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I know it's possible to modify the IP headers and change the source IP address, but it should be simple for network devices to detect and discard those messages. If they don't, why not? Does it add too much overhead?
The industry name for the feature you are asking about is called "Unicast Reverse Path Forwarding" (or as Cisco calls it, "uRPF"); it is defined in RFC 3704 and is considered a Best Current Practice (see BCP38).
Speaking at a very high level, most of the hardware used by ISPs has this feature built into an ASIC; normally there is not a huge penalty for turning it on. Sometimes there are feature conflicts, but again this is not a huge deal in most cases.
The biggest reason it isn't universal is because the internet is still somewhat like the American "wild west" in the 1800s; consider them analagous to a town's sheriff. The policies and competency of the engineering/operational personnel varies, and many ISPs are too busy with making things "work" that they don't have cycles to make things "work well".
That dynamic is particularly true in smaller countries; I worked for a large network equipment manufacturer in a previous life and occasionally traveled throughout southeast asia conducting ISP seminars. Smaller countries are often half a decade (or more) behind the practices and competency of ISPs here in the US (that's not to say that US ISPs are terribly great on the whole either, but they are generally much better off than, say, some of the ISPs operating in the smaller islands in the Pacific).
This results in the non-trivial amount of spamming / hacker traffic on the internet today... it's there because they have no lack of places to hide. Source IP address spoofing is one of their first lines of defense.
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I'm looking for a in house geocoding tool to geocode millions of address. I've tried on TIGER database, but it got only about 60% address rooftop. There are addresses way far away from the actual address. My needs are:
1. fast enough to process those millions of address in days
2. rooftop accuracy - shouldn't be too far away (I'll say less than 100 foot mistake)
3. in house service - so it should be free to our internal staff
4. ideally open source, but it's ok to have a one time cost to set it up
Currently I'm looking at application level infrastructure, and I'm open to dedicate map server or something like that. I just don't have enough information to start researching.
Feel free to throw me any ideas, thoughts, comments. I'd love to hear them!
There are two pieces to this problem.
the geocoder and how well it parses addresses and matches them to the reference data set.
the reference data
For 1, I have extracted the parser standardizer from PAGC into a postgresql stored procedure (which is OpenSource) and then built a couple of geocoders using that as the heart of the engine.
For 2, and the accuracy that you are looking for, you will likely need high quality commercial data like Navteq or parcel data. Tiger is good for the cost to get you near the location but Title 13 requires Census to fuzzy the address ranges to no single address can be matched to a Census form. So as you found out, Tiger will not do the job.
I have written a lot of geocoders and have one that will work with Navteq and should give you results that are close to your requirements. Check out http://imaptools.com/ and contact me if your interested.
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so ive read this post here: and im a bit confused, so here's my additional question:
how does UDP handle data which are lost? because it says there that UDP doesn't care if the data will arrive to the destination or the ordering of data.
SO example in an on line game, how does UDP handle data loss? my understanding is that when a data is lost so lets say my character's hand cant be seen in an on line game? or the warglaive of azinoth which i farmed for years is lost? LOL
and if the ordering is not important so lets say i the head of my character will be messed up or the body will be dislocated, something like that.
So can anyone clarify this for me?
A better example of UDP in gaming is for position information.
In this case the position of a character is sent several times a second and it doesn't matter whether a packet is lost as another one will be sent again shortly. When you combine this with a game engine that does some level of interpolation and extrapolation then you can achieve smooth looking motion from sporadic data.
In the case of re-ordering if you receive a character position which is older (in time) due to packet re-ordering you would just discard it as you've already got a newer value.
With your example of loot - it's possible this information is sent via TCP or using a reliable wrapper around UDP - to your client.
Take a look at http://code.google.com/p/lidgren-network-gen3/ for a C# UDP networking library which is designed with games in mind. It provides various unreliable and reliable channels over UDP and should give you an idea how UDP is typically used in games.
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I am working on getting the performance parameters of a tcp connection and one these parameters is the bandwidth. I am intending to use the tcp_info structure supported from linux 2.6 onwards, which holds the meta data about a tcp connection. The information can be retrieved using the getsockopt() function call on tcp_info. I have spent lot of time finding a good documentation which explains all the parameters in that structure, but couldn't find one.
Also I tested a small program to retrieve the values from tcp_info for a tcp connection where I found the measured MSS values for most of the time as zero.To make long story short-Is there a link to follow for which has complete details ontcp_info and also is it reliable to use these values.
Here is a fairly comprehensive write-up of the structure and use of the linux tcp_info by René Pfeiffer but there are a couple of things worth noting:
The author needed to look at these data repeated over time because there are no aggregate stats in that structure.
The author directs you to the tcp.c source as the final authority on the meaning of any of those data.
I'm not sure what you were hoping to get from the Maximum Segment Size, but expect you thought it meant something else.
If you are truly interested in exact measurements of bandwidth you need to use a measurement device which is outside the system being tested as even pulling the ioctls will affect the phenomenon you are interested in knowing about. A passive wire sniffer is the only way to get truly accurate results. Finally, depending on your application, "bandwidth" is a really broad umbrella which flattens many measurements (e.g. latency, round-trip-time, variability, jitter, etc.) into one category.
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Suppose an actor A has the site of an actor B in iFrames. There is no difference in the sites except the url. Urls are totally different. Should the actor A ask a permission of the actor B for using B's site? Is there any law that forbid placing other site on a site in iFrames?
Not a programming question, but at least let me help you with a link to a site. The owner of plagiarismtoday.com have had some of your concerns and, although not a lawyer, have collected quite a bit of information.
http://www.plagiarismtoday.com/2009/04/07/is-the-diggbar-content-theft/
Read The Law on Framing and follow the link to the case of Washington Post v. TotalNews
You should also check your country and local state laws, there is no such thing as a standard legal solution because it changes from one place to the other and many countries do not have laws on what you are asking. However, let me tell you, the web seems to be dominated by two frame of mind, or law philosophy:
lex mercatoria: these folks tend to think the web is commerce and commerce laws should apply, which are mostly derived by mores and civil laws
lex retis: these folks say the web is anarchy, no law should govern it
PS: I am a lawyer. Even if this is a bit complicated, I hope you can get an idea.
As far as I can tell, it only becomes a legal problem if the iframe is used to perpetrate fraud, deceptive marketing, or somesuch. Short of that, it's merely annoying. You can always use framebusters/framekillers if it bothers you enough.
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I haven't been to enough of these "live" events to really determine which, if any, are worth the time / money. Which ones do you attend and why?
For conventions, if you're still in university, and can make it to Montreal, Canada, the Canadian Undergraduate Software Engineering Conference (CUSEC) has been extremely enjoyable. See the 2009 site for the next event, and for a take on what previous years have been like, take a look at the 2008 speakers (note: it included Jeff Atwood).
I attend CUSEC primarily because our software engineering society on campus makes a point of organizing a trip to it, but also because of the speakers that present there, and the career fair.
I used to belong to my local Linux User Group which I co-founded but I treated it more as a social event than anything else but obviously a social event full of geeks is still a great way to get a great debate going :)
Conventions and the like I've not got much out of other than being pestered by businesses who can offer me nothing that is apart from a bunch of Linux and Hacker ones where I've met loads of people who I consider friends offline, again great for the social aspect but pretty worthless to me in other respects.
That's not to say I never got any business out of attending various events it's just that treating them as social occasions meant any business that did come my way was a bonus so I never left an event feeling like it was a waste of time.