ajax fail recursive pure javascript

function a(d, p, s, r, n) {
//d -> json
//p -> object with XHR
//s -> url link for current ajax call
//r -> object with all links for ajax calls
//n -> counter variable to limit ajax calls in case of all 3 servers
// fail to connect 
    if (n > 3) {
        return;
    } else {
        try {
            var x = w(p, s); // function to create cross domain XHR
            x.setRequestHeader("Content-Type","application/json;charset=UTF-8", 'X-Requested-With', 'XMLHttpRequest');
            x.onreadystatechange = function() {
                if (x.readyState != 4) {
                    return;
                }
                if(x.status==200){
                    console.log("success: ", d);
                }
                if (x.status != 200) {
                    console.log("t2", d, "N: ", n);
                    try {
                        f(d); // throw error with data json
                    } catch (e) {
                        a(e.message, p, r.t1, r, n);
                    }
                    try {
                        e(p, s, r); // throw error with error json
                    } catch (e) {
                        a(e.message, p, r.err, r, n);
                    }
                }
            };
            x.send(d);
            n++;
        } catch (e) {
            console.log(e.message);
        }
    }
};

I try to make two async ajax calls inside ajax call to my own servers, in case of outer ajax call did not succeed. I get result, that only last ajax call is really goes out of browser to the server. I can't use callback, as I only need this two ajax calls in case first one fail.

The main trick - I can't use jQuery, and this ajax should be cross-browser compatible -> IE8,9. I already test it on my servers, and it work with cross domain. the only thing is breaking my mind, how to make this code to run 2 ajax calls on fail of first one. I do not need COMET( subscribe) or WebSockets.

Please help me somebody.