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just another bad question

Discussion in 'Networks' started by kobem, Nov 5, 2007.

  1. kobem

    kobem Megabyte Poster

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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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  2. greenbrucelee
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    greenbrucelee Zettabyte Poster

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

    newkoba Byte Poster

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    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.
     
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  4. JonnyMX

    JonnyMX Petabyte Poster

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    Put what between them?
     
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  5. BosonMichael
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    BosonMichael Yottabyte Poster

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    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?
     
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  6. Luddym

    Luddym Megabyte Poster

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    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!
     
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  7. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    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.
     
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  8. kobem

    kobem Megabyte Poster

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    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?
     
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  9. kobem

    kobem Megabyte Poster

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

    kobem Megabyte Poster

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    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
     
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  11. greenbrucelee
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    greenbrucelee Zettabyte Poster

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

    hbroomhall Petabyte Poster Gold Member

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    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.
     
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  13. Tinus1959

    Tinus1959 Gigabyte Poster

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    Try reading for two months.
     
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  14. Tinus1959

    Tinus1959 Gigabyte Poster

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    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
     
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  15. kobem

    kobem Megabyte Poster

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    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!
     
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  16. kobem

    kobem Megabyte Poster

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    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!
     
    Certifications: CCNA
  17. Fergal1982

    Fergal1982 Petabyte Poster

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    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?
     
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  18. greenbrucelee
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    greenbrucelee Zettabyte Poster

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    from my basic understanding, you are spot on, good analogy btw :)
     
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  19. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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

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

    Harry.
     
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  20. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    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.
     
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