JP2000332777A - Ip label switching communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize highly reliable packet transfer by transferring IP packets, having IP addresses to an ATM network according to labels obtained by converting the IP addresses by sequentially setting a plurality of routes which do not form a loop for the same IP address. SOLUTION: The existence of the congestion of a label switching network and its occurrence place are detected, when there is no congestion, the shortest route among a plurality of routes is selected, and when congestion is detected, 2 or more the routes are selected. At this time, the 2 or more routes selected transfer a series of cells constituting one frame in frame units. Further, more the priority of an IP packet is discriminated and according to the discrimination result, a shorter route is selected out of the 2 or more routes for the IP packet with a top priority than that for IP packets with a low priority.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a technology for label switching an IP packet in a layer 2 ATM network. The present invention provides a Multi Protocol Label Switchi
ng: related to MPLS technology.

[0002]

2. Description of the Related Art In a conventional label switching technique, I
Switching routes used for label switching of P packets are based on shortest path routing. Therefore, the routing algorithm installed in each label switch router in the network calculates the shortest test path.

In such a conventional routing algorithm, link cost information of a network (information including a link distance, a band, a congestion state, and other parameters).
, A routing path that realizes the minimum link cost (show test path) is searched and calculated. It is assumed that the link cost used in calculating the shortest test path is exactly the same at each label switch router in the network and is synchronously maintained.

[0004]

Therefore, recalculating the short test path avoiding the congestion point in consideration of the link cost reflecting the local congestion state requires a large-scale network, and the variable cost is reduced to the entire network. This is basically not possible when it is difficult to synchronize and distribute.

[0005] For this reason, when a local congestion state occurs in an actual network, performing shortest path routing with the minimum hop cost includes a congestion point in the routing path, and further worsens the congestion state. Problems arise. In the conventional label switching technology, since a label switching path addressed to the same IP address is configured using a single short test path, IP packets of different quality classes of the same destination are regarded as information of the same quality class. Therefore, there is a problem that transfer control for each quality cannot be realized by changing the route when congestion occurs. As a result, there arises a problem that QoS (Quality of Services) control of IP traffic cannot be performed.

[0006] The present invention has been made in view of such a background, and an object of the present invention is to provide an IP label switching communication system capable of performing high-speed and high-quality label switching of an IP packet on an ATM network.
In particular, it is an object of the present invention to provide a highly reliable IP label switching communication system that performs multipath label switching while adaptively bypassing a congestion point according to a QoS class in units of frames when congestion occurs. The present invention provides an IP that can realize high-throughput and highly reliable packet transfer in a large-scale and complicated IP network.
An object of the present invention is to provide a label switching communication system.

[0007]

The present invention is characterized in that a label switching path addressed to a specific IP address is set by multipath by sequentially setting labels in an ATM switch in an ATM network in a loop-free manner. And In addition, when congestion occurs in the network, QoS-based route control is performed, in which high-priority traffic and low-priority traffic are discriminated and route control is performed according to the priority.

That is, according to the present invention, an IP packet is transmitted to an ATM by utilizing the high-speed switching characteristics of a layer 2 ATM.
This is a high-speed label switching technology on a network. When mapping an IP address to an ATM address by using a label distribution algorithm, a switching route aiming at the same IP address group can be set at a time in a loop-free manner with a plurality of routes at once including a minimum hop route on an ATM network. This is the first main feature of the present invention.

In the prior art, a plurality of loop-free routes cannot be set on the ATM network. However, according to the present invention, label switching of the minimum hop route is performed normally, and congestion occurs when local congestion occurs. Label switching is performed by multiple routes avoiding points.
At this time, in order to prevent the cell order of the ATM cells in the same connection from being reversed, when label switching is performed using a plurality of routes in consideration of the IP packet, the cells are framed in units of frames including a series of cells on the ATM network. Perform switching.

As described above, the prior art is different from the prior art in that a plurality of routes are adaptively set based on local congestion information. In order to prevent reversal of the order of ATM cells when label switching is performed using a plurality of routes. The difference is that label switching of a plurality of routes is performed in frame units. Further, in the present invention, when there is a possibility that local congestion occurs and cell transfer quality cannot be guaranteed, the cell transfer quality is identified by identifying the priority class of the cell and changing the label switching route for each class. It is characterized by guarantee.

That is, according to the present invention, when local congestion occurs, a cell of a high priority class performs label switching by a normal minimum hop route, and a cell of a low priority class performs label switching by a plurality of routes including a detour. I do. Even ATM cells aiming for the same class of IP address as the conventional technology have A
The difference is that the communication quality for each class can be guaranteed by changing the routing policy in the TM network.

That is, the present invention relates to an IP label switching communication system, and means for holding network topology information composed of label information including VPI and VCI predetermined in correspondence with an IP address and link cost information. Means for converting an IP address and a label according to the network topology information held by the holding means, and an IP packet having the IP address according to the label converted from the IP address by the ATM means. Means for sequentially setting routes to be transferred in a network.

Here, a feature of the present invention resides in that the means for sequentially setting includes means for sequentially setting a plurality of routes that do not form a loop for the same IP address. Thus, for example, when a means for detecting the presence or absence of congestion in the ATM network and the location where the congestion occurs is provided, the shortest route among the plurality of routes is selected when there is no congestion, according to the detection result of this detecting means. And means for selecting a plurality of two or more routes from the plurality of routes when there is congestion.

With this configuration, when there is no congestion, the IP packet is transferred by the shortest route,
When congestion occurs, IP packets can be distributed to a plurality of routes to avoid congestion. At this time, it is preferable that the plurality of routes include means for transferring cells in a frame unit for a series of cells constituting one frame. Thus, the cell order can be prevented from being reversed.

Further, in the case where means for identifying the priority of the IP packet is provided, the means for selecting a plurality of the IP packets according to the identification result of the means for identifying the priority of the IP packet from the two or more routes may be used. For low priority I
A means for selecting a route shorter than the P packet may be included. As a result, transmission quality can be ensured by reducing delay for high-priority IP packets, and routes can be distributed for low-priority IP packets to avoid congestion.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a network configuration assumed in an embodiment of the present invention. FIG. 2 is a diagram showing a protocol stack used in the embodiment of the present invention. FIG. 3 is a diagram for explaining the algorithm operation of the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a multipath realized by a combination of spanning trees starting from a destination. FIG. 5 is a diagram showing a label switch network according to the embodiment of the present invention. FIG. 6 is a diagram showing a label setting correspondence table according to the embodiment of the present invention. FIG. 7 is a diagram for explaining a cell switching procedure according to the separation or connection of the label switching path according to the embodiment of the present invention. FIG. 8 is a diagram showing a multi-QoS control method according to the embodiment of the present invention.

The configuration of the embodiment of the present invention will be described with reference to FIG. The present invention is configured as a label switching network which is an ATM network as shown in FIG. The label switching network shown in FIG.
Means for holding network topology information composed of label information including VPI and VCI predetermined corresponding to the P address and link cost information including link distance, bandwidth, congestion state, and other information;
Means for converting an IP address and a label by the holding means in accordance with the held network topology information, and converting an IP packet having the IP address into the ATM network according to the label converted from the IP address by the converting means; Means for sequentially setting a route to be transferred to the inside.

Here, a feature of the present invention is that the means for sequentially setting the routes includes means for sequentially setting a plurality of routes that do not form a loop for the same IP address.

A means for detecting the presence or absence of congestion in the label switching network shown in FIG. 1 and a place where the congestion occurs is provided. According to the detection result of this detecting means, when there is no congestion, the shortest route among the plurality of routes is selected. And means for selecting a plurality of two or more routes from the plurality of routes when there is congestion. At this time, the two or more selected routes are provided with means for transferring cells in a frame unit for a series of cells constituting one frame. The apparatus further comprises means for identifying the priority of the IP packet. According to the identification result of the means for identifying, the high priority I / O is selected from the two or more routes.
There is provided a means for selecting a shorter route for a P packet than for a low-priority IP packet.

Next, the operation of the embodiment of the present invention will be described. As shown in FIG. 1, a label switch router (LSR) implementing the IP label switching method of the present invention is provided in a label switch network in a central circle.
Around it, an IP subnetwork composed of routers is connected. Each LSR and router deployed throughout this network is
The IP address information of the P host, its connection relation, and link cost information are synchronized as network topology information and held as network topology information. For this reason, regardless of the type of the LSR and the router, each node can independently calculate a transfer route and a transfer cost to the destination by using the network topology information if the IP address to be the destination is determined. .

FIG. 2 shows a protocol stack used in the present invention. The LSR implementing the IP label switching method of the present invention calculates a loop-free multipath that reaches a target IP address from network topology information at the network layer of Layer 3 at the time of route calculation, and determines an adjacent node from the calculation result. When the adjacent node is determined, a path is set by setting a layer 2 ATM address.

As described above, according to the IP label switching method of the present invention, at the time of setting a route, a routing path is set at the end and end of the network by using the network topology information of the layer 3. At the time of IP data transfer, routing is performed by transferring data up to layer 3 hop-by-hop for each router in the IP subnet, but when IP data reaches the label switch network, high-speed labeling is performed at layer 2 using a preset label. It is transferred while being switched.

In the example shown in FIG. 1, a router having an IP address of 129.63.80.1 in the IP subnetwork 1 transfers data to a router having an IP address of 182.66.91.00 in the subnetwork 2. Is shown. In the sub-network 1, the IP packet is terminated hop-by-hop by the router, and is subjected to LSR using the routing information of the layer 3.
H.

In the LSRH, when an IP packet arrives, its destination IP address is checked. In this example, a packet having an IP address of 182.69.11.00.0 has arrived. At this time, as described above, in the label switch network configured by the LSR, the multipath that can reach the target IP address is calculated in advance in the ATM layer, and the label conversion relay forming the multipath is set. The cells decomposed from the IP packet while performing the label conversion are subjected to label switching. In this example, routes 1: H → E → C → A and route 2: H → E → D →
Since C → A exists, a label conversion relay for label switching along these two routes is set.

That is, the IP address 182.69.1 is assigned to the LSRH.
When a 10.0 packet arrives, the LSRH converts the packet to a cell and sets a label 25 in the cell overhead. The cell with the label 25 set as overhead is then transferred to the LSRE. At this time, the LSRE sets the multipath and performs the cell label conversion 25 → 7, 51 at the frame level so that the packet information is not interleaved between the multipaths.
Transfer to SRD. Such operation is similarly performed by LSRD,
The cell transfer is completed by LSRC and LSRA.

However, when a plurality of routes are converged to the same output interface and merged into one label as in the case of LSRC, cells are merged at the frame level so that data interleaving does not occur. When all cells constituting a packet reach LSRA, L
The SRA assembles cells and reproduces IP packets. The reconstructed IP packet is then sent to the IP subnetwork 2 where it is hop-by-hop
Routed to reach routers 182.69 and 110.0. By linking such layer 2 label switching technology and layer 3 IP routing technology,
High-speed and highly reliable multipath data transfer is realized.

Next, a description will be given of a routing algorithm for calculating a multipath in the label switch network. Each LSR provided in the label switch network independently calculates a multipath based on the above-described network topology information including IP addresses of the entire network and transfer cost information between each IP address. At this time, the network topology information held by each LSR is synchronously held as completely the same information among the LSRs of the entire network. Therefore, the multipath transfer route to the same IP address calculated independently by each LSR is within the network. All LS
A perfect match at R is guaranteed.

[0028]

(Equation 1)

The operation of the above algorithm will be described with reference to the example of FIG. FIG. 3 shows an example in which eight LSRs: A, B, C, D, E, F, G, and J are arranged in the label switch network. As an example, consider the calculation of a multipath toward an IP host connected to the LSRJ.
In the algorithm of the present invention, first, the group s and the adjacent vector v of the nearest neighbor node of the destination J are considered. In this case, the adjacent node s = (E, B, C, G). Further, the distance vector Ds is set to the hop cost between (s, J). Thereafter, the operation proceeds to the operation of step 1, and an adjacent node that realizes the minimum hop cost is determined from the distance vector. In this example, among the nodes adjacent to E, B, C, and G, the node E having the hop cost 1 can be reached with the minimum hop cost, so that the node E is determined as P1 as a node on the multipath course.

The determined points are represented as P as a set of points.
To be stored. At this stage, if all nodes in the network have been determined, the operation ends. In this example, since it has not been determined, the operation proceeds to step 2. In step 2, a new adjacent node is searched from the node determined in step 1 and added to the distance vector and vector set for all the adjacent nodes. In this example, an adjacent node B is detected from P1.

However, since the node B has already been added to the adjacent node set by the previous operation, only the distance vector from the node J to the node B is newly calculated, and the distance vector becomes the minimum 3 (route: J ← E ← B, cost: 2
+1, route: J ← B, cost: 4) are set as a distance vector to B. At this time, the distance vector 4 (J ←
B) is deleted from the minimum distance vector and managed as a reachable distance vector. When this operation ends, the process proceeds to a step 1. In step 1, a newest hop node is newly searched, and a node C (route: J ← C, cost: 2) with the next smallest distance vector to J is determined. Then, the process proceeds to step 2 and the node A adjacent to the node C,
F is added to the distance vector and the set of adjacent nodes.

The process further proceeds to step 1 and the node B (the route: J ← E ← B,
Cost: 2 + 1) is determined. When the node is determined, the process proceeds to step 2 to detect the node A as an adjacent node. However, since node A has already been detected as a node adjacent to node C, 4 (J ← E) having the smallest distance vector
← B ← A) is determined as the distance vector. Thereafter, the process proceeds to step 1 and the node A is determined. By repeating such operations, the nodes F, D, and G are determined, all the nodes are determined, and the multipath search ends.

Considering the process of generating a multipath to be searched by this search algorithm, the multipath is realized by a combination of spanning trees starting from a destination. An example is shown in FIG. Since the algorithm of the present invention sets the multipath so that the multipath route always includes the minimum route during the execution of the algorithm, it is guaranteed that the minimum hop route is always included in the multipath. Furthermore, in the calculation process for forming a spanning tree, branches are extended downstream with the determined upstream node as a trunk, so that once determined nodes cannot be used again as a tree trunk. This computation ensures that no loops are formed in the multipath. By employing such a routing algorithm, a loop-free multipath including the minimum hop route to the same IP destination can be set in the label switch network.

Next, a method of setting a multipath calculated using this multipath setting algorithm in an LSR in a label switch network will be described with reference to FIG. FIG. 5 shows the label switch network described above. The multipath search and label setting algorithm of the present invention is classified as a link state routing protocol. Therefore, as described above, all the LSRs in the label switch network synchronously hold the IP addresses in the network and the link costs between the addresses as completely matched information as network topology information.

For example, as shown in FIG. 5, a case is considered where a multipath reaching an IP address 182.69.11.00.0 in a destination subnetwork is set in a label switch network. The LSRJ corresponding to the output unit of the label switch network has its own IP address of 182.6.
9.1 It is determined based on the network topology information described above that it exists in the route reaching 111.0.

Next, in order to reach the IP address, the interface itself determines the interface to be used for the label switch, and selects an unused label in the interface as a set label for the label switch. Next, LSRJ
Determines the multipath that reaches the IP address 182.69.11.00 by using the above-described route search algorithm. When the route is confirmed, the LSR adjacent to itself
Therefore, a label that is vacant on the link between itself and the adjacent router is set as a label for the IP address 182.69.11.0.0.

In the example of FIG. 5, the LSRJ applies the label 19 between the LSRJ and E, the LSRJ, and the label 131 between the B and LSRJ.
Label 251 between J and C, Label 2 between LSRJ and G
52 is set. Once label setting is completed, LSR
J notifies the adjacent node of the label value used between itself and the adjacent node together with the destination IP address. In this case, the adjacent LSREs, B, C, and G receive this notification.

Upon receiving this notification, the adjacent node can know the label value of the destination LSR that can reach the notified destination IP address. Knowing the value of this label, the adjacent node also determines the multipath that can reach the target IP address using the above-described multipath setting algorithm, and determines the LSR adjacent to itself. When the adjacent router is determined, a free label in the link between itself and the adjacent LSR is set as a label for the destination IP address.

After that, the IP address and the determined label information are notified to the adjacent node. For example, in the example of FIG.
E sets the label arriving at label 19 (IP address: 182.69.10.10.0) to 21 and notifies label 21 and the IP address to the LSRB which is an adjacent node. Also LS
The RB sets the label reaching the label 131 to 15 and sets the label 15 and the IP address to the adjacent node LSRA
Notify. Similarly, the LSRC sets the label arriving at the label 251 as 4,210 and sets the adjacent node LSR
A and F are notified of the labels 4, 210 and the IP address.

The label propagation process of the example of FIG. 5 is summarized in the table of FIG. As shown in the table, the LSR in the network does not always perform one label conversion for data destined for the same IP address. This is because a plurality of routing paths are assigned by the above-described algorithm. In such a case, each LSR holds a plurality of label assignment candidates.

In this case, the labels forming the shortest test pass are held in priority order. For example, in the example of FIG.
When a cell reaches the label 17 of the SRA, I
The LSR that reaches the P address 182.69.11.00.0 is the LSR
B and C are held, so that labels corresponding to these two LSRs are held. At this time, the LS forming the shortest test path
A label 15 is set to the LSRB and a label 4 is set to the LSRC, giving priority to the RB. That is, in the LSRA, two label conversions of label conversion 17 → 15 and 17 → 4 can be executed. Which label conversion is selected from a plurality of label conversion candidates is determined by the routing policy to which each cell belongs.

Next, a cell transfer procedure when multipath label switching is executed will be described with reference to FIG.
FIG. 7 shows a case where routes of cells aiming at the same IP destination are separated or combined. Multipath label switching operates when ports on the default show test path are congested and cell transfer quality cannot be met. In this case, if cells are distributed to multipaths without considering IP packets, the order of the cells constituting the same packet may be reversed on the receiving side, and packet assembly may not be performed properly. For this reason, when distributing cells by multipath, the distribution is performed on a frame basis while considering the original IP packet. For example, in the case where a packet is formed into a cell by AAL5, the sorting is performed by recognizing the last cell constituting the packet with reference to the PTI field of the ATM cell. That is, the cluster of cells constituting the same packet is conscious of the cluster of cells constituting the packet based on the value of the PTI field, and the frame is stored by performing label switching on the same routing path for the cluster of cells constituting the same packet.

Even if cells are sorted on a frame basis, the packet order may be reversed at the receiving terminal due to the difference in the packet transfer route, and packets may arrive beyond the TCP window size. In this case, packets arriving beyond the window size cannot be correctly rearranged, so that the receiving terminal cannot correctly receive data within the window size.
In order to prevent the packet order from being reversed due to the difference in the transfer route within the same TCP connection, the packet distribution according to the present invention can be performed on a TCP connection basis.

In this case, when an IP packet arrives at the LSR at the entrance of the label switch network, the source address is also referred to, and when converting to an ATM cell, a VIP or VCI identifier is used for each connection (for each source route). Is assigned. The LSR performing multipath transfer prevents multipath transfer in a connection by transferring cells having the same identifier to the same route.

In the example of FIG. 7, cells having the user identifiers (route identifiers) of the labels 5 and 11 arrive and the route is LSR1 to LSR3 in units of frames in the LSR1, and the route is L
An example is shown in which label switching is performed in frame units on two routes of SR1, LSR2, and LSR3. When multipaths are merged into one route, frame multiplexing techniques are used. By adopting such a technique (corresponding to VC merging), even if multipath label switching is performed, IP packets can be reliably reproduced at the end and end, and the packet order can be prevented from being reversed. .

When performing such multi-path label switching, priority and non-priority labels are further given to connections, so that cells of the priority class preferentially perform label switching using the shortest path route and cells of the non-priority class. The cell can transfer the cell under a multipath environment when congestion occurs, thereby satisfying the cell transfer quality of the show test path of the priority class.

As shown in FIG. 8, by controlling the switching route for each priority class in the label switching network, it is possible to satisfy the cell transfer quality for each class.

[0048]

As described above, according to the present invention,
High-speed and high-quality label switching of IP packets can be performed on an ATM network. In particular, when congestion occurs, multipath label switching can be performed frame by frame while adaptively bypassing the congestion point according to the QoS class. By using the routing algorithm of the present invention, high-throughput and highly reliable packet transfer can be realized in a large-scale and complicated IP network.

[Brief description of the drawings]

FIG. 1 is a diagram showing a network configuration assumed in an embodiment of the present invention.

FIG. 2 is a diagram showing a protocol stack used in the embodiment of the present invention.

FIG. 3 is a diagram for explaining an algorithm operation according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a multipath realized by a combination of spanning trees starting from a destination.

FIG. 5 is a diagram showing a label switch network according to the embodiment of the present invention.

FIG. 6 is a diagram showing a label setting correspondence table according to the embodiment of the present invention.

FIG. 7 is a diagram for explaining a cell switching procedure associated with separation or connection of a label switching path according to the embodiment of the present invention.

FIG. 8 is a diagram showing a multi-QoS control method according to an embodiment of the present invention.

[Explanation of symbols]

 A ~ J LSR

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masayoshi Nabeshima 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 5K030 GA03 GA11 HA10 HB00 HB08 HB14 HB17 HC01 LB08 LC11 LE05 MB02

Claims (5)

[Claims] 1. Means for holding network topology information composed of label information including VPI and VCI predetermined in correspondence with an IP address and link cost information, and a network topology held by the holding means Means for performing conversion between an IP address and a label in accordance with the information;
Means for sequentially setting a route for transferring an IP packet having a P address into an ATM network.
In the label switching communication system, the means for sequentially setting includes means for sequentially setting a plurality of routes that do not form a loop for the same IP address. 2. Means for detecting the presence or absence of congestion in the ATM network and the place where the congestion has occurred are provided, and means for selecting the shortest route among the plurality of routes according to the detection result of the detecting means when there is no congestion. The IP label switching communication system according to claim 1, further comprising: 3. The IP according to claim 2, further comprising: means for selecting a plurality of two or more of the plurality of routes when there is congestion in accordance with a detection result of the detecting means.
Label switching communication method. 4. The IP label according to claim 3, wherein said two or more routes selected by said plurality of selecting means include means for transferring cells in a frame unit for a series of cells constituting one frame. Switching communication method. 5. A means for identifying a priority of an IP packet is provided. According to an identification result of the identifying means, the means for selecting a plurality of IP packets includes a high priority I / O from the two or more routes.
4. The IP label switching communication system according to claim 3, further comprising means for selecting a shorter route for the P packet than for a low priority IP packet.