Below is the Ionic information while writing this tutorial.

Cordova CLI: 6.5.0 
Ionic Framework Version: 3.0.1
Ionic CLI Version: 2.2.1
Ionic App Lib Version: 2.2.0
Ionic App Scripts Version: 1.3.0
ios-deploy version: Not installed
ios-sim version: 5.0.13 
OS: macOS Sierra
Node Version: v6.10.0
Xcode version: Xcode 8.2.1

Recently I tried to implement the Ajax service on the Ionic 2 application. I faced two problems when I tried to use the Http class from @angular/http.

1. No provider for Http
2. No provider for "connection backend"

If you face the above error while using the @angular/Http class, you have to include the HttpModule in the imports of the app.module.ts file.

Open the app.module.ts file  and import the HttpModule

import { HttpModule } from '@angular/http';

Now include the HttpModule on the imports

imports: [

That's all. The No provider for Http and No provider for "connection backend" is solved. 

Angular 2 No provider for Http.
angular2 No provider for "connection backend".