draft-ietf-dime-load-02.txt   draft-ietf-dime-load-03.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: September 19, 2016 JJ. Trottin Expires: March 31, 2017 JJ. Trottin
Nokia Nokia
March 18, 2016 September 27, 2016
Diameter Load Information Conveyance Diameter Load Information Conveyance
draft-ietf-dime-load-02 draft-ietf-dime-load-03
Abstract Abstract
This document defines a mechanism for sharing of Diameter load This document defines a mechanism for conveying of Diameter load
information. [RFC7068] describes requirements for Overload Control information. [RFC7068] describes requirements for Overload Control
in Diameter. This includes a requirement to allow Diameter nodes to in Diameter. This includes a requirement to allow Diameter nodes to
send "load" information, even when the node is not overloaded. The send "load" information, even when the node is not overloaded. The
Diameter Overload Information Conveyance (DOIC) [RFC7683] solution Diameter Overload Information Conveyance (DOIC) [RFC7683] solution
describes a mechanism meeting most of the requirements, but does not describes a mechanism meeting most of the requirements, but does not
currently include the ability to send load information. currently include the ability to send 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
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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 September 19, 2016. This Internet-Draft will expire on March 31, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
3. Conventions Used in This Document . . . . . . . . . . . . . . 4 3. Conventions Used in This Document . . . . . . . . . . . . . . 4
4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
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 . . . . . . . . . . . . . . . . . . . 7 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. Receiving Node Behavior . . . . . . . . . . . . . . . . . 11 6.2. Receiving Node Behavior . . . . . . . . . . . . . . . . . 12
6.3. Extensibility . . . . . . . . . . . . . . . . . . . . . . 12 6.3. Extensibility . . . . . . . . . . . . . . . . . . . . . . 13
6.4. Addition and removal of Nodes . . . . . . . . . . . . . . 13
7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 13 7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 13
7.1. Load AVP . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Load AVP . . . . . . . . . . . . . . . . . . . . . . . . 13
7.2. Load-Type AVP . . . . . . . . . . . . . . . . . . . . . . 13 7.2. Load-Type AVP . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Load-Value AVP . . . . . . . . . . . . . . . . . . . . . 13 7.3. Load-Value AVP . . . . . . . . . . . . . . . . . . . . . 14
7.4. SourceID AVP . . . . . . . . . . . . . . . . . . . . . . 14 7.4. SourceID AVP . . . . . . . . . . . . . . . . . . . . . . 14
7.5. Attribute Value Pair flag rules . . . . . . . . . . . . . 14 7.5. Attribute Value Pair flag rules . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 15 9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 15
9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 15 9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . 15 10.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Topology Scenarios . . . . . . . . . . . . . . . . . 16 Appendix A. Topology Scenarios . . . . . . . . . . . . . . . . . 16
A.1. No Agent . . . . . . . . . . . . . . . . . . . . . . . . 16 A.1. No Agent . . . . . . . . . . . . . . . . . . . . . . . . 16
A.2. Single Agent . . . . . . . . . . . . . . . . . . . . . . 16 A.2. Single Agent . . . . . . . . . . . . . . . . . . . . . . 17
A.3. Multiple Agents . . . . . . . . . . . . . . . . . . . . . 17 A.3. Multiple Agents . . . . . . . . . . . . . . . . . . . . . 17
A.4. Linked Agents . . . . . . . . . . . . . . . . . . . . . . 18 A.4. Linked Agents . . . . . . . . . . . . . . . . . . . . . . 18
A.5. Shared Server Pools . . . . . . . . . . . . . . . . . . . 19 A.5. Shared Server Pools . . . . . . . . . . . . . . . . . . . 19
A.6. Agent Chains . . . . . . . . . . . . . . . . . . . . . . 19 A.6. Agent Chains . . . . . . . . . . . . . . . . . . . . . . 20
A.7. Fully Meshed Layers . . . . . . . . . . . . . . . . . . . 20 A.7. Fully Meshed Layers . . . . . . . . . . . . . . . . . . . 20
A.8. Partitions . . . . . . . . . . . . . . . . . . . . . . . 20 A.8. Partitions . . . . . . . . . . . . . . . . . . . . . . . 21
A.9. Active-Standby Nodes . . . . . . . . . . . . . . . . . . 20 A.9. Active-Standby Nodes . . . . . . . . . . . . . . . . . . 21
A.10. Addition and removal of Nodes . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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 24, which requires a In particular, DOIC does not fulfill Req 23 and Req 24:
mechanism where Diameter nodes can indicate their current load, even
if they are not currently overloaded. DOIC also does not fulfill Req REQ 23: The solution MUST provide sufficient information to enable
23, which requires that nodes that divert traffic away from a load-balancing node to divert messages that are rejected or
overloaded nodes be provided with sufficient information to select otherwise throttled by an overloaded upstream node to other
targets that are most likely to have sufficient capacity. upstream nodes that are the most likely to have sufficient
capacity to process them.
REQ 24: The solution MUST provide a mechanism for indicating load
levels, even when not in an overload condition, to assist nodes in
making decisions to prevent overload conditions from occurring.
There are several other requirements in [RFC7068] that mention both There are several other requirements in [RFC7068] that mention both
overload and load information that are only partially fulfilled by overload and load information that are only partially fulfilled by
DOIC. DOIC.
The DIME working group explicitly chose not to fulfill these The DIME working group explicitly chose not to fulfill these
requirements in DOIC due to several reasons. A principal reason was requirements in DOIC due to several reasons. A principal reason was
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
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requirements from RFC 7068. requirements from RFC 7068.
2. Terminology and Abbreviations 2. Terminology and Abbreviations
DOIC DOIC
Diameter Overload Information Conveyance ([RFC7683]) Diameter Overload Information Conveyance ([RFC7683])
Load Load
The relative capacity of a Diameter node. A low load level The he relative usage of the Diameter message processing capacity
indicates that the Diameter node is under utilized. A high load of a Diameter node. A low load level indicates that the Diameter
level indicates that the node is closer to being fully utilized. node is under utilized. A high load level indicates that the node
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, Reacting Node
Reporting node and reacting node terminology is defined in Reporting node and reacting node terminology is defined in
[RFC7683]. [RFC7683].
Routing Information Routing Information
Routing Information - Routing information referred to in this Routing Information referred to in this document can include the
document can include the Routing and Peer tables defined in RFC Routing and Peer tables defined in RFC 6733. It can also include
6733. It can also include other implementation specific tables other implementation specific tables used to store load
used to store load information. This document does not define the information. This document does not define the structure of such
structure of such tables. tables.
3. Conventions Used in This Document 3. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
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 had 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, in the opinion of the
authors, there are two primary differences. First, a Diameter node authors, there are two primary differences. First, a Diameter node
always has a load. At any given time that load maybe effectively always has a load. At any given time that load may be effectively
zero, effectively fully loaded, or somewhere in between. In zero, effectively fully loaded, or somewhere in between. In
contrast, overload is an exceptional condition. A node only has contrast, overload is an exceptional condition. A node only has
overload information when it is in an overloaded state. Furthermore, overload information when it is in an overloaded state. Furthermore,
the relationship between a node's load level and overload state at the relationship between a node's load level and overload state at
any given time may be vague. For example, a node may normally any given time may be vague. For example, a node may normally
operate at a "fully loaded" level, but still not be considered operate at a "fully loaded" level, but still not be considered
overloaded. Another node may declare itself to be "overloaded" even overloaded. Another node may declare itself 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 reduce 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 or to an indicated level. made -- by an indicated amount (by default), or as prescribed by the
Effectively, DOIC provides a contract between the reporting node and selected abatement algorithm. Effectively, DOIC provides a contract
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
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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
greater potential to drive other nodes into overload. greater potential to drive other nodes into overload.
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. A the first place. Normal load-balancing falls into this category, but
node might also take other proactive steps to reduce offered load the diameter node can take other proactive steps as well.
based on load information, so that the loaded node never goes into
overload in the first place.
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 are most server-to-client transactions), both of these uses of load
effectively accomplished by a Diameter node that performs server information should be accomplished by a Diameter node that performs
selection. Typically, server selection is performed by a node (a server selection. Typically, server selection is performed by a node
client or an agent) that is an immediate peer of the server. (a client or an agent) that is an immediate peer of the server.
However, there are scenarios (see Appendix A) where a client or proxy However, there are scenarios (see Appendix A) where a client or proxy
that is not the immediate peer to the selected servers performs that is not the immediate peer to the selected servers performs
server selection. In this case, the client or proxy enforces the server selection. In this case, the client or proxy enforces the
server selection by inserting a Destination-Host AVP. 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.
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There are two primary differences. First, there is no capability There are two primary differences. First, there is no capability
negotiation process for load. The sender of the load information is negotiation process for load. The sender of the load information is
sending it with the expectation that any supporting nodes will use it sending it with the expectation that any supporting nodes will use it
when making routing decisions. If there are no nodes that support when making routing decisions. If there are no nodes that support
the Load mechanism then the load information is ignored. the Load mechanism then the load information is ignored.
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. The DOIC overload reports much remain in the message information, although only one node actually comsumes and reacts to
all the way from the reporting node to the node that is the target the report. The DOIC overload reports remain in the message all the
for the answer message. way from the reporting node to the node that is the target for the
answer message.
For the Load mechanism there are two types of load reports. For the Load mechanism there are two types of load reports and only
the first one is transmitted end-to-end.
The first is the load of the endpoint sending the answer message. The first is the load of the endpoint sending the answer message.
This load report is carried end-to-end to enable any nodes that make This load report is carried end-to-end to enable any nodes that make
server selection decisions to use the load status of the sending server selection decisions to use the load status of the sending
endpoint as part of the server selection decision. endpoint as part of 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, do not have significance beyond the peer Diameter node and, as such, does not have significance beyond the
node. These load reports are removed by the first supporting peer node. These load reports are removed by the first supporting
Diameter node to receive the report. 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 the relative load of the sending node. This The load report includes a value indicating the load of the sending
relative load is specified in a manner consistent with that defined node relative load of the sending node, specified in a manner
for DNS SRV [RFC2782]. consistent with that defined for DNS SRV [RFC2782].
The goal is make it possible to use both the load values received as The goal is to make it possible to use both the load values received
a part of the Diameter Load mechanism and weight values received as a as a part of the Diameter Load mechanism and weight values received
result of a DNS SRV query. As a result, the Diameter load value has as a result of a DNS SRV query. As a result, the Diameter load value
a range of 0-65535. This value and DNS SRV weight values are then has a range of 0-65535. This value and DNS SRV weight values are
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 as the algorithm specified in [RFC2782]. result in similar behavior to the algorithm described for the use of
weigh 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 nodes load. load information have a sufficiently accurate view of the node's
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.
For this discussion, assume the following Diameter network For this discussion, assume the following Diameter network
configuration: configuration:
---A1---A3----S[1], S[2]...S[p] ---A1---A3----S[1], S[2]...S[p]
skipping to change at page 8, line 27 skipping to change at page 8, line 35
following path: following path:
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 it's 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 it will verify that the If Agent A4 supports the Load mechanism then A4's actions depend on
load information received is valid. For a HOST load report this is whether A4 is responsible for doing server selection. If A4 is not
achieved by matching the identity included in the load information doing server selection then A4 ignores the HOST load report. If A4
with the identity of the host node from which the answer message was is responsible for doing server selection then it stores the load
received. information for S[n] in its routing information for the handling of
subsequent request messages. In both cases A4 leaves the HOST report
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.
If the identity included in the load information AVPs matches the
identity of the host from which the load information is received then
Agent A4 stores the load information for S[n] in its routing
information.
Because the load report is an HOST load report, A4 leaves the load
report in the message it relays.
A4 then calculates its own load information and inserts load A4 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 A1: message to A1.
C A1 A4 S[n] C A1 A4 S[n]
| | | | | | | |
| |<-----| | | |<-----| |
| 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
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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 A1: 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.
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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 it's own DiameterIdentity in the The Diameter endpoint MUST include its own DiameterIdentity in the
Source-ID 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 Value AVP in
the load AVP. the load AVP.
The method for determining the load value included in the load report The LOAD value should be calculated in a way that reflects the
is an implementation decision. available load independently of the weight of each server, in order
to accurately compare LOAD values from different nodes. Any specific
LOAD value needs to identify the same amount of available capacity,
regardless the Diameter node that calculates the value.
The mechanism used to calculate the LOAD value that fulfils this
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
endpoints peer then the endpoint can choose to only include a load endpoint's peer then the endpoint can choose to only include a
report when the load of the endpoint has changed by a meaningful load report when the load of the endpoint has changed by a
percentage. If there are consumers of the endpoint load report meaningful percentage. If there are consumers of the endpoint
other then the endpoints peer (this will be the case if other load report other then the endpoint's peer (this will be the case
nodes are responsible for server selection) then the endpoint if other nodes are responsible for server selection) then the
might choose to include load reports in all answer messages as a endpoint might choose to include load reports in all answer
way of ensuring that all nodes doing server selection get accurate messages as a way of ensuring that all nodes doing server
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 it's own DiameterIdentity in the The Diameter agent MUST include its own DiameterIdentity in the
Source-ID 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 Value AVP in The Diameter agent MUST include its load value in the Load-Value AVP
the load AVP. in the load AVP.
The method for determining the load value included in the load report The LOAD value should be calculated in a way that reflects the
is an implementation decision. available load independently of the weight of each agent, in order to
accurately compare LOAD values from different nodes. Any specific
LOAD value needs to identify the same amount of available capacity,
regardless the Diameter node that calculates the value.
The mechanism used to calculate the LOAD value that fulfils this
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 insures 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. Receiving Node Behavior 6.2. Receiving Node Behavior
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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 Value AVP included in it SHOULD save the load value included in the Load-Value AVP included
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 Source-ID 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.
How a Diameter node uses load information for making routing How a Diameter node uses load information for making routing
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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
When a Diameter node is added, the new node will start by advertising
its load. Downstream nodes will need to factor the new load
information into load balancing decisions. The downstream nodes can
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
for handling of such a smooth increase is implementation specific but
it can rely on the evolution of load information received from the
new node and from the other nodes.
When removing a node in a controlled way (e.g. for maintenance
purpose, so outside a failure case), it might be appropriate to
progressively reduce the traffic to this node by routing traffic to
other nodes. Simple load information (load percentage) would not be
sufficient. The method for handling of the node removal is
implementation specific but it can rely on the evolution of the load
information received from the node to be removed.
7. Attribute Value Pairs 7. Attribute Value Pairs
The section defines the AVPs required for the Load mechanism. The section defines the AVPs required for the Load mechanism.
7.1. Load AVP 7.1. Load AVP
The Load AVP (AVP code TBD1) is of type Grouped and is used to convey The Load AVP (AVP code TBD1) is of type Grouped and is used to convey
load information between Diameter nodes. load information between Diameter nodes.
Load ::= < AVP Header: TBD1 > Load ::= < AVP Header: TBD1 >
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[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000, DOI 10.17487/RFC2782, February 2000,
<http://www.rfc-editor.org/info/rfc2782>. <http://www.rfc-editor.org/info/rfc2782>.
Appendix A. Topology Scenarios Appendix A. Topology Scenarios
This section presents a number of Diameter topology scenarios, and This section presents a number of Diameter topology scenarios, and
discusses how load information might be used in each scenario. discusses how load information might be used in each scenario.
Nothing in this section should be construed to mean that a given
scenario is in scope for this effort, or even a good idea. Some
scenarios might be considered as not relevant in practice and
subsequently discarded.
A.1. No Agent A.1. No Agent
Figure 6 shows a simple client-server scenario, where a client picks Figure 6 shows a simple client-server scenario, where a client picks
from a set of candidate servers available for a particular realm and from a set of candidate servers available for a particular realm and
application. The client selects the server for a given transaction application. The client selects the server for a given transaction
using the load information received from each server. using the load information received from each server.
------S1 ------S1
/ /
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The previous scenarios assume that traffic can be load balanced among The previous scenarios assume that traffic can be load balanced among
all peers that are eligible to handle a request. That is, the peers all peers that are eligible to handle a request. That is, the peers
operate in an "active-active" configuration. In an "active-standby" operate in an "active-active" configuration. In an "active-standby"
configuration, traffic would be load-balanced among active peers. configuration, traffic would be load-balanced among active peers.
Requests would only be sent to peers in a "standby" state if the Requests would only be sent to peers in a "standby" state if the
active peers became unavailable. For example, requests might be active peers became unavailable. For example, requests might be
diverted to a stand-by peer if one or more active peers becomes diverted to a stand-by peer if one or more active peers becomes
overloaded. overloaded.
A.10. Addition and removal of Nodes
When a Diameter node is added, the new node will start by advertising
its load. Downstream nodes will need to factor the new load
information into load balancing decisions. The downstream nodes
should attempt to ensure a smooth increase of the traffic to the new
node, avoiding an immediate spike of traffic to the new node. The
handling of such a smooth increase is implementation specific but it
can rely on the evolution of load information received from the new
node and from the other nodes.
When removing a node in a controlled way (e.g. for maintenance
purpose, so outside a failure case), it might be appropriate to
progressively reduce the traffic to this node by routing traffic to
other nodes. Simple load information (load percentage) would be not
sufficient. The handling of the node removal is implementation
specific but it can rely on the evolution of the load information
received from the node to be removed
Authors' Addresses Authors' Addresses
Ben Campbell Ben Campbell
Oracle Oracle
7460 Warren Parkway # 300 7460 Warren Parkway # 300
Frisco, Texas 75034 Frisco, Texas 75034
USA USA
Email: ben@nostrum.com Email: ben@nostrum.com
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