Changes between Version 8 and Version 9 of GEC15Agenda/AdvancedGENITopoOmni/Instructions/ClickExampleExperiment


Ignore:
Timestamp:
10/19/12 03:12:11 (7 years ago)
Author:
nriga@bbn.com
Comment:

--

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  • GEC15Agenda/AdvancedGENITopoOmni/Instructions/ClickExampleExperiment

    v8 v9  
    379379This configuration just blindly forwards packets. It picks up any packet from the '''top''' router, updates the Ethernet header, and passes it along to the '''bottom''' router. The same applies in the reverse direction.  Again, the configuration for the '''right''' router is exactly analogous.
    380380
    381 === 8. Monitoring your core network ===
     381=== 7c. Monitoring your core network ===
    382382
    383383Let's watch how the packets travel through the network.
     
    391391outR:   76 | 000423b7 192e0004 23b71ce0 7744416c 69636557 61734865
    392392}}}
    393 
    394393  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.
    395 
    396   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.
     394  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.
    397395
    398396== 9. Clean up ==