PC - AOR GT3 S11 - PC Tier 3 - ROUND 2 - Silverstone GP | ApexOnlineRacing.com

PC AOR GT3 S11 - PC Tier 3 - ROUND 2 - Silverstone GP

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Deerladog

Assetto Corsa Coordinator
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AC Coordinator
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AOR Commentator
Aug 24, 2017
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@krop I have a 6700k that I've pushed almost to 5GHz from 4GHz stock, and I still believe I'm suffering from grip loss as a result of my CPU being unable to handle all the physics calculations etc for all the cars on track in a full AOR grid. Over the past season or so I've just learnt to expect to not be able to achieve within 1s of my practice times when it comes to race day.
 

Ranno

AOR PCars PC Ginetta GT5 S1 T2 Champion
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Feb 28, 2018
2,213
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@krop I have a 6700k that I've pushed almost to 5GHz from 4GHz stock, and I still believe I'm suffering from grip loss as a result of my CPU being unable to handle all the physics calculations etc for all the cars on track in a full AOR grid. Over the past season or so I've just learnt to expect to not be able to achieve within 1s of my practice times when it comes to race day.
Krop is not using VR. I started having problems when I switched to VR.
It may actually run OK on a single monitor with 4690k. But what I remember from the CPU benchmarks I posted in Discord, I find it hard to believe it runs 120fps on 4690k
 

Deerladog

Assetto Corsa Coordinator
Staff member
AC Coordinator
Premium Member
AOR Commentator
Aug 24, 2017
778
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I also had the same issue when running on a single monitor last season, so I doubt that Krop is faring much better.
 

venquessa

Formula 4 2nd Driver
Sep 16, 2018
123
66
So putting my Software Engineer hat on, there is no way PCars lobbies are P2P. It's not possible without everyone opening inbound ports, which I'm sure none of you have. You simply cannot receive peer to peer connections from a random (from your routers point of view) computer... without opening firewall ports.

So what they call P2P must go via n intermediary.

I believe what they call P2P is just that someone hosts the game session and everyone connects via a proxy or other connection router. So everyone makes connects to it, it forwards them down other people's connections.

The primary difference is there is a certain hub/proxy/router/intermediary, so everyone has two hops. Netcode performance depends on your connection, and the other parties' connection to that intermediary.
 

venquessa

Formula 4 2nd Driver
Sep 16, 2018
123
66
I had no issues in any of the races this week. Only at Algarve, but I'm not convinved that was network or host issues, I think it was Windows update still messing around, or running a Windows defender scan or some ****.
 

Ranno

AOR PCars PC Ginetta GT5 S1 T2 Champion
Staff member
iRacing Coordinator
Feb 28, 2018
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So putting my Software Engineer hat on, there is no way PCars lobbies are P2P. It's not possible without everyone opening inbound ports, which I'm sure none of you have. You simply cannot receive peer to peer connections from a random (from your routers point of view) computer... without opening firewall ports.

So what they call P2P must go via n intermediary.

I believe what they call P2P is just that someone hosts the game session and everyone connects via a proxy or other connection router. So everyone makes connects to it, it forwards them down other people's connections.

The primary difference is there is a certain hub/proxy/router/intermediary, so everyone has two hops. Netcode performance depends on your connection, and the other parties' connection to that intermediary.
I'm no software engineer, but I'm quite sure PCars is P2P. Also a lot of other things are P2P without the need to open ports manually. So You are saying all of them have a intermediary? Whats so P2P about them then?

From what I see, I'm sure that the host is not between every packet sent (that would show in reported ping). I highly doubt SMS is hosting this intermediary for everyone. So who is this intermediary? And are You saying every packet sent has to go though it or only the first, to establish the direct connection?
 

venquessa

Formula 4 2nd Driver
Sep 16, 2018
123
66
So 99.9% of us have an internet router. This will be 99.9% of the time a NAT router. A private IP address range on the inside, a single IP on the outside. Should I wish to connect to your game and I send a request to your IP, where would your router send it? Your PC? Your Phone? Your laptop upstairs? How would it know? NAT routing is incredible common and also a highly effective firewall as a result.

When you establish a connection to a host, the host must have an open route to a server which is "listening" on that port. It must recieve your package and accept it. The reason you can receive the reply is because YOU sent the request. A NAT router tracks connections. By default it; accepts all related and established traffic, only if it has a previous connection in it's list.

Ping times do not tell you anything about how many hops there are. If you consider that on the way to your ISP, out onto the backbone, down to the other ends ISP and through their network to a host, you packet might take 20 hops to ping bbc.co.uk

There do exist UPNP routers which applications can interface with and ask it to open an inbound port and direct it to a particular IP, but nobody in their right mind ever actually turns that on. I definitely don't.

I could always run wireshark and capture some lobby traffic, or google it, because someone has bound to have done this.

There is some clever distributed stuff going on in P2P, the way the lobby can change hosts etc. But I don't see how it can be direct connection P2P.
 

Ranno

AOR PCars PC Ginetta GT5 S1 T2 Champion
Staff member
iRacing Coordinator
Feb 28, 2018
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I somewhat know how networks work, at least I think I do. But I'm too tired at the moment to argue about it.

I believe there can be some central server that helps establish the P2P connections or this is done by the host PC. But I have a hard time believing that every packet is sent though it, I just don't see evidence for that. Everything is pointing to that it's P2P. I think also the developer of PCars has confirmed it using P2P connections (at least thats what I have read on various forums).
 

venquessa

Formula 4 2nd Driver
Sep 16, 2018
123
66
Okay. There might be a way. If the central server gets each player to send a UDP packet to every other player, this will register outbound association on those routers. They will be in the "related" list. When a player wants to send data to another player they can as it will match the "related" association created by the outbound packet on the receiver.

I had forgotten about UDP. It doesn't do "connections", it does streams and there is no need for an association to be negotiated. If you send a UDP packet to an IP you will accept and UDP packet coming back as a reply.

EDIT:
Wireshark confirms this. Apparently it uses (what wireshark identifies as) "CLASSIC STUN" protocol to establish the two way communications. Every client sends a request to each other. These will "cross on the wire", so as long as you have sent your binding request before you receive the other guys his will be routed to your PCars as your router is expecting a reply. This "handshake" is repeated periodically, like every few seconds.

Most packets are 25 or 79 bytes payload (68 or 121 total packet size), with a few larger 600 byte packets occasionally. On the connection I'm looking at, one "peer" is sending me a packet every 50ms or so. Bind request, responses sent every second or so. I am sending similar to him.

So for each "peer" that's, say 150 bytes per packet, 20 packets per second, 3000 bytes per second. 24 kbit bandwidth.. Ballpark. 30 peers, 720kbit/s bidirectional. That's interesting, as my outbound connection would be at saturation at twice that rate.

https://en.wikipedia.org/wiki/STUN
 
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