD with unknown values SHOULD be silently discarded by reacting nodes
be logged. and the event SHOULD be logged.
Editor's note: Need to specify what happens when two reports of
the same type are received.
6.4. OC-Sequence-Number AVP 6.4. OC-Sequence-Number AVP
The OC-Sequence-Number AVP (AVP code TBD3) is type of Unsigned64. The OC-Sequence-Number AVP (AVP code TBD3) is type of Unsigned64.
Its usage in the context of overload control is described in Its usage in the context of overload control is described in
Section 4.2. Section 4.2.
From the functionality point of view, the OC-Sequence-Number AVP MUST From the functionality point of view, the OC-Sequence-Number AVP MUST
be used as a non-volatile increasing counter between two overload be used as a non-volatile increasing counter for a sequence of
control endpoints. The sequence number is only required to be unique overload reports between two DOIC nodes for the same overload
between two overload control endpoints. Sequence numbers are treated occurrence. The sequence number is only required to be unique
in a uni-directional manner, i.e. two sequence numbers on each between two DOIC nodes. Sequence numbers are treated in a uni-
direction between two endpoints are not related or correlated. directional manner, i.e. two sequence numbers on each direction
between two DOIC nodes are not related or correlated.
When generating sequence numbers, the new sequence number MUST be
greater than any sequence number in an active overload report
previously sent by the reporting node. This property MUST hold over
a reboot of the reporting node.
6.5. OC-Validity-Duration AVP 6.5. OC-Validity-Duration AVP
The OC-Validity-Duration AVP (AVP code TBD4) is type of Unsigned32 The OC-Validity-Duration AVP (AVP code TBD4) is type of Unsigned32
and indicates in seconds the validity time of the overload report. and indicates in milliseconds the validity time of the overload
The number of seconds is measured after reception of the first OC-OLR report. The number of milliseconds is measured after reception of
AVP with a given value of OC-Sequence-Number AVP. The default value the first OC-OLR AVP with a given value of OC-Sequence-Number AVP.
for the OC-Validity-Duration AVP is 5 (i.e., 5 seconds). When the The default value for the OC-Validity-Duration AVP is 5000 (i.e., 5
OC-Validity-Duration AVP is not present in the OC-OLR AVP, the seconds). When the OC-Validity-Duration AVP is not present in the
default value applies. Validity duration with values above 86400 OC-OLR AVP, the default value applies. Validity duration with values
(i.e.; 24 hours) MUST NOT be used. Invalid duration values are above 86400 (i.e.; 24 hours) MUST NOT be used. Invalid duration
treated as if the OC-Validity-Duration AVP were not present and values are treated as if the OC-Validity-Duration AVP were not
result in the default value being used. present and result in the default value being used.
Editor's note: There is an open discussion on whether to have an
upper limit on the OC-Validity-Duration value, beyond that which can
be indicated by an Unsigned32.
A timeout of the overload report has specific concerns that need to 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 DOIC node acting on the earlier received
overload report(s). Section 6.7 discusses the impacts of timeout in overload report(s). Section 6.7 discusses the impacts of timeout in
the scope of the traffic abatement algorithms. the scope of the traffic abatement algorithms.
When a reporting node has recovered from overload, it SHOULD
invalidate any existing overload reports in a timely matter. This
can be achieved by sending an updated overload report (meaning the
OLR contains a new sequence number) with the OC-Validity-Duration AVP
value set to zero ("0"). If the overload report is about to expire
naturally, the reporting node MAY choose to simply let it do so.
A reacting node MUST invalidate and remove an overload report that
expires without an explicit overload report containing an OC-
Validity-Duration value set to zero ("0").
6.6. OC-Report-Type AVP 6.6. OC-Report-Type AVP
The OC-Report-Type AVP (AVP code TBD5) is type of Enumerated. The The OC-Report-Type AVP (AVP code TBD5) is type of Enumerated. The
value of the AVP describes what the overload report concerns. The value of the AVP describes what the overload report concerns. The
following values are initially defined: following values are initially defined:
0 A host report. The overload treatment should apply to requests 0 A host report. The overload treatment should apply to requests
for which all of the following conditions are true: for which all of the following conditions are true:
Either the Destination-Host AVP is present in the request and its Either the Destination-Host AVP is present in the request and its
value matches the value of the Origin-Host AVP of the received value matches the value of the Origin-Host AVP of the received
message that contained the OC-OLR AVP; or the Destination-Host is message that contained the OC-OLR AVP; or the Destination-Host is
not present in the request but the value of peer identity not present in the request but the value of the peer identity
associated with the connection used to send the request matches associated with the connection used to send the request matches
the value of the Origin-Host AVP of the received message that the value of the Origin-Host AVP of the received message that
contained the OC-OLR AVP. contained the OC-OLR AVP.
The value of the Destination-Realm AVP in the request matches the The value of the Destination-Realm AVP in the request matches the
value of the Origin-Realm AVP of the received message that value of the Origin-Realm AVP of the received message that
contained the OC-OLR AVP. contained the OC-OLR AVP.
The value of the Application-ID in the Diameter Header of the The value of the Application-ID in the Diameter Header of the
request matches the value of the Application-ID of the Diameter request matches the value of the Application-ID of the Diameter
Header of the received message that contained the OC-OLR AVP. Header of the received message that contained the OC-OLR AVP.
1 A realm report. The overload treatment should apply to requests 1 A realm report. The overload treatment should apply to requests
for which all of the following conditions are true: for which all of the following conditions are true:
The Destination-Host AVP is absent in the request. The Destination-Host AVP is absent in the requestand the value of
the peer identity associated with the connection used to send the
request does not match a server that could serve the request.
The value of the Destination-Realm AVP in the request matches the The value of the Destination-Realm AVP in the request matches the
value of the Origin-Realm AVP of the received message that value of the Origin-Realm AVP of the received message that
contained the OC-OLR AVP. contained the OC-OLR AVP.
The value of the Application-ID in the Diameter Header of the The value of the Application-ID in the Diameter Header of the
request matches the value of the Application-ID of the Diameter request matches the value of the Application-ID of the Diameter
Header of the received message that contained the OC-OLR AVP. Header of the received message that contained the OC-OLR AVP.
Editor's note: There is still an open issue on the definition of
Realm reports and whether what report types should be supported.
There is consensus that host reports should be supported. There
is discussion on Realm reports and Realm-Routed-Request reports.
The above definition applies to Realm-Routed-Request reports where
Realm reports are defined to apply to all requests that match the
realm, independent of the presence, absence or value of the
Destination-Host AVP.
The default value of the OC-Report-Type AVP is 0 (i.e. the host
report).
The OC-Report-Type AVP is envisioned to be useful for situations The OC-Report-Type AVP is envisioned to be useful for situations
where a reacting node needs to apply different overload treatments where a reacting node needs to apply different overload treatments
for different "types" of overload. For example, the reacting node(s) for different overload contexts. For example, the reacting node(s)
might need to throttle differently requests sent to a specific server might need to throttle differently requests sent to a specific server
(identified by the Destination-Host AVP in the request) and requests (identified by the Destination-Host AVP in the request) and requests
that can be handled by any server in a realm. The example in that can be handled by any server in a realm.
Appendix B.1 illustrates this usage.
6.7. OC-Reduction-Percentage AVP 6.7. OC-Reduction-Percentage AVP
The OC-Reduction-Percentage AVP (AVP code TBD8) is type of Unsigned32 The OC-Reduction-Percentage AVP (AVP code TBD8) is 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 send. The requested to reduce, compared to what it otherwise would send. The
OC-Reduction-Percentage AVP applies to the default (loss) algorithm OC-Reduction-Percentage AVP applies to the default (loss) algorithm
specified in this specification. However, the AVP can be reused for specified in this specification. However, the AVP can be reused for
future abatement algorithms, if its semantics fit into the new future abatement algorithms, if its semantics fit into the new
algorithm. algorithm.
The value of the Reduction-Percentage AVP is between zero (0) and one The value of the Reduction-Percentage AVP is between zero (0) and one
hundred (100). Values greater than 100 are ignored. The value of hundred (100). Values greater than 100 are ignored. The value of
100 means that all traffic is to be throttled, i.e. the reporting 100 means that all traffic is to be throttled, i.e. the reporting
node is under a severe load and ceases to process any new messages. node is under a severe load and ceases to process any new messages.
The value of 0 means that the reporting node is in a stable state and The value of 0 means that the reporting node is in a stable state and
has no need for the other endpoint to apply any traffic abatement. has no need for the reacting node to apply any traffic abatement.
The default value of the OC-Reduction-Percentage AVP is 0. When the The default value of the OC-Reduction-Percentage AVP is 0. When the
OC-Reduction-Percentage AVP is not present in the overload report, OC-Reduction-Percentage AVP is not present in the overload report,
the default value applies. the default value applies.
6.8. Attribute Value Pair flag rules 6.8. Attribute Value Pair flag rules
+---------+ +---------+
|AVP flag | |AVP flag |
|rules | |rules |
+----+----+ +----+----+
AVP Section | |MUST| AVP Section | |MUST|
Attribute Name Code Defined Value Type |MUST| NOT| Attribute Name Code Defined Value Type |MUST| NOT|
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Supported-Features TBD1 x.x Grouped | | V | |OC-Supported-Features TBD1 x.x Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-OLR TBD2 x.x Grouped | | V | |OC-OLR TBD2 x.x Grouped | | V |
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command within that application that includes the AVP. command within that application that includes the AVP.
The Diameter overload control AVPs SHOULD always be sent with the The Diameter overload control AVPs SHOULD always be sent with the
M-bit cleared when used within existing Diameter applications to M-bit cleared when used within existing Diameter applications to
avoid backward compatibility issues. Otherwise, when reused in newly avoid backward compatibility issues. Otherwise, when reused in newly
defined Diameter applications, the DOC related AVPs SHOULD have the defined Diameter applications, the DOC related AVPs SHOULD have the
M-bit set. M-bit set.
7. Error Response Codes 7. Error Response Codes
Editor's note: This section depends on resolution of issue #27. When a DOIC node rejects a Diameter request due to overload, the DOIC
node MUST select an appropriate error response code. This
determination is made based on the probability of the request
succeeding if retried on a different path.
A reporting node rejecting a Diameter request due to an overload
condition SHOULD send a DIAMETER-TOO-BUSY error response, if it can
assume that the same request may succeed on a different path.
If a reporting node knows or assumes that the same request will not
succeed on a different path, DIAMETER_UNABLE_TO_COMPLY error response
SHOULD be used. Retrying would consume valuable resources during an
occurrence of overload.
For instance, if the request arrived at the reporting node without
a Destination-Host AVP then the reporting node might determine
that there is an alternative Diameter node that could successfully
process the request and that retrying the transaction would not
negatively impact the reporting node. DIAMETER_TOO_BUSY would be
sent in this case.
For instance, if the request arrived at the reporting node with a
Destination-Host AVP populated with its own Diameter identity then
the reporting node can assume that retrying the request would
result in it coming to the same reporting node.
DIAMETER_UNABLE_TO_COMPLY would be sent in this case.
A second example is when an agent that supports the DOIC solution
is performing the role of a reacting node for a non supporting
client. Requests that are rejected as a result of DOIC throttling
by the agent in this scenario would generally be rejected with a
DIAMETER_UNABLE_TO_COMPLY response code.
8. IANA Considerations 8. IANA Considerations
8.1. AVP codes 8.1. AVP codes
New AVPs defined by this specification are listed in Section 6. All New AVPs defined by this specification are listed in Section 6. All
AVP codes allocated from the 'Authentication, Authorization, and AVP codes allocated from the 'Authentication, Authorization, and
Accounting (AAA) Parameters' AVP Codes registry. Accounting (AAA) Parameters' AVP Codes registry.
8.2. New registries 8.2. New registries
Three new registries are needed under the 'Authentication, Two new registries are needed under the 'Authentication,
Authorization, and Accounting (AAA) Parameters' registry. Authorization, and Accounting (AAA) Parameters' registry.
Section 6.2 defines a new "Overload Control Feature Vector" registry Section 6.2 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]. See registry using the Specification Required policy [RFC5226]. See
Section 6.2 for the initial assignment in the registry. Section 6.2 for the initial assignment in the registry.
Section 6.6 defines a new "Overload Report Type" registry with its Section 6.6 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].
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A similar attack involves an otherwise authorized Diameter node that A similar attack involves an otherwise authorized Diameter node that
sends an inappropriate overload report. For example, a server for sends an inappropriate overload report. For example, a server for
the realm "example.com" might send an overload report indicating that the realm "example.com" might send an overload report indicating that
a competitor's realm "example.net" is overloaded. If other nodes act a competitor's realm "example.net" is overloaded. If other nodes act
on the report, they may falsely believe that "example.net" is on the report, they may falsely believe that "example.net" is
overloaded, effectively reducing that realm's capacity. Therefore, overloaded, effectively reducing that realm's capacity. Therefore,
it's critical that nodes validate that an overload report received it's critical that nodes validate that an overload report received
from a peer actually falls within that peer's responsibility before from a peer actually falls within that peer's responsibility before
acting on the report or forwarding the report to other peers. For acting on the report or forwarding the report to other peers. For
example, an overload report from an peer that applies to a realm not example, an overload report from a peer that applies to a realm not
handled by that peer is suspect. handled by that peer is suspect.
An attacker might use the information in an overload report to assist An attacker might use the information in an overload report to assist
in certain attacks. For example, an attacker could use information in certain attacks. For example, an attacker could use information
about current overload conditions to time a DoS attack for maximum about current overload conditions to time a DoS attack for maximum
effect, or use subsequent overload reports as a feedback mechanism to effect, or use subsequent overload reports as a feedback mechanism to
learn the results of a previous or ongoing attack. learn the results of a previous or ongoing attack.
9.2. Denial of Service Attacks 9.2. Denial of Service Attacks
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This specification describes only means for a simple loss based This specification describes only means for a simple loss based
algorithm. Future algorithms can be added using the designed algorithm. Future algorithms can be added using the designed
solution extension mechanism. The new algorithms need to be solution extension mechanism. The new algorithms need to be
registered with IANA. See Sections 6.1 and 8 for the required IANA registered with IANA. See Sections 6.1 and 8 for the required IANA
steps. steps.
A.2. Agent Overload A.2. Agent Overload
This specification focuses on Diameter endpoint (server or client) This specification focuses on Diameter endpoint (server or client)
overload. A separate extension will be required to outline the overload. A separate extension will be required to outline the
handling the case of agent overload. handling of the case of agent overload.
A.3. DIAMETER_TOO_BUSY clarifications A.3. New Error Diagnostic AVP
The current [RFC6733] behavior in a case of DIAMETER_TOO_BUSY is The proposal was made to add a new Error Diagnostic AVP to supplement
somewhat under specified. For example, there is no information how the error responces to be able to indicate that overload was the
long the specific Diameter node is willing to be unavailable. A reason for the rejection of the message.
specification updating [RFC6733] should clarify the handling of
DIAMETER_TOO_BUSY from the error answer initiating Diameter node
point of view and from the original request initiating Diameter node
point of view. Further, the inclusion of possible additional
information providing AVPs should be discussed and possible be
recommended to be used.
Appendix B. Examples Appendix B. Deployment Considerations
B.1. Mix of Destination-Realm routed requests and Destination-Host Non supporting agents
routed requests
Diameter allows a client to optionally select the destination server Due to the way that realm-routed requests are handled in Diameter
of a request, even if there are agents between the client and the networks, with the server selection for the request done by an
server. The client does this using the Destination-Host AVP. In agent, it is recommended that deployments enable all agents that
cases where the client does not care if a specific server receives do server selection to support the DOIC solution prior to enabling
the request, it can omit Destination-Host and route the request using the DOIC solution in the Diameter network.
the Destination-Realm and Application Id, effectively letting an
agent select the server.
Clients commonly send mixtures of Destination-Host and Destination- Topology hiding interactions
Realm routed requests. For example, in an application that uses user
sessions, a client typically won't care which server handles a
session-initiating requests. But once the session is initiated, the
client will send all subsequent requests in that session to the same
server. Therefore it would send the initial request with no
Destination-Host AVP. If it receives a successful answer, the client
would copy the Origin-Host value from the answer message into a
Destination-Host AVP in each subsequent request in the session.
An agent has very limited options in applying overload abatement to There exist proxies that implement what is referred to as Topology
requests that contain Destination-Host AVPs. It typically cannot Hiding. This can include cases where the agent modifies the
route the request to a different server than the one identified in Origin-Host in answer messages. The behavior of the DOIC solution
Destination-Host. It's only remaining options are to throttle such is not well understood when this happens. As such, the DOIC
requests locally, or to send an overload report back towards the solution does not address this scenario.
client so the client can throttle the requests. The second choice is
usually more efficient, since it prevents any throttled requests from
being sent in the first place, and removes the agent's need to send
errors back to the client for each dropped request.
On the other hand, an agent has much more leeway to apply overload Appendix C. Requirements Conformance Analysis
abatement for requests that do not contain Destination-Host AVPs. If
the agent has multiple servers in its peer table for the given realm
and application, it can route such requests to other, less overloaded
servers.
If the overload severity increases, the agent may reach a point where This section contains the result of an analysis of the DOIC solutions
there is not sufficient capacity across all servers to handle even conformance to the requirements defined in [RFC7068].
realm-routed requests. In this case, the realm itself can be
considered overloaded. The agent may need the client to throttle
realm-routed requests in addition to Destination-Host routed
requests. The overload severity may be different for each server,
and the severity for the realm at is likely to be different than for
any specific server. Therefore, an agent may need to forward, or
originate, multiple overload reports with differing ReportType and
Reduction-Percentage values.
Figure 8 illustrates such a mixed-routing scenario. In this example, To be completed.
the servers S1, S2, and S3 handle requests for the realm "realm".
Any of the three can handle requests that are not part of a user
session (i.e. routed by Destination-Realm). But once a session is
established, all requests in that session must go to the same server.
Client Agent S1 S2 S3 Appendix D. Considerations for Applications Integrating the DOIC
| | | | | Solution
|(1) Request (DR:realm) | |
|-------->| | | |
| | | | |
| | | | |
| |Agent selects S1 | |
| | | | |
| | | | |
| | | | |
| |(2) Request (DR:realm) |
| |-------->| | |
| | | | |
| | | | |
| | |S1 overloaded, returns OLR
| | | | |
| | | | |
| | | | |
| |(3) Answer (OR:realm,OH:S1,OLR:RT=DH)
| |<--------| | |
| | | | |
| | | | |
| |sees OLR,routes DR traffic to S2&S3
| | | | |
| | | | |
| | | | |
|(4) Answer (OR:realm,OH:S1, OLR:RT=DH) |
|<--------| | | |
| | | | |
| | | | |
|Client throttles requests with DH:S1 |
| | | | |
| | | | |
| | | | |
|(5) Request (DR:realm) | |
|-------->| | | |
| | | | |
| | | | |
| |Agent selects S2 | |
| | | | |
| | | | |
| | | | |
| |(6) Request (DR:realm) |
| |------------------>| |
| | | | |
| | | | |
| | | |S2 is overloaded...
| | | | |
| | | | |
| | | | |
| |(7) Answer (OH:S2, OLR:RT=DH)|
| |<------------------| |
| | | | |
| | | | |
| |Agent sees OLR, realm now overloaded
| | | | |
| | | | |
| | | | |
|(8) Answer (OR:realm,OH:S2, OLR:RT=DH, OLR: RT=R)
|<--------| | | |
| | | | |
| | | | |
|Client throttles DH:S1, DH:S2, and DR:realm
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
Figure 8: Mix of Destination-Host and Destination-Realm Routed This section outlines considerations to be taken into account when
Requests integrating the DOIC solution into Diameter applications.
1. The client sends a request with no Destination-Host AVP (that is, D.1. Application Classification
a Destination-Realm routed request.)
2. The agent follows local policy to select a server from its peer The following is a classification of Diameter applications and
table. In this case, the agent selects S2 and forwards the request types. This discussion is meant to document factors that
request. play into decisions made by the Diameter identity responsible for
handling overload reports.
3. S1 is overloaded. It sends a answer indicating success, but also Section 8.1 of [RFC6733] defines two state machines that imply two
includes an overload report. Since the overload report only types of applications, session-less and session-based applications.
applies to S1, the ReportType is "Destination-Host". The primary difference between these types of applications is the
lifetime of Session-Ids.
4. The agent sees the overload report, and records that S1 is For session-based applications, the Session-Id is used to tie
overloaded by the value in the Reduction-Percentage AVP. It multiple requests into a single session.
begins diverting the indicated percentage of realm-routed traffic
from S1 to S2 and S3. Since it can't divert Destination-Host
routed traffic, it forwards the overload report to the client.
This effectively delegates the throttling of traffic with
Destination-Host:S1 to the client.
5. The client sends another Destination-Realm routed request. The Credit-Control application defined in [RFC4006] is an example of
a Diameter session-based application.
6. The agent selects S2, and forwards the request. In session-less applications, the lifetime of the Session-Id is a
single Diameter transaction, i.e. the session is implicitly
terminated after a single Diameter transaction and a new Session-Id
is generated for each Diameter request.
7. It turns out that S2 is also overloaded, perhaps due to all that For the purposes of this discussion, session-less applications are
traffic it took over for S1. S2 returns an successful answer further divided into two types of applications:
containing an overload report. Since this report only applies to
S2, the ReportType is "Destination-Host".
8. The agent sees that S2 is also overloaded by the value in Stateless applications:
Reduction-Percentage. This value is probably different than the
value from S1's report. The agent diverts the remaining traffic
to S3 as best as it can, but it calculates that the remaining
capacity across all three servers is no longer sufficient to
handle all of the realm-routed traffic. This means the realm
itself is overloaded. The realm's overload percentage is most
likely different than that for either S1 or S2. The agent
forward's S2's report back to the client in the Diameter answer.
Additionally, the agent generates a new report for the realm of
"realm", and inserts that report into the answer. The client
throttles requests with Destination-Host:S1 at one rate, requests
with Destination-Host:S2 at another rate, and requests with no
Destination-Host AVP at yet a third rate. (Since S3 has not
indicated overload, the client does not throttle requests with
Destination-Host:S3.)
Appendix C. Restructuring of -02 version of the draft Requests within a stateless application have no relationship to
each other. The 3GPP defined S13 application is an example of a
stateless application [S13], where only a Diameter command is
defined between a client and a server and no state is maintained
between two consecutive transactions.
This section captures the initial plan for restructuring the DOIC Pseudo-session applications:
specification from the -02 version to the new -03 version.
1. Introduction (non normative) Applications that do not rely on the Session-Id AVP for
-- Existing Text from section 1. -- correlation of application messages related to the same session
2. Terminology and Abbreviations (non normative) but use other session-related information in the Diameter requests
-- Existing Text from section 2. -- for this purpose. The 3GPP defined Cx application [Cx] is an
3. Solution Overview (Non normative) example of a pseudo-session application.
-- Existing text from section 3. --
3.1 Overload Control Endpoints (Non normative)
-- New text leveraging text from existing section 5.1 --
3.2 Piggybacking Principle (Non normative)
-- Existing text from existing section 5.2, with enhancements --
3.3 DOIC Capability Discovery (Non normative)
-- New text leveraging text from existing section 5.3 --
3.4 DOIC Overload Condition Reporting (Non normative)
-- New text --
3.5 DOIC Extensibility (Non normative)
-- New text leveraging text from existing Section 5.4 --
3.5 Simplified Example Architecture (Non normative)
-- Existing text from section 3.1.6, with enhancements --
3.6 Considerations for Applications Integrating the DOIC Solution (Non normative)
-- New text --
3.6.1. Application Classification (Non normative)
-- Existing text from section 3.1.1 --
3.6.2. Application Type Overload Implications (Non normative)
-- Existing text from section 3.1.2 --
3.6.3. Request Transaction Classification (Non normative)
-- Existing text from section 3.1.3 --
3.6.4. Request Type Overload Implications (Non normative)
-- Existing text from section 3.1.4 --
4. Solution Procedures (Normative)
4.1 Capability Announcement (Normative)
-- Existing text from section 5.3 --
4.1.1. Reacting Node Behavior (Normative)
-- Existing text from section 5.3.1 --
4.1.2. Reporting Node Behavior (Normative)
-- Existing text from section 5.3.2 --
4.1.3. Agent Behavior (Normative)
-- Existing text from section 5.3.3 --
4.2. Overload Report Processing (Normative)
4.2.1. Overload Control State (Normative)
-- Existing text from section 5.5.1 --
4.2.2. Reacting Node Behavior (Normative)
-- Existing text from section 5.5.2 --
4.2.3. Reporting Node Behavior (Normative)
-- Existing text from section 5.5.3 --
4.2.4. Agent Behavior (Normative)
-- Existing text from section 5.5.4 --
4.3. Protocol Extensibility (Normative)
-- Existing text from section 5.4 --
5. Loss Algorithm (Normative)
-- New text pulling from information spread through the document --
5.1. Overview (Non normative)
-- New text pulling from information spread through the document --
5.2. Reporting Node Behavior (Normative)
-- New text pulling from information spread through the document --
5.3. Reacting Node Behavior (Normative)
-- New text pulling from information spread through the document --
6. Attribute Value Pairs (Normative)
-- Existing text from section 4. --
6.1. OC-Supported-Features AVP
-- Existing text from section 4.1 --
6.2. OC-Feature-Vector AVP
-- Existing text from section 4.2 --
6.3. OC-OLR AVP
-- Existing text from section 4.3 --
6.4. OC-Sequence-Number AVP
-- Existing text from section 4.4 --
6.5. OC-Validity-Duration AVP
-- Existing text from section 4.5 --
6.6. OC-Report-Type AVP
-- Existing text from section 4.6 --
6.7. OC-Reduction-Percentage AVP
-- Existing text from section 4.7 --
6.8. Attribute Value Pair flag rules
-- Existing text from section 4.8 --
7. Error Response Codes
-- New text based on resolution of issue --
8. IANA Considerations
-- Existing text from section 7. --
8.1. AVP codes
-- Existing text from section 7.1 --
8.2. New registries
-- Existing text from section 7.2 --
9. Security Considerations
-- Existing text from section 8. --
9.1. Potential Threat Modes
-- Existing text from section 8.1 --
9.2. Denial of Service Attacks
-- Existing text from section 8.2 --
9.3. Non-Compliant Nodes
-- Existing text from section 8.3 --
9.4. End-to End-Security Issues
-- Existing text from section 8.4 --
10. Contributors
11. References
11.1. Normative References
11.2. Informative References
Appendix A. Issues left for future specifications
A.1. Additional traffic abatement algorithms
A.2. Agent Overload
A.3. DIAMETER_TOO_BUSY clarifications
A.4. Per reacting node reports
Appendix B. Examples
B.1. Mix of Destination-Realm routed requests and Destination-
Host routed requests
Authors' Addresses
Authors' Addresses The handling of overload reports must take the type of application
into consideration, as discussed in Appendix D.2.
D.2. Application Type Overload Implications
This section discusses considerations for mitigating overload
reported by a Diameter entity. This discussion focuses on the type
of application. Appendix D.3 discusses considerations for handling
various request types when the target server is known to be in an
overloaded state.
These discussions assume that the strategy for mitigating the
reported overload is to reduce the overall workload sent to the
overloaded entity. The concept of applying overload treatment to
requests targeted for an overloaded Diameter entity is inherent to
this discussion. The method used to reduce offered load is not
specified here but could include routing requests to another Diameter
entity known to be able to handle them, or it could mean rejecting
certain requests. For a Diameter agent, rejecting requests will
usually mean generating appropriate Diameter error responses. For a
Diameter client, rejecting requests will depend upon the application.
For example, it could mean giving an indication to the entity
requesting the Diameter service that the network is busy and to try
again later.
Stateless applications:
By definition there is no relationship between individual requests
in a stateless application. As a result, when a request is sent
or relayed to an overloaded Diameter entity - either a Diameter
Server or a Diameter Agent - the sending or relaying entity can
choose to apply the overload treatment to any request targeted for
the overloaded entity.
Pseudo-session applications:
For pseudo-session applications, there is an implied ordering of
requests. As a result, decisions about which requests towards an
overloaded entity to reject could take the command code of the
request into consideration. This generally means that
transactions later in the sequence of transactions should be given
more favorable treatment than messages earlier in the sequence.
This is because more work has already been done by the Diameter
network for those transactions that occur later in the sequence.
Rejecting them could result in increasing the load on the network
as the transactions earlier in the sequence might also need to be
repeated.
Session-based applications:
Overload handling for session-based applications must take into
consideration the work load associated with setting up and
maintaining a session. As such, the entity sending requests
towards an overloaded Diameter entity for a session-based
application might tend to reject new session requests prior to
rejecting intra-session requests. In addition, session ending
requests might be given a lower probability of being rejected as
rejecting session ending requests could result in session status
being out of sync between the Diameter clients and servers.
Application designers that would decide to reject mid-session
requests will need to consider whether the rejection invalidates
the session and any resulting session clean-up procedures.
D.3. Request Transaction Classification
Independent Request:
An independent request is not correlated to any other requests
and, as such, the lifetime of the session-id is constrained to an
individual transaction.
Session-Initiating Request:
A session-initiating request is the initial message that
establishes a Diameter session. The ACR message defined in
[RFC6733] is an example of a session-initiating request.
Correlated Session-Initiating Request:
There are cases when multiple session-initiated requests must be
correlated and managed by the same Diameter server. It is notably
the case in the 3GPP PCC architecture [PCC], where multiple
apparently independent Diameter application sessions are actually
correlated and must be handled by the same Diameter server.
Intra-Session Request:
An intra session request is a request that uses the same Session-
Id than the one used in a previous request. An intra session
request generally needs to be delivered to the server that handled
the session creating request for the session. The STR message
defined in [RFC6733] is an example of an intra-session requests.
Pseudo-Session Requests:
Pseudo-session requests are independent requests and do not use
the same Session-Id but are correlated by other session-related
information contained in the request. There exists Diameter
applications that define an expected ordering of transactions.
This sequencing of independent transactions results in a pseudo
session. The AIR, MAR and SAR requests in the 3GPP defined Cx
[Cx] application are examples of pseudo-session requests.
D.4. Request Type Overload Implications
The request classes identified in Appendix D.3 have implications on
decisions about which requests should be throttled first. The
following list of request treatment regarding throttling is provided
as guidelines for application designers when implementing the
Diameter overload control mechanism described in this document. The
exact behavior regarding throttling is a matter of local policy,
unless specifically defined for the application.
Independent requests:
Independent requests can generally be given equal treatment when
making throttling decisions, unless otherwise indicated by
application requirements or local policy.
Session-initiating requests:
Session-initiating requests often represent more work than
independent or intra-session requests. Moreover, session-
initiating requests are typically followed by other session-
related requests. Since the main objective of the overload
control is to reduce the total number of requests sent to the
overloaded entity, throttling decisions might favor allowing
intra-session requests over session-initiating requests. In the
absence of local policies or application specific requirements to
the contrary, Individual session-initiating requests can be given
equal treatment when making throttling decisions.
Correlated session-initiating requests:
A Request that results in a new binding, where the binding is used
for routing of subsequent session-initiating requests to the same
server, represents more work load than other requests. As such,
these requests might be throttled more frequently than other
request types.
Pseudo-session requests:
Throttling decisions for pseudo-session requests can take into
consideration where individual requests fit into the overall
sequence of requests within the pseudo session. Requests that are
earlier in the sequence might be throttled more aggressively than
requests that occur later in the sequence.
Intra-session requests:
There are two types of intra-sessions requests, requests that
terminate a session and the remainder of intra-session requests.
Implementors and operators may choose to throttle session-
terminating requests less aggressively in order to gracefully
terminate sessions, allow clean-up of the related resources (e.g.
session state) and avoid the need for additional intra-session
requests. Favoring session-termination requests may reduce the
session management impact on the overloaded entity. The default
handling of other intra-session requests might be to treat them
equally when making throttling decisions. There might also be
application level considerations whether some request types are
favored over others.
Authors' Addresses
Jouni Korhonen (editor) Jouni Korhonen (editor)
Broadcom Broadcom
Porkkalankatu 24 Porkkalankatu 24
Helsinki FIN-00180 Helsinki FIN-00180
Finland Finland
Email: jouni.nospam@gmail.com Email: jouni.nospam@gmail.com
Steve Donovan (editor) Steve Donovan (editor)
Oracle Oracle
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