draft-ietf-dime-ovli-00.txt   draft-ietf-dime-ovli-01.txt 
Diameter Maintenance and Extensions J. Korhonen, Ed. Diameter Maintenance and Extensions J. Korhonen, Ed.
(DIME) Broadcom (DIME) Broadcom
Internet-Draft S. Donovan Internet-Draft S. Donovan
Intended status: Standards Track B. Campbell Intended status: Standards Track B. Campbell
Expires: May 26, 2014 Oracle Expires: June 20, 2014 Oracle
November 22, 2013 L. Morand
Orange Labs
December 17, 2013
Diameter Overload Indication Conveyance Diameter Overload Indication Conveyance
draft-ietf-dime-ovli-00.txt draft-ietf-dime-ovli-01.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 39 skipping to change at page 1, line 41
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 26, 2014. This Internet-Draft will expire on June 20, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Architectural Assumptions . . . . . . . . . . . . . . . . 6 3.1. Architectural Assumptions . . . . . . . . . . . . . . . . 5
3.1.1. Application Classification . . . . . . . . . . . . . . 7 3.1.1. Application Classification . . . . . . . . . . . . . . 5
3.1.2. Application Type Overload Implications . . . . . . . . 8 3.1.2. Application Type Overload Implications . . . . . . . . 6
3.1.3. Request Transaction Classification . . . . . . . . . . 9 3.1.3. Request Transaction Classification . . . . . . . . . . 8
3.1.4. Request Type Overload Implications . . . . . . . . . . 10 3.1.4. Request Type Overload Implications . . . . . . . . . . 9
3.1.5. Diameter Deployment Scenarios . . . . . . . . . . . . 11 3.1.5. Diameter Agent Behaviour . . . . . . . . . . . . . . . 10
3.1.6. Diameter Agent Behaviour . . . . . . . . . . . . . . . 12 3.1.6. Simplified Example Architecture . . . . . . . . . . . 11
3.1.7. Simplified Example Architecture . . . . . . . . . . . 13 3.2. Conveyance of the Overload Indication . . . . . . . . . . 11
3.2. Conveyance of the Overload Indication . . . . . . . . . . 14 3.2.1. DOIC Capability Discovery . . . . . . . . . . . . . . 12
3.2.1. Negotiation and Versioning . . . . . . . . . . . . . . 14 3.3. Overload Condition Indication . . . . . . . . . . . . . . 12
3.2.2. Transmission of the Attribute Value Pairs . . . . . . 14 4. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 12
3.3. Overload Condition Indication . . . . . . . . . . . . . . 15 4.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 13
4. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 15 4.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 14
4.1. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 15 4.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . . 16 4.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . . 15
4.3. TimeStamp AVP . . . . . . . . . . . . . . . . . . . . . . 17 4.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . . 15
4.4. ValidityDuration AVP . . . . . . . . . . . . . . . . . . . 17 4.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . . 16
4.5. ReportType AVP . . . . . . . . . . . . . . . . . . . . . . 17 4.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 16
4.6. Reduction-Percentage AVP . . . . . . . . . . . . . . . . . 18 4.8. Attribute Value Pair flag rules . . . . . . . . . . . . . 17
4.7. Attribute Value Pair flag rules . . . . . . . . . . . . . 19 5. Overload Control Operation . . . . . . . . . . . . . . . . . . 18
5. Overload Control Operation . . . . . . . . . . . . . . . . . . 19 5.1. Overload Control Endpoints . . . . . . . . . . . . . . . . 18
5.1. Overload Control Endpoints . . . . . . . . . . . . . . . . 19 5.2. Piggybacking Principle . . . . . . . . . . . . . . . . . . 21
5.2. Piggybacking Principle . . . . . . . . . . . . . . . . . . 23 5.3. Capability Announcement . . . . . . . . . . . . . . . . . 22
5.3. Capability Announcement . . . . . . . . . . . . . . . . . 23 5.3.1. Reacting Node Endpoint Considerations . . . . . . . . 22
5.3.1. Request Message Initiator Endpoint Considerations . . 24 5.3.2. Reporting Node Endpoint Considerations . . . . . . . . 23
5.3.2. Answer Message Initiating Endpoint Considerations . . 24 5.4. Protocol Extensibility . . . . . . . . . . . . . . . . . . 23
5.4. Protocol Extensibility . . . . . . . . . . . . . . . . . . 25 5.5. Overload Report Processing . . . . . . . . . . . . . . . . 24
5.5. Overload Report Processing . . . . . . . . . . . . . . . . 25 5.5.1. Overload Control State . . . . . . . . . . . . . . . . 24
5.5.1. Sender Endpoint Considerations . . . . . . . . . . . . 25 5.5.2. Reacting Node Considerations . . . . . . . . . . . . . 24
5.5.2. Receiver Endpoint Considerations . . . . . . . . . . . 25 5.5.3. Reporting Node Considerations . . . . . . . . . . . . 27
6. Transport Considerations . . . . . . . . . . . . . . . . . . . 25 6. Transport Considerations . . . . . . . . . . . . . . . . . . . 27
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
7.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 26 7.1. AVP codes . . . . . . . . . . . . . . . . . . . . . . . . 28
7.2. New registries . . . . . . . . . . . . . . . . . . . . . . 26 7.2. New registries . . . . . . . . . . . . . . . . . . . . . . 28
8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
8.1. Potential Threat Modes . . . . . . . . . . . . . . . . . . 27 8. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 28 8.1. Potential Threat Modes . . . . . . . . . . . . . . . . . . 28
8.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 28 8.2. Denial of Service Attacks . . . . . . . . . . . . . . . . 30
8.4. End-to End-Security Issues . . . . . . . . . . . . . . . . 28 8.3. Non-Compliant Nodes . . . . . . . . . . . . . . . . . . . 30
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.4. End-to End-Security Issues . . . . . . . . . . . . . . . . 30
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 31
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
11.1. Normative References . . . . . . . . . . . . . . . . . . . 30 10.1. Normative References . . . . . . . . . . . . . . . . . . . 32
11.2. Informative References . . . . . . . . . . . . . . . . . . 31 10.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. Issues left for future specifications . . . . . . . . 31 Appendix A. Issues left for future specifications . . . . . . . . 33
A.1. Additional traffic abatement algorithms . . . . . . . . . 31 A.1. Additional traffic abatement algorithms . . . . . . . . . 33
A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . . 31 A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . . 33
A.3. DIAMETER_TOO_BUSY clarifications . . . . . . . . . . . . . 31 A.3. DIAMETER_TOO_BUSY clarifications . . . . . . . . . . . . . 33
Appendix B. Conformance to Requirements . . . . . . . . . . . . . 32 Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 33
Appendix C. Examples . . . . . . . . . . . . . . . . . . . . . . 41 B.1. Mix of Destination-Realm routed requests and
C.1. 3GPP S6a interface overload indication . . . . . . . . . . 41 Destination-Host routed requests . . . . . . . . . . . . . 33
C.2. 3GPP PCC interfaces overload indication . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
C.3. Mix of Destination-Realm routed requests and
Destination-Host reouted requests . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
This specification defines a base solution for the Diameter Overload This specification defines a base solution for Diameter Overload
Control (DOC). The requirements for the solution are described and Control (DOC). The requirements for the solution are described and
discussed in the corresponding design requirements document discussed in the corresponding design requirements document
[I-D.ietf-dime-overload-reqs]. Note that the overload control [RFC7068]. Note that the overload control solution defined in this
solution defined in this specification does not address all the specification does not address all the requirements listed in
requirements listed in [I-D.ietf-dime-overload-reqs]. A number of [RFC7068]. A number of overload control related features are left
overload control related features are left for the future for the future specifications.
specifications. See Appendix A for more detailed discussion on
those.
The solution defined in this specification addresses the Diameter The solution defined in this specification addresses the Diameter
overload control between two endpoints (see Section 5.1). overload control between two endpoints (see Section 5.1).
Furthermore, the solution is designed to apply to existing and future Furthermore, the solution is designed to apply to existing and future
Diameter applications, requires no changes to the Diameter base Diameter applications, requires no changes to the Diameter base
protocol [RFC6733] and is deployable in environments where some protocol [RFC6733] and is deployable in environments where some
Diameter nodes do not implement the Diameter overload control Diameter nodes do not implement the Diameter overload control
solution defined in this specification. solution defined in this specification.
2. Terminology and Abbreviations 2. Terminology and Abbreviations
Server Farm Server Farm
A set of Diameter servers that can handle any request for a given A set of Diameter servers that can handle any request for a given
set of Diameter applications. While these servers support the set of Diameter applications. While these servers support the
same set of applications, they do not necessarily all have the same set of applications, they do not necessarily all have the
same capacity. An individual server farm might also support a same capacity. An individual server farm might also support a
subset of the users for a Diameter Realm. subset of the users for a Diameter Realm. A server farm may host
a single or multiple realms.
[OpenIssue: Is a server farm assumed to support a single realm?
That is, does it support a set of applications in a single realm?]
Server Front End
A Server Front End (SFE) is a role that can be performed by a
Diameter agent -- either a relay or a proxy -- that sits between
Diameter clients and a Server Farm. An SFE can perform various
functions for the server farm it sits in front of. This includes
some or all of the following functions:
* Diameter Routing
* Diameter layer load balancing
* Load Management
* Overload Management
* Topology Hiding
* Server Farm Identity Management
[OpenIssue: We used the concept of a server farm and SFE for
internal discussions. Do we still need those concepts to explain
the mechanism? It doesn't seem like we use them much.]
Diameter Routing: Diameter Routing:
Diameter Routing determines the destination of Diameter messages Diameter Routing between non-adjacent nodes relies on the
addressed to either a Diameter Realm and Application in general, Destination-Realm AVP to determine the Diameter realm in which the
or to a specific server using Destination-Host. This function is request needs to be processed. A Destination-Host AVP may also be
defined in [RFC6733]. Application level routing specifications present in the request to address a specific server inside the
that expand on [RFC6733] also exist. Diameter realm. This function is defined in [RFC6733]. However,
it is possible to enhance the routing decisions with application
level knowledge as it done in 3GPP PCC [3GPP.23.203] and NAI-based
source routing [RFC5729].
Diameter-layer Load Balancing: Diameter layer Load Balancing:
Diameter layer load balancing allows Diameter requests to be Diameter layer load balancing allows Diameter requests to be
distributed across the set of servers. Definition of this distributed across the set of servers. Definition of this
function is outside the scope of this document. function is outside the scope of this document.
Load Management:
This functionality ensures that the consolidated load state for
the server farm is collected, and processed. The exact algorithm
for computing the load at the SFE is implementation specific but
enough semantic of the conveyed load information needs to be
specified so that deterministic behavior can be ensured.
Overload Management:
The SFE is the entity that understands the consolidated overload
state for the server farm. Just as it is outside the scope of
this document to specify how a Diameter server calculates its
overload state, it is also outside the scope of this document to
specify how an SFE calculates the overload state for the set of
servers. This document describes how the SFE communicates
Overload information to Diameter Clients.
Topology Hiding: Topology Hiding:
Topology Hiding is loosely defined as ensuring that no Diameter Topology Hiding is loosely defined as ensuring that no Diameter
topology information about the server farm can be discovered from topology information about a Diameter network can be discovered
Diameter messages sent outside a predefined boundary (typically an from Diameter messages sent outside a predefined boundary
administrative domain). This includes obfuscating identifiers and (typically an administrative domain). This includes obfuscating
address information of Diameter entities in the server farm. It identifiers and address information of Diameter entities in the
can also include hiding the number of various Diameter entities in Diameter network. It can also include hiding the number of
the server farm. Identifying information can occur in many various Diameter entities in the Diameter network. Identifying
Diameter Attribute-Value Pairs (AVPs), including Origin-Host, information can occur in many Diameter Attribute-Value Pairs
Destination-Host, Route-Record, Proxy-Info, Session-ID and other (AVPs), including Origin-Host, Destination-Host, Route-Record,
AVPs. Proxy-Info, Session-ID and other AVPs.
Server Farm Identity Management:
Server Farm Identity Management (SFIM) is a mechanism that can be
used by the SFE to present a single Diameter identity that can be
used by clients to send Diameter requests to the server farm.
This requires that the SFE modifies Origin-Host information in
answers coming from servers in the server farm. An agent that
performs SFIM appears as a server from the client's perspective.
Throttling: Throttling:
Throttling is the reduction of the number of requests sent to an Throttling is the reduction of the number of requests sent to an
entity. Throttling can include a client dropping requests, or an entity. Throttling can include a client dropping requests, or an
agent rejecting requests with appropriate error responses. agent rejecting requests with appropriate error responses.
Clients and agents can also choose to redirect throttled requests Clients and agents can also choose to redirect throttled requests
to some other entity or entities capable of handling them. to some other entity or entities capable of handling them.
Reporting Node Reporting Node
skipping to change at page 6, line 40 skipping to change at page 5, line 38
A Diameter node that generates an overload report. (This may or A Diameter node that generates an overload report. (This may or
may not be the actually overloaded node.) may not be the actually overloaded node.)
Reacting Node Reacting Node
A Diameter node that consumes and acts upon a report. Note that A Diameter node that consumes and acts upon a report. Note that
"act upon" does not necessarily mean the reacting node applies an "act upon" does not necessarily mean the reacting node applies an
abatement algorithm; it might decide to delegate that downstream, abatement algorithm; it might decide to delegate that downstream,
in which case it also becomes a "reporting node". in which case it also becomes a "reporting node".
OLR Oveload Report. OLR Overload Report.
3. Solution Overview 3. Solution Overview
3.1. Architectural Assumptions 3.1. Architectural Assumptions
This section describes the high-level architectural and semantic This section describes the high-level architectural and semantic
assumptions that underly the Diameter Overload Control Mechanism. assumptions that underlie the Diameter Overload Control Mechanism.
3.1.1. Application Classification 3.1.1. Application Classification
The following is a classification of Diameter applications and The following is a classification of Diameter applications and
requests. This discussion is meant to document factors that play requests. This discussion is meant to document factors that play
into decisions made by the Diameter identity responsible for handling into decisions made by the Diameter identity responsible for handling
overload reports. overload reports.
Section 8.1 of [RFC6733] defines two state machines that imply two Section 8.1 of [RFC6733] defines two state machines that imply two
types of applications, session-less and session-based. The primary types of applications, session-less and session-based applications.
differentiator between these types of applications is the lifetime of The primary difference between these types of applications is the
Session-IDs. lifetime of Session-Ids.
For session-based applications, the session-id is used to tie For session-based applications, the Session-Id is used to tie
multiple requests into a single session. multiple requests into a single session.
In session-less applications, the lifetime of the session-id is a In session-less applications, the lifetime of the Session-Id is a
single Diameter transaction. single Diameter transaction, i.e. the session is implicitly
terminated after a single Diameter transaction and a new Session-Id
The 3GPP-defined S6a application is an example of a session-less is generated for each Diameter request.
application. The following, copied from section 7.1.4 of 29.272,
explicitly states that sessions are implicitly terminated and that
the server does not maintain session state:
"Between the MME and the HSS and between the SGSN and the HSS and
between the MME and the EIR, Diameter sessions shall be implicitly
terminated. An implicitly terminated session is one for which the
server does not maintain state information. The client shall not
send any re-authorization or session termination requests to the
server.
The Diameter base protocol includes the Auth-Session-State AVP as
the mechanism for the implementation of implicitly terminated
sessions.
The client (server) shall include in its requests (responses) the
Auth-Session-State AVP set to the value NO_STATE_MAINTAINED (1),
as described in [RFC6733]. As a consequence, the server shall not
maintain any state information about this session and the client
shall not send any session termination request. Neither the
Authorization-Lifetime AVP nor the Session-Timeout AVP shall be
present in requests or responses."
For the purposes of this discussion, session-less applications are For the purposes of this discussion, session-less applications are
further divided into two types of applications: further divided into two types of applications:
Stateless applications: Requests within a stateless application have Stateless applications:
no relationship to each other. The 3GPP defined S13 application
is an example of a stateless application.
Pseudo-session applications: While this class of application does Requests within a stateless application have no relationship to
not use the Diameter Session-ID AVP to correlate requests, there each other. The 3GPP defined S13 application is an example of a
is an implied ordering of transactions defined by the application. stateless application [3GPP.29.272], where only a Diameter command
The 3GPP defined Cx application [reference] is an example of a is defined between a client and a server and no state is
pseudo-session application. maintained between two consecutive transactions.
[OpenIssue: Do we assume that all requests in a pseudo-session Pseudo-session applications:
typically need to go to the same server?]
The accounting application defined in [RFC6733] and the Credit- Applications that do not rely on the Session-Id AVP for
Control application defined in [RFC4006] are examples of Diameter correlation of application messages related to the same session
session-based applications. but use other session-related information in the Diameter requests
for this purpose. The 3GPP defined Cx application [3GPP.29.229]
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 The handling of overload reports must take the type of application
into consideration, as discussed in Section 3.1.2. into consideration, as discussed in Section 3.1.2.
3.1.2. Application Type Overload Implications 3.1.2. Application Type Overload Implications
This section discusses considerations for mitigating overload This section discusses considerations for mitigating overload
reported by a Diameter entity. This discussion focuses on the type reported by a Diameter entity. This discussion focuses on the type
of application. Section 3.1.3 discusses considerations for handling of application. Section 3.1.3 discusses considerations for handling
various request types when the target server is known to be in an various request types when the target server is known to be in an
overloaded state. Section 3.1.5 discusses considerations for overloaded state.
handling overload conditions based on the network deployment
scenario.
These discussions assume that the strategy for mitigating the These discussions assume that the strategy for mitigating the
reported overload is to reduce the overall workload sent to the reported overload is to reduce the overall workload sent to the
overloaded entity. The concept of applying overload treatment to overloaded entity. The concept of applying overload treatment to
requests targeted for an overloaded Diameter entity is inherent to requests targeted for an overloaded Diameter entity is inherent to
this discussion. The method used to reduce offered load is not this discussion. The method used to reduce offered load is not
specified here but could include routing requests to another Diameter specified here but could include routing requests to another Diameter
entity known to be able to handle them, or it could mean rejecting entity known to be able to handle them, or it could mean rejecting
certain requests. For a Diameter agent, rejecting requests will certain requests. For a Diameter agent, rejecting requests will
usually mean generating appropriate Diameter error responses. For a usually mean generating appropriate Diameter error responses. For a
Diameter client, rejecting requests will depend upon the application. Diameter client, rejecting requests will depend upon the application.
For example, it could mean giving an indication to the entity For example, it could mean giving an indication to the entity
requesting the Diameter service that the network is busy and to try requesting the Diameter service that the network is busy and to try
again later. again later.
Stateless applications: By definition there is no relationship Stateless applications:
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-stateful applications: Pseudo stateful applications are also By definition there is no relationship between individual requests
stateless applications in that there is no session Diameter state in a stateless application. As a result, when a request is sent
maintained between transactions. There is, however, an implied or relayed to an overloaded Diameter entity - either a Diameter
ordering of requests. As a result, decisions about which Server or a Diameter Agent - the sending or relaying entity can
transactions to reject as a result of an overloaded entity could choose to apply the overload treatment to any request targeted for
take the command-code of the request into consideration. This the overloaded entity.
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.
Stateful applications: Overload handling for stateful applications Pseudo-session applications:
must take into consideration the work associated with setting up
an maintaining a session. As such, the entity handling overload For pseudo-session applications, there is an implied ordering of
of a Diameter entity for a stateful application might tend to requests. As a result, decisions about which requests towards an
reject new session requests before rejecting intra-session overloaded entity to reject could take the command code of the
requests. In addition, session ending requests might be given a request into consideration. This generally means that
lower priority of being rejected as rejecting session ending transactions later in the sequence of transactions should be given
requests could result in session status being out of sync between more favorable treatment than messages earlier in the sequence.
the Diameter clients and servers. Nodes that reject mid-session 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 requests will need to consider whether the rejection invalidates
the session, and any session clean-up that may be required. the session and any resulting session clean-up procedures.
3.1.3. Request Transaction Classification 3.1.3. Request Transaction Classification
Independent Request: An independent request is not a part of a Independent Request:
Diameter session and, as such, the lifetime of the session-id is
constrained to an individual transaction.
Session-Initiating Request: A session-initiating request is the An independent request is not correlated to any other requests
initial message that establishes a Diameter session. The ACR and, as such, the lifetime of the session-id is constrained to an
message defined in [RFC6733] is an example of a session-initiating individual transaction.
request.
Correlated Session-Initiating Request: There are cases, most notably Session-Initiating Request:
in the 3GPP PCC architecture, where multiple Diameter sessions are
correlated and must be handled by the same Diameter server. This
is a special case of a Session-Initiating Request. Gx CCR-I
requests and Rx AAR messages are examples of correlated session-
initiating requests.
[OpenIssue: The previous paragraph needs references.] 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.
Intra-Session Request: An intra session request is a request that Correlated Session-Initiating Request:
uses a session-id for an already established request. An intra
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 [3GPP.23.203], 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 session request generally needs to be delivered to the server that
handled the session creating request for the session. The STR handled the session creating request for the session. The STR
message defined in [RFC6733] is an example of an intra-session message defined in [RFC6733] is an example of an intra-session
requests. CCR-U and CCR-T requests defined in [RFC4006] are requests.
further examples of intra-session requests.
Pseudo-Session Requests: Pseudo session requests are independent Pseudo-Session Requests:
requests and, as such, the request transactions are not tied
together using the Diameter session-id. There exist Diameter 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. applications that define an expected ordering of transactions.
This sequencing of independent transactions results in a pseudo This sequencing of independent transactions results in a pseudo
session. The AIR, MAR and SAR requests in the 3GPP defined Cx session. The AIR, MAR and SAR requests in the 3GPP defined Cx
application are examples of pseudo-session requests. application are examples of pseudo-session requests.
3.1.4. Request Type Overload Implications 3.1.4. Request Type Overload Implications
The request classes identified in Section 3.1.3 have implications on The request classes identified in Section 3.1.3 have implications on
decisions about which requests should be throttled first. decisions about which requests should be throttled first. The
following list of request treatment regarding throttling is provided
Independent requests: Independent requests can be given equal as guidelines for application designers when implementing the
treatment when making throttling decisions. Diameter overload control mechanism described in this document.
Exact behavior regarding throttling must be defined per application.
Session-creating requests: Session-creating requests represent more
work than independent or intra-session requests. As such,
throttling decisions might favor intra-session requests over
session-creating requests. Individual session-creating requests
can be given equal treatment when making throttling decisions.
Correlated session-creating requests: A Request that results in a
new binding, where the binding is used for routing of subsequent
session-creating requests, represents more work 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 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 is a request that ends a session. The second
is a request that is used to convey session related state between
the Diameter client and server. Session ending request should be
throttled less aggressively in order to keep session state
consistent between the client and server, and possibly reduce the
sessions 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.
3.1.5. Diameter Deployment Scenarios
This section discusses various Diameter network deployment scenarios
and the implications of those deployment models on handling of
overload reports.
The scenarios vary based on the following:
o The presence or absence of Diameter agents
o Which Diameter entities support the DOC extension
o The amount of the network topology understood by Diameter clients
o The complexity of the Diameter server deployment for a Diameter
application
o Number of Diameter applications supported by Diameter clients and
Diameter servers
Without consideration for which elements support the DOC extension,
the following is a representative list of deployment scenarios:
o Client --- Server
o Client --- Multiple equivalent servers
o Client --- Agent --- Multiple equivalent servers
o Client --- Agent [ --- Agent ] --- Partitioned server
o Client --- Edge Agent [ --- Edge Agent] --- { Multiple Equivalent
Servers | Partitioned Servers }
o Client --- Session Correlating Agent --- Multiple Equivalent
Servers
[OpenIssue: Do the "multiple equivalent servers" cases change for
session-stateful applications? Do we need to distinguish equivalence
for session-initiation requests vs intra-session requests?]
The following is a list of representative DOC deployment scenarios: Independent requests:
o Direct connection between a DOC client and a DOC server Independent requests can be given equal treatment when making
throttling decisions.
o DOC client --- non-DOC agent --- DOC server Session-initiating requests:
o DOC client --- DOC agent --- DOC server Session-initiating requests represent more work than independent
or intra-session requests. Moreover, session-initiating requests
are typically followed by other related 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.
o Non-DOC client --- DOC agent --- DOC server Correlated session-initiating requests:
o Non-DOC client --- DOC agent --- Mix of DOC and non-DOC servers 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.
o DOC client --- agent --- Partitioned/Segmented DOC server Pseudo-session requests:
o DOC client --- agent --- agent --- Partitioned/Segmented DOC Throttling decisions for pseudo-session requests can take into
server 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.
o DOC client --- edge agent --- edge agent --- DOC server Intra-session requests
[OpenIssue: In the last 3 list entries, are the agents DOC or non- There are two classes of intra-sessions requests. The first class
DOC?] 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.
3.1.6. Diameter Agent Behaviour 3.1.5. Diameter Agent Behaviour
In the context of the Diameter Overload Indication Conveyance (DOIC) In the context of the Diameter Overload Indication Conveyance (DOIC)
and reacting to the overload information, the functional behaviour of and reacting to the overload information, the functional behaviour of
Diameter agents in front of servers, especially Diameter proxies, Diameter agents in front of servers, especially Diameter proxies,
needs to be common. This is important because agents may actively needs to be common. This is important because agents may actively
participate in the handling of an overload conditions. For example, participate in the handling of an overload conditions. For example,
they may make intelligent next hop selection decisions based on they may make intelligent next hop selection decisions based on
overload conditions, or aggregate overload information to be overload conditions, or aggregate overload information to be
disseminated downstream. Diameter agents may have other deployment disseminated downstream. Diameter agents may have other deployment
related tasks that are not defined in the Diameter base protocol related tasks that are not defined in the Diameter base protocol
[RFC6733]. These include, among other tasks, topology hiding, and [RFC6733]. These include, among other tasks, topology hiding, or
acting as a server front end for a server farm of real Diameter agent acting as a Server Front End (SFE) for a farm of Diameter
servers. servers.
Since the solution defined in this specification must not break the Since the solution defined in this specification must not break the
Diameter base protocol [RFC6733] at any time, great care has to be Diameter base protocol [RFC6733] at any time, great care has to be
taken not to assume functionality from the Diameter agents that would taken not to assume functionality from the Diameter agents that would
break base protocol behavior, or to assume agent functionality beyond break base protocol behavior, or to assume agent functionality beyond
the Diameter base protocol. Effectively this means the following the Diameter base protocol. Effectively this means the following
from a Diameter agent: from a Diameter agent:
o If a Diameter agent presents itself as the "end node", perhaps o If a Diameter agent presents itself as the "end node", as an agent
acting as an topology hiding SFE, the DOC mechanism MUST NOT leak acting as an topology hiding SFE, the agent is the final
information of the Diameter nodes behind it. From the Diameter destination of requests initiated by Diameter clients, the
client point of view the final destination to its requests and the original source for the corresponding answers and server-initiated
original source for the answers MUST be the Diameter agent. This requests. As a consequence, the DOIC mechanism MUST NOT leak
requirement means that such a Diameter agent acts as a back-to- information of the Diameter nodes behind it. This requirement
back-agent for DOC purposes. How the agent in this case appears means that such a Diameter agent acts as a back-to-back-agent for
to the Diameter nodes it is representing (i.e. the real Diameter DOIC purposes. How the Diameter agent in this case appears to the
servers), is an implementation and a deployment specific within Diameter servers in the farm, is specific to the implementation
the realm the Diameter agent is deployed. and deployment within the realm the Diameter agent is deployed.
o This requirement also implies that if the Diameter agent does not
impersonate the servers behind it, the Diameter dialogue is
established between clients and servers and any overload
information received by a client would be from a given server
identified by the Origin-Host identity.
[OpenIssue: We've discussed multiple situations where an agent might o If the Diameter agent does not impersonate the servers behind it,
insert an OLR. I don't think we mean to force them to always perform the Diameter dialogue is established between clients and servers
topology hiding or SFIM in order to do so. We cannot assume that an and any overload information received by a client would be from
OLR is always "from" or "about" the Origin-Host. Also, the section the server identified by the Origin-Host identity contained in the
seems to assume that topology hiding agents act as b2b overload Diameter message.
agents, but non-topology hiding agents never do. It don't think
that's the right abstraction. It's possible that topology-hiding
agents must do this, but I don't think we can preclude non-topology
hiding agents from also doing it, at least some of the time.]
3.1.7. Simplified Example Architecture 3.1.6. Simplified Example Architecture
Figure 1 illustrates the simplified architecture for Diameter Figure 1 illustrates the simplified architecture for Diameter
overload control. See Section 5.1 for more discussion and details overload information conveyance. See Section 5.1 for more discussion
how different Diameter nodes fit into the architecture from the DOIC and details how different Diameter nodes fit into the architecture
point of view. from the DOIC point of view.
Realm X Other Realms Realm X Same or other Realms
<--------------------------------------> <----------------------> <--------------------------------------> <---------------------->
+--^-----+ : (optional) : +--^-----+ : (optional) :
|Diameter| : : |Diameter| : :
|Server A|--+ .--. : +---^----+ : .--. |Server A|--+ .--. : +---^----+ : .--.
+--------+ | _( `. : |Diameter| : _( `. +---^----+ +--------+ | _( `. : |Diameter| : _( `. +---^----+
+--( )--:-| Agent |-:--( )--|Diameter| +--( )--:-| Agent |-:--( )--|Diameter|
+--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client | +--------+ | ( ` . ) ) : +-----^--+ : ( ` . ) ) | Client |
|Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+ |Diameter|--+ `--(___.-' : : `--(___.-' +-----^--+
|Server B| : : |Server B| : :
+---^----+ : : +---^----+ : :
End-to-end Overload Indication
1) <----------------------------------------------->
Diameter Application Y
Overload Indication A Overload Indication A' Overload Indication A Overload Indication A'
1) <----------------------> <----------------------> 2) <----------------------> <---------------------->
standard base protocol standard base protocol standard base protocol standard base protocol
End-to-end Overload Indication
2) <----------------------------------------------->
standard base protocol
Figure 1: Simplified architecture choices for overload indication Figure 1: Simplified architecture choices for overload indication
delivery delivery
In Figure 1, the Diameter overload indication can be conveyed (1)
end-to-end between servers and clients or (2) between servers and
Diameter agent inside the realm and then between the Diameter agent
and the clients when the Diameter agent acting as back-to-back-agent
for DOIC purposes.
3.2. Conveyance of the Overload Indication 3.2. Conveyance of the Overload Indication
The following features describe new Diameter AVPs used for sending The following sections describe new Diameter AVPs used for sending
overload reports, and for declaring support for certain DOC features. overload reports, and for declaring support for certain DOIC
features.
3.2.1. Negotiation and Versioning 3.2.1. DOIC Capability Discovery
Since the Diameter overload control mechanism is also designed to Support of DOIC may be specified as part of the functionality
work over existing application (i.e., the piggybacking principle), a supported by a new Diameter application. In this way, support of the
proper negotiation is hard to accomplish. The "capability considered Diameter application (discovered during capabilities
negotiation" is based on the existense of specific non-mandatory APV, exchange phase as defined in Diameter base protocol [RFC6733])
such as the OC-Feature-Vector AVP (see Section 4.1. Although the OC- indicates implicit support of the DOIC mechanism.
Feature-Vector AVP can be used to advertise a certain set of new or
When the DOIC mechanism is introduced in existing Diameter
applications, a specific capability discovery mechanism is required.
The "DOIC capability discovery mechanism" is based on the presence of
specific optional AVPs in the Diameter messages, such as the OC-
Supported-Features AVP (see Section 4.1). Although the OC-Supported-
Features AVP can be used to advertise a certain set of new or
existing Diameter overload control capabilities, it is not a existing Diameter overload control capabilities, it is not a
versioning solution per se, however, it can be used to achieve the versioning solution per se, however, it can be used to achieve the
same result. same result.
3.2.2. Transmission of the Attribute Value Pairs
The Diameter overload control APVs SHOULD always be sent as an
optional AVPs. This requirement stems from the fact that
piggybacking overload control information on top of existing
application cannot really use AVPs with the M-bit set. However,
there are certain exceptions as explained in Section 5.4.
From the Diameter overload control functionality point of view, the From the Diameter overload control functionality point of view, the
"Reacting node" is always the requester of the overload report "Reacting node" is the requester of the overload report information
information and the "Reporting node" is the provider of the overload and the "Reporting node" is the provider of the overload report. The
report. The overload report or the capability information in the OC-Supported-Features AVP in the request message is always
request message is always interpreted as an announcement of a interpreted as an announcement of "DOIC supported capabilities". The
"capability". The overload report and the capability information in OC-Supported-Features AVP in the answer is also interpreted as a
the answer is always interpreted as a report of supported commond report of "DOIC supported capabilities" and at least one of supported
functionality and as a status report of an overload condition (of a capabilities MUST be common with the "Reacting node" (see
node). Section 4.1).
3.3. Overload Condition Indication 3.3. Overload Condition Indication
Diameter nodes can request a reduction in offered load by indicating Diameter nodes can request a reduction in offered load by indicating
an overload condition in the form of an overload report. The an overload condition in the form of an overload report. The
overload report contains information about how much load should be overload report contains information about how much load should be
reduced, and may contain other information about the overload reduced, and may contain other information about the overload
condition. This information is encoded in Diameter Attribute Value condition. This information is conveyed in Diameter Attribute Value
Pairs (AVPs). Pairs (AVPs).
Certain new AVPs may also be used to declare certain DOIC Certain new AVPs may also be used to declare certain DOIC
capabilities and extensions. capabilities and extensions.
4. Attribute Value Pairs 4. Attribute Value Pairs
This section describes the encoding and semantics of Overload This section describes the encoding and semantics of the Diameter
Indication Attribute Value Pairs (AVPs). Overload Indication Attribute Value Pairs (AVPs) defined in this
document.
4.1. OC-Feature-Vector AVP 4.1. OC-Supported-Features AVP
The OC-Feature-Vector AVP (AVP code TBD1) is type of Unsigned64 and The OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and
contains a 64 bit flags field of announced capabilities of an serves for two purposes. First, it announces node's support for the
overload control endpoint. Sending or receiving the OC-Feature- DOIC in general. Second, it contains the description of the
Vector AVP with the value 0 indicates that the endpoint only support supported DOIC features of the sending node. The OC-Supported-
the capabilities defined in this specification. Features AVP SHOULD be included into every Diameter message a DOIC
supporting node sends (and intends to use for DOIC purposes).
An overload control endpoint (a reacting node) includes this AVP to OC-Supported-Features ::= < AVP Header: TBD1 >
indicate its capabilities to the other overload control endpoint (the < OC-Sequence-Number >
reporting node). For example, the endpoint (reacting node) may [ OC-Feature-Vector ]
* [ AVP ]
The OC-Sequence-Number AVP is used to indicate whether the contents
of the OC-Supported-Features AVP has changed since last time the node
included the OC-Supported-Features AVP (see Section 4.4). Although
sending the OC-Sequence-Number AVP is mandatory in the OC-Supported-
Features AVP, the receiving node MAY always choose to ignore the
sequence number if it can determine the feature support changes
otherwise.
The OC-Feature-Vector sub-AVP is used to announced the DOIC features
supported by the endpoint, in the form of a flag bits field in which
each bit announces one feature or capability supported by the node
(see Section 4.2). The absence of the OC-Feature-Vector AVP
indicates that only the default traffic abatement algorithm described
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 indicate which (future defined) traffic abatement algorithms it
supports in addition to the default. supports in addition to the default.
During the message exchange the overload control endpoints express During the message exchange the overload control endpoints express
their common set of supported capabilities. The endpoint sending a their common set of supported capabilities. The reacting node
request (the reacting node) includes the OC-Feature-Vector AVP with includes the OC-Supported-Features AVP that announces what it
those flags set that correspond what it supports. The endpoint that supports. The reporting node that sends the answer also includes the
sends the answer (the reporting node) also includes the OC-Feature- OC-Supported-Features AVP that describes the capabilities it
Vector AVP with flags set to describe the capabilities it both supports. The set of capabilities advertised by the reporting node
supports and agrees with the request sender (e.g., based on the local depends on local policies. At least one of the announced
policy and/or configuration). The answer sending endpoint (the capabilities MUST match mutually. If there is no single matching
reporting node) does not need to advertise those capabilities it is capability the reacting node MUST act as if it does not implement
not going to use with the request sending endpoint (the reacting DOIC and cease inserting any DOIC related AVPs into any Diameter
node). messages with this specific reacting node.
This specification does not define any additional capability flag. 4.2. OC-Feature-Vector AVP
The implicity capability (all flags set to zero) indicates the
support for this specification only.
4.2. OC-OLR AVP The OC-Feature-Vector AVP (AVP code TBD6) is type of Unsigned64 and
contains a 64 bit flags field of announced capabilities of an
overload control endpoint. The value of zero (0) is reserved.
The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the The following capabilities are defined in this document:
necessary information to convey an overload report. OC-OLR may also
be used to convey additional information about an extension that is
declared in the OC-Feature-Vector AVP.
The OC-OLR AVP does not contain explicit information to which OLR_DEFAULT_ALGO (0x0000000000000001)
application it applies to and who inserted the AVP or whom the
specific OC-OLR AVP concerns to. Both these information is When this flag is set by the overload control endpoint it means
implicitly learned from the encapsulating Diameter message/command. that the default traffic abatement (loss) algorithm is supported.
The application the OC-OLR AVP applies to is the same as the
Application-Id found in the Diameter message header. The identity 4.3. OC-OLR AVP
the OC-OLR AVP concerns is determined from the Origin-Host AVP found
from the encapsulating Diameter command. 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
does not contain explicit information to which application it applies
to and who inserted the AVP or whom the specific OC-OLR AVP concerns
to. Both these information is implicitly learned from the
encapsulating Diameter message/command. The application the OC-OLR
AVP applies to is the same as the Application-Id found in the
Diameter message header. The identity the OC-OLR AVP concerns is
determined from the Origin-Host AVP (and Origin-Realm AVP as well)
found from 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 >
< TimeStamp > < OC-Sequence-Number >
[ Reduction-Percentage ] [ OC-Report-Type ]
[ ValidityDuration ] [ OC-Reduction-Percentage ]
[ ReportType ] [ OC-Validity-Duration ]
* [ AVP ] * [ AVP ]
The TimeStamp AVP indicates when the original OC-OLR AVP with the The Sequence-Number AVP indicates the "freshness" of the OC-OLR AVP.
current content was created. It is possible to replay the same OC- It is possible to replay the same OC-OLR AVP multiple times between
OLR AVP multiple times between the overload endpoints, however, when the overload control endpoints, however, when the OC-OLR AVP content
the OC-OLR AVP content changes or the other information sending changes or sending endpoint otherwise wants the receiving endpoint to
endpoint wants the receiving endpoint to update its overload control update its overload control information, then the OC-Sequence-Number
information, then the TimeStamp AVP MUST contain a new value. AVP MUST contain a new greater value than the previously received.
The receiver SHOULD discard an OC-OLR AVP with a sequence number that
is less than previously received one.
[OpenIssue: Is this necessarily a timestamp, or is it just a sequence Note that if a Diameter command were to contain multiple OC-OLR AVPs
number that can be implemented as a timestamp? Is this timestamp they all MUST have different OC-Report-Type AVP value. OC-OLR AVPs
used to calculate expiration time? (propose no.). We should also with unknown values SHOULD be silently discarded and the event SHOULD
consider whether either a timestamp or sequence number is needed for be logged.
protection against replay attacks.]
4.3. TimeStamp AVP The OC-OLR AVP can be expanded with optional sub-AVPs only if a
legacy implementation can safely ignore them without breaking
backward compatibility for the given OC-Report-Type AVP value implied
report handling semantics. If the new sub-AVPs imply new semantics
for the report handling, then a new OC-Report-Type AVP value MUST be
defined.
The TimeStamp AVP (AVP code TBD3) is type of Time. Its usage in the 4.4. OC-Sequence-Number AVP
context of the overload control is described in Section 4.2. From
the functionality point of view, the TimeStamp AVP is merely used as
a non-volatile increasing counter between two overload control
endpoints.
4.4. ValidityDuration AVP The OC-Sequence-Number AVP (AVP code TBD3) is type of Time. Its
usage in the context of the overload control is described in Sections
4.1 and 4.3.
The ValidityDuration AVP (AVP code TBD4) is type of Unsigned32 and From the functionality point of view, the OC-Sequence-Number AVP MUST
describes the number of seconds the OC-OLR AVP and its content is be used as a non-volatile increasing counter between two overload
valid since the creation of the OC-OLR AVP (as indicated by the control endpoints (neglecting the fact that the contents of the AVP
TimeStamp AVP). is a 64-bit NTP timestamp [RFC5905]). The sequence number is only
required to be unique between two overload control endpoints.
Sequence numbers are treated in uni-directional manner, i.e. two
sequence numbers on each direction between two endpoints are not
related or correlated.
When generating sequence numbers, the new sequence number MUST be
greater than any sequence number previously seen between two
endpoints within a time window that tolerates the wraparound of the
NTP timestamp (i.e. approximately 68 years).
4.5. OC-Validity-Duration AVP
The OC-Validity-Duration AVP (AVP code TBD4) is type of Unsigned32
and describes the number of seconds the "new and fresh" OC-OLR AVP
and its content is valid since the reception of the new OC-OLR AVP.
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. Validity duration values 0
(i.e., 0 seconds) and above 86400 (i.e., 24 hours) MUST NOT be used.
Invalid validity duration values are treated as if the OC-Validity-
Duration AVP were not present.
A timeout of the overload report has specific concerns that need to A timeout of the overload report has specific concerns that need to
be taken into account by the endpoint acting on the earlier received be taken into account by the endpoint acting on the earlier received
overload report(s). Section 4.6 discusses the impacts of timeout in overload report(s). Section 4.7 discusses the impacts of timeout in
the scope of the traffic abatement algorithms. the scope of the traffic abatement algorithms.
As a general guidance for implementations it is RECOMMENDED never to As a general guidance for implementations it is RECOMMENDED never to
let any overload report to timeout. Rather, an overload endpoint let any overload report to timeout. Following to this rule, an
should explicitly signal, e.g. the end of overload condition. This overload endpoint should explicitly signal the end of overload
leaves no need for the other overload endpoint to reason or guess the condition and not rely on the expiration of the validity time of the
condition the other endpoint is at. overload report in the reacting node. This leaves no need for the
reacting node to reason or guess the overload condition of the
reporting node.
4.5. ReportType AVP 4.6. OC-Report-Type AVP
The ReportType AVP (AVP code TBD5) is type of Enumerated. The value The OC-Report-Type AVP (AVP code TBD5) is type of Enumerated. The
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 Reserved. 0 A host report. The overload treatment should apply to requests
the reacting node knows that will reach the overloaded node. For
example, requests with a Destination-Host AVP indicating the
endpoint. The reacting node learns the "host" implicitly from the
Origin-Host AVP of the received message that contained the OC-OLR
AVP.
1 Destination-Host report. The overload treatment should apply to 1 A realm report. The overload treatment should apply to all
requests that the sender knows will reach the overloaded server. requests bound for the overloaded realm. The reacting node learns
For example, requests with a Destination-Host AVP indicating the the "realm" implicitly from the Origin-Realm AVP of the received
server. message that contained the OC-OLR AVP.
2 Realm (aggregated) report. The overload treatment should apply to The default value of the OC-Report-Type AVP is 0 (i.e. the host
all requests bound for the overloaded realm. report).
The ReportType AVP is envisioned to be useful for situations where a The OC-Report-Type AVP is envisioned to be useful for situations
reacting node needs to apply different overload treatments for where a reacting node needs to apply different overload treatments
different "types" of overload. For example, the reacting node(s) for different "types" of overload. For example, the reacting node(s)
might need to throttle requests that are targeted to a specific might need to throttle differently requests sent to a specific server
server by the presence of a Destination-Host AVP than for 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. The example in
Appendix C.3 illustrates this usage. Appendix B.1 illustrates this usage.
[OpenIssue: There is an ongoing discussion about whether the When defining new report type values, the corresponding specification
ReportType AVP is the right way to solve that issue, and whether it's MUST define the semantics of the new report types and how they affect
needed at all.] the OC-OLR AVP handling. The specification MUST also reserve a
corresponding new feature, see the OC-Supported-Features and OC-
Feature-Vector AVPs.
4.6. Reduction-Percentage AVP 4.7. OC-Reduction-Percentage AVP
The 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 have sent. requested to reduce, compared to what it otherwise would have sent.
The OC-Reduction-Percentage AVP applies to the default (loss like)
algorithm specified in this specification. However, the AVP can be
reused for future abatement algorithms, if its semantics fit into the
new 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 interpreted as 100. The hundred (100). Values greater than 100 are interpreted as 100. The
value of 100 means that no traffic is expected, i.e. the sender of value of 100 means that no traffic is expected, i.e. the reporting
the information is under a severe load and ceases to process any new node is under a severe load and ceases to process any new messages.
messages. The value of 0 means that the sender of the information is The value of 0 means that the reporting node is in a stable state and
in a stable state and has no requests to the other endpoint to apply has no requests to the other endpoint to apply any traffic abatement.
any traffic abatement. The default value of the OC-Reduction-Percentage AVP is 0. When the
OC-Reduction-Percentage AVP is not present in the overload report,
[Open Issue: We should consider an algorithm independent way to end the default value applies.
an overload condition. Perhaps setting the validitytime to zero?
Counter comment; since the abatement is based on a specific
algorithm, it is natural to indicate that from the abatement
algorithm point of view status quo has been reached.]
If an overload control endpoint comes out of the 100 percent traffic If an overload control endpoint comes out of the 100 percent traffic
reduction as a result of the overload report timing out, the reduction as a result of the overload report timing out, the
following concerns are RECOMMENDED to be applied. The endpoint following concerns are RECOMMENDED to be applied. The reacting node
sending the traffic should be conservative and, for example, first sending the traffic should be conservative and, for example, first
send few "probe" messages to learn the overload condition of the send "probe" messages to learn the overload condition of the
other endpoint before converging to any traffic amount/rate decided overloaded node before converging to any traffic amount/rate decided
by the sender. Similar concerns actually apply in all cases when the by the sender. Similar concerns apply in all cases when the overload
overload report times out unless the previous overload report stated report times out unless the previous overload report stated 0 percent
0 percent reduction. reduction.
[Open Issue: It is still open whether we need an AVP to indicate the
exact used traffic abatement algorithm. Currently it assumed that
the reacting node is able to figure out what to do based on the
Reducttion-Percentage AVP and possible other embedded information
inside the OC-OLR AVP.]
4.7. Attribute Value Pair flag rules 4.8. 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-Feature-Vector TBD1 x.x Unsigned64 | | V | |OC-Supported-Features TBD1 x.x Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-OLR TBD2 x.x Grouped | | V | |OC-OLR TBD2 x.x Grouped | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|TimeStamp TBD3 x.x Time | | V | |OC-Sequence-Number TBD3 x.x Time | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|ValidityPeriod TBD4 x.x Unsigned32 | | V | |OC-Validity-Duration TBD4 x.x Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|ReportType TBD5 x.x Enumerated | | V | |OC-Report-Type TBD5 x.x Enumerated | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|Reduction | | | |OC-Reduction | | |
| -Percentage TBD8 x.x Unsigned32 | | V | | -Percentage TBD8 x.x Unsigned32 | | V |
+--------------------------------------------------+----+----+ +--------------------------------------------------+----+----+
|OC-Feature-Vector TBD6 x.x Unsigned64 | | V |
+--------------------------------------------------+----+----+
As described in the Diameter base protocol [RFC6733], the M-bit
setting for a given AVP is relevant to an application and each
command within that application that includes the AVP.
The Diameter overload control AVPs SHOULD always be sent with the
M-bit cleared when used within existing Diameter applications to
avoid backward compatibility issues. Otherwise, when reused in newly
defined Diameter applications, the DOC related AVPs SHOULD have the
M-bit set.
5. Overload Control Operation 5. Overload Control Operation
5.1. Overload Control Endpoints 5.1. Overload Control Endpoints
The overload control solution can be considered as an overlay on top The overload control solution can be considered as an overlay on top
of an arbitrary Diameter network. The overload control information of an arbitrary Diameter network. The overload control information
is exchanged over on a "DOIC association" between two communicatin is exchanged over on a "DOIC association" established between two
endpoints. The endpoints, namely the "reacting node" and the communication endpoints. The endpoints, namely the "reacting node"
"reporting node" do not need to be adjacent Diameter peer nodes, nor and the "reporting node" do not need to be adjacent Diameter peer
they need to be the end-to-end Diameter nodes in a typical "client- nodes, nor they need to be the end-to-end Diameter nodes in a typical
server" deployment with multiple intermediate Diameter agent nodes in "client-server" deployment with multiple intermediate Diameter agent
between. The overload control endpoint are the two Diameter nodes nodes in between. The overload control endpoints are the two
that decide to exchange overload control information between each Diameter nodes that decide to exchange overload control information
other. How the endpoints are determined is specific to a deployment, between each other. How the endpoints are determined is specific to
a Diameter node role in that deployment and local configuration. a deployment, a Diameter node role in that deployment and local
configuration.
The following diagrams illustrate the concept of Diameter Overload The following diagrams illustrate the concept of Diameter Overload
End-Points and how they differ from the standard [RFC6733] defined End-Points and how they differ from the standard [RFC6733] defined
client, server and agent Diameter nodes. The following is the key to client, server and agent Diameter nodes. The following is the key to
the elements in the diagrams: the elements in the diagrams:
C Diameter client as defined in [RFC6733]. C Diameter client as defined in [RFC6733].
S Diameter server as defined in [RFC6733]. S Diameter server as defined in [RFC6733].
skipping to change at page 20, line 23 skipping to change at page 19, line 6
following figures a DEP may terminate two different DOIC following figures a DEP may terminate two different DOIC
associations being a reporter and reactor at the same time. associations being a reporter and reactor at the same time.
Diameter Session A Diameter session as defined in [RFC6733]. Diameter Session A Diameter session as defined in [RFC6733].
DOIC Association A DOIC association exists between two Diameter DOIC Association A DOIC association exists between two Diameter
Overload End-Points. One of the end-points is the overload Overload End-Points. One of the end-points is the overload
reporter and the other is the overload reactor. reporter and the other is the overload reactor.
Figure 2 illustrates the most basic configuration where a client is Figure 2 illustrates the most basic configuration where a client is
connected directly to a server. In this case, the session and connected directly to a server. In this case, the Diameter session
association are both between the client and server. and the DOIC association are both between the client and server.
+-----+ +-----+ +-----+ +-----+
| C | | S | | C | | S |
+-----+ +-----+ +-----+ +-----+
| DEP | | DEP | | DEP | | DEP |
+--+--+ +--+--+ +--+--+ +--+--+
| | | |
| | | |
|{Diameter Session}| |{Diameter Session}|
| | | |
|{DOIC Association}| |{DOIC Association}|
| | | |
Figure 2: Basic DOIC deployment Figure 2: Basic DOIC deployment
In Figure 3 there is an agent that is not participating directly in In Figure 3 there is an agent that is not participating directly in
the exchange of overload reports. As a result, the DOIC association the exchange of overload reports. As a result, the Diameter session
is still between the client and the server. and the DOIC association are still established between the client and
the server.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| C | | A | | S | | C | | A | | S |
+-----+ +--+--+ +-----+ +-----+ +--+--+ +-----+
| DEP | | | DEP | | DEP | | | DEP |
+--+--+ | +--+--+ +--+--+ | +--+--+
| | | | | |
| | | | | |
|----------{Diameter Session}---------| |----------{Diameter Session}---------|
| | | | | |
skipping to change at page 21, line 41 skipping to change at page 20, line 22
|----------{Diameter Session}---------| |----------{Diameter Session}---------|
| | | | | |
| |{DOIC Association}| | |{DOIC Association}|
| | | | | |
Figure 4: DOIC deployment with non-DOIC client and DOIC enabled agent Figure 4: DOIC deployment with non-DOIC client and DOIC enabled agent
In Figure 5 there is a DOIC association between the client and the In Figure 5 there is a DOIC association between the client and the
agent and a second DOIC association between the agent and the server. agent and a second DOIC association between the agent and the server.
One use case requiring this configuration is when the agent is One use case requiring this configuration is when the agent is
serving as a SFE/SFIM for a set of servers. serving as a SFE for a set of servers.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| C | | A | | S | | C | | A | | S |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| DEP | | DEP | | DEP | | DEP | | DEP | | DEP |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
| | | | | |
| | | | | |
|----------{Diameter Session}---------| |----------{Diameter Session}---------|
| | | | | |
|{DOIC Association}|{DOIC Association}| |{DOIC Association}|{DOIC Association}|
| | and/or
|----------{DOIC Association}---------|
| | | | | |
Figure 5: A deployment where all nodes support DOIC Figure 5: A deployment where all nodes support DOIC
Figure 6 illustrates a deployment where some clients support Diameter Figure 6 illustrates a deployment where some clients support Diameter
overload control and some do not. In this case the agent must overload control and some do not. In this case the agent must
support Diameter overload control for the non supporting client. It support Diameter overload control for the non supporting client. It
might also need to have a DOIC association with the server, as shown 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 here, to handle overload for a server farm and/or for managing Realm
overload. overload.
skipping to change at page 22, line 38 skipping to change at page 21, line 17
+-----+ +--+--+ +-----+ +-----+ +-----+ +--+--+ +-----+ +-----+
| DEP | | | DEP | | DEP | | DEP | | | DEP | | DEP |
+--+--+ | +--+--+ +--+--+ +--+--+ | +--+--+ +--+--+
| | | | | | | |
| | | | | | | |
|-------------------{Diameter Session}-------------------| |-------------------{Diameter Session}-------------------|
| | | | | | | |
| |--------{Diameter Session}-----------| | |--------{Diameter Session}-----------|
| | | | | | | |
|---------{DOIC Association}----------|{DOIC Association}| |---------{DOIC Association}----------|{DOIC Association}|
| | | and/or
|-------------------{DOIC Association}-------------------|
| | | | | | | |
Figure 6: A deployment with DOIC and non-DOIC supporting clients Figure 6: A deployment with DOIC and non-DOIC supporting clients
Figure 7 illustrates a deployment where some agents support Diameter Figure 7 illustrates a deployment where some agents support Diameter
overload control and others do not. overload control and others do not.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| C | | A | | A | | S | | C | | A | | A | | S |
+-----+ +--+--+ +-----+ +-----+ +-----+ +--+--+ +-----+ +-----+
| DEP | | | DEP | | DEP | | DEP | | | DEP | | DEP |
+--+--+ | +--+--+ +--+--+ +--+--+ | +--+--+ +--+--+
| | | | | | | |
| | | | | | | |
|-------------------{Diameter Session}-------------------| |-------------------{Diameter Session}-------------------|
| | | | | | | |
| | | | | | | |
|---------{DOIC Association}----------|{DOIC Association}| |---------{DOIC Association}----------|{DOIC Association}|
| | | and/or
|-------------------{DOIC Association}-------------------|
| | | | | | | |
Figure 7: A deployment with DOIC and non-DOIC supporting agents Figure 7: A deployment with DOIC and non-DOIC supporting agents
5.2. Piggybacking Principle 5.2. Piggybacking Principle
The overload control solution defined AVPs are essentially The overload control AVPs defined in this specification have been
piggybacked on top of existing application message exchanges. This designed to be piggybacked on top of existing application message
is made possible by adding overload control top level AVPs, the OC- exchanges. This is made possible by adding overload control top
OLR AVP and the OC-Feature-Vector AVP into existing commands (this level AVPs, the OC-OLR AVP and the OC-Supported-Features AVP as
has an assumption that the application CCF allows adding new AVPs optional AVPs into existing commands when the corresponding Command
into the Diameter messages. Code Format (CCF) specification allows adding new optional AVPs (see
Section 1.3.4 of [RFC6733]).
In a case of newly defined Diameter applications, it is RECOMMENDED When added to existing commands, both OC-Feature-Vector and OC-OLR
to add and defined how overload control mechanisms works on that AVPs SHOULD have the M-bit flag cleared to avoid backward
application. using OC-Feature-Vector and OC-OLR AVPs in a non- compatibility issues.
mandatory manner is intended only existing applications.
A new application specification can incorporate the overload control
mechanism specified in this document by making it mandatory to
implement for the application and referencing this specification
normatively. In such a case, the OC-Feature-Vector and OC-OLR AVPs
reused in newly defined Diameter applications SHOULD have the M-bit
flag set. However, it is the responsibility of the Diameter
application designers to define how overload control mechanisms works
on that application.
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 sent and client roles. The endpoint 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 "client" MAY
report its overload condition to the "server" for any server report its overload condition to the "server" for any server
initiated message exchange. An example of such is the server initiated message exchange. An example of such is the server
requesting a re-authentication from a client. requesting a re-authentication from a client.
5.3. Capability Announcement 5.3. Capability Announcement
Since the overload control solution relies on the piggybacking Since the overload control solution relies on the piggybacking
principle for the overload reporting and the overload control principle for the overload reporting and the overload control
endpoint are likely not adjacent peers, finding out whether the other endpoint are likely not adjacent peers, finding out whether the other
endpoint supports the overload control or what is the common traffic endpoint supports the overload control or what is the common traffic
abatement algorithm to apply for the traffic. The approach defined abatement algorithm to apply for the traffic. The approach defined
in this specification for the end-to-end capability capability in this specification for the end-to-end capability announcement
announcement relies on the exchange of the OC-Feature-Vector between relies on the exchange of the OC-Supported-Features between the
the endpoints. The feature announcement solution also works when endpoints. The feature announcement solution also works when carried
carried out on existing applications. For the newly defined out on existing applications. For the newly defined application the
application the negotiation can be more exact based on the negotiation can be more exact based on the application specification.
application specification. The announced set of capabilities MUST The announced set of capabilities MUST NOT change during the life
NOT change during the life time of the Diameter session (or time of the Diameter session (or transaction in case of non-session
transaction in a case of non-session maintaining applications). maintaining applications).
5.3.1. Request Message Initiator Endpoint Considerations 5.3.1. Reacting Node Endpoint Considerations
The basic principle is that the request message initiating endpoint The basic principle is that the request message initiating endpoint
(i.e. the "reacting node") announces its support for the overload (i.e. the "reacting node") announces its support for the overload
control mechanism by including in the request message the OC-Feature- control mechanism by including in the request message the OC-
Vector AVP with those capability flag bits set that it supports and Supported-Features AVP with those capabilities it supports and is
is willing to use for this Diameter session (or transaction in a case willing to use for this Diameter session (or transaction in a case of
of a non-session state maintaining applications). In a case of a non-session state maintaining applications, see Section 3.1.2 for
session maintaining applications the request message initiating more details on Diameter sessions). It is RECOMMENDED that the
endpoint does not need to do the capability announcement more than request message initiating endpoint includes the capability
once for the lifetime of the Diameter session. In a case of non- announcement into every request regardless it has had prior message
session maintaining applications, it is RECOMMENDED that the request exchanges with the give remote endpoint. In a case of a Diameter
message initiating endpoint includes the capability announcement into session maintaining application, sending the OC-Supported-Features
every request regardless it has had prior message exchanges with the AVP in every message is not really necessary after the initial
give remote endpoint. capability announcement or until there is a change in supported
features.
[OpenIssue: We need to think about the lifetime of a capabilities
declaration. It's probably not the same as for a session. We have
had proposals that the feature vector needs to go into every request
sent by an OC node. For peer to peer cases, this can be associated
with connection lifetime, but it's more complex for non-adjacent OC
support.]
Once the endpoint that initiated the request message receives an Once the endpoint that initiated the request message receives an
answer message from the remote endpoint, it can detect from the answer message from the remote endpoint, it can detect from the
received answer message whether the remote endpoint supports the received answer message whether the remote endpoint supports the
overload control solution and in a case it does, what features are overload control solution and in a case it does, what features are
supported. The support for the overload control solution is based on supported. The support for the overload control solution is based on
the presence of the OC-Feature-Vector AVP in the Diameter answer for the presence of the OC-Supported-Features AVP in the Diameter answer
existing application. For the newly defined applications the support for existing application.
for the overload control MAY already be part of the application
specification. Based on capability knowledge the request message
initiating endpoint can select the preferred common traffic abatement
algorithm and act accordingly for the subsequent message exchanges.
5.3.2. Answer Message Initiating Endpoint Considerations 5.3.2. Reporting Node Endpoint Considerations
When a remote endpoint (i.e. a "reporting node") receives a request When a remote endpoint (i.e. a "reporting node") receives a request
message in can detect whether the request message initiating endpoint message, it can detect whether the request message initiating
has support for the overload control solution based on the presence endpoint supports the overload control solution based on the presence
of the OC-Feature-Vector AVP. For the newly defined applications the of the OC-Supported-Features AVP. For the newly defined applications
overload control solution support can be part of the application the overload control solution support can be part of the application
specification. Based on the content of the OC-Feature-Vector AVP the specification. Based on the content of the OC-Supported-Features AVP
request message receiving endpoint knows what overload control the request message receiving endpoint knows what overload control
functionality the other endpoint supports and then act accordingly functionality the other endpoint supports and then act accordingly
for the subsequent answer messages it initiates. It is RECOMMENDED for the subsequent answer messages it initiates. The answer message
that the answer message initiating endpoint selects one common initiating endpoint MAY announce as many supported capabilities as it
traffic abatement algorithm even if it would support multiple. The has (the announced set is a subject to local policy and
answer message initiating endpoint MUST NOT include any overload configuration). However, at least one of the announced capabilities
MUST be the same as received in the request message.
The answer message initiating endpoint MUST NOT include any overload
control solution defined AVPs into its answer messages if the request control solution defined AVPs into its answer messages if the request
message initiating endpoint has not indicated support at the message initiating endpoint has not indicated support at the
beginning of the the created session (or transaction in a case of beginning of the created session (or transaction in a case of non-
non-session state maintaining applications). session state maintaining applications). The same also applies if
none of the announced capabilities match between the two endpoints.
5.4. Protocol Extensibility 5.4. Protocol Extensibility
The overload control solution can be extended, e.g. with new traffic The overload control solution can be extended, e.g. with new traffic
abatement algorithms or new functionality. The new features and abatement algorithms or new functionality. The new features and
algorithms MUST be registered with the IANA and for the ppossible use algorithms MUST be registered with the IANA and for the possible use
with the OC-Feature-Vector for announcing the support for the new with the OC-Supported-Features for announcing the support for the new
features (see Section 7 for the required procedures). features (see Section 7 for the required procedures).
It should be noted that [RFC6733] defined Grouped AVP extension It should be noted that [RFC6733] defined Grouped AVP extension
mechanisms also apply. This allows, for example, defining a new mechanisms also apply. This allows, for example, defining a new
feature that is mandatory to understand even when piggybacked on an feature that is mandatory to understand even when piggybacked on an
existing applications. More specifically, the sub-AVPs inside the existing applications. More specifically, the sub-AVPs inside the
OC-OLR AVP MAY have the M-bit set. However, when overload control OC-OLR AVP MAY have the M-bit set. However, when overload control
AVPs are piggybacked on top of an existing applications, setting AVPs are piggybacked on top of an existing applications, setting
M-bit in sub-AVPs is NOT RECOMMENDED. M-bit in sub-AVPs is NOT RECOMMENDED.
5.5. Overload Report Processing 5.5. Overload Report Processing
5.5.1. Sender Endpoint Considerations 5.5.1. Overload Control State
5.5.2. Receiver Endpoint Considerations Both reacting and reporting nodes maintain an overload condition
state for each endpoint (a host or a realm) they communicate with and
both endpoints have announced support for DOIC. See Sections 4.1 and
5.3 for discussion about how the support for DOIC is determined. The
overload condition state SHOULD be able to make a difference between
a realm and a specific host in that realm.
[OpenIssue: did we now agree that e.g. a server can refrain sending The overload condition state could include the following information
OLR in answers based on some magical algorithm? (Note: We seem to (per host or realm):
have consensus that a server MAY repeat OLRs in subsequent messages,
but is not required to do so, based on local policy.)] o The endpoint information (Diameter identity of the realm and/or
host, application identifier, etc)
o Reduction percentage
o Validity period timer
o Sequence number
o Supported/selected traffic abatement algorithm
The overload control state information SHOULD be maintained as long
as the other endpoint is known to support DOIC (based on the presence
of the DOIC AVPs or by a future application specification).
5.5.2. Reacting Node Considerations
Once a reacting node receives an OC-OLR AVP from a reporting node, it
applies the traffic abatement based on the commonly supported
algorithm with the reporting node and the current overload condition.
The reacting node learns the reporting node supported abatement
algorithms directly from the received answer message containing the
OC-Supported-Features AVP or indirectly remembering the previously
used traffic abatement algorithm with the given reporting node.
The received OC-Supported-Features AVP does not change the existing
overload condition and/or traffic abatement algorithm settings if the
OC-Sequence-Number AVP contains a value that is equal to the
previously received/recorded one. 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 one (and is outside the valid overflow window), then either
the sequence number is stale (e.g. an intentional or unintentional
replay) and SHOULD be silently discarded.
The OC-OLR AVP contains the necessary information of the overload
condition on the reporting node. Similarly to the OC-Supported-
Features's sequence numbering, the OC-OLR AVP also has the OC-
Sequence-Number AVP and its handling is similar to the one in the OC-
Supported-Features AVP. The reacting node MUST update its overload
condition state whenever receiving the OC-OLR AVP for the first time
or the OC-Sequence-Number sub-AVP indicates a change in the OC-OLR
AVP.
As described in Section 4.3, the OC-OLR AVP contains the necessary
information of the overload condition on the reporting node.
From the OC-Report-Type AVP contained in the OC-OLR AVP, the reacting
node learns whether the overload condition report concerns a specific
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.
In the context of this specification and the default traffic
abatement algorithm, the OC-Reduction-Percentage AVP value MUST be
interpreted in the following way:
value == 0
Indicates explicitly the end of overload condition and the
reacting node SHOULD NOT apply the traffic abatement algorithm
procedures anymore for the given reporting node (or realm).
value == 100
Indicates that the reporting node (or realm) does not want to
receive any traffic from the reacting node for the application the
report concerns. The reacting node MUST do all measure not to
send traffic to the reporting node (or realm) as long as the
overload condition changes or expires.
0 < value < 100
Indicates that the reporting node urges the reacting node to
reduce its traffic by a given percentage. For example if the
reacting node has been sending 100 packets per second to the
reporting node, then a reception of OC-Reduction-Percentage value
of 10 would mean that from now on the reacting node MUST only send
90 packets per second. How the reacting node achieves the "true
reduction" transactions leading to the sent request messages is up
to the implementation. The reacting node MAY simply drop every
10th packet from its output queue and let the generic application
logic try to recover from it.
If the OC-OLR AVP is received for the first time, the reacting node
MUST create an overload condition state associated with the related
realm or a specific host in the realm identified in the message
carrying the OC-OLR AVP, as described in Section 5.5.1.
If the value of the OC-Sequence-Number AVP contained in the received
OC-OLR AVP is equal to or less than the value stored in an existing
overload condition state, the received OC-OLR AVP SHOULD be silently
discarded. If the value of the OC-Sequence-Number AVP contained in
the received OC-OLR AVP is greater than the value stored in an
existing overload condition state or there is no previously recorded
sequence number, the reacting node MUST update the overload condition
state associated with the realm or the specific node is the realm.
When an overload condition state is created or updated, the reacting
node MUST apply the traffic abatement requested in the OC-OLR AVP
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
OC-OLR AVP is either explicitly indicated in the OC-Validity-Duration
AVP or is implicitly equals to the default value (5 seconds) if the
OC-Validity-Duration AVP is absent of the OC-OLR AVP. The reacting
node MUST maintain the validity duration in the overload condition
state. Once the validity duration times out, the reacting node MUST
assume the overload condition reported in a previous OC-OLR AVP has
ended.
5.5.3. Reporting Node Considerations
A reporting node is a Diameter node inserting an OC-OLR AVP in a
Diameter message in order to inform a reacting node about an overload
condition and request Diameter traffic abatement.
The operation on the reporting node is rather straight forward. The
reporting node learns the capabilities of the reacting node when it
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 5.3 for further discussion on the
capability and feature announcement between two endpoints.
When a traffic reduction is required due to an overload condition and
the overload control solution is supported by the sender of the
Diameter request, the reporting node MUST include an OC-Supported-
Features AVP and an OC-OLR AVP in the corresponding Diameter answer.
The OC-OLR AVP contains the required traffic reduction and the OC-
Supported-Features AVP indicates the traffic abatement algorithm to
apply. This algorithm MUST be one of the algorithms advertised by
the request sender.
A reporting node MAY rely on the OC-Validity-Duration AVP values for
the implicit overload condition state cleanup on the reacting node.
However, it is RECOMMENDED that the reporting node always explicitly
indicates the end of a overload condition.
6. Transport Considerations 6. Transport Considerations
In order to reduce overload control introduced additional AVP and In order to reduce overload control introduced additional AVP and
message processing it might be desirable/beneficial to signal whether message processing it might be desirable/beneficial to signal whether
the Diameter command carries overload control information that should the Diameter command carries overload control information that should
be of interest of an overload aware Diameter node. be of interest of an overload aware Diameter node.
Should such indication be include is not part of this specification. Should such indication be include is not part of this specification.
It has not either been concluded at what layer such possible It has not either been concluded at what layer such possible
skipping to change at page 26, line 24 skipping to change at page 28, line 18
New AVPs defined by this specification are listed in Section 4. All New AVPs defined by this specification are listed in Section 4. 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.
7.2. New registries 7.2. New registries
Three new registries are needed under the 'Authentication, Three new registries are needed under the 'Authentication,
Authorization, and Accounting (AAA) Parameters' registry. Authorization, and Accounting (AAA) Parameters' registry.
Section 4.1 defines a new "Overload Control Feature Vector" registry Section 4.2 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]. registry using the Specification Required policy [RFC5226]. See
Section 4.2 for the initial assignment in the registry.
Section 4.5 defines a new "Overload Report Type" registry with its Section 4.6 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].
8. Security Considerations 8. Security Considerations
This mechanism gives Diameter nodes the ability to request that This mechanism gives Diameter nodes the ability to request that
downstream nodes send fewer Diameter requests. Nodes do this by downstream nodes send fewer Diameter requests. Nodes do this by
exchanging overload reports that directly affect this reduction. exchanging overload reports that directly affect this reduction.
This exchange is potentially subject to multiple methods of attack, This exchange is potentially subject to multiple methods of attack,
and has the potential to be used as a Denial-of-Service (DoS) attack and has the potential to be used as a Denial-of-Service (DoS) attack
skipping to change at page 28, line 22 skipping to change at page 30, line 19
tempting vector for DoS tacks. Furthermore, since Diameter is almost tempting vector for DoS tacks. Furthermore, since Diameter is almost
always used in support of other protocols, a DoS attack on Diameter always used in support of other protocols, a DoS attack on Diameter
is likely to impact those protocols as well. Therefore, Diameter is likely to impact those protocols as well. Therefore, Diameter
nodes MUST NOT honor or forward overload reports from unauthorized or nodes MUST NOT honor or forward overload reports from unauthorized or
otherwise untrusted sources. otherwise untrusted sources.
8.3. Non-Compliant Nodes 8.3. Non-Compliant Nodes
When a Diameter node sends an overload report, it cannot assume that When a Diameter node sends an overload report, it cannot assume that
all nodes will comply. A non-compliant node might continue to send all nodes will comply. A non-compliant node might continue to send
requests with no reduction in load. Requirement 28 requests with no reduction in load. Requirement 28 [RFC7068]
[I-D.ietf-dime-overload-reqs] indicates that the overload control indicates that the overload control solution cannot assume that all
solution cannot assume that all Diameter nodes in a network are Diameter nodes in a network are necessarily trusted, and that
necessarily trusted, and that malicious nodes not be allowed to take malicious nodes not be allowed to take advantage of the overload
advantage of the overload control mechanism to get more than their control mechanism to get more than their fair share of service.
fair share of service.
In the absence of an overload control mechanism, Diameter nodes need In the absence of an overload control mechanism, Diameter nodes need
to implement strategies to protect themselves from floods of to implement strategies to protect themselves from floods of
requests, and to make sure that a disproportionate load from one requests, and to make sure that a disproportionate load from one
source does not prevent other sources from receiving service. For source does not prevent other sources from receiving service. For
example, a Diameter server might reject a certain percentage of example, a Diameter server might reject a certain percentage of
requests from sources that exceed certain limits. Overload control requests from sources that exceed certain limits. Overload control
can be thought of as an optimization for such strategies, where can be thought of as an optimization for such strategies, where
downstream nodes never send the excess requests in the first place. downstream nodes never send the excess requests in the first place.
However, the presence of an overload control mechanism does not However, the presence of an overload control mechanism does not
skipping to change at page 29, line 7 skipping to change at page 30, line 51
overload reports. Nodes must trust that their adjacent peers perform overload reports. Nodes must trust that their adjacent peers perform
proper checks on overload reports from their peers, and so on, proper checks on overload reports from their peers, and so on,
creating a transitive-trust requirement extending for potentially creating a transitive-trust requirement extending for potentially
long chains of nodes. Network operators must determine if this long chains of nodes. Network operators must determine if this
transitive trust requirement is acceptable for their deployments. transitive trust requirement is acceptable for their deployments.
Nodes supporting Diameter overload control MUST give operators the Nodes supporting Diameter overload control MUST give operators the
ability to select which peers are trusted to deliver overload ability to select which peers are trusted to deliver overload
reports, and whether they are trusted to forward overload reports reports, and whether they are trusted to forward overload reports
from non-adjacent nodes. from non-adjacent nodes.
[OpenIssue: This requires that a responding node be able to tell a
peer-generated OLR from one generated by a non-adjacent node. One
way of doing this would be to include the identity of the node that
generated the report as part of the OLR]
[OpenIssue: Do we need further language about what rules an agent
should apply before forwarding an OLR?]
The lack of end-to-end protection creates a tension between two
requirements from the overload control requirements document.
[I-D.ietf-dime-overload-reqs] Requirement 34 requires the ability
to send overload reports across intermediaries (i.e. agents) that
do not support overload control mechanism. Requirement 27 forbids
the mechanism from adding new vulnerabilities or increasing the
severity of existing ones. A non-supporting agent will most
likely forward overload reports without inspecting them or
applying any sort of validation or authorization. This makes the
transitive trust issue considerably more of a problem. Without
the ability to authenticate and integrity protect overload reports
across a non-supporting agent, the mechanism cannot comply with
both requirements.
[OpenIssue: What do we want to do about this? Req27 is a
normative MUST, while Req34 is "merely" a SHOULD. This would seem
to imply that 27 has to take precedent. Can we say that overload
reports MUST NOT be sent to and/or accepted from non-supporting
agents until such time we can use end-to-end security?]
The lack of end-to-end confidentiality protection means that any The lack of end-to-end confidentiality protection means that any
Diameter agent in the path of an overload report can view the Diameter agent in the path of an overload report can view the
contents of that report. In addition to the requirement to select contents of that report. In addition to the requirement to select
which peers are trusted to send overload reports, operators MUST be which peers are trusted to send overload reports, operators MUST be
able to select which peers are authorized to receive reports. A node able to select which peers are authorized to receive reports. A node
MUST not send an overload report to a peer not authorized to receive MUST not send an overload report to a peer not authorized to receive
it. Furthermore, an agent MUST remove any overload reports that it. Furthermore, an agent MUST remove any overload reports that
might have been inserted by other nodes before forwarding a Diameter might have been inserted by other nodes before forwarding a Diameter
message to a peer that is not authorized to receive overload reports. message to a peer that is not authorized to receive overload reports.
At the time of this writing, the DIME working group is studying At the time of this writing, the DIME working group is studying
requirements for adding end-to-end security requirements for adding end-to-end security
[I-D.ietf-dime-e2e-sec-req] features to Diameter. These features, [I-D.ietf-dime-e2e-sec-req] features to Diameter. These features,
when they become available, might make it easier to establish when they become available, might make it easier to establish trust
trust in non-adjacent nodes for overload control purposes. in non-adjacent nodes for overload control purposes. Readers should
Readers should be reminded, however, that the overload control be reminded, however, that the overload control mechanism encourages
mechanism encourages Diameter agents to modify AVPs in, or insert Diameter agents to modify AVPs in, or insert additional AVPs into,
additional AVPs into, existing messages that are originated by existing messages that are originated by other nodes. If end-to-end
other nodes. If end-to-end security is enabled, there is a risk security is enabled, there is a risk that such modification could
that such modification could violate integrity protection. The violate integrity protection. The details of using any future
details of using any future Diameter end-to-end security mechanism Diameter end-to-end security mechanism with overload control will
with overload control will require careful consideration, and are require careful consideration, and are beyond the scope of this
beyond the scope of this document. document.
9. Contributors 9. Contributors
The following people contributed substantial ideas, feedback, and The following people contributed substantial ideas, feedback, and
discussion to this document: discussion to this document:
o Eric McMurry o Eric McMurry
o Hannes Tschofenig o Hannes Tschofenig
o Ulrich Wiehe o Ulrich Wiehe
o Jean-Jacques Trottin o Jean-Jacques Trottin
o Lionel Morand
o Maria Cruz Bartolome o Maria Cruz Bartolome
o Martin Dolly o Martin Dolly
o Nirav Salot o Nirav Salot
o Susan Shishufeng o Susan Shishufeng
10. Acknowledgements 10. References
10.1. Normative References
...
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, [RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012. "Diameter Base Protocol", RFC 6733, October 2012.
11.2. Informative References 10.2. Informative References
[3GPP.23.203]
3GPP, "Policy and charging control architecture", 3GPP
TS 23.203 10.9.0, September 2013.
[3GPP.29.229]
3GPP, "Cx and Dx interfaces based on the Diameter
protocol; Protocol details", 3GPP TS 29.229 10.5.0,
March 2013.
[3GPP.29.272]
3GPP, "Evolved Packet System (EPS); Mobility Management
Entity (MME) and Serving GPRS Support Node (SGSN) related
interfaces based on Diameter protocol", 3GPP TS 29.272
10.8.0, June 2013.
[I-D.ietf-dime-e2e-sec-req] [I-D.ietf-dime-e2e-sec-req]
Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay, Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay,
"Diameter AVP Level Security: Scenarios and Requirements", "Diameter AVP Level Security: Scenarios and Requirements",
draft-ietf-dime-e2e-sec-req-00 (work in progress), draft-ietf-dime-e2e-sec-req-00 (work in progress),
September 2013. September 2013.
[I-D.ietf-dime-overload-reqs]
McMurry, E. and B. Campbell, "Diameter Overload Control
Requirements", draft-ietf-dime-overload-reqs-13 (work in
progress), September 2013.
[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
Loughney, "Diameter Credit-Control Application", RFC 4006, Loughney, "Diameter Credit-Control Application", RFC 4006,
August 2005. August 2005.
[RFC5729] Korhonen, J., Jones, M., Morand, L., and T. Tsou,
"Clarifications on the Routing of Diameter Requests Based
on the Username and the Realm", RFC 5729, December 2009.
[RFC7068] McMurry, E. and B. Campbell, "Diameter Overload Control
Requirements", RFC 7068, November 2013.
Appendix A. Issues left for future specifications Appendix A. Issues left for future specifications
The base solution for the overload control does not cover all The base solution for the overload control does not cover all
possible use cases. A number of solution aspects were intentionally possible use cases. A number of solution aspects were intentionally
left for future specification and protocol work. left for future specification and protocol work.
A.1. Additional traffic abatement algorithms A.1. Additional traffic abatement algorithms
This specification describes only means for a simple loss based This specification describes only means for a simple loss based
algorithm. Future algorithms can be added using the designed algorithm. Future algorithms can be added using the designed
skipping to change at page 31, line 48 skipping to change at page 33, line 29
A.2. Agent Overload A.2. Agent Overload
This specification focuses on Diameter end-point (server or client) This specification focuses on Diameter end-point (server or client)
overload. A separate extension will be required to outline the overload. A separate extension will be required to outline the
handling the case of agent overload. handling the case of agent overload.
A.3. DIAMETER_TOO_BUSY clarifications A.3. DIAMETER_TOO_BUSY clarifications
The current [RFC6733] behaviour in a case of DIAMETER_TOO_BUSY is The current [RFC6733] behaviour in a case of DIAMETER_TOO_BUSY is
somewhat underspecified. For example, there is no information how somewhat under specified. For example, there is no information how
long the specific Diameter node is willing to be unavailable. A long the specific Diameter node is willing to be unavailable. A
specification updating [RFC6733] should clarify the handling of specification updating [RFC6733] should clarify the handling of
DIAMETER_TOO_BUSY from the error answer initiating Diameter node DIAMETER_TOO_BUSY from the error answer initiating Diameter node
point of view and from the original request initiating Diameter node point of view and from the original request initiating Diameter node
point of view. Further, the inclusion of possible additional point of view. Further, the inclusion of possible additional
information providing APVs should be discussed and possible be information providing AVPs should be discussed and possible be
recommended to be used. recommended to be used.
Appendix B. Conformance to Requirements Appendix B. Examples
The following section analyses, which Diameter Overload Control B.1. Mix of Destination-Realm routed requests and Destination-Host
requirements [I-D.ietf-dime-overload-reqs] are met by this routed requests
specification.
Key: Diameter allows a client to optionally select the destination server
of a request, even if there are agents between the client and the
server. The client does this using the Destination-Host AVP. In
cases where the client does not care if a specific server receives
the request, it can omit Destination-Host and route the request using
the Destination-Realm and Application Id, effectively letting an
agent select the server.
S - Supported Clients commonly send mixtures of Destination-Host and Destination-
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.
P - Partial An agent has very limited options in applying overload abatement to
requests that contain Destination-Host AVPs. It typically cannot
route the request to a different server than the one identified in
Destination-Host. It's only remaining options are to throttle such
requests locally, or to send an overload report back towards the
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.
N - Not supported On the other hand, an agent has much more leeway to apply overload
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
| Rqmt | S/ | Notes | there is not sufficient capacity across all servers to handle even
| # | P/ | | realm-routed requests. In this case, the realm itself can be
| | N | | considered overloaded. The agent may need the client to throttle
+------+----+-------------------------------------------------------+ realm-routed requests in addition to Destination-Host routed
| REQ | P | The DOIC solution only addresses overload | requests. The overload severity may be different for each server,
| 1 | | information. Load information is left as future | and the severity for the realm at is likely to be different than for
| | | work. In addition, the DOIC solution does not | any specific server. Therefore, an agent may need to forward, or
| | | address agent overload scenarios. | originate, multiple overload reports with differing ReportType and
| | | - | Reduction-Percentage values.
| REQ | P | The DOIC solution supports overload reports that |
| 2 | | implicitly indicate the application impacted by the |
| | | report. The DOIC solution does not support reporting |
| | | load information. The DOIC solution is thought to |
| | | support graceful behavior. Allowing an application |
| | | specific capabilities negotiation mechanism violates |
| | | application-independence. Suggested different |
| | | wording: The DOIC solution supports overload reports |
| | | that are applicable to any Diameter application. The |
| | | DOIC solution does not support reporting load |
| | | information. The DOIC solution allows to support |
| | | graceful behavior; this will be enhanced when the |
| | | Load information will be defined. Comment: Can we |
| | | removed the words "is thought"? |
| | | - |
| REQ | S | The DOIC solution is thought to address this |
| 3 | | requirement. Comment: Can we removed the words "is |
| | | thought"? |
| | | - |
| REQ | P | The DOIC solution does allow for both both a Diameter |
| 4 | | server and a Diameter client to send overload |
| | | reports. The DOIC solution only addresses Diameter |
| | | end-point (server and client) overload. Agent |
| | | overload is being addressed in a separate draft. |
| | | - |
| REQ | S | The DOIC solution does not depend on how the |
| 5 | | end-points are discovered. Comment: it might be |
| | | worth working through at least one use case showing |
| | | DNS based dynamic peer discovery to make sure we |
| | | haven't missed anything. |
| | | - |
| REQ | ? | Need to update text as some configuation is required. |
| 6 | | Need to determin if the current discussion on |
| | | overload application id increases the amount of |
| | | configuration which would change this to a N. |
| | | - |
| REQ | S | The DOIC solution supports the loss algorithm, which |
| 7 | | is expected to address this requirement. There is |
| | | concern about the ability to address oscillations. |
| | | Wording is included for how a reacting node starts to |
| | | increase traffic after an overload report expires to |
| | | address this concern. Suggested different wording: |
| | | The DOIC solution supports a baseline mechanism |
| | | relying on traffic reduction percentage that is a |
| | | loss algorithm, which allows to address this |
| | | requirement. Oscillations are avoided or quite |
| | | minimized by sending successive OLR reports with the |
| | | values to converge to the optimal traffic or to |
| | | smoothly come back to normal traffic conditions when |
| | | overload decreases and ends. |
| | | - |
| REQ | ? | The DOIC solution supports a timestamp which is meant |
| 8 | | to serve as a report version indication to address |
| | | this requirement. Comment: The use of the timestamp |
| | | is under discussion. |
| | | - |
| REQ | ? | The DOIC solution uses a piggybacking strategy for |
| 9 | | carrying overload reports, which scales lineraly with |
| | | the amount of traffic. As such, the first part of |
| | | the requirement is addressed. The DOIC solution does |
| | | not support a mechanism for sending overload reports |
| | | over a quiescent transport connections or, more |
| | | generally, to Diameter nodes that are not producing |
| | | traffic. Suggested different wording: The DOIC |
| | | solution uses a piggybacking strategy for carrying |
| | | overload reports. As such, the first part of the |
| | | requirement is addressed. For a connection that has |
| | | become quiescent due to OLRs with a 100% traffic |
| | | reduction, the validity timer allows to handle this |
| | | case. Other cases of quiescent connections are |
| | | outside the scope of Diameter overload (e.g. their |
| | | handling may be done through the watch dog of the |
| | | Diameter base protocol). |
| | | - |
| REQ | S | The DOIC solution supports two methods for managing |
| 10 | | the length of an overload condition. First, all |
| | | overload reports must contain a duration indication, |
| | | after which the node reacting to the report can |
| | | consider the overload condition as ended. Secondly, |
| | | the solution supports the method for the node |
| | | originating the overload report to explicitly |
| | | communicate that the condition has ended. This |
| | | latter mechanism depends on traffic to be sent from |
| | | the reacting node and, as such, can not be depended |
| | | upon in all circumstances. |
| | | - |
| REQ | ? | The DOIC solution works well for small network |
| 11 | | configurations and for network configurations with a |
| | | single Diameter agent hop. More analysis is required |
| | | to determine how well the DOIC solution handles very |
| | | large Diameter network with partitioned or segmented |
| | | server farms requiring multiple hops through Diameter |
| | | agents. |
| | | - |
| REQ | P | The DOIC solution focuses on Diameter end-point |
| 12 | | overload and meets this requirement for those |
| | | Diameter nodes. The DOIC solution does not address |
| | | Diameter Agent overload and does not meet this |
| | | requirement for those Diameter nodes. |
| | | - |
| REQ | ? | The DOIC solution requires including of the overload |
| 13 | | report in all answer messages in some situations. It |
| | | is not agreed, however, that this constitutes |
| | | substantial work. This can also be mitigated by the |
| | | sender of the overload report keeping state to record |
| | | who has received overload reports. It is left to |
| | | implementation decisions as to which approach is |
| | | taken -- send in all messages or send once with a |
| | | record of who has received the report. Another way |
| | | is to let the request sender (reacting node) insert |
| | | information in the request to say whether a |
| | | throttling is actually performed. The reporting node |
| | | then can base its decision on information received in |
| | | the request; no need for keeping state to record who |
| | | has received overload reports. The DOIC solution |
| | | also requires capabilities negotiation in every |
| | | request and response message, which increases the |
| | | baseline work required for any node supporting the |
| | | DOIC solution. Suggested additional text: It does |
| | | not, however, require that the information be |
| | | recalculated or updated with each message. The |
| | | update frequency is up to the implementation, and |
| | | each implementation can make decisions on balancing |
| | | the update of overload information along with its |
| | | other priorities. It is expected that using a |
| | | periodically updated OLR report added to all messages |
| | | sent to overload control endpoints will not add |
| | | substantial additional work. Piggyback base |
| | | transport also does not require composition, sending, |
| | | or parsing of new Diameter messages for the purpose |
| | | of conveying overload control information. There is |
| | | still discussion on the substantial additional work |
| | | due to have OLR in each answer message. |
| | | - |
| REQ | S | The DOIC solution uses the piggybacking method to |
| 14 | | deliver overload report, which scales lineraly with |
| | | the amount of traffic. This allows for immediate |
| | | feedback to any node generating traffic toward |
| | | another overloaded node. |
| | | - |
| REQ | S | The DOIC solution does not interfere with transport |
| 15 | | protocols. |
| | | - |
| REQ | ? | The DOIC solution allows for a mixed network of |
| 16 | | supporting and non supporting Diameter end-points. |
| | | It isn't clear how realm overload is handled in a |
| | | network with agents that do not support the DOIC |
| | | solution. Suggested additional wording: Evaluation |
| | | of Realm overload may require a DA supporting DOIC, |
| | | if the realm overload is not evaluated by the client. |
| | | Realm overload handling is still under discussion. |
| | | - |
| REQ | ? | Suggested wording: The DOIC solution addresses this |
| 17 | | requirement through the loss algorithm (DOIC baseline |
| | | mechanism) with the following possibilities. A DA |
| | | supporting DOIC can act on behalf of clients not |
| | | supporting DOIC. A reporting node is also aware of |
| | | the nodes not supporting the DOIC as there is no |
| | | advertisement of the DOIC support. It may then apply |
| | | a particular throttling of the requests coming from |
| | | these non supporting DOIC clients. |
| | | - |
| REQ | ? | It isn't clear yet that if this requirement is |
| 18 | | addressed. There has been a proposal to mark |
| | | messages that survived overload throttling as one |
| | | method for an overloaded node to address fairness but |
| | | this proposal is not yet part of the solution. It is |
| | | also possible that the overloaded node could use |
| | | state gathered as part of the capability |
| | | advertisement mechanism to know if the sending node |
| | | supports the DOIC solution and if not, to apply a |
| | | particular throttling of the requests coming from |
| | | these non supporting DOIC clients. |
| | | - |
| REQ | S | The DOIC solution supports the ability for the |
| 19 | | overloaded node and the reacting node to be in |
| | | different administrative domains. |
| | | - |
| REQ | ? | This mechanism is still under discussion. Comment 1: |
| 20 | | I think this is a "S". OLRs are clearly |
| | | distinguishable from any error code. The fact that |
| | | an agent would need to send errors if it throttles is |
| | | not an overload indication per se. It needs to do |
| | | that even without DoC. OTOH, if we apply some DOC |
| | | related fix to TOO_BUSY, we probably need a new code. |
| | | Comment 2: New AVPs conveys overload control |
| | | information, and this is transported on existing |
| | | answer messages, so distinguishable from Diameter |
| | | errors. |
| | | - |
| REQ | S | The inability for a node to send overload reports |
| 21 | | will result in equivalent through put to a network |
| | | that does not support the DOIC solution. |
| | | - |
| REQ | S | The DOIC solution gives this node generating the |
| 22 | | overload report the ability to control the amount of |
| | | throttling done by the reacting node using the |
| | | reduction percentage parameter in the overload |
| | | report. |
| | | - |
| REQ | ? | Initial text: The DOIC mechanism supports two |
| 23 | | abatement strategies by reacting nodes, routing to an |
| | | alternative node or dropping traffic. The routing to |
| | | an alternative node will be enhanced when the Load |
| | | extension is defined. Comment: This is a N. There's |
| | | no good way to determine which nodes are likely to |
| | | have sufficient capacity without some sort of load |
| | | metric for non-overloaded nodes. |
| | | - |
| REQ | N | The DOIC solution does not address delivering load |
| 24 | | information. |
| | | - |
| REQ | S | The DOIC solution contains some guideance. |
| 25 | | |
| | | - |
| REQ | S | The DOIC solution does not constrain a nodes ability |
| 26 | | to determine which requests are trottled. |
| | | - |
| REQ | ? | Initial text: The DOIC solution does add a new line |
| 27 | | of attack in the ability for a malicious entity to |
| | | insert overload reports that would reduce or |
| | | eliminate traffic. This, however, is no worse than |
| | | an attacker that would assert erroneous error |
| | | responses such as a TOO BUSY response. It is |
| | | recognized that the end-to-end security solution |
| | | currently being worked on by the DIME working group |
| | | is needed to close these types of vulurabilities. |
| | | Comment: Sending a malicious OLR with a type of |
| | | "realm" will have considerably more impact than a |
| | | TOO_BUSY. Personally, I don't think we can achieve |
| | | this requirement without either being hop-by-hop or |
| | | requiring e2e security. We probably need further |
| | | analysis of the security implications of the |
| | | capabilities negotiation as well. Suggested |
| | | additional verbage: An OLR only relates to the |
| | | traffic between a reporting node and a reacting node |
| | | and can effectively block the traffic from a client |
| | | which would be an important impact. Nevertheless |
| | | OLRs are regularly sent in all answers, so a |
| | | malicious OLR will have a short transient effect, as |
| | | quickly overridden by a new OLR. To have a |
| | | significant impact would require a continuous flow of |
| | | answers with malicious OLRs. There is the exception |
| | | of the OLR with a value of 100% reduction traffic |
| | | which has a higher vulnerability and the use of which |
| | | should be avoided when possible. In addition such |
| | | malicious OLRs must be in answers, which means the |
| | | capability to insert the malicious OLR in an existing |
| | | answer rather than to create an answer which is much |
| | | less easy than to create a request. To have a |
| | | network wide applicability would request to generate |
| | | malicious OLRs messages towards all reacting nodes. |
| | | It can be considered that the baseline mechanism |
| | | offer a relevant level of security. Further analysis |
| | | with a security expertise would be beneficial. |
| | | - |
| REQ | ? | See REQ 18 and REQ 27. Suggested additional verbage: |
| 28 | | Guidance may be provided for detection of non |
| | | compliant/abnormal use of OLRs, not only by endpoints |
| | | but also by intermediate DA that can be aware of |
| | | OLRs, an example being edge DAs with external |
| | | networks. Further analysis with a security expertise |
| | | would be beneficial. |
| | | - |
| REQ | ? | This requirement is not explicitly addressed by the |
| 29 | | DOIC solution. There is nothing in the DOIC solution |
| | | that would prevent the goals of this requirement from |
| | | being achieved. Non-adjacent DOIC without e2e |
| | | security could be an issue here. |
| | | - |
| REQ | ? | It isn't clear how a solution would interfere. |
| 30 | | Suggested wording: A node can have methods on how to |
| | | protect from overload from nodes non supporting DOIC. |
| | | The DOIC mechanism used with DOIC supporting nodes |
| | | will not interfere with the appliance of these |
| | | methods. There is the remark that the use of these |
| | | methods may impact the global overload of the node |
| | | and the evaluation of the traffic reduction that the |
| | | reporting node will send in OLRs. If a node has |
| | | methods to protect against denial of service attacks, |
| | | the use of DOIC will not interfere with them. A |
| | | denial of service attack concerning the DOIC itself |
| | | is addressed in REQ 27. |
| | | - |
| REQ | ? | Initial text with an S: The DOIC solution addresses |
| 31 | | node and realm directly. The application to which a |
| | | report applies is implicitly determined based on the |
| | | application level message carrying the report. Note |
| | | that there is no way with DOIC for an overloaded node |
| | | to communicate multiple nodes, realms or applications |
| | | in a single overload report. So the inverse of this |
| | | requirement is not supported. Comment: The inverse |
| | | is also not _required_ :-) But I think we are "P" |
| | | here, in that we don't support "node" per se. we do |
| | | support "server." "Node" includes agents. (I also |
| | | interpreted this to mean that each granularity needed |
| | | to be supported independently--that is, a potential |
| | | to say "all traffic to a realm" or "all traffic to a |
| | | host" independently of application.) |
| | | - |
| REQ | ? | Initial text with an S: The DOIC solution supports |
| 32 | | extensibility of both the information communicated |
| | | and in the definition of new overload abatement |
| | | algorithms. Comment 1: Recent discussions have made |
| | | this a ?. It can be changed to S/N/P once these |
| | | discussions come to a conclusion and new text is |
| | | added to the draft. Comment 2: Suggested wording - |
| | | The DOIC solution supports extensibility of both the |
| | | information communicated and in the definition of new |
| | | overload abatement algorithms or strategies. It |
| | | should be noted that, according to the applications |
| | | or to reacting node implementations, many algorithms |
| | | may be applied on top of the DOIC baseline solution |
| | | (without contradicting it), e.g. regarding which type |
| | | of request to throttle, prioritized messages |
| | | handling, mapping of the reduction % to an internal |
| | | algorithm (eg 1 message out of ten etc..) but such |
| | | algorithms are out of scope of DOIC. |
| | | - |
| REQ | ? | Initial text with P: The DOIC solution currently |
| 33 | | defines the loss algorithm as the default algorithm. |
| | | It does not specify it as mandatory to implement. |
| | | Comment 1: Then I think that's a "n". The MTI part |
| | | is the crux of the requirement. Comment 2: Suggested |
| | | wording: In the DOIC baseline solution, the reacting |
| | | node has to apply the received Reduction-Percentage, |
| | | and for achieving this, the reacting node can do |
| | | requests rerouting (when it is possible) or |
| | | drop/reject requests. This DOIC baseline solution is |
| | | a loss algorithm and DOIC should not require further |
| | | specification. The answer to REQ32 indicates the |
| | | possibility to add other algorithms on top of the |
| | | DOIC baseline solution. The DOIC solution currently |
| | | defines this loss algorithm as the default algorithm. |
| | | It is still under discussion to make it as mandatory |
| | | to implement. |
| | | - |
| REQ | P | The ability to communicate overload reports between |
| 34 | | supporting Diameter nodes does not require agents to |
| | | support the DOIC solution. Load information exchange |
| | | is not currently defined. |
+------+----+-------------------------------------------------------+
Table 1 Figure 8 illustrates such a mixed-routing scenario. In this example,
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.
Appendix C. Examples Client Agent S1 S2 S3
| | | | |
|(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
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
C.1. 3GPP S6a interface overload indication Figure 8: Mix of Destination-Host and Destination-Realm Routed
Requests
[TBD: Would cover S6a MME-HSS communication with several topology 1. The client sends a request with no Destination-Host AVP (that is,
choices (such as with or without DRA, and with "generic" agents).] a Destination-Realm routed request.)
C.2. 3GPP PCC interfaces overload indication 2. The agent follows local policy to select a server from its peer
table. In this case, the agent selects S2 and forwards the
request.
[TBD: Would cover Gx/Rx and maybe S9..] 3. S1 is overloaded. It sends a answer indicating success, but also
includes an overload report. Since the overload report only
applies to S1, the ReportType is "Destination-Host".
C.3. Mix of Destination-Realm routed requests and Destination-Host 4. The agent sees the overload report, and records that S1 is
reouted requests overloaded by the value in the Reduction-Percentage AVP. It
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.
[TBD: Add example showing the use of Destination-Host type OLRs and 5. The client sends another Destination-Realm routed request.
Realm type OLRs.]
6. The agent selects S2, and forwards the request.
7. It turns out that S2 is also overloaded, perhaps due to all that
traffic it took over for S1. S2 returns an successful answer
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
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.)
Authors' Addresses Authors' Addresses
Jouni Korhonen (editor) Jouni Korhonen (editor)
Broadcom Broadcom
Porkkalankatu 24 Porkkalankatu 24
Helsinki FIN-00180 Helsinki FIN-00180
Finland Finland
Email: jouni.nospam@gmail.com Email: jouni.nospam@gmail.com
skipping to change at line 1803 skipping to change at page 38, line 4
Email: srdonovan@usdonovans.com Email: srdonovan@usdonovans.com
Ben Campbell Ben Campbell
Oracle Oracle
17210 Campbell Road 17210 Campbell Road
Dallas, Texas 75254 Dallas, Texas 75254
United States United States
Email: ben@nostrum.com Email: ben@nostrum.com
Lionel Morand
Orange Labs
38/40 rue du General Leclerc
Issy-Les-Moulineaux Cedex 9 92794
France
Phone: +33145296257
Email: lionel.morand@orange.com
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