Welcome!

Mobile IoT Authors: Liz McMillan, Dana Gardner, Zakia Bouachraoui, Yeshim Deniz, Elizabeth White

Blog Feed Post

What's in an RFC?

Deciphering and interpreting an RFC is never an easy thing and many times the same RFC can be interpreted different ways.  My favourite RFC is RFC 2616 - Hypertext Transfer Protocol -- HTTP/1.1 specifically section 13 on caching and section 14 on headers make for a very interesting read.  I frequently encounter situations where browsers and applications don't appear to behave as the RFC states they should.  Here are a couple of examples I have come across:

 

Firefox 3 Expires and Max-Age

According to section 14.9.3 "If a response includes both an Expires header and a max-age directive, the max-age directive overrides the Expires header, even if the Expires header is more restrictive."  Recent testing with Firefox 3 has revealed that this is not the case.   If the Expires header is in the future then the Max-Age value from Cache-Control header is honoured, but if the Expires header is in the past then Firefox 3 will cache the content on the browser with an immediate expiry. Neither  Internet Explorer 7 nor Chrome exhibit this same behaviour the cache-control headers always override the Expires header even when the value is in the past.   This discrepancy in behaviour when a customer said they were getting inconsistent results during their testing of WebAccelerator, just goes to show the importance of performing cross-browser functional testing of your application.  

Maximum Value for Expires Header

Section 14.21 covers more details on the use of the Expires header specifically appropriate values for the header. 

"HTTP/1.1 servers SHOULD NOT send Expires dates more than one year in the future."  However I occasionally see headers like the one below that is set for almost 30 years.

Expires    Sun, 17 Jan 2038 19:14:07 GMT

I'm all for setting expires in the future but isn't 1 year sufficient or is 30 years really necessary?

Cache-Control Private

This came to my attention through one of the forum posts on DevCentral in regards to the insertion of a Cache-Control=private header into responses and how this was impacting Akamai.  It turns out that Akamai does not honour the Cache-Control header of private.  Section 14.9.1 of the RFC states a private header  "Indicates that all or part of the response message is intended for a single user and MUST NOT be cached by a shared cache. This allows an origin server to state that the specified parts of the response are intended for only one user and are not a valid response for requests by other users. "  In my opinion Akamai is a shared cache and should not cache content with the Cache-Control header of private. 

 

These are just 3 examples of how items in the RFC can either be interpreted differently and sometimes ignored.  I'm sure there are others out there.  Do you have any other examples?

 

 

Reblog this post [with Zemanta]

Categories:  

Read the original blog entry...

More Stories By Dawn Parzych

Dawn Parzych is a Technical Product Marketing Manager at Instart Logic. Dawn has had a passion for web performance for over 15 years with a focus on how to make the web faster. As a technical product marketing manager at Instart Logic, she researches and writes about trends in the web performance space and how they impact the user experience. Prior to joining Instart Logic, Dawn worked at F5 Networks, Gomez & Empirix.

IoT & Smart Cities Stories
The platform combines the strengths of Singtel's extensive, intelligent network capabilities with Microsoft's cloud expertise to create a unique solution that sets new standards for IoT applications," said Mr Diomedes Kastanis, Head of IoT at Singtel. "Our solution provides speed, transparency and flexibility, paving the way for a more pervasive use of IoT to accelerate enterprises' digitalisation efforts. AI-powered intelligent connectivity over Microsoft Azure will be the fastest connected pat...
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
Codete accelerates their clients growth through technological expertise and experience. Codite team works with organizations to meet the challenges that digitalization presents. Their clients include digital start-ups as well as established enterprises in the IT industry. To stay competitive in a highly innovative IT industry, strong R&D departments and bold spin-off initiatives is a must. Codete Data Science and Software Architects teams help corporate clients to stay up to date with the mod...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Druva is the global leader in Cloud Data Protection and Management, delivering the industry's first data management-as-a-service solution that aggregates data from endpoints, servers and cloud applications and leverages the public cloud to offer a single pane of glass to enable data protection, governance and intelligence-dramatically increasing the availability and visibility of business critical information, while reducing the risk, cost and complexity of managing and protecting it. Druva's...
BMC has unmatched experience in IT management, supporting 92 of the Forbes Global 100, and earning recognition as an ITSM Gartner Magic Quadrant Leader for five years running. Our solutions offer speed, agility, and efficiency to tackle business challenges in the areas of service management, automation, operations, and the mainframe.
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, compared the Jevons Paradox to modern-day enterprise IT, examin...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
DSR is a supplier of project management, consultancy services and IT solutions that increase effectiveness of a company's operations in the production sector. The company combines in-depth knowledge of international companies with expert knowledge utilising IT tools that support manufacturing and distribution processes. DSR ensures optimization and integration of internal processes which is necessary for companies to grow rapidly. The rapid growth is possible thanks, to specialized services an...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...