Index: src/wp-includes/ms-settings.php
===================================================================
--- src/wp-includes/ms-settings.php	(revision 28898)
+++ src/wp-includes/ms-settings.php	(working copy)
@@ -10,12 +10,9 @@
  * @since 3.0.0
  */
 
-/** Include Multisite initialization functions */
-require( ABSPATH . WPINC . '/ms-load.php' );
-require( ABSPATH . WPINC . '/ms-default-constants.php' );
-
-if ( defined( 'SUNRISE' ) )
+if ( defined( 'SUNRISE' ) ) {
 	include_once( WP_CONTENT_DIR . '/sunrise.php' );
+}
 
 /** Check for and define SUBDOMAIN_INSTALL and the deprecated VHOST constant. */
 ms_subdomain_constants();
Index: src/wp-settings.php
===================================================================
--- src/wp-settings.php	(revision 28898)
+++ src/wp-settings.php	(working copy)
@@ -91,6 +91,9 @@
 // Initialize multisite if enabled.
 if ( is_multisite() ) {
 	require( ABSPATH . WPINC . '/ms-blogs.php' );
+	/** Include Multisite initialization functions */
+	require( ABSPATH . WPINC . '/ms-load.php' );
+	require( ABSPATH . WPINC . '/ms-default-constants.php' );
 	require( ABSPATH . WPINC . '/ms-settings.php' );
 } elseif ( ! defined( 'MULTISITE' ) ) {
 	define( 'MULTISITE', false );
Index: tests/phpunit/includes/bootstrap.php
===================================================================
--- tests/phpunit/includes/bootstrap.php	(revision 28898)
+++ tests/phpunit/includes/bootstrap.php	(working copy)
@@ -55,10 +55,6 @@
 	echo "Running as multisite..." . PHP_EOL;
 	define( 'MULTISITE', true );
 	define( 'SUBDOMAIN_INSTALL', false );
-	define( 'DOMAIN_CURRENT_SITE', WP_TESTS_DOMAIN );
-	define( 'PATH_CURRENT_SITE', '/' );
-	define( 'SITE_ID_CURRENT_SITE', 1 );
-	define( 'BLOG_ID_CURRENT_SITE', 1 );
 	$GLOBALS['base'] = '/';
 } else {
 	echo "Running as single site... To run multisite, use -c tests/phpunit/multisite.xml" . PHP_EOL;
Index: tests/phpunit/tests/ms.php
===================================================================
--- tests/phpunit/tests/ms.php	(revision 28898)
+++ tests/phpunit/tests/ms.php	(working copy)
@@ -455,7 +455,7 @@
 		$blog_id = $this->factory->blog->create( array( 'user_id' => $user_id, 'path' => '/test_blogname', 'title' => 'Test Title' ) );
 		$this->assertInternalType( 'int', $blog_id );
 
-		$this->assertEquals( 'http://' . DOMAIN_CURRENT_SITE . PATH_CURRENT_SITE . 'test_blogname/', get_blogaddress_by_name('test_blogname') );
+		$this->assertEquals( 'http://' . $current_site->domain . $current_site->path . 'test_blogname/', get_blogaddress_by_name('test_blogname') );
 
 		$this->assertEquals( $blog_id, get_id_from_blogname('test_blogname') );
 	}
@@ -1410,6 +1410,114 @@
 		$details = get_blog_details( get_current_blog_id() );
 		$this->assertEquals( 'bar', $details->blogname );
 	}
+
+	/**
+	 * @ticket 27884
+	 *
+	 * @expectedDeprecated define()
+	 */
+	function test_multisite_bootstrap() {
+		global $current_site, $current_blog;
+
+		$network_ids = array(
+			'wordpress.org/'         => array( 'domain' => 'wordpress.org', 'path' => '/' ),
+			'make.wordpress.org/'    => array( 'domain' => 'make.wordpress.org', 'path' => '/' ),
+		);
+
+		foreach ( $network_ids as &$id ) {
+			$id = $this->factory->network->create( $id );
+		}
+		unset( $id );
+
+		$ids = array(
+			'wordpress.org/'              => array( 'domain' => 'wordpress.org',      'path' => '/',         'site_id' => $network_ids['wordpress.org/'] ),
+			'wordpress.org/foo/'          => array( 'domain' => 'wordpress.org',      'path' => '/foo/',     'site_id' => $network_ids['wordpress.org/'] ),
+			'wordpress.org/foo/bar/'      => array( 'domain' => 'wordpress.org',      'path' => '/foo/bar/', 'site_id' => $network_ids['wordpress.org/'] ),
+			'make.wordpress.org/'         => array( 'domain' => 'make.wordpress.org', 'path' => '/',         'site_id' => $network_ids['make.wordpress.org/'] ),
+			'make.wordpress.org/foo/'     => array( 'domain' => 'make.wordpress.org', 'path' => '/foo/',     'site_id' => $network_ids['make.wordpress.org/'] ),
+		);
+
+		foreach ( $ids as &$id ) {
+			$id = $this->factory->blog->create( $id );
+		}
+		unset( $id );
+
+		$this->_setup_host_request( 'wordpress.org', '/' );
+		$this->assertEquals( $ids['wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/2014/04/23/hello-world/' );
+		$this->assertEquals( $ids['wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/sample-page/' );
+		$this->assertEquals( $ids['wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/?p=1' );
+		$this->assertEquals( $ids['wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/wp-admin/' );
+		$this->assertEquals( $ids['wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/foo/' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/FOO/' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/foo/2014/04/23/hello-world/' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/foo/sample-page/' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/foo/?p=1' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'wordpress.org', '/foo/wp-admin/' );
+		$this->assertEquals( $ids['wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		// @todo not currently passing.
+		//$this->_setup_host_request( 'wordpress.org', '/foo/bar/' );
+		//$this->assertEquals( $ids['wordpress.org/foo/bar/'], $current_blog->blog_id );
+		//$this->assertEquals( $network_ids['wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'make.wordpress.org', '/' );
+		$this->assertEquals( $ids['make.wordpress.org/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['make.wordpress.org/'], $current_blog->site_id );
+
+		$this->_setup_host_request( 'make.wordpress.org', '/foo/' );
+		$this->assertEquals( $ids['make.wordpress.org/foo/'], $current_blog->blog_id );
+		$this->assertEquals( $network_ids['make.wordpress.org/'], $current_blog->site_id );
+	}
+
+	/**
+	 * Reset various globals required for a 'clean' multisite boot.
+	 *
+	 * The $wpdb and $table_prefix globals are required for ms-settings.php to
+	 * load properly.
+	 *
+	 * @param string $domain HTTP_HOST of the bootstrap request.
+	 * @param string $path   REQUEST_URI of the boot strap request.
+	 */
+	function _setup_host_request( $domain, $path ) {
+		global $current_site, $current_blog, $wpdb, $table_prefix;
+
+		$current_site = $current_blog = null;
+		$_SERVER['HTTP_HOST'] = $domain;
+		$_SERVER['REQUEST_URI'] = $path;
+
+		include ABSPATH . '/wp-includes/ms-settings.php';
+	}
 }
 
 endif;