Tag Archives: Great Confusions

10 Mar

What is 4G?

I can see SUPER HEAVY confusion on what is 4G? So thought to make a blog post about it.

Some people even feel like….

 

🙂 Let’s try to understand from basic definition about 4G.

As per ITU – 4G refers to wireless technologies which gives as fast as 1Gbps speeds when one is stationary, while 100Mbps speeds when one is on move. That’s it. Full stop.

 

1Gbps!!! Really?

Well, that’s “just in defination”. In real – there is no technology which is real 4G.

 

So what is WiMax?

Well WiMax is yet another technology which enables wireless broadband. WiMax comes in two flavors – fixed wimax (802.16d) and mobile wimax (802.16e). Fixed WiMax is available from long time. As per its name – “it’s fixed!”. It needs a clear “line of sight”. It works quite good as “alternate to DSL” in Rural areas where demand is very low. It’s also more suited for Rural environment because of easy line of sight clearance, apart from very long distance links (as long as 40Km’s). What WiMax we hear these days (the one which is operated by ClearWire in US, for carriers like Sprint, and BSNL wimax in India) that’s “mobile wimax”. It’s a totally different technology then fixed wimax, and both share “almost” nothing other then “name” wimax. It’s one of technologies heavily backed by Intel – who considered it as an alternate to Wifi covering whole city with just a couple of hotspots. Intel’s dream was much like having WiMax in way we see WiFi, though it seems it failed. Have a look at this promo video:

httpv://www.youtube.com/watch?v=KQdc5AdJqCg

 

So how much speeds WiMax supports? Is that 1Gbps?!!

Mmm…NO! (not even in theory).

Current version of mobile wimax supports peak (read it theoritical) speeds of somewhere around 70Mbps. (no way close to 1Gbps)

 

What about LTE?

Well that’s one of other popular wireless technology. One must note that LTE is an upgrade from GSM > GPRS/EDGE > HSDPA > HSPA+ > LTE…

meaning it is not directly related to (wireless) broadband, but it’s an evolution from cell phone technologies. That’s one of prime reasons of why people call these as 4G technology. Present LTE standard too does not support 1Gbps of speeds, and so it’s also NOT the real 4G.

 

So what’s the real 4G?

Well till now – there is no commercially available technology which can support “real 4G” speeds. Recently NTT DoCoMo did tests for Advanced LTE, and it seems that might come as real 4G. In case WiMax, an advanced version 802.16m might be real 4G, but that has years to come!

 

But till now all operators are just calling their own technology as 4G.

In US , firstly Sprint came with mobile wimax based network (running over ClearWire’s network). It gives average downlink speeds of somewhere around 4-5Mbps, which is far away from 4G standard. Next, At&t and T-mobile upgraded their 3G network to HSPA+ which supports peak speeds of 21Mbps and they call it “almost 4G network”. Next, Verizon came up with their “4G LTE network” which supports real world speeds of somewhere between 5-12Mbps. One remarkable thing here was – Verizon is atleast giving real world speeds in their claim. Wireless broadband ads are all full of “peak” theoretical speeds while at the end users just get hardly 1/5th of that (on a lucky day).

A few interesting facts:
  1. If At&t and T-mobile keep on calling their network as 4G, all Indian telecos can call their new network too as 4G as they are also deploying HSPA+ (right from start).
  2. In rough and more real sense HSPA+ is considered to be 3.5G. They give end user a speed from 3-5Mbps which is definitely good for mobile broadband.
  3. In real mobile WiMax & LTE (current standard) is 3.9G – a way to 4G. That’s why they call it as Long Term Evolution 🙂
  4. Even if LTE advanced comes into picture, we still need really big slot of spectrum. These technologies are mostly about how efficiently we are using limited spectrum.
  5. If DSL players start claiming “peak” speeds in their ads, then expect BSNL banner saying – “24Mbps for just 150Rs/month” 😛 🙂 and FTTH – Fiber to home deployments will go as high as “1.6Tbps of  peak speeds just for $60 a month”! 😀
  6. Even FTTH players like Verizon FiOS are yet not giving 1Gbps speeds. Issue remains with capacity and overall demand. (who really needs that much bandwidth today?)
  7. LTE is in picture from many years but development was very slow till mid of 2010. Reason remains high cost of building new infrastructure, and not really any significant demand.
  8. In India Reliance Infotel is expected to launch wireless broadband over TD-LTE in middle of this year. You should be excited about it – considering fact that Infotel is only player which holds pan India spectrum for BWA, apart from fact that it’s return of billionare Mukesh Ambani in communications industry.

 

 

So stop using word “4G” unless you can really download 1G of data in 8 seconds!

 

Fun fact: I am making this post after hearing from a friend that iPhone 4 is never going to launch in India since we don’t have 4G!

02 Nov

DNS Zone Propagation Time


OK ok, I agree its one of the BIGGEST confusions of world!

MOST of web host state that if you have changed your domain’s name server’s to there’s server then also it will take around 24-48 hours for DNS changes to propagate.

WRONG!!!

Correct sentence would be

If you have changed your domain’s name server’s to theirs server then also it might take around 24-48 hours for DNS changes to propagate.

no no…Still that’s just a bit of “truth!”

What I mean to say it’s just creates a wrong image of DNS working in eyes of a newbie. Let me be clear in one thing – There is NO such think like propagation between world dns server…blah..blah blah….that’s just a wrong picture.

Now lets think over it and shoot it!

Question:

What happens when you change name servers of your domain or either change the DNS records like A, MX etc?

Answer:

Case 1 – You changed any DNS Record

You modified a DNS record and hit submit key

Now all these are done on Primary Name server (generally ns1)

as soon as you change, SOA serial number on Primary name server increases its value. Now it’s a simple thing that secondary name servers keep on checking primary name server for SOA serial number up gradation as per “refresh” parameter of SOA.

When as per “refresh” secondary ns will check primary ns and detects SOA serial is increased, it will initialize a XEFR Zone transfer (XEFR – incremental of AXFR) and thus this will transfer the change to secondary name server. And thus ALL servers hosting DNS zone of your domain are updated.

BUT that was strictly behind the scene work, and here forward screen is a bit frustrating!

Lets say if I had a dns record for domain.com pointing to 11.22.33.44 and it had TTL of 3600 (1hr), my friend in same city opens it he gets through the site and finds issue with server, and I just change the hosting to other server by modifying A record to my other server say 44.33.22.11 and then here’s complexity.

I am using 2 name servers and then just say refresh value in my SOA is 300 (5mins)

now just after changing name server’s I ask my friend in other location to check site, here it is possible he sees site up, possible he sees down. As e.g. if at time of opening he hits primary DNS revolver, he will get new server’s ip BUT incase he hits secondary DNS server before 5mins of my updating to primary ns, then he will get to old faulty server and thus site will be down for him.

On other side, site will be down for 1hr for my friend who was in my city (who informed me) because as soon as he opened my site, old site’s record was cached in ISP’s revolver and thus he will keep on getting to old server until record expires as per TTL.

Thus two things effect – TTL & SOA (both, are you sure….no no…read more carefully)

That kind of working is just followed by most of private server cluster’s (common in corporate offices) but these days most of world’s dns host use advanced method and “push up” changes to secondary (slave) name servers as soon as changes are done on primary ns. This means they initialize a XEFR zone transfer without looking at refresh periods

Case 1 – You changed Name Servers of a domain

Now here two factors affect propagation largely old friend TTL & Domain Registrar

TTL affects same as done in last case as dns records get cached on ISP’s end (or any other local revolver) and thus lookup gives old records.

Registrar – yea! our domain registrar. In simple words its quality effects DNS migration! Lol

Ok how? – here it is

There are MANY poor “companies” who call themselves registrar and fool people! We can call them reseller but believe me in domain registration market you will find LOTS of good quality of resellers.

They technically effect situation as poor companies make users to operate on a CMS! Yup

They make user to login at a CMS and give a feel of domain control panel using forms!!!

This means when one changes name servers, the data is recorded BUT not comes in effect because it’s recorded! As soon as you fill up that form, it goes to company Tech. People and they modify name servers BY hands (through original control panel of a good Registrar). This makes an average delay of 5-6 hours in name server updating. Generally small web hosting company use this kind of setup, in which they registrar domain for customers and give customers a feeling that he is managing domain himself.

On other side if you use an Original Domain Registrar or a reseller having proper setup of this stuff, you will see changing name servers will take place in less then 10 seconds!

So this is actually DNS Propagation – propagation of DNS Zone file across DNS servers (hosting that domain….). I am ending up with few FAQ’s regarding the subject. Feel free to as if any confusion is still there.

[faq list DNS Propogation]

[ratings]

NOTE: You can download this post as pdf directly by clicking here