diff --git a/bin/mn b/bin/mn
index aef64fe..d5cc0f1 100755
--- a/bin/mn
+++ b/bin/mn
@@ -30,7 +30,7 @@ from mininet.node import ( Host, CPULimitedHost, Controller, OVSController,
                            UserSwitch, OVSSwitch, OVSBridge,
                            IVSSwitch )
 from mininet.nodelib import LinuxBridge
-from mininet.link import Link, TCLink, OVSLink
+from mininet.link import Link, TCLink, TCULink, OVSLink
 from mininet.topo import ( SingleSwitchTopo, LinearTopo,
                            SingleSwitchReversedTopo, MinimalTopo )
 from mininet.topolib import TreeTopo, TorusTopo
@@ -73,18 +73,18 @@ HOSTS = { 'proc': Host,
           'cfs': specialClass( CPULimitedHost, defaults=dict( sched='cfs' ) ) }
 
 CONTROLLERDEF = 'default'
-
 CONTROLLERS = { 'ref': Controller,
                 'ovsc': OVSController,
                 'nox': NOX,
                 'remote': RemoteController,
                 'ryu': Ryu,
-                'default': DefaultController,  # Note: replaced below
+                'default': DefaultController,  # Note: overridden below
                 'none': NullController }
 
 LINKDEF = 'default'
-LINKS = { 'default': Link,
+LINKS = { 'default': Link,  # Note: overridden below
           'tc': TCLink,
+          'tcu': TCULink,
           'ovs': OVSLink }
 
 # TESTS dict can contain functions and/or Mininet() method names
@@ -341,11 +341,19 @@ class MininetRunner( object ):
                                      "for switch %s" %
                                      opts.switch )
 
+
+
         topo = buildTopo( TOPOS, opts.topo )
         switch = customClass( SWITCHES, opts.switch )
         host = customClass( HOSTS, opts.host )
         controller = [ customClass( CONTROLLERS, c )
                        for c in opts.controller ]
+
+        if opts.switch == 'user' and opts.link == 'default':
+            debug( '*** Using TCULink with UserSwitch\n' )
+            # Use link configured correctly for UserSwitch
+            opts.link = 'tcu'
+
         link = customClass( LINKS, opts.link )
 
         if self.validate:
diff --git a/mininet/link.py b/mininet/link.py
index 81b12e4..eff9c97 100644
--- a/mininet/link.py
+++ b/mininet/link.py
@@ -313,16 +313,40 @@ class TCIntf( Intf ):
         return self.cmd( c )
 
     def config( self, bw=None, delay=None, jitter=None, loss=None,
-                disable_gro=True, speedup=0, use_hfsc=False, use_tbf=False,
+                gro=False, txo=True, rxo=True,
+                speedup=0, use_hfsc=False, use_tbf=False,
                 latency_ms=None, enable_ecn=False, enable_red=False,
                 max_queue_size=None, **params ):
-        "Configure the port and set its properties."
+        """Configure the port and set its properties.
+           bw: bandwidth in b/s (e.g. '10m')
+           delay: transmit delay (e.g. '1ms' )
+           jitter: jitter (e.g. '1ms')
+           loss: loss (e.g. '1%' )
+           gro: enable GRO (False)
+           txo: enable transmit checksum offload (True)
+           rxo: enable receive checksum offload (True)
+           speedup: experimental switch-side bw option
+           use_hfsc: use HFSC scheduling
+           use_tbf: use TBF scheduling
+           latency_ms: TBF latency parameter
+           enable_ecn: enable ECN (False)
+           enable_red: enable RED (False)
+           max_queue_size: queue limit parameter for netem"""
+
+        # Support old names for parameters
+        gro = not params.pop( 'disable_gro', not gro )
 
         result = Intf.config( self, **params)
 
-        # Disable GRO
-        if disable_gro:
-            self.cmd( 'ethtool -K %s gro off' % self )
+        def on( isOn ):
+            "Helper method: bool -> 'on'/'off'"
+            return 'on' if isOn else 'off'
+
+        # Set offload parameters with ethool
+        self.cmd( 'ethtool -K', self,
+                  'gro', on( gro ),
+                  'tx', on( txo ),
+                  'rx', on( rxo ) )
 
         # Optimization: return if nothing else to configure
         # Question: what happens if we want to reset things?
@@ -476,7 +500,7 @@ class Link( object ):
         self.intf1 = None
         self.intf2.delete()
         self.intf2 = None
-    
+
     def stop( self ):
         "Override to stop and clean up link as needed"
         self.delete()
@@ -535,3 +559,18 @@ class TCLink( Link ):
                        addr1=addr1, addr2=addr2,
                        params1=params,
                        params2=params )
+
+
+class TCULink( TCLink ):
+    """TCLink with default settings optimized for UserSwitch
+       (txo=rxo=0/False).  Unfortunately with recent Linux kernels,
+       enabling TX and RX checksum offload on veth pairs doesn't work
+       well with UserSwitch: either it gets terrible performance or
+       TCP packets with bad checksums are generated, forwarded, and
+       *dropped* due to having bad checksums! OVS and LinuxBridge seem
+       to cope with this somehow, but it is likely to be an issue with
+       many software Ethernet bridges."""
+
+    def __init__( self, *args, **kwargs ):
+        kwargs.update( txo=False, rxo=False )
+        TCLink.__init__( self, *args, **kwargs )