[Podcast] Greasing the wheels

In this episode of PING, Shumon Huque from Salesforce discusses how protocols with extensible flag fields can benefit from regular testing of the values possible in the packet structure. This technique is known as 'greasing' and has a strong metaphorical meaning of 'greasing the wheels' to ensure future uses aren't blocked by mistaken beliefs about the possible values.

Intermediate systems, often called 'middleboxes', attempt to identify 'risky' packet flows, and one way they do this is by flagging unexpected values in otherwise familiar packet flows as potentially dangerous. This approach is overly simplistic and can lead to protocol ossification, where the protocol becomes locked into using only the currently active range of values.

Most protocols are designed with flexibility in mind, including extra flag fields, settings, and options that allow for future growth. Many of these have 'reserved' values listed in IANA registries, intended for use later. Greasing is a proposed technique to exercise some of these values in live network traffic to observe how the protocol behaves 'on the wire'.

Shumon and his co-author and collaborator, Mark Andrews from Internet Systems Consortium (ISC), have been applying the greasing model to the DNS. In this episode of PING, we talk about its history in other protocols and how, in practice, greasing can be applied on the global Internet.

Read more about Shumon, Mark and Roy Arends' greasing activity on the web:

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