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+Network Working Group                                        B. Jamoussi
+Request for Comments: 2340                                   D. Jamieson
+Category: Informational                                     D. Williston
+                                                                 S. Gabe
+                                          Nortel (Northern Telecom) Ltd.
+                                                                May 1998
+
+
+           Nortel's Virtual Network Switching (VNS) Overview
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1998).  All Rights Reserved.
+
+Abstract
+
+   This document provides an overview of Virtual Network Switching
+   (VNS).
+
+   VNS is a multi-protocol switching architecture that provides COS-
+   sensitive packet switching, reduces the complexity of operating
+   protocols like PPP and frame relay, provides logical networks and
+   traffic segregation for Virtual Private Networks (VPNs), security and
+   traffic engineering, enables efficient WAN broadcasting and
+   multicasting, and reduces address space requirements. VNS reduces the
+   number of routing hops over the WAN by switching packets based on
+   labels.
+
+   VNS has been proven in production networks for several years.
+
+Table of Contents
+
+   1       Introduction ............................................   2
+   2       What is VNS? ............................................   3
+   3       VNS Header  .............................................   5
+   4       VNS Label Distribution ..................................   7
+   5     Logical Networks (LNs) ....................................   7
+   6       VNS Routing .............................................   8
+   7       VNS Forwarding ..........................................   9
+      7.1   Unicast ................................................   9
+      7.2   Multicast ..............................................   9
+   8       Traffic Engineering .....................................  10
+
+
+
+Jamoussi, et. al.            Informational                      [Page 1]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+      8.1   Equal Cost Multipaths ..................................  10
+      8.2   Trunk Load Spreading ...................................  10
+   9       Class of Service ........................................  11
+   10      VNS Migration Strategies ................................  11
+   11      Summary .................................................  11
+   12      Security Considerations .................................  12
+   13      Acknowledgments .........................................  12
+   14      Authors' Addresses ......................................  13
+   15      Full Copyright Statement ................................  14
+
+1. Introduction
+
+   There are several key problem areas with today's wide area backbone
+   networks that carry LAN traffic: scalability, service
+   differentiation, redundancy, administration, and traffic containment.
+
+   First, scalability is becoming a major concern because of the rapid
+   growth in bandwidth demand and geographical reach. As the size of the
+   WAN network grows traditional point-to-point and NBMA topologies or
+   network models lose their performance.
+
+   Second, the need to provide several Classes of Service (CoS) has
+   never been greater. The days of a single "best effort" service are
+   over and service providers demand ways to differentiate the quality
+   of the service offered to their clients based on several policies.
+
+   Third, the WAN is often carrying mission-critical traffic and loss of
+   service is not acceptable. So far, path redundancy has been addressed
+   inefficiently by requiring additional links or VCs.
+
+   Fourth, network operators demand easy and simplified network
+   administration. Large NBMA topologies require extensive PVC
+   provisioning until SVC  deployment becomes more ubiquitous. For
+   Point-to-point models, IP address space may be used inefficiently and
+   non-trivial network schemas are required to contain reserved address
+   space.
+
+   Finally, proper segregation of traffic is becoming a must. This
+   requirement is being addressed today by adding leased lines or VCs
+   used to separate traffic flows based on regions or interest or
+   protocol.
+
+   Nortel's Virtual Network Switching (VNS) is a technology that
+   provides efficient solutions to these challenges.
+
+
+
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 2]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   Section 2 provides an overview of VNS. The VNS header is specified in
+   Section 3. Section 4 describes the VNS label distribution mechanism.
+   Section 5 defines how a VNS network can be partitioned into Logical
+   Networks (LN). Section 6 outlines VNS routing. Section 7 defines both
+   unicast and multicast forwarding. Section 8 describes the mechanisms
+   used to engineer the traffic. Section 9 defines the COS based
+   switching of VNS. Section 10 provides network migration scenarios
+   using VNS. A summary of VNS is provided in Section 11.
+
+2. What is VNS?
+
+   Virtual Network Switching (VNS) is a CoS-sensitive multi-protocol
+   label switching architecture that reduces or eliminates the number of
+   layer 3 hops over the WAN by switching traffic based on labels.
+
+   VNS makes a network of point to point links  appear to be a single
+   LAN (broadcast, multiple access) media.  The network used by a
+   particular instance of VNS is called a Logical Network (LN) which is
+   described in more detail in Section 5.
+
+   In reference to the ISO Network Layering Model, the Data Link Layer
+   is expanded to include VNS network layer. To the ISO Network Layer,
+   (e.g., IP), VNS is treated as a Data Link Layer.
+
+           ------------------------
+           | Application          |
+           ------------------------
+           | Presentation         |
+           ------------------------
+           | Session              |
+           ------------------------
+           | Transport            |
+           ------------------------      -------------------------
+           | Network (e.g., IP)   |     / Network VNS            |
+           -----------------------------                         |
+           | Data Link                 |--------------------------
+           -----------------------------                         |
+           | Physical             |     \ data link (e.g., ATM)  |
+           ------------------------      -------------------------
+
+               Figure 1. ISO Network Layering Model for VNS
+
+   In a VNS Network, three separate nodal functions are defined.  An
+   ingress node, an egress node, and a tandem node. The ingress and
+   egress nodes define the boundary between an IP network and the VNS
+   network. Therefore, these nodes run both IP routing and VNS routing.
+   However, tandem nodes need only run VNS routing.
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 3]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   A LAN packet is encapsulated in a VNS header as it enters the LN. The
+   label in the header is used to switch the packet across the LN. The
+   encapsulation header contains the identifier of the last node (or
+   egress node) that processes the packet as it traverses the LN. It is
+   the first  node (or ingress node) that decides to which egress node
+   the packet is sent. All nodes between the ingress and egress nodes
+   (known as tandem nodes) decide independently the best packet
+   forwarding route to the egress node identified in the packet.
+
+   The network layer protocols view VNS as a shared broadcast media,
+   where the speed to reach any node on the media is the same for all
+   nodes. VNS ensures that traffic destined to other nodes is forwarded
+   optimally. This transparent view of the VNS means that all the
+   details of the network (for example, topology and link states) can be
+   hidden from the Upper Layer Protocols (e.g. Layer 3 routing
+   protocols) and their applications. VNS also ensures that changes to
+   topology and link state are hidden.
+
+   The network layer protocol on the ingress node views the network
+   layer protocol on the egress node as its logical and directly
+   connected neighbor. This is significant because the network layer
+   protocols always decide which directly connected neighbor should
+   receive a forwarded packet. The details of the actual topology
+   supporting the connectionless network are managed entirely by the
+   Virtual Network Switching and are hidden from the network layer
+   protocols. To the network layer, VNS simply appears to be another
+   Data Link Layer (or media), even though VNS is a network layer itself
+   running on top of the actual Data Link Layer (for example, ATM
+   trunks).
+
+   For the ingress node to choose the egress node that provides the best
+   path to the packet's final destination, it must have knowledge of the
+   following:
+
+      - the nodes that can be reached in the  network
+      - the topology of the network that is using the VNS services for
+        transport across the network (but not necessarily the topology
+        of the full network)
+
+   This knowledge is obtained through the network layer routing
+   mechanisms such as, IP's Open Shortest Path First (OSPF) and Address
+   Resolution Protocol (ARP).
+
+   Once the network layer protocol on the ingress node has decided which
+   neighbor to transmit the packet to, it is the responsibility of VNS
+   forwarding, a part of VNS, to deliver the packet to that node. Once
+   the packet arrives at the egress node, the packet is delivered to the
+   network layer protocol, which then forwards it to its ultimate
+
+
+
+Jamoussi, et. al.            Informational                      [Page 4]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   destination.
+
+   Tandem nodes have no interaction with the network layer protocols.
+   They only require knowledge of the  VNS network topology. They make
+   their packet forwarding decision on the egress node  identifier and
+   LN identifier carried in the VNS header of the packet.
+
+3. VNS Header
+
+   VNS defines a unicast header shown in Figure 2 and a multicast header
+   shown in Figure 3.
+
+       3                   2                   1                   0
+     1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |      TTL      |      LNN            |x|LS-Key |x|DP | CmnHdr  |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    | Protocol Type |         Destination Node Identifier           |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |  COS  |x x x x|         Source Node Identifier                |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |                 Network Layer Header (e.g. IP)                |
+    /                                                               /
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |                          Data                                 |
+    /                                                               /
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+                       Figure 2. Unicast VNS Header
+
+   The unicast header includes the following fields:
+
+   - Common Header (CmnHdr): The common header identifies the packet to
+   be a VNS encapsulated packet.
+
+   - Discard Priority: Indicates the level of congestion at which the
+   packet should be discarded. The value of this field is assigned on
+   the originating node based on policy information (see Section 9).
+
+   - Load Spreading Key: indicates the stream to which the packet
+   belongs for the purposes of equal cost multipath and trunk load
+   spreading (see Section 8).
+
+   - LNN: The Logical Network Number defines the logical network the
+   packet belongs to. This field in is used in conjunction with the
+   destination node identifier as the VNS switching label (see Section
+   5).
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 5]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   - TTL: The Time To Live field is used to detect and discard packets
+   caught in temporary routing loops.
+
+   - Destination Node Identifier: This field contains an ID which
+   uniquely identifies the destination node.  This ID is unique to  the
+   physical network not just the LN. In conjunction with the LNN, this
+   forms a global VNS switching label.
+
+   - Protocol Type: indicates the type of Network layer protocol being
+   carried in the packet. Examples include IP, IPX, and Bridging. If the
+   packet is a multicast packet then this is indicated in this field.
+
+   - Source Node Identifier: This field contains an ID which uniquely
+   identifies the source node (ingress node).
+
+   - CoS: The Class of Service field is used to provide routing class of
+   service. The COS field also affects the Emission Priority of the
+   packet in the scheduler (see Section 9).
+
+   - Reserved Fields: All the fields marked with "x" are Reserved.
+
+       3                   2                   1                   0
+     1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |      TTL      |      LNN            |x|LS-Key |x|DP | CmnHdr  |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    | PT = Multicast|         Destination Node Identifier           |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |  COS  |x x x x|         Source Node Identifier                |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    | Protocol Type |x x x x x x x x|    Multicast Group            |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |                 Network Layer Header (e.g. IP)                |
+    /                                                               /
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    /                          Data                                 /
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+                      Figure 3. Multicast VNS Header
+
+   The multicast header shown in Figure 3, includes all the fields of
+   the unicast header. In addition, the multicast header includes the
+   following fields:
+
+   - Multicast Group: this field is used to identify a sub-group within
+   the logical network that receives the multicast packets.
+
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 6]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   - Protocol Type: indicates the type of Network layer protocol being
+   carried in the packet. Examples include IP, IPX, and Bridging.
+
+4. VNS Label Distribution
+
+   Label distribution in VNS is based on a distributed serverless
+   topology driven approach. Standard ARP or address gleaning is used to
+   distribute and map network layer addresses to VNS addresses.
+
+   A VNS Label is an 6 byte encoding of the LNN and the node ID.  VNS
+   Labels are treated as MAC addresses by the network layer.  This means
+   that labels are distributed by the same means network layers use to
+   distribute MAC addresses.  Thus, VNS leverages existing L2/L3 mapping
+   techniques and doesn't require a separate Label Distribution
+   Protocol.
+
+5. Logical Networks (LNs)
+
+   A logical network consists of a subset of the nodes in a network
+   together with a subset of the trunking facilities that link those
+   nodes. Logical networks partition the network into subnetworks that
+   serve a subset of the overall topology.
+
+   Each of the logical networks supported on any given node has a
+   separate routing and forwarding table (built by VNS). Therefore,
+   routing decisions are based on the resources available to the logical
+   network, not the entire network.
+
+   Each instance of VNS will discover all the trunks which are connected
+   to neighbors which support a matching LNN.  This provides a huge
+   administrative saving, since VNS provisioning is on a per-node basis,
+   not on a per-link basis.  VNS provisioning requires only a unique
+   node ID and an LNN.  Discovery of which trunks support which LNNs is
+   done at run time, relieving administrative effort, and allowing the
+   LN to dynamically adapt to topology changes.
+
+   Multiple Logical Networks provide the following benefits to the
+   network system:
+
+      - Logical networks allow service providers to service multiple
+      private networks or (Virtual Private Internets) easily over one
+      network.
+
+      - Logical networks can be used to limit the impact of one network
+      layer protocol on the others. This is particularly true for
+      protocols that broadcast or multicast a large percentage of either
+      their control or data packets.  This increases the effective
+      bandwidth of the trunks and allows the overall network to scale
+
+
+
+Jamoussi, et. al.            Informational                      [Page 7]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+      better.
+
+      - Logical networks allow for the configuration of the network to
+      meet individual community of interest and geographical
+      subnetworking needs.
+
+      - Routing control traffic has significance only in the local
+      subnetwork that is isolated to that subnetwork.
+
+      - Logical networks allow different instances of the same protocol
+      to share trunk facilities.
+
+6. VNS Routing
+
+   VNS routing is a link state routing system which uses many concepts
+   similar to OSPF and PNNI. One of the most significant departures from
+   the others is its ability to calculate shortest path trees for
+   routing unicast traffic and spanning trees for routing multicast
+   traffic within a Logical Network.
+
+   There is only one type of interface that VNS routing supports and
+   this is known as a VNS link. A link is a set of trunks that join two
+   VNS neighbor nodes. Each node in a VNS network maintains information
+   about the state of locally attached links. This information is
+   flooded throughout the network whenever there is a significant change
+   to the link's state or attributes (i.e. up/down, speed change,
+   available bandwidth change).
+
+   Each node stores and forwards the link state information received
+   from all other nodes. This allows each node to have the same view of
+   all of the nodes in the network together with all of their link state
+   information. This data is used to compute both the shortest path to
+   reach each node in the Logical Network and a spanning tree for the
+   Logical Network.
+
+   Logical networks are not bound to a particular trunk or link. They
+   are configured on a node. By default, a link will support a specific
+   logical network if the two nodes which it connects both are
+   configured to support the logical network number. This provides a
+   significant savings in operations over having to configure logical
+   networks on links or trunks.
+
+   When a link first comes into service, a protocol is run which allows
+   the two neighboring nodes to exchange information about the logical
+   networks they support. This allows the two nodes to determine if the
+   links are to be considered as a locally attached link for a logical
+   network.
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 8]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+7. VNS Forwarding
+
+   VNS supports two types of forwarding: unicasting and multicasting. In
+   the first type, the data packet arrives on the ingress node and
+   unicasting forwards the data packet to a single destination (egress
+   node). In the second type, the data packet arrives on the ingress
+   node and multicasting forwards the data packet to all other nodes in
+   the logical network.
+
+7.1 Unicast
+
+   When a packet first enters the  LAN internetwork, the network layer
+   routing protocol determines the next hop of the best route for the
+   packet to reach its final destination. If the best route is through a
+   VNS Logical Network, the network layer routing protocol relies on VNS
+   forwarding to get the packet to the egress  node. A VNS packet header
+   containing the node ID (the unique ID assigned  to each  node) of the
+   egress node is added to the front of the packet and VNS forwarding is
+   invoked to deliver the packet. The network layer routing protocol
+   learns the egress node ID through an Address Resolution Protocol
+   (ARP) for IP and Source Address learning for bridging.
+
+   As the packet traverses the LN, routing decisions are made to
+   determine the next hop in the route to reach the destination node ID
+   specified in the VNS header. A forwarding table is built on each node
+   that assists in making the routing decision.
+
+   Each VNS instance on each  node builds and maintains a forwarding
+   table for its LN. Each forwarding table has an entry for every  node
+   that is a member of the logical network.
+
+7.2 Multicast
+
+   In addition to the unicast forwarding function, VNS also supports a
+   multicast forwarding service for traffic within an LN at the VNS
+   layer. Multicast packets are delivered to all nodes supporting the
+   logical network to which the multicast packet belongs. The packets
+   are sent along the branches of a spanning tree that is built by each
+   node supporting the logical network and is based on a common root
+   node (so that each node's view of the tree is the same as other
+   nodes). In other words, multicast packets are sent intelligently,
+   consuming a minimum of network bandwidth. If the network topology is
+   stable, each node receives each multicast packet only once.
+
+   Multicast packets received at any node are not acknowledged. They are
+   simply forwarded to the specified network layer interface and sent to
+   any other neighbor nodes on the spanning tree.
+
+
+
+
+Jamoussi, et. al.            Informational                      [Page 9]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+8. Traffic Engineering
+
+   VNS forwarding supports two types of traffic engineering mechanisms:
+   equal cost multipaths and trunk load spreading.
+
+   Equal cost multipaths allows different streams (unique network layer
+   source and destination address pairings) to be load spread between
+   multiple relatively equal cost paths, through the Logical Network to
+   the egress node.
+
+   Trunk load spreading between two neighbors can take place when
+   multiple VNS  trunks are defined between neighbors. Again, the load
+   spreading is based on network layer streams.
+
+8.1 Equal Cost Multipaths
+
+   From any point in a logical network, there may be multiple paths to
+   reach a specific egress node. If VNS routing determines that more
+   than one of these paths are of equal cost, VNS packets will be load
+   spread between two of them.
+
+   Equal cost multipath forwarding is supported not only on ingress
+   nodes but on tandem nodes as well. Each packet on an ingress node is
+   tagged with an equal cost multipath key. This key is acted upon at
+   the ingress node and stored in the VNS header to be used on tandem
+   nodes.
+
+   The equal cost multipath key is calculated by running an algorithm
+   over the source and destination network layer addresses. This means
+   that, in a stable network, any given stream will always take the same
+   path through a Logical Network avoiding the problems that misordering
+   would otherwise cause.
+
+8.2 Trunk Load Spreading Between Neighbors
+
+   VNS allows multiple trunks to be configured between neighboring VNS
+   nodes. VNS routing considers the aggregate bandwidth of those trunks
+   to determine the metric between the nodes. Also, VNS load spreads its
+   traffic amongst those trunks.
+
+   As is the case with equal cost multipaths, the trunk load spreading
+   key is calculated on the ingress node from an algorithm run over the
+   source and destination network layer addresses. The key is then
+   stored in the VNS header to be used on all tandem nodes through the
+   Logical Network.
+
+
+
+
+
+
+Jamoussi, et. al.            Informational                     [Page 10]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+9. Class of Service
+
+   At the ingress to a VNS Network, packets are classified according to
+   the Class of Service (Cos) policy settings. The CoS differentiation
+   is achieved through different  Emission and Discard priorities. The
+   semantics of the classification is carried in the VNS label (DP and
+   COS Fields described in Section 3) to be used at the ingress node as
+   well as all tandem points in the VNS network to affect queuing and
+   scheduling decisions.
+
+10. VNS Migration Strategies
+
+   VNS supports several upper layer protocols such as IP, IPX, and
+   Bridging. Therefore, it is a multiprotocol label switching
+   architecture. In addition, VNS  is not tied to a particular L2
+   technology. It runs on cell (e.g., ATM) trunks, frame trunks, or a
+   mixture of both.
+
+   VNS can be gradually introduced in a network. It can be implemented
+   between switching elements interconnected by point to point links.
+   Each of the switching nodes can run layer 3 routing simultaneously
+   with packet switching. VNS also allows for the interconnection of VNS
+   clouds through an ATM VC.
+
+   Since VNS can run on a mixture of Frame and Cell trunks, it allows
+   for the graceful migration of the frame links to ATM without
+   requiring a complete immediate overhaul.
+
+11. Summary
+
+   VNS addresses scalability problems in several ways:
+
+      1. By a generally distributed design which doesn't
+         require a Label Distribution Protocol, or servers of any kind.
+      2. By providing an efficient, distributed multicast mechanism.
+      3. By allowing administrators to control the size of a
+         Logical Network, limiting traffic to a subset of the physical
+         topology.
+      4. By reducing layer 3 address space/subnet requirements in the
+         WAN which reduces the routing table size.
+
+   VNS provides redundancy transparent to the network layer protocol by
+   managing the network of trunks independently of the network layer.
+   VNS will automatically discover any topology changes and re-route
+   traffic accordingly.
+
+
+
+
+
+
+Jamoussi, et. al.            Informational                     [Page 11]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+   VNS eases network administration by dynamically keeping track of
+   which trunks are available for each LNN.  Network administrators
+   don't have to configure VNS or network layer addresses on a per link
+   basis.  Network layer addresses only have to be assigned on a per
+   Logical Network basis.  For nodes which will only be tandem VNS
+   nodes, network layer addresses aren't required at all.
+
+   Since VNS traffic is constrained within an LNN, administrators have
+   control of where VNS traffic is allowed to flow.
+
+   Finally, VNS supports switching of several Upper Layer Protocols and
+   supports  several media (cell and Frame) or a mixture thereof.
+   Switching in the core of the WAN removes the need for routers and
+   improves the performance due to a reduction in the  number of fields
+   that need to processed.
+
+12. Security Considerations
+
+   Logical networks provide a means of restricting traffic flow for
+   security purposes. VNS also relies on the inherent security of the L2
+   media such as an ATM Virtual Circuit.
+
+13. Acknowledgments
+
+   The authors would like to acknowledge the valuable comments of Terry
+   Boland, Pierre Cousineau, Robert Eros, Robert Tomkins, and John
+   Whatman.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Jamoussi, et. al.            Informational                     [Page 12]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+14. Authors' Addresses
+
+   Bilel Jamoussi
+   Nortel (Northern Telecom), Ltd.
+   PO Box 3511 Station C
+   Ottawa ON K1Y 4H7
+   Canada
+
+   EMail: jamoussi@Nortel.ca
+
+
+   Dwight Jamieson
+   Nortel (Northern Telecom), Ltd.
+   PO Box 3511 Station C
+   Ottawa ON K1Y 4H7
+   Canada
+
+   EMail: djamies@Nortel.ca
+
+
+   Dan Williston
+   Nortel (Northern Telecom), Ltd.
+   PO Box 3511 Station C
+   Ottawa ON K1Y 4H7
+   Canada
+
+   EMail: danwil@Nortel.ca
+
+
+   Stephen Gabe
+   Nortel (Northern Telecom), Ltd.
+   PO Box 3511 Station C
+   Ottawa ON K1Y 4H7
+   Canada
+
+   EMail: spgabe@Nortel.ca
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Jamoussi, et. al.            Informational                     [Page 13]
+
+RFC 2340        Nortel's Virtual Network Switching (VNS)        May 1998
+
+
+15.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (1998).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
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+Jamoussi, et. al.            Informational                     [Page 14]
+