[CALUG] DoD/OSI Layer 2, 3 and 4 in the real world -- WAS: open ports

[Joel J.]

GGR> Yes, every application that talks over the network or within the
OS itself has a port, it may be a temporary port, but it is
GGR> present. In fact when 1 app talks to another app within the same
server/pc, a port is opened for communication. It may not be
GGR> seen on the network, but it is still present.

I'm going to have to go with Brian on this one.  For example, I
present the humble ping application.  It communicates with another
computer across a network, yet does not use a port.

--Joel

On Thu, Sep 15, 2011 at 4:56 PM, Rajiv Gunja <opn.src.rocks at gmail.com> wrote:
> Sorry Bryan. I cannot accept your answer.
>
> GGR> So, irrespective of the application, everything communicating
> GGR> over the network has a port address.
>
> BJS> This is _false_.  Not trying to be anal here, but understand my initial
> response was hoping to avoid the mega-oversimplification that I'm BJS>
> seeing too often.  I was afraid it would go here.
> Yes, every application that talks over the network or within the OS itself
> has a port, it may be a temporary port, but it is present. In fact when 1
> app talks to another app within the same server/pc, a port is opened for
> communication. It may not be seen on the network, but it is still present.
> About using tcpdump/snoop(solaris) over netstat. True netstat gives network
> information, it is a good step to get on to learn about network traffic. But
> for running it on a PC, it does not matter (since we are all behind a router
> at home).
> Also, to learn something, we need to simply stuff first, else we will drive
> away folks who want to learn. If we make things sound like brain surgery,
> then no one will want to learn about subjects.
>
> --
> Rajiv G Gunja
> Blog: http://ossrocks.blogspot.com
>
>
> On Thu, Sep 15, 2011 at 16:22, Bryan J Smith <b.j.smith at ieee.org> wrote:
>>
>> > So, irrespective of the application, everything communicating
>> > over the network has a port address.
>>
>> This is _false_.  Not trying to be anal here, but understand my initial
>> response was hoping to avoid the mega-oversimplification that I'm seeing too
>> often.  I was afraid it would go here.
>