Chapter4-helmy-intro

Chapter4-helmy-intro - Chapter4 NetworkLayer...

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Network Layer 4-1 Chapter 4 Network Layer Computer Networking: A Top  Down Approach  4 th  edition.  Jim Kurose, Keith Ross Addison-Wesley, July 2007. 
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Network Layer 4-2 Network layer transport segment from sending  to receiving host  on sending side encapsulates  segments into datagrams on rcving side, delivers segments  to transport layer network layer protocols in every  host, router router examines header fields in  all IP datagrams passing  through it application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical
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Network Layer 4-3 Two Key Network-Layer Functions forwarding:  move packets  from router’s input to  appropriate router output routing:  determine route  taken by packets from source  to dest.  routing algorithms analogy: routing:  process of planning  trip from source to dest forwarding:  process of  getting through single  interchange
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Network Layer 4-4 1 2 3 0111 value in arriving packet’s header routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 2 1 Interplay between routing and forwarding
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Network Layer 4-5 VC implementation a VC consists of: 1. path from source to destination 2. VC numbers, one number for each link along path 3. entries in forwarding tables in routers along path packet belonging to VC carries VC number (rather than  dest address) VC number can be changed on each link. New VC number comes from forwarding table
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Network Layer 4-6 Forwarding table 12 22 32 1 2 3 VC number interface number Incoming interface    Incoming VC #     Outgoing interface    Outgoing VC # 1                           12                               3                          22 2                          63                               1                           18  3                           7                                2                           17 1                          97                               3                           87 …                          …                                …                            … Forwarding table in northwest router: Routers maintain connection state information!
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This note was uploaded on 01/28/2010 for the course CNT 5106c taught by Professor Helmy during the Fall '09 term at University of Florida.

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Chapter4-helmy-intro - Chapter4 NetworkLayer...

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