Opened 5 years ago

Closed 5 years ago

#70 closed defect (fixed)

Appendix B - Example

Reported by: maria.cruz.bartolome@… Owned by: draft-ietf-dime-ovli@…
Priority: minor Milestone:
Component: draft-ietf-dime-ovli Version:
Severity: Active WG Document Keywords:
Cc:

Description

In the example included in Appendix B, it is considered that the Agent reports Host overload directly back to the Client, when the Client request was for the Realm, withouth Destination Host (or direct connection). I do not agree about this behaviour. Agent will provide Host overload to the Client only when the request was sent to one specific host.

Example shall be modified.

Proposed modification:

Client Agent S1 S2 S3

| | | | | |(1) Request (DR:realm) | |

>| | | |

| | | | | | | | | | | |Agent selects S1 | | | | | | | | | | | | | | | | | | |(2) Request (DR:realm) |

|>| | |

| | | | | | | | | | | | |S1 overloaded, returns OLR | | | | | | | | | | | | | | | | |(3) Answer (OH:S1,OLR:RT=DH) | |<--------| | | | | | | | | | | | | | |sees OLR,routes next DR traffic to S2&S3 | | | | | |(5) Request (DR:realm) | |

>| | | |

| | | | | | | | | | | |Agent selects S2 | | | | | | | | | | | | | | | | | | |(6) Request (DR:realm) |

|>| |

| | | | | | | | | | | | | |S2 is overloaded... | | | | | | | | | | | | | | | | |(7) Answer (OH:S2, OLR:RT=DH)| | |<------------------| | | | | | | | | | | | | |Agent sees OLR, realm now overloaded | | | | | | | | | | | | | | | |(8) Answer (OLR: RT=R) |<--------| | | | | | | | | | | | | | |Client throttles DR:realm | | | | | | | | | | | | | | | | | | | | | | | | |

Figure 8: Mix of Destination-Host and Destination-Realm Routed

Requests

  1. The client sends a request with no Destination-Host AVP (that is,

a Destination-Realm routed request.)

  1. The agent follows local policy to select a server from its peer

table. In this case, the agent selects S2 and forwards the request.

  1. S1 is overloaded. It sends an answer indicating success, but also

includes an overload report. Since the overload report only applies to S1, the ReportType? is "Destination-Host".

  1. The agent sees the overload report, and records that S1 is

overloaded by the value in the Reduction-Percentage AVP. It begins diverting the indicated percentage of realm-routed traffic from S1 to S2 and S3.

  1. The client sends another Destination-Realm routed request.
  1. The agent selects S2, and forwards the request.
  1. It turns out that S2 is also overloaded, perhaps due to all that

traffic it took over for S1. S2 returns an successful answer containing an overload report. Since this report only applies to S2, the ReportType? is "Destination-Host".

  1. The agent sees that S2 is also overloaded by the value in

Reduction-Percentage. This value is probably different than the value from S1's report. The agent diverts the remaining traffic to S3 as best as it can, but it calculates that the remaining capacity across all three servers is no longer sufficient to handle all of the realm-routed traffic. This means the realm itself is overloaded. The realm's overload percentage is most likely different than that for either S1 or S2. The agent generates a new report for the realm of "realm", and inserts that report into the answer. The client throttles requests with no Destination-Host AVP at requested rate.

Change History (1)

comment:1 Changed 5 years ago by srdonovan@…

  • Resolution set to fixed
  • Status changed from new to closed

Agreed to remove the examples section and references to it.

Also agreed to add wording that a reporting node must only send report types that it knows the reacting node supports. This resulted in the following wording in section 4.2.3:

A reporting node MUST only send overload reports of a type advertised as supported by the reacting node.

Note that a reacting node advertises support for the host and realm report types by including the OC-Supported-Features AVP in the request. Support for other report types must be explicitly indicated by a new feature bit in the OC-Feature-Vector AVP.

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