EP1825643A1

EP1825643A1 - Aggregation of inter-domain resource signalling

Info

Publication number: EP1825643A1
Application number: EP05821733A
Authority: EP
Inventors: Thomas Engel; Thomas Schwabe
Original assignee: Nokia Siemens Networks GmbH and Co KG
Current assignee: Nokia Solutions and Networks GmbH and Co KG
Priority date: 2004-12-07
Filing date: 2005-12-07
Publication date: 2007-08-29
Also published as: CN101073229A; WO2006061394A1; CA2591302A1; DE102004058927B3; US20080107127A1

Abstract

The invention relates to a method for aggregating or combining signalling messages for the adaptation of resource reservations required for route modifications. According to said method, a modification of an inter-domain route requiring an adaptation of resource reservations is disclosed to a first routing domain (AS1). Said first routing domain (AS1) communicates the modification of the inter-domain route to at least a second (AS2) and a third (AS3) routing domain. Resource reservations adapted according to the route modification are then disclosed by the second (AS2) and the third (AS3) routing domains to the first routing domain (AS1) and are combined in order to be transferred to a fourth routing domain (AS8). According to one form of embodiment, a timer is used to define the period of time for combining reservation messages, in order to be able to transfer modified reservations in a more efficient manner. The invention enables a technically simple and efficient modification of resource reservations in the event of route modifications.

Description

description

Aggregation of inter-domain resource signaling

The invention relates to a method and a device for the efficient adaptation of resource reservations during route changes in the context of inter-domain routing.

Inter-domain routing, and the signaling required for this purpose, are particularly demanding where a large number of networks in a network network interact in an end-to-end transmission and at the same time guarantee quality criteria for the transmission should be. The most important example of such a scenario is the transmission of real-time traffic over the Internet Protocol based on the IP protocol.

In the future, IP networks will also support applications that include the transmission of voice, video and data streams that require fast and reliable transport of IP packets. Current development activities aim to ensure that future IP networks provide new transmission services in addition to the traditional "best effort" service, which will provide traffic with the bandwidths required and reliably transport IP packets to the receiver with little, little lag and very low packet loss rates. A network equipped to implement these new transmission services is also referred to as NGN (Next Generation Network). Traffic that is transported as part of these services is also referred to as QoS (Quality of Service) traffic. Today's Internet is an amalgamation of a growing number of individual IP networks, so-called autonomous systems (AS) or routing domains, managed and controlled by different organizations. At present, the Internet consists of more than 15,000 autonomous systems. Similarly, in future, NGNs will be merged into a network and QoS services will be offered across networks.

In order to provide QoS services, the resources required for them must be reserved not only within an NGN but also on the connections between the NGNs. There are currently two proposals for an inter-domain resource signaling protocol, the Border Gateway Reservation Protocol (BGRP, Pan, P., E. Hahne, H. Schulzrinne: "Sink-Tree-Based Aggregation for Interdomain Reservations", Journal of Communications and Networks, Vol. 2, No. 2, pp. 157-167, http://www.cs.columbia.edu/~pingpan/papers/bgrp.pdf, June

2000) and the Inter-domain Control Aggregation Protocol shared segment (SICAP, R. Sofia, R.Guerin and P.Veiga: "SICAP, a Shared-segment Inter-domain Control Aggregation Protocol", High Performance Switching and Routing, HPSR 2003, Turin, Italy, June 2003). Both protocols differ mainly in their aggregation behavior.

In this context, aggregation is understood to be the pooling of reservations for different QoS traffic streams, that is to say of individual connections or of smaller aggregates, to a common reservation. The traffic streams combined with the aggregation of reservations then form an aggregate for this purpose only a single reservation needs to be managed. At BGRP, all reservations are grouped together to one destination. SICAP additionally aggregates on intermediate sections of the end-to-end paths.

The aggregation of inter-domain reservations is necessary to limit the number of necessary reservations for QoS traffic between the very large number of different autonomous systems so that they can be transmitted and processed with reasonable computing and memory overhead in a suitable time. If the route changes to a destination, then the aggregates of the QoS traffic, which is transported via the changed route, must be resolved, since the route change can cause aggregates to lose their validity. After route changes, the traffic streams that have previously formed an aggregate can run on different routes and thus require new aggregates. Reasons for a route change may be the failure of a connection or overload on the connection used. In order to dissolve the aggregates, messages are sent to all the sources involved and the persons concerned have to adapt their reservations to the new routes.

It is an object of the invention to provide a low-cost and efficient method for the adaptation of resource reservations for route changes in the context of inter-domain routing with respect to the signaling load.

According to the invention, it is proposed to summarize resource reservations in the case of a route resolution and consequent relocation or diversion of traffic in order to design the signaling as efficiently as possible. In the course of the invention, when a route is changed in the context of inter-domain routing, a first routing domain is notified of a change in an inter-domain route (this can be both a withdrawal of an inter-domain route or the notification of a changed inter-domain Act route), which requires an adjustment of resource reservations. The first routing domain then shares this change, eg in the form of a route change message (eg UPDATE message of the BGP protocol) of at least one second and one third routing domain, but preferably all adjacent routing domains from which QoS traffic over the first one With the routing domain along the route affected by the change. From the second and the third routing domain, in each case, the first routing domain is signaled a resource reservation adapted in accordance with the route change, which, for example, requests resources along an alternative route or new route. These signaled resource reservations are aggregated and further communicated from the first routing domain, typically to a fourth routing domain, from which the route change was originally communicated to the first routing domain.

The invention has the advantage that resource reservations combined are further communicated and thus the signaling effort is optimized. The number of signaling messages when dissolving and rebuilding an aggregate are thus significantly reduced.

The procedure according to the invention can lead to a delay of

Resource reservations lead, for example, when the signaled by the second routing domain resource reservation arrives with a delay, whereby the summary of the resource reservations of the routing domains two and three is delayed forwarded. In this case, the resource reservation of the third routing domain takes place with a delay, which can be achieved without aggregation or cooperation. the reservation would not be available. Because of this difficulty, it is proposed according to a further development to introduce a timer or timer and to summarize only within the running time of the timer received resource reservations. If all resource reservations are received within the runtime of the timer, they can be forwarded together (possibly even before the timer expires). Otherwise, only the resource reservations received during the runtime of the timer will be forwarded in an aggregated form. Subsequent resource reservations can then not be aggregated as single reservations or communicated further.

It makes sense to tell the routing change from the first routing domain along existing inter-domain routes to the routing domains that have reserved resources along routes that pass through the first routing domain to a common destination and are affected by the route change. This results in a route tree of routes that are communicated by the first routing domain the route change. According to an embodiment of the subject of the invention, upon reversion when passing the tree with changed resource reservations at the routing domains that are not a "leaf node", ie, not an endpoint, an aggregation of the resource reservations according to the invention is performed. For example, the root of a route tree or a plurality of routes, which determines which route reservations can be aggregated, is given by a routing domain that represents the end point of the routes, but it is also conceivable that it may not is a routing domain, but a network - for example, defined by a particular address - which can form part of a domain.Also, the destination is not necessarily the endpoint of routes, but may be a suitably chosen waypoint selected, along a route te, lying domain. For example, an aggregation of reservations that is not limited to the endpoints is also provided for in a context different from that of the application in the SICAP protocol.

The above embodiment of the subject invention can be advantageously extended, not only in the first routing domain, but also in other routing domains, which are notified of the route change on the first routing domain and which do not form the end point of a route, also a timer for aggregation of Resource reservations start. For example, a timer can also be started in the second routing domain; Preferably, however, timers are started in all routing domains, which are informed of the routing change from the first domain and which then receive resource re-reservations from more than one domain to the same destination.

When using multiple timers, it is beneficial to synchronize the timers. By such a vote is to be achieved that if a routing domain, which summarizes the previously received resource reservations to a reservation after the expiration of their timer and this signals a subsequent routing domain with respect to the changed route, the timer of this routing domain has also not yet expired, so that the signaled (aggregated) route reservation can be aggregated or combined with further route reservations. Therefore, it is appropriate to run the duration of a timer

Routing domain shorter than the duration of the timer to choose the routing domain, then the aggregated route reservations are signaled.

In a preferred embodiment, such a tuning of the duration of the timer takes place for all routing domains that aggregate route reservations and with it Timers work. This results in a kind of timer cascade or timer interwall nesting, where the duration of the timer becomes shorter the further one approaches the endpoints or leaf nodes in the route tree. In general, the time it takes to run a timer will be shorter the later it starts. A vote of the timers on each other can be done by exchanging information that is part of the route change message, for example. This information may include, for example, the duration of the timer, which, together with the transmission time of the message, which is often already provided by the protocol, for example in the form of a time stamp (Time Stamp) used to determine a suitable duration for the timer , Other solutions are also conceivable, for example, one can also imagine that there are empirical values for a suitable duration of timers in accordance with the distance of the routing domain from the tree located furthest forward in the tree. In this embodiment, for example, a domain which is located in third place with respect to the routing domains using the timers must only forward the information to a subsequent routing domain that it is located fourth, so that it selects the runtime provided for this position.

The invention also includes a device, e.g. B. a router, with means for performing a method according to the invention.

In the following, the subject invention is explained in more detail in the context of an embodiment with reference to figures.

Show it

FIG. 1 Routing domains with resource reservation aggregation for routing to a destination network N1. FIG. 2 shows the routing domains shown in FIG. 1 with an aggregation according to the invention of new route reservations in the case of a change of routes leading to the destination N 1.

1 shows the disadvantages of the procedure according to the prior art. The basic procedure for aggregation and deaggregation of BGRP and SICAP is very similar and thus has the same problem that is solved in this application. Therefore, only BGRP is considered below.

Fig. 1 shows an example of aggregation of reservations corresponding to BRGP. In the network network shown, each of the four autonomous systems AS4, AS5, AS6 and AS7 has each set up a reservation to the destination network N1. The reservations start with the reservations Fl, F2, F3 and F4 between one of the autonomous systems AS4, AS5, AS6 and AS7 and AS2 or AS3 and are combined step by step into larger aggregates. The autonomous system AS2 has combined the two reservations Fl and F2 from the autonomous system AS4 or the autonomous system AS5 to the aggregate A1 in the direction of AS1. Analogously, the autonomous system AS3 has combined the two reservations F3 and F4 from the autonomous system AS6 or the autonomous system AS7 to the aggregate A2. The autonomous system ASl has again combined the two units Al and A2 into a larger aggregate A12. Based on the reservations Fl, F2, F3 and F4, this creates a tree-like system of reservations, which will be referred to below as a reservation tree. Each of the autonomous systems AS4, AS5, AS6 and AS7 uses its reservations Fl, F2, F3 and F4 for the entire QoS traffic with destination addresses with the prefix 10.10.10.0/23. In this example, it is assumed that on the direct link between ASl and the destination network Nl the load of the QoS traffic exceeds a limit set by the network management and therefore part of the aggregate A12 is to be routed via AS8 to the destination network. For this purpose, the prefix 10.10.10.0/23 is split into the two prefixes 10.10.10.0/24 and 10.10.11.0/24, as shown in FIG. 2, and forwarded via the routing protocol to all affected autonomous systems corresponding routing messages. Then all autonomous systems (AS1-7), whose QoS traffic is part of the aggregate A12, must adapt their reservations to the prefix 10.10.11.0/23 to the new path via AS8. Via the routing protocol, at least one new route with the prefix 10.10.11.0/24 is made known, which leads from the autonomous system AS1 via the autonomous system AS8 to the network N1. In order for the traffic to this prefix of the excessive load direct connection between the autonomous system ASl and the destination network Nl to the path of the autonomous system ASl on the autonomous system AS8 to the destination network Nl be allocated. The resource management of the autonomous system ASl responds to the new route and sends a message to the autonomous systems AS2 and AS3 with the request that they rebuild their existing reservations. The autonomous systems AS2 and AS3 subsequently send a message to their neighbors, the autonomous systems AS4, AS5, AS6 and AS7. So these messages go back in the opposite direction to the existing reservations on the reservation tree from the root to the leaves, ie to the nodes where the individual reservations start. From there, new reservations are being set up. Due to the changed routing, the autonomous system AS4 divides its reservation Fl into two reservations Fla and FIb corresponding to the traffic to the two prefixes 10.10.10.0/24 and 10.10.11.0/24, which are now reached via different routes. The autonomous systems AS5, AS6 and AS7 react analogously and two new reservation trees are created.

Back signaling on the reservation tree and rebuilding all reservations will generate a very large number of signaling messages in the real Internet, where much larger reservation trees are created.

The procedure according to the invention is illustrated below. After splitting the prefix 10.10.10.0/23 into the two prefixes 10.10.10.0/24 and 10.10.11.0/24, corresponding routing messages are forwarded via the routing protocol to all affected autonomous systems. Then all autonomous systems (AS1-7), whose QoS traffic is part of the aggregate A12, must adapt their reservations to the prefix 10.10.11.0/23 to the new path via the autonomous system AS8. The autonomous system AS1 notices the changed routing at a time Tl. The autonomous system ASl then sends to all neighbors whose reservations the aggregate A12 is made at time T1, i. to the autonomous systems AS2 and AS3, a message that causes them to check the reservations according to the changed routing and to respond with new reservations to the autonomous system AS1. According to the invention, the autonomous

System ASl then answers the notified autonomous systems AS2 and AS3 and monitors with a timer the maximum response time. The autonomous system ASl waits for four reservations, one each for the two prefixes 10.10.10.0/24 and 10.10.11.0/24 from the autonomous system AS2 and from the autonomous system AS3. Let T2 be the time when either all expected responses have arrived or the timer has expired (the earlier of the two events). In the Meanwhile: ΔTl = T2 - Tl, the autonomous system ASl sets up two new aggregates according to the incoming reservations: one aggregate for the direct connection to Nl (prefix 10.10.10.0/24) and for the path via the autonomous system AS8 (prefix 10.10.11.0/24). In accordance with the invention, incoming signaling messages relating to reservations of the resolved aggregate A12 at time Tl during ΔTl are not signaled further in the direction of the destination. Only new reservations that are not part of the resolved aggregate A12 at the time Tl are treated as usual. The assignment of incoming reservations to the dissolved aggregate A12 is done via a unique identifier which was sent by the autonomous system AS1 with the resolution message to the autonomous systems AS2 and AS3 and is contained in the returning responses. Only at time T2 does the autonomous system AS1 signal the two new aggregates in the direction of the destination network N1.

The autonomous systems AS2 and AS3 react according to the invention as the autonomous system ASl on the message to rebuild the reservations of the aggregate A12. Only when the autonomous system AS2 has ever received a new reservation for the two prefixes 10.10.10.0/24 and 10.10.11.0/24 from AS4 and AS5, or a corresponding timer has expired, the autonomous system AS2 sends two reservation messages to the autonomous System ASl, one for each of the two prefixes. The autonomous system AS3 reacts analogously. If no resources are to be reserved for a prefix, then a reservation can be made with the value 0 so as not to have to wait for the timer to expire.

Starting from the first signaling message with which the autonomous system ASl at the time Tl rebuilding the Reservations of the A12 aggregate, the new procedure requires a total of 6 + 12 signaling messages (6 for dissolving the aggregates between AS4, AS5, AS6, AS7 and ASl + 12 for rebuilding). Without the new procedure, 6 + 24 signaling messages will be needed. In particular, the load of the autonomous system ASl decreases with the new method from 8 answers to 4, thus halving itself in this small example.

It makes sense to match the running time of the timers to each other. Thus, the autonomous system ASl starts a timer and sends a message to the autonomous systems AS2 and AS3. Autonomous system AS2 then starts a timer again and sends a message to the autonomous systems AS4 and AS5. Assuming that the autonomous system AS4 does not respond in time, the timer of the autonomous system AS2 will expire. The autonomous system AS2 sends the reservations AIa and Alb to the autonomous system ASl. If the timers of the autonomous systems AS2 and AS3 comprise the same time period, then the timer has already expired from the autonomous system AS1, that is, the reservations from the autonomous system AS2 are no longer taken into account in the aggregation. This can be prevented if the time periods of the timers are adjusted to each other or adjusted (the farther in the tree, the shorter). This can be realized, for example, by inserting the time span of the timer in the messages between the autonomous systems. For example, the autonomous system AS1 informs the autonomous system AS2 of the duration of its timer, and the autonomous system AS2 then selects a shorter duration, which allows the reservation messages to be sent before the autonomous system timer ASl expires. This shorter duration of the timer takes into account the duration of the messages exchanged between the autonomous system AS1 and AS2. The duration is then at least twice the duration of exchanged messages less (duration of the route change message + duration of the message with the aggregated reservations).

Claims

claims

1. A method for the efficient adaptation of resource reservations for route changes in the context of inter-domain routing, in which

a first routing domain (AS1) is notified of a change of an inter-domain route which requires an adaptation of resource reservations; by the first routing domain (AS1) the change of the inter-domain route of at least one second (AS2) and one third (AS3 ) Routing domain is communicated,

- By the second (AS2) and the third (AS3) routing domain each of the first routing domain (ASl) is signaled in accordance with the route change resource reservation, and

at least the two resource reservations signaled by the second (AS2) and the third (AS3) routing domains are summarized by the first routing domain (AS1) and signaled as a resource reservation of a fourth routing domain (AS8).

2. The method according to claim 1, characterized in that - a timer is started by the first routing domain (ASl) on the notification of the route change, and

- Resource Reservations signaled prior to expiration of the timer and signaled as resource reservation of a fourth routing domain (AS8).

3. The method according to claim 2, characterized in that

- the second routing domain (AS2) signals a resource reservation after the timer expires, and - this resource reservation without further delay as a change to the previous summary of resources Reservations the fourth routing domain (AS8) is signaled.

4. The method according to any one of the preceding claims, characterized in that from the first routing domain (ASL), starting along existing inter-domain routes the route change is communicated to the routing domains, the resources for along over the first routing domain (ASl) to a destination (Nl ) have reserved leading inter-domain routes and in which an adjustment of the resource reservation according to the route change is required.

5. The method according to any one of the preceding claims, characterized in that are summarized by the first routing domain (ASL) all in the wake of the route change signaled resource reservations that affect the traffic along the changed route to a common destination to be transmitted.

6. The method according to claim 5, characterized in that the destination (Nl) is given by a routing domain or a network.

7. The method according to claim 5 or 6, characterized in that

- a timer is started by the first routing domain (ASL) in response to the notification of the route change, and - those of the resource reservations signaled as a result of the route change are summarized, relating to the traffic to be transmitted along the changed route to a common destination and before the timer expires to the first routing domain (ASl).

8. The method according to any one of claims 2 to 7, characterized in that a timer is also started by the second routing domain (AS2),

- resource reservations received before the expiration of the timer are combined and signaled to the first routing domain (ASl).

9. The method according to claim 8, characterized in that the running time of the second routing domain (AS2) started timer is set in such a manner according to the duration of the first routing domain (ASl) started timer that during the running time of the second timer received and summarized at the end of the second timer and the first routing domain (ASl) signaled route changes before the expiry of the first timer at the first routing domain (ASl) arrive.

10. The method according to claim 9, characterized in that the fixing of the running time of the second timer in accordance with one of the first routing domain (ASl) to the second routing domain (AS2) transmitted information is made.

11. Device having means for carrying out a method according to one of claims 1 to 10.