port question

[Tony Alfrey]

Bruce Marshall wrote:
> On Sunday 23 August 2009, Tony Alfrey wrote:
>> Yes, thanks, it is very clear! I'm just wondering about the actual
>> packet of bits that is assembled at each layer.  My understanding is
>> that the port ID is part of the bit stream that makes up the packet.  If
>> this packet starts out from ME where I (my mail client) put in an ID of
>> port 587 into the header that precedes the data bits, does an additional
>> piece of header get added (perhaps at the sending SMTP server end) with
>> an ID of port 25 so that it makes it to the receiving SMTP server?
> 
> I suspect that your ISP is relaying the mail to wherever it is going....  They 
> receive the mail, then send it on....  more than just changing ports on a 
> packet.

OK!  Thanks for all the info.



-- 
Tony Alfrey
tonyalfrey at earthlink.net
"I'd Rather Be Sailing"