(12) United States Patent
`Chase et al.
`
`USOO6188671B1
`(10) Patent No.:
`US 6,188,671 B1
`(45) Date of Patent:
`Feb. 13, 2001
`
`(54) TRAFFIC MANAGEMENT FOR FRAME
`RELAY SWITCHED DATASERVICE
`
`5.991,268
`6,023,453
`
`11/1999 Awdeh et al. ........................ 370/232
`2/2000 Ruutu et al. ......................... 370/229
`
`(75) Inventors: Christopher J. Chase, Freehold;
`Stephen L. Holmgren, Little Silver;
`John Babu Medamana, Colts Neck;
`Vikram R. Saksena. Freehold, all of
`N ity . SakSena, Freehold, all O
`
`(73) Assignee: AT&T Corp, New York, NY (US)
`(*) Notice:
`Under 35 U.S.C. 154(b), the term of this
`patent shall be extended for 0 days.
`
`(21) Appl. No.: 08/988,424
`(22) Filed:
`Dec. 10, 1997
`(Under 37 CFR 1.47)
`O
`O
`Related U.S. Application Data
`(60) Provisional application No. 60/051,564, filed on Jul. 3,
`1997.
`(51) Int. Cl." ................................................. H04L 12/28
`(52) U.S. Cl. ........................... 370/232; 370/253; 370/254
`(58) Field of Search ..................................... 370/412, 414,
`370/416, 468,236, 232, 253, 395,429,
`234, 235, 254
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`
`Klessig, Robert W. And Tesink, Kaj. SMDS Wide-Area
`9.
`Data Networking With Switched Multi-megabit Data Ser
`vice. Prentice Hall, pp. 11-20.
`
`* cited by examiner
`
`Primary Examiner-Chi H Pham
`ASSistant Examiner Brenda H. Pham
`(57)
`ABSTRACT
`A new type of data transport Service which uses a frame
`relay layer 2 data link connection identifier (DLCI) to select
`among various Service types, feature Sets, and/or closed user
`groups (CUGs). A layer 3 address may be extracted from a
`layer 2 frame, and the layer 3 address information may be
`used to route a data packet Over a packet-Switched network
`according to the service classes, feature sets, and/or CUGs
`Selected. At the destination, the layer
`ata packet ma
`lected. At the destination, the layer 3 data pack
`y
`again be enclosed in a layer 2 frame with a DLCI indicating
`the Service classes, features Sets, and/or CUGS. Because the
`use of conventional permanent virtual circuits (PVCs) is not
`required in aspects of the invention, new methods of mea
`Suring and managing network traffic are presented.
`
`5,909,443 *
`
`6/1999 Fichou et al. ........................ 370/412
`
`31 Claims, 10 Drawing Sheets
`
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`

`

`U.S. Patent
`
`Feb. 13, 2001
`
`Sheet 1 of 10
`
`US 6,188,671 B1
`
`FIG. 1
`
`END-USER
`LOCATION A
`919-1
`
`
`
`PVCA-c
`
`END-USER
`LOCATION B
`
`USER NETWORK
`INTERFACE B
`
`END-USER
`LOCATION C
`
`END-USER
`LOCATION D
`
`

`

`U.S. Patent
`
`Feb. 13, 2001
`
`US 6,188,671 B1
`
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`U.S. Patent
`
`Feb. 13, 2001
`
`Sheet 3 of 10
`
`US 6,188,671 B1
`
`-
`
`DATA/INFORMATION
`
`FIG. 3
`/ - N
`ISO PROTOCOLLAYER-t
`APPLICATION LAYER-7
`y
`
`TCP
`HEADER
`IP
`H
`
`USER DATA
`
`USER DATA
`
`TRANSPORT LAYER-4
`
`USER DATA
`
`NETWORK LAYER-3
`DATA LINK LAYER-2
`
`PDU
`A. DATA
`O.K.O.: DATARAM CNEL
`FRAMES
`ER
`(FRAME RELAY)
`
`BITS
`
`
`
`PHYSICAL LAYER-1
`
`ensensensensens...elsensets
`FIG. 4
`-\
`2
`FEER INFORMATION FIELD
`- 4-4100 OCTETS
`F = FRAME DELIMITER (FLAG)
`(O1111110 BINARY VALUE)
`HEADER - FR HEADER FIELD
`INFORMATION FIELD
`USER'S PAYLOAD
`FCS
`FRAME CHECK SEQUENCE
`
`0-4096
`
`2
`
`N
`FCSF
`--
`
`FIG. 6
`
`A
`
`FRAME HEADER - 2 OCTETS
`
`V
`
`FECNBECNDEEA
`DLC
`2
`DLCI = DATA LINK CONNECTION IDENTIFIER (10 BITS)
`C/R = COMMAND/RESPONSE (BIT)
`EA = EXTENDED ADDRESS (2 BITS)
`FECN = FORWARD EXPLICIT CONGESTION NOTIFICATION (BIT)
`BECN = BACKWARD EXPLICIT CONGESTION NOTIFICATION (1 BIT)
`DE = DISCARD ELIGIBILITY (1 BIT)
`
`

`

`U.S. Patent
`
`Feb. 13, 2001
`
`Sheet 4 of 10
`
`US 6,188,671 B1
`
`SWITCHED TRAFFIC
`
`|
`SINGLE
`PHYSICAL |
`PORT
`
`
`
`CUSTOMER
`
`
`
`.
`
`.
`
`FIG. 6
`
`POINT TO POINT
`TRAFFIC
`
`
`
`
`
`
`
`COMMITTED DELIVERY RATE:
`GUARANTEED RATE OF COMBINED
`FLOW TO COMMON EGRESS,
`
`

`

`U.S. Patent
`
`Feb. 13, 2001
`
`Sheet 5 of 10
`
`US 6,188,671 B1
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`FIG. 7
`
`END-USER
`LOCATION A
`ROUTER
`(CPE)
`
`402
`
`USER NETWORK
`INTERFACE A
`
`J
`
`500
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`ANDPoint
`ROUTER
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`
`USER NETWORK
`INTERFACE B
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`S SPN
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`402
`
`USER NETWORK
`INTERFACEC
`
`900
`
`919
`
`ROUTER
`RC
`(CPE)
`END-USER
`LOCATION C
`
`SWITCH (D)
`
`ROUTER
`RD
`(CPE)
`END-USER
`LOCATION D
`
`502
`
`919
`
`

`

`U.S. Patent
`US. Patent
`
`Feb. 13, 2001
`Feb. 13, 2001
`
`Sheet 6 of 10
`Sheet 6 0f 10
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`US 6,188,671 B1
`US 6,188,671 B1
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`

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`U.S. Patent
`
`Feb. 13, 2001
`
`Sheet 7 of 10
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`US 6,188,671 B1
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`U.S. Patent
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`Sheet 8 of 10
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`US 6,188,671 B1
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`U.S. Patent
`US. Patent
`
`Feb. 13, 2001
`Feb. 13, 2001
`
`Sheet 9 of 10
`Sheet 9 0f 10
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`US 6,188,671 B1
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`U.S. Patent
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`Feb. 13, 2001
`
`Sheet 10 Of 10
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`US 6,188,671 B1
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`

`1
`TRAFFIC MANAGEMENT FOR FRAME
`RELAY SWITCHED DATASERVICE
`
`US 6,188,671 B1
`
`2
`At the UNI 920, the frame is checked for validity to
`determine if there is a predefined PVC associated with the
`DLCI 912. If so, the frame 914 is then forwarded on that
`PVC through the network along the same path and in the
`same order as other frames with that DLCI, as depicted in
`FIG. 2. The layer 2 frame information remains as the packet
`traverses the frame relay network whether this network is
`actually implemented as a frame relay network or other
`network Such as an ATM network. The frame is carried to its
`destination without any further routing decisions being made
`in the network. The FCS is checked at the egress UNI, and
`if the frame is not corrupted, it is then output to the UNI
`asSociated with the end user.
`As is well known in the art, FIGS. 1-3 provide exemplary
`diagrams of how the frame relay data packets are assembled
`at the various ISO layers using the example of TCP/IP
`protocol transport over a frame relay data link layer. The
`example shows how the user data at the application layer is
`"wrapped' in Succeeding envelopes, making up the PDUs,
`as it passes down the protocol Stack. Specifically, the com
`position of the Header field is expanded for detail and is
`shown in FIG. 5. The data link connection identifier (DLCI)
`field comprises 10 bits spread over the first and Second octet,
`and allows for 1023 possible addresses, of which some are
`reserved for specific uses by the standards. As shown in FIG.
`3, the DLCI is added to the frame relay header according to
`what destination IP address is specified in the IP packet. This
`decision about what DLCI is chosen is made by the CPE,
`uSuually a router, based on configuration information pro
`vided by the customer that provides a mapping of IP
`addresses into the PVCs that connect the current location
`with others across the WAN 900.
`In conventional frame relay, a layer 2 Q.922 frame carries
`the layer 3 customer data packet across the network in a
`permanent virtual circuit (PVC) which is identified by a data
`link connection identifier (DLCI). Thus, the DLCIs are used
`by the customer as addresses that select the proper PVC to
`carry the data to the desired destination. The customer data
`packet is carried across the network transparently and its
`contents is never examined by the network.
`The conventional meshed frame relay network discussed
`above has a number of limitations. For example, every time
`a new end user location is added to the meshed network, a
`new connection is required to be added to every other end
`user location. Consequently, all of the routing tables must be
`updated at every end user location. Thus, a “ripple' effect
`propagates acroSS the entire network whenever there is a
`change in the network topology. For large networks with
`thousands of end user locations, this ripple effect creates a
`large burden on both the network provided to Supply enough
`permanent virtual circuits (PVCs) and on the network cus
`tomers in updating all of their routing tables. Further, most
`routers are limited to peering with a maximum of 10 other
`routers which makes this network topology difficult to
`implement. As networks grow in size, the number of PVCs
`customers need to manage and map to DLCIS increases.
`Further complicating the problem is a trend toward increas
`ing "meshedness” of networks, meaning more Sites are
`directly connected to each other. The result is a growth in the
`number and mesh of PVCs in networks that does not scale
`well with current network technologies.
`A possible Solution for handling large meshed networks is
`to use a virtual private network (VPN) which interconnects
`end user locations using encrypted traffic Sent via "tunnel
`ing” over the internet. However, VPNs are not widely
`supported by internet service providers (ISPs), have erratic
`information rates, and present a number of Security con
`CCS.
`
`The present application claims priority from copending
`provisional application Ser. No. 60/051,564 entitled
`“FRAME RELAY SWITCHED DATASERVICE fled on
`Jul. 3, 1997, herein incorporated by reference, and is related
`by Subject matter to concurrently filed U.S. patent applica
`tion Ser. No. 08/988,159, entitled “FRAME RELAY
`SWITCHED DATASERVICE" by the same inventors.
`BACKGROUND OF THE INVENTION
`1. Technical Field
`The present invention is directed to Systems and methods
`for implementing improved network architectures, and more
`Specifically to Systems and methods for routing internet
`protocol (IP) packets using modified frame relay protocols.
`2. Description of the Related Arts
`Recently, the popularity of large "meshed” networks has
`been increasing. However, large-scale highly-meshed net
`WorkS can be difficult to implement, maintain, and manage
`using conventional network technologies.
`An example of a conventional mesh configuration is
`shown in FIG.1. A wide-area network (WAN) 900 includes
`a plurality of routers RA, Re, Re, Rio, (customer premises
`equipment (CPE)) respectively disposed at a plurality of end
`user locations A, B, C, and D and interconnected to a Service
`provider's network (SPN) 901 via respective user-network
`interfaces (UNI) 920-1, -2, .
`. . , -n. The user-network
`interfaces 920 may be variously configured to be, for
`example, an asynchronous transfer mode (ATM) Switch
`having a frame relay interface to CPE. Connecting the sites
`together are logical paths called, for example, permanent
`Virtual circuits (PVCs) PAC, PA, Pa-o, PA, P., that are
`characterized by their endpoints at the UNIs 920-1,
`920-2, . . . , 920-n and a guaranteed bandwidth called the
`committed information rate (CIR).
`FIG. 2 provides a detailed view of the flow of data across
`the WAN 900. There exists a plurality of layers of protocol
`over which communications may occur. For example, the
`well-known layers of the International Standards Organiza
`tion's (ISO) Open Systems Interconnect Model having lay
`ers from a physical layer (layer 1), a datalink layer (layer 2),
`a network layer (layer 4), up through and including an
`application layer (layer 7). Under this model, user data 902
`is generated by a user application running at the application
`layer 903. At the transport layer (layer 4) 904, a source and
`destination port address 906 (as part of the TCP header
`(layer 4)) may be added to the user data 902. At the network
`layer (layer 3) 905, an additional header (i.e., an IP header
`(layer 3)) containing Source and destination IP addresses)
`908 may be added. Thus, the layer 3 user data field includes
`the layer 4 user data 902 plus the layer 4 header 906. The
`layer 3 protocol data unit (PDU) 902,906,908, which makes
`up, for example, an IP packet 950, is then passed down to
`layer 2 909 in the CPE (routers RA, R, R, R) that
`interfaces to the SPN 901. In the router, a table maps one or
`more IP addresses (layer 3) 908 to an appropriate PVC or
`PVCS (PAC, PA, Pa-o, PA, P). The router table is
`maintained by the customer. Once the correct PVC is located
`in the routing table, the corresponding data link connection
`identifier (DLCI) (layer 2) 912 is coded into the header of
`the frame relay frame 914 (packet). Thereafter, the remain
`der of the frame relay frame is included and a frame check
`sum (FCS) is computed. The frame is then passed down to
`the physical layer and transmitted to the SPN 901.
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`US 6,188,671 B1
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`3
`Another possible Solution is the use of frame relay based
`switched virtual circuits (SVCs). While PVCs (discussed
`above) are usually defined on a Subscription basis and are
`analogous to leased lines, SVCs are temporary, defined on an
`as-needed basis, and are analogous to telephone calls.
`However, SVCs require continuous communications
`between all routers in the system to coordinate the SVCs.
`Further, because the tables mapping IP addresses to SVC
`addresses are typically manually maintained, SVCS are often
`impractical for large highly-meshed networkS. Security is a
`major concern for SVC networks where tables are misman
`aged or the network is spoofed. Further, frame SVCs are
`difficult to interwork with asynchronous transfer mode
`(ATM) SVCs.
`None of the above Solutions adequately address the grow
`ing demand for large mesh networks. Accordingly, there is
`a need for network architectures which enable implementa
`tion of large mesh networks having Security, low mainte
`nance costs, efficient operations, and Scalability.
`
`15
`
`4
`customers because, unlike that of conventional frame relay,
`customers no longer need to update their local DLCI tables
`each time a network customer with whom they wish to
`communicate is added or removed from the network. Thus,
`the customer's burden of network administration is Substan
`tially reduced.
`In sub-aspects of the invention, some DLCIs may be used
`to select among Service categories ("Service category
`DLCIs”) while in the same network other DLCIs may be
`used to select conventional PVCs and/or SVCs
`(“conventional DLCIs). In other words, conventional frame
`relay may be mixed with aspects of the present invention
`within the same network, allowing aspects of the present
`invention to be incrementally implemented in existing con
`ventional frame relay networks.
`In further aspects of the invention, addressing contained
`in multiple layers (e.g., as defined by the Open System
`Interconnection model) are compared with each other in a
`network to determine routing errors. If the addressing in the
`layers are consistent with each other, then the associated data
`is routed without interruption. On the other hand, if the
`addressing in the layerS is inconsistent with each other, the
`asSociated data may be specially handled. For example, the
`data may be discarded, Sent to a pre-determined address,
`and/or returned to the Sender. This address comparison may
`be applied to the Sending address and/or the destination
`address. An advantage of this multiple layer address com
`parison is that network Security is increased. For instance,
`problems Such as “spoofing,” which is the practice of
`purposely providing an incorrect Sending internet protocol
`(IP) address, are better controlled by such a method.
`In Still further aspects of the invention, routing look-up
`tables within the network are separated Such that, for
`example, each customer, closed user group (CUG), extranet,
`and/or intranet may have its own private partition and/or
`Separate table. This can provide greater network Speed
`because a router need not Scan the entire available address
`Space for all network customers at once. Furthermore, data
`Security is improved because the risk of Sending data to a
`wrong recipient is reduced.
`In yet further aspects of the invention, layer 3 and/or layer
`4 IP address information is utilized to route the fast packets
`through the network.
`In even further aspects of the invention, new network
`traffic management techniques and measurements are
`defined. For example, in Some traffic-management aspects of
`the invention, committed delivery rates (CDRs) may be
`assigned to one or more UNIs. A CDR is the average
`minimum data rate that is guaranteed to be delivered to a
`given UNI when sufficient traffic is being sent to the UNI. In
`further traffic-management aspects of the invention, a des
`tination rate share (DRS) is assigned to one or more UNIs.
`The DRS may be used to determine the share of traffic that
`a given UNI may send through the network. If several UNIs
`are simultaneously offering to Send traffic to the same
`destination UNI, then each sending UNI's share of the
`network may be determined by its own DRS and the DRSS
`of the other sending UNIs.
`These and other features of the invention will be apparent
`upon consideration of the following detailed description of
`preferred embodiments. Although the invention has been
`defined using the appended claims, these claims are exem
`plary in that the invention is intended to include the elements
`and Steps described herein in any combination or Subcom
`bination. Accordingly, there are any number of alternative
`combinations for defining the invention, which incorporate
`
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`SUMMARY OF THE INVENTION
`Aspects of the present invention Solve one or more of the
`above-Stated problems and/or provide improved Systems
`and methods for implementing a network architecture.
`A new type of data transport Service takes advantage of
`the existing base of frame relay customer premises equip
`ment (CPE) and customers while offering a new mechanism
`for providing extensible Service features to those customers.
`In the new service, data link connection identifiers (DLCIs)
`may be used by the CPE to Select among Service types,
`feature sets, and closed user groups (CUGs). The DLCI is
`used in the layer 2 frame that conveys the user data to the
`network. The layer 3 user data packet is extracted from the
`layer 2 frame and the layer 3 address information for the
`(routable) protocol is used to route the user data packet over
`a high-performance packet Switched network, according to
`the service class/feature set selected by the DLCI. At the
`destination, the layer 3 data packet is again enclosed in a
`layer 2 frame with a DLCI that indicates to which service
`group it belongs. The frame is then forwarded to the CPE.
`Use of this technique will allow the existing frame relay
`CPE to Support, Over the same physical interface, conven
`tional frame relay service with a range of DLCIs that are
`linked to logical paths. Such as permanent Virtual circuit
`(PVCs), as well as a range of DLCIs that are linked to
`Service and/or feature sets. This will allow a robust method
`for extension of new Services to the frame relay installed
`base, with minimal impact to existing customer equipment.
`In Some aspects of the invention, frame relay DLCIS are
`used for Selecting among various “Service categories.” This
`differS Significantly from conventional frame relay, which
`uses DLCIs only to select PVCs and/or switched virtual
`circuits (SVCs). Service categories may include, but are not
`limited to, communication via the public internet, commu
`55
`nication via a local intranet, communication within a closed
`user group (CUG), communication with an extranet (e.g., a
`network of trusted Suppliers or corporate trading partners),
`live audio/video transmission, multicasting, telephony over
`internet protocol (IP), or any combination thereof. Thus, the
`concept of a frame relay PVC is significantly expanded by
`aspects of the present invention. For example, the location of
`an intended network endpoint recipient is not necessarily
`determined by a DLCI at a sending network endpoint. The
`DLCI may represent a Service category with the intended
`recipient indicated by an IP address within the frame relay
`packet. This results in a Significant benefit to network
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`S
`one or more elements from the Specification, including the
`description, claims, and drawings, in various combinations
`or Subcombinations. It will be apparent to those skilled in
`network theory and design, in light of the present
`Specification, that alternate combinations of aspects of the
`invention, either alone or in combination with one or more
`elements or Steps defined herein, may be utilized as modi
`fications or alterations of the invention or as part of the
`invention. It is intended that the written description of the
`invention contained herein covers all Such modifications and
`alterations.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The foregoing Summary of the invention, as well as the
`following detailed description of preferred embodiments, is
`better understood when read in connection with the accom
`panying drawings. For the purpose of illustration, embodi
`ments showing one or more aspects of the invention are
`shown in the drawings. These exemplary embodiments,
`however, are not intended to limit the invention solely
`thereto.
`FIG. 1 illustrates a wide area network (WAN) having
`routers as CPES and PVCs between customer locations.
`FIG. 2 shows data flow through the WAN shown in FIG.
`1.
`FIGS. 3-5 show the construction and flow of data packets
`through the network.
`FIG. 6 shows a block diagram of a network architecture
`in accordance with aspects of the present invention.
`FIG. 7 shows a detailed block diagram of the network
`illustrated in FIG. 6.
`FIGS. 8A-8B shows a migration path for incorporating
`aspects of the invention into convention network architec
`tureS.
`FIG. 9 shows data flow through the network architecture
`of FIG. 6.
`FIG. 10 shows application based prioritization through
`the network architecture of FIG. 6.
`FIG. 11 illustrates an exemplary embodiment of a means
`to apportion services through the network of FIG. 6.
`FIGS. 12-14 illustrate data flow through exemplary
`WANS 1.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`Exemplary embodiments of the present invention allow
`the large installed base of frame relay customer premises
`equipment (CPE) to be maintained by using the same
`interface in a different way to deliver new sets of services
`and features to the customer. For example, the data link
`connection identifier (DLCI) known from the frame relay
`protocol may be used to Select among Several virtual private
`networks with differing address Spaces, feature Sets, and/or
`conventional permanent virtual circuits (PVCs).
`Referring to FIG. 7, a block diagram of a wide area
`network (WAN) 1 incorporating aspects of the present
`invention is shown. The WAN 1 includes a plurality of
`customer premise equipment (CPE) System, for example
`routers located at each of the end user locations and inter
`connected via one or more Service provider's networks
`(SPNs) 500. The SPN 500 is typically connected to a
`plurality of endpoint routers 919 via a plurality of corre
`sponding user network interfaces (UNIs) 402 and/or one or
`more internet protocol (IP) switches 502. The IP switches
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`502, UNIs 402, and/or routers/switches 501 may be inter
`connected So as to form a meshed network (e.g., a partial or
`fully meshed network). Additionally, the wide area network
`(WAN) 1 may contain any number of IP switches 502
`located within the WAN 1 Such that it is not connected
`directly to any endpoint routers 919, and/or one or more IP
`Switches 502 may be located at an interface between the
`SPN 500 and an endpoint router 919. In further embodi
`ments of the invention, there may be multiple endpoint
`routers 919 associated with a UNI 402/IP switch 502 and/or
`multiple UNIs 402/IP switches 502 associated with an
`endpoint router 919.
`The network architecture of the WAN 1 allows the num
`ber of IPSwitches to increase as customers are transitioned
`to the new service. For example, as shown in FIG. 8A,
`initially there may be only a small number (e.g., one, two,
`three, etc.) of IP switches installed in the system. Where only
`a small number of IPSwitches are included in the network,
`traffic originating from non-IP enabled UNIs 402 (e.g., UNI
`A) may be routed to an IP switch 502 elsewhere in the
`network. Although this creates Some negligible inefficien
`cies in “backtracking it nonetheless allows a migration path
`to the new network architecture without Simultaneously
`replacing all routers 501. However, as more and more users
`are transitioned to the new network architecture of WAN 1,
`more and more IP switches can be added (FIG. 8B) to
`accommodate the increased load. In many embodiments, it
`may be desirable to eventually convert each UNI 402 to an
`IP switch 502 such that IP routing may be accomplished at
`the edge of the network.
`In some embodiments, the WAN 1 may include a com
`bination of conventional network Switches and/or routers
`501 in addition to IP switches 502. On the other hand, every
`switch in the SPN 500 may be an IP switch 502.
`Alternatively, the WAN 1 may contain only a single IP
`switch 502. The IP switches 502 may be variously config
`ured to include a Suitable multi-layer routing Switch Such as
`a Tag Switch from Cisco. Multilayer routing Switches may
`also be utilized from vendors such as Ipsilon, Toshiba, IBM,
`and/or Telecom. IP switches are currently being developed
`to replace endpoint routerS So that customer premise equip
`ment (e.g., Ethernet local area network (LAN) equipment)
`can connect directly to an asynchronous transfer mode
`(ATM) network. Aspects of the present invention propose
`using IPSwitches in a different manner to maintain the huge
`installed base of customer premise equipment while avoid
`ing the limitations of previous Systems. Accordingly, the IP
`Switches in accordance with embodiments of the invention
`are disposed within the SPN 500 and modified to provide
`Suitable routing and interface functions.
`In Some embodiments of the invention, an IPSwitch 502
`acts as a multi-layer Switch. For example, an IP switch 502
`may receive ATM cells, Switching some or all of the ATM
`cells based upon the content of IP packets encapsulated
`within the ATM cells. Thus, IP addressing may be used by
`an IP switch 502 to determine an ATM virtual path for
`sending ATM cells to a destination UNI 402. In further
`embodiments of the invention, higher layer addressing (e.g.,
`transmission control program (TCP) logical ports at layer 4)
`may also be used by an IPSwitch 502 as a basis for Switching
`ATM cells to provide a path through the SPN 500. In still
`further embodiments of the invention, an IPSwitch 502 uses
`IP addresses and/or TCP logical ports to make quality of
`service (QOS) decisions.
`In further embodiments of the invention, an endpoint
`router 919 may encapsulate one or more IP packets in frame
`relay frame 914. In this event, the frame relay frames may
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`US 6,188,671 B1
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`be transmitted between an endpoint router 919 and a corre
`sponding UNI 402 and/or IP switch 502. The endpoint router
`919 encapsulates IP packets 950 with frame relay frames
`914. Further, the endpoint router 919 may set the DLCI of
`each frame relay frame 914 according to a particular Service
`category (if a Service category DLCI is used) that the user
`has Selected. For example, the various Service categories
`may include the public internet, communication via a local
`intranet, communication within a closed user group (CUG),
`communication with an extranet (e.g., a network of trusted
`Suppliers or corporate trading partners), live audio/video
`transmission, multicasting, telephony over internet protocol
`(IP), or any combination thereof. Thus, the concept of a
`frame relay PVC is significantly expanded by aspects of the
`present invention. For example, the location of an intended
`network endpoint recipient is not necessarily determined by
`a DLCI at the endpoint routers 919.
`In further embodiments of the invention, a UNI 402 may
`receive frame relay frames 914 from an endpoint router 919
`and divides and encapsulates frame relay frames into, for
`example, smaller fixed-length ATM cells. The UNI 402 may
`further translates the frame relay DLCI into an ATM address
`(e.g., a virtual path identifier/virtual channel identifier (VPI/
`VCI)). There are various methods which may be used to
`translate DLCIs to VPI/VCIs. For example, the Network
`Interworking Standard as defined in Implementation Agree
`ment #5 of the Frame Relay Forum, and/or the Service
`Interworking Standard as defined in Implementation Agree
`ment #8 of the Frame Relay Forum may be utilized. An ATM
`address associated with a Service category DLCIS defines an
`ATM virtual path via network routers to an IP switch 502.
`Thus, ATM data associated with a service category DLCI is
`ultimately sent to an IP switch 502. However, ATM data
`asSociated with a conventional DLCI may or may not be sent
`to an IP switch 502 and may be routed through the network
`without passing through an IP switch 502. Thus, both
`translated IP data and conventional PVC data may be present
`in the SPN 500 and/or WAN 1.
`In further embodiments of the invention, a UNI 402
`and/or a network router 501 may send data to a predeter
`mined IP Switch 502. In even further embodiments of the
`invention, a UNI 402 and/or a network router 501 selects
`which IPSwitch 502 to send data to based upon an algorithm
`(e.g., based on network traffic flows, the relative distance/
`location of an IP switch 502, the type of data being sent,
`and/or the Service category Selected). In still further embodi
`ments of the invention, a UNI 402, network router 501,
`and/or IP switch 502 may send the same data to more than
`one UNI 402, network router 501, and/or IP switch 502,
`depending upon, for example, a Service category or catego
`CS.
`In further embodiments of the invention, a UNI 402, an IP
`Switch 502, and/or a network router 501 compares an ATM
`VPI/VCI 303-305 address with an IP address for the same
`data. If the two addresses are inconsistent, then the ATM cell
`may be discarded, Sent to a predetermined address, and/or
`returned to the Sending location. In even further embodi
`ments of the invention, layers above the layer 3 IPlayer may
`be used for address and/or Service class generation/
`discrimination. For example layer 4 of the ISO addressing
`Scheme and/or other application level data may be utilized to
`determine particular Service classes.
`Referring specifically to FIG. 9, the path of user data
`flowing through an exemplary WAN 1 is shown. As in the
`frame relay case, user data at the application layer and layer
`4 requires the addition of a layer 3 network address header.
`In the CPE a decision is made based on information in layers
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`3 and 4 about which virtual private network (VPN), service
`class, or conventional PVC the packet should be routed to.
`Thus, a packet with layer 4 information indicating it is a
`telnet (interactive) application and layer 3 information that
`it is an internal company address might go to VPN A for a
`low-delay intranet class of Service. Another packet that is
`part of a file transfer protocol (FTP) file transfer might go to
`VPNB with a lower service class, and a third packet going
`between two heavily utilized applications might go on a
`dedicated PVC D. These decisions are coded as different
`DLCI values, inserted in the layer 2 frame, and sent into the
`UNI.
`At the UNIA402, the Switching based on the DLCI takes
`place. The packet may be routed to IP switch 502 in the
`center of the SPN 500. The first packet has its layer 2 frame
`stripped off as it is forwarded to VPN A. Within VPNA, the
`layer 3 address is now used to make routing decisions that
`send the packet to its destination UNI. Thus, no PVC need
`be established ahead of time for that path, and conventional
`routing methods and protocols can be used, as well as newer
`“short-cut” routing techniques. This permits VPN A to
`provide a high “mesh' of connectivity between sites without
`requiring the customer to configure and maintain the "mesh'
`as a large number of PVCs. The packet forwarded to VPN
`B is treated similarly except that VPN B is implemented
`with a lower Service class (e.g. higher delay). Finally, the
`packet forwarded to PVCD has its layer 2 frame intact and
`passes through the network as a conventional frame relay
`frame. This allows customers to maintain their current
`connectivity of PVCs for their