Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L45/00—Routing or path finding of packets in data switching networks
  • H04L45/02—Topology update or discovery
  • H04L45/04—Interdomain routing, e.g. hierarchical routing
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
  • H04L65/1066—Session management
  • H04L65/1101—Session protocols
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L45/00—Routing or path finding of packets in data switching networks
  • H04L45/302—Route determination based on requested QoS
  • H04L45/306—Route determination based on the nature of the carried application
  • H04L45/3065—Route determination based on the nature of the carried application for real time traffic
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
  • H04L65/1066—Session management
  • H04L65/1069—Session establishment or de-establishment

Definitions

• a method of selecting a telephony route within an IP telephony domain, corresponding device and computer program is a method of selecting a telephony route within an IP telephony domain, corresponding device and computer program.
• Telephony is understood to mean both conventional telephony services or integrating advanced services such as video telephony or the synchronous digital data transfer service.
• the present invention relates more particularly to the exchange of information to allow the synchronization between the service layer (that is to say that dealing with call routing) and the network layer (that is to say that the occupying IP datagram transfer) for routing information flows between IP telephony domains.
• IP network is the backbone adopted by operators to pool their heterogeneous service offerings including IP telephony commonly referenced by the abbreviation VoIP (or "Voice over IP” for “Voice over IP”) or more generally grouped under the topic of conversational services.
• VoIP Voice over IP
• VoIP over IP Voice over IP
• This overall coverage is achievable through the establishment of interconnection agreements with other third-party service providers to extend the reach of a service outside the administrative boundaries of a single service provider.
• LS Location Server
• ITAD telephony domain
• AS Autonomous System for "Autonomous System”: It is a set of IP resources managed by a single administrative entity, also called “IP connectivity provider”. As part of the BGP inter-domain routing protocol (Border Gateway
• each AS is identified by a unique identifier.
• PSTN switched telephone network
• the telephone operators establish bilateral agreements to extend the overall coverage of the telephone service. The level of coverage achieved depends primarily on the number of agreements reached.
• Large global operators establish a large number of agreements and can thus join most existing destinations.
• Local operators establish only a limited number of agreements of which only one or two with large operators. For example, a national incumbent operator in a developing country will establish agreements with other national operators and one or two agreements with global operators to evacuate communications to the rest of the world.
• IP IP
• TRlP allows interconnected ITADs to exchange all the destinations they can reach and, in particular, facilitates the selection of the most appropriate "Gateway” or "backbone” to evacuate IP telephony traffic to the RTC network.
• the TRIP protocol is put implemented by LS ("Location Servers” for “Location Servers”) that propagate TRlP routes containing attributes to qualify the routes in question.
• LS Local Security Servers
• This particular protocol is independent of the type of signaling protocol deployed for the actual establishment of calls.
• TRIP can be used in conjunction with SIP, H.323, or any other signaling protocol.
• Each LS maintains a local routing database called TRIB ("Telephony Routing Information Database” for "Telephony Routing Information Database”).
• This basic routing is powered by received listings of neighboring LS (another telephony domain, for example).
• the operation of the TRIP protocol is similar to that of the Border Gateway Protocol (BGP). Advertisements between neighboring LSs are performed as route update messages, called UPDATE messages. These messages are defined by the TRIP protocol and are exchanged between the LSs to inform the LSs of the same domain or a neighboring domain of the available routes.
• Border Gateway Protocol Border Gateway Protocol
• each ITAD being administered by a single telephone operator.
• IP IP
• These operators each have one or more LSs.
• Each LS maintains a routing base that it feeds with advertisements received from its neighbors (ie other domains) and LSs from its own domain. These ads are updated and redistributed to other neighbors if interconnection agreements allow.
• the 11TAD4 LS 14 updates the advertisements received from the T1TAD5 LS 15 and re-propagates them to ITAD3 13. It should be noted that an ITAD is not necessarily deployed on a single AS or " IP transfer domain ".
• an LS treats three types of routes: the external routes ("External Routes"), received from LS located in
• Adj-TRIBs-In 22 stores the routing information conveyed by UPDATE messages. This routing information, also called “routes”, is the input to a route selection process 21 ("Decision Process"). A given LS maintains a table “Adj-TRIB-In” 22 (for adjacent TRIB in which stores the set of route advertisements received from an adjacent LS) by neighbor LS;
• Ext-TRIB 24 only one "Ext-TRIB” (“external TRIB”) table is maintained by LS.
• This table contains the result of a route selection process applied to the external roads 25 ("Adj-TRIBs-IN”) and local roads 26 ("Local Routes").
• the techniques of the prior art allow only one route to be chosen per destination; "Loc-TRIB” 20 (“Local TRIB”): This table contains local routes resulting from the application of local routing policies to each LS; Adj-TRIBs-Out 23: These are the routes that the local LS will announce to their peers.
• the QoS-Enhanced Border Gateway Protocol (Q-BGP) can be used to determine the QoS processing that will be reserved for voice streams by the QoS. transport layer.
• Q-BGP QoS-Enhanced Border Gateway Protocol
• a disadvantage of this technique of the prior art is related to the lack of synchronization between the service layer and the network layer in order to route the media streams. Indeed, in the context of the deployment of the TRIP protocol between neighboring ITADs, the media streams follow either the path determined by the IP routing protocols such as the BGP protocol or the one imposed by the telephony platforms of each ITAD. This last possibility requires, in the context of the use of the SIP protocol for example, to modify several times the content of the SDP part of these messages.
• a corollary disadvantage of these transfer techniques of the prior art stems from the processing of the media streams by the ASs. Indeed, as these flows follow a path determined by the BGP protocol, NTAD does not have the ability to control the path taken by the stream. Thus, flows may follow an optimum path (for example, better QoS) at the ITAD level, but not at the inter-AS path. This amounts to negating negotiations and agreements between neighboring ITADs if the QoS clauses are not met.
• a spiral of AS occurs when, after a negotiation between ITAD for the delivery of a media stream, that stream takes several times the same
• ITTADl 31 1 uses ASl 321 to evacuate its voice traffic
• TITAD2 312 uses AS2 322.
• ITT AD3 313 uses ASl 321, that 1TTAD4 314 uses AS4 324.
• I 1 ITADS 315 uses AS3 323 and ITTAD6 316 uses AS6 326.
• the best route to reach D 302 from S 301 is via ⁇ AS1, AS4, AS5, AS6 ⁇ .
• a client S 301 wants to make a call to D 302 and riTAD1111 has chosen the route through ITAD2 312 and 1TAD3 313 to reach ITAD ⁇ 316 to which destination D 302 is attached.
• This telephone-level route assumes the existence of an IP route (at the level of the transfer layer) traversing the domains: AS1, AS2, AS1, AS6.
• ASl the level of the transfer layer
• ASl the domains
• ITADl is deployed on the two AS, AS1 and AS2, and that ITAD2 is deployed on the AS4 domain and that the two IP telephony operators managing the two ITADs, ITAD1 and ITAD2, have concluded an agreement to interconnect their platforms. services and extend the reach of their voice services to quality of service.
• ITADl is based on a premium class (ie a class that guarantees an IP transfer with a better quality of service, for example guarantees a loss rate of 99.999% or a maximum delay of less than 50ms) offered by ASl and AS2;
• ITAD2 uses another premium class offered by AS4.
• IP network service providers exchange routing information to help build routes in coherent and consistent QoS plans.
• the premium class of the AS4 is linked to the premium class of 1 ⁇ S2 through a dedicated inter-domain route.
• two best effort routes ie the routes available thanks to the activation of a routing protocol such as the BGP (Border Gateway Protocol) exist: that which crosses AS1, AS2 and AS4, and the one that crosses ASl, AS3 and AS4, but only one premium route exists.
• This road crosses ASl, AS2 and AS4 .
• voice traffic from C 1 to destination of C2 for the telephone service offered by ITADl uses the premium route and not the best effort route, but, unless a static configuration is implemented, the assurance of obtaining an AS1, AS2 traversing route AS4 can not be certain to be obtained by riTADl, so that it is very likely that, at the moment of the actual transfer of the media streams, they pass through AS1, AS3 and AS4.
• signaling does not have a direct interface to the IP routing protocols that p support the routing of IP packets.
• the path of the signaling packets may be different from that of the media packets. In this case, the guarantees negotiated during the establishment of the call
• the solution proposed by the invention makes it possible to overcome these drawbacks of the prior art, by means of a method for selecting a telephony route of at least one digital stream serving a telephony destination, within a first server. of location belonging to a first telephony domain
• IP deployed on at least one autonomous system said autonomous system exchanging with its neighbors IP routing information designating at least one IP destination to update an IP routing table.
• said method comprises the following steps: search by the first location server of said IP routing information, said IP routing information comprising an identifier of a second IP telephony domain with which said at least one destination is associated IP telephony, called destination identifier; selecting said IP telephony route to reach said at least one telephony destination, according to a predetermined second telephony domain selection criterion, according to said destination identifier.
• IP routing information related to the transfer layer This allows the location server that performs the selection to be informed by the autonomic system, IP routes actually used by digital flow during transfer. Autonomous systems therefore communicate with each other IP routes and the locating servers can use this information to perform the selection of the telephony routes.
• said routing information comprising a list of autonomous system identifiers crossed to reach the telephony destination associated with said identifier of destination
• the step of searching for said routing information consists in extracting from said routing table of said autonomous system said list of autonomous system identifiers crossed.
• the invention allows the location server to access a managed routing table at the transfer layer. He can therefore know the roads
• said method comprises the following steps: receiving at least one route update message from a second location server, said message defining at least one updated telephony route; comprising a list of traversed autonomous system identifiers and a list of IP telephony domains traversed from said telephony destination; extracting from said list of IP telephony domains the identifier of an IP telephony domain with which said telephony destination is associated, said destination identifier; obtaining a set of at least one telephony route, previously stored in said first location server, serving said telephony destination; search, within said at least one autonomous system, of at least one IP route whose said at least one IP destination is identical to said destination identifier, said IP routes searched; selecting a telephony route, within said set of telephony roads, including a list of autonomous systems traversed includes the same identifiers of autonomous systems that the list of autonomous systems identifiers of said at least one searched route, when such a road
• the location server performing the selection of the route therefore implements a method that makes it possible to choose a route taking into account the routing information.
• This method is based on the reception, by the location server, of update messages. These messages include a list of autonomous system identifiers inserted into the telephony route.
• the telephony route includes information identifying the route
• the location server retrieves the identifier of the telephony domain of the destination and obtains a telephony route list that serves that destination. This obtaining enables him to search, within his own autonomous system, at least one IP route (at the transfer level) which serves this destination.
• the system can therefore select a route according to two channels or selection criteria: if it identifies, within the set of telephony routes, a route whose list of autonomous systems crossed includes the same autonomous system identifiers as the list autonomous system identifiers of the searched route, then it selects this identified route; if not, it selects a route that serves the same destination according to another criterion. It can, for example, be the first telephony route found.
• the server then stores this selected route. It will then be used for the routing of digital flows during a routing process.
• such a method comprises a step of transmitting at least one route update message to a location server, said message defining at least one updated telephony route comprising at least one identifier of at least one autonomous system and at least one identifier of at least one IP telephony domain.
• the location server keeps its peers informed of the selection it has made. The other location servers are therefore able to use and take into account this route.
• such a method comprises the following steps: receiving at least one route update message from a second location server located in said first telephony domain, said message defining at least one updated telephony route comprising a list of traversed autonomous system identifiers and a list of IP telephony domains traversed from said destination; storing said at least one updated telephony route.
• the location server therefore has the ability to receive updated telephony routes by its peers located in the same telephony domain as itself. It can therefore realize an immediate storage of this road.
• said list of autonomous system identifiers is ordered according to at least one predetermined scheduling criterion and said selection step takes account of said at least one predetermined scheduling criterion.
• the list of identifiers allows the location server to identify the autonomous systems used by the telephony route. This list, for a given route, can be ordered, namely to indicate, for example, the order in which the autonomous systems are traversed by the digital stream.
• the location server is aware of the standard of scheduling and the order given to autonomous road systems.
• the selection of the telephony route by the autonomous system can take into account this scheduling, in order, for example, to optimize the telephony path.
• the list of independent identifiers servers is not orderly and said selection step takes into account the first identifier of said autonomous system identifier list.
• the process selection step implemented by the location server is only the first identifier of the list. So even if a location server transmits a road that is not ordered, the location server that processes this information is able to realize a route selection based on the road that has been provided by the message update.
• the invention also relates to a device for selecting a telephony route of at least one digital stream serving a telephony destination within a first location server belonging to a first IP telephony domain deployed on at least one system.
• autonomous transfer system said autonomous system exchanging with its neighbors IP routing information designating at least one IP destination to update an IP routing table
• said device comprises the means of: searching said IP routing information, said IP routing information comprising an identifier of a second IP telephony domain which is associated with said at least one destination IP telephony, said identifier destination; selecting said IP telephony route to reach said at least one telephony destination, according to a predetermined second telephony domain selection criterion, according to said destination identifier.
• such a device comprises means for implementing the steps of the method of selecting telephony routes, as described above.
• the invention also relates to a computer program product downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor.
• such a computer program product includes program code instructions for the execution of the telephony route selection process as described above.
• the invention also relates to a propagation signal for implementing the routing route propagation method.
• a propagation signal for implementing the routing route propagation method.
• such a signal comprises a route update message including data representative of a list of identifiers of crossed autonomous systems and a list of IP telephony domains traversed from said destination.
• FIG. 1 shows an example of telephony domain architecture (ITAD);
• FIG. 2 illustrates the structure of the routing databases (TRIB) used by the location servers (LS) routing the calls in the telephony domains (ITAD) presented in FIG. 1;
• FIG. 3 describes the spiral phenomenon of the AS occurring during the choice of a telephony route according to the techniques of the prior art;
• FIG. 4 illustrates the need to obtain synchronization between the transport layer and the service layer;
• FIG. 5 depicts the new routing database structure for an LS according to the invention
• FIG. 6 illustrates an example of synchronization realized using the method according to the invention.
• the invention therefore proposes to perform a synchronization between the transfer layer and the service layer in order to avoid the AS spiral phenomena and the quality of service depreciation.
• the general principle of the invention rests on the taking into account by a
• Adj-TRIBs-In 22 stores the routing information conveyed by UPDATE messages. These routing info ⁇ nations, also called “routes", are the inputs of a route selection process 21 ("Decision Process").
• a given LS maintains a table “Adj-TRIB-In” 22 (for adjacent TRIB in which stores the set of route advertisements received from an adjacent LS) by neighbor LS;
• Ext-TRIB 24 only one "Ext-TRIB” table (“TRIB externat”) is maintained by LS.
• This table contains the result of a route selection process applied to the external roads ("Adj-TRIBs-fN") and local roads 26 ("Local Routes").
• the techniques of the prior art only allow to choose one route per destination; "Loc-TRIB” 20 (“Local TRIB”):
• This table contains local routes resulting from the application of local routing policies to each LS;
• Adj-TRIBs-Out” 23 (“Adjacent TRlB out”): These are the routes that the local LS will announce to their peers.
• This cache is provided by the IP connectivity provider (Administrative Entity managing an AS) either as a set of permissions to access the routing tables or by l intermediate of an "looking glass” (process for visualizing IP routes on IP backbones).
• This table can be, for example, the copy of the routing tables (RIB,
• This new table is used, for example, by a TRIP route selection process to ensure synchronization between the transport layer and the service layer.
• Each ITAD has an identifier in the form of an AS number or a routable IP address; - This identifier is the same as that used by the TRIP protocol to provide the attributes "AdvertisementPath" and "RoutedPath";
• ITAD identifiers are announced in an interdomain routing protocol such as BGP or q-BGP. These identifiers may not be the true IP addresses of the LSs; -
• Each IP connectivity service provider (administrative entity managing the AS) provides IP telephony operators (managing an ITAD) an interface or a cache of its local routing table (Cache_Local_RlB) filled in by an inter-domain routing protocol such as BGP or q-BGP. This cache is updated at the request of IP telephony service providers or dynamically through another mechanism;
• the local LS queries the local RIB cache (ie Cache_Local_RIB) between domains to find the path to join
• the LS retrieves the BGP attribute
• AS_PATH (BGP specific attribute) This attribute informs the list of IP domains traversed by the BGP route in question.
• the local LS searches in its "Adj_TRIB_In” the existence of other routes towards DEST, whose list of AS used to carry voice traffic with identical characteristics to
• the LS extracts the identifier of the first AS from the list, that is to say the identifier of the next AS, denoted ASid.
• the LS searches, among the routes to DEST, contained in the Adj_TRIB_ln, the one whose next provider of IP connectivity is identical to ASid. This route is then stored in the "Local_TRIB" table. If no route exists then the LS executes a standard selection process or other local policies; 5.3 Example of implementation To illustrate the synchronization procedure, consider the example illustrated in Figure 6. Suppose that ITADl 61 1 uses ASl 621 to evacuate its voice traffic, that ITAD2 612 uses AS2 622, that ITAD3 613 uses ASl
• ITAD4 614 uses AS2 622
• ITAD5 615 uses AS3 623
• ITAD ⁇ 616 uses AS6 626. It is assumed that to join D 602 from S 601, the AS path chosen by Inter-domain routing protocol is ASl, AS2, AS3, AS6 (621,
• ITAD6 announces its prefixes to ITAD5 and ITAD3; - ITAD3 and ITAD5 have no routes other than those received from ITAD6 to serve ITAD ⁇ prefixes including D. Therefore, ITAD3 and ITAD5 store these routes in their local TRlBs and announce (through UPDATE messages). These prefixes to ITAD4 for rITAD5 and ITAD2 for TITAD3; - The same procedure applies for ITAD4 and ITAD2 from FITAD3 and riTAD5.
• ITADl receives two routes to serve the same prefixes, it consults the cache of local routing tables provided by I " ASl to find the route selected by the inter-domain routing protocol to the ITADô identifier .This query returns the path ⁇ AS2, AS3, AS6 ⁇ . ITADl chooses the TRlP route received from ITAD4 and stores it in its table
• this information can improve the quality of service.
• an LS has a simple and effective way to optimize an end-to-end path for a given destination.
• This same information also makes it possible to detect anomalies, such as IP spirals for example, since the service layer is aware of the ASs through which the data travels.
• the present application describes only the principle of information feedback, or identifiers for the IP layer.
• a list of identifiers relating to the IP layer is obtained, and then propagated between the LSs implemented by the ITADs.
• an AS number identifies the IP connectivity provider at the transport layer to carry voice. This number is provided to an administrative management domain (ITAD) which forwards it to a neighboring domain.
• ITID administrative management domain
• This document presents an embodiment based on the location servers LS. It is understood that this embodiment is that an example of implementation. Especially. the invention can quite be implemented using proximity servers (also called “proxy” servers).
• TRlP protocol is implemented by the LS (location servers) that propagate TRIP routes, containing attributes to qualify the routes exchanged.
• the standard version of the TRIP protocol (detailed in Rosenberg et al .: RFC3219: “Telephony Routing over IP (TRlP)" of January 2002) provides for alternate routing information between two neighboring LSs via the UPDATE message. which has a number of attributes.
• This attribute includes the following attributes:
• This attribute indicates whether the attribute in question should be filled in or not in a TRIP message.
• TRIP Type Code The unique identifier of the TRlP message in question. The purpose of this attribute is to create and store a list of traversed ASs to reach the destination in question. In other words, it is an attribute of the service layer which contains information relating to the transport layer. It is then propagated from an IP telephony domain (ITAD) to a neighboring IP telephony domain.
• ITID IP telephony domain
• the AS_PATH attribute is composed of a sequence of segments, or fields, "AS path".
• Each segment "AS path” is composed of a triplet ⁇ path segment type, path segment length. path segment value>, defined as follows: each "path segment type” has a length of 1 byte which can take the following values:
• each path segment length has a length of 1 byte and contains the number of AS contained in the path segment value; the field "path segment value" contains one or more AS numbers. each encoded as a field of 2 bytes long. This new attribute therefore lists the succession of AS traversed by the data associated with a call.
• Each LS maintains a routing table that it feeds with the announcements received from the neighbors and LSs of its own domain. These ads are updated and redistributed to other neighbors if the agreements allow.
• an LS when an LS propagates a TRIP route that it has learned in an UPDATE message from another neighboring LS, it is expected that it modifies the new AS_PATH attribute of the route according to the type of LS to which it is to re - propagate the route, according to the following procedure.
• LS peer If the LS to which the route is advertised (LS peer) is not located in the same ITAD, two cases arise for the update of the attribute AS_PATH: if the first segment of the AS_PATH is of type AS_SEQUENCR, the local system adds the number of its IP connectivity service provider as the last element of the sequence; if the first segment of the AS_PATH is of type AS_SET, the local system adds a new segment of type AS_SEQUENCE at the beginning of the AS_PATH; this new segment contains the domain number of its IP connectivity service provider.
• the advertisement includes the IP connectivity service provider's number in the AS PATH attribute of all UPDATE messages to be sent to its TRIP peers in neighboring ITADs.
• the LS includes an empty AS P ATH in all UPDATE messages to send to its TRIP peers in its own ITAD.

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• 2007
  • 2007-04-20 WO PCT/FR2007/051149 patent/WO2007122353A1/fr active Application Filing
  • 2007-04-20 EP EP07731924A patent/EP2014031A1/de not_active Withdrawn
  • 2007-04-20 US US12/298,000 patent/US7990892B2/en not_active Expired - Fee Related

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