December 24, 2007
Sometimes one could become so comfortable with something, that one becomes blind to the underlying technology. Such was the case with me a few days ago when I was trying to delete an IP address from one Linux node on the network and assign it to another.
The problem was that the new node would remain inaccessible on the network. It would eventually show up, but that didn't make troubleshooting easy. We're all so used to plugging a node into a switch and have it up and running that we forget that underneath the IP address, there's the MAC address with the DNS-like ARP tables running on switches and nodes.
Apparently the "service network reload" command on the Linux box wasn't making any ARP announcements on the network, leaving the ARP tables (evidently with long aging timers) with old mappings. And that explains why the new Linux node would remain inaccessible for some time.
I'm not sure if the network subsystem in Linux is supposed to advertise a new IP to MAC (possibly using a an ARP request). Strangely, even a reboot wouldn't fix this problem. It is possible that the firewall (iptables) rules were preventing this. Whatever the case, a manual ARP request using the arping command seemed to have resolved this. Here's the syntax (with a phony IP):
arping -U -I eth0 192.168.100.100
arping is a useful Linux tool similar to the ping command, but operating at the MAC level. I suppose there's a good chance that even pinging a node on the local network from the Linux box would have done the trick and updated the ARP tables. Anyways, if you find yourself in a similar situation, check the ARP tables on your switches. They're so easy to forget.
linux,arp,mac address,ethernet,ip address,network switch
December 13, 2007
Like most people who have a Web site I check my site's ranking on Google SERPs (Search Engine Results Pages) from time to time. It's striking how much of a Website's life depends on Google. That's particularly true with smaller sites whose lifeblood is the traffic Google sends their way. But even bigger sites would suffer severely if their pages suddenly lost ranking in Google. Sure there are other search engines like Yahoo and MSN, but enough about those.
And so when a couple of days ago I noticed that my site's traffic had a noticeable drop in traffic, the first place I looked for diagnosis was Google. Sure enough, my site's pages where either non-existent or had dropped considerably in ranking. I know that compared to other sites, my traffic is but a drop in a proverbial bucket, but even so the realization of lost ranking made me concerned. I can only imagine how those people, whose living is tied to their traffic, may feel when Google starts to snub their sites. the results could be devastating.
Had I violated any one of Google's quality guidelines? Had I engaged in any activity that might have blacklisted my site? I was stumped. I hadn't made any design changes to the site that I could recall. I even tested my site for unintended search engine spamming using a couple of different online tools. One claimed I had hidden text on my pages. They were light-colored timestamps on a colored background. Just for insurance I changed them to a darker color. It also caught what it regarded as keyword stuffing. The culprit turned out to be whitespace characters ( ) with missing trailing semi-colons. So at least I got to fix this error on my site, and then I just moved on.
Today, inexplicably my site's ranking in Google SERPs seems to be back where it used to be. Could this have been the result of those minor changes? I don't think so. Most likely, the drop was due to some temporary event in Google's algorithm.
What's alarming is that Google is not just influential, but it's vital to so many. Where can one go to if they are unfairly treated? Who will listen? This is not a paid service, there are no SLAs (Service Level Agreements), contracts, or even tenuous promises. Mine is just a hobby site. Being present in Google is great, but I'd still be doing this even if my site wasn't included. I don't think my attitude would be the same if I were making a living off my site.
I can appreciate that Google has the enormous task of separating the good sites from the bad. But with that much power and reach, it is inevitable that many innocent sites will be inadvertently punished. Consider how things would be if there were only one powerful and unregulated credit agency with two marginal ones, instead of the three with equal standings today.
google,search engines,seo,serp,spam,page ranking
December 5, 2007
So today I'm at my desk in the office fiddling with a new Web accelerator toy, er appliance, and I get the dreaded call transfer from the front desk. The Web caching box must've had fried my common sense and I took the call. It was a sales pitch. People who call my number at the office usually dial my extension directly. Even then, they get a call-screening message asking them to identify themselves. If I am at my desk and if it's urgent, I pick up the call, otherwise they go into the voicemail and I get back to them later.
Generally, the only times calls are transferred to my extension via the front desk are when someone calls up the office and asks for the Web guy or the programmer or the developer and those are typically salespeople pushing a new and exciting product or a service or the survey guys asking for 5 minutes that last a good half hour. The sales guy was peddling Microsoft and Cisco training courses.
With my mind still on Web caching, I half-heartedly listened to the man drone on effusively about their courses and their various membership levels. He had me browse to their Web site and took me through some of their marketing pages. Not wanting to be discourteous, I obliged, but he must've realized that I wasn't exactly the type of ready and willing customer he was hoping for. Undaunted, he pushed on buttering me up with compliments that I was a part of an exclusive group chosen to receive the course material at a substantial discount. I finally had to cut him off and asked the inevitable question, "How much?"
Sensing slippage, he promptly handed the call over to one of their professional and cheerful salespeople with the hopes that the new guy would close the deal. When I resisted, the cheers suddenly gave way to a quick thank-you and a phone number to call back and that was the end of it.
I don't understand this. I mean I know techies are eccentric and lack some social skills, but are we taken for easy prey? I could almost hear the salesman's thoughts through all the pleasantries, "Buy it, you dumb ass. Take the bait. Buy the stupid course." I suppose there are some of us out there who would succumb to the art of persuasion. I've had my weak moments too, but not today. If only he was peddling a Web caching courseware today.
sales pitch,telemarketing,web caching,web accelerator
November 26, 2007
For the longest time, I've been wanting to create a simple feed widget to place on a web page and have it display links from the syndicated site. Easier dreamt than done, until this thanksgiving weekend when I decided to partially put the long holiday to good use and write up a widget tool.
It's a weird thing. I get to be away form work for 4 days, yet I spend my free time coding and learning new programming techniques. There was certainly time spent with family, but for me, delving into coding challenges also has a therapeutic effect. Some programmers may understand the absurdity of this. There's that drudgery factor at work that you don't have to deal with when hobby programming. No boss to report to, no business politics, no users interrupting with questions or problems. I get to set the rules from end to end. Not to mention that at work I'm an ASP.NET programmer, and at home I turn into a PHP coder.
I realize that there are a bunch of these RSS/ATOM widgets already out there. So mine's another one to add to the list. Partial as I may be, I think it does a decent job and it allow for some basic customizations.
Since this is a new utility, consider it in beta mode until I say it's not. If Gmail can be in beta for eternity, why not this one? I've tested it quite a bit, but I'm sure there are still bugs to be fixed. Also I have no idea what impact this may have on my Web hosting account quotas. We'll find out. Documentation is not one of my strengths, but I will eventually produce an FAQ on some of the widget's capabilities, features, and customizations using, for instance, CSS. There are also plans to enhance it further, if there's enough demand for it.
November 17, 2007
Call me paranoid, but I always like to be clear on what a site is doing on my computer while I have it up on my browser. I don't think I'm that paranoid (okay, maybe a little,) but I think users are entitled to know if a site is storing and reading data to and from their computers. That's an exact description of what browser cookies are used for, but tonight I learned about a new kind of cookie I had been abashedly unaware of.
I for one, don't appreciate being followed around while I surf the Net, so I delight in cleaning or modifying my cookies often and throwing off the trackers. But tonight I was stumped by an often visited music site that remembered me steadfastly, even when I deleted my cookies and visited the sites on different browsers.
What was going on here? Was the site using my IP address to identify me? I doubted it. IP address tracking is so inexact these days that it's generally only used for geo-location, and even that yields questionable results. After some persistent searching, I finally found the elusive answer, and it was a Flash cookie.
I had never known that Flash player could store data on users' computers, so I delved a bit deeper. I found out that they are similar to, but work completely independently from browser cookies. On my Windows XP machine, Flash cookies (known as local storage in Macromedia's jargon) are stored under the "\Documents and Settings\[account]\Application Data\Macromedia\Flash Player\#SharedObjects\" folder. By default each site is allowed to store and access up to 100KB in the cookies and users are oblivious to this activity the whole time.
Way to go Adobe. I don't remember every seeing anything about these cookies when I was installing the Flash player. No doubt it was buried in some privacy legalese. The good news is that once discovered, these cookies can be deleted using Adobe's Website, or by just simply zapping them in the folder mentioned above. Adobe's site also allows users to disable Flash cookies altogether. The caveat is that just like browser cookies, many sites rely on these cookies and probably will not function correctly without them. For me, the happy medium was to configure Flash to alert me every time a site wants to store a Flash cookie on my PC. You can do the same by going to Global Storage Settings panel on Adobe's Flash site and alter your settings to match the figure below.
Maybe you can't stop sites from storing and retrieving data from your computer, but at least you know who's tracking you using this type of cookie.
flash cookies,flash local storage,adobe,macromedia,flash,cookies,browser cookies,browsers,flash player
November 13, 2007
Here's the brilliant idea for today. Why don't the hosting companies let the right representatives answer their customers' questions, instead of letting customers waste time with their less trained agents? I've been helping a friend setup a site on one of the nationally known web hosting sites, and I must say getting the right answer is an exercise in extreme patience.
My own site (the one carrying this blog) is hosted with one of the smaller outfits and I've been able to get my technical questions promptly and correctly answered most of the time. That doesn't seem to be the case with the larger companies. I don't even think they read the emails. I ask for something to be disabled, they send instructions back on how to enable it. Even worse, after dealing with so many newbies mindlessly spouting techie jargon, they have developed resistance to anyone trying to get technical with them.
It's only after several tries that an issue is escalated to the more knowledgeable staff who can finally help resolve the issue. I'm not sure whom is to blame here. Web hosting must be a cut-throat business and these outfits are just holding the line on expenses. The front-end positions are generally low-paying jobs, so I assume new people are brought in, trained quickly on the web hosting's interface, and then dumped in the call center pool. I wish I could get a sample of the questions these guys field. I can only imagine what absurdities customers throw at them.
The front-end agents are probably fine for the amateur callers, but it’s the back-end guys I really need when I call or email for something. I presume I never quite make it to the back, but I would be quite content with the middle-layer without being hassled by the front guys a few times. People tend to note that smaller hosting companies have more informed support personnel. That's certainly true with my hosting service. Perhaps the bigger guys can learn something from their smaller counterparts.
web hosting,tech support,call centers,customer service
November 6, 2007
October 31, 2007
Years ago when I lived in Germany for a short time, most people used their own canvass bags when grocery shopping. Initially I attributed that to the European environmental consciousness, which is probably somewhat correct. But then I found out that grocery stores charged for their bags and most people probably didn't want to pay for them. I believe the system is still the same over there and it works well.
In the US stores, grocery bags are an expected perk. Sure, we all pay for it in the form of tiny margins added to the cost of other items, but that is lost on the consumers. Grocery bags are abundant and free. At home we use these bags as trash can liners but when I go to my local grocery store's salad bar for lunch, the cashier would place the container in a plastic bag and I would promptly toss it in the trash at my desk. For years I felt guilty about this practice, but I wasn't about to change that habit.
Then a couple of months ago as I was leaving the store I noticed the long rows of the checkout lines filled with the yellow plastic bags. The sight and sound of hundreds of these bags crinkling and rustling as they were being filled made me consider the amount of waste that was being generated. This was just one moment in time, in one store, in one town. I was overwhelmed by the thought of millions of these bags being dumped in landfills everyday and right then I vowed to change my bagging habit. I wasn't quite ready for canvass bags, but I decided to save the plastic bags and reuse them every time I go to the store, until the bags become unusable.
It took a few false starts, but I finally made good on the promise. In the past couple of months that I have been reusing the bags, I have become quite accustomed to recycling them at the checkout counters. By now I have probably prevented 40 or so bags from going to the landfills and I feel pretty good about it. It wasn't difficult, nor was it inconvenient. It was just making a slight adjustment to correct this wasteful habit. Yet I wondered how many bags can be recycled if everyone shook the old habit.
Today I saw a glimmer of hope to that end. When I presented the clerk with my bag, she credited me with two cents off the total. When I inquired about the credit, she showed me a stamp imprinted on the bag indicating a 2-cent credit for re-use. The grocery store, ShopRite, is obviously trying to portray itself as an environmentally conscious company and I applaud them for that. Whatever their motivation (probably a mixture of business sense and green ambitions), this could set the stage for saving millions of bags from being wasted so needlessly. Other stores have also begun with their own similar initiatives to show their green sides. They just need to promote this a little. Grocery store bags could be going the same way as the beverage bottles and cans went years ago, and that's a good thing.
grocery stores,plastic bags,recycling,environment,green,landfills,trash
October 23, 2007
Troubleshooting misbehaving Web applications is a part of my job at work. Most of the time it's some buggy code that I or someone in our team had written. But sometimes I get approached about system problems too, like when a browser is having connection issues and can't access Web sites. If you are in the help desk business you know how the question is posed, "Is the Internet down?". I've always been tempted to reply: "Why yes, it is down. All that redundancy worked into it back in the DARPA era was a pile of lies. The whole Internet is toast."
Most of the time browser problems are not browser problems at all, they are network issues. The browser just gets the blame because it's front and center. A bad cable kicked once too many, an unplugged Wi-Fi access point, or a beleaguered DHCP server are the usual suspects. But the one that trips me most of the time is the proxy server setting. I've gotten better at it but I still occasionally miss this little item from my checklist.
As you may know proxy servers are protocol-level servers (appliances) that work as brokers between clients and servers. The most commonly used is the Web (HTTP) proxy server. Traffic passing back and forth between browsers and servers is funneled through them. Why use them? A detailed discussion is too boring, but in a nutshell, they make network admins' lives easier (more granular control, central management, etc), and they can cache and compress data saving on bandwidth and thus speeding things along.
Proxy servers are helpful, as long as one remembers that they're being used, especially when troubleshooting. Case in point, the other day I was working on a laptop connected to the Internet over Verizon Wireless broadband EVDO. No matter what I did I couldn't browse to the laptop's local Web server. Everything was fine when wireless was off, but as soon as I started it up, the local Web server would become inaccessible. What was happening? I could successfully ping my own server (duh), the Web service was running fine and listening on the local address, and there was no proxy server setting hidden in my browser (obvious place to look, but easily missed, specially when frantic).
After hours of investigating, including recruiting assistance from a colleague, the issue was revealed, quite by accident. Verizon Wireless comes with an add-on product called Venturi (enabled by default), used for optimization and compression. Turns out Venturi was the cause of this issue. When disabled, everything began working as expected. Venturi inserts itself in the TCP/IP stack and reroutes Web requests to a proxy server. No wonder I couldn't browse to the local server, the external Venturi proxy server had no idea how to access it, nor anything else on the private LAN.
The trouble with proxy servers is that it's hard to detect that your applications are using one, unless you pay attention to the telltale signs. First, with most applications, including browsers, you can check the network options and see if a proxy server address is configured. Next you can visit an IP address and header lookup page like whoami/My IP Address on this site, and check out the results. This page and the likes will display whatever information they can glean from your connection. Sometimes, but not always, proxy servers add headers such as "X-Forwarded-For" or "Via" to reveal the actual source of the request. You can also compare the shown source IP address to the IP address of your own machine. From the command line enter the "ipconfig" command (in Windows) which will display your actual IP address. If the lookup page is displaying the same IP address, chances are there is no proxy server in between, otherwise your traffic may be going through a proxy server and that would explain the irregularities of the sorts I was experiencing.
proxy servers,verizon wireless,evdo,ip address,ipconfig,tcp/ip,networks,browsers,http
October 10, 2007
Older Posts »
A couple of entries ago I griped about the seatbelt law and how I was caught and ticketed for not wearing one driving in Westchester county, NY. Little did I know that there is a move afoot in the same county to make bicycle helmets mandatory. Mind you, this is not for children (which I support), but for everyone, including adults.
I just don't understand how people can tolerate this erosion and intrusion into their personal rights. This is yet again another obvious attempt for municipalities to transform law-abiding citizens into law-breakers and collect money. It always comes down to money, doesn't it? A bunch of bureaucrats got together one day and brain-stormed about how they can raise more money and this emerged as a good candidate under the guise of protecting public safety.
The slippery slope is indeed upon us and you can be sure that it won't stop with mandatory adult bike laws. Soon, there will be mandatory blood tests to measure your bad cholesterol and fine you if it's over some arbitrary limit. Like to exercise? There will be laws forbidding you to raise your heart rate beyond a certain number of beats per minute. Like to shovel your own snow? There will be laws banning that. How about swimming? There will laws requiring flotation devices for everyone; laws that will ban lifting heavy objects, laws against strenuous hiking, laws against running with scissors, laws against wearing too few layers during the cold, laws against hammering a nail without a permit, and laws against other laws to make sure everything is covered.
You laugh now, but all these laws will be enacted to save you from yourself, and of course each offense will carry its own scheduled fine. Why not even a law to punish you if you haven't committed an offense for a certain length of time? The justification is that it's unfair for some people not to pay into the system while others are being bilked. And you had no idea you were a criminal a hundred times over already.
helmets,bicycle helmets,helmet law,laws
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