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Subtleties of mobile download

Introduction

In this article the author would like to share with readers about those subtleties of mobile download which the author had to experience with his gut as people say. The topic seems to be quite actual because of already known by many people "Giga-Internet" proposal from Life:) operator, and now also from UMC - the 24-hour unlimited access known as hyper.net.

Download equipment

To write such kind of review is impossible without mentioning the equipment that downloads files from the Net. Below there is its list, and also other details which, in author's opinion, can partially influence the final result:
  • Computer: of modern generation one;
  • OS: Windows XP Professional SP2;
  • Download manager: Reget Deluxe 4.0;
  • The operator of cellular communication: Life:);
  • Internet access package: Giga-Internet;
  • Cellular phone: Siemens A65 SW17 (GPRS class 8);
  • Means of connecting the personal computer and a cellular phone: original date-cable;
  • Data-cable marking: DCA-510.
It is necessary to mention that the author is in the city of Dnepropetrovsk, in settlement/microdistrict "Yubileyniy" (The left bank). Time of using Giga-Internet service: November, 2006 Files for download were on foreign sites - Russian and Western.

A little theory of mobile Internet

If the reader sees these lines - so he uses the Internet and for certain has his own experience of downloading files from the Net. It is not a secret, that the download procedure depends in many aspects on how the provider gives user the channel and how it is paid. Let's try to analyze "Giga-Internet" by these criteria:
  • Monthly, for fixed fee;
  • Volume of service - conditionally-unlimited package (1 GB a month for one SIM-card).
The user is stimulated in such conditions to wholly to use the volume of the traffic given to him. Package cheapness attracts even those who has the cable Internet at home, digital-leased circuit or ADSL.
Now let's consider global conditions of granting Internet access in cellular communication networks:
  • Modem connection by PPP protocol. Life assigns a dynamic real IP-address from subnets 212.58.х.х and 91.145.х.х.
  • Data transmission technologies: GPRS and EDGE.
  • Voice traffic has a priority over the Internet-traffic.
The capacity of cellular communication networks depends on such factors:
  • The standard used at the nearby base station (GSM 900/1800);
  • EDGE support by the base station.
  • Equipment congestion degree/base stations density, i.e. those conditions which the operator can either improve or cover territory simply for "sticks" presence and nominal dialing.
  • Whether the operator has free frequencies in the area of service usage, i.e. a physical limit for expansion the capacity of the cellular communication network.
The technical and economic conditions enumerated above under which "Giga-Internet" is given, it is possible to classify it remorselessly as a cheap and bad quality access using low-speed channel without guaranteed QoS (Quality of Service).

Giga-Internet: a portrait close up

Since the moment Giga-Internet was launched people not unreasonably predicted its fast end. The majority of active users of cellular communication remember well testing the Internet on Mobi and its practically full down state when required. The situation is quite similar. After the first wave of equipment overloads Life:) increased a little the capacity of the network. After that in Dnepropetrovsk there is approximately the following situation.
  • 22.00 -2.00 - Internet gradually comes to the senses and revives. Not tested later at night.
  • 5.00-9.00 - Internet is the fastest and almost without problems (very few people chat over phone at this time).
  • 9.00-17.00 - the speed is low (approximately 1 KB, but stable). Can be used with great reserve.
  • 17.00-22.00 - speed varies from 0 up to 700 B/s. Can be used for measured surfing only. It is practically useless for problem downloads (this question is going to be discussed below).
On the days off the situation is approximately the same unless the dead period begins earlier and comes to an end at late night, and its weight is so big, that data are practically not transmitted through PPP-connection.
The Internet-connections from Life:) has the following distinctive features:
  • At the shortage of modem pool capacities the latter simply terminates the process of establishing the PPP-connection. At first there is a window "Registering the computer at the network…" for a long time on the screen, and then all simply begins anew. The heaviest, critical case.
  • PPP-connection is established, however data are not transferred through it. Usually in such cases IP-addresses of the entered domain names are not resolved. The operator plays this dirty trick also when a plenty of the traffic or connection has been transferred during current session or it is active for several hours. Because of this feature there is no sense to leave a computer with an active PPP-connection for a long time without supervision; it is useless to schedule a download, leaving on work or study, going to bed not so late. Almost 100 per cent of probability, that after 4-5 or 10-15 MB (the author failed to trace the precise dependence of compulsory connection termination) of the downloaded traffic the active data transmission stops. In this Life:) made some progress: if Beeline roughly breaks PPP-connection, popping up its start window with the phone number to be dialed on the screen the "red" operator does not throw out the subscriber from the network, and quietly blocks access to the outer net, i.e. to the Internet.
  • PPP-connection is established or it is active, data are transmitted through it, however there is a problem with resolving the IP-addresses of domain names. Data are exchanged with domain names that have been resolved during the current session. Ping is successful too, but by IP-addresses only. This condition can precede a problem described in item above.
The partial decision of the latter problem can be specifying often used domain names in LMHOSTS. The author of this article uses the compressing proxy-server toonel.net for surfing , and for treatment of the resolve problem the address of the proxy-server was simply specified in LMHOSTS. Now the problem arises only at downloads through direct connection.
  • Long pinging time (from time to time) - 2-3 ms; frequent package losses. In such conditions those downloads that demand frequent exchange of service packages, for example, through ftp - are simply inefficient. Those programs which work in real-time mode - icq, jabber - simply show constant terminations and are practically disabled.

Downloads: practical recommendations

In this final section the author tries to give concrete practical recommendations to mobile download beginners, without superfluous milk and water and deepening in theory.
  • 1. Differentiate your downloads by protocols. As it is known, by way of worsening conditions it is possible to range the downloads as follows:
    • Download by usual http through the direct link.
    • Download through ftp.
    • Download through the indirect link with cookies, authorization procedure and other perversions.
  • 2. Choose optimum time for download. I think, it is not necessary to convince, that a download only in the evening - this is waste of time and nerves. For evening time the only suitable protocol is http through the direct link.
  • 3. If many packages are lost - at this time it is better to download only by http, even with authorization.
  • 4. For ftp-downloads the best time is in the morning. A guarantee of their mutually high speed will be simultaneous download by http.

Adobe's website as a masterpiece of perverted download

As it was already mentioned above, some sites offer especially refined specifications for downloading. The matter concerns, unfortunately, not only cookies. Adobe's website uses ColdFusion application server. Besides that it terribly brakes, it also demands registration without which throwing to Reget the direct link is simply useless. Theoretically it turns out, that the company suggests users to download files more than 100 MB using browser. It simply appears to be a mockery, however it is possible to assume, that thus Adobe eliminates downloading files by pirates and cheapskates from the third world. And only interception by the download manager URL from IE allows to download file normally.
So, what does Adobe offer us?
  • 1. Registration on website.
  • 2. Session cookies usage. At the request to server it generates each time session cookies. They are valid only at indissoluble connection with the server. As soon as the user pressed button "Stop" or "Pause" - the session is considered to be terminated, the cookies become void. It is necessary to pass authorization anew, and only after that ColdFusion gives out new valid cookies. When Reget is trying to use old cookies it simply downloads a web-page file.
  • 3. Even if authorization had been successfully passed, but the page hung for a while in your browser and connection with ColdFusion server has been lost, cookies are again void.
  • 4. The only way something to download from it is quickly passing authorization by good, high-speed morning GPRS rather, allowing Reget to intercept the link with valid cookies - and only then the download manager will more or less reliably "stick" to the desired file.
  • 5. If data on the channel suddenly ceased to be transferred and passed a bit of time you can to try to avoid repeated authorization by next way. Accurately tear off PPP-connection. Do not put Reget on a pause! Then quickly restore PPP-connection. There is a chance, that ColdFusion apprehends it as loss of connections and passes cookies from the interrupted session.
  • 6. How to set up Reget on interception of complex links from IE? Open the main menu item Options > Integration. In the opened window pass on вкладку Internet Explorer. Activate an option " To intercept downloads from Microsoft Internet Explorer ". Choose integration on a low level. Everything, now you can catch links with the help of Reget.
That is actually all what the author would like to narrate to mobile download beginners.