Privacy/Reviews/Persistent SPDY CWND

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Document Overview

Feature/Product: SPDY persistent CWND setting
Projected Feature Freeze Date: (tbd)
Product Champions: Patrick McManus
Privacy Champions: (the privacy Friend you're working with)
Security Contact: Curtis Koenig
Document State: [NEW]


Architectural Overview: (date TBD)
Recommendation Meeting: (date TBD)
Review Complete ETA: tbd


In this section, the product's architecture is described. Any individual components or actors are identified, their "knowledge" or what data they store is identified, and data flow between components and external entities is described.

The main objective of this feature/product is: network performance for the spdy protocol using the persistent CWND settings attribute of the protocol.

Design Documents:


A spdy server sends a value that represents the effective network CWND to the host periodically during the session. The client, upon creating a new session, echoes this value to the server so it can apply it to the new session and garner a performance benefit over TCP slow start. It is essentially a transport layer cookie specific to the protocol.

The value is limited in our implementation to 7 bits and is stored per connection entry. a connection entry is more or less defined by the tuple of {hostname, ssl, private-browsing, anonymous} - so this data is not shared between PB and non PB sessions.

This data is not stored on disk and is not persisted between restarts.

an about:config preference is available to control whether or not the data is stored.

User Data Risk Minimization

In this section, the privacy champion will identify areas of user data risk and recommendations for minimizing the risk.

Alignment with Privacy Operating Principles

In this section, the privacy champion will identify how the feature lines up with Mozilla's privacy operating principles.

See Also: Privacy/Roadmap_2011#Operating_Principles:

Principle: Transparency / No Surprises

(How the feature addresses this)

Recommendations: (what can be improved)

Principle: Real Choice


Principle: Sensible Defaults


Principle: Limited Data


Follow-up Tasks and tracking

What Who Bug Details
[NEW] Initial Overview Discussion  ? Meeting time TBD