Revisiting WiFi Connection Speed (<200ms with static ip + bssid+ channel, 1.5-2 secs without static IP)

[kapyaar]

Board

ESP32 Dev Module

Device Description

ESP32 Dev Module

Hardware Configuration

Base Board with no peripherals.

Version

latest master (checkout manually)

IDE Name

Arduino IDE 2.3.4

Operating System

Windows 11

Flash frequency

80

PSRAM enabled

no

Upload speed

921600

Description

I am working on a battery powered application, hence connection speed to wifi is being tested. I have gone through 1675, but wanted to check if there has been any changes (for good or bad) in this context.
Is the almost 10x time disparity between static ip and dhcp expected?

Sketch

#include <WiFi.h>
const char *ssid = "wifi_ssid";          
const char *password = "wifi_password"; 

void setup() {
  Serial.begin(115200);
  Serial.print("Start Connect At ");
  Serial.println(millis());

  uint8_t bssid[6] = { 0xDE, 0xAD, 0xBE, 0xEF, 0x10, 0x3E };
  int32_t channel = 6;

  IPAddress local_IP(192, 168, 2, 61);
  IPAddress gateway(192, 168, 2, 1);
  IPAddress subnet(255, 255, 255, 0);
  IPAddress primaryDNS(8, 8, 8, 8);
  IPAddress secondaryDNS(8, 8, 4, 4);

  WiFi.config(local_IP, gateway, subnet, primaryDNS, secondaryDNS);  // Static IP connects in ~200mS. Without, Takes upto 2 seconds.
  WiFi.begin(ssid, password, channel, bssid, 1);

  //WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(10);
    Serial.print(".");
  }
  Serial.println("WiFi connected at ");
  Serial.println(millis());
}
void loop() {
  esp_sleep_enable_timer_wakeup(10 * 1000000);
  esp_deep_sleep_start();
}

Debug Message

Just the time difference in connection, under 

  while (WiFi.status() != WL_CONNECTED) {
    delay(10);
    Serial.print(".");
  }

No Error messages.

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[lbernstone]

There's a lot of variables in WiFi connection that are outside of the control of the ESP device. Looking at verbose logs will let you see some of them, but a full understanding of the transaction will require a wireshark. I can see on my esp32 logs that the WiFi negotiation only takes about 100ms. Then, on first connection, DHCP negotiation takes about 3.5sec. On a restart, where the lease can be reused, DHCP only takes 100ms. From this, I can conclude that most of the time is spent by the AP (which is the DHCPd) figuring out a valid address and committing it to memory, not in getting that info back to the esp32.

[kapyaar]

Got it, thanks! In my tests, the time difference seemed fairly consistent so I was curious whether any of the scan related parameter was at play.

[lbernstone]

scan related parameters? I don't see any scanning in your code. I ran the simplest connection code possible with verbose logging

#include <WiFi.h>
void setup() {
  Serial.begin(115200);
  WiFi.begin("ssid","pass");
  WiFi.waitForConnectResult();
}
void loop() {delay(-1);}

I get this in the logs:

15:14:05.859 -> [   681][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 112 - STA_CONNECTED
15:14:05.859 -> [   689][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 112 - STA_CONNECTED
15:14:05.892 -> [   705][V][NetworkInterface.cpp:78] _onIpEvent(): sta Got New IP: 192.168.2.240 MASK: 255.255.255.0 GW: 192.168.2.1
15:14:05.892 -> [   716][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 115 - STA_GOT_IP
15:14:05.892 -> [   724][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 115 - STA_GOT_IP
15:14:05.892 -> [   731][V][STA.cpp:171] _onStaArduinoEvent(): STA IP: 192.168.2.240, MASK: 255.255.255.0, GW: 192.168.2.1

That gap between STA_CONNECTED and the finish of GOT_IP is the DHCP transaction. Any extra code other than that simple begin is unnecessary (well, some error checking is good). If you aren't allowing the device to save the wifi connection information (which includes the lease info), then that will slow your connection down.

[kapyaar]

By scan, I meant channel scan before connecting.

I ran verbose with and without static IP, and I see what you mean.

Connecting to wifi_ssid (with static settings)

[   883][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 101 - WIFI_READY
[  1003][V][STA.cpp:186] _onStaEvent(): STA Started
[  1008][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 110 - STA_START
[  1016][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 110 - STA_START
..........
[  1132][V][STA.cpp:206] _onStaEvent(): STA Connected: SSID: wifi_ssid,  Channel: 6, Auth: WPA2_PSK
[  1144][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 112 - STA_CONNECTED
[  1144][V][NetworkInterface.cpp:78] _onIpEvent(): sta Got New IP: 192.168.2.61 MASK: 255.255.255.0 GW: 192.168.2.1
[  1162][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 112 - STA_CONNECTED
[  1170][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 115 - STA_GOT_IP
[  1178][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 115 - STA_GOT_IP
[  1185][V][STA.cpp:171] _onStaArduinoEvent(): STA IP: 192.168.2.61, MASK: 255.255.255.0, GW: 192.168.2.1
.
WiFi connected

Connecting to wifi_ssid (dhcp) with WiFi.persistent(true);

[   884][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 101 - WIFI_READY
[  1000][V][STA.cpp:186] _onStaEvent(): STA Started
[  1005][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 110 - STA_START
[  1013][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 110 - STA_START
.......
[  1104][V][STA.cpp:206] _onStaEvent(): STA Connected: SSID: wifi_ssid,  Channel: 6, Auth: WPA2_PSK
..
[  1116][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 112 - STA_CONNECTED
[  1124][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 112 - STA_CONNECTED
.........................................................................................................
[  2180][V][NetworkInterface.cpp:78] _onIpEvent(): sta Got New IP: 192.168.2.61 MASK: 255.255.255.0 GW: 192.168.2.1
.
[  2191][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 115 - STA_GOT_IP
[  2199][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 115 - STA_GOT_IP
[  2206][V][STA.cpp:171] _onStaArduinoEvent(): STA IP: 192.168.2.61, MASK: 255.255.255.0, GW: 192.168.2.1
.
WiFi connected

I would have thought that after the first dhcp connect, subsequent connections would be faster with persistent(true), but timing remains the same over repeated sleep/wake/connects.

WiFi.begin(ssid, password, channel, bssid, 1); Seems to be performing about 800ms faster than WiFi.begin(ssid, password);

Connecting with WiFi.begin(ssid, password);

[   884][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 101 - WIFI_READY
[  1000][V][STA.cpp:186] _onStaEvent(): STA Started
[  1005][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 110 - STA_START
[  1013][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 110 - STA_START
E (2449) wifi:sta is connecting, return error
[  1179][E][STA.cpp:417] connect(): STA connect failed! 0x3007: ESP_ERR_WIFI_CONN
..................................................................
[  1854][V][STA.cpp:206] _onStaEvent(): STA Connected: SSID: wifi_ssid, Channel: 6, Auth: WPA2_PSK
.
[  1867][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 112 - STA_CONNECTED
[  1875][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 112 - STA_CONNECTED
.......................................................................................................
[  2909][V][NetworkInterface.cpp:78] _onIpEvent(): sta Got New IP: 192.168.2.61 MASK: 255.255.255.0 GW: 192.168.2.1
.
[  2920][V][NetworkEvents.cpp:117] _checkForEvent(): Network Event: 115 - STA_GOT_IP
[  2928][V][STA.cpp:110] _onStaArduinoEvent(): Arduino STA Event: 115 - STA_GOT_IP
[  2935][V][STA.cpp:171] _onStaArduinoEvent(): STA IP: 192.168.2.61, MASK: 255.255.255.0, GW: 192.168.2.1
.
WiFi connected

Not sure what those error mean, but it does connect.

[lbernstone]

You would need to wireshark (or have logs on the DHCPd) to see exactly what is going on in the dhcp negotiation. But, it seems like the slowdown is not on the esp32.

[kapyaar]

I did a quick wireshark capture with WiFi.begin(ssid,pwd) and sleep for 10sec. I see something like this.

And they look like this.

215	33.877358	Espressif_4f:90:e4	Broadcast	XID	52	Basic Format; Type 1 LLC (Class I LLC); Window Size 0
Frame 215: 52 bytes on wire (416 bits), 52 bytes captured (416 bits) on interface en0, id 0
    Section number: 1
    Interface id: 0 (en0)
        Interface name: en0
        Interface description: Wi-Fi
    Encapsulation type: Ethernet (1)
    Arrival Time: Mar 19, 2025 14:12:24.773200000 EDT
    UTC Arrival Time: Mar 19, 2025 18:12:24.773200000 UTC
    Epoch Arrival Time: 1742407944.773200000
    [Time shift for this packet: 0.000000000 seconds]
    [Time delta from previous captured frame: 0.818851000 seconds]
    [Time delta from previous displayed frame: 0.818851000 seconds]
    [Time since reference or first frame: 33.877358000 seconds]
    Frame Number: 215
    Frame Length: 52 bytes (416 bits)
    Capture Length: 52 bytes (416 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:llc]
    [Coloring Rule Name: Broadcast]
    [Coloring Rule String: eth[0] & 1]
IEEE 802.3 Ethernet 
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: Espressif_4f:90:e4 (90:15:06:4f:90:e4)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Length: 38
    [Stream index: 3]
Logical-Link Control
    DSAP: NULL LSAP (0x00)
        0000 000. = SAP: NULL LSAP
        .... ...0 = IG Bit: Individual
    SSAP: NULL LSAP (0x01)
        0000 000. = SAP: NULL LSAP
        .... ...1 = CR Bit: Response
    Control field: U, func=XID (0xAF)
        101. 11.. = Response: Exchange identification (0x2b)
        .... ..11 = Frame type: Unnumbered frame (0x3)
Logical-Link Control Basic Format XID
    XID Format: LLC basic format (0x81)
    LLC Types/Classes: Type 1 LLC (Class I LLC) (0x01)
    Receive Window Size: 0



===
218	33.980969	Espressif_4f:90:e4	Broadcast	ARP	52	Who has 192.168.2.61? (ARP Probe)
Frame 218: 52 bytes on wire (416 bits), 52 bytes captured (416 bits) on interface en0, id 0
    Section number: 1
    Interface id: 0 (en0)
        Interface name: en0
        Interface description: Wi-Fi
    Encapsulation type: Ethernet (1)
    Arrival Time: Mar 19, 2025 14:12:24.876811000 EDT
    UTC Arrival Time: Mar 19, 2025 18:12:24.876811000 UTC
    Epoch Arrival Time: 1742407944.876811000
    [Time shift for this packet: 0.000000000 seconds]
    [Time delta from previous captured frame: 0.000289000 seconds]
    [Time delta from previous displayed frame: 0.000289000 seconds]
    [Time since reference or first frame: 33.980969000 seconds]
    Frame Number: 218
    Frame Length: 52 bytes (416 bits)
    Capture Length: 52 bytes (416 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:arp]
    [Coloring Rule Name: ARP]
    [Coloring Rule String: arp]
Ethernet II, Src: Espressif_4f:90:e4 (90:15:06:4f:90:e4), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: Espressif_4f:90:e4 (90:15:06:4f:90:e4)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: ARP (0x0806)
    [Stream index: 3]
    Trailer: 00000000000000000000
Address Resolution Protocol (ARP Probe)
    Hardware type: Ethernet (1)
    Protocol type: IPv4 (0x0800)
    Hardware size: 6
    Protocol size: 4
    Opcode: request (1)
    [Is probe: True]
    Sender MAC address: Espressif_4f:90:e4 (90:15:06:4f:90:e4)
    Sender IP address: 0.0.0.0
    Target MAC address: 00:00:00_00:00:00 (00:00:00:00:00:00)
    Target IP address: 192.168.2.61

I don't know what I am looking for, so could nt get much mileage out of it. :)
IMO,

1. No matter what we find, if what you stated holds (that esp has nothing to do with the delay in getting the dhcp ip), then, there is not much point in troubleshooting, and I will live with what various routers out there offer in terms of their dhcp behaviour.
2. On the other hand, if there is any use that may come out of looking deeper, I will be happy to look for specifics and report back.