2017-04-09 00:18:44 +08:00
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Optimal 6loWPAN Configuration
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2017-04-08 21:30:20 +08:00
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1. Link local IP addresses:
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128 112 96 80 64 48 32 16
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fe80 0000 0000 0000 xxxx xxxx xxxx xxxx
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2. MAC-based IP addresses:
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128 112 96 80 64 48 32 16
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---- ---- ---- ---- ---- ---- ---- ----
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xxxx xxxx xxxx xxxx xxxx 00ff fe00 MMMM 2-byte Rime address IEEE 48-bit MAC
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fe80 0000 0000 0000 NNNN NNNN NNNN NNNN 8-byte Rime address IEEE EUI-64
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Where MMM is the 2-byte rime address XOR 0x0200. For example, the MAC
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address of 0xabcd would be 0xa9cd. And NNNN NNNN NNNN NNNN is the 8-byte
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rime address address XOR 02000 0000 0000 0000
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3. MAC based link-local addresses
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128 112 96 80 64 48 32 16
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---- ---- ---- ---- ---- ---- ---- ----
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fe80 0000 0000 0000 0000 00ff fe00 MMMM 2-byte Rime address IEEE 48-bit MAC
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fe80 0000 0000 0000 NNNN NNNN NNNN NNNN 8-byte Rime address IEEE EUI-64
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4. Compressable port numbers in the rangs 0xf0b0-0xf0bf
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5. IOBs: Must be big enough to hold one IEEE802.15.4 frame (CONFIG_NET_6LOWPAN_FRAMELEN,
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typically 127). There must be enough IOBs to decompose the largest IPv6
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2017-04-09 00:18:44 +08:00
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packet (CONFIG_NET_6LOWPAN_MTU, default 1294, plus per frame overhead).
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Fragmentation Headers
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---------------------
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A fragment header is placed at the beginning of the outgoing packet when the
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payload is too large to fit in a single IEEE 802.15.4 frame. The fragment
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header contains three fields: Datagram size, datagram tag and datagram
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offset.
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1. Datagram size describes the total (un-fragmented) payload.
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2. Datagram tag identifies the set of fragments and is used to match
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fragments of the same payload.
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3. Datagram offset identifies the fragment’s offset within the un-
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fragmented payload (in units of 8 bytes).
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The length of the fragment header length is four bytes for the first header
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(FRAG1) and five bytes for all subsequent headers (FRAGN). For example,
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this is a HC1 compressed first frame of a packet
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c50e 000b ### 4-byte FRAG1 header
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01 08 01 0000 3412 ### 7-byte FCF header
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42 ### SIXLOWPAN_DISPATCH_HC1
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fb ### RIME_HC1_HC_UDP_HC1_ENCODING
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e0 ### RIME_HC1_HC_UDP_UDP_ENCODING
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00 ### RIME_HC1_HC_UDP_TTL
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10 ### RIME_HC1_HC_UDP_PORTS
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0000 ### RIME_HC1_HC_UDP_CHKSUM
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4f4e452064617920 48656e6e792d7065 6e6e792077617320 7069636b696e6720 ### 80 byte payload
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757020636f726e20 696e207468652063 6f726e7961726420 7768656e2d2d7768
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61636b212d2d736f 6d657468696e6720 g
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This is the second frame of the same transfer:
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e50e 000b 0a ### 5 byte FRAGN header
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01 08 01 0000 3412 ### 7-byte FCF header
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6869742068657220 75706f6e20746865 20686561642e2027 476f6f646e657373 ### 88 byte payload
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2067726163696f75 73206d6521272073 6169642048656e6e 792d70656e6e793b
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202774686520736b 79277320612d676f 696e6720746f2066
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The payload length is encoded in the LS 11-bits of the first 16-bit value:
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In this example the payload size is 0x050e or 1,294. The tag is 0x000b. In
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the second frame, the fifth byte contains the offset 0x0a which is 10 << 3 =
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80 bytes, the size of the payload on the first packet.
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