DE10340809A1 - Optimization of route determination within network with multiple way editing e.g. for real time traffic in packet based network, involves routing to alternative route based on criterion of topology of communications network - Google Patents

Abstract

The method involves routing to an alternative route based on a first criterion of the topology of a communications network. From the alternative group a selection is made for a further criterion so that selected goals are specified. Three or more different routes are prepared based on the first criterion of the topology of the communications network.

Description

The The invention relates to a method for defining path sections for the Routing in a packet-based communication network formed with nodes and links with multipath routing.

The Improvement or optimization of packet-oriented networks, above all in terms of real-time traffic is an important field of work for switching technicians, Network specialists and Internet experts.

Currently intensive work is being done on packet-oriented networks and in the process especially the Internet Protocol (IP) based Internet for the transmission of real-time traffic, such as B. to develop voice or video data. For the Acceptance of a real-time service by the service user is crucial that certain so-called quality of service characteristics are met can. In English is for this property is the term "Quality of Service "- abbreviated QoS - common approaches to a strict control of the user claimed Bandwidth, e.g. by means of routing (MPLS: Multi Protocol Label Switching) in conjunction with bandwidth reservations (RSVP: Resource Reservation Protocol), there are complementary or alternative efforts, the operation of the conventional Internet to improve.

in the usual Internet finds routing within network domains or autonomous systems e.g. using the OSPF (Open Shortest Path First) protocol. Usually is determined by means of a metric, that is, fixed routing criteria, an in For this metric optimal path for routed through the routing domain Determines packets and the routing tables of the individual nodes of the Network according to these determined paths (often by means of so-called link-state messages as part of the linked-state routing). In a routing table is then usually for a particular destination given by the destination address of the packet, an address for the next Hop or the next Station or the next Assigned jump. A router receiving a packet evaluates those in the packet header integrated address destination information, determines the address for the next Hop or next Jump and forward the packet to the appropriate router or node further. In this way, the packages will hop through hop, so to speak the network or the routing domain taught.

One important approach to improve routing within packet-oriented Nets is the so-called Mehrwegerouting, often with the English Expression "Multipath Routing "is called. It provides for packets along two or more paths within a routing domain too to send to a destination. Multipath routing brings in two ways an important improvement to traditional routing. On the one hand can be done by distributing packages in several different ways a better and more efficient utilization of the network can be achieved. The case of unequal burden frequently occurring bottlenecks, which leads to delays and the throwing of packages can be so much less likely. On the other hand, multipath routing can also for a quick reaction to disturbances or failures be used within the network. Distributed in regular operation a node the traffic in the direction of a goal evenly or according to certain distribution weights on the available travel fans. One route fan is there by outgoing links from the node - in the German-speaking Literature also called edges - given on the packages one Flows are distributed. If a link fails, the node picks up the affected path from the Weefächer and distributes the traffic according to the remaining ways around. It can for quality traffic a Ensure acceptance control with suitably calculated acceptance thresholds, that only so much quality traffic is allowed in the network that the remaining after an error route fan actually this traffic can carry. The net thus offers a planned reserve, the in case of error, the traffic in compliance with the promised quality of service takes over (and in normal operation by lower priority traffic classes - e.g. effort traffic - to be availed can).

For IP networks under the second version of the OSPF Protocol (see RFCs 2328, 2178, 1583, 1247, 1131) provided protocols along several paths in the Meaning of a metric of equal length have to transport. This protocol extension is under the abbreviation ECMP (Equal Cost Multi Path) known in the art. It takes place in Within this concept an equal distribution to the different ones Paths that are also the same length, or the same cost is suggested.

• • Verkehrskontrollen am Netzeingang und Netzausgang
• • Übertragung von Verkehr von einem Eingangspunkt zu einem Ausgangspunkt entlang mehrerer Wege (Mehrwegerouting)
• • Verteilung auf verschiedene Wege und Umverteilung bei Störungen durch lokale Routingentscheidungen

Another multi-routing-based approach to improve intra-area routing is being developed as part of the KING (Key Components for the Mobile Internet of Next Generation) project. In the KING project, the information required centrally or at the edge of the network is greatly reduced in comparison to conventional methods with bandwidth reservation, in that routing decisions are essentially carried out locally, as in the conventional IP network. Network-wide states do not have to be maintained. Crucial points of the concept are:

• • Traffic controls at the network entrance and net output
• • Transmission of traffic from an entry point to a starting point along multiple paths (multipath routing)
• • Distribution in different ways and redistribution in case of disturbances due to local routing decisions

The The idea behind the concept is that at the network borders only the aggregated ones Traffic volumes are controlled. The distribution within the Net is by appropriate local measures in the sense of avoidance bottlenecks guaranteed.

As a general rule is multipath routing method in packet networks common that fixing the routes for Multipath routing is an important factor for efficient traffic distribution represents.

The Invention has the task of defining routes in a network to optimize with multipath routing.

The The object is solved by the subject matter of claim 1.

The The basic idea of this invention is, in the route determination next to criteria first order, such as Topology and link metrics (e.g., in conjunction with the Left assigned weights), a second order criterion which is always used when the First-order criteria Choices to let. So far, a random selection has been made in such situations. A possible Second order criterion is e.g. the distribution of traffic or the respective link utilization.

For example would in an O2 routing method (i.e., a method which has two secondary links per node), which in one step at a node three (or more) continuing way possible has determined the two actually paths to be included in the multipath route, e.g. selected according to the lowest relative link load.

in the Framework of the method according to the invention be several for the routing to a destination (e.g., by an edge node of the network may be given) alternative links based on a first criterion determines or identifies the topology of the communication network. In these equivalent Links are e.g. around links leading from the same node, which for the routing to the destination can be used. From this group of alternative On the left, a selection is made based on another criterion. The so selected Links are considered path sections or components of routing routes used to the destination set routing along these routes to the destination.

The Invention has the advantage of better definition of the routes or Ways for the multipath routing. The introduction a second criterion allows the route selection with regard to to optimize this criterion, i. a more efficient routing too guarantee.

advantageous Further developments of the subject invention are specified in the dependent claims.

in the The following is the invention within the scope of an embodiment on the basis of figures closer explained. Show it:

1 : a network formed with nodes and links

2 : a mesh with nodes and links.

In FIGURE is shown a net formed of nodes and links is. Edge nodes r1 ... r10 are as solid circles and inner nodes as unfilled Circles shown. In the context of the embodiment, path sections for a multipath routing selected along routes. Here, between pairs of edge nodes, a selection of path sections for the Routing between the edge nodes done. Exemplary are in the Figure path sections marked by broken arrows. These Path sections define routes between the entrance edge node r1 and the output edge node r7. The path sections or the corresponding Nodes and links were set so that each of the inner Knot two alternatives for the forwarding of incoming from the input edge node r1 traffic to the output edge node r7. These different alternatives Links for The forwarding of an account will be within the scope of the underlying Concept also as a Weifächer or distribution slots designated. A traveling fan can of course also include more than two links. Concentrated for the sake of simplicity the embodiment on moving fans with two path alternatives (also referred to as O2 routing below).

A method to set routes to all egress nodes, which if possible in all internal nodes used for routing to an egress node traversing two alternative routes On the left, the following is sketched:
The method goes through at least all the output edge nodes. If the network is not a pure transit network, the process can also go through all the nodes of the network, with the respective sink or destination node assuming the role of the outgoing edge node (in the case of transit traffic). For a given output edge node, two alternative links are determined for all inner nodes on which the node can forward traffic to the outgoing edge node. For the determination of the links on the left, it makes sense to divide the inner nodes into classes, depending on how many links have to be passed along the route with the minimum number of links in order to reach the respective exit node. The nodes directly connected to the output edge node would then be of class 1, the nodes connected to the output node via these nodes would be of class 2, etc. This classification into classes allows a systematic in the definition of links used for the routing to the output edge node which avoids the circling of packets. In this case, links to the output node are primarily set to nodes of the lower class and possibly to nodes of the same class, but not to nodes of the higher class. The method also provides an order in which the distribution slots for the inner nodes are determined, in which, after the distribution compartments have been determined, the nodes of a class are made the determination for the nodes of the next higher class. It will be described below how, in the context of the method outlined above, the method according to the invention is used for the definition of distribution compartments. The totality of the Weufächer or links intended for an output node is also referred to below as a Hammock Set.

There are in 2 an edge node or destination node A and inner node B ... H shown. In accordance with the method outlined above, traffic fans are defined for traffic to be conducted to the outgoing edge nodes or destination nodes A, respectively. This determination starts at the class 1 (B; C, D, E) nodes and then continues for the class 2 (F, G) nodes. For nodes of higher classes (eg H) the procedure can then be applied analogously as for the nodes of class 2.

at the determination of the Weufächer for multipath routing to the destination node A according to the invention a two-stage process proposed.

• – in einem ersten Schritt für jeden Knoten, der noch nicht O2-fähig ist (d.h. der noch keinen zwei Links umfassenden Wegefächer aufweist), alle durch die Netz-Topologie möglichen Links bestimmt, die diesen Knoten O2-fähig machen würden (sofern es mindestens 2 sind).
• – In einem zweiten Schritt werden dann aus den gefundenen möglichen Links auf Basis des Verkehrs im Netz oder eines anderen sinnvollen Kriteriums ein Paar von Links bestimmt, das für das Routing herangezogen werden soll.

Starting from an inner ring around the respective destination node (eg the destination node A), for all other network nodes:

• In a first step, for each node which is not yet O2-capable (that is, which does not yet have two links compartments) determine all links possible by the network topology which would make that node O2-capable (if at least 2 are).
• In a second step, a pair of links to be used for the routing is then determined from the possible links found on the basis of the traffic in the network or another sensible criterion.

That usually more than two possible ones Selected links. From the selected Two links are then set based on secondary criteria.

This procedure is based on the in 2 shown network section explained in detail. For a hammock set to calculate, let A be the target (eg a network seed node). The neighbors of A (hereinafter referred to as ring nodes), ie the nodes B, C, D and E, which are connected to A via the dotted drawn links (hereinafter referred to as star-links) are also interconnected, in 2 represented by dashed lines (hereinafter referred to as ring links). Although the interconnection of all ring nodes with each other is a prerequisite for the O2 / 1 capability of the network (O2 multipath routing with exactly one joker link (ie a link through which traffic can be routed in both directions) per hammock Set), but not a requirement for the applicability of the invention.

in the Below is the selection criterion for the second step, the traffic load the links chosen.

Ring 1:

It will be first the inner ring around A (here referred to as Ring_1), ie the ring nodes B, C, D, E as well as the ring links and the star links. To O2 ability can reach any ring link as a so-called Joker or Joker link selected become.

It is not possible to provide two outbound links to each of the ring nodes for routing to the destination A, and the links should not lead to a higher-class node, and at the same time, preclude the circling of packets. Therefore, a link is defined (Joker), over which traffic is usually directed in one direction, but in a well-defined accident in the other direction (to the same destination) can be operated. In 1 the joker link is marked with the letter J It may also be an advantage to make all ring links joker links for greater flexibility in case of failure.

For example, it is proposed to make that ring link to the wild, whose adjacent star links lead the least traffic. If I and J are the endpoints of a ring link, the joker for the hammock set to destination A is determined as follows:
Link ij = Joker if T = TLink_i_A + TLink_j_A + k1 * (T_i_A + T_j_A) the minimum over all i, j is the set of (directly connected) ring nodes B, C, D, E.

• • TLink_i_A der Verkehr auf dem Link i-A vor der Berechnung des Hammock-Sets nach A (d.h. der für die bereits berechneten Hammock-Sets ermittelte Verkehr)
• • TLink_j_A der Verkehr auf dem Link j-A vor der Berechnung des Hammock-Sets nach A
• • T_i_A der Verkehr des Knotens i nach A (d.h. der im Knoten i generierte Verkehr, der nach A geschickt wird)
• • T_j_A der Verkehr des Knotens j nach A
• • k1 ein Faktor, der zwischen 0 und 1 liegt. Er kann z.B. bei einem O2-Hammock-Set starr zu 0.5 gewählt werden, oder aber auch abhängig vom berechneten Hammock-Set. So kann z.B. durch Wahl von k1 = (i/n) der zu hohe Einfluss von lokalem Verkehr bei der Berechnung der ersten Hammock-Sets kompensiert werden. Dabei ist n die Anzahl der Knoten im Netz und i kennzeichnet, dass der Hammock-Set für den Knoten i (1 < = i< = n) berechnet wird. Eine andere Wahl von k1, z.B. auf Basis der Verkehrsmatrix, ist ebenso möglich.

Where:

• TLink_i_A the traffic on the link iA before the calculation of the Hammock set after A (ie the traffic determined for the already calculated Hammock sets)
• • TLink_j_A the traffic on link jA before the hammock set is calculated to A
• T_i_A the traffic of node i to A (ie the traffic generated in node i which is sent to A)
• T_j_A the traffic of the node j to A
• • k1 is a factor between 0 and 1. For example, it can be set to 0.5 for an O2 Hammock Set, or depending on the calculated Hammock Set. For example, by choosing k1 = (i / n), the excessive influence of local traffic in the calculation of the first hammock sets can be compensated. Where n is the number of nodes in the network and i indicates that the hammock set is calculated for node i (1 <= i <= n). Another choice of k1, eg based on the traffic matrix, is also possible.

There first the hammock sets are not known, but gradually one after the other can be determined when calculating the hammock sets to a destination node m the respective values of TLink also not from the beginning consider the full traffic on the links but only in the previous runs to the node (destination) m-1 calculated traffic.

The Procedure ensures that the joker is between the star links with the least traffic being laid, so traffic for that anyway stronger loaded links can be distributed according to the O2 principle. For the remaining ring nodes leaves the Demand for O2 capability no freedom for the application of secondary Criteria.

Ring k

• T_i_j ist dabei der Verkehrsbeitrag des Knoten i über den gerade betrachteten Link zu Knoten j, wobei j ein bereits im Hammock-Set enthaltener Knoten ist, an den i angebunden werden kann.
• • T_link ist der bereits auf dem betrachteten Link laufende Verkehr Für den Faktor k2 gilt das bei Ring 1 für den Faktor k1 Gesagte.

After that, the O2 routing is calculated for all further outlying nodes in the network, ie in Figure 1 for the nodes F, G, H which successively become "O2-reachable". Similar to Ring 1, for a given node i (here, F, G, H) for all possible 2-link combinations that would make node i a new O2 node, the two links with the least traffic become T = T_link + k2 * T_i_j selected and added to the hammock set.

• T_i_j is the traffic contribution of the node i over the currently considered link to node j, where j is a node already contained in the hammock set to which i can be connected.
• • T_link is the traffic already running on the link under consideration. For the factor k2, what has been said with ring 1 for the factor k1 applies.

With the described method ("Ring 1 ", ring k") are successively all hammock sets calculated. Since the algorithm at each destination node of a Hammock set starts, can the traffic contributions not yet included node in the direction of the destination node, too not included in the determination of link loads. For the approximation of LinKlast as a criterion second order will therefore only the direct traffic contribution, the is created or generated by the currently considered link / node, underlying (T_i_j and T_i_A each describe the direct Traffic relations of the considered neighboring nodes). Indeed after each pass, after determining each hammock set, to prepare for the next Round the previously accumulated link loads T_link in the network exactly calculated, what with knowledge of hitherto calculated Hammock sets and the traffic matrix, as well as e.g. assumed equal weight Distribution weights possible is.

By This routing will significantly increase the load on the links of the network and also a smaller shift of the load with link failures.

• • Die Verwendung der relativen Verkehrslast als Kriterium zweiter Ordnung, also der auf die Link-Bandbreite bezogenen Verkehrswerte T. Dadurch wird in einfacher Weise die Berücksichtigung von unterschiedlichen Link-Bandbreiten in O2-Netzen möglich.
• • Die Verwendung von Kosten-Funktionen bei der Auswahl der Links bzw. des Jokers. Kosten-Funktionen können z.B. im Sinne einer optimierten gleichmäßigen Verkehrsverteilung oder das Preis/Bandbreite Verhältnis eines Betreibers sein.
• • Die Verwendung von Faktoren k1 bzw. k2 proportional zu (i/n)^x, wobei i der Knoten (Ziel A) ist, für den gerade der Hammock-Set berechnet wird und n die Gesamtzahl der Knoten im Netz. Dadurch wird vermieden (z.B. mit x = 1), dass für die ersten Hammock-Sets der lokale Verkehr zwischen zwei Nachbarn zu stark bewertet wird.
• • Die unabhängige Verwendung der für Ring 1 bzw. Ring k vorgeschlagenen Verfahren. So kann es zweckmäßig sein, im Ring 1 mehrere Joker zu verwenden, um einen hohen hopcount für bestimmten Verkehr zu vermeiden. Mehrere Joker in Ring 1 verhindern, dass Pakete über eine längere Kette von Ring-Links gesendet werden. Dann kann trotzdem sinnvoll das vorgeschlagen Verfahren für die äußeren Ringe verwendet werden.
• • Auch im Fall von mehreren Jokern in Ring 1 kann sinngemäß verfahren werden, wie hier für einen Joker vorgeschlagen.
• • Die Verwendung etwa anfallender verkehrsabhängiger Kosten als Kriterium zweiter Ordnung.
• • Die Verwendung etwa unterschiedlicher Link-Verfügbarkeit als Kriterium zweiter Ordnung.

Appropriate additions or alternatives to the procedure presented in the context of the exemplary embodiment are:

• The use of the relative traffic load as a second-order criterion, ie the traffic values T related to the link bandwidth. This makes it possible to easily consider different link bandwidths in O2 networks.
• • The use of cost functions when selecting links or jokers. Cost functions can be eg in the sense of an optimized even traffic distribution or the price / bandwidth ratio of an operator.
• • The use of factors k1 and k2, respectively, proportional to (i / n) ^x , where i is the node (target A) for which the hammock set is currently being calculated and n is the total number of nodes in the network. This avoids (eg with x = 1) that the local traffic between two neighbors is overestimated for the first hammock sets.
• • The independent use of the procedures proposed for Ring 1 or Ring k. So it may be useful to use multiple wild cards in ring 1 to avoid a high hopcount for certain traffic. Multiple wildcards in ring 1 prevent packets from being sent over a longer chain of ring links. Then, nevertheless, the proposed method for the outer rings can still be used meaningfully.
• • In the case of several Jokers in Ring 1, the same procedure can be followed, as suggested here for a Joker.
• • The use of any traffic-related costs as a second-order criterion.
• The use of some different link availability as a second-order criterion.

Further Criteria for selection, such as the running time of the links, the load capacity (Capacity) the end nodes of the new links etc. are also conceivable. A additional Improvement of traffic distribution through a specific order when editing the node is also possible.

The proposed methods of selection according to the criteria listed is synonymous for others Algorithms for calculating Hammock Sets applicable.

Claims (11)

Method for determining route segments for routing in a packet-based communications network formed with nodes and links with multipath routing, as a result - several for routing to a destination alternative links based on a first criterion of the topology of the Communication network determined / identified, and - from the Group of alternative links a selection of links based on a further criterion is made, and - the links selected as pathways for a Routing along paths to the destination. Method according to claim 1, characterized in that that three or more for routing to a destination alternative links based on a first Criteria of the topology of the communication network determined / identified become. Method according to one of claims 1 or 2, characterized that the first criterion by the topology of the communication network or given by a link metric. Method according to one of the preceding claims, characterized characterized in that the further criterion by the traffic load the links, the bandwidth of the links, the available bandwidth of the links, The relationship too traffic to bandwidth, cost functions, availability the links, the load capacity of the links bounding nodes or the duration of packages is given on the links. Method according to one of the preceding claims, characterized that is more than an additional additional criterion for the Selection of links is used. Method according to one of the preceding claims, characterized marked that - the Determination of alternative links takes place knot-related, and - for each the node a fixed number of links is selected when the number of alternative links larger or is equal to the fixed number. Method according to Claim 6, characterized that the fixed number is equal to 2. Method according to one of claims 6 or 7, characterized that one of the selected Links are used as the wildcard link, i. used for routing only if at least one of the alternatives is on the same node related links fails. Method according to claim 8, characterized in that that all links between for The routing to a destination used neighboring nodes of the destination as wild links be used. Method according to one of the preceding claims, characterized marked that - the Definition of path sections for Routing to a destination based on a destination considered Node is made, - too leading to this destination node Left or path sections selected be, and - successively for inner Nodes from which links selected as way sections of paths to the destination a selection of this node related to this node leading Links take place. Method according to one of the preceding claims, characterized marked that - the Communication network is an IP (Internet Protocol) network.