Protocol

This is documentation for a reliable protocol over UDP.

Description

Data transfering is done using Selective Repeat ARQ.

That uses insights from an article "An Efficient Selective-Repeat ARQ Scheme for Satellite Channels and Its Throughput Analysis"

P. Yu and Shu Lin, "An Efficient Selective-Repeat ARQ Scheme for Satellite Channels and Its Throughput Analysis," in IEEE Transactions on Communications, vol. 29, no. 3, pp. 353-363, March 1981, doi: 10.1109/TCOM.1981.1094999.

Discriminants

Type	Discriminant
INIT	0000
DATA	0001
DATA_OK	0101
NAK	0110
KEEP_ALIVE	0010
INIT_OK	0011
KEEP_ALIVE_OK	0100
SYN	0111
SYN_ACK	1000
SYN_ACK_ACK	1011
FIN	1001
FIN_OK	1010

Layout

INIT

28 bytes:

d: 4 bits for discriminant
p: 11 bits for payload size (valid range [1-1500])
s: 32 bits for transfer size in bytes
n: 22 bytes for name (s in little endian)

0123456789abcdef	0123456789abcdef
ddddppppppppppp0	ssssssssssssssss
ssssssssssssssss	nnnnnnnnnnnnnnnn
nnnnnnnnnnnnnnnn	nnnnnnnnnnnnnnnn
nnnnnnnnnnnnnnnn	nnnnnnnnnnnnnnnn
nnnnnnnnnnnnnnnn	nnnnnnnnnnnnnnnn
nnnnnnnnnnnnnnnn	nnnnnnnnnnnnnnnn
nnnnnnnnnnnnnnnn	nnnnnnnnnnnnnnnn

DATA

4 bytes + payload:

d: 4 bits for discriminant
s: 28 bits for sequence number

0123456789abcdef
ddddssssssssssss
ssssssssssssssss
......data......

DATA_OK, NAK, SYN_ACK, SYN_ACK_ACK

4 bytes:

d: 4 bits for discriminant
s: 28 bits for sequence number

0123456789abcdef
ddddssssssssssss
ssssssssssssssss

KEEP_ALIVE, INIT_OK, KEEP_ALIVE_OK, FIN, FIN_OK

1 byte:

d: 4 bits for discriminant

0123456789abcdef
dddd0000........

Ddystopia/protocol