1.2. TAS Command-Line Parameters¶

1.2.1. IP Configuration¶

--ip-addr=ADDR[/PREFIXLEN]

Set local IP address. Currently only exactly one IP address is supported.

--ip-route=DEST[/PREFIX],NEXTHOP

Add an IP route for the destination subnet DEST/PREFIX via NEXTHOP. Can be specified more than once. For example, a default route could be --ip-route=0.0.0.0/0,192.168.1.1.

1.2.2. Fast Path Configuration¶

--fp-cores-max=CORES

Maximum number of cores to use for fast-path. (default: 1)

--fp-no-ints

Disable receive interrupts in the NIC driver, switches over to just polling.

--fp-no-xsumoffload

Disable transmit checksum offloads, primarily useful to run TAS with NICs that do not support checksum offload, but comes at a slight performance cost.

--fp-no-autoscale

Disable auto scaling, instead fix the number of cores used by the fast path to the maximum.

--fp-no-hugepages

Do not use huge pages for the shared memory region between TAS and applications. (DPDK still uses huge pages for it’s buffers unless explicitly disabled through --dpdk-extra)

--dpdk-extra=ARG

Pass ARG through as a parameter to the dpdk EAL. (see https://doc.dpdk.org/guides/linux_gsg/linux_eal_parameters.html)

1.2.3. TCP Protocol Parameters¶

--tcp-rtt-init=RTT

Initial RTT used for congestion control. Is updated with actual measurements when they arrive.

--tcp-link-bw=BANDWIDH

Link bandwidth in GBPS. TODO: what is this used for? (default: 10).

--tcp-rxbuf-len=LEN

Connection receive buffer len in bytes (default: 8,192).

--tcp-txbuf-len=LEN

Connection transmit buffer len in bytes (default: 8,192).

--tcp-handshake-timeout=TIMEOUT

TCP handshake timeout in microseconds (default 10,000us).

--tcp-handshake-retries=RETRIES

Maximum retries for timeouts during handshake. (default: 10).

1.2.4. Congestion Control Parameters¶

--cc=ALGORITHM

Choose which congestion control algorithm to use. The supported options are:

dctcp-rate: dctcp algorithm adapted to directly operate on the connection rate.

dctcp-win: original dctcp algorithm with the window converted to a rate for enforcement.

timely: latency-based TIMELY control law.

const-rate: set all connections to a constant rate (effectively disables congestion control, useful for debugging).

--cc-control-interval=INT

Control interval length as multiples of the connection’s RTT. (default: 2)

--cc-control-granularity=G

Minimal control loop granularity. Control loop is only executed at most once every G microseconds. (default: 50)

--cc-rexmit-ints=INTERVALS

Number of connection cnotrol intervals before TAS triggers a re-transmit. (default: 4).

1.2.4.1. DCTCP¶

For the dctcp-rate and dctcp-win algorithm:

--cc-dctcp-weight=WEIGHT

EWMA weight for dctcp’s ECN rate (alpha, default: 0.0625).

--cc-dctcp-mimd=INC_FACT

Enable mutliplicative increase by INC_FACT (disabled by default, only used for tests).

--cc-dctcp-min=RATE

Minimum rate to set for flows (kbps, default: 10000).

1.2.4.2. Timely¶

Parameters for the timely algorithm:

--cc-timely-tlow=TIME

Tlow threshold in microseconds. (default: 30)

--cc-timely-thigh=TIME

Thigh threshold in microseconds. (default: 150)

--cc-timely-step=STEP

Additive increase step size in kbps (default: 10000)

--cc-timely-init=RATE

Initial connection rate in kbps (default: 10000)

--cc-timely-alpha=FRAC

EWMA weight for rtt diff. (default: 0.02)

--cc-timely-beta=FRAC

Multiplicative decrease factor. (default: 0.8)

--cc-timely-minrtt=RTT

Minimal RTT without queueing in microseconds. (default: 11)

--cc-timely-minrate=RTT

Minimal connection rate to use in kbps (default: 10000)

1.2.4.3. Constant Rate¶

For the const-rate “algorithm” the following configuration options apply:

--cc-const-rate=RATE

Sets the rate to use in kbps.

1.2.5. ARP Protocol Parameters¶

--arp-timeout=TIMEOUT

Initial ARP request timetout in microseconds. This doubles with every retry (default: 500).

--arp-timeout-max=TIMEOUT

Maximal ARP timeout in microseconds. If the retry-timeout grows larger than this, the request fails. (default: 10,000,000 us)

1.2.6. Slowpath Queues¶

--nic-rx-len=LEN

Number of entries in TAS slowpath receive queue. (default: 16,384).

--nic-tx-len=LEN

Number of entries in TAS slowpath transmit queue. (default: 16,384).

--app-kin-len=LEN

Application slow path receive queue length in bytes. (default: 1,048,576).

--app-kout-len=LEN

Application slow path transmit queue length in bytes. (default: 1,048,576).

1.2.7. Host Kernel Interface¶

--kni-name=NAME

Enables the DPDK kernel network interface, by creating a dummy network interface with the name NAME. (default: disabled)

1.2.8. Miscellaneous¶

--quiet

Disable non-essential logging.

--ready-fd=FD

Causes TAS to write to file descriptor FD when ready. Can be used by supervisor processes to detect when TAS is ready, e.g. used in full system tests.