config: make internal links in network topology unidirectional.

This patch makes the internal links within the network topology
unidirectional, thus allowing any deadlock-free routing algorithms to
be specified from the topology itself using weights.
This patch also renames Mesh.py and MeshDirCorners.py to
Mesh_XY.py and MeshDirCorners_XY.py (Mesh with XY routing).
It also adds a Mesh_westfirst.py and CrossbarGarnet.py topologies.

20 files changed, 295 insertions, 173 deletions

diff --git a/configs/topologies/Cluster.py b/configs/topologies/Cluster.py
index b146d8675..fad90856d 100644
--- a/configs/topologies/Cluster.py
+++ b/configs/topologies/Cluster.py
@@ -86,23 +86,30 @@ class Cluster(BaseTopology):
                 node.makeTopology(options, network, IntLink, ExtLink, Router)
 
                 # connect this cluster to the router
-                link = IntLink(link_id=self.num_int_links(), node_a=self.router,
-                        node_b=node.router)
+                link_out = IntLink(link_id=self.num_int_links(), src_node=self.router,
+                           dst_node_=node.router)
+                link_in = IntLink(link_id=self.num_int_links(), src_node=node.router,
+                                  dst_node_=self.router)
 
                 if node.extBW:
-                    link.bandwidth_factor = node.extBW
+                    link_out.bandwidth_factor = node.extBW
+                    link_in.bandwidth_factor = node.extBW
 
-                # if there is an interanl b/w for this node
+                # if there is an internal b/w for this node
                 # and no ext b/w to override
                 elif self.intBW:
-                    link.bandwidth_factor = self.intBW
+                    link_out.bandwidth_factor = self.intBW
+                    link_in.bandwidth_factor = self.intBW
 
                 if node.extLatency:
-                    link.latency = node.extLatency
+                    link_out.latency = node.extLatency
+                    link_in.latency = node.extLatency
                 elif self.intLatency:
-                    link.latency = self.intLatency
+                    link_out.latency = self.intLatency
+                    link_in.latency = self.intLatency
 
-                network.int_links.append(link)
+                network.int_links.append(link_out)
+                network.int_links.append(link_in)
             else:
                 # node is just a controller,
                 # connect it to the router via a ext_link
diff --git a/configs/topologies/Crossbar.py b/configs/topologies/Crossbar.py
index e3dd431e7..35d20de34 100644
--- a/configs/topologies/Crossbar.py
+++ b/configs/topologies/Crossbar.py
@@ -39,6 +39,7 @@ class Crossbar(SimpleTopology):
         # the centralized crossbar.  The large numbers of routers are needed
         # because external links do not model outgoing bandwidth in the
         # simple network, but internal links do.
+        # For garnet, one router suffices, use CrossbarGarnet.py
 
         routers = [Router(router_id=i) for i in range(len(self.nodes)+1)]
         xbar = routers[len(self.nodes)] # the crossbar router is the last router created
@@ -49,7 +50,18 @@ class Crossbar(SimpleTopology):
         network.ext_links = ext_links
 
         link_count = len(self.nodes)
-        int_links = [IntLink(link_id=(link_count+i),
-                             node_a=routers[i], node_b=xbar)
-                        for i in range(len(self.nodes))]
+
+        int_links = []
+        for i in range(len(self.nodes)):
+            int_links.append(IntLink(link_id=(link_count+i),
+                                     src_node=routers[i],
+                                     dst_node=xbar))
+
+        link_count += len(self.nodes)
+
+        for i in range(len(self.nodes)):
+            int_links.append(IntLink(link_id=(link_count+i),
+                                     src_node=xbar,
+                                     dst_node=routers[i]))
+
         network.int_links = int_links
diff --git a/configs/topologies/CrossbarGarnet.py b/configs/topologies/CrossbarGarnet.py
new file mode 100644
index 000000000..64f8001e2
--- /dev/null
+++ b/configs/topologies/CrossbarGarnet.py
@@ -0,0 +1,50 @@
+# Copyright (c) 2016 Georgia Institute of Technology
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#
+# Authors: Tushar Krishna
+
+from m5.params import *
+from m5.objects import *
+
+from BaseTopology import SimpleTopology
+
+class CrossbarGarnet(SimpleTopology):
+    description='CrossbarGarnet'
+
+    def makeTopology(self, options, network, IntLink, ExtLink, Router):
+        # Create one router in Garnet. Internally models a crossbar and
+        # the associated allocator.
+        # For simple network, use Crossbar.py
+
+        xbar = Router(router_id=0)
+        network.routers = xbar
+
+        ext_links = [ExtLink(link_id=i, ext_node=n, int_node=xbar)
+                        for (i, n) in enumerate(self.nodes)]
+        network.ext_links = ext_links
+
+        int_links = []
+        network.int_links = int_links
diff --git a/configs/topologies/MeshDirCorners.py b/configs/topologies/MeshDirCorners_XY.py
index 40720004e..47eb48086 100644
--- a/configs/topologies/MeshDirCorners.py
+++ b/configs/topologies/MeshDirCorners_XY.py
@@ -31,17 +31,16 @@ from m5.objects import *
 
 from BaseTopology import SimpleTopology
 
-class MeshDirCorners(SimpleTopology):
-    description='MeshDirCorners'
+# Creates a Mesh topology with 4 directories, one at each corner.
+# One L1 (and L2, depending on the protocol) are connected to each router.
+# XY routing is enforced (using link weights) to guarantee deadlock freedom.
+
+class MeshDirCorners_XY(SimpleTopology):
+    description='MeshDirCorners_XY'
 
     def __init__(self, controllers):
         self.nodes = controllers
 
-    # This file contains a special network creation function.  This
-    # networks is not general and will only work with specific system
-    # configurations.  The network specified is similar to GEMS old file
-    # specified network.
-
     def makeTopology(self, options, network, IntLink, ExtLink, Router):
         nodes = self.nodes
 
@@ -110,29 +109,56 @@ class MeshDirCorners(SimpleTopology):
 
         network.ext_links = ext_links
 
-        # Create the mesh links.  First row (east-west) links then column
-        # (north-south) links
+        # Create the mesh links.
         int_links = []
+
+        # East output to West input links (weight = 1)
+        for row in xrange(num_rows):
+            for col in xrange(num_columns):
+                if (col + 1 < num_columns):
+                    east_out = col + (row * num_columns)
+                    west_in = (col + 1) + (row * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[east_out],
+                                             dst_node=routers[west_in],
+                                             weight=1))
+                    link_count += 1
+
+        # West output to East input links (weight = 1)
         for row in xrange(num_rows):
             for col in xrange(num_columns):
                 if (col + 1 < num_columns):
-                    east_id = col + (row * num_columns)
-                    west_id = (col + 1) + (row * num_columns)
+                    east_in = col + (row * num_columns)
+                    west_out = (col + 1) + (row * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[west_out],
+                                             dst_node=routers[east_in],
+                                             weight=1))
+                    link_count += 1
+
+        # North output to South input links (weight = 2)
+        for col in xrange(num_columns):
+            for row in xrange(num_rows):
+                if (row + 1 < num_rows):
+                    north_out = col + (row * num_columns)
+                    south_in = col + ((row + 1) * num_columns)
                     int_links.append(IntLink(link_id=link_count,
-                                            node_a=routers[east_id],
-                                            node_b=routers[west_id],
-                                            weight=1))
+                                             src_node=routers[north_out],
+                                             dst_node=routers[south_in],
+                                             weight=2))
                     link_count += 1
 
+        # South output to North input links (weight = 2)
         for col in xrange(num_columns):
             for row in xrange(num_rows):
                 if (row + 1 < num_rows):
-                    north_id = col + (row * num_columns)
-                    south_id = col + ((row + 1) * num_columns)
+                    north_in = col + (row * num_columns)
+                    south_out = col + ((row + 1) * num_columns)
                     int_links.append(IntLink(link_id=link_count,
-                                            node_a=routers[north_id],
-                                            node_b=routers[south_id],
-                                            weight=2))
+                                             src_node=routers[south_out],
+                                             dst_node=routers[north_in],
+                                             weight=2))
                     link_count += 1
 
+
         network.int_links = int_links
diff --git a/configs/topologies/Mesh.py b/configs/topologies/Mesh_XY.py
index 446fc4a18..adf3ebe49 100644
--- a/configs/topologies/Mesh.py
+++ b/configs/topologies/Mesh_XY.py
@@ -1,4 +1,5 @@
 # Copyright (c) 2010 Advanced Micro Devices, Inc.
+#               2016 Georgia Institute of Technology
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -25,19 +26,26 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 # Authors: Brad Beckmann
+#          Tushar Krishna
 
 from m5.params import *
 from m5.objects import *
 
 from BaseTopology import SimpleTopology
 
-class Mesh(SimpleTopology):
-    description='Mesh'
+# Creates a generic Mesh assuming an equal number of cache
+# and directory controllers.
+# XY routing is enforced (using link weights)
+# to guarantee deadlock freedom.
+
+class Mesh_XY(SimpleTopology):
+    description='Mesh_XY'
 
     def __init__(self, controllers):
         self.nodes = controllers
 
-    # Makes a generic mesh assuming an equal number of cache and directory cntrls
+    # Makes a generic mesh
+    # assuming an equal number of cache and directory cntrls
 
     def makeTopology(self, options, network, IntLink, ExtLink, Router):
         nodes = self.nodes
@@ -89,29 +97,56 @@ class Mesh(SimpleTopology):
 
         network.ext_links = ext_links
 
-        # Create the mesh links.  First row (east-west) links then column
-        # (north-south) links
+        # Create the mesh links.
         int_links = []
+
+        # East output to West input links (weight = 1)
+        for row in xrange(num_rows):
+            for col in xrange(num_columns):
+                if (col + 1 < num_columns):
+                    east_out = col + (row * num_columns)
+                    west_in = (col + 1) + (row * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[east_out],
+                                             dst_node=routers[west_in],
+                                             weight=1))
+                    link_count += 1
+
+        # West output to East input links (weight = 1)
         for row in xrange(num_rows):
             for col in xrange(num_columns):
                 if (col + 1 < num_columns):
-                    east_id = col + (row * num_columns)
-                    west_id = (col + 1) + (row * num_columns)
+                    east_in = col + (row * num_columns)
+                    west_out = (col + 1) + (row * num_columns)
                     int_links.append(IntLink(link_id=link_count,
-                                            node_a=routers[east_id],
-                                            node_b=routers[west_id],
-                                            weight=1))
+                                             src_node=routers[west_out],
+                                             dst_node=routers[east_in],
+                                             weight=1))
                     link_count += 1
 
+        # North output to South input links (weight = 2)
         for col in xrange(num_columns):
             for row in xrange(num_rows):
                 if (row + 1 < num_rows):
-                    north_id = col + (row * num_columns)
-                    south_id = col + ((row + 1) * num_columns)
+                    north_out = col + (row * num_columns)
+                    south_in = col + ((row + 1) * num_columns)
                     int_links.append(IntLink(link_id=link_count,
-                                            node_a=routers[north_id],
-                                            node_b=routers[south_id],
-                                            weight=2))
+                                             src_node=routers[north_out],
+                                             dst_node=routers[south_in],
+                                             weight=2))
                     link_count += 1
 
+        # South output to North input links (weight = 2)
+        for col in xrange(num_columns):
+            for row in xrange(num_rows):
+                if (row + 1 < num_rows):
+                    north_in = col + (row * num_columns)
+                    south_out = col + ((row + 1) * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[south_out],
+                                             dst_node=routers[north_in],
+                                             weight=2))
+                    link_count += 1
+
+
         network.int_links = int_links
diff --git a/configs/topologies/Torus.py b/configs/topologies/Mesh_westfirst.py
index db67d3ede..3af894f93 100644
--- a/configs/topologies/Torus.py
+++ b/configs/topologies/Mesh_westfirst.py
@@ -1,5 +1,5 @@
-# Copyright (c) 2011 Advanced Micro Devices, Inc.
-#               2011 Massachusetts Institute of Technology
+# Copyright (c) 2010 Advanced Micro Devices, Inc.
+#               2016 Georgia Institute of Technology
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -33,16 +33,24 @@ from m5.objects import *
 
 from BaseTopology import SimpleTopology
 
-class Torus(SimpleTopology):
-    description='Torus'
+# Creates a generic Mesh assuming an equal number of cache
+# and directory controllers.
+# West-first routing is enforced (using link weights)
+# to guarantee deadlock freedom.
+# The network randomly chooses between links with the same
+# weight for messages within unordered virtual networks.
+# Within ordered virtual networks, a fixed link direction
+# is always chosen based on which appears first inside the
+# routing table.
+
+class Mesh_westfirst(SimpleTopology):
+    description='Mesh_westfirst'
 
     def __init__(self, controllers):
         self.nodes = controllers
 
-    # Makes a generic torus assuming an equal number of cache and directory cntrls
-    # Assuming a folded-torus on-chip layout (as shown on gem5 wiki).
-    # All links (including the wrap-around ones) are of equal length, double that
-    # of a mesh. Thus, each link is assigned a latency of 2 cycles.
+    # Makes a generic mesh
+    # assuming an equal number of cache and directory cntrls
 
     def makeTopology(self, options, network, IntLink, ExtLink, Router):
         nodes = self.nodes
@@ -57,7 +65,7 @@ class Torus(SimpleTopology):
         num_columns = int(num_routers / num_rows)
         assert(num_columns * num_rows == num_routers)
 
-        # Create the routers in the torus
+        # Create the routers in the mesh
         routers = [Router(router_id=i) for i in range(num_routers)]
         network.routers = routers
 
@@ -94,36 +102,57 @@ class Torus(SimpleTopology):
 
         network.ext_links = ext_links
 
-        # Create the torus links.  First row (east-west) links then column
-        # (north-south) links
-        # column links are given higher weights to implement XY routing
+        # Create the mesh links.
         int_links = []
+
+        # East output to West input links (weight = 2)
+        for row in xrange(num_rows):
+            for col in xrange(num_columns):
+                if (col + 1 < num_columns):
+                    east_out = col + (row * num_columns)
+                    west_in = (col + 1) + (row * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[east_out],
+                                             dst_node=routers[west_in],
+                                             weight=2))
+                    link_count += 1
+
+        # West output to East input links (weight = 1)
         for row in xrange(num_rows):
             for col in xrange(num_columns):
-                west_id = col + (row * num_columns)
                 if (col + 1 < num_columns):
-                    east_id = (col + 1) + (row * num_columns)
-                else:
-                    east_id = (row * num_columns)
-                int_links.append(IntLink(link_id=link_count,
-                                        node_a=routers[east_id],
-                                        node_b=routers[west_id],
-                                        latency=2,
-                                        weight=1))
-                link_count += 1
+                    east_in = col + (row * num_columns)
+                    west_out = (col + 1) + (row * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[west_out],
+                                             dst_node=routers[east_in],
+                                             weight=1))
+                    link_count += 1
 
+
+        # North output to South input links (weight = 2)
         for col in xrange(num_columns):
             for row in xrange(num_rows):
-                north_id = col + (row * num_columns)
                 if (row + 1 < num_rows):
-                    south_id = col + ((row + 1) * num_columns)
-                else:
-                    south_id = col
-                int_links.append(IntLink(link_id=link_count,
-                                        node_a=routers[north_id],
-                                        node_b=routers[south_id],
-                                        latency=2,
-                                        weight=2))
-                link_count += 1
+                    north_out = col + (row * num_columns)
+                    south_in = col + ((row + 1) * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[north_out],
+                                             dst_node=routers[south_in],
+                                             weight=2))
+                    link_count += 1
+
+        # South output to North input links (weight = 2)
+        for col in xrange(num_columns):
+            for row in xrange(num_rows):
+                if (row + 1 < num_rows):
+                    north_in = col + (row * num_columns)
+                    south_out = col + ((row + 1) * num_columns)
+                    int_links.append(IntLink(link_id=link_count,
+                                             src_node=routers[south_out],
+                                             dst_node=routers[north_in],
+                                             weight=2))
+                    link_count += 1
+
 
         network.int_links = int_links
diff --git a/configs/topologies/Pt2Pt.py b/configs/topologies/Pt2Pt.py
index 8fada26bf..006d00c2f 100644
--- a/configs/topologies/Pt2Pt.py
+++ b/configs/topologies/Pt2Pt.py
@@ -57,7 +57,7 @@ class Pt2Pt(SimpleTopology):
                 if (i != j):
                     link_count += 1
                     int_links.append(IntLink(link_id=link_count,
-                                            node_a=routers[i],
-                                            node_b=routers[j]))
+                                             src_node=routers[i],
+                                             dst_node=routers[j]))
 
         network.int_links = int_links
diff --git a/src/mem/ruby/network/BasicLink.cc b/src/mem/ruby/network/BasicLink.cc
index 292e74e96..2b55e7ec8 100644
--- a/src/mem/ruby/network/BasicLink.cc
+++ b/src/mem/ruby/network/BasicLink.cc
@@ -56,8 +56,6 @@ BasicLinkParams::create()
 BasicExtLink::BasicExtLink(const Params *p)
     : BasicLink(p)
 {
-    m_int_node = p->int_node;
-    m_ext_node = p->ext_node;
 }
 
 BasicExtLink *
@@ -69,8 +67,6 @@ BasicExtLinkParams::create()
 BasicIntLink::BasicIntLink(const Params *p)
     : BasicLink(p)
 {
-    m_node_a = p->node_a;
-    m_node_b = p->node_b;
 }
 
 BasicIntLink *
diff --git a/src/mem/ruby/network/BasicLink.hh b/src/mem/ruby/network/BasicLink.hh
index 634b9143e..188f62941 100644
--- a/src/mem/ruby/network/BasicLink.hh
+++ b/src/mem/ruby/network/BasicLink.hh
@@ -73,10 +73,6 @@ class BasicExtLink : public BasicLink
     const Params *params() const { return (const Params *)_params; }
 
     friend class Topology;
-
-  protected:
-    BasicRouter* m_int_node;
-    AbstractController* m_ext_node;
 };
 
 class BasicIntLink : public BasicLink
@@ -87,10 +83,6 @@ class BasicIntLink : public BasicLink
     const Params *params() const { return (const Params *)_params; }
 
     friend class Topology;
-
-  protected:
-    BasicRouter* m_node_a;
-    BasicRouter* m_node_b;
 };
 
 #endif // __MEM_RUBY_NETWORK_BASIC_LINK_HH__
diff --git a/src/mem/ruby/network/BasicLink.py b/src/mem/ruby/network/BasicLink.py
index 8fc83c9e2..5da5dc6a2 100644
--- a/src/mem/ruby/network/BasicLink.py
+++ b/src/mem/ruby/network/BasicLink.py
@@ -35,10 +35,9 @@ class BasicLink(SimObject):
     cxx_header = "mem/ruby/network/BasicLink.hh"
     link_id = Param.Int("ID in relation to other links")
     latency = Param.Cycles(1, "latency")
-    # The following banwidth factor does not translate to the same value for
-    # both the simple and Garnet models.  For the most part, the bandwidth
-    # factor is the width of the link in bytes, expect for certain situations
-    # with regard to the simple network.
+    # Width of the link in bytes
+    # Only used by simple network.
+    # Garnet models this by flit size
     bandwidth_factor = Param.Int("generic bandwidth factor, usually in bytes")
     weight = Param.Int(1, "used to restrict routing in shortest path analysis")
 
@@ -52,6 +51,6 @@ class BasicExtLink(BasicLink):
 class BasicIntLink(BasicLink):
     type = 'BasicIntLink'
     cxx_header = "mem/ruby/network/BasicLink.hh"
-    node_a = Param.BasicRouter("Router on one end")
-    node_b = Param.BasicRouter("Router on other end")
+    src_node = Param.BasicRouter("Router on src end")
+    dst_node = Param.BasicRouter("Router on dst end")
     bandwidth_factor = 16
diff --git a/src/mem/ruby/network/Network.hh b/src/mem/ruby/network/Network.hh
index c06ee5a1a..529408696 100644
--- a/src/mem/ruby/network/Network.hh
+++ b/src/mem/ruby/network/Network.hh
@@ -80,14 +80,11 @@ class Network : public ClockedObject
     virtual void checkNetworkAllocation(NodeID id, bool ordered,
         int network_num, std::string vnet_type);
 
-    virtual void makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                             LinkDirection direction,
+    virtual void makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                              const NetDest& routing_table_entry) = 0;
-    virtual void makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                            LinkDirection direction,
+    virtual void makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                             const NetDest& routing_table_entry) = 0;
     virtual void makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                                  LinkDirection direction,
                                   const NetDest& routing_table_entry) = 0;
 
     virtual void collateStats() = 0;
diff --git a/src/mem/ruby/network/Topology.cc b/src/mem/ruby/network/Topology.cc
index 757efe063..f73e686c5 100644
--- a/src/mem/ruby/network/Topology.cc
+++ b/src/mem/ruby/network/Topology.cc
@@ -55,10 +55,14 @@ Topology::Topology(uint32_t num_routers,
     // Total nodes/controllers in network
     assert(m_nodes > 1);
 
-    // analyze both the internal and external links, create data structures
-    // Note that the python created links are bi-directional, but that the
-    // topology and networks utilize uni-directional links.  Thus each
-    // BasicLink is converted to two calls to add link, on for each direction
+    // analyze both the internal and external links, create data structures.
+    // The python created external links are bi-directional,
+    // and the python created internal links are uni-directional.
+    // The networks and topology utilize uni-directional links.
+    // Thus each external link is converted to two calls to addLink,
+    // one for each direction.
+    //
+    // External Links
     for (vector<BasicExtLink*>::const_iterator i = ext_links.begin();
          i != ext_links.end(); ++i) {
         BasicExtLink *ext_link = (*i);
@@ -71,29 +75,27 @@ Topology::Topology(uint32_t num_routers,
         int int_idx = router->params()->router_id + 2*m_nodes;
 
         // create the internal uni-directional links in both directions
-        //   the first direction is marked: In
-        addLink(ext_idx1, int_idx, ext_link, LinkDirection_In);
-        //   the first direction is marked: Out
-        addLink(int_idx, ext_idx2, ext_link, LinkDirection_Out);
+        // ext to int
+        addLink(ext_idx1, int_idx, ext_link);
+        // int to ext
+        addLink(int_idx, ext_idx2, ext_link);
     }
 
+    // Internal Links
     for (vector<BasicIntLink*>::const_iterator i = int_links.begin();
          i != int_links.end(); ++i) {
         BasicIntLink *int_link = (*i);
-        BasicRouter *router_a = int_link->params()->node_a;
-        BasicRouter *router_b = int_link->params()->node_b;
+        BasicRouter *router_src = int_link->params()->src_node;
+        BasicRouter *router_dst = int_link->params()->dst_node;
 
         // Store the IntLink pointers for later
         m_int_link_vector.push_back(int_link);
 
-        int a = router_a->params()->router_id + 2*m_nodes;
-        int b = router_b->params()->router_id + 2*m_nodes;
+        int src = router_src->params()->router_id + 2*m_nodes;
+        int dst = router_dst->params()->router_id + 2*m_nodes;
 
-        // create the internal uni-directional links in both directions
-        //   the first direction is marked: In
-        addLink(a, b, int_link, LinkDirection_In);
-        //   the second direction is marked: Out
-        addLink(b, a, int_link, LinkDirection_Out);
+        // create the internal uni-directional link from src to dst
+        addLink(src, dst, int_link);
     }
 }
 
@@ -151,8 +153,7 @@ Topology::createLinks(Network *net)
 }
 
 void
-Topology::addLink(SwitchID src, SwitchID dest, BasicLink* link,
-                  LinkDirection dir)
+Topology::addLink(SwitchID src, SwitchID dest, BasicLink* link)
 {
     assert(src <= m_number_of_switches+m_nodes+m_nodes);
     assert(dest <= m_number_of_switches+m_nodes+m_nodes);
@@ -162,7 +163,6 @@ Topology::addLink(SwitchID src, SwitchID dest, BasicLink* link,
 
     src_dest_pair.first = src;
     src_dest_pair.second = dest;
-    link_entry.direction = dir;
     link_entry.link = link;
     m_link_map[src_dest_pair] = link_entry;
 }
@@ -182,23 +182,23 @@ Topology::makeLink(Network *net, SwitchID src, SwitchID dest,
         src_dest.first = src;
         src_dest.second = dest;
         link_entry = m_link_map[src_dest];
-        net->makeInLink(src, dest - (2 * m_nodes), link_entry.link,
-                        link_entry.direction, routing_table_entry);
+        net->makeExtInLink(src, dest - (2 * m_nodes), link_entry.link,
+                        routing_table_entry);
     } else if (dest < 2*m_nodes) {
         assert(dest >= m_nodes);
         NodeID node = dest - m_nodes;
         src_dest.first = src;
         src_dest.second = dest;
         link_entry = m_link_map[src_dest];
-        net->makeOutLink(src - (2 * m_nodes), node, link_entry.link,
-                         link_entry.direction, routing_table_entry);
+        net->makeExtOutLink(src - (2 * m_nodes), node, link_entry.link,
+                         routing_table_entry);
     } else {
         assert((src >= 2 * m_nodes) && (dest >= 2 * m_nodes));
         src_dest.first = src;
         src_dest.second = dest;
         link_entry = m_link_map[src_dest];
         net->makeInternalLink(src - (2 * m_nodes), dest - (2 * m_nodes),
-                              link_entry.link, link_entry.direction,
+                              link_entry.link,
                               routing_table_entry);
     }
 }
diff --git a/src/mem/ruby/network/Topology.hh b/src/mem/ruby/network/Topology.hh
index d55ba99a9..7e0b12c63 100644
--- a/src/mem/ruby/network/Topology.hh
+++ b/src/mem/ruby/network/Topology.hh
@@ -72,8 +72,7 @@ class Topology
     void print(std::ostream& out) const { out << "[Topology]"; }
 
   private:
-    void addLink(SwitchID src, SwitchID dest, BasicLink* link,
-                 LinkDirection dir);
+    void addLink(SwitchID src, SwitchID dest, BasicLink* link);
     void makeLink(Network *net, SwitchID src, SwitchID dest,
                   const NetDest& routing_table_entry);
 
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
index ce919335e..1e36a4cf0 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.cc
@@ -127,15 +127,14 @@ GarnetNetwork_d::~GarnetNetwork_d()
 */
 
 void
-GarnetNetwork_d::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                            LinkDirection direction,
+GarnetNetwork_d::makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                             const NetDest& routing_table_entry)
 {
     assert(src < m_nodes);
 
     GarnetExtLink_d* garnet_link = safe_cast<GarnetExtLink_d*>(link);
-    NetworkLink_d* net_link = garnet_link->m_network_links[direction];
-    CreditLink_d* credit_link = garnet_link->m_credit_links[direction];
+    NetworkLink_d* net_link = garnet_link->m_network_links[0];
+    CreditLink_d* credit_link = garnet_link->m_credit_links[0];
 
     m_links.push_back(net_link);
     m_creditlinks.push_back(credit_link);
@@ -151,8 +150,7 @@ GarnetNetwork_d::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
 */
 
 void
-GarnetNetwork_d::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                             LinkDirection direction,
+GarnetNetwork_d::makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                              const NetDest& routing_table_entry)
 {
     assert(dest < m_nodes);
@@ -160,8 +158,8 @@ GarnetNetwork_d::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
     assert(m_routers[src] != NULL);
 
     GarnetExtLink_d* garnet_link = safe_cast<GarnetExtLink_d*>(link);
-    NetworkLink_d* net_link = garnet_link->m_network_links[direction];
-    CreditLink_d* credit_link = garnet_link->m_credit_links[direction];
+    NetworkLink_d* net_link = garnet_link->m_network_links[1];
+    CreditLink_d* credit_link = garnet_link->m_credit_links[1];
 
     m_links.push_back(net_link);
     m_creditlinks.push_back(credit_link);
@@ -177,12 +175,11 @@ GarnetNetwork_d::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
 
 void
 GarnetNetwork_d::makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                                  LinkDirection direction,
                                   const NetDest& routing_table_entry)
 {
     GarnetIntLink_d* garnet_link = safe_cast<GarnetIntLink_d*>(link);
-    NetworkLink_d* net_link = garnet_link->m_network_links[direction];
-    CreditLink_d* credit_link = garnet_link->m_credit_links[direction];
+    NetworkLink_d* net_link = garnet_link->m_network_links[0];
+    CreditLink_d* credit_link = garnet_link->m_credit_links[0];
 
     m_links.push_back(net_link);
     m_creditlinks.push_back(credit_link);
diff --git a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.hh b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.hh
index 99ecc02da..a11f3ea50 100644
--- a/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.hh
+++ b/src/mem/ruby/network/garnet/fixed-pipeline/GarnetNetwork_d.hh
@@ -69,14 +69,11 @@ class GarnetNetwork_d : public BaseGarnetNetwork
     }
 
     // Methods used by Topology to setup the network
-    void makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                     LinkDirection direction,
+    void makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                      const NetDest& routing_table_entry);
-    void makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                    LinkDirection direction,
+    void makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                     const NetDest& routing_table_entry);
     void makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                          LinkDirection direction,
                           const NetDest& routing_table_entry);
 
     //! Function for performing a functional write. The return value
diff --git a/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.cc b/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.cc
index bd96fc2ed..0b33ab009 100644
--- a/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.cc
+++ b/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.cc
@@ -94,14 +94,13 @@ GarnetNetwork::~GarnetNetwork()
 }
 
 void
-GarnetNetwork::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                          LinkDirection direction,
+GarnetNetwork::makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                           const NetDest& routing_table_entry)
 {
     assert(src < m_nodes);
 
     GarnetExtLink* garnet_link = safe_cast<GarnetExtLink*>(link);
-    NetworkLink *net_link = garnet_link->m_network_links[direction];
+    NetworkLink *net_link = garnet_link->m_network_links[0];
 
     net_link->init_net_ptr(this);
     m_links.push_back(net_link);
@@ -110,8 +109,7 @@ GarnetNetwork::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
 }
 
 void
-GarnetNetwork::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                           LinkDirection direction,
+GarnetNetwork::makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                            const NetDest& routing_table_entry)
 {
     assert(dest < m_nodes);
@@ -119,7 +117,7 @@ GarnetNetwork::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
     assert(m_routers[src] != NULL);
 
     GarnetExtLink* garnet_link = safe_cast<GarnetExtLink*>(link);
-    NetworkLink *net_link = garnet_link->m_network_links[direction];
+    NetworkLink *net_link = garnet_link->m_network_links[1];
 
     net_link->init_net_ptr(this);
     m_links.push_back(net_link);
@@ -130,11 +128,10 @@ GarnetNetwork::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
 
 void
 GarnetNetwork::makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                                LinkDirection direction,
                                 const NetDest& routing_table_entry)
 {
     GarnetIntLink* garnet_link = safe_cast<GarnetIntLink*>(link);
-    NetworkLink *net_link = garnet_link->m_network_links[direction];
+    NetworkLink *net_link = garnet_link->m_network_links[0];
 
     net_link->init_net_ptr(this);
     m_links.push_back(net_link);
diff --git a/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.hh b/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.hh
index e9b94809f..18360d475 100644
--- a/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.hh
+++ b/src/mem/ruby/network/garnet/flexible-pipeline/GarnetNetwork.hh
@@ -60,14 +60,11 @@ class GarnetNetwork : public BaseGarnetNetwork
     void print(std::ostream& out) const;
 
     // Methods used by Topology to setup the network
-    void makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                     LinkDirection direction,
+    void makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                      const NetDest& routing_table_entry);
-    void makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                    LinkDirection direction,
+    void makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                     const NetDest& routing_table_entry);
     void makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                          LinkDirection direction,
                           const NetDest& routing_table_entry);
 
     //! Function for performing a functional read. The return value
diff --git a/src/mem/ruby/network/simple/SimpleNetwork.cc b/src/mem/ruby/network/simple/SimpleNetwork.cc
index 2fc7b6440..b30bd8731 100644
--- a/src/mem/ruby/network/simple/SimpleNetwork.cc
+++ b/src/mem/ruby/network/simple/SimpleNetwork.cc
@@ -78,8 +78,7 @@ SimpleNetwork::~SimpleNetwork()
 
 // From a switch to an endpoint node
 void
-SimpleNetwork::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                           LinkDirection direction,
+SimpleNetwork::makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                            const NetDest& routing_table_entry)
 {
     assert(dest < m_nodes);
@@ -95,8 +94,7 @@ SimpleNetwork::makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
 
 // From an endpoint node to a switch
 void
-SimpleNetwork::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                          LinkDirection direction,
+SimpleNetwork::makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                           const NetDest& routing_table_entry)
 {
     assert(src < m_nodes);
@@ -106,7 +104,6 @@ SimpleNetwork::makeInLink(NodeID src, SwitchID dest, BasicLink* link,
 // From a switch to a switch
 void
 SimpleNetwork::makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                                LinkDirection direction,
                                 const NetDest& routing_table_entry)
 {
     // Create a set of new MessageBuffers
diff --git a/src/mem/ruby/network/simple/SimpleNetwork.hh b/src/mem/ruby/network/simple/SimpleNetwork.hh
index 434dfa702..6a325d2a4 100644
--- a/src/mem/ruby/network/simple/SimpleNetwork.hh
+++ b/src/mem/ruby/network/simple/SimpleNetwork.hh
@@ -59,14 +59,11 @@ class SimpleNetwork : public Network
     bool isVNetOrdered(int vnet) const { return m_ordered[vnet]; }
 
     // Methods used by Topology to setup the network
-    void makeOutLink(SwitchID src, NodeID dest, BasicLink* link,
-                     LinkDirection direction,
+    void makeExtOutLink(SwitchID src, NodeID dest, BasicLink* link,
                      const NetDest& routing_table_entry);
-    void makeInLink(NodeID src, SwitchID dest, BasicLink* link,
-                    LinkDirection direction,
+    void makeExtInLink(NodeID src, SwitchID dest, BasicLink* link,
                     const NetDest& routing_table_entry);
     void makeInternalLink(SwitchID src, SwitchID dest, BasicLink* link,
-                          LinkDirection direction,
                           const NetDest& routing_table_entry);
 
     void print(std::ostream& out) const;
diff --git a/src/mem/ruby/network/simple/SimpleNetwork.py b/src/mem/ruby/network/simple/SimpleNetwork.py
index 87de0fb46..3d6f7e854 100644
--- a/src/mem/ruby/network/simple/SimpleNetwork.py
+++ b/src/mem/ruby/network/simple/SimpleNetwork.py
@@ -56,12 +56,10 @@ class SimpleNetwork(RubyNetwork):
         # Also add buffers for all router-link connections
         for router in self.routers:
             router_buffers = []
-            # Add message buffers to routers for each internal link connection
+            # Add message buffers to routers at the end of each
+            # unidirectional internal link
             for link in self.int_links:
-                if link.node_a == router:
-                    for i in xrange(self.number_of_virtual_networks):
-                        router_buffers.append(MessageBuffer(ordered = True))
-                if link.node_b == router:
+                if link.dst_node == router:
                     for i in xrange(self.number_of_virtual_networks):
                         router_buffers.append(MessageBuffer(ordered = True))