| Commit message (Collapse) | Author | Age | Files | Lines |
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test-link now also plays an attacker: packets changed on the way,
packets of the past sent again from the sender's address and its own,
keys and sources not allowed, and a flood of made-up packets. It found:
- A nonce used twice: a receiver sealed every answer in its one run, and
a sender at rest coming back with the same run got a new slot whose
answers began at number 0 again under the same key. Each slot now
draws the run its answers are sealed in.
- A link stopped for good by one packet of the past: a stream that did
not know its last heard (after a restart or a rest) handed over from
its first record held, and a stale part of an old one never came
whole. It hands over from its first whole record.
- Answers taken away: any packet that opened, however old, moved where
answers went. Only the newest of its run moves it now; a new address
is sent a challenge the sender says back (CHALLENGE, RESPONSE), and
until then gets at most three times the bytes that came from it.
- An answer made by a packet that did not open: a number heard before
was acknowledged before the packet was opened. It is opened first.
- An old answer lowering the sender's credit, or its gap making it send
again: the sender now sends up to the most heard and credit it was
told, and takes a gap only from a word not older than it knows.
- Ten thousand made-up packets made ten thousand keys: keys made for a
run that did not open now cost a token, 256 a second.
Counts now say runs keyed and secrets made.
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A sample of 0 (a path within one clock tick, or a test's) made the
pacing rate the window over 0, and its bytes infinity times 0: NaN,
after which the sender never sent again. CUBIC's time-based estimate
divided by it too. The RTT they take is at least a microsecond.
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(097)
M6 of design 011: with a 50 Mbit/s bottleneck, a link carries 21-41
times quinn's goodput when packets reorder, the same under random loss,
and 1.3-3.5 times with both; its p99 at 50 records a second is the same
or shorter; beside TCP CUBIC it takes 0.48-0.55 of the path, inside the
guardrail. Only on a clean path is it 3-5% below quinn.
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With a fixed delay the drop-tail queue dropped one flow's packets eight
times as often as the other's by their phases alone (Floyd and Jacobson,
1992): Pure took 0.63-0.77 of the path from TCP and 0.69 from quinn,
0.47 from itself, and 0.49 under fq_codel. With 1 ms of jitter it takes
0.53 at an RTT of 20 ms.
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Linux's CUBIC and quinn's keep it so; RFC 9438's whole datagram once
past the window before the event is left out.
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acknowledgments
Packets go at the window an RTT, a quarter more (twice in slow start),
up to 2 ms of it at once (10 to 256 datagrams, RFC 9002 7.7); the sender
says when the next may go. The Reno-friendly estimate grows by the
acknowledgments (RFC 9438) or by time (RFC 8312), whichever is ahead, so
a link its app holds back to a few records a second does not fall
behind it.
In the M6 simulator (RTT 100 ms, 5% loss, 50 records a second) the
median time a record takes falls from 134 to 51-71 ms and the p99 from
about 900 to 290-350 ms; a backlog with 1% loss at RTT 20 ms goes at
8.3 Mbit/s. The transport's CPU a record is unchanged.
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The TCP flow started first and in a thread of the runner; two TCP flows
split 0.31 to 0.56. Now every flow is a process started at once, run
40 s, counted from 10 s on.
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acknowledged
A link starts at 1,200 bytes; once an RTT is known it sends a PING padded
to 1,452 (DPLPMTUD, RFC 8899), alone and with the don't-fragment bit,
and uses that size once it is acknowledged. A probe lost is no
congestion; it is tried again a second on, three times, then ten minutes
on. GSO is asked for each burst (a control message), not the socket, so
a packet sent alone is never cut. CUBIC counts in the datagram.
On loopback packets fall by 19-27%; the CPU a record falls 13% at 1 KiB
and 7% at 16 KiB; in the simulator of a 50 Mbit/s path with 1% loss the
goodput rises from 6.1 to 7.0 Mbit/s (5%: 2.3 to 3.0).
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tbf with netem under it lost tbf's queue (netem became it), and the
answers queued behind the data. Now each way has its netem, the way to
the receivers' ports then a tbf whose queue holds a round trip; the way
back does not queue. transport.c takes its listener's port
(TRANSPORT_PORT).
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A record that does not fit what is left of a packet goes in part when at
least 64 bytes fit; its parts keep their cuts, so what a packet carried
is whole parts. The receiver keeps the spans it had of a record, and a
record coming in order from its start fills the line's tail with no
allocation. Packets fall by 8% for 1 KiB records and 10% for 16 KiB;
the CPU a record is the same at 61 B and 1 KiB and 5% less at 16 KiB.
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From the one after the last heard, letting be the ones heard before and
stopping at a gap: the listener's first delivery may begin past it when
packets reorder, which the harness counted as wrong.
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020-lossy-paths/run.py runs each case in an unprivileged namespace: a
50 Mbit/s tbf bottleneck under netem's delay, jitter and loss, both
ways. A link may send without UDP GSO (pure_link_gso), as netem takes a
burst as one packet; quinn the same (QUIC_GSO=0). transport.c and the
quinn harness give the records handed over in each 100 ms, and at a
steady rate the time each took; TCP CUBIC flows run beside them.
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A packet called lost stays known a while; acknowledged after all, it
came late: what it carried counts as received, the reordering awaited
grows (later packets acknowledged, and time past the RTT, as RACK), and
an episode of congestion events whose losses all came late is undone.
The window grows only when it was used (RFC 9002 7.8), and congestion
avoidance is CUBIC (RFC 9438), as quinn's.
In a path of 50 Mbit/s whose packets reorder by up to 5 ms, with no
loss, a link carried 1.5 Mbit/s at an RTT of 20 ms and 10 at 100 ms; now
43.6 and 40.1, as without reordering (research/experiments/020-lossy-paths,
virtual time). With 1% random loss: 4.9 to 6.1 at 20 ms, 1.0 to 1.3 at
100 ms. The transport's CPU a record is unchanged.
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links.c was a second implementation of the packet format; each device is
now a PureLinkSender on a socket of its own, keyed with a secret made
outside (pure_link_sender_shared: a key kept elsewhere, or a test's
many). M1 (1k, 10k) and M2 (10k, kill -9) pass with it: no silent step,
caught up in 0.2 s, every order applied once; the slowest store after
the restart is now the sender's 1 s wait for a word of the save
(STORED_WAIT), where the old devices tried again after 200 ms.
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link/link-protocol.h is the protocol with no socket, thread or clock of
its own: packets and time in, packets out. link/link.h carries it over
UDP as before. A sender starts small (8 flights, 16 records, a 4 KiB
ring) so one thread can hold many. The transport's CPU a record is the
same within 2% (five rounds each way, 61 B to 16 KiB).
test-link runs both sides through a network of its own: loss, packets
held back and doubled, failed saves, an idle sweep, and both sides
starting again, every record applied once as sent.
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A sender takes its messages' shape, and a listener asks its host which
input a stream goes to. The core gives the shape (pure_module_shape);
link/ now builds without the core's headers.
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libpure-link.a holds them; pure-serve and the M5 harness link it instead
of naming its source files.
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Between two pure-serve nodes, 16 KiB records drain at 33,600 a second
(23,000 before), the links spending 58 us a record (76), under quinn's 60
while the receiver also stores each one. 1,013 bytes: 406,000 a second
(347,000). Saving sends one by one: 5,000 of 16 KiB in 0.91 s (84.8).
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The sends not yet trimmed were written whole into the links value at
every save, as the numbers heard were: a sender whose receiver is away
or slow saved all its waiting sends again with each new one. They are
now a runtime list {output (its name), seq, payload}, in the order sent,
stored as a list state is (image "0sent" and its changes in the log). A
send is a change of the list with its event; a trim lets the sends go at
once and a failed save brings them back; the host sees the saved ones
(sent_saved). Outputs are named in the items, so a module replaced keeps
them without moving anything; one that lacks or changed an output with
sends left is refused as before. Links stored before (PLK1, PLK2) move
their sends to the list at a start and are stored again without them
(PLK3).
A list field may now hold any bytes (kind 2), unchecked, besides a number
and a UTF-8 text.
Saving 5,000 sends of 16 KB one by one took 84.8 s and left a store of
400 MB; now 0.91 s and 144 MB. 20,000 of 61 bytes: 8.4 s, now 2.9 s.
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M5 of design 011. At first a link spent eight times quinn's CPU on a small
record: scans of the backlog, a system call and allocations a record, 19
bytes of framing. After the seven changes before this one, the transport
alone (transport.c; a backlog drained, every record checked) spends per
record 0.30 us for 61 bytes (quinn 0.27: 1.06 to 1.12 times over three
campaigns, at the design's 10 % line), 2.91 us for 1,013 bytes (quinn
3.88) and 45.2 us for 16,013 bytes (quinn 60.9): 25 % less for the larger
ones, and 30 % more records a second. What is left for small records is
per packet: the stream's names and the RECORDS head. quinn's numbers carry
no confirmation of storing and no exactly once.
Between two pure-serve nodes the links spend more per record, woken at
the receiving app's pace. Filling the sender showed the outbox is written
whole at every save, as the numbers heard were (094): the next thing to
change.
run.py gains --transport and --drain; the quinn service reads a drain a
chunk at a time and its client writes 64 KiB at a time.
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A record over a piece (1,000 bytes) went in pieces even when it fit the
packet whole: a record of 1,013 bytes went as two RECORD frames, and the
receiver gathered it the slow way (an allocation, pieces, then onto the
line). A record none of whose pieces went yet now goes whole in a RECORDS
frame whenever it fits what is left of the packet; its pieces are marked
sent together. A record too large for a packet, or one resent after
some of its pieces were lost, still goes in pieces, and a receiver takes
a record whole or in pieces alike.
The transport alone takes 2.85 us a record of 1,013 bytes, not 3.18
(quinn: 3.90). transport.c now checks every record delivered: in order,
once each, its bytes as sent. None was wrong in a network namespace with
1 ms of delay, 3 % loss and 10 % reordering, with records of 61, 1,013
and 16,013 bytes.
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A queued record had an allocation of its own for its bytes and its
pieces' states, freed when the receiver stored it. Records come and go in
order, so their bytes now go one after another into a ring, never cut by
its end, and go back as the ring's head moves past the ones stored; a
ring too small grows to twice its size, the records moved into it in
order. A record of one piece keeps its piece's state in itself.
The transport alone drains 200,000 records of 61 bytes at 5.3 to 6.5
million a second; per record the link takes 0.137 us, the listener 0.14:
0.28 in all, against quinn's 0.26 a message over one stream.
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A receiver copied each record into an allocation of its own, copied them
all again into a delivery, and freed each once stored: about 110 ns a
record of 61 bytes. Once the last number heard is known, whole records
that come in order now go onto the stream's line as a delivery carries
them (u32 size, bytes). The line is handed over as it is, and let go by
moving its head; its front is given back when there is no room at its
end. Records that come early or in pieces, or before the last heard is
known, still wait in held, and move onto the line once it reaches them.
The transport alone: the listener took 0.20 us a record of 61 bytes, now
0.15; with the link, 0.31 us a record in all, against quinn's 0.26.
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changes
A listener's socket now asks for GRO: the kernel hands over the datagrams
of one sender that came one after another as one buffer, each the
segment's size but the last, and on the loopback a burst sent with GSO
comes whole instead of cut into datagrams. The listener takes up to eight
such buffers at once. It gives its AES-GCM context a key only when the
packet's run has another than the one it holds, for opening and for
sealing answers.
The transport alone drained 200,000 records of 61 bytes at 4.2 million a
second (0.454 us a record, both sides); now at 4.9 million (0.394 us).
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A RECORD frame carries a number, a size, an offset and a length before
each record's bytes, 19 bytes: a packet held 13.7 records of 61 bytes. A
RECORDS frame (0x06) carries the first record's number and a count, then
whole records whose numbers follow on, each its size as a varint and its
bytes: 17.2 a packet. A piece of a record larger than a piece still goes
in a RECORD frame; a receiver takes both.
The transport alone (research/experiments/019-idle-links/transport.c)
drains 200,000 records of 61 bytes in 11,600 packets instead of 14,600;
per record the link takes 0.217 us and the listener 0.23, 0.447 us in all,
against quinn's 0.43 a message over one stream.
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Every queued record wrote the link's eventfd, a system call each, and woke
the thread to send a packet of a few records. A record queued now wakes
the thread only when it sleeps and nobody woke it yet; one queued while it
sends marks the link, and the thread looks again before it sleeps. With
records queued one at a time as fast as a thread can, 200,000 small ones
went at 400k a second, and now at 730k; queuing one costs 0.43 us, not
1.0.
research/experiments/019-idle-links/transport.c measures the transport
alone: a link and a listener in one process, no app, no store. A backlog
of 200,000 records of 61 bytes drains at 3 to 4 million a second, 0.24 us
a record on each side.
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A backlog made the link slow in its square: the sender looked at every
queued record's pieces twice a turn to know whether any waited to be
stored, and the receiver moved all its held records down each time it let
the first one go.
- The sender counts the pieces received and not stored, and keeps where
the unsent ones begin; every change of a piece's state goes through one
place that keeps both.
- The receiver keeps its held records from a head index. One in order goes
last, and one out of order finds its place by halving. The record's bytes
and its pieces' marks are one allocation.
- Packets go in bursts with UDP GSO, 54 at a time: 0.45 us a packet on this
Pi, against 2.4 us for a send each. A full packet is padded to a whole
datagram (PADDING frames, as QUIC does). Datagrams are taken 64 at a time
(recvmmsg).
Twenty thousand saved sends of 61 bytes drained at 370k a second; now at
990k. Per record, the sender's link thread took 1.1 us and now takes 0.5;
the receiver's took 2.4 and now takes 0.5.
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M2 and M4 of design 011. Ten thousand devices send an order every five
seconds (2,000 a second); the receiver is killed (-9) at about 21 s and
started again at once. With its secrets remembered the node shows no
100 ms step without an order stored, catches up in 0.2 s, spends no more
CPU than before and makes no X25519; 34 orders were sent again, and
every order made was applied once (three rounds; on the SD card the
same, with 0.2 s silent). Without the memo it makes 10,000 X25519, 1.6 s
of CPU. quinn under the same load stops for 1.0 s and catches up after
10.9 s: 10,115 new connections, about 7 s more of the service's CPU and
8 s of the clients'. A first contact takes Pure one round trip and QUIC
two, at 10, 50 and 100 ms of RTT.
run.py --restart and --first-contact make them; the quinn harness gains
a fixed port with a reset key from its key, clients that connect again,
and a drain for M5.
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A listener lets a quiet sender's secret go with its active state, so a
node started again made one X25519 for every sender that came back (169
us on this Pi, most of a wake's CPU): asymmetric work in proportion to the
links, which design 011 counts as a reason to design again. The secret is
now remembered in a file beside the key (KEY.links, 0600, begun again for
another node's key): a place of 64 bytes a sender in the order allowed,
mapped, so a sender at rest takes no memory for it. A place is the first
28 bytes of the sender's key, a check (FNV-1a of the key and the secret)
and the secret, written secret first and key last; a place whose check
fails is made again. The UDP link checks see a receiver started again
make no X25519.
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M1 of design 011. A Pure node allows 1,000 to 1,000,000 senders; each
sends one order and, once told it is stored, rests. At rest a link costs
the node 132 bytes (the sender allowed, 73; its number heard, about 60)
and no transport state; with a million the node runs in 139 MB. A quinn
0.11 service holding the same exchange's clients connected at rest costs
38,106 bytes a connection: 289 times as much, past the design's 1/100.
A link at rest takes its next record in 0.56 ms to stored, one X25519 on
the node included; a new QUIC connection takes 1.06 ms and 2.8 times the
receiver's CPU, without storing.
research/experiments/019-idle-links: links.c, many senders written from
serve/link.h's packet format alone (a second implementation), and the
quinn service and clients (quic/, built offline); run.py makes both
measurements.
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Each run a listener knew held two OpenSSL contexts. With 16 KiB pages,
what those allocations left behind when idle senders went kept 42 MB of
free heap resident after 10,000 senders had come and gone (in use: 0.6
MB). A run now keeps its keys (16 bytes each way and the nonce bases),
and the listener seals and opens with one context, giving it each
packet's key: about 130 ns a packet on this Pi. Two runs a sender, not
four; a sender's address as an IPv6 one (an IPv4 one fits). What idle
senders held goes back to the system once 1,024 have gone, or 10 s after
any went (malloc_trim). HKDF is fetched once, not at every derivation.
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A sender allowed is now a peer of 48 bytes (its key, its key's id, its
sources), found through an index by key id; ids are 32 bits, so keys that
share one are each tried. What a sending peer needs besides (the secret
its key shares with the node's, its runs' keys and addresses, its
streams) is made at its first packet and let go once it has been quiet
for the idle period (--link-idle-ms, 30 s at first) with nothing of it
waiting: the next packet makes it again, one X25519, no handshake. The
listener hands over and answers only the streams and runs that changed,
not every one at each turn. --senders FILE allows senders a line each.
The UDP link checks take their sender from such a file among a thousand
others, let it go after 400 ms of quiet, and see an order after a longer
pause arrive all the same.
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The last number heard from each source was written whole into the links
value at every save, and counted in two bytes: a node that heard from
more than 65,535 sources stored a wrong count, and each save cost as many
bytes as there were sources. The numbers are now a runtime-owned list
{source, seq} in order of source, stored as a list state is (its image
"0heard" and its changes in the log), changed with the event that
delivers, so a failed save takes them back with it. Links stored before
(PLK1) move their numbers to the list at a start and are stored again
without them (PLK2).
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pure-serve --send OUTPUT=pure://host:port/INPUT sends an output's saved
sends to another node's --link-port with no handshake: the first packet
carries records. Keys come from the two nodes' keys (X25519, HKDF-SHA256,
AES-128-GCM), with a random run in each packet's header so no nonce
repeats across restarts; nothing is stored for them. What lasts is the
apps' own: the sender's outbox and the receiver's heard numbers
(pure_app_heard, new). The sender detects losses as RFC 9002 says, with
NewReno, and trims a send once the receiver says it stored it; the
receiver hands the owner whole records in order, which it applies from
the one after the source's last heard number, stopping at a gap, and
answers how far it stored with every acknowledgment. Stored bytes are
the bytes on the wire: an output and an input of one shape need no JSON.
server_links_udp kills the receiver, the sender, then both (-9) while
four clients buy: every saved order is applied once, with no handshake
(five runs, 10k-11k orders each). server_links_udp_lossy does it again in
a namespace of its own with the link's packets delayed, lost (3 %) and
reordered (10 %) by netem (three runs, 11k-12k orders).
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The first draft replaced a few of QUIC's layers with what Pure already
has, every technique known and the gains constant factors, and it kept
the connection. This one removes it. Nodes have keys, links are the app's
wiring, paths are a cache of where the last authenticated packet came
from, and a link's transport state (key epoch, stored-through number,
heard numbers, packet-number reservation) is a row committed atomically
with the app's state; memory holds only active links and per-path
congestion state. So a restart of either node is invisible to the other
(no handshake, nothing lost or doubled), an idle link costs a row on
disk rather than process memory, and moving the store moves its links.
Forward secrecy comes from key epochs rather than per-connection
handshakes; replay protection survives restarts because heard numbers
are stored with the events they applied (OSCORE, the closest prior art,
needs an Echo round trip there).
Hypotheses H1-H4 and a measurement plan against quinn and ngtcp2:
memory per idle link at 10k to 1M links, kill -9 under load with 10k
active links, moving the store, first contact, and CPU, loss and fairness
as guardrails; stop if an idle link is not at least a hundred times
cheaper than a QUIC connection, if restarts need handshakes, or if
anything is lost or doubled. Beyond it: speculative execution of
verified, deterministic modules, for interactions that do not wait.
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Outside feedback 002 asks for a protocol of Pure's own that beats QUIC.
Pure's delivery is already stored, numbered, applied once, and sealed per
link; QUIC and TCP with TLS own the same things again (retransmission
buffers, replay protection, encryption, flow control, acknowledgment).
The design takes the end-to-end argument literally: the sending app's
store is the retransmission buffer, one packet carries both the packet
ACK and the stored-through number, a direct link is sealed once with the
nodes' session keys, first contact carries records in its first packet
(the receiver's key is wired in advance and applying once makes replays
harmless), credits come from what the next save can take, the session is
known by its key rather than its addresses, and stored bytes are the
bytes on the wire. Loss detection, congestion control and cryptography
stay standard (RFC 9002, NewReno then CUBIC, HPKE), plain UDP sockets
rather than SOCK_RAW, HTTP stays the boundary to others.
Written before any code: the decision (this transport, QUIC with Pure's
format, or neither), the open questions, the smallest checks, a
measurement plan against quinn, ngtcp2 and the current HTTP delivery
(seven workloads, RAM and SD stores, loss and delay from unprivileged
namespaces with netem, checked to work on this Pi), and stop criteria:
no transport if it is under 30 % of a delivery's CPU; stop below 1.5x
the best QUIC per CPU; adopt at 2x with a round trip fewer, a quarter of
the memory per idle link, fair to TCP, every correctness and security
check passing, and under 5,000 lines.
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and an SD card
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store
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