What is H1B Visa duration and I797B validity period?

I have got a mail from my company that my petition for H-1B non-immigrant visa status has been approved by the USCIS with validity dates of 10/01/2013 - 10/30/2014.The I-797B notice that I have received also mentions same validity period.

Questions from my side:

1)What is this validity period?

2)I found in net that H1B visa is generally granted for 3 years initially.In my case, H1B Visa duration will remain same as the above period mentioned in I-797B,i.e. 1 yr only?OR it might also remain under the discretion of the VO taking the interview?

3)Suppose H1B is given for 1 year,can it be extended while in US and if possible then to what duration

Any help in this regard will clear the doubts and help me to take a decision.

Thanks in advance.


I too have issue can anyone advice accordingly