MXPA00004921A - Internet protocol (ip) class-of-service routing technique - Google Patents

Abstract

The priority of the flow of packets representing calls or other connection requests within a packet network (10) is determined from the Class-of-Service of the call. Upon receipt of a call, a recipient router (121, 122, 123) identifies available paths, typically by exchanging messages with the other routers in the network. After selecting the path, the recipient router or centralized bandwidth broker determines whether the links comprising the selected path have available bandwidth for the class of service of the call. If so, the router routes the call to the next hop along the path. Otherwise, the router selects another path(s) and checks whether the links on the path possess sufficient bandwidth for the class of service of the call.

Description

RUTEO TECHNIQUE FOR PROTOCOL The present invention relates to a technique for routing calls or other type of connection requirement in a network with IP.

BACKGROUND OF THE INVENTION Traditional telecommunications networks typically use dedicated circuits to carry telephone traffic between facilities. In such traditional networks, the switching systems, such as the 4ESS switching systems used by AT & T, route the calls by establishing a circuit that is active for the entire duration of the call and subsequently deactivating said circuit. For this reason, such traditional networks are commonly referred to as networks of "switching circuits".

The increase in traffic and restrictions in the capacity of existing switches in such networks of switching circuits has driven the development of networks based on information packets, and in particular, networks with REF .: 33133 * t T ^ "^" ~ Internet Protocol (IP) ^^^^^ e typical with IP employs a plurality of routers, such as those manufactured by Cisco, Ascend Communications, Bay Networks and Newbridge, among others, to route data packets representing a call or another connection regardless of the origin to the destination based on a destination address in each packet. Currently, IP networks of the type described above are characterized by the routing of the best effort. In other words, routing, and particularly, route selection, generally occurs regardless of the criterion of the service class. Today, examples of the most prevalent routing techniques in networks with IP are the protocol of the Shortest First Route (OSPF) and the Limit Gate Protocol (BGP). In the OSPF protocol, for example, the routers in the network exchange information with each other by means of a flooding technique in such a way that each maintains a database of the type of the network. When using the information in its stored database, each router selects a route for each packet according to the cost metric established by the user that typically requires the shortest route possible. Using such a cost metric, consequently each router establishes its routing table so that each router can select a route that has, for example, a minimum of links.

Traditionally, telecommunications service providers have offered different grades or classes of service based on consumer demand. To meet quality objectives for such different degrees of service, telecommunications providers, such as AT &T, have employed routing techniques by Class of Service in traditional circuit-switched networks. U.S. Patent 5,392,344, published in the name of Gerald R. Ash et al., On February 21, 1995, and assigned to AT & T (incorporated herein by reference) describes and claims such a Class of Service routing technique. Unfortunately, the Class of Service routing does not exist in the current IP telecommunications networks. Therefore, there is a need for a routing technique with Internet Protocol I IP) per Class of Service.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the present invention provides a technique for routing a call or other connection requirement between a source and destination in an IP network comprised of routers connected by links that transmit data packets between routers. In accordance with the invention, the routers exchange status messages to identify available routes between the origin and destination. Each route includes at least one outbound link to another. First, the class -of "call service or other connection requirement is determined. Then the route that has a minimum cost is selected, such as, and example, a minimum number of connections. Subsequently, a check is made by the originating router or possibly a centralized bandwidth corridor, based on the flood status information of the network, of the selected route to check if the links of that router that form the route have an available depth (that is, bandwidth capacity not reserved for other services) for the service case determined. If the link has the bandwidth requirement, the router routes the packet on the outbound link. Otherwise, another route is selected and the step is repeated to »determine if the route formation links have the depth requirement. After the permitted route is found, the IP packets are treated according to their assigned class of service priority in the queue discipline used by the routers on the route.

BRIEF SUMMARY OF THE DRAWINGS FIGURE 1 illustrates a schematic block diagram for practicing the Class of Service routing technique for IP.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a schematic block diagram of an IP network 10 comprising a plurality of routed, exemplified by routers 12 ?, 122, and 123. The links 14, 14, and 143 connect the "pairs of routers 12 ^ -122, 122- 123, and 121-123, respectively, therefore allowing the routers pass data packets, representing telephone calls, or other information between them. Although the network mode illustrated-10 includes only the three routers 121-123 and three pairs of connector links, the network can include a very large number of routers and interconnection links.

The voice traffic intended to transit through the network 10 enters and leaves the network via at least one, and preferably, a plurality of voice / IP gates, exemplified by the voice gates / IP 15, 152 and 15-. In the illustrated mode, the voice gate / IP 15. handles the Digital Network Traffic of Narrow Band Integrated Services (NISDN), for example, traffic transmitted in blocks of 64 kilobit per second. Voice Gate / IP 152 handles Digital Network Traffic (BISDN), for example, the trw jf that exceeds 144 kilobits per second, the basic transmission rate for NISDN traffic. Such BISDN traffic may include, for example, voice, video and voice data / IP 153 handles data already in an IP format. Depending on the nature of the traffic, the network 10 may include Voice / IP gateways (not shown) each designated for a particular format.

Traditionally, routers 12, 122, and 12 have used a best-effort route policy to route traffic on network 10, using algorithms such as the Shortest First Route Open (OSPF) algorithm that seeks to route each package on the shortest route possible. Currently, the OSPF routing protocol could theoretically support different Service Types (TOS) based on the following criteria: Delay, Processing Flow and Reliability. However, IP networks, such as network 10, which uses OSPF routing, have not offered Class of Service (COS) that has been available in switching circuit networks, making it difficult for telecommunications companies to offer different kinds of services. service using an IP network.

The present invention provides a technique for achieving COS routing in an IP network. In determining the class of service, which includes the priority and other parameters of the call or other connection at its initial startup, an originating router that receives packets from one of the 15 gates. 152 and 153 select a route based on the requirement of the depth (bandwidth required), which in turn is based on the flow priority and load status of the links (14, 142, 143) in the network 10. Once the originating router selects a permissible route, each Subsequent router performs routing-of the packets according to the determined route and priority, such as the one that is now described in detail.

To determine the depth requirement, the originating router in network 100 determines the equivalent bandwidth needed for the call or other connection and also uses a Bandwidth in Progress (BWIP) indication for a particular class of service at the beginning of the call or another connection. For that purpose, two quantities: Bandwidth Level Count (BWPC) and Bandwidth Overflow Count (BWOV) are maintained for each link by connecting a pair of originating / terminating routers. During a given interval of X minutes, each router, such as a router 12, traces for each link to another router the following quantities: BWPC (link) = Sum of all bandwidths (B) required for flows in the link; Y BW0V (link) = Sum of BW required for each flow blocked in the link In the service class routing method, several virtual networks are maintained, which are bandwidths assigned according to demand. Each router also maintains the following two Depth parameters for each virtual network: BWprom ^, the Bandwidth required by each Virtual Network (Vnv) and node pair k to bring the average of the Bandwidth in Progress (BWIPvJt) f = Load of Erlang > ? vkI. x (average bandwidth per virtual connection).] and BVfaiax, the Bandwidth required to comply with the objective of the blocking probability of Degree of Service = [TREBS (Erlangv Load?, Degree of Service) x (average bandwidth per virtual connection)] _? £ -. where TREBS represents * the # 846 * 1 ^ known Erlang-B formula for line requirements.

In practice, BWprom vk and BWmax, are computed to pre-written intervals, typically per week. Different values of BWprom and BVI & x can be used for different periods of the day (business peak, residential peak).

Four different blocking reserve intensities (BR1, BR2, BR3, BR4) are used, where 0% < BR1 = BR2 = BR3 = BR4 = 100%. The reservation level. N is 0 if the link block (NN) does not exceed BR1, N = 3 if NN exceeds BR3 but not BR4, and N - 4 if NN exceeds BR. This relationship is shown in Table 1.

Table I Determination of the Reserve Level (N) The one for each link is used in the termination of the Load Status of the link. In addition to the Load State of each local link (that is, the link associated with a particular router), the Load Status of all other links in the network is received from other routers using, for example, an extension of the mechanism of OSPF flood currently used. A metric such as "available throughput or bandwidth" can theoretically be supported by the OSPF routing algorithm to provide an indication of the Load Status of all links in network 10. Also, another metric such as "delay" can provide An indication of the Load Status. In addition to flooding each router in the network, this link metric information on bandwidth availability, delay, or other measures could flood a centralized Bandwidth Intermediary (BB), 20 which can track information. the state of the link and perform routing computations, as discussed at length below.

A link that extends between a router pair is considered in a reserve state (R) if the Inactive Bandwidth (ILBW) is less than or equal to a Reserve Intensity (Rthr), as defined below. The link is considered in the Heavy Load Intensity (HLthr) state if the Inactive Bandwidth is less than or equal to the Heavy Load Intensity (HLthr) for the link but less than Rthr. Conversely, the link is considered as Lightly Loaded (LL) if the Inactive Bandwidth for each link in the route is greater than HL for the link. This relationship is best illustrated in Table II (here we have omitted, for simplicity, the subscripts k that denote the pair of nodes for each variable): Table II State Condition Loaded The Reserve Intensity Rthr and the Intensity of Heavy Load HLthr are given by the relations Rthr = N x .05 x BWmax HLthr = Rthr + .05 x BWmax where N is the reserve level based on the Blocking Reserve intensities (BR1, BR2 ^ R3, and BR4).

The Search Depth '(DoS) for a flow that uses several Load States depends on the Bandwidth in Progress (BWIPv), BWpromv and BWmaxv, the priority of the call or other connection, and if the route is the first route selection or alternate route, as illustrated in Table III (also omitted here), for simplicity, the subscripts k that denote the pair of nodes for each variable): TABLE III CRITERIA DoS The originating router determines the allowed DoS for the call or other connection according to Table III, first the originating router tries to route the call on the shortest route to the terminal router.

For a key service flow: If BWIPv = 2 x BWmax, then all loading states they are allowed Yes BWIP > 2 x BWmax, then only LL links are allowed.

For a normal service flow: If BWIPv = BWpromv, then all load states are allowed in the first route selection and HL and LL states are allowed in alternate routes.

If BWprom = BWIP = BWmax, then only the HL and LL states in the first route selection and the LL status is allowed in alternate routes.

Yes BWIPv > BWmaxv, 'then only the links are p LL in the first route selection and alternate routes.

• For a call from the best effort service only LL links are allowed.

The originating router first determines the service class of the call (or other connection requirement) of information associated with the call. In routing calls according to the invention, an originating router, (for example, router 12) will determine the Load Status of the links of the network. As discussed above, the Load Status information for all links in the network 10 could be distributed, for example, via the OSPF flood protocol. The source router selects a route that has, for example, a minimum number of connections using the routing algorithm of the shortest route. When using the depth parameters discussed above, the source router ffi & ba then if the links forming the selected route have an available depth (bandwidth capacity) for the given service class. If so, the router routes the packets of the call or connection required in the links of the selected route. Otherwise, another route is selected and the step is repeated to determine if links on the route have available capacity and depth. If the originating router can not route the call or other connection to the selected destination router, and there are other terminal routers that can route the call, then the originating router uses the shortest route algorithm to select candidate routes and the routing technique of service class to route the call to such terminal router. , If there is no terminal router available, the call is blocked.

As discussed above, the centralized bandwidth broker (BB) 20 could receive the metric information of the link state through a flood mechanism, and perform the same routing computations described above for the originating router. This, in response to a requirement from a source router, for example, the BB20 could select a route with a minimum number of connections using the shortest route routing algorithm, depth parameters, and link bandwidth available. Once a permissible route is found, the route information returns to the originating router which can consequently route the packets in the flow.

After the route is established by the source router and the packets flow along the route, at each connection point, the receiving router performs a packet priority queue based on the priority ie routing assigned by the originating router to each packet, such as the one contained in the TOS field indicator of the package. The TOS indicators in each packet are set so that the receiving router at each subsequent connection point uses the same priority queue as determined by the originating router for the shortest route selected and the routing treatment COS. Therefore the COS capacity provided by the method of the invention can be improved by the addition of a priority queuing capability. In each link, the router maintains a tail discipline such that the packets that have the highest TOS requirement (TOS and preceding bits) have priority over smaller TOS requirements, such as the best effort services.

The above describes a technique for obtaining a routing per Class of Service in an IP network. The above-mentioned aspects only illustrate the principles of the invention. Those skilled in the art may contain the principles of the invention and fall within its spirit and scope.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, the content of the following is claimed as property.

Claims (18)

1. CLAIMS n Method for routing a connection requirement between a source and a destination in a network with Internet Protocol (IP) comprised of a plurality of routers connected by links carrying data packets representative of the requirement between the routers, characterized in that it comprises : (a) exchange of status messages on the network to identify a group of available routes each running between a source and a destination, each route including at least one link; (b) selection from the group of available routes of a first route to route the connection requirement; (c) determination for the connection requirement of your class of service; (d) checking the selected route to determine whether each link forming the selected route has a bandwidth available for the service class of the connection requirement, and if so, routing of the data packets representative of the call in question. said outbound link; on the contrary; (e) selection of another route; and (f) repetition of step (d) and repetition of step (e) in the event that said other route has an available bandwidth lacking link.
2. The method according to claim 1 characterized in that the states of the messages are exchanged between routers.
3. The method according to claim 1 (?) Characterized in that the network includes a corridor of bandwidth to track information of the state of the link and because the stage of exchange of status messages includes the stage of message exchange between the routers and the bandwidth corridor.
4. The method according to claim 1 characterized in that the first route is selected to minimize costs.
5. The method according to claim 4 characterized in that the first route is selected to minimize the number of connection points between routers.
6. The method according to claim 1, characterized in that said route is selected by the source router based on the link flood state information.
7. The method according to claim 2, characterized in that said route is selected by said corridor of centralized bandwidth based on the information of the flood state of the link.
8. The method according to claim 1, characterized in that the step of checking whether the network has an available bandwidth includes the steps of: (a) measuring the current bandwidth in said link; (b) determining the blocking of the link according to the current bandwidth; (c) establishment of reserve intensities in accordance with link blocking; (d) determining the state of charge of the links in a route according to the bandwidth reservation intensities; and (e) establishing the availability of a route according to the service class of the connection requirement, the Load State of the links in the route, and a required bandwidth for each virtual network associated with the connection requirement. of service class.
9. 9. The method of coi vsa? Jiad with claim 8 characterized in that the bandwidth required for the service class is established periodically.
10. 10. The method according to claim 1 characterized in that the service class call connection includes key service, normal service and best effort service.
11. 11. The method according to claim 10 characterized in that each link can have one of the Reserved, Light Charge, Heavy Load states.
12. 12. The method according to claim 10, characterized in that for the key service, all load states are allowed if the current bandwidth in progress (BWIP) = 2 x BWmaxv, where BWpro ^, the Bandwidth required by each Virtual Network (Vnv) and node pair k to bring the average of the Bandwidth in Progress (BWIPvJt) [= Load of ErlangvA. x (average bandwidth per virtual connection) ^] and BW ax vk., The Bandwidth required to meet the objective of the blocking probability of Degree of Service = [TREBS (Load of Erlang ^, Degree of Service) x (average bandwidth per virtual connection) k)
13. The method according to claim 12 characterized in that for the key service, only Light Charge links are allowed if BWIPv > 2 x BWmax.
14. The method according to claim 10 characterized in that for normal service, all load states in the first selection path are allowed and heavy load and light load states are permitted in alternate routes, if the current bandwidth in progress (BWIP) = BWprom, where BWprom ^, the Bandwidth required by each Virtual Network (Vnv) and node pair k to bring the average of the Bandwidth in Progress (BWIP) [= Load of Erlang ^ x (width of average band per virtual connection) vk.] J and BWmax, the Bandwidth required to meet the objective of the blocking probability of Service Degree = [TREBS (ErlangvJt Load, Service Degree) x (average bandwidth per virtual copy-vj. ] J "Ht
15. 15. The method according to claim 14 characterized in that for normal service calls, the heavy load and light load states are allowed in the first selection route and only the light load status is allowed in the alternate routes, if BWpromvk = BWIPv = BWmaxvk *
16. 16. The method according to claim 14 characterized in that for normal service calls, only light load links are allowed on all routes when BWIPv > BWmaxvk ,.
17. 17. The method according to claim 14, characterized in that only light load links are allowed for the best effort service.
18. 18. The method according to claim 1 characterized in that in each link it maintains a queuing discipline so that packets having a Service Type (TOS) of higher priority pass before the packets having a lower priority TOS. The priority of the flow packets representing calls or other connection requirements in a packet network (10) is determined from the Class of Service of the call. In receiving a call, a receiver router (12, 12, 123) identifies the available routes, typically by exchanging messages with other routers in the network. After selecting the route, the receiver or centralized bandwidth router determines whether the links comprising the selected route have an available bandwidth for the service class of the call. If so, the router routes the call to the next connection point along the route. Otherwise, "the router selects another route (s) and checks if the links on the route have sufficient bandwidth for the service class of the call.