Diameter Maintenance and Extensions J. Korhonen
(DIME) Renesas Mobile
Internet-Draft H. Tschofenig, Ed.
Intended status: Standards Track Nokia Siemens Networks
Expires: August 29, 2013 February 25, 2013
The Diameter Overload Control Application (DOCA)
draft-korhonen-dime-ovl-01.txt
Abstract
This specification documents a Diameter Overload Control Application
(DOCA), which uses the normal Diameter application approach for the
capability negotiation, propagation and management of Diameter
overload control information between Diameter nodes.
Status of this Memo
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This Internet-Draft will expire on August 29, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DOCA Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
4. DOCA Commands . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 6
5.1. OC-Information AVP . . . . . . . . . . . . . . . . . . . . 6
5.2. OC-Scope AVP . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. OC-Applications AVP . . . . . . . . . . . . . . . . . . . 8
5.4. OC-Action AVP . . . . . . . . . . . . . . . . . . . . . . 9
5.5. OC-Algorithm AVP . . . . . . . . . . . . . . . . . . . . . 9
5.6. OC-Level AVP . . . . . . . . . . . . . . . . . . . . . . . 10
5.7. OC-Utilization AVP . . . . . . . . . . . . . . . . . . . . 11
5.8. OC-Tocl AVP . . . . . . . . . . . . . . . . . . . . . . . 11
5.9. OC-Sending-Rate AVP . . . . . . . . . . . . . . . . . . . 11
5.10. OC-Best-Before AVP . . . . . . . . . . . . . . . . . . . . 12
5.11. OC-Origin AVP . . . . . . . . . . . . . . . . . . . . . . 12
5.12. OC-Priority AVP . . . . . . . . . . . . . . . . . . . . . 12
5.13. Attribute Value Pair flag rules . . . . . . . . . . . . . 13
6. Transport Considerations . . . . . . . . . . . . . . . . . . . 13
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. Application Identifiers . . . . . . . . . . . . . . . . . 15
8.2. SCTP Payload Protocol Identifier . . . . . . . . . . . . . 15
8.3. Command Codes . . . . . . . . . . . . . . . . . . . . . . 15
8.4. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 15
8.5. Result-Code Values . . . . . . . . . . . . . . . . . . . . 15
8.6. New Registries . . . . . . . . . . . . . . . . . . . . . . 16
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. Design Justification . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
The existing toolbox offered by the Diameter Base Protocol [RFC6733]
to prevent and recover from signaling overload situations is rather
limited. Apart from out-of-band altering of the transport connection
congestion control behavior or other non-standard application level
throttling, the protocol error DIAMETER_TOO_BUSY, the permanent error
DIAMETER_UNABLE_TO_COMPLY (for some unspecified reason) and the
Disconnect-Cause Attribute Value Pair (AVP) code BUSY or
DO_NOT_WANT_TO_TALK_TO_YOU are more or less all there is.
Unfortunately, the mentioned three indications are coarse, concern
one peer connection at a time or lack detailed information for
problem diagnosis and mitigation. They also treat all applications
in a single Diameter node (identified by a single DiameterIdentity)
as a lump. There is no way communicate any kind of grouping of
applications or what is the scope/partitioning of the delivered
information. Furthermore, there is no way to signal when the
overload situation is over. The request initiator and forwarders are
therefore forced to keep re-submitting their messages to determine
whether the situation has changed.
The situation is further complicated by the hop-by-hop nature of
Diameter deployments. This makes the propagation of possible
overload situation information non-trivial, even for existing
protocol errors since every intermediate Diameter node is allowed to
react to the error situation. Either the information is never
propagated to the originator of the request or it takes an
unacceptable long time.
A problem statement of overload control for Diameter and requirements
are documented in [I-D.ietf-dime-overload-reqs]. This specification
describes a solution to the Diameter overload Diameter Overload
Control Application (DOCA), which fulfills the requirements of
[I-D.ietf-dime-overload-reqs] and defines a Diameter application to
convey overload information between Diameter nodes.
Note: The recent publication of
[I-D.campbell-dime-overload-data-analysis] illustrates the overload
information data model and the design space. As the working group
makes progress in deciding about specific features this document will
be updated accordingly.
2. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. DOCA Overview
Any the DOCA capable Diameter node MAY initiate a DOCA-Report-Request
at any given time. The receiver of the DOCA-Report-Request
acknowledges with a DOCA-Report-Answer and includes the Result-Code
AVP indicating whether it could honor the action/report in the
request. The DOCA-Report-Answer SHOULD also piggyback overload
control information.
A DOCA client MUST set the Auth-Session-State AVP to the value
NO_STATE_MAINTAINED and SHOULD include the OC-Information AVP with
overload information into the DOCA-Report-Request, if available. The
DOCA-Report-Response message MUST contain the Auth-Session-State AVP
set to value NO_STATE_MAINTAINED.
Note that information exchanges regarding various DOCA related timers
serve only as a hint since they cannot be enforced. Consequently,
care should be taken not to send DOCA-Report-Requests too frequently.
When a Diameter node receives overload control information and is
also requested to act on it, the DOCA functionality is applied to all
specified applications within a given scope. How the Diameter node
accomplishes the node wide DOCA action enforcement is implementation
specific.
When a Diameter node receives (interim) overload information but the
overload condition has not exceeded a certain threshold, then the
receiver is not required to act based on the received information.
However, it is RECOMMENDED that the receiver makes proactive actions
to avoid entering the overload condition based on the newly received
overload information.
There may be zero or more intermediate Diameter agents on the path
between the DOCA client and the DOCA server. Understanding the DOCA
functionality is not expected from relays and redirect agents. A
Diameter proxy, which obviously understands the DOCA application, MAY
inspect the DOCA related AVPs in the DOCA-Report-Request/Answer
message pair and depending on the value of the OC-Scope AVP (see
Section 5.2) inject its own information. A proxy is always
RECOMMENDED to react according to the overload information when it
comes to, for example, peer selection and traffic throttling.
When a Diameter agent receives overload control information and is
also requested to act on it, the DOCA functionality is applied to all
specified applications within a given scope. How the Diameter agent
accomplishes the node wide DOCA action enforcement is implementation
specific.
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4. DOCA Commands
The DOCA-Report-Request (DRR) message is used to report overload
condition information. The message can be originated as a result of
emerging overload condition or as a periodic unsolicited report.
<DOCA-Report-Request> ::= < Diameter Header: TBD2, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Request-Type }
{ Destination-Host }
[ Auth-Session-State ]
* [ Class ]
[ Origin-State-Id ]
* [ Proxy-Info ]
* [ Route-Record ]
{ OC-Scope }
[ OC-Algorithm ]
[ OC-Action ]
[ OC-Tocl ]
[ OC-Applications ]
* [ OC-Information ]
* [ AVP ]
The DOCA-Report-Answer (DRA) message is used as a response to the
DOCA-Report-Request. The message MAY piggyback overload condition
information in order to avoid unnecessary DOCA-Report-Request
messages to the reverse direction.
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<DOCA-Report-Answer> ::= < Diameter Header: TBD2, PXY >
< Session-Id >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
[ Auth-Session-State ]
* [ Class ]
[ Error-Message ]
[ Error-Reporting-Host ]
[ Failed-AVP ]
[ Origin-State-Id ]
* [ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
{ OC-Scope }
[ OC-Action ]
* [ OC-Information ]
* [ AVP ]
5. Attribute Value Pairs
5.1. OC-Information AVP
The OC-Information AVP (AVP Code TBD3) is of type Grouped and
contains a set AVPs that identify the source of the overload control
information (the OC-Origin AVP), the overload information itself and
which applications the information concerns.
OC-Information ::= < AVP Header: TBD3 >
{ OC-Origin }
{ OC-Best-Before }
[ OC-Level ]
[ OC-Algorithm ]
[ OC-Sending-Rate ]
[ Vendor-Id ]
[ OC-Applications ]
[ Product-Name ]
[ OC-Utilization ]
[ OC-Priority ]
* [ AVP ]
Diameter proxies on path MAY add one or more OC-Information AVPs into
the DOCA-Report-Request/answer messages.
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5.2. OC-Scope AVP
The OC-Scope (AVP Code TBD4) is of type Unsigned32 and contains the
scope where and concerning what the overload control information can
be injected. The OC-Scope is formatted as a vector of scope flag
bits. The following scopes are supported:
Host scope (0x00000001)
The OC-Information AVP concerns only a single host within a realm
(which internally MAY represent of pool).
Realm scope (0x00000002)
The OC-Information AVP concerns a realm. No specific hosts are
identified.
Only origin realm (0x00000004)
The OC-Information AVP can only be included by a Diameter node on
the path that has the same Origin-Realm as the DOCA client.
Application information (0x00010000)
The OC-Information AVP MAY contain application related information
(the OC-Applications AVP).
Node utilization information (0x00020000)
The OC-Information AVP MAY contain node wide load related
information (the OC-Utilization AVP).
Application priorities (0x00040000)
The OC-Information AVP SHOULD priority information (the OC-
Priority AVP) so when the overload condition is on, Diameter nodes
are able to prioritize between different applications, for
example, when dropping or throttling messages.
Any other value is reserved.
A scope is active when a corresponding flag is set in the OC-Scope
AVP. During the initialization state a DOCA client includes those
scopes it supports and is interested in. A DOCA server then returns
the scope that it has in common with the DOCA client (and intends to
use). The common scopes are then used during the established state.
Note that some scope combinations make little sense while still being
valid. The general guide when multiple scopes collide is that the
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least restrictive wins.
A sender of the overload information MUST adhere to the scope it
announces regarding the information it itself sends.
If a DOCA server does not have a common scope with a DOCA client or
the DOCA server cannot agree on one based on a local policy, then the
DOCA server MUST send the DOCA-Report-Answer indicating an error and
set the Result-Code to the DIAMETER_NO_COMMON_SCOPE value.
5.3. OC-Applications AVP
The OC-Applications (AVP Code TBD5) is of type Grouped and contains a
list of Application-IDs of interest when found in the DOCA-Report-
Request/Answer command main level and meant to be used during the
initialization state to agree on the common set of supported
applications of monitoring interest. When used within the OC-
Information AVP, the OC-Applications AVP identify those applications
the overload information concerns. The OC-Applications AVPs on the
command main level and inside the OC-Information AVP MUST NOT have
conflicting views of the applications of interest. However, the OC-
Applications AVP can be see as a superset of applications i.e., not
all applications of interest need to be included every time into the
OC-Information AVP.
OC-Applications ::= < AVP Header: TBD3 >
* [ Auth-Application-Id ]
* [ Acct-Application-Id ]
* [ Vendor-Specific-Application-Id ]
* [ AVP ]
The absence of the OC-Applications AVP indicates the Diameter node
has no specific preference or interest in specific applications. The
overload information is then signaled as concerning the whole
Diameter node. This default behavior is useful when the DOCA does
not maintain session state. If there are no common applications,
then the DOCA-Report-Answer MUST contain the Result-Code with the
DIAMETER_NO_COMMON_APPLICATION value.
When the DOCA maintains state, there is no need to include the OC-
Applications AVP into the DOCA-Report-Request/Answer command main
level after the initial message exchange. The agreed common set of
application is expected to be known by both DOCA client and server
throughout the session lifetime.
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5.4. OC-Action AVP
The OC-Action (AVP Code TBD6) is of type OctetString and size of one
octet. The octet has the following three possible values:
Start (1)
Signals the start of the overload condition. This implies the
receiver is requested to act according to the information found in
the OC-Information.
Stop (2)
Signals the end of the overload condition.
Interim (3)
Updates the overload information. The interim can be sent during
the overload condition or during the normal condition. This is
the default value.
Any other value is reserved.
5.5. OC-Algorithm AVP
The OC-Algorithm (AVP Code TBD7) is of type Unsigned32. The contains
supported 'algorithms' to mitigate the overload condition. The OC-
Algorithm AVP is formatted as a vector of algorithm flag bits. The
following 'algorithms' are supported:
Drop (0x00000001)
Messages are plain dropped. It is RECOMMENDED to drop messages
selectively based, for example, on application priorities. This
is the default algorithm.
Throttle (0x00000002)
The message sending rate is according to the OC-Sending-Rate AVP.
Prioritize (0x00000004)
Apply priorities among applications and the other used means for
holding traffic.
Any other value is reserved.
The 'algorithms' are only applied at a Diameter node when the
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overload condition has been signaled.
During the initialization state a DOCA client includes those
algorithms it supports and is interested in. A DOCA server then
returns the algorithm that it has in common with the DOCA client (and
intends to use). One or more common algorithms are then used during
the established state.
If a DOCA server does not have a common algorithm with a DOCA client
or the DOCA server cannot agree on one based on a local policy, then
the DOCA server MUST send the DOCA-Report-Answer indicating an error
and set the Result-Code to the DIAMETER_NO_COMMON_ALGORITHM value.
5.6. OC-Level AVP
The OC-Level (AVP Code TBD8) is of type OctetString and size of one
octet. The octet has the following five possible values:
Normal (1)
Everything is in control. Meaningful only when the OC-Action is
set to 'Interim' since when the overload condition level is
considered normal, the overload condition SHOULD be stopped. This
is the default value.
Raising (2)
There is a sign of increasing load.
Alarming (3)
The overload condition is reaching the level where quick measures
SHOULD be done to mitigate the overload condition.
Panic (4)
The overload condition is severe. Apply any measure to mitigate
the overload condition but still allowed to send messages.
Hold (5)
Do not send any messages, please. When this level is signaled,
the OC-Best-Before time SHOULD NOT be respected but an explicit
overload condition stop has to be received (with an exception the
Diameter node realizes its other end has rebooted or otherwise
lost its state).
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Switch servers (6)
Do not talk to me again. When this level is signaled, the DOCA
client MUST switch to an alternative server.
Any other value is reserved.
If the receiver cannot agree on or does not understand the OC-Level
AVP value, the an error MUST be returned with the Result-Code AVP set
to the value DIAMETER_INVALID_AVP_VALUE and the Failed-AVP AVP
containing the OC-Level AVP.
5.7. OC-Utilization AVP
The OC-Utilization (AVP Code TBD9) is of type Float32 and tells the
overall utilization level percentage of the Diameter node. Values
between 0.0 to 100.0 are valid.
5.8. OC-Tocl AVP
The OC-Tocl (AVP Code TBD10) is of type Unsigned32 and tells the Tolc
timer value in milliseconds. This timer defines the interval for
sending periodic DOCA-Report-Request messages with the OC-Action AVP
set to 'Interim'. The value of zero (0) means no periodic DOCA-
Report-Request messages are sent or desired. The default value is
120000.
The OC-Tocl AVP can be considered as a hint for a desired sending
rate of subsequent messages.
If a DOCA server find the Tocl value proposed by a DOCA client either
too small (i.e. too frequent periodic messages) or too big (i.e. too
seldom periodic messages), then the DOCA server MUST send the DOCA-
Report-Answer indicating an error and set the Result-Code either to
the DIAMETER_TOCL_TOO_SMALL or DIAMETER_TOCL_TOO_BIG value.
5.9. OC-Sending-Rate AVP
The OC-Sending-Rate (AVP Code TBD11) is of type Float32 and tells the
the maximum Diameter message sending rate per second the sender of
this information wishes to receive Diameter messages. Only positive
values are valid. A value of zero (0.0) of the absence of this AVP
means the information sender has no specific rate preference.
If a DOCA server finds the sending rate value proposed by a DOCA
client too big (i.e., too frequent periodic messages), then the DOCA
server MUST send the DOCA-Report-Answer indicating an error and set
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the Result-Code to the DIAMETER_RATE_TOO_BIG value.
5.10. OC-Best-Before AVP
The OC-Best-Before (AVP Code TBD12) is of type Time and tells the
expiration time/date for the information received in the OC-
Information. For example, when the overload condition is on, the
expiration of the 'best before' timer causes the same as receiving a
DOCA-Report-Request/Answer with the OC-Action set to 'Stop'.
[Editor's node: to be decided whether a duration timer is a better
measure. Using Time has the assumptions nodes have actually
clocks that a running approximately same time.]
5.11. OC-Origin AVP
The OC-Origin (AVP Code TBD13) is of type DiameterIdentity and tells
the identity of the Diameter node that originated included the
overload control information. Both host and realm information MUST
be included in the OC-Origin AVP. Note, if the OC-Scope AVP
indicates only a realm wide scope for the overload information, then
the realm part of the OC-Origin AVP is meaningful and the host
information only serves as an additional information of the
representative for the realm wide information.
5.12. OC-Priority AVP
The OC-Priority (AVP Code TBD14) is of type Unsigned32 and defines
the priority level. The value of 0x00000000 is the highest priority
and the value of 0xffffffff is the lowest priority. The absence of
the OC-Priority AVP means there is not specific priority level
defined and the priority SHOULD be considered as the lowest possible.
When used within the OC-Information grouped AVP, the OC-Priority AVP
defines the priority for the listed applications within the OC-
Applications AVP.
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5.13. Attribute Value Pair flag rules
+---------+
|AVP flag |
|rules |
+----+----+
AVP Section | |MUST|
Attribute Name Code Defined Value Type |MUST| NOT|
+---------------------------------------------------+----+----+
|OC-Information TBD3 x.x Grouped | M | V |
+---------------------------------------------------+----+----+
|OC-Scope TBD4 x.x Unsigned32 | M | V |
+---------------------------------------------------+----+----+
|OC-Application TBD5 x.x Grouped | M | V |
+---------------------------------------------------+----+----+
|OC-Action TBD6 x.x OctetString | M | V |
+---------------------------------------------------+----+----+
|OC-Algorithm TBD7 x.x Unsigned32 | M | V |
+---------------------------------------------------+----+----+
|OC-Level TBD8 x.x OctetString | M | V |
+---------------------------------------------------+----+----+
|OC-Utilization TBD9 x.x Float32 | M | V |
+---------------------------------------------------+----+----+
|OC-Tocl TBD10 x.x Unsigned32 | M | V |
+---------------------------------------------------+----+----+
|OC-Sending-Rate TBD11 x.x Float32 | M | V |
+---------------------------------------------------+----+----+
|OC-Best-Before TBD12 x.x Time | M | V |
+---------------------------------------------------+----+----+
|OC-Origin TBD13 x.x DiameterIdentity | M | V |
+---------------------------------------------------+----+----+
|OC-Priority TBD14 x.x Unsigned32 | M | V |
+---------------------------------------------------+----+----+
6. Transport Considerations
In case of Stream Control Transmission Protocol (SCTP) transport, the
DOCA application is RECOMMENDED to mark its Diameter packets using
the DOCA defined SCTP Payload Protocol Identifier (PPID) TBD1. The
PPID MAY be used by intermediating network nodes or agents to peek
into SCTP message and find out that this is about overload control.
Such information can be used for prioritizing SCTP packet handling as
an example.
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7. Examples
Consider the following simplified scenario shown in Figure 1 where
two servers are connected to a proxy. All three nodes understand the
DOCA application. These three nodes belong to the same
administrative domain and the operator decided that he wants to hide
the Diameter topology of his own network. Consequently, aggregate
information is provided by the proxy for any Diameter overload
message exchange. The Diameter client also supports the DOCA
application. Between the client and the Diameter proxy we assume an
arbitrary Diameter network that passes Diameter messages back and
forth.
+------------------+ +------------------+
| Server 1 | | Server 2 |
| (DOCA capable) | | (DOCA capable) |
+----------`.------+ +------------------+
`.
`.
`.
`.
+-------`.---------+
| Proxy |
| (DOCA capable) |
+--------+---------+
|
......................+......................
|
+-------`.'--------+
| |
| Intermediate |
| Diameter nodes |
+--------+---------+
|
|
+--------+---------+
| Client |
| (DOCA capable) |
+------------------+
Figure 1
Let us assume that the DOCA exchange is initiated by server 1 who
determines that the load situation increases. It sends a DOCA-
Report-Request message (with piggybacked overload information)
towards the client. The message also instructs the client to reduce
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it's sending rate. The proxy, who receives the DOCA-Report-Request
decides to change the included OC-Origin information and forwards the
request to the client.
When the client receives the DOCA-Report-Request message is processes
the content, evaluates the overload information content and reacts
accordingly, and returns a DOCA-Report-Answer message back to
acknowledge the receipt.
Alternatively, let us assume that the proxy does not forward the
message but instead terminates the DOCA-Report-Request received from
Server 1. It instead decides to route traffic to the backup server,
Server 2. In this case the entire process was transparent for the
client.
8. IANA Considerations
8.1. Application Identifiers
This specification reserves a new Diameter Application-ID TBD14 for
the Diameter Overload Control Application (DOCA) from the
'Authentication, Authorization, and Accounting (AAA) Parameters'
Application IDs registry.
8.2. SCTP Payload Protocol Identifier
Section 6 reserves a new SCTP Payload Protocol Identifier for the
DOCA application usage. The value is reserved from the existing SCTP
Payload Protocol Identifiers registry.
8.3. Command Codes
Two command codes are defined in Section 4. The DOCA-Report-Request
Command Code is TBD and the DOCA-Report-Answer Command Code is TBD.
Both are allocated from the 'Authentication, Authorization, and
Accounting (AAA) Parameters' Command Codes registry.
8.4. AVP Codes
New AVPs defined by this specification are listed in Section 5. All
AVP codes allocated from the 'Authentication, Authorization, and
Accounting (AAA) Parameters' AVP Codes registry.
8.5. Result-Code Values
This specification adds several Diameter Overload Control Application
specific Permanent Failure codes from the 'Authentication,
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Authorization, and Accounting (AAA) Parameters' Result-Code AVP
Values (code 268) - Permanent Failure registry:
AVP Values | Attribute Name | Reference
-----------+-------------------------------+----------
5xxx | DIAMETER_NO_COMMON_SCOPE | RFCxxxx
5xxx | DIAMETER_NO_COMMON_ALGORITHM | RFCxxxx
5xxx | DIAMETER_TOCL_TOO_SMALL | RFCxxxx
5xxx | DIAMETER_TOCL_TOO_BIG | RFCxxxx
5xxx | DIAMETER_RATE_TOO_BIG | RFCxxxx
8.6. New Registries
Four new registries are needed under the 'Authentication,
Authorization, and Accounting (AAA) Parameters' registry:
o OC-Scope AVP Values: the policy for this registry is Specification
Required.
o OC-Action AVP Values: the policy for this registry is Standards
Action.
o OC-Level AVP Values: the policy for this registry is Standards
Action.
o OC-Algorithm AVP Values: the policy for this registry is
Specification Required.
9. Security Considerations
The security properties of the Diameter Overload Control Application
(DOCA) follows the security model of Diameter [RFC6733]. This
implies there is no proper means to verify the message and AVP
content correctness if multiple intermediate Diameter agents are
present on the path between the DOCA client and server. As a result
a malicious intermediate could feed incorrect overload control
information to DOCA clients and peers, and thus affect negatively to
the overload condition recovery. A possible way to overcome the
obvious security vulnerability is to mandate the use of end-to-end
security at the Diameter AVP level.
As such, like any other Diameter application this document would
benefit from a Diameter end-to-end security mechanism. While work is
in progress it has not yet been finalized and therefore this
specification does not rely on it.
10. Acknowledgements
The author thanks Annett Seefeldt for her constructive comments on
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the technical aspects on this document.
11. References
11.1. Normative References
[I-D.ietf-dime-overload-reqs]
McMurry, E. and B. Campbell, "Diameter Overload Control
Requirements", draft-ietf-dime-overload-reqs-04 (work in
progress), February 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012.
11.2. Informative References
[I-D.campbell-dime-overload-data-analysis]
Campbell, B., Tschofenig, H., Korhonen, J., and A. Roach,
"Diameter Overload Data Analysis",
draft-campbell-dime-overload-data-analysis-00 (work in
progress), February 2013.
[RFC6408] Jones, M., Korhonen, J., and L. Morand, "Diameter
Straightforward-Naming Authority Pointer (S-NAPTR) Usage",
RFC 6408, November 2011.
Appendix A. Design Justification
Section 1 discussed the motivation and the background for the
Diameter enhancements for an explicit Diameter overload control
solution. This specification solves the overload control at the
application level instead of extending the Diameter base protocol or
piggybacking overload control information on top of existing
applications. The reasoning is the following:
1. The support for Diameter overload control capability between
Diameter peers is explicit (i.e., a new application-id is
advertised) and thus not build on an exchange of optional
Attribute Value Pairs (AVPs).
2. The support for Diameter overload control capability between
Diameter client and server is explicit.
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3. The peer selection follows the existing standards including DNS-
based discovery [RFC6408] and does not assume additional peer
selection criteria learnt from an exchange of optional AVPs.
4. The application based solution is able to traverse and also
propagate overload control information through realms that deploy
relay agents without Diameter overload control support.
5. The propagation does not depend on a modified behavior of already
specified Diameter command codes.
6. Pretending not to establish a state when there actually is an
overload capability and information state still maintained. The
state might not be at the application level but is there.
7. Trying to avoid information flooding, especially across
administrative domains.
8. The use of the application concept allows established mechanisms
for filtering and Diameter traffic engineering, since it behaves
like any other Diameter application.
9. The use of the dedicated application allows to isolate (even
physically) the overload signaling into a dedicated transport
that is not affected by other Diameter messages and network
traffic.
Authors' Addresses
Jouni Korhonen
Renesas Mobile
Porkkalankatu 24
Helsinki 00180
Finland
Email: jouni.nospam@gmail.com
Hannes Tschofenig (editor)
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
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