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Linux Howtos: C/C++ -> simple tutorial on using sockets

• seq & ack
• TCP payload: deliver a single file

• building a header with char* in C

  using the pack() and unpack() function. They take a series of numbers and parameters specifying each number's type (int, short, long) and return the bit format of the bits.

  Here is an example command to 'pack' the header into it's bit format:

  bitHeader = pack( 'HHLLBBHHH', source, dest, seq, ack_seq, offset, unusedFlags, windowSize, check, urg_ptr )
  'HHLLBBHHH' is the format of the bits. H stands for short int (2 bytes), L stands for int (4 bytes) B is binary (1 byte)

  Now you can just append the packet payload to this bit header, send it through the link, get the packet on the other side and remove the first 32 characters from the packet (think header = packet[:32]) unpack them and now on the other side you have a tuple of all your packet header values!

newudpl
[-i sorce_host[[:|/][port|*]]] [-o dest_host[[:|/]port]]
[-s link_speed] [-d delay] [-e Ethernet_speed] [-q queue_buf_size]
[-B bit_error_rate] [-L random_packet_loss_rate] [-O out_of_order_rate]

Commenting out line 161 in sysdep.h worked for me (I'm using Mac OS X, 10.11.3).

the RTT computation is only updated for original segments. You can also see the gory details in https://tools.ietf.org/html/rfc6298 (only sections 1 through 3 are likely relevant since we don't worry about timer granularity for this assignment).

TCP MUST use Karn's algorithm for taking RTT samples. That is, RTT samples MUST NOT be made using segments that were retransmitted (and thus for which it is ambiguous whether the reply was for the first instance of the packet or a later instance).

I found a suggestion to use an initial timeout length of 3s, and then commence using RTT and devRTT after two RTT measurements.

RFC 1323 [JBB92]
suggests that TCP connections utilizing large congestion windows
should take many RTT samples per window of data to avoid aliasing
effects in the estimated RTT.

• timeout

design window

• divide and deliver a single file