Improving compression with a preset DEFLATE dictionary
A few years ago Google made a proposal for a new HTTP compression method, called SDCH (SanDwiCH). The idea behind the method is to create a dictionary of long strings that appear throughout many pages of the same domain (or popular search results). The compression is then simply searching for the appearance of the long strings in a dictionary and replacing them with references to the aforementioned dictionary. Afterwards the output is further compressed with DEFLATE.
CC BY SA 2.0 image by Quinn Dombrowski
With the right dictionary for the right page the savings can be spectacular, even 70% smaller than gzip alone. In theory, a whole file can be replaced by a single token.
The drawbacks of the method are twofold: first - the dictionary that is created is fairly large and must be distributed as a separate file, in fact the dictionary is often larger than the individual pages it compresses; second - the dictionary is usually absolutely useless for another set of pages.
For large domains that are visited repeatedly the advantage is huge: at a cost of single dictionary download, all the following page views can be compressed with much higher efficiency. Currently we aware Continue reading
Cisco Live US – 2015
I will be attending this year’s Cisco Live US in San Diego!
This is my first Cisco Live, so I dont really know what to expect. There are alot of great sessions that I want to attend (if they are not already full), and I will be posting my week here when i have my sessions down.
If you want to connect for a coffee or a chat, feel free to drop me a mail/tweet, and im sure we can figure something out!
See you in San Diego!
Too Many Details Can Hurt You (or Why You Need the Fundamentals First)
The IPv6 Security Summit at the Troopers conference always has a few awesome IPv6 presentations (many people claim Troopers is the conference to attend if you’re serious about IPv6), and this year was no exception. A day after the MLD bashing, Enno Rey delivered a great in-depth presentation on DHCPv6 features and shortcomings.
It seems the DHCPv6 intricacies presented in that talk were too much for some of the attendees – that afternoon I accidentally stumbled upon a visibly distressed gentleman who started our chat with “How could anyone expect us to deploy IPv6 in a production environment?”
Read more ...[SDN Protocols] Part 5 – NETCONF
For those that followed my SDN Protocols series last summer, you might have noticed a missing entry: NETCONF. This protocol has actually existed for some time (the original now-outdated specification was published in 2006), but is appearing more often, especially in discussions pertaining to network automation. The current, updated specification - RFC6241 - covers a fairly large amount of material, so I will attempt to condense here. NETCONF operates at the management layer of the network, and therefore plays a role similar to that of OVSDB.[SDN Protocols] Part 5 – NETCONF
For those that followed my SDN Protocols series last summer, you might have noticed a missing entry: NETCONF. This protocol has actually existed for some time (the original now-outdated specification was published in 2006), but is appearing more often, especially in discussions pertaining to network automation. The current, updated specification - RFC6241 - covers a fairly large amount of material, so I will attempt to condense here. NETCONF operates at the management layer of the network, and therefore plays a role similar to that of OVSDB.[SDN Protocols] Part 5 – NETCONF
For those that followed my SDN Protocols series last summer, you might have noticed a missing entry: NETCONF. This protocol has actually existed for some time (the original now-outdated specification was published in 2006), but is appearing more often, especially in discussions pertaining to network automation. The current, updated specification - RFC6241 - covers a fairly large amount of material, so I will attempt to condense here. NETCONF operates at the management layer of the network, and therefore plays a role similar to that of OVSDB.OS X – Outlook Search “No Results”
The worst feeling for a geek:
Courtesy of xkcd (http://xkcd.com/979/)
This has happened to me twice now: upgrading Mac OS X from one release to another and after the dust settles, the search function in Outlook 2011 totally breaks and always returns “no results”. As we all know, email sucks and being able to deftly search through that mound of crap in your mail client is the only thing that makes it somewhat bearable.
When I upgraded from 10.8 to 10.9, I was the guy in the cartoon above. I had to resort to uninstalling and reinstalling all of Office to get this repaired. Urgh.
Well, I just upgraded from 10.9 to 10.10 and lo, the same problem with Outlook search. However this time my karma must be right topped off because I found the solution buried in a message board after an hour or so of searching.
Sweet, merciful help!
The post is from the macrumors.com forum and exactly described the issue and how to fix it on my machine. As stated, the permissions on my Microsoft Office 2011 directory allowed only my account to open the directory:
jknight@mac:~% ls -ld /Applications/Microsoft Office Continue reading2016 CCDE Practical Exam Dates
Cisco announced 2016 CCDE Practical exam dates. CCDE practical exam is organised only in every 3 months. Prerequisite for the exam is CCDE Written Qualification exam. You can attend the exam 4 times a year in a Professional Pearson Centers. I am planning to start my CCDE trainings 2 months before an announced exam date… Read More »
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Common Misconceptions about SDN
Andrew Lerner, my favorite Gartner blogger, published a great article documenting common SDN misconceptions. Not surprisingly, they're pretty much in line with what I've been ranting about for the last few years (including Whitebox Switching Is not SDN). Enjoy!OS X — Outlook Search “No Results”
The worst feeling for a geek:
Courtesy of xkcd (http://xkcd.com/979/)
This has happened to me twice now: upgrading Mac OS X from one release to another and after the dust settles, the search function in Outlook 2011 totally breaks and always returns “no results”. As we all know, email sucks and being able to deftly search through that mound of crap in your mail client is the only thing that makes it somewhat bearable.
CUCM 10.5 Upgrade issue
Hey everyone. I have just finished my upgrade to CUCM 10.5.2 and I faced an issue at the end of the ugprade. Of course this always happen after you spent some hours waiting for the upgrade to be successful According to the very good Cisco DocWiki, VMware Tools are specialized drivers for virtual hardware that […]Check Point – Upgrade Without Dropping Connections
Check Point firewall upgrades have always been painful. The loss of connection state is a big part of this. Existing connections stop working, and many applications need restart. It looks like there is a way of minimising this pain on upgrade.
Stateful firewalls record the current ‘state’ of traffic passing through, so they can recognise and allow reply or related traffic. If you have a firewall cluster, they need to synchronise state between the cluster members. This is so that if there is a failover, the new Active node will be aware of all connections currently in flight.
If you have a failover, and the standby member is NOT aware of current connection state, it will drop all currently open sessions. Any packet that isn’t a SYN packet will get dropped, and the applications need to establish new connections. Some applications handle this well – especially those that use many short-lived connections such as HTTP or DNS. But other applications that have long-running connections – e.g. DB connections – may struggle with this. They think the connection is still open, and take a long time to figure out it’s broken. They may eventually recover on their own, or they may Continue reading