[dpdk-users] Is it possible to TX through a port with no RX connected?

[dpdk-users] Is it possible to TX through a port with no RX connected?

[Andrea Bigagli]

Hi everyone.
Moving first steps with DPDK, so forgive my noobness or if this is a dumb question, but I’ve searched around before posting and didn’t find anything that could help me.

I have 4 Intel 10Gbps cards for a total of 8 RX/TX ports.
What I’m trying to do is a kind of “8->4 tapping-concentrator”: 8 fibers are tapped through an optical splitter and connected to the 8 RX ports, some packet analysis is performed and based on certain properties of the packets, traffic is re-routed on only 4 TX ports.
The application guarantees that overall input bandwidth is less than 30Gbps, so using only 4 TXs is not a problem (the balancing is almost pretty even).
The problem I’m facing is that the 8 monitored RX are not always up. The system being monitored at times shuts down some of those 8 connections and so on some of the 8 RXs the link goes down, and when that happens, the corresponding TX stops working.
I’m not a great expert of the inner working of the 10Gbps cards, I’ve skimmed through the 82599 datasheet and tried to play with some registers (i.e. setting the “FORCE-LINK-UP” bit in the AUTOC register), but couldn’t find a way to keep the TX ports running without something “alive” on the corresponding RX port.

Is there any way (maybe diving down at the PHY layer, which I’m really not familiar with) to have TX ports working regardless of their corresponding RX port status?
Looping back something in the RX port is not feasible in my case because the RX port has to be dedicated to the tapped traffic, for when there’s actually traffic on it.

Hope I was able to explain myself, and hope someone could point me in some direction as I’m totally stuck at the moment.


Thanks,
Andrea.

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Muhammad Zain-ul-Abideen]

Hi there,

1) Without having a link UP, one cannot send packet, (Link is up when RX is
up)
2) I prefer, you use a by pass switch of some type, as i understand they
might b active taps, it will keep the link up, u can configure it to use
loop back the link if the tapped link goes down.

I hope, it might help you have a more clear view

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Andrea Bigagli]

Damn! I hoped there was a way to force the desired behavior in some way. 
I’m afraid adding a bypass switch is not an option at the moment as the “how” I get the tapped traffic is not directly under my control.

Thanks anyway.

> On 13 giu 2016, at 06:36, Muhammad Zain-ul-Abideen <zain2294@gmail.com> wrote:
> 
> Hi there,
> 
> 1) Without having a link UP, one cannot send packet, (Link is up when RX is up)
> 2) I prefer, you use a by pass switch of some type, as i understand they might b active taps, it will keep the link up, u can configure it to use loop back the link if the tapped link goes down.
> 
> I hope, it might help you have a more clear view
> 

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Muhammad Zain-ul-Abideen]

How many interface u got, if u got spare, u can work around

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Andrea Bigagli]

Nope.
I've got 4 dual port boards, and have to handle 8 RX. But I'm curious as
what the workaround would be?


On 14 giu 2016, at 23:39, Muhammad Zain-ul-Abideen <zain2294@gmail.com>
wrote:

How many interface u got, if u got spare, u can work around

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Pavey, Nicholas]

Hi Andrea,

Would it be possible to pass the incoming (tapped) traffic through a switch?

Perhaps that might allow the interfaces between the system being tapped and the switch to go down, while leaving the interfaces between the switch and the DPDK machine up? The switch would deal with the intermittent link-down conditions, without taking down the links to the DPDK and therefore not taking down your DPDK TX links too.

I know it’s extra cost, but perhaps it would allow you to make progress.

Regards,


Nick




From: Andrea Bigagli <andrea.bigagli@commprove.com>
Date: Tuesday, June 14, 2016 at 5:43 PM
To: Muhammad Zain-ul-Abideen <zain2294@gmail.com>
Cc: "users@dpdk.org" <users@dpdk.org>
Subject: Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

Nope.
I've got 4 dual port boards, and have to handle 8 RX. But I'm curious as
what the workaround would be?


On 14 giu 2016, at 23:39, Muhammad Zain-ul-Abideen <zain2294@gmail.com<mailto:zain2294@gmail.com>>
wrote:

How many interface u got, if u got spare, u can work around

Re: [dpdk-users] Is it possible to TX through a port with no RX connected?

[Andrea Bigagli]

I'm currently evaluating this possibility as it appears there's no
dpdk-only-based solution.

Unfortunately the budget is really tight and the customer is really against
adding any extra piece of metal in its premises, even if it's on the
monitoring path...

Thanks anyway for the suggestion


Il giorno 15 giu 2016, alle ore 14:56, Pavey, Nicholas <npavey@akamai.com>
ha scritto:

Hi Andrea,



Would it be possible to pass the incoming (tapped) traffic through a switch?



Perhaps that might allow the interfaces between the system being tapped and
the switch to go down, while leaving the interfaces between the switch and
the DPDK machine up? The switch would deal with the intermittent link-down
conditions, without taking down the links to the DPDK and therefore not
taking down your DPDK TX links too.



I know it’s extra cost, but perhaps it would allow you to make progress.



Regards,





Nick









*From: *Andrea Bigagli <andrea.bigagli@commprove.com>
*Date: *Tuesday, June 14, 2016 at 5:43 PM
*To: *Muhammad Zain-ul-Abideen <zain2294@gmail.com>
*Cc: *"users@dpdk.org" <users@dpdk.org>
*Subject: *Re: [dpdk-users] Is it possible to TX through a port with no RX
connected?



Nope.

I've got 4 dual port boards, and have to handle 8 RX. But I'm curious as

what the workaround would be?





On 14 giu 2016, at 23:39, Muhammad Zain-ul-Abideen <zain2294@gmail.com>

wrote:



How many interface u got, if u got spare, u can work around