How many bytes of Application Layer header length ?

[ray]

Dear guru :
Anyone could tell me ,

Q1 .How many bytes of Application layer header ?
Data(200 bytes) +AP layer header(??) + TCP header(20 bytes) + IP
header(20 bytes) + Ethernet (14 bytes) + Pad(4 bytes)
I do not know the AP layer header.

Q2: MSG A header len (2bytes) + MSG A(100 bytes)=102 bytes,
MSG B headre len (2 bytes)+ MSG B(50 bytes) =52 bytes,
Could I combine MSG A+MSG B into one DATA (154 bytes) ?

Thank all !

[Barry Margolin]

In article
<ac4c7558-c10a-40b1...@u25g2000prh.googlegroups.com>,
ray <yehr...@gmail.com> wrote:

> Dear guru :
> Anyone could tell me ,
>
> Q1 .How many bytes of Application layer header ?
> Data(200 bytes) +AP layer header(??) + TCP header(20 bytes) + IP
> header(20 bytes) + Ethernet (14 bytes) + Pad(4 bytes)
> I do not know the AP layer header.

There's no standard application layer header, it depends on the
application protocol. Many protocols don't even have a header, they're
just text streams, such as SMTP or TELNET.

> Q2: MSG A header len (2bytes) + MSG A(100 bytes)=102 bytes,
> MSG B headre len (2 bytes)+ MSG B(50 bytes) =52 bytes,
> Could I combine MSG A+MSG B into one DATA (154 bytes) ?

It depends on the protocol. If it's a datagram protocol, there's often
a requirement that each message be in a separate datagram. If it's a
stream protocol, and uses TCP as the transport, there's no way for the
application to tell how it was transmitted.

--
Barry Margolin, bar...@alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***

[ray]

On 12月16日, 下午5時35分, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article
> <ac4c7558-c10a-40b1-a055-3232efab4...@u25g2000prh.googlegroups.com>,

>
>  ray <yehray...@gmail.com> wrote:
> > Dear guru :
> >     Anyone could tell me ,
>
> > Q1 .How many bytes of Application layer header ?
> > Data(200 bytes) +AP layer header(??)  + TCP header(20 bytes) + IP
> > header(20 bytes) + Ethernet (14 bytes) + Pad(4 bytes)
> > I do not know the AP layer header.
>
> There's no standard application layer header, it depends on the
> application protocol.  Many protocols don't even have a header, they're
> just text streams, such as SMTP or TELNET.

[ray] I see UDP have header. text streams do not have header.
Thanks !

>
> > Q2: MSG A header len (2bytes) + MSG A(100 bytes)=102 bytes,
> >        MSG B headre len (2 bytes)+ MSG B(50 bytes) =52 bytes,
> >        Could I   combine   MSG A+MSG B into one DATA  (154 bytes) ?
>
> It depends on the protocol.  If it's a datagram protocol, there's often
> a requirement that each message be in a separate datagram.  If it's a
> stream protocol, and uses TCP as the transport, there's no way for the
> application to tell how it was transmitted.

[ray] It is datagram protocol. Thanks !