INFORMATIO
chapter_5_2015(1).pdf

Protocol type contains the protocol address type for

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Protocol Type: contains the protocol address type (for IP is 0x800). Hardware Address Length: the physical address length (for Ethernet is 6). Protocol Address Length: the protocol address length (for IPv4 is 4). Operation: is the command; in our case we'll see ARP Request and ARP Replay Sender HA, IP: the H/W and IP address of the sender Target HA, IP: the H/W and IP address of the target Page 5a-27 Address Resolution Protocol (ARP) Header Decoding (3) Determine the header information of the following packet. FF FF FF FF FF FF 00 0C DB 56 7C 00 08 06 00 01 08 00 06 04 00 01 00 0C DB 56 7C 00 C1 E3 33 C1 00 00 00 00 00 00 C1 E3 33 D1 00 Sol. - DA=FF:FF:FF:FF:FF:FF - SA= 00:0C:DB:56:7C:00 -Protocol: 0x806 ARP - Hardware Type: 0x0001 -Protocol Type: 0x800 (IP protocol) - HLEN=0x06=6 bytes -PLEN=0x04=4 - Operation=0x01 ARP Query H/W SA= 00:0C:DB:56:7C:00 IP SA=C1.E3.33.C1=193.227.51.193 H/W DA= 00:00:00:00:00:00 IP DA = C1 E3 33 D1 = 193.227.51.206 Page 5a-28
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ICMP Header Decoding (1) It is the responsibility of the network layer (IP) protocol to ensure that the ICMP message is sent to the correct destination by: Setting the destination address of the IP packet Setting the source address of the computer generating the ICMP ECHO request The IP protocol type is set to "ICMP" (01) The format of an ICMP message is shown Page 5b-29 ICMP Header Decoding (2) ICMP Message Types Echo Request (8) Echo Replay (0) Destination Unreachable (3) Time Exceeded (11) Redirect (route change) (5) Traceroute (30) there are more ... Many of these ICMP types have a "code" field that indicates the reason of the error message. The "ping“ and Traceroute programs contain client interface to ICMP. Page 5b-30
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ICMP Header Decoding (3) 00 0C DB 56 7C 00 00 30 4F 11 72 98 08 00 4 5 00 00 3C 70 07 00 00 80 01 E1 21 C1 E3 33 CE C1 E3 32 03 08 00 4A 14 01 00 02 48 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 72 73 74 75 76 77 61 62 63 64 65 66 67 68 69 Sol.: IP header (0x800) - Protocol type = 01 ICMP - source IP = C1.E3.33.CE = 193.227.51.206 - Dest. IP = C1.E3.32.03 = 193.227.50.3 ICMP header - Type= 0x08 Echo Request - Operation Code = 0x00 = Page 5b-31
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  • Spring '16
  • Sameh
  • Internet Protocol Suite, User Datagram Protocol, Address Resolution Protocol

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