Patent Application
20070263571
1. Field of the Invention
The invention is used in communications networks to ensure that a service provider can set up services to customers or mobile users in a special selected geographical area.
2. Description of the Related Art
In the near future service providers will offer customers the possibility to set up services in a special selectable geographical area or to send information to it. By this way, mobile (wireless) users can be maintained with useful services and information which is related to their current position, e.g. special offers can be advertised to users who are located in the area of a shop.
One of the required basic functionalities to realize such services is a method to send data from the service provider to a chosen geographic area, i.e. to the access routers which cover these areas with their wireless access technology. This can be achieved by inserting the geographical destination coordinates in each message. It is assumed that every access router knows the coordinates of its coverage area and all relevant intermediate network systems know the coverage areas of the other systems which are connected to them. In this case each router performs a test if the geographical area which is covered by its connected access routers or the coverage areas of other routers which are connected to it comply with the target address and forward it to the appropriate system. The described mechanism is called GeoCast (see, T. Imielinski, J. Navas, “GeoCast-Geographic Addressing and Routing”, Proceedings of the Third ACM/IEEE International Conference on Mobile Computing and Networking (MobiCom'97), Budapest, Hungary, September 1997).
The drawback of the described mechanism is the delay which is caused by the expensive intersection checks in the intermediate systems before a message can be forwarded towards its destination. Additionally, the intermediate systems may become a performance bottleneck resulting in congestion if the number of messages to be routed exceeds a certain rate.
A need therefore exists for a technique that can reduce the delay caused by intermediate systems performing intersection checks in order to deliver a message towards its destination in a geographical area, and reducing the bottlenecks that systems may cause which in turn cause performance to degrade.
With the present invention, the abovementioned issues are resolved in an efficient and simple manner. The proposed technique allows for the delivery of a message to a destination within a geographical area.
The method for delivering messages in a communications network includes
Any further messages destined for the geographical area arriving after the establishment of a multicast group are delivered via the established multicast group. After a predefined time period has elapsed within which no further messages destined for the geographical area arrive, the multicast group is removed. Each message destined for the geographical area is defined by a geographical destination address; when the geographical destination address of the messages are identical or similar, monitoring the rate of arrival of messages is performed using a soft state message counter; whereby fast internet protocol forwarding is used to forward the messages in the multicast group.
These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the detailed description given herein below, taken in conjunction with the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
We assume that an architecture as shown in
In the geographic territory an area has been defined. When a message is send to this area, it is routed through the distribution network to the access routers which are connected to those antennas which supply the area, i.e. which coverage area corresponds to it.
The gateway performs an intersection check and forwards the message to two intermediate routers, which have to perform the check again and so on until the message reaches the access routers. The access routers then emit the message in the geographical area.
In the simple example shown in
Simulation results for a prototypical GeoCast routing system show that the forwarding decision in an intermediate system will take up to 4,426 times more that that of an IP router (in fact that a IP router uses firmware has to be considered but the result nevertheless roughly shows the scale of the performance difference). These results show that the packet delay resulting from the duration of the forwarding decision would increase heavily and that a congestion of an intermediate router might result if it has to route too many packets.
Our invention deals with several aims:
Up to now, there is no solution which explicitly addresses the dynamic adaptive configuration of distribution networks for routing to geographical addresses. A mechanism which utilizes dynamic multicast groups to circumvent intersection checks does not exist.
Several efforts have been made to develop mechanisms which are able to forward messages to geographic areas.
GeoCast:
The GeoCast mechanism which has been introduced at the beginning of this document relies on the intersection checks of the geographical target address of a message with the coverage area of each intermediate system. As already stated, the checks require a non-negligible amount of computing power and time. Additionally, an expensive parsing of the address is required depending on its presentation in the message. The intersection check has to be performed for each single message. At least, GeoCast uses cache entries to speed up forwarding decisions. Messages are identified via an ID or by other values which are part of the message header e.g. the source and destination address. After the first packet has been received the resulting forwarding decision is stored in the cache. Following messages with the same ID can skip the intersection check but nevertheless the message must be processed by the geographic routing module to determine the ID and the corresponding cache entry in each router. Further disadvantages are that the messages are sent via unicast and so there is no mechanism in place to reduce the overall amount of messages to be transmitted in the network (e.g. no multicast routing). No mechanism for dynamic optimization of message routing is provided.
Deployment of Static Multicast Groups:
Another mechanism, which relies on IP multicast is called GPS-Multicast Routing Scheme which is described in T. Imielinski, J. Navas, “GPS-Based Addressing and Routing” IETF Request for Comments 2009, rfc2009.txt, November 1996. To speed up the forwarding decision static multicast groups are established in the distribution network. Routers are combined to Atoms and a multicast address is assigned to them. Several atoms are combined to a partition with an own address again and partitions can be combined to larger partitions. A geographical target address polygon in a message is then approximated with the smallest partition which contains it and sent to the corresponding IP multicast address. This requires a mapping from the geographical destination address to the multicast group. One disadvantage of this approach is the fact that the multicast groups will only rarely match the exact target areas. This means that several systems in the network will erroneously receive the packets, perform an intersection check and discard it. The main drawback of this approach is that before the static multicast mechanism can be utilized in the network, a division of the coverage areas into atoms and partitions is necessary. This leads to a difficult network planning problem requiring expensive considerations or estimations of the (at this time still unknown) traffic patterns and a lot of administrative interaction for the pre-configuration of the network and during its operation. Another problem with this approach is that it has to be decided a priori how to partition the geographic topology and which multicast groups to create, which is very likely to lead to many only rarely or not at all used multicast groups for which (rare) multicast addresses have to be assigned and signalling traffic has to be exchanged and processed.
Deployment of Dynamic Multicast Groups on the Last Hop:
For the distribution of the message between the access router and the mobile clients in its coverage area the GPS-Multicast Routing Scheme deploys multicast groups for the “last Mile” routing. An access router assigns a group to all mobile clients in a specific area. This happens also dynamically and is based e.g. on the specific geographical polygon. All mobile clients in it can join the group because of knowing their geographical address derived from their assumed GPS module. In contrast to the invention described in this invention report, the multicast groups are not deployed in the distribution network to reduce the packet delay and speed up the forwarding decisions in the intermediate systems, but the groups are only valid between access routers and mobile clients and have the purpose to reduce the amount of unnecessary messages mobile clients will receive and to save rare resources of the air interface. Another disadvantage of this mechanism is that for each specific individual geographic address one multicast group is assigned and maintained.
In order to reduce the forwarding delay and amount of required intersection checks and messages, the invention described in this invention report provides a mechanism to establish multicast groups in the network which are dynamically adapted, depending on the occurring data traffic. If a certain amount of messages arrives in a short period of time with the same or a similar geographical target address, an IP multicast group will be established by the network which contains all the access routers being responsible for the message forwarding, i.e. all those access routers which would usually forward the message when they received it after an intersection check requiring forwarding procedure through the distribution network. The advantage of the described mechanism is based on the fact that an IP multicast forwarding decision in an intermediate system is multiple times faster that a GeoCast one.
In detail, a upper level router in the distribution network, e.g. the gateway, monitors if it receives several messages with the same or very similar destination addresses in a short period of time (e.g. in case service providers want to address users in an area with a special event). The period or arrival rate is chosen in a way that the router can estimate that multiple messages with the same address will follow. This can, for example, be realized with a soft state message counter. By monitoring the traffic load of geographic areas, the geocast router is able to compute optimal geographic areas for multicast distribution of geographic messages, optimizing between various tradeoffs/number of multicast groups, number of unnecessarily distributed messages, signalling load for multicast group maintenance, etc.).
Afterwards the access routers which are responsible for the message delivery to parts of the addressed geographical area are requested to join a dynamically created multicast group. The request is send from the upper level router via a standard geographical addressed message to the access routers and intercepted by them. After the respective access routers processed the request and joined the multicast group and confirmed it, messages for the area are directly send to the IP multicast group. All intermediate systems utilize fast standard IP forwarding for the messages making the expensive intersection checks in the intermediate systems unnecessary and enable the network to duplicate the messages as close to the target systems as possible. The access routers remove the multicast IP information form the messages and forward them according to their geographical target addresses. A multicast group is removed if no messages with the respective target addresses arrive any more for a certain period of time.
The proposed mechanism is suited for the next generation of services, which are related to specific areas (so called Area Based Services). It is a basic technology deployable in the network infrastructure to speed up the forwarding decisions in intermediate systems. With faster decisions the delay for message delivery is also shortened.
The following section presents a more detailed explanation of the invention.
The following important properties have been achieved:
In the distribution network, multicast groups are dynamically established to reduce forwarding delay and to reduce the amount of duplicated messages.
What is claimed is that novel methods have been developed:
Summarizing, our invention represents an important step towards realizing a self-configuring efficient distribution network for routing messages to geographic addresses.
The following shows an illustrative example of the invention. It is related to the architecture of a sample access network, with a distribution network of a certain carrier. The network is connected via a gateway to the internet which is in this case simultaneously the upper level router. Let us assume that a certain public event (e.g. soccer game) takes place in the coverage area (e.g.) of the access routers connected to the network.
Now a certain company wants to advertise its products in this area during the event. It determines the geographical coordinates of the area and inserts them in an advertisement message. The message is then send to the gateway of the distribution network (usually, this step requires the interaction of a service broker but this is out of interest for the invention).
The advertisement message is now send via GeoCast through the distribution network and emitted by the products at once but sends messages to the same area in short time intervals.
After some messages the gateway notices that this geographical address is used very often. It composes a Request to Join temporary group message and inserts an allocated temporary multicast address. This message is encapsulated in a special GeoCast message which has the same geographical coordinates as the other messages. Afterwards it is send out to the distribution network.
The access routers receive the messages and decapsulate them. Instead of delivering them to the area, they start with the Request to Join message processing by joining to the multicast group with the predetermined multicast address.
Afterwards, the Join temporary group message is send back to the gateway. When the intermediate systems and the gateway receives all Request to Join messages (which means that all affected access routers received the message from the gateway), the gateway adds the appropriate multicast state to its own routing entries.
If a GeoCast message with the matching destination address arrives at the upper level router it is encapsulated in an IP multicast packet and directly send to the access routers. The forwarding in the distribution network is done via fast IP routing decisions.
The access routers decapsulate the messages and distribute them in the area via their antennas.
Another company also wants to send advertisements to the area of the public event. It determines the geographical coordinates, which differ only marginal from those which are used by the first company. The company sends messages with the coordinates (i.e. the similar geographical address) to the gateway, too. The gateway notices the similarity and sends the messages to the same already established multicast group address. The rest of the message processing is the same as described above.
When the event ended, neither the first nor the second company sends messages to the area any more. After some time the temporary multicast address is removed in the distribution network, for example via timeouts or explicit pruning messages.
Although the invention has been described in terms of preferred embodiments described herein, those skilled in the art will appreciate other embodiments and modifications which can be made without departing from the scope of the teachings of the invention. All such modifications are intended to be included within the scope of the claims appended hereto.
The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).
This application is based on and hereby claims priority to U.S. Provisional Application No. 60/576,843 filed on Jun. 4, 2004, the contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/52396 | 5/25/2005 | WO | 1/31/2006 |
| Number | Date | Country | |
|---|---|---|---|
| 60576843 | Jun 2004 | US |
