draft-ietf-dime-load-07.txt   draft-ietf-dime-load-08.txt 
Internet Engineering Task Force B. Campbell Internet Engineering Task Force B. Campbell
Internet-Draft S. Donovan, Ed. Internet-Draft S. Donovan, Ed.
Intended status: Standards Track Oracle Intended status: Standards Track Oracle
Expires: August 11, 2017 JJ. Trottin Expires: September 8, 2017 JJ. Trottin
Nokia Nokia
February 7, 2017 March 7, 2017
Diameter Load Information Conveyance Diameter Load Information Conveyance
draft-ietf-dime-load-07 draft-ietf-dime-load-08
Abstract Abstract
This document defines a mechanism for conveying of Diameter load RFC7068 describes requirements for Overload Control in Diameter.
information. RFC7068 describes requirements for Overload Control in This includes a requirement to allow Diameter nodes to send "load"
Diameter. This includes a requirement to allow Diameter nodes to information, even when the node is not overloaded. RFC7683 (Diameter
send "load" information, even when the node is not overloaded. Overload Information Conveyance (DOIC)) solution describes a
RFC7683 (Diameter Overload Information Conveyance (DOIC)) solution mechanism meeting most of the requirements, but does not currently
describes a mechanism meeting most of the requirements, but does not include the ability to send load information. This document defines
currently include the ability to send load information. a mechanism for conveying of Diameter load information.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 11, 2017. This Internet-Draft will expire on September 8, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4.1. Differences between Load and Overload information . . . . 4 4.1. Differences between Load and Overload information . . . . 4
4.2. How is Load Information Used? . . . . . . . . . . . . . . 5 4.2. How is Load Information Used? . . . . . . . . . . . . . . 5
5. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6 5. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Theory of Operation . . . . . . . . . . . . . . . . . . . 8 5.1. Theory of Operation . . . . . . . . . . . . . . . . . . . 8
6. Load Mechanism Procedures . . . . . . . . . . . . . . . . . . 10 6. Load Mechanism Procedures . . . . . . . . . . . . . . . . . . 10
6.1. Reporting Node Behavior . . . . . . . . . . . . . . . . . 10 6.1. Reporting Node Behavior . . . . . . . . . . . . . . . . . 10
6.1.1. Endpoint Reporting Node Behavior . . . . . . . . . . 10 6.1.1. Endpoint Reporting Node Behavior . . . . . . . . . . 10
6.1.2. Agent Reporting Node Behavior . . . . . . . . . . . . 11 6.1.2. Agent Reporting Node Behavior . . . . . . . . . . . . 11
6.2. Reacting Node Behavior . . . . . . . . . . . . . . . . . 12 6.2. Reacting Node Behavior . . . . . . . . . . . . . . . . . 12
6.3. Extensibility . . . . . . . . . . . . . . . . . . . . . . 13 6.3. Extensibility . . . . . . . . . . . . . . . . . . . . . . 13
6.4. Addition and removal of Nodes . . . . . . . . . . . . . . 13 6.4. Addition and Removal of Nodes . . . . . . . . . . . . . . 13
7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 14 7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 14
7.1. Load AVP . . . . . . . . . . . . . . . . . . . . . . . . 14 7.1. Load AVP . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Load-Type AVP . . . . . . . . . . . . . . . . . . . . . . 14 7.2. Load-Type AVP . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Load-Value AVP . . . . . . . . . . . . . . . . . . . . . 14 7.3. Load-Value AVP . . . . . . . . . . . . . . . . . . . . . 14
7.4. SourceID AVP . . . . . . . . . . . . . . . . . . . . . . 15 7.4. SourceID AVP . . . . . . . . . . . . . . . . . . . . . . 15
7.5. Attribute Value Pair flag rules . . . . . . . . . . . . . 15 7.5. Attribute Value Pair flag rules . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 16 9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16 10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Topology Scenarios . . . . . . . . . . . . . . . . . 17 Appendix A. Topology Scenarios . . . . . . . . . . . . . . . . . 17
A.1. No Agent . . . . . . . . . . . . . . . . . . . . . . . . 17 A.1. No Agent . . . . . . . . . . . . . . . . . . . . . . . . 17
A.2. Single Agent . . . . . . . . . . . . . . . . . . . . . . 17 A.2. Single Agent . . . . . . . . . . . . . . . . . . . . . . 17
A.3. Multiple Agents . . . . . . . . . . . . . . . . . . . . . 18 A.3. Multiple Agents . . . . . . . . . . . . . . . . . . . . . 18
A.4. Linked Agents . . . . . . . . . . . . . . . . . . . . . . 18 A.4. Linked Agents . . . . . . . . . . . . . . . . . . . . . . 19
A.5. Shared Server Pools . . . . . . . . . . . . . . . . . . . 20 A.5. Shared Server Pools . . . . . . . . . . . . . . . . . . . 20
A.6. Agent Chains . . . . . . . . . . . . . . . . . . . . . . 20 A.6. Agent Chains . . . . . . . . . . . . . . . . . . . . . . 20
A.7. Fully Meshed Layers . . . . . . . . . . . . . . . . . . . 20 A.7. Fully Meshed Layers . . . . . . . . . . . . . . . . . . . 21
A.8. Partitions . . . . . . . . . . . . . . . . . . . . . . . 21 A.8. Partitions . . . . . . . . . . . . . . . . . . . . . . . 21
A.9. Active-Standby Nodes . . . . . . . . . . . . . . . . . . 21 A.9. Active-Standby Nodes . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
[RFC7068] describes requirements for Overload Control in Diameter [RFC7068] describes requirements for Overload Control in Diameter
[RFC6733]. The DIME working group has finished the Diameter Overload [RFC6733]. The DIME working group has finished the Diameter Overload
Information Conveyance (DOIC) mechanism [RFC7683]. As currently Information Conveyance (DOIC) mechanism [RFC7683]. As currently
specified, DOIC fulfills some, but not all, of the requirements. specified, DOIC fulfills some, but not all, of the requirements.
In particular, DOIC does not fulfill Req 23 and Req 24: In particular, DOIC does not fulfill Req 23 and Req 24:
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that the working group did not agree on a general approach for that the working group did not agree on a general approach for
conveying load information. It chose to progress the rest of DOIC, conveying load information. It chose to progress the rest of DOIC,
and deferred load information conveyance to a DOIC extension or a and deferred load information conveyance to a DOIC extension or a
separate mechanism. separate mechanism.
This document defines a mechanism that addresses the load-related This document defines a mechanism that addresses the load-related
requirements from RFC 7068. requirements from RFC 7068.
2. Terminology and Abbreviations 2. Terminology and Abbreviations
AVP
Attribute Value Pair
DOIC DOIC
Diameter Overload Information Conveyance ([RFC7683]) Diameter Overload Information Conveyance ([RFC7683])
Load Load
The relative usage of the Diameter message processing capacity of The relative usage of the Diameter message processing capacity of
a Diameter node. A low load level indicates that the Diameter a Diameter node. A low load level indicates that the Diameter
node is under utilized. A high load level indicates that the node node is under utilized. A high load level indicates that the node
is closer to being fully utilized. is closer to being fully utilized.
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Diameter Overload Information Conveyance ([RFC7683]) Diameter Overload Information Conveyance ([RFC7683])
Load Load
The relative usage of the Diameter message processing capacity of The relative usage of the Diameter message processing capacity of
a Diameter node. A low load level indicates that the Diameter a Diameter node. A low load level indicates that the Diameter
node is under utilized. A high load level indicates that the node node is under utilized. A high load level indicates that the node
is closer to being fully utilized. is closer to being fully utilized.
Offered Load Offered Load
The actual traffic sent to the reporting node after overload The actual traffic sent to the reporting node after overload
abatement and routing decisions are made. abatement and routing decisions are made.
Reporting, Reacting Node Reporting Node
Reporting node and reacting node terminology is defined in Reporting Node: A Diameter node that generates a load report.
[RFC7683].
Reacting Node
Reacting Node: A Diameter node that acts upon a load report.
Routing Information Routing Information
Routing Information referred to in this document can include the Routing Information referred to in this document can include the
Routing and Peer tables defined in RFC 6733. It can also include Routing and Peer tables defined in RFC 6733. It can also include
other implementation specific tables used to store load other implementation specific tables used to store load
information. This document does not define the structure of such information. This document does not define the structure of such
tables. tables.
3. Conventions Used in This Document 3. Conventions Used in This Document
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document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
RFC 2119 [RFC2119] interpretation does not apply for the above listed RFC 2119 [RFC2119] interpretation does not apply for the above listed
words when they are not used in all-caps format. words when they are not used in all-caps format.
4. Background 4. Background
4.1. Differences between Load and Overload information 4.1. Differences between Load and Overload information
Previous discussions of how to solve the load-related requirements in Previous discussions of how to solve the load-related requirements in
[RFC7068] have shown that people did not had an agreed-upon concept [RFC7068] have shown that people did not have an agreed-upon concept
of how "load" information differs from "overload" information. While of how "load" information differs from "overload" information. While
the two concepts are highly interrelated, in the opinion of the the two concepts are highly interrelated, there are two primary
authors, there are two primary differences. First, a Diameter node differences. First, a Diameter node always has a load. At any given
always has a load. At any given time that load may be effectively time that load may be effectively zero, effectively fully loaded, or
zero, effectively fully loaded, or somewhere in between. In somewhere in between. In contrast, overload is an exceptional
contrast, overload is an exceptional condition. A node only has condition. A node only has overload information when it is in an
overload information when it is in an overloaded state. Furthermore, overloaded state. Furthermore, the relationship between a node's
the relationship between a node's load level and overload state at load level and overload state at any given time may be vague. For
any given time may be vague. For example, a node may normally example, a node may normally operate at a "fully loaded" level, but
operate at a "fully loaded" level, but still not be considered still not be considered overloaded. Another node may declare itself
overloaded. Another node may declare itself to be "overloaded" even to be "overloaded" even though it might not be fully "loaded".
though it might not be fully "loaded".
Second, Overload information, in the form of a DOIC Overload Report Second, Overload information, in the form of a DOIC Overload Report
(OLR) [RFC7683] indicates an explicit request for action on the part (OLR) [RFC7683] indicates an explicit request for action on the part
of the reacting node. That is, the OLR requests that the reacting of the reacting node. That is, the OLR requests that the reacting
node reduce the offered load -- the actual traffic sent to the node reduces the offered load -- the actual traffic sent to the
reporting node after overload abatement and routing decisions are reporting node after overload abatement and routing decisions are
made -- by an indicated amount (by default), or as prescribed by the made -- by an indicated amount (by default), or as prescribed by the
selected abatement algorithm. Effectively, DOIC provides a contract selected abatement algorithm. Effectively, DOIC provides a contract
between the reporting node and the reacting node. between the reporting node and the reacting node.
In contrast, load is informational. That is, load information can be In contrast, load is informational. That is, load information can be
considered a hint to the recipient node. That node may use the load considered a hint to the recipient node. That node may use the load
information for load balancing purposes, as an input to certain information for load balancing purposes, as an input to certain
overload abatement techniques, to make inferences about the overload abatement techniques, to make inferences about the
likelihood that the sending node becomes overloaded in the immediate likelihood that the sending node becomes overloaded in the immediate
future, or for other purposes. future, or for other purposes.
None of this prevents a Diameter node from deciding to reduce the None of this prevents a Diameter node from deciding to reduce the
offered load based on load information. The fundamental difference offered load based on load information. The fundamental difference
is that an overload report requires that reduction. It is also is that an overload report requires the reduction of offered load.
reasonable for a Diameter node to decide to increase the offered load It is also reasonable for a Diameter node to decide to increase the
based on load information. offered load based on load information.
4.2. How is Load Information Used? 4.2. How is Load Information Used?
[RFC7068] contemplates two primary uses for load information. Req 23 [RFC7068] contemplates two primary uses for load information. Req 23
discusses how load information might be used when performing discusses how load information might be used when performing
diversion as an overload abatement technique, as described in diversion as an overload abatement technique, as described in
[RFC7683]. When a reacting node diverts traffic away from an [RFC7683]. When a reacting node diverts traffic away from an
overloaded node, it needs load information for the other candidates overloaded node, it needs load information for the other candidates
for that traffic in order to effectively load balance the diverted for that traffic in order to effectively load balance the diverted
load between potential candidates. Otherwise, diversion has a load between potential candidates. Otherwise, diversion has a
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Req 24 discusses how Diameter load information might be used when no Req 24 discusses how Diameter load information might be used when no
overload condition currently exists. Diameter nodes can use the load overload condition currently exists. Diameter nodes can use the load
information to make decisions to try to avoid overload conditions in information to make decisions to try to avoid overload conditions in
the first place. Normal load-balancing falls into this category, but the first place. Normal load-balancing falls into this category, but
the diameter node can take other proactive steps as well. the diameter node can take other proactive steps as well.
If the loaded nodes are Diameter servers (or clients in the case of If the loaded nodes are Diameter servers (or clients in the case of
server-to-client transactions), both of these uses of load server-to-client transactions), both of these uses of load
information should be accomplished by a Diameter node that performs information should be accomplished by a Diameter node that performs
server selection. Typically, server selection is performed by a node server selection (selection of the Diameter endpont to which the
(a client or an agent) that is an immediate peer of the server. request is to be routed for processing). Typically, server selection
However, there are scenarios (see Appendix A) where a client or proxy is performed by a node (a client or an agent) that is an immediate
that is not the immediate peer to the selected servers performs peer of the server. However, there are scenarios (see Appendix A)
server selection. In this case, the client or proxy enforces the where a client or proxy that is not the immediate peer to the
server selection by inserting a Destination-Host AVP. selected servers performs server selection. In this case, the client
or proxy enforces the server selection by inserting a Destination-
Host AVP.
For example, a Diameter node (e.g. client) can use a redirect For example, a Diameter node (e.g. client) can use a redirect
agent to get candidate destination host addresses. The redirect agent to get candidate destination host addresses. The redirect
agent might return several destination host addresses, from which agent might return several destination host addresses, from which
the Diameter node selects one. The Diameter node can use load the Diameter node selects one. The Diameter node can use load
information received from these hosts to make the selection. information received from these hosts to make the selection.
Just as load information can be used as part of server selection, it Just as load information can be used as part of server selection, it
can also be used as input to the selection of the next-hop peer to can also be used as input to the selection of the next-hop peer to
which a request is to be routed. which a request is to be routed.
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The second big difference between DOIC and Load is visibility of the The second big difference between DOIC and Load is visibility of the
DOIC or Load information within a Diameter network. DOIC information DOIC or Load information within a Diameter network. DOIC information
is sent end-to-end resulting in the ability of all nodes in the path is sent end-to-end resulting in the ability of all nodes in the path
of the answer message that carries the OC-OLR AVP to act on the of the answer message that carries the OC-OLR AVP to act on the
information, although only one node actually comsumes and reacts to information, although only one node actually comsumes and reacts to
the report. The DOIC overload reports remain in the message all the the report. The DOIC overload reports remain in the message all the
way from the reporting node to the node that is the target for the way from the reporting node to the node that is the target for the
answer message. answer message.
For the Load mechanism there are two types of load reports and only For the Load mechanism there are two types of Load reports and only
the first one is transmitted end-to-end. the first one is transmitted end-to-end.
The first is the load of the endpoint sending the answer message. The first type of load report is a HOST report which contains the
This load report is carried end-to-end to enable any nodes that make load of the endpoint sending the answer message. This Load report is
server selection decisions to use the load status of the sending carried end-to-end to enable any nodes that make server selection
endpoint as part of the server selection decision. Unlike with DOIC, decisions to use the load status of the sending endpoint as part of
more than one node may make use of the load information received. the server selection decision. Unlike with DOIC, more than one node
may make use of the load information received.
The second type of load report is a peer report. This report is used The second type of Load report is a PEER report. This report is used
by Diameter nodes as part of the logic to select the next-hop by Diameter nodes as part of the logic to select the next-hop
Diameter node and, as such, does not have significance beyond the Diameter node and, as such, does not have significance beyond the
peer node. These load reports are removed by the first supporting peer node. Load reports of type PEER are removed by the first
Diameter node to receive the report. supporting Diameter node to receive the report.
Because load reports can traverse Diameter nodes that do not support Because Load reports can traverse Diameter nodes that do not support
the Load mechanism, it is necessary to include the identity of the the Load mechanism, it is necessary to include the identity of the
node to which the load report applies as part of the load report. node to which the Load report applies as part of the Load report.
This allows for a Diameter node to verify that a load report applies This allows for a Diameter node to verify that a Load report applies
to its peer or if it should be ignored. to its peer or if it should be ignored.
The load report includes a value indicating the load of the sending The Load report includes a value indicating relative load of the
node relative load of the sending node, specified in a manner sending node, specified in a manner consistent with that defined for
consistent with that defined for DNS SRV [RFC2782]. DNS SRV [RFC2782].
The goal is to make it possible to use both the load values received The goal is to make it possible to use both the load values received
as a part of the Diameter Load mechanism and weight values received as a part of the Diameter Load mechanism and weight values received
as a result of a DNS SRV query. As a result, the Diameter load value as a result of a DNS SRV query. As a result, the Diameter load value
has a range of 0-65535. This value and DNS SRV weight values are has a range of 0-65535. This value and DNS SRV weight values are
then used in a distribution algorithm similar to that specified in then used in a distribution algorithm similar to that specified in
[RFC2782]. [RFC2782].
The DNS SRV distribution algorithm results in more messages being The DNS SRV distribution algorithm results in more messages being
sent to a node with a higher weight value. As a result, a higher sent to a node with a higher weight value. As a result, a higher
Diameter load value indicates a LOWER load on the sending node. A Diameter load value indicates a LOWER load on the sending node. A
node that is heavily loaded sends a lower Diameter load value. node that is heavily loaded sends a lower Diameter load value.
Stated another way, a node that has zero load would have a load value Stated another way, a node that has zero load would have a load value
of 65535. A node that is 100% loaded would have a load value of 0. of 65535. A node that is 100% loaded would have a load value of 0.
The distribution algorithm used by Diameter nodes supporting the The distribution algorithm used by Diameter nodes supporting the
Diameter Load mechanism is an implementation decision but it needs to Diameter Load mechanism is an implementation decision but it needs to
result in similar behavior to the algorithm described for the use of result in similar behavior to the algorithm described for the use of
weigh values specified in [RFC2782]. weight values specified in [RFC2782].
The method for calculating the load value included in the load report The method for calculating the load value included in the Load report
is also left as an implementation decision. is also left as an implementation decision.
The frequency for sending of load reports is also left as an The frequency for sending of Load reports is also left as an
implementation decision. The sending node might choose to send load implementation decision. The sending node might choose to send Load
reports in all messages or it might choose to only send load reports reports in all messages or it might choose to only send Load reports
when the load value has changed by some implementation specific when the load value has changed by some implementation specific
amount. The important consideration is that all nodes needing the amount. The important consideration is that all nodes needing the
load information have a sufficiently accurate view of the node's load information have a sufficiently accurate view of the node's
load. load.
5.1. Theory of Operation 5.1. Theory of Operation
This section outlines how the Diameter Load mechanism is expected to This section outlines how the Diameter Load mechanism is expected to
work. work.
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C A1 A4 S[n] C A1 A4 S[n]
| | | | | | | |
|----->|----->|----->| |----->|----->|----->|
xxR xxR xxR xxR xxR xxR
Figure 2: Request Message Path Figure 2: Request Message Path
When sending the answer message, an endpoint node that supports the When sending the answer message, an endpoint node that supports the
Diameter Load mechanism includes its own load information in the Diameter Load mechanism includes its own load information in the
answer message. Because it is a Diameter endpoint it includes a HOST answer message. Because it is a Diameter endpoint it includes a HOST
load report. Load report.
C A1 A4 S[n] C A1 A4 S[n]
| | | | | | | |
| | |<-----| | | |<-----|
| | xxA(Load type:HOST, source:S[n]) | | xxA(Load type:HOST, source:S[n])
| | | | | | | |
Figure 3: Answer Message from S[n] Figure 3: Answer Message from S[n]
If Agent A4 supports the Load mechanism then A4's actions depend on If Agent A4 supports the Load mechanism then A4's actions depend on
whether A4 is responsible for doing server selection. If A4 is not whether A4 is responsible for doing server selection. If A4 is not
doing server selection then A4 ignores the HOST load report. If A4 doing server selection then A4 ignores the HOST Load report. If A4
is responsible for doing server selection then it stores the load is responsible for doing server selection then it stores the load
information for S[n] in its routing information for the handling of information for S[n] in its routing information for the handling of
subsequent request messages. In both cases A4 leaves the HOST report subsequent request messages. In both cases A4 leaves the HOST report
in the message. in the message.
Note: If A4 does not support the Load mechanism then it will relay Note: If A4 does not support the Load mechanism then it will relay
the answer message without doing any processing on the load the answer message without doing any processing on the load
information. In this case the load information AVPs will be information. In this case the load information AVPs will be
relayed without change. relayed without change.
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| |<-----| | | |<-----| |
| xxA(Load type:PEER, source:A4) | xxA(Load type:PEER, source:A4)
| xxA(Load type:HOST, source:S[n]) | xxA(Load type:HOST, source:S[n])
| | | | | | | |
Figure 4: Answer Message from A4 Figure 4: Answer Message from A4
If A1 supports the Load mechanism then it processes each of the Load If A1 supports the Load mechanism then it processes each of the Load
reports it receives separately. reports it receives separately.
For the PEER load report, A1 first determines if the source of the For the PEER Load report, A1 first determines if the source of the
report indicated in the load report matches the DiameterIdentity of report indicated in the Load report matches the DiameterIdentity of
the Diameter node from which the request was received. If the the Diameter node from which the request was received. If the
identities do not match then the PEER load report is discarded. If identities do not match then the PEER load report is discarded. If
the identities match then A1 saves the load information in its the identities match then A1 saves the load information in its
routing information for routing of subsequent request messages. In routing information for routing of subsequent request messages. In
both cases A1 strips the PEER load report from the message. both cases A1 strips the PEER Load report from the message.
For the HOST load report, A1's actions depend on whether A1 is For the HOST Load report, A1's actions depend on whether A1 is
responsible for doing server selection. If A1 is not doing server responsible for doing server selection. If A1 is not doing server
selection then A1 ignores the HOST load report. If A1 is responsible selection then A1 ignores the HOST Load report. If A1 is responsible
for doing server selection then it stores the load information for for doing server selection then it stores the load information for
S[n] in its routing information for the handling of subsequent S[n] in its routing information for the handling of subsequent
request messages. In both cases A1 leaves the HOST report in the request messages. In both cases A1 leaves the HOST report in the
message. message.
A1 then calculates its own load information and inserts load A1 then calculates its own load information and inserts load
information AVPs of type PEER in the message before sending the information AVPs of type PEER in the message before sending the
message to C: message to C:
C A1 A4 S[n] C A1 A4 S[n]
| | | | | | | |
|<-----| | | |<-----| | |
xxA(Load type:PEER, source:A1) xxA(Load type:PEER, source:A1)
xxA(Load type:HOST, source:S[n]) xxA(Load type:HOST, source:S[n])
Figure 5: Answer Message from A1 Figure 5: Answer Message from A1
As with A1, C processes each load report separately. As with A1, C processes each Load report separately.
For the PEER load report, C follows the same procedure as A1 for For the PEER Load report, C follows the same procedure as A1 for
determining if the Load report was received from the peer from which determining if the Load report was received from the peer from which
the report was sent and, when finding it does, stores the load the report was sent. When finding it does, C stores the load
information for use when making future routing decisions. information for use when making future routing decisions.
For the HOST load report, C saves the load information only if it is For the HOST Load report, C saves the load information only if it is
responsible for doing server selection. responsible for doing server selection.
The Load information received by all nodes is then used for routing The Load information received by all nodes is then used for routing
of subsequent request messages. of subsequent request messages.
6. Load Mechanism Procedures 6. Load Mechanism Procedures
This section defines the normative behaviors for the Load mechanism. This section defines the normative behaviors for the Load mechanism.
6.1. Reporting Node Behavior 6.1. Reporting Node Behavior
This section defines the procedures of Diameter reporting nodes that This section defines the procedures of Diameter reporting nodes that
generate load reports. generate Load reports.
6.1.1. Endpoint Reporting Node Behavior 6.1.1. Endpoint Reporting Node Behavior
A Diameter endpoint that supports the Diameter Load mechanism MUST A Diameter endpoint that supports the Diameter Load mechanism MUST
include a load report of type HOST in sufficient answer messages to include a Load report of type HOST in sufficient answer messages to
ensure that all consumers of the load information receive timely ensure that all consumers of the load information receive timely
updates. updates.
The Diameter endpoint MUST include its own DiameterIdentity in the The Diameter endpoint MUST include its own DiameterIdentity in the
SourceID AVP included in the Load AVP. SourceID AVP included in the Load AVP.
The Diameter endpoint MUST include a Load-Type AVP of type HOST in The Diameter endpoint MUST include a Load-Type AVP of type HOST in
the Load AVP. the Load AVP.
The Diameter endpoint MUST include its load value in the Value AVP in The Diameter endpoint MUST include its load value in the Load-Value
the load AVP. AVP in the Load AVP.
The LOAD value should be calculated in a way that reflects the The LOAD value should be calculated in a way that reflects the
available load independently of the weight of each server, in order available load independently of the weight of each server, in order
to accurately compare LOAD values from different nodes. Any specific to accurately compare LOAD values from different nodes. Any specific
LOAD value needs to identify the same amount of available capacity, LOAD value needs to identify the same amount of available capacity,
regardless the Diameter node that calculates the value. regardless the Diameter node that calculates the value.
The mechanism used to calculate the LOAD value that fulfils this The mechanism used to calculate the LOAD value that fulfills this
requirement is an implementation decision. requirement is an implementation decision.
The frequency of sending load reports is an implementation decision. The frequency of sending Load reports is an implementation decision.
For instance, if the only consumer of the load reports is the For instance, if the only consumer of the Load reports is the
endpoint's peer then the endpoint can choose to only include a endpoint's peer then the endpoint can choose to only include a
load report when the load of the endpoint has changed by a Load report when the load of the endpoint has changed by a
meaningful percentage. If there are consumers of the endpoint meaningful percentage. If there are consumers of the endpoint
load report other then the endpoint's peer (this will be the case Load report other then the endpoint's peer (this will be the case
if other nodes are responsible for server selection) then the if other nodes are responsible for server selection) then the
endpoint might choose to include load reports in all answer endpoint might choose to include Load reports in all answer
messages as a way of ensuring that all nodes doing server messages as a way of ensuring that all nodes doing server
selection get accurate load information. selection get accurate load information.
6.1.2. Agent Reporting Node Behavior 6.1.2. Agent Reporting Node Behavior
A Diameter agent that supports the Diameter Load mechanism MUST A Diameter Agent that supports the Diameter Load mechanism MUST
include a PEER load report in sufficient answer messages to ensure include a PEER Load report in sufficient answer messages to ensure
that all users of the load information receive timely updates. that all users of the load information receive timely updates.
The Diameter agent MUST include its own DiameterIdentity in the The Diameter Agent MUST include its own DiameterIdentity in the
SourceID AVP included in the Load AVP. SourceID AVP included in the Load AVP.
The Diameter agent MUST include a Load-Type AVP of type PEER in the The Diameter Agent MUST include a Load-Type AVP of type PEER in the
Load AVP. Load AVP.
The Diameter agent MUST include its load value in the Load-Value AVP The Diameter Agent MUST include its load value in the Load-Value AVP
in the load AVP. in the Load AVP.
The LOAD value should be calculated in a way that reflects the The LOAD value should be calculated in a way that reflects the
available load independently of the weight of each agent, in order to available load independently of the weight of each agent, in order to
accurately compare LOAD values from different nodes. Any specific accurately compare LOAD values from different nodes. Any specific
LOAD value needs to identify the same amount of available capacity, LOAD value needs to identify the same amount of available capacity,
regardless the Diameter node that calculates the value. regardless the Diameter node that calculates the value.
The mechanism used to calculate the LOAD value that fulfils this The mechanism used to calculate the LOAD value that fulfills this
requirement is an implementation decision. requirement is an implementation decision.
The frequency of sending load reports is an implementation decision. The frequency of sending Load reports is an implementation decision.
Note: In the case of peer load reports it is only necessary to Note: In the case of peer Load reports it is only necessary to
include load reports when the load value has changed by some include Load reports when the load value has changed by some
meaningful value, as long as the agent insures that all peers meaningful value, as long as the agent ensures that all peers
receive the report. It is also acceptable to include the load receive the report. It is also acceptable to include the Load
report in every answer message handled by the Diameter agent. report in every answer message handled by the Diameter Agent.
6.2. Reacting Node Behavior 6.2. Reacting Node Behavior
This section defines the behavior of Diameter nodes processing load This section defines the behavior of Diameter nodes processing Load
reports. reports.
A Diameter node MUST be prepared to process load reports of type HOST A Diameter node MUST be prepared to process Load reports of type HOST
and of type PEER, as indicated in the Load-Type AVP included in the and of type PEER, as indicated in the Load-Type AVP included in the
Load AVP received in the same answer message or from multiple answer Load AVP received in the same answer message or from multiple answer
messages. messages.
Note that the node needs to be able to handle messages with no Note that the node needs to be able to handle messages with no
load reports, messages with just a PEER load report, messages with load reports, messages with just a PEER Load report, messages with
just an HOST load report and messages with both types of load just an HOST Load report and messages with both types of Load
reports. reports.
If the Diameter node is not responsible for doing server selection If the Diameter node is not responsible for doing server selection
then it SHOULD ignore load reports of type HOST. then it SHOULD ignore Load reports of type HOST.
If the Diameter node is responsible for doing server selection then If the Diameter node is responsible for doing server selection then
it SHOULD save the load value included in the Load-Value AVP included it SHOULD save the load value included in the Load-Value AVP included
in the Load AVP of type HOST in its routing information. in the Load AVP of type HOST in its routing information.
If the Diameter node receives a Load report of type PEER then the If the Diameter node receives a Load report of type PEER then the
Diameter node MUST determine if the Load report was inserted into the Diameter node MUST determine if the Load report was inserted into the
answer message by the peer from which the message was received. This answer message by the peer from which the message was received. This
is achieved by comparing the DiameterIdentity associated with the is achieved by comparing the DiameterIdentity associated with the
connection from which the message was received with the connection from which the message was received with the
DiameterIdentity included in the SourceID AVP in the Load report. DiameterIdentity included in the SourceID AVP in the Load report.
If the Diameter node determines that the Load report of type PEER was If the Diameter node determines that the Load report of type PEER was
not received from the peer that sent or relayed the answer message not received from the peer that sent or relayed the answer message
then the node MUST ignore the Load report. then the node MUST ignore the Load report.
If the Diameter node determines that the Load report of type PEER was If the Diameter node determines that the Load report of type PEER was
received from the peer that sent or relayed the answer message then received from the peer that sent or relayed the answer message then
the node SHOULD save the load information in its routing information. the node SHOULD save the load information in its routing information.
In all cases, a Diameter Agent MUST strip all load reports of type In all cases, a Diameter Agent MUST strip all Load reports of type
peer received in answer messages. PEER received in answer messages.
Note: This ensures that there will be precisely one load report of Note: This ensures that there will be precisely one Load report of
type peer, that of the Diameter node sending the message, in any type PEER, that of the Diameter node sending the message, in any
answer messages sent by the Diameter agent. answer messages sent by the Diameter Agent.
How a Diameter node uses load information for making routing How a Diameter node uses load information for making routing
decisions is an implementation decision. However, the distribution decisions is an implementation decision. However, the distribution
algorithm MUST result in similar behavior as the algorithm described algorithm MUST result in similar behavior as the algorithm described
for the use of weigth values in [RFC2782]. for the use of weight values in [RFC2782].
6.3. Extensibility 6.3. Extensibility
The Load mechanism can be extended to include additional information The Load mechanism can be extended to include additional information
in the load reports. in the Load reports.
Any extension may define new AVPs for use in Load reports. These new Any extension may define new AVPs for use in Load reports. These new
AVPs SHOULD be defined to be extensions to the Load AVPs defined in AVPs SHOULD be defined to be extensions to the Load AVPs defined in
this document. this document.
[RFC6733] defined Grouped AVP extension mechanisms apply. This [RFC6733] defined Grouped AVP extension mechanisms apply. This
allows, for example, defining a new feature that is mandatory to be allows, for example, defining a new feature that is mandatory to be
understood even when piggybacked on an existing application. understood even when piggybacked on an existing application.
As with any Diameter specification, [RFC6733] requires all new AVPs As with any Diameter specification, [RFC6733] requires all new AVPs
to be registered with IANA. See Section 9 for the required to be registered with IANA. See Section 9 for the required
procedures. procedures.
6.4. Addition and removal of Nodes 6.4. Addition and Removal of Nodes
When a Diameter node is added, the new node will start by advertising When a Diameter node is added, the new node will start by advertising
its load. Downstream nodes will need to factor the new load its load. Downstream nodes will need to factor the new load
information into load balancing decisions. The downstream nodes can information into load balancing decisions. The downstream nodes can
attempt to ensure a smooth increase of the traffic to the new node, attempt to ensure a smooth increase of the traffic to the new node,
avoiding an immediate spike of traffic to the new node. The method avoiding an immediate spike of traffic to the new node. The method
for handling of such a smooth increase is implementation specific but for handling of such a smooth increase is implementation specific but
it can rely on the evolution of load information received from the it can rely on the evolution of load information received from the
new node and from the other nodes. new node and from the other nodes.
skipping to change at page 14, line 26 skipping to change at page 14, line 34
[ Load-Value ] [ Load-Value ]
[ SourceID ] [ SourceID ]
* [ AVP ] * [ AVP ]
7.2. Load-Type AVP 7.2. Load-Type AVP
The Load-Type AVP (AVP code TBD2) is of type Enumerated. It is used The Load-Type AVP (AVP code TBD2) is of type Enumerated. It is used
to convey the type of Diameter node that sent the load information. to convey the type of Diameter node that sent the load information.
The following values are defined: The following values are defined:
HOST 0 The load report is for a host. HOST 0 The Load report is for a host.
PEER 1 The load report is for a peer. PEER 1 The Load report is for a peer.
7.3. Load-Value AVP 7.3. Load-Value AVP
The Load-Value AVP (AVP code TBD3) is of type Unsigned64. It is used The Load-Value AVP (AVP code TBD3) is of type Unsigned64. It is used
to convey relative load information about the sender of the load to convey relative load information about the sender of the Load
report. report.
The Load-Value AVP is specified in a manner similar to the weight The Load-Value AVP is specified in a manner similar to the weight
value in DNS SRV ([RFC2782]). value in DNS SRV ([RFC2782]).
The Load-Value has a range of 0-65535. The Load-Value has a range of 0-65535.
A higher value indicates a lower load on the sending node. A lower A higher value indicates a lower load on the sending node. A lower
value indicates that the sending node is heavily loaded. value indicates that the sending node is heavily loaded.
skipping to change at page 15, line 41 skipping to change at page 15, line 45
8. Security Considerations 8. Security Considerations
Load information may be sensitive information in some cases. Load information may be sensitive information in some cases.
Depending on the mechanism, an unauthorized recipient might be able Depending on the mechanism, an unauthorized recipient might be able
to infer the topology of a Diameter network from load information. to infer the topology of a Diameter network from load information.
Load information might be useful in identifying targets for Denial of Load information might be useful in identifying targets for Denial of
Service (DoS) attacks, where a node known to be already heavily Service (DoS) attacks, where a node known to be already heavily
loaded might be a tempting target. Load information might also be loaded might be a tempting target. Load information might also be
useful as feedback about the success of an ongoing DoS attack. useful as feedback about the success of an ongoing DoS attack.
Given that routing decisions are impacted by load information, there
is potential for negative impacts on a Diameter network caused by
erroneous or malicious load reports. This includes the malicious
changing of load values by Diameter Agents.
Any load information conveyance mechanism will need to allow Any load information conveyance mechanism will need to allow
operators to avoid sending load information to nodes that are not operators to avoid sending load information to nodes that are not
authorized to receive it. Since Diameter currently only offers authorized to receive it. Since Diameter currently only offers
authentication of nodes at the transport level, any solution that authentication of nodes at the transport level, any solution that
sends load information to non-peer nodes might require a transitive- sends load information to non-peer nodes requires a transitive-trust
trust model. model.
9. IANA Considerations 9. IANA Considerations
9.1. AVP Codes 9.1. AVP Codes
New AVPs defined by this specification are listed in New AVPs defined by this specification are listed in
Section Section 7. All AVP codes are allocated from the Section Section 7. All AVP codes are allocated from the
'Authentication, Authorization, and Accounting (AAA) Parameters' AVP 'Authentication, Authorization, and Accounting (AAA) Parameters' AVP
Codes registry. Codes registry.
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