SVS/SPVC with L3 IP forwarding

The present invention relates to digital communications using a multi-service switching architecture, more specifically to transport layer 3 (layer-3, L3) IP traffic across SVC or SPVC and to make these connections using the ATM signaling protocol. Regarding the system and method to set.

Conventional switching architectures in digital communication networks generally use data link (Layer 2) services. ATM packet switching technology uses virtual connections to complete end-to-end communication over ATM networks. The types of virtual connections are permanent virtual connection (PVC), switched virtual connection (SVC), or soft permanent virtual. connection, SPVC) is included. The SVC transport packets and each packet over the network contain routing and addressing information. These packets pass through a network that shares a predetermined route with packets from other messages. A permanent virtual circuit is a circuit in which terminals are permanently coupled via a virtual circuit. SPVC uses PVC-type connections from the edge of the network to the end user, and SVC-type switching within the network.

FIG. 1 shows SPVC12, which allows user traffic to flow between two ATM switches 14 and 16 over a conventional ATM network 17. SPVC12 has two endpoints 18 and 20 (indicated by black dots in the figure, respectively) at the edge of the network. Each SPVC endpoint terminates on a port that provides direct connectivity from its ATM switch to the CPE. From the point of view of the source node (switch 14), the endpoint 18 is internally cross-connected 15 to the exit port 22 where the SPVC 12 leaves the node. From the point of view of the destination node (switch 16), the endpoint 20 is internally cross-connected 19 to the entry port 24 where the SPVC12 call enters the node. The rest of SPVC12 is shown as a dashed line through the ATM network cloud 17. SPVCs are configured between ATM switches using ATM signal transmission protocols such as the PNNI (Private Network Network Interface) protocol.

Figure 2 shows an exemplary DSL (Digital Subscriber Line) application according to the prior art. In this example, the end user's computer 32 is connected to three separate IP services via an ATM switch 45, an ATM network 34, and a device to be combined. These separate services are network games provided by game server 36, video on demand provided via application server 38, and internet access provided via broadband remote access server (BRAS) 40. Dedicated SPVC connections (SPVC1, SPVC2, and SPVC3) exist for each of these services. Each SPVC connection has an endpoint at the entry port of a DSL access multiplexer (DSLAM) 42 and another endpoint at the IP interface of the far-end ATM switch 50. At the far-end ATM switch 50, each SPVC has an internal interconnect that connects its combined IP interface to the switch's inlet port 52. The user's computer 32 is connected to the DSLAM 42 via the CPE modem 43. For each SPVC, there is a PVC connection between the user's computer and the exit port of the CPE modem. The corresponding SPVC and PVC pairs share the same VPI / VCI (Virtual Path Identifier / Virtual Circuit Identifier) to create a connection between the CPE modem and the DSLAM.

Figure 3 shows a prior art SVC application that uses SPVC and is substantially identical to Figure 1. The connection begins at CPE70, which is connected to switch 72, and ends at ISP server 74, which is connected to switch 76. SVC78 is shown as a dotted line through ATM network 80. Switches 72 and 76 have internal cross connections 73 and 77, respectively.

A problem with the prior art, especially with the example application shown in Figure 2, is that it leads to a large number of PVC and SPVC connections. PVC and SPVC resources are limited and therefore it is desirable to use these resources as efficiently as possible. In fact, the problem sometimes reached the PVC limit on CPE modems. In addition, SPVC limitations on network nodes have become an issue, as a large number of users, and the services they subscribe to, have grown in so many such applications. In addition, it is desirable to minimize the total number of connections in setting up and maintaining such connections, for example by making effective use of existing connections in response to network failures.

Another problem with the prior art shown in Figure 3 is that the SVC only provides connectivity for a single connection between CPE devices. If multiple services are requested from different CPE devices (possibly with different IP addresses) on the same node, then multiple SVCs are requested from the source CPE when a single SVC can be sufficient. Ru.

<p> The present invention uses ATM signaling protocols such as the PNNI protocol and enhances SVC or SPVC signaling messages to dynamically establish virtual IP links over the ATM network, Layer 3 across the ATM network cloud. Describe a new solution to carry traffic (eg IP traffic). Other ATM signal transmission protocols include AINI, UNI, and IISP.</p>

<p> According to a first aspect of the invention, a method of establishing a connection in a communication system is provided, the system having a first endpoint having Layer 3 transfer capability in a first multi-service network node, the method. Is a) The system includes a step of establishing a second endpoint with a second multi-service network node. b) Including the step of establishing a connection between the first multi-service network node and the second multi-service network node via any intervening network node. As a result, the first endpoint is assigned address information, and the address information is added to the forwarding information of the first multi-service network node.</p><p> The present invention will be described in more detail with reference to the accompanying drawings.</p>

An object of the present invention is to establish connectivity between independent routing processes performed on the switch at the source and network destinations such as allowing direct exchange of routing information between them. And to establish reachability between subnets attached to them. The most important connectivity is that it is offered across the underlying L2ATM network in a transparent way that establishes connectivity over time, and the switch follows the path of the L2 virtual connection. Regardless of the number of intermediate ATM switches, they are assumed to be the next hop routers to each other.

The present invention introduces some enhancements to standard ATM SPVC / SVC signal transmission messages (hereinafter sometimes referred to as L3-SPVC signal transmission or L3-SVC) and L3IP on a second multi-service switch. Allows the routing process to establish peer relationships with other L3IP routing processes on the second multiservice switch and exchange routing information, as well as through the underlying Layer 2 virtual connection. Allows transparent flow. For the routing process on both switches, the virtual connection endpoint (hence the name L3-SPVC endpoint) of the other IP interface (virtual IP interface) through which the IP flow can pass. Is processed as.

The ability to establish peer relationships through the underlying ATM network creates a number of applicable scenarios for the present invention. Some of them are: 1. From a public perspective, subnets allow you to connect to public services, such as public networks that provide Internet access. 2. From a private point of view, it allows a subnet to join a virtual private network (VPN) and communicate with a second subnet contained in the VPN. 3. From a semi-private perspective, it provides reachability between the subnet contained in the VPN and the second subnet contained in the second VPN (ie extranet).

From a normal IP routing perspective, establishing a peer relationship between routing processes on a switch is another configuration in which each endpoint has the appropriate IP address to assume the other IP address. The routing process needs to be addressed to the L3-SPVC endpoint so that the IP interface is the next hop interface. The routing process on both switches then exchanges routing information through its (virtual IP) interface. To establish the required connectivity between these two virtual IP interfaces on both ends (via L2VC), the network management system should initiate the signaling process on the L3-SPVC endpoint. It can be used to configure either. L3-SPVC signaling messages require certain extensions (or additions) to the information elements (IE) carried in standard SPVC signaling messages. Therefore, the necessary extensions to standard SPVC messages and the methods of those messages are processed at both ends of the L3-SPVC connection, which represents an important aspect of the invention.

The additional IE required in the associated L3-SPVC signaling message can include any combination of: -IP address of the virtual IP interface on the calling side -IP address of the virtual IP interface on the terminal side · Outgoing node L3-SPVC endpoint identifier · L3-SPVC endpoint identifier of the terminating node -Route specification process id of the outgoing node -Route specification process id of the terminal node -Other statically configured IP address information

Any other IE that can be included in the signal transmission messages exchanged during the L3-SPVC configuration includes, but is not limited to: VPN address Credit information regarding confirmation and certification -Parameters related to negotiation with IP routing protocols and policies Exchangeability information -Transfer table identifier

A particular implementation of the details of the L3-SPVC signaling process is which information is available from the management station 130 to each multi-service switch, as shown in Figure 4, and which combination of additional messages It should be noted to determine if it needs to be exchanged during the signaling process. For example, a particular implementation scenario can preconfigure both endpoints of L3-SPVC with the appropriate IP address, then the IP address of the outgoing virtual IP interface and the IP of the destination virtual IP interface in the configuration message. It can have one end of an L3-SPVC endpoint that initiates signal transmission, including only the address. On the terminating node side, establishing an L3-SPVC then requires creating an end-to-end virtual IP link via the underlying VC for mapping SPVC endpoints to the appropriate virtual IP interface and therefore exchanging IP packets. There is.

Any combination of additional IEs suggested above includes SPVCs such as service category (CBR, rtVBR, nrtVBR, UBR, or ABR), L2 resource features for connectivity such as bandwidth, delay, jitter, cell loss ratio, etc. Added to standard IE, which is normally carried in signaling messages.

It is also assumed that the implementation of the routing process allows the configuration of routing policies such as security policies (eg access control lists) that determine the flow in which the network should be mapped to a given L3-SPVC connection. To. Implicit features commonly supported in routing include the ability to allow multiplexing of flows entering through different interfaces of the same departure interface, and the aggregated flow from incoming interfaces of different departure interfaces. The ability to demultiplex. L3-SPVC endpoint processing as a virtual IP interface fully supports such routing policies such as 1-1 mapping, 1-N mapping, N-1 mapping, and NN mapping. In addition, L3-SPVC offers additional benefits such as guaranteed QoS, transparent and automatic rerouting capabilities that do not affect the forwarding table, and the ability to modify resources allocated to the ATM layer on the fly. To do.

FIG. 4 shows a novel type of ATM connection according to the present invention. The type of connection is hereafter referred to as L3-SPVC (or in some cases L3-SVC). This type of connection uses the capabilities of multi-service, especially ATM / IP, multi-service switching / routing platforms. The connection differs from a traditional SPVC connection in that at least one of its endpoints is what is hereafter referred to as the L3 transfer endpoint. Such an endpoint is the entry port of the "destination" multiservice switch (or the exit port of the "sourcing" multiservice switch), or one assigned or signaled by its location. Characterized by having multiple IP addresses or by its use of L3 IP forwarding to route IP packets between its entry port and the IP interface at the other exit port of the switch. FIG. 4 shows an L3-SPVC connection 101 connecting two multi-service switches via an ATM network 114. The connection in the figure has two L3 transfer endpoints. In FIG. 4, the multi-service switch 102 has an SPVC endpoint 104 at the exit port 106 and an IP interface 108 at the inlet port 110. In FIG. 4, reference numeral 105 indicates the ability to forward IP packets from IP interface 108 to endpoint 104 and vice versa across the multiservice switch fabric. In fact, IP interfaces 108, etc. that can forward packets towards the L3 endpoint 104 via a multi-service switching fabric and vice versa can be multiplexed. Similarly, the multi-service switch 112 on the other side of the ATM network 114 has an SPVC endpoint 116 at ingress port 118 and an IP interface 120 at exit port 122. Reference numeral 124 in FIG. 4 also refers to the multi-service switch 1 Shows the ability to forward IP packets across 12. It can be seen that in a further embodiment of the invention, switch 102 or switch 112 has the L3IP transfer function and the others do not.

Figure 5 illustrates the same concept shown in Figure 2 as an exemplary application of a possible DSL service. However, in this case, the L3-SPVC connection is used instead. The L3-SPVC replaces the dedicated SPVC for each IP interface in the previous example, thereby reducing the number of connections in the network and on the switch. L3-SPVC is used to carry combined traffic for IP services, thus using network and switch connectivity resources more efficiently.

As shown in FIG. 5, the L3-SPVC in a DSL application has multi-service switches 202 and 204 at the opposite end of the ATM network 206. In FIG. 5, it is understood that only switch 204 has L3IP forwarding, but both switches can have this capability. Figure 5 also shows an L3-3 PVC connection, but the application can also have an L3SVC connection. The L3 IP transfer feature allows the SPVC endpoint 208 to communicate independently with separate applications 210, 212, 214 over the IP interface. At the user end, switch 202 is connected to multiple workstations via DSLAM216 and CPE modem 218. Some computers on the LAN are connected to the IP service via L3-SPVC. Therefore, the L3-SPVC configuration request contains the IP address of the computer, and the IP forwarding table at the far-end ATM switch is updated with these addresses when the L3-SPVC connection is made.

L3-SPVC connections can be established in two ways. That is, 1) By configuring the L3-SPVC endpoint on the destination and / or source switch with the appropriate IP addressing information, or 2) By configuring L3-SPVC in response to a new type of connection request, an L3-SPVC configuration request that contains IP addressing information for the user's computer or other device. If the IP address information is dynamically assigned, the L3-SPVC configuration request can be initiated with the dynamically configured information. If the L3-SPVC connection already exists and the IP addressing information has not changed yet, this information can be signaled to the destination node with a connection correction request and the L3 forwarding information disconnects. It will be fixed without.

The following summarizes the different types of messages supported by L3-SPVC (SVC), as indicated by the present invention. ·Configuration. This message is sent during the initial configuration of L3-SPVC. This type of message is also supported by standard SPVC configuration messages, with the exception of the additional IE needed to configure this type of connection. -Connection. This message is used to inform you of successful allocation of L3-SPVC resources along the configuration path. This is also supported by standard SPVC messages, with the exception of additional IE if needed. -Reachability. This message is used to indicate reachability. This is a new signaling message, as defined by the present invention. Inclusion. The reachability message indicates the currently reachable network. In addition, the newly added network (or interface) whose traffic is being collected on an existing L3-SPVC is reachable to indicate it in the forwarding table at the opposite end of the L3-SPVC. It may be necessary to send a message. Cancellation. The reachability message indicates a network that is no longer reachable and should be revoked from the forwarding table. If the transfer table to be joined does not have a reachable network within the transfer table for a given period of time to store network resources, the L3-SPVC can be automatically destroyed. .. This type of message can also be used to carry BGP, OSPF, or ISIS routing information, if desired. -Corrected. This type of message is used for requests to modify resources already allocated to a given L3-SPVC. The type of modification message can indicate that new users are increased or decreased depending on whether they are added or canceled.

For example, there are many other applications where L3-SPVC and L3-SVC can be used in connections between nodes within the core of a network to provide a dedicated IP tunnel within an ATM network. This concept is similar to MPLS LSP (label switching path) in a network with MPLS implemented in the core.

In general, the present invention provides tools that allow a multi-service switch to provide L3IP transfer capability across L2SPVC and SVC connections.

The present invention provides an easier way to carry IP packets across an ATM network.

The present invention provides more effective use of connection resources in CPE devices such as networks and DSL modems. This makes it easier to provide, improves scalability, and makes service applications less constrained by connection resources.

The present invention provides the ability to change the L3IP transfer information in a connection without the need to disconnect and reestablish the connection.

The present invention provides equivalent alternatives to other technologies that require QoS because of the unique QOS features and capabilities currently available using ATM connections in existing networks.

With minor changes to the current signal transmission specifications to handle L3-SVC and L3-SPVC signal transmission information, SVC and SPVC connections are for VCs that include all the advantages of using SVC or SPVC for multi-service switches. It can be enhanced to provide capability for forwarded IP packets. In this way, it provides excellent QOS for IP information flow. As IP-related QoS concerns are currently receiving widespread attention, alternative solutions to solve these problems can have widespread interest and applicability.

Although specific embodiments of the invention have been described and shown, it will be apparent to those skilled in the art that many modifications can be made without departing from the basic concepts of the invention. However, it is understood that such modifications are entirely within the scope of the invention as defined by the claims.

<figref num="1">Shown is a prior art ATM network that carries SPVC connections.</figref><figref num="2">The prior art DSL service application is shown.</figref><figref num="3">Shown is a prior art SVC application.</figref><figref num="4">The Layer 3 SPVC application according to the present invention is shown.</figref><figref num="5">The layer 3 SPVC in the DSL application according to the present invention is shown.</figref>

Code description

12 SPVC 14, 16, 45, 50 ATM switches 15, 19, 73, 77 cross connection 17, 34, 80, 114, 206 ATM networks 18, 20 endpoints 22, 106, 122 exit ports 24, 52, 110, 118 entrance ports 32 computer 36 game server 38 Application server 40 Broadband remote access server 42, 216 DSL access multiplexer 43,218 CPE modem 72, 76 switches 70 CPE 74 ISP server 78 SVC 101 L3-SPVC connection 102, 112, 202, 204 multi-service switch 104, 116, 208 SPVC endpoints 108, 120 IP interface 130 management station 210, 212, 214 applications