Links. The world is moving on from modems over voice channels, better technologies are widespread. Also, V.90 and V.92 achieve the fastest rates that can theoretically be achieved through a standard voice channel, so there is not a lot of room for growth!
(a) "Hello {world}" is the bytestream (hex)
48 65 6c 6c 6f 20 7b 77 6f 72 6c 94
Under SLIP this becomes
c0 48 65 6c 6c 6f 20 7b 77 6f 72 6c 94 c0
with framing.
(b) Now we get
7e ff 03 00 00 48 65 6c 6c 6f 20 7b 77 6f 72 6c 94 20 79 7e
The checksum algorithm is the same as used in Ethernet.
Links. Of course, there is no simple solution to this question: some reflection on the various technologies is expected. MPLS and ATM can actually run side-by-side, so they can be deployed together.
Links. There are (at least) ADSL, CDSL, HDSL, IDSL, PDSL, RADSL, SDSL, SHDSL, UDSL, VDSL and their variants (e.g., ADSL2).
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