Linksys WRT 1900ACS v2 installation

Greetings!!
We are trying to install LEDE/OpenWRT in Linksys WRT1900ACSv2. We found the installation URL from the hardware list (https://openwrt.org/toh/views/toh_fwdownload?dataflt[Model*~]=wrt1900acs&dataflt[Brand*~]=linksys). However the page only shows one option for 1900ACS while for 1900AC it shows separate links for v1 and v2.
Is there only one common image for both version 1 and version 2 of WRT1900ACS ?

Thank You

They both (v1 or v2), for acs, use the same image.

1 Like

I've updated this as well under Firmware Images in the WRT AC Series ToH

1 Like

Thank You !

Thank you!

Hello David, Greetings.

I work with Abin, who had asked the earlier question. Thanks. We flashed the Linksys rotuer with the firmware. The basic functionality i.e., enabling bring up with OVS, and enabling switching using OpenvSwitch works fine. However we have challenges.

Our (abin & myself) goal is to use OVS support over the LAN ports of Linksys Wrt 1900ACS v2, and create a high speed OVS enabled switch. We observe high latency when OVS is enabled. i.e., a ping between two end systems with the OVS enabled results in a round trip delay of about 400+micro seconds (0.4+ ms). Without OVS, the base switching silicon gives a round trip delay of about 180+micro seconds (0.18+ms). Our expectation was OVS to be give as close to basic switching silicon speed. Do you have any pointer/suggestion which can reduce the latency. or in other words how to increse ovs kernel forwarding speed?

Also we observed the ring buffers rx 128 and tx as 532. Any pointers as how to increase the rx buffers? we thought Linksys 1900ACS being a powerful device will have large ring buffers, but got plesantly surprised.

thank you
Manikantan

Hello, Greetings.

I work with Abin, who had asked the earlier question. Thanks. We flashed the Linksys rotuer with the firmware. The basic functionality i.e., enabling bring up with OVS, and enabling switching using OpenvSwitch works fine. However we have challenges.

Our (abin & myself) goal is to use OVS support over the LAN ports of Linksys Wrt 1900ACS v2, and create a high speed OVS enabled switch. We observe high latency when OVS is enabled. i.e., a ping between two end systems with the OVS enabled results in a round trip delay of about 400+micro seconds (0.4+ ms). Without OVS, the base switching silicon gives a round trip delay of about 180+micro seconds (0.18+ms). Our expectation was OVS to be give as close to basic switching silicon speed. Do you have any pointer/suggestion which can reduce the latency. or in other words how to increse ovs kernel forwarding speed?

Also we observed the ring buffers rx 128 and tx as 532. Any pointers as how to increase the rx buffers? we thought Linksys 1900ACS being a powerful device will have large ring buffers, but got plesantly surprised.

thank you
Manikantan

You don't have to post the same replies to multiple people, just mention the user(s) via @< username > (i.e. @manikantan @abinmathew2) and the user will be notified they've been mentioned in a post =]

I have no experience with OVS, but 400ms does seem quite excessive. If you haven't already done so, I would utilize forum search until someone more knowledgeable is able to reply.

That's not 400ms, that 0.4ms which is less than 1ms.

thank you for the pointers.. will dig further the forum post, and wait for reply.

As @davidc502 metioned, the round trip time is now 0.4 ms, which ideally must be less than or equal to 0.2ms or less. TP-Link 1043ND gives 0.2ms. We need to figure out if there is a way to reduce it.

Also our application generates burst of data. May be a large tx/rx ring buffer size is required. We have to figure out the possibility for increasing this.

Thanks for your support. Thank you @davidc502

Sorry, I can't be of more help as this is in an area I'm unfamiliar with.

The old forum was horrible with searches, and with a shell of the forum being stood up in its place now, I'm not going to find what I'm looking for. However, I have heard of people attempting to tweak buffer sizes, but have no idea how it was done.

EDIT

The first place I looked was sysctl.conf. However, I don't see the usual options to adjust wmem max.

Thank you @davidc502 for your time and replies. Much appreciated.

Will continue looking out for a suitable solution.
Wishing you a good weekend.
Regards
Manikantan

Out of curiosity, why does the extra 200μs matter?

Thank you for asking the question @JW0914

Now the measured .4 ms round-trip (ping) latency indicates (assuming symmetric network behavior) a one-way latency of .2 ms. This is with Host 1<--> Linksys WRT1900 ACS <---> Host 2. A back to back Host1<---> Host2 round-trip ping latency is about 0.1ms, one way will be .05ms. This leads to conclude the latency overhead added by one hop (Linksys WRT1900 ACS ) is 0.15 ms.

In my setup, i am looking forward to a network with 4 hops, such as Host1 <-> S1<->S2<->S3<->S4<->H2. Now 4 switches in between each adding .15 ms will add to a total of .6ms latency.

My application (a mobile LTE network testbed) expects data transfers and response back within certain time limits such as 3 ms. Hence as much reduced latency will help.

I do agree, slightly higher latency might not be a serious deterrent for my setup, but packet drops cause issues. If forwarding is faster, less latency, imply less buffer overrun, and thus no packet drops.

We burst 14 packets every 1 ms, 14 packets (89,600 bits) get generated within a short span say within 15 microseconds, the rate is about 500 Mbps (for this 15-microsecond duration). Buffer size to handle the burst is critical for me. Hence looking for pointers that could help to increase on TX/RX ring buffers/buffer sizes, i.e. there is no loss in a network having 4 hops.

thank you
Manikantan
@abinmathew2

1 Like