Changes between Version 46 and Version 47 of GENIExperimenter/Tutorials/ClickExample/Execute


Ignore:
Timestamp:
07/16/14 14:47:48 (5 years ago)
Author:
sedwards@bbn.com
Comment:

--

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  • GENIExperimenter/Tutorials/ClickExample/Execute

    v46 v47  
    325325ssh -A top "tail -f /tmp/click.log"
    326326}}}
    327   i. Go to your window for '''hostA''', where your '''nc''' command is still running. Type a message into this window. You should see a log message in three of your four router windows.
     327}}}
     328
     329{{{
     330#!div style="background: #ddf; border: 2px ridge; width: 685px; margin-left:50px;"
     331ii. Go to your window for '''hostA''', where your '''nc''' command is still running. Type a message into this window. You should see a log message in three of your four router windows.
     332   {{{
     333[mberman@hostb ~]$ nc -ul 24565
     334your message here
     335   }}}
     336}}}
     337
     338
     339{{{
     340#!div style="background: #ffd; border: 3px ridge; width: 685px;"
     341
    328342  i. In the local terminal you will see:
    329343  {{{
    330344outR:   76 | 000423b7 192e0004 23b71ce0 7744416c 69636557 61734865
    331 }}}
     345  }}}
    332346  This log entry says that the '''top''' router received a packet from '''hostA''', modified it, and sent it out to the '''right''' router. If the entry started with '''outL''', that would indicate that it sent the packet out to the '''left''' router. Let's look a bit at the start of the packet (the first 24 bytes are logged). It starts with an Ethernet header. The first six bytes are the MAC address of the destination interface, that's 00:04:23:B7:19:2E, the MAC address of '''eth4''' on '''right'''. The next six bytes are the MAC address of the source interface, 00:04:23:B7:1C:E0, or '''eth4''' on '''top'''. Next comes your ether type, 0x7744. The remaining bytes, "416c 69636557 61734865" are the start of the first field in your new protocol, "!AliceWasHe" in ASCII.
    333   i. Try typing a few different lines to hostA. You should see some packets routed to the left and some to the right. The routing decision is based on the '''route :: Classifier(27/01%01,-);''' entry in the '''top''' router configuration. Here, the router is looking at the low-order bit of the checksum on the initial IP packet (now at byte position 27 with the addition of the new sixteen byte field at the start of the header). Packets with odd checksums go to the left; those with even checksums go right.
     347}}}
     348
     349{{{
     350#!div style="background: #ddf; border: 2px ridge; width: 685px; margin-left:50px;"
     351  i. Try typing a few different lines to '''hostA'''. You should see some packets routed to the left and some to the right. The routing decision is based on the '''route :: Classifier(27/01%01,-);''' entry in the '''top''' router configuration. Here, the router is looking at the low-order bit of the checksum on the initial IP packet (now at byte position 27 with the addition of the new sixteen byte field at the start of the header). Packets with odd checksums go to the left; those with even checksums go right.
    334352}}}
    335353