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Thursday, May 29, 2014

BITAG: 6 measures to stop throttling of VoIP - for super-users?

BITAG: After 7 months in purdah, BITAG is back with a bang: some concrete recommendations to ISPs, VoIp developers and industry. "BITAG’s Technical Working Group recommends the following to minimize the occurrences and impact of VoIP impairment, failure, and restrictions:

  1.  Network operators should avoid impairing or restricting VoIP applications unless no reasonable alternatives are available to resolve technical issues. 
    • Certain network management actions may have the effect of limiting or restricting VoIP traffic as a method of ensuring network integrity. Examples include port blocks or traffic limitations implemented when a customer uses a vulnerable VoIP service that can be exploited by attackers for the purpose of flooding the network with unwanted traffic. In adopting any approach that has the effect of limiting the use of VoIP, network operators should seek to minimize the impact of the approach on legitimate VoIP use. 
  2. VoIP-related ALGs in operator-supplied home routers should minimize their impact on traffic other than the operator’s VoIP service where possible. 
    • VoIP-related ALGs can interfere with some VoIP services while attempting to facilitate NAT traversal for other VoIP services. Because of these problems, BITAG recommends that VoIP-related ALGs in operator-supplied home routers should either allow the VoIP-related ALGs to be disabled for customers who do not subscribe to the operator’s VoIP service or minimize or avoid impact to independent VoIP services and all other traffic not associated with the operator’s own VoIP service. Where possible, VoIP-related ALGs in operator-supplied home routers should be disabled by default. ALGs for real-time applications (including VoIP) can be problematic for services other than VoIP, but recommendations concerning ALGs more broadly are outside the scope of this report. 
  3. Manufacturers of home routers should disable VoIP-related ALGs by default.
    • Some consumers purchase their home routers from retailers rather than from network operators. To limit the impact of VoIP-related ALGs on VoIP services, home routers sold to consumers should have VoIP-related ALGs disabled by default. 
  4. Port blocking rules in consumer equipment should be user-configurable. 
    • The port blocking (or firewall) rules of consumers’ home routers should be user-configurable, whether the routers are provided by the ISP or purchased separately by the consumer. By making these rules user-configurable, technically sophisticated users may be able to eliminate port blocks that prevent them from using VoIP services. It is recommended that the documentation provided with the consumer equipment inform the consumer that port blocking or firewall rules have been implemented, the default ports blocked, and how consumers can modify those rules. 
  5. If network operators intentionally use network policies or practices that impair or restrict VoIP, they should provide disclosures about those policies and practices and provide communications channels for feedback. 
    • BITAG recommends that network operators disclose their policies and practices that may or could result in VoIP impairment, failure, or restrictions. The information should be readily available to both customers and non-customers alike. For example, such policies could be provided on the operator’s public-facing web site or on a page dedicated to summarizing or describing the ISP’s network management practices. If specific VoIP applications are impaired or restricted, those applications should be listed by name, along with a brief description of the reason for the impairment or restriction. BITAG also recommends that ISPs provide a communications channel or other clear method for application providers and consumers to discuss the impact of VoIP impairment, failure, and restrictions, and possible mitigations. 
  6. Application developers should design VoIP applications to be port-agile where possible. 
    • BITAG recommends that VoIP application developers design VoIP applications and services to be port-agile where possible. Applications designed to tolerate random source ports or to allow port selection to be user-configurable are better able to avoid VoIP impairments that result from port blocking or contention between multiple services for the same port. Whether particular applications can be re-designed to be port agile may depend on whether re-designed versions of the application can be made compatible with existing versions or other existing applications." 'via Blog this'

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