EP1757049A1

EP1757049A1 - Method for reserving resources for inter-domain-routing by means of quality of service characteristics

Info

Publication number: EP1757049A1
Application number: EP05762890A
Authority: EP
Inventors: Thomas Engel
Original assignee: Siemens AG; Nokia Siemens Networks GmbH and Co KG
Current assignee: Nokia Solutions and Networks GmbH and Co KG
Priority date: 2004-06-15
Filing date: 2005-06-09
Publication date: 2007-02-28
Also published as: DE102004028815A1; WO2005125117A1

Abstract

The invention relates to the input of resources for inter-domain-routes of QoS (Quality of Service) traffic. According to the invention, a route to a target (N1) is communicated to a network element (R45) of a routing domain by information from an inter-domain routing protocol (e.g. BGP). Said route is determined by the network element (R45) for the routing of at least one part of relevant traffic which is to be transported to the target (N1) via another route. Information is transmitted to a resource management system prior to or at the same time as the diversion of traffic from the current route to the newly communicated route, in order to reserve resources for the newly communicated route. Said method enables the resource reservation and the diversion to be co-ordinated together. Diversion only takes place if the required resources are reserved. Maintenance of the quality of service characteristics is therefor possible during inter-domain routing.

Description

description

Resource reservation method for inter-domain routing with quality of service characteristics

The invention relates to a method for providing resources for inter-domain routing, an edge node with means for carrying out the method and a server for supporting the method.

The invention is in the field of communication networks and makes a contribution to the further development of data networks for the transmission of real-time traffic while maintaining quality of service characteristics.

The currently most important data network, the Internet, is actually a network that consists of a large number (currently over 1,7000) of networks. In the nomenclature of Internet experts, these networks are usually referred to as autonomous systems (abbreviated AS) or routing domains (routing do ain). Protocols for the routing or transport of data packets are defined within these routing domains (e.g. open shortest path first (OSPF) protocol).

The interaction of autonomous systems on the Internet, i.e. The "cross-network forwarding of data packets or IP packets (IP: Internet Protocol) across the borders of individual IP networks is carried out with the Inter-Domain Routing Protocol (BGP: BGP: border gateway protocol) ), which is described in RFC1771 (RFC: request for comments). In the context of this protocol, neighboring edge routers or edge nodes set up so-called BGP peering sessions and exchange routing information via UPDATE messages. Using BGP, a routing

Domain_ which IP addresses can be reached via which routes. Routes are here as cross-network routes on the To understand the level of autonomous systems and are coded as sequences of AS numbers: For this purpose, autonomous systems are assigned unique AS numbers. If traffic is to be switched to a new route, an edge router uses a UPDATE message to announce a route change (announcing a new route, canceling an existing route, or both). Such a route change generally spreads via further UPDATE messages from network to network across large parts of the Internet. Networks that are further away generally receive several in several ways

UPDATE messages and see different routes from which they select the best route in their view. Since UPDATE messages generally arrive with significantly different transit times via different routes, a network only gradually learns the alternatively available routes. During this learning process, a network will generally shift or redirect the affected traffic several times to alternative routes. A shift takes place whenever a better route becomes known with the arrival of another UPDATE message. This means that the first UPDATE starts a convergence process that takes about three minutes on average after measurements. During the convergence period, the traffic concerned is generally rerouted or redirected to alternating routes and considerable delays in IP packets and high packet loss rates must be expected. .. ₃

Conventional data networks therefore offer a so-called "best effort" transmission, i.e. a transmission that does not guarantee compliance with quality features or quality of service features (e.g. maximum delay, maximum loss rate, ...).

In the future, IP networks will also support applications in which real-time traffic, ie voice, video and data streams, are transmitted. For this real-time traffic, a fast and reliable transport of IP packets is required. This means transport services that guarantee compliance with service features or Quality of Service (QoS) parameters. For this purpose, future IP networks, in addition to the traditional "best effort" services, are to provide new transmission services 5 that make the required bandwidths continuously available to traffic and reliably transmit IP packets to the recipient with low, hardly fluctuating delays and very low packet loss rates , In the following, these new services will also be referred to as QoS services and the

10th traffic called QoS traffic. Within individual routing domains there are in some cases already standardized approaches for the transmission of QoS traffic within routing domains, which generally include an identification of the QoS traffic and the reservation of bandwidth. examples

15. games are the use of the DiffServ (Differentiated Services) concept (standardized by the IETF in RFC2474 and RFC2475) or the MPLS protocol (MPLS: multi-protocol label switching) in conjunction with RSVP (resource reservation protocol).

20 Since the Internet is an amalgamation of a growing number of individual IP networks or autonomous systems (AS) that are managed and controlled by different organizations, QoS services in this network must be cross-network

25 will be provided. It is intended to use resource management systems that provide QoS traffic with the resources required for guaranteed quality of service across networks. One approach is given by the BGRP (border gateway reservation protocol).

The object of the invention is to optimize the resource reservations for inter-domain routing.

The invention is based on the knowledge that the transmission quality can be improved by coordinating resource reservations and route changes in inter-domain routing. According to the invention, a message is sent to a resource management for the purpose of resource management before or at the same time as a route change of an inter-domain route, ie before or at the same time to redirect or rerout traffic to a newly communicated inter-domain route. Reservation for the new route is sent. In this way, a reservation process is started at an early stage. The redirection of traffic can be delayed until a confirmation message is received from the resource management. The traffic can then be directed along the old route. If the resource management sends the confirmation message only after reserving the resources, it is ensured that the bandwidth required for the transmission is available. If the resource reservation is not successful, this fact can be communicated by the resource management in order to influence the route selection. A less conservative approach, which generally allows a quicker redirection from traffic to the new route, is to start the redirection before receiving the confirmation message or through resource management to receive the message (and not just the completed one) Reservation). It is assumed that the reservation will usually be successful.

It makes sense to make the procedure dependent on whether QoS traffic is affected by the redirection. A successful bandwidth reservation is not absolutely necessary for so-called "best effort" traffic. This can be taken into account by the network management completing the reservation before the confirmation if QoS traffic is affected by the redirection and otherwise sending the confirmation immediately after receiving the request. It is also possible to send a resource reservation message to resource management only when QoS traffic is affected. If a partial flow is diverted, an initial The reservation for the total current can be made and this reservation can then be adjusted by means of a renewal or refresh mechanism.

The invention ensures that QoS traffic can be redirected with minimal disruption to the guaranteed quality of service, since the required resources are already provided at the time of the redirection of the traffic or the processes necessary for redirecting or redirecting and reserving resources run in parallel as early as possible , The invention thus increases the availability of QoS services and simplifies resource management, which would have to detect routing activities in the event of a route change after the following reservation and could only react with a time delay.

The invention can be used particularly advantageously on the Internet, where the inter-domain routing is controlled using the BGP protocol. For various reasons, such as connection and node failures, traffic engineering and changes in the AS topology and business relationships, cross-network traffic is often switched to new cross-network routes. When a routing domain via BGP uses UPDATE messages to announce a new route, a convergence process is initiated during which all affected routing domains look for new stable cross-network routes. During this convergence time of the order of minutes, multiple route changes must be expected. Traditionally, affected traffic is affected by large, fluctuating delays and high packet loss rates during this period. Through the preceding or simultaneous resource reservation, the invention ensures the quality of service of QoS services when routing cross-network traffic flows to an extent that could not be guaranteed with a looser coupling of route change and resource reservation.

Resource management can be provided by a process that runs on a computer. If resource management and routing are given by processes on one computer, it makes sense to have them both run on the same computer (usually a peripheral node or peripheral router of a domain). This makes it possible to provide a local (i.e. internal computer) interface for the exchange of messages between the processes.

When resource management processes run on edge nodes of a domain, the situation can arise that a changed route, which is communicated to a first edge node of the domain, leads via a second edge node and that resource reservation by a resource management process on the second edge node is therefore necessary , In this case, it makes sense that a resource management process on the first edge node to which the resource reservation message is sent communicates with the resource management process on the second edge node for the purpose of resource reservation.

For communication between different resource management processes, it is helpful to have an assignment of the resource management process and the associated edge router, which can be accessed for the purpose of addressing other resource management processes. This assignment is. preferably accessible on a central server in the domain.

The invention is explained in more detail below with the aid of a figure.

The figure shows 5 autonomous systems AS1, AS2, ..., AS5. The network N1 is connected to AS1, in which the end systems with the IP addresses with the prefix 10.10.10.0/24, i.e. 10.10.10.0 to 10.10.10.255 can be reached. The prefix exists

10.10.10.0/24 from an IP address: 10.10.10.0, and a mask length: 24, and stands for all IP addresses that are in the the first 24 bits (mask length) match the specified address 10.10.10.0, ie 10.10.10.0 to 10.10.11.255. The figure shows only a part of the routers involved, namely the edge routers via which the autonomous systems are connected: R12, R13, R21, ..., R53. The resource management and routing processes on the routers are also only partially shown. As indicated with the resource managers RM42, RM43, and RM45, a resource manager is assigned to each edge router. The reference symbols IDR42, IDR43, and IDR45 stand for routing processes. As indicated by the notation, a routing process should also be assigned to each edge router. In this example, routes are shown in the form (P, al, a2, ..., aN). The prefix P describes the address block with the reachable destination addresses and the following sequence of AS numbers al, a2, ..., aN the sequence of the autonomous systems to be run through, via which the traffic reaches the destination addresses from the address block with the prefix P. For example (10.10.10.0/24, 2, 1) is a route from AS4 to Nl. Assume router R45 uses this route, ie (10.10.10.0/24, 2, 1), for traffic to network Nl. To describe a route change according to the invention, we also assume that router R45 learns the route (10.10.10.0/24, 3, 1) via R43 and decides to use this route in the future as the best route for the prefix 10.10.10.0/24.

According to the invention, the router R45 interrupts the further processing of this route (changing the FIB (forwarding information base) and forwarding the new route to R53 in the neighboring network AS5) after the notification of the new route and the decision to use the new route in the future and informs the

Resource manager RM45 on the same router R45 about the upcoming route change. The process IDR45 also communicates to the resource manager RM45 an IP address of the new output node R43. The resource manager RM45 checks whether he has a reservation for the prefix 10.10.10.0/24 and, if necessary, determines the resources required on the new route. If no QoS traffic is affected, RM45 sends immediately a message to IDR45, which causes the IDR45 to continue processing the new route (10.10.10.0/24, 3, 1). If QoS traffic is affected, the resource manager RM45 sends a reservation message to the resource manager RM43 in order to reserve the required resources along the new route (it may also be necessary to reserve required resources within AS4, between R45 and R43). After the resource manager RM45 has received a response with a positive reservation confirmation from the resource manager RM43 (and a possibly additional intra-domain resource manager), the resource manager RM45 sends a message to the process IDR45, which prompts the process to process the new route (10.10.10.0/24, 3, 1) to continue. The routing process IDR45 then activates the new route by changing its routing table (FIB (forwarding information base)) accordingly. From this point in time, the traffic concerned flows along the new route. The routing process IDR45 also forwards the new route, ie (10.10.10.0/24, 4, 3, 1), to R53 with an UPDATE message (in accordance with its routing policy).

Alternatively, the RM45 resource manager can immediately answer the notification of the upcoming route change and in parallel with the other activities of the routing process

IDR45 make the reservation, ideally both processes taking place almost simultaneously. Another possibility is that the routing process IDR45 continues to work on the route change without waiting for a response from RM45 in order to speed up the process.

The reservation of resource manager RM45 along the new route may not be successful. Then the resource manager RM45 could return this information to the process IDR45 to influence the route selection of the process IDR45. Since the new route, starting from the router R45 on which RM45 is located, first runs through its own network AS4 to an edge router or exit router (egress router) R43, the resource manager RM43 from R43 is not on the original route from RM45 to the destination network N1 and the resource manager RM45 must address the resource manager RM43 directly. For this purpose, the routing process IDR45 can pass on a router ID of the output router R43, on which the resource manager RM43 is located, to the resource manager RM45, for example an iP address of router R43. In order for resource manager RM45 to find resource manager RM43 using this information, resource manager RM54 must have access to an assignment of router IDs to addresses of resource management processes. This can be implemented by a central server on which all resource management processes log on, or with the aid of IP packets addressed to the R43 output router that bear an identifier, such as a special protocol ID. If a complete flow of traffic is routed, the resource requirements are generally known immediately. If only parts of it are switched over, the size of the partial flow should be estimated. A simple way would be to make a reservation for a complete transfer even if some of the traffic is diverted and to make the reservation using the

Quickly adjust the refresh mechanism of resource management. It is advantageously announced that this is a traffic diversion and which existing reservations or which traffic is affected (reservation or traffic ID) in order to avoid double reservations on common sections of the route.

Within the scope of the exemplary embodiment, the invention has been described for an application with decentralized resource managers RM42, RM43 and RM45. It is immediately clear to the person skilled in the art that the invention is not restricted to this case is. In particular, the invention can also be easily implemented with central resource management.

Claims

claims

1. Procedure for the provision of resources for an inter-domain routing, in which a route to a destination (NI) communicates with a network element (R45) of a routing domain (AS4) by means of a message from an inter-domain routing protocol becomes,

- The route through the network element (R45) for the routing of at least part of traffic currently being transported via another route to the destination (Nl) is determined, and

- Before or at the same time as the redirection of traffic from the current route to the newly communicated route, a message is sent to a resource management in order to effect a resource reservation for the newly communicated route.

2. The method according to claim 1, characterized in that a routing process (IDR45) of the network element (R45) is informed if the resource reservation is not successful.

3. The method according to any one of the preceding claims, characterized in that the message to the resource management is only sent if traffic is affected by the redirection, which is subject to compliance with quality of service parameters (QoS).

4. The method according to any one of the preceding claims, characterized in that the redirection of the traffic is carried out after a confirmation message sent by the resource management has been received by a routing process (IDR45) of the network element (R45).

5. The method according to any one of claims 1 to 4, characterized in that the traffic is redirected simultaneously or immediately after the resource reservation message is sent.

6. The method according to any one of the preceding claims, characterized in that the confirmation message is sent by the resource management when the resource reservation has been effected.

7. The method according to any one of claims 1 to 5, characterized in that the confirmation message is sent by the resource management when the resource reservation message has been received.

8. The method according to any one of claims 1 to 5, characterized in that the confirmation message is sent by the resource management after receipt of the resource reservation message if the traffic diversion does not affect traffic that is subject to compliance with quality of service parameters (QoS), and by the resource management the confirmation message is sent after the resource reservation has been made if the traffic diversion relates to traffic which is subject to compliance with quality of service parameters.

9. The method according to any one of the preceding claims, characterized in that

- The resource management of the routing domain (AS4) in which the network element (R45) is located comprises a resource management process (RM45) which runs on the network element (R45), and

- An interface on the network element (R45) for communication with the resource management process (RM45) is given.

10. The method according to any one of the preceding claims, characterized in that - The network element (R45) is given by an edge node.

11. The method according to any one of the preceding claims, characterized in that

- In the routing domain (AS4) in which the network element (R45) is located, there are at least two resource management processes (RM45, M43, RM42), and

- Two resource management processes (RM45, RM43) communicate with each other to reserve resources.

12. The method according to any one of the preceding claims, characterized in that

- The resource management of the routing domain (AS4), in which the network element (R45) is located, comprises at least two resource management processes (RM45, RM43, RM42), and

- An assignment of network elements (R45, R43, R42) to resource management processes (RM45, RM43, RM42) is given.

13. The method according to claim 12, characterized in that

- The assignment of network elements (R45, R43, R42) to resource management processes (RM45, RM43, RM42) is held on a central server.

14. The method according to any one of the preceding claims, characterized in that

- When a part of the traffic routed via another route is diverted, a reservation corresponding to the entire traffic is first made and then the reservation is adjusted in accordance with the diverted part.

15. edge node (R45) of a communication network, with means for carrying out a method according to one of the preceding claims, characterized in that the means - a routing process (IDR45) for defining InterDomain routes,

- a resource management process (RM45), and

- Include an interface for the exchange of messages between the two processes.

16. Server to support a method according to claim 12 or 13, characterized in that an allocation of network elements (R45, R43, R42) to resource management processes (RM45, RM43, RM42) is provided in the server.

17. Server according to claim 16, characterized in that the network elements (R45, R43, R42) are given by edge nodes.