just another bad question

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i want to give them end , i try for it but another one .............

in addition my purpose is not to bother you .

...........................

think there are two workstations (pc1 and pc2)each are in different networks and assume you put between
them.

a packet has left the pc1 by being implemented encapsulation process from 7 to 1 (layers)
then it came to router's interface(to local side) and router received it then
took it out to network layer . After that , sent it by putting it into physical layer


BUT this packet had TCP rules (while going out pc1) when it came to router , router could take it out
to network layer BUT NOT 4TH LAYER

so during router process , where did the reliability of packets go ?

 

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Kobem please will you read and understand the replies to your other questions.

 

i'm not even sure if they know what they're asking. that question makes absolutely not sense. oh yes please listen to the rest of the crowd and read some materials on the network+. that way you can answer a good portion of your questions. also google ftw. http://www.mcmcse.com/comptia/network/networkplus.shtml

you should be able to get some information from that site that you may find beneficial.

 

Put what between them?

 

Studying Network+ will enable you to understand the OSI layers.

...there's a reason I'm suggesting Network+ to you over and over again... why are you resistant to it?

 

I'm with BosonM on this one again.

You have no clue as to what you are asking, so how do you expect us to answer.

Please, please, please do yourself a favour and start studying for the N+. Or at least get a basic networking book!

 

It didn't go away. As you said - the 1st and 2nd layers are removed by the router. But 'reliability' is in the 3rd and 4th, so haven't gone away.

Harry.

 

i forgot it , i would say a router!

shortly , after a packet has left the pc1 and taken by a router , because of it has been taken out
to 3th layer at most , reliability of the packet will not exist .

when the router handed the packet to physical layer to send it to pc2 , there will be no TCP rule just checksum.(no sequence numbering , no ack , no flow control..)

at that time what is the benefit of using TCP on end hosts?

 

but packet doesn't go up to 4TH layer in router!

 

i have been reading network+ materials for two days also i solve tests about it but it is a basic CCNA
and everything in it is almost same

 

If it is so basic why do you ask questions you should know the answer to?

 

I'm not sure what you are trying to say here. I feel that TCP is a combination of 3rd and 4th layers. In any case, TCP and IP packets are preserved in a router (althought the router will decrement the TTL field). It is layer 1 and 2 that are stripped.

Harry.

 

Try reading for two months.

 

Not quite Harry. TCP is only layer four. Routing is basically changing the IP-address in the packet. That's layer three. Layer four is not affected by the router unless you have some filtering done there.

I find this animation an eye opener, allthou it does not cover the details.
http://www.warriorsofthe.net/movie.html

 

trying again in a different way

think you have pc1 and pc2 those are in different networks

-pc1 wants to send packet to pc2

-assume there is a router among these

- packet leaves the pc1 but before leaving , processes done from layer 7 to layer 1

- then this packet came to local side interface of router

- router does his own job up to layer 3
-and while sending it to find the destination host (pc2) it searches which network it is in

- puts it to cable(physical layer) ............

BUT as i said above , router does his job up to 3 , where did the TCP reliability concerns go?

note : i asked this because i had a look at for IP PROTOCOL and
there is written "unreliable , no error checking .... just checksum"

regarding to note i asked this question!

 

trying again in a different way

think you have pc1 and pc2 those are in different networks

-pc1 wants to send packet to pc2

-assume there is a router among these

- packet leaves the pc1 but before leaving , processes done from layer 7 to layer 1

- then this packet came to local side interface of router

- router does his own job up to layer 3
-and while sending it to find the destination host (pc2) it searches which network it is in

- puts it to cable(physical layer) ............

BUT as i said above , router does his job up to layer 3 , where did the TCP reliability concerns go?

note : i asked this because i had a look at for IP PROTOCOL and
there is written "unreliable , no error checking .... just checksum"

regarding to note i asked this question!

 

Pardon my miniscule understanding of networking, but my understanding was that, whilst a router processes only certain levels of the packet (im being vague here since i dont really know the terminology, etc that well), it doesnt actually strip out the data from other layers. it just does nothing with them.

Or am I wrong in that assumption? Surely if it stripped out the data from other layers it would render the packets useless, since the other layers contain information relevant to the programs on the recipient receiving them. removing the data would mean that the information would be useless.

Think of the postal service (An analogy, as I recall, that has been used in answer to one of your previous questions Kobem). I write a letter (Data) and stick it in an envelope. The envelope (Packet) is then posted, where it is picked up by the postal service (Router). The router looks at the information on the Packet (Whatever layer that is in TCP terms), and routes it according to that information. But (unless the postal service is shite) it doesnt actually rip open my letter and remove the contents. When its delivered to the correct address (host), its opened by the intended recipient (Application) and its contents are read.

At no point in that example are the other 'layers' actually removed.

Or am I totally wrong with this?

 

from my basic understanding, you are spot on, good analogy btw

 

They didn't 'go' because layer 3 is still intact.

This is why TCP is put above IP - it provides the reliability.

Harry.

 

A router removes layer 1 and 2. All the higher layers are kept, so no data is lost.


Here is a diagram that may help. Read the articles that surround it.

Harry.