A METHOD AND SYSTEM FOR ENCAPSULATING MULTICAST PACKETS INTO
UNICAST PACKETS
FIELD OF INVENTION
The present invention relates to a method and system for encapsulating multicast packets into unicast packets.
BACKGROUND ART
In general, multicast addressing is designed to enable the delivery of datagrams to a set of hosts that have been configured as members of a multicast group in various scattered subnetworks. As defined in the IEEE standards, multicast traffic is treated similar to broadcast traffic whereby any multicast traffic which passes through a wireless communication system would be transmitted at a basic data rate as it would be broadcasted on the Media Access Control (MAC) layer of the Data Link layer (Layer 2) of the Open System Interconnection (OSI) model. Thus, data quality and integrity may most likely be affected.
Typically, conversion of multicast traffic to unicast traffic to the user is perform in several method which includes the use of access point in a communication network to receive a multicast or broadcast packet from a source. The use of access points converts the multicast or broadcast packet into a unicast packet and further transmits the unicast packet over the communications network from the access point. The conversion of multicast to unicast traffic does not consume or preserve bandwidth.
Alternatively, Internet Protocol (IP) address lookup method and hardware architecture, which utilizes the hashing process, reduces searching time. Searching time refers to time for searching entries of the sub-table having the prefix matched with the prefix of the IP address starting from a location in the sub-table pointed by a pointer of the main table. IP address lookup process is perform on all the prefixes by classifying prefixes based on the prefix lengths and constructing separate tables corresponding to the classified prefix lengths of the IP address. The problem, which arises, is such that the
binary searching combined hashing scheme is not practical as the calculation involves large numbers and consumes processing time.
With further enhancement, conversion of multicast traffic to unicast traffic, which involves the MAC addresses, is employed. By including the MAC address to which the multicast packet stream is to be transmitted, the multicast packet stream is effectively converted to unicast traffic stream. The traffic conversion techniques discards non-participating subscriber, thus avoid from overburdening traffic. The above mentioned mechanism affects the quality and integrity of data as does not have the effect of end-to-end multicast operation.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.
SUMMARY OF INVENTION
In one embodiment of the present invention is a method for encapsulating multicast packets into unicast packets for an end-to-end multicast operation. The method comprises receiving a plurality of incoming multicast packets from an incoming wireless module, translating the plurality of incoming multicast packets to a recognizable format for mapping, mapping the plurality of incoming multicast packets to generate a plurality of unicast packets, translating the unicast packets to a recognizable format for transmission and transmitting the unicast packets into an outgoing wireless module. The step of mapping the plurality of incoming multicast packets to generate a plurality of unicast packets further comprises extracting a subscriber IP address, a subscriber MAC address and a TTL period from the plurality of incoming multicast packets, storing the subscriber IP address, the subscriber MAC address and the TTL period in an intelligent hashing table, encapsulating the plurality of incoming multicast packets into a plurality of unicast packets, forwarding the unicast packets for mapping and multiplying the unicast packets in the presence of multiple subscribers.
In another embodiment of the present invention is a system for encapsulating multicast packets into unicast packets for an end-to-end multicast operation. The system comprises a TCP/IP communication stack, a first translation module, a first mapping module, an intelligent hashing table, a second mapping module and a second translation module. The TCP/IP communication stack comprises means for receiving a plurality of incoming multicast packets from an incoming wireless module. The first translation module comprises means for translating the plurality of incoming multicast packets to a recognizable format for mapping. The first mapping module comprises means for extracting a subscriber IP address, a subscriber MAC address and a TTL period from the plurality of incoming multicast packets, means for storing the subscriber IP address, the subscriber MAC address and the TTL period in the intelligent hashing table, means for encapsulating the plurality of incoming multicast packets into a plurality of unicast packets and means for forwarding the unicast packets for mapping. The intelligent hashing table comprises means for storing the extracted subscriber IP address, the subscriber MAC address and the TTL period. The second mapping module comprises means for forwarding the unicast packets for mapping and means for multiplying the unicast packets for mapping in the presence of multiple subscribers. The second
translation module comprises means for translating the unicast packets to a format recognizable for transmission and means for transmitting the unicast packets into an outgoing wireless module.
The present invention consists of several novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings, it being understood that various changes in the details may be made without departing from the scope of invention or sacrificing any of the advantages of the present invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
To further clarify various aspects of some embodiments of the present invention, a more particular description of the invention will be rendered by references to specific embodiments thereof, which are illustrated, in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the accompanying drawings in which:
FIG. 1 illustrates a system arrangement for encapsulation of multicast packets into unicast packets for an end-to-end multicast operation.
FIG. 2 is a flowchart illustrating a method for encapsulating multicast packets into unicast packets for an end-to-end multicast operation.
FIG. 3 is a flowchart illustrating a method for mapping a plurality of incoming multicast packets to generate a plurality of unicast packets.
FIG. 4 is a flowchart illustrating a method for encapsulating a plurality of incoming multicast packets into a plurality of unicast packets.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention relates to a method and system for encapsulating multicast packets into unicast packets for an end-to-end multicast operation. Hereinafter, this specification will describe the present invention according to the preferred embodiments of the present invention. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the scope of the appended claims.
The method and system for encapsulating multicast packets into unicast packets for an end-to-end multicast operation according to the embodiments of the present invention describes a method and a system that streams multicast traffic on a wireless communication network by encapsulating the multicast packets of the Network Layer (Layer 3) of the Open Systems Interconnection (OSI) model into unicast packets in Media Access Control (MAC) Layer which is a sub layer of the Data Link Layer (Layer 2) specified in the OSI model. The Network Layer is also known as the Internet Layer or Internet Protocol Layer as the best-known example of a Layer 3 protocol is the Internet Protocol (IP).
The mechanism of encapsulating multicast packets into unicast packets ensures that the data quality is rendered to be substantially comparable to the data quality of unicast packets due to the fact that transmission reliability is ensured on the MAC layer. The embodiments of the present invention are intended to substantially resolve the issue of poor transmission whilst maintaining data quality and integrity of multicast packets across the wireless communication network. This is achieved by encapsulating multicast packets transmitted on the IP layer is into unicast packets on the MAC layer.
The method and system according to the embodiments of the present invention may be described as a dynamically loadable module that is plugged into a kernel to provide end- to-end multicast support over the wireless communication network, wherein a single multicast stream on the IP layer is converted into a unicast stream on MAC layer. A subscriber that subscribes to the multicast stream is substantially unaware of the fact that the multicast packets on the IP layer have been converted to unicast packets on the
MAC layer. This feature facilitates an end-to-end multicast operation over the wireless communication network.
Reference is first being made to FIG 1. FIG 1 illustrates a system arrangement for encapsulation of multicast packets into unicast packets for an end-to-end multicast operation. The system according to the embodiments of the present invention comprises an incoming wireless module (102), a Transmission Control Protocol/Internet Protocol (TCP/IP) communication stack (104), a multicast enhancement module, and an outgoing wireless module (116). The multicast enhancement module further comprises translation modules (106, 114), mapping modules (108, 112) and an intelligent hashing table (110). The translation modules (106, 114) essentially comprise a first translation module (106) and a second translation module (114). Likewise, the mapping modules (108, 112) essentially comprise a first mapping module (108) and a second mapping module (112).
The system according to the embodiments of the present invention may be best utilized in a wireless communication network, wherein the incoming wireless module (102) is of similar or different wireless technology than that of the outgoing wireless module (116). The incoming wireless module (102) may comprise a radio frequency module, an infrared light module or a wireless module of the like. Similarly, the outgoing wireless module (116) may comprise a radio frequency module, an infrared light module or a wireless module of the like. Where the system according to the embodiments of the present invention is implemented on a wireless communication system, substantial efficiency of the same is observed, as there is an absence of repeated traffic on the end- to-end multicast operation.
Encapsulation of the multicast packets into unicast packets for the end-to-end operation begins with the TCP/IP communication stack (104) receiving a plurality of incoming multicast packets originating from the incoming wireless module (102). The TCP/IP communication stack provides an end-to-end connectivity by forwarding the plurality of incoming multicast packets to the multicast enhancement module, which comprises the first translation module, the second translation module (114), the first mapping module (108), the second mapping module (112) and the intelligent hashing table (110). Upon receiving the plurality of incoming multicast packets from the incoming wireless module
(102), the first translation module (106), translates the plurality of incoming multicast packets to a recognizable format for the purpose of mapping the multicast packets in the first mapping module (108) and the second mapping module (112).
The first mapping module (108) and the second mapping module (112) progressively build the intelligent hashing table (110) by dynamically storing a subscriber IP address, a subscriber MAC address and a Time To Live (TTL) period. Using these stored parameters, the intelligent hashing table performs smart mapping based on the multicast streams available in the wireless communication network.
The first mapping module (108) and the second mapping module (112) utilize Multicast Listener Discovery (MLD) Protocol to map the plurality of incoming multicast packets to generate a plurality of unicast packets. Multicast Listener Discovery Protocol version 2 (MLDv2) is a protocol fundamentally applied in IPv6 routers to discover multicast listeners on a directly attached link wherein the multicast protocol, address lengths and address scopes are significantly varied. In one embodiment of the present invention, the method and system for encapsulating multicast packets into unicast packets for an end- to-end multicast operation is proposed for the implementation with IPv6, which is characterized with a variation of address lengths and protocol operations.
The first mapping module (108) communicates with the second mapping module (112) to encapsulate the plurality of incoming multicast packets into a plurality of unicast packets. The second mapping module (112) forwards the encapsulated multicast packets in the form of unicast packets to the second translation module (114). The second translation module (114) translates the unicast packets to a format recognizable for transmission. These unicast packets are then transmitted to the outgoing wireless module (116).
Reference is now being made to FIG 2. FIG 2 is a flowchart illustrating the method for encapsulating multicast packets into unicast packets for an end-to-end multicast operation. The method for encapsulating multicast packets into unicast packets for the end-to-end multicast operation comprises receiving the plurality of incoming multicast packets from the incoming wireless module (202), translating the plurality of incoming multicast packets to a recognizable format for mapping (204), mapping the plurality of incoming multicast packets to generate a plurality of unicast packets (206), translating
the unicast packets to a recognizable format for transmission (208) and finally transmitting the unicast packets into the outgoing wireless module (210).
In the method according to the embodiments of the present invention, the step of mapping the plurality of incoming multicast packets to generate a plurality of unicast packets comprises steps as referred to FIG 3. FIG 3 is a flowchart illustrating the steps during mapping for the end-to-end multicast operation. In mapping the plurality of incoming multicast packets to generate a plurality of unicast packets, the subscriber IP address, the subscriber MAC address and the TTL period of each packet from the plurality of incoming multicast packets is extracted by the first mapping module (302).
The extracted addresses and TTL period is then stored in the intelligent hashing table (304). Thereafter, the plurality of incoming multicast packets is encapsulated into unicast packets (306) whereby the plurality of incoming multicast packets of the IP layer are encapsulated into unicast packets in the MAC Layer. Data transmission reliability is ensured on the MAC layer, wherein packets are transmitted in multicast streams to conserve bandwidth on the backbone of the network. Multicast to unicast conversion is not employed at the IP Layer; it is only employed at the MAC layer and appears to the subscriber as multicast packets. The embodiment according to the present invention allows for various types of subscribers that subscribed to a multicast stream.
The encapsulated unicast packets are then forwarded to the second mapping module (112) for further mapping (308). In addition, the encapsulated unicast packets are multiplied in the presence of multiple subscribers (310).
Reference is now being made to FIG 4. FIG 4 is a flowchart illustrating the steps of encapsulating the plurality of incoming multicast packets into a plurality of unicast packets. In encapsulating the plurality of incoming multicast packets into a plurality of unicast packets, the subscriber IP address, the subscriber MAC address and the TTL period of the plurality of incoming multicast packets from the first mapping module is compared (402) to the subscriber IP address, the subscriber MAC address and the TTL period stored in the intelligent hashing table to identify a match using the implementation of smart mapping (404).
Smart mapping is performed based on the available information to determine if a match is identified and if the TTL period is larger than a specified range whereby the description herein will refer to the specified range as zero. The present invention implements the TTL period evaluation method for disconnecting non existent subscribers whereby the network elements in the wireless communication network will be informed if a particular packet has been in the network for a substantially long duration and if the same is to be discarded. This is to prevent the packet from looping infinitely due to the absence of addressing information in the intelligent hashing table.
When a match is identified using the addressing information on the intelligent hashing table and the plurality of incoming multicast packets in the first mapping module within the specified TTL period, the subscriber MAC address stored in the intelligent hashing table is appended to the plurality of incoming multicast packets (406). However, when a match is not identified using the addressing information on the intelligent hashing table and the plurality of incoming multicast packets in the first mapping module within the specified TTL period, the plurality of incoming multicast packets are discarded from the mapping module (408).
The method and system according to the embodiments of the present invention may be described as a scenario where multiple subscribers are accessing different multicast streams for a wireless communication network. For example, in the presence of three subscribers A, B and C, subscriber A first subscribes to a multicast stream and is assigned to an IP multicast stream FF3E::1. The intelligent hashing table is dynamically updated based on the subscriber MAC address and the TTL period as shown in Table 1.0.
Table 1.0: Subscriber A subscribes to multicast stream (FF3E::1)
Subscriber B then accesses the network and subscribes to a multicast stream on the same IP multicast stream with a particular TTL period. The intelligent hashing table is dynamically updated as shown in Table 2.0.
Table 2.0: Subscriber B subscribes to multicast stream (FF3E::1)
Subscriber C then accesses the network and subscribes to a new IP multicast stream, FF3E::2 a different multicast address. This information is conveyed to the intelligent hashing table to enable the implementation of smart mapping as shown in Table 3.0.
Table 3.0: Subscriber C subscribes to multicast stream FF3E::2
When a multicast packet arrives at the first mapping module (108), the first mapping module (108) determines if the incoming packets are from multicast subscribers by using the MLDv2. Upon confirmation that the plurality of incoming packets subscribes to a multicast stream, smart mapping takes place. The first mapping module (108) compares with the updated intelligent hashing table (110) and appends the destination MAC address into the plurality of incoming packets. The unicast packets will then be forwarded to the second mapping module (112).
The second mapping module (112) thus forward and multiply the packets on unicast MAC address according to the number of subscribers available to the second translation module (114) which then translates the packets to a recognizable format for transmission into the corresponding outgoing wireless module (116). In a situation where the addressing information on the intelligent hashing table (110) shows that there are no subscriptions to a multicast stream, the first mapping module (108) silently drops the packets thus conserving valuable bandwidth of the entire end-to-end multicast operation.
The present invention may be embodiment in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All
changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.