Patent Application
20110090851
A method and system for the transmission of fragmented packets on a packet-based communication network.
IP-based mobile system includes at least one mobile node on a wireless communication system. The term “mobile node” includes a mobile communication unit, and, in addition to the mobile node, the communication system has a home network and a foreign network. The mobile node may change its point of attachment to these networks, but the mobile node will always be associated with a single home network for IP addressing purposes. The home network has a home agent and the foreign network has a foreign agent—both of which control the routing of information packets into and out of their network.
The mobile node, home network, and foreign network may be called other names depending on the nomenclature used on any particular network configuration or communication system. For instance, a “mobile node” is sometimes referred to as user equipment, mobile unit, mobile terminal, mobile device, or similar names depending on the nomenclature adopted by particular system providers.
A “mobile node” encompasses PC's having cabled (e.g., telephone line (“twisted pair”), Ethernet cable, optical cable, and so on) connectivity to the wireless network, as well as wireless connectivity directly to the cellular network, as can be experienced by various makes and models of mobile terminals (“cell phones”) having various features and functionality, such as Internet access, e-mail, messaging services, and the like. The term “mobile node” also includes a mobile communication unit (e.g., mobile terminal, “smart phones,” nomadic devices such as laptop PCs with wireless connectivity).
A home agent may be referred to as a Home Agent, Home Mobility Manager, Home Location Register, Local Mobility Agent, or Packet Data Network. And, a foreign agent may be referred to as a Mobility Agent Gateway, Serving Gateway, Serving Mobility Manager, Visited Location Register, and Visiting Serving Entity. Foreign networks can also be called serving networks. The terms Mobile Node, Home Agent and Foreign Agent are not meant to be restrictively defined, but could include other mobile communication units or supervisory routing devices located on the home or foreign networks.
The mobile node will always be associated with its home network and sub-network for IP addressing purposes and will have information routed to it by routers located on the home and foreign network. If the mobile node is located on its home network, information packets will be routed to the mobile node according to the standard addressing and routing scheme.
If the mobile node is visiting a foreign network, however, the mobile node obtains appropriate information from an agent advertisement, and transmits a registration request message (sometimes called a binding update request) to its home agent through the foreign agent. The registration request message will include a care-of address for the mobile node. A registration reply message (also called a binding update acknowledge message) may be sent to the mobile node by the home agent to confirm that the registration process has been successfully completed.
As part of the registration process, the mobile node maintains connectivity with the home agent or local mobility anchor through the use of a “care-of address.” This care-of address is registered with the home agent or local mobility anchor in a table, sometimes called a Binding Cache Entry Table. The registered care-of address identifies the foreign network where the mobile node is located, and the home agent or local mobility anchor uses this registered care-of address to forward information packets to the foreign network for subsequent transfer onto the mobile node.
The mobile node may change its point of attachment to the Internet through these networks, but the mobile node will always be associated with a single home network for IP addressing purposes. The home network includes a home agent and the foreign network includes a foreign agent—both of which control the routing of information packets into and out of their network. A mobile node may transition and move from one foreign network to another foreign network. Each foreign network is identified by a different care-of address, so the transition of the mobile node from one foreign network to a new foreign network requires a modification of the care-of addresses registered for the mobile node at the home agent or local mobility anchor.
If the home agent or local mobility anchor receives an information packet addressed to the mobile node while the mobile node is located on a foreign network, the home agent or local mobility anchor will transmit the information packet to the mobile node's current location on the foreign network using the applicable care-of address. This is accomplished by forwarding the information packet to the care-of address where the foreign network will receive the information packet, and forward the information packet to the mobile node on the foreign network. During these communications, the transmission of communication packets between the foreign network and the home agent or local mobility anchor will be performed using a tunneling communication protocol.
The registered care-of address identifies the foreign network where the mobile node is located, and the home agent or local mobility anchor also uses this registered care-of address to forward information packets received from the mobile node located on the foreign network. In this situation, the mobile node may transmit information and communication packets back through the foreign agent to the home agent or local mobility anchor for further processing and transmission to other nodes on the system, such as the correspondence node. The source of the information packets will be identified on the mobile node's packets as the mobile node's care-of address.
The home agent or local mobility anchor will confirm that the mobile node's communications are being transmitted from a valid care-of address for the mobile node before routing, processing, and further transferring the packets received from the mobile node. If the home agent receives an information packet that does not have a valid care-of address as its source, the packets will not be processed further. If the care-of address is valid, the information packet will then be forwarded and routed to the destination by the home agent or local mobility anchor. These communications are sometimes referred to a “tunneled” communication between the foreign network and the home network.
Tunneling is the basic methodology in IP communication by which a data packet is routed to the appropriate internet node through an intermediate internet address. Typically, a data packet with network routing is “encapsulated” by IP address information. Encapsulation involves adding an outer IP header to the original IP header fields. In this manner, a “tunnel” can be constructed. The outer IP header contains a source and destination IP address—the “endpoints” of the tunnel. The inner IP header source and destination addresses identify the original sender and destination addresses.
The original sender and recipient addresses remain unchanged, while the new “tunnel” endpoint addresses are grafted upon the original data packet. This alters the original IP routing by delivering the data packet to an intermediate destination node (in this case the Foreign Agent), where it is “decapsulated” or “de-tunneled” yielding the original data packet and routing. The packet is then delivered according to the destination found in the original IP address.
The important concept to keep in mind is that the “tunnel” is established by encapsulating a data packet containing the original IP address of the Mobile Node and an IP source address with the intermediate routing IP address (i.e. care-of address) of the foreign network. After the Foreign Agent decapsulates the data packet, the Foreign Agent in turn routes the data packet using the assigned Home Address of the Mobile Node found in the original data packet.
During the transmission of encapsulated transmission packets in the tunneling communication, the encapsulated transmission packets are transmitted through the home network, foreign network and intermediate routers and networks until it reaches the mobile node. Each of these steps in the transmission path can be considered a separate node in the transmission path. There may be limitations on the size of packeted transmissions that can be transmitted to or from the home network, foreign network or intermediate routers and networks. Because the size of the encapsulated transmission packets is not fixed, the size may exceed these packet size limitations.
In order to comply with these maximum size requirements, the various nodes on the transmission path may “fragment” the encapsulated transmission packets into separate smaller sized packets that can be transmitted between nodes on the transmission path in compliance with the maximum packet size limitations. Fragmentation performed by nodes in the transmission path often requires that further encapsulation headers be added to the fragmented packets, which introduces additional overhead and consumes additional system resources to assemble and transport such fragmented packet transmissions.
Fragmentation performed by the internal nodes in the transmission path can significantly increase the overhead and use of system resources, which can be avoided if the initial fragmentation performed at the home network fragments the packet size at or below a lowest maximum transmission unit (MTU) size for the nodes on the transmission path. It is a primary objective of the present invention to reduce the overhead and system resource usage by discovering the lowest maximum transmission unit (MTU) size for tunneled communications to and from a mobile node for all or some of the transmission path to the mobile node.
The present invention provides a method and system for the identification and discovery of the lowest maximum transmission unit (MTU) size for transmission packets on some or all of the transmission path nodes. Different methods and protocols are described in the present patent application to support the identification and discovery of the lowest maximum transmission unit (MTU) size for fragmented transmission packets.
The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements and in which:
In
The transceiver station (Xan) 110 is coupled to a basestation location (eNB) 120 by connection 115, and the basestation location (eNB) 120 is coupled to IP Network1125 by connection 122. The IP Network1125 is coupled to the foreign agent MAG/SGW 130 on the foreign network by connection 127, and the foreign network MAG/SGW 130 is coupled to the IP Network2135 by connection 132.
The IP Network2135 is coupled to an intermediate router RTR 140 by connection 137. The intermediate router RTR 140 is coupled to the IPNetwork3 by connection 142, and the IPNetwork3 is connected to the home agent LMA/PDN 150 on the home network by connection 142. The present invention is described with respect to the downlink transmissions from the home agent LMA/PDN 150 to the mobile node 101, but the present invention could be applied equally to uplink transmissions from the mobile node 101 to home agent LMA/PDN 150.
In the present invention, the home agent LMA/PDN 150 encapsulates a transmission packet 201 shown in
In the present invention, if internal fragmentation is conducted by the home agent LMA/PDN 150 (or the other nodes on the network), the fragmentation occurs prior to encapsulation. The transmission packet 301 shown in
The second fragmented transmission packet 320 has a second portion of the data payload 302 designated as data payload 322. After fragmentation, the fragmented transmission packets 310 and 322 are encapsulated and shown as encapsulated transmission packets 330 and 340. The encapsulated transmission packet 330 has an encapsulation IP header 335, UDP designation 336, GTP designation 337, IP header 303 and data payload 312. The encapsulated transmission packet 340 has an encapsulation IP header 341, UDP designation 342, GTP designation 343, and data payload 322.
The methods of internal and external fragmentation each have various advantages and disadvantages. Both fragmentation methods are shown to increase the overhead for each transmission packet by increasing the header information that will need to be processed. Further, external fragmentation has overhead added to each fragmented transmission packet 230 and 220, but transmission packet 220 does not possess sufficient header information to determine how the transmission packet 220 should be handled (QoS) and prioritized. (e.g. latency, bandwidth, priority)
In order to make that determination, all the fragmented transmission packets will need to be de-fragmentized or re-assembled with the lead fragmented transmission packet 230. With internal fragmentation, each fragmented transmission packet 330 and 340 has the header information sufficient to make these handling and prioritization determinations so there is no need to de-fragment or re-assemble all the fragmented transmission packets. But, by including additional encapsulation header information on each fragmented transmission packet 330 and 340, there is a substantial increase in the overhead of these transmission packets (and decrease in the effective data throughput) for the system, which wastes system resources.
Traffic parameters and application traffic characteristic parameters were analyzed to determine what is the best type of fragmentation to use on the system. The results at Table I shown below show the results of analysis for different application traffic such as traffic involved with interactive gaming, VoIP, Video Conference, streaming media, information technology, media content and WAP. The results of traffic parameter research for FTP, web browsing/HTTP, video streaming, VoIP, and interactive gaming are shown in Table II.
Characteristic Parameters
)
at
)
)
5
4
)
Control
, Movie Download
indicates data missing or illegible when filed
] = 50 ms latency <200 ms for IPTV;
indicates data missing or illegible when filed
Different models of traffic capacity and flow for different fragmentation protocols (internal vs. external) were analyzed, where a maximum transmission unit size was dynamically allocated (dynamic) or statically designated (static). The models for the transmission systems included weighting the processing costs associated with the home agent LMA/PDN 150, foreign agent MAG/SGW 130, the basestation eNB 120 and the mobile node 101, where each of these nodes is allocated a processing cost associated with assembly, processing, fragmentation and routing.
Additionally, two intermediate routers, one between the home agent LMA/PDN 150 and the foreign agent MAG/SGW 130 and the other between the foreign agent MAG/SGW 130, and the basestation eNB 120 were allocated a processing cost. The results of the modeling in the first and second scenario where the MTU for the intermediate routers was the lowest maximum of 1000B and 1500B packet size is shown below in Table III and IV.
The processor weightings for the home agent LMA/PDN 150, the foreign agent MAG/SGW 130 and the mobile node 101 processors were increased slightly for another set of modeling scenarios. The results of the modeling in the third and fourth scenario where the MTU for the intermediate routers was the lowest maximum of 1000B and 1500B packet size is shown below in Table V and VI.
For combinations of fragmentation are modeled above using slightly different MTU sizes for the intermediate routers. External and internal fragmentation were modeled with the combination of either static or dynamic allocation of the MTU size. By static MTU allocation, the maximum transmission unit size would be set by the system administrator, which is not deemed to optimize efficiency of the transmissions over the system. By dynamic MTU allocation, the MTU size would be set by the lowest maximum MTU size for any two nodes on the transmission path.
The modeling analysis demonstrated several key recommendations. First, using a dynamic allocation of the MTU size improves system capacity, and dynamic MTU allocation is required in IPv6 protocols. Second, if the nodes support internal fragmentation and external fragmentation can be avoided in the intermediate routers, system capacity will be improved. Third, the optimized model for transmissions is the use of internal fragmentation with dynamic MTU allocation, which increases the header overhead by 2-4% but reduces the processor (e.g. SGW and eNB) costs associated with assembly and fragmentation significantly and thereby reduces transmission time (e.g. total delay savings) by 10-20 msec.
If the packet can be initially fragmented in a manner to reduce fragmentation at the intermediate nodes, the system capacity will be improved. The optimal goal would be to initially fragment the packets into sizes less than the lowest maximum transmission unit (MTU) size, so that the intermediate nodes will not need to further fragment the packets, the system processing costs will be lowered, and the transmission time (delays) will be minimized.
In order to initially fragment the transmission packets into packets of a size less than the lowest MTU size, the lowest MTU size for the nodes on the transmission path must be discovered. The present invention accomplishes that goal in several different embodiments which are described with respect to three basic nodes on the transmission path—foreign agent LMA/PDN 150, intermediate router 140, and home agent MAG/SGW 130. The invention can be easily extended to include all nodes on the transmission path, all combinations of two nodes on the transmission path, uplink or downlink directions of communications along the transmission path, and external or internal fragmentation processing schemes.
The present invention is described in the embodiment described in
The home agent MAG/SGW 130 receives and accumulates comparable maximum transmission unit (MTU) information from other proxy binding update messages transmitted from the other routers and nodes on the transmission path, and uses the accumulated MTU information to calculate the lowest maximum transmission unit (MTU) for all the nodes on the transmission path. The home agent LMA/PDN 150 sends the foreign agent MAG/SGW 130 (and other nodes on the transmission path) a proxy binding update response message 420, which includes the lowest maximum transmission unit (MTU) for the nodes on the transmission path.
The home agent LMA/PDN 150 and/or the foreign agent MAG/SGW 130 then sets its MTU size based on this lowest maximum transmission unit for all the nodes on the transmission path, so that transmission packets processed by the home agent LMA/PDN 150 and/or foreign agent MAG/SGW 130, respectively, will be fragmented into a size that will not require any further processing or fragmentation by the intermediate entities and routers on the transmission path. This will eliminate the need for intermediate fragmentation processing along the transmission path, which will result in less processing delays and system resource usage and greater transmission throughput on the system.
As an alternative embodiment shown in
The intermediate router 140 responds to the home agent LMA/PDN 150 with an echo (“packet too big”) response message 520 if the MTU parameter value in the echo request message is greater than the lowest MTU value that can be accommodated by the intermediate router without requiring that intermediate router to further fragment the transmission packet during processing and transmission. If the home agent LMA/PDN 150 receives this type of echo response 520, it will re-send its echo transmission message 510 with a lower MTU parameter value. If the MTU parameter value in the echo transmission 510 is equal to or less than MTU value that can be accommodated by the intermediate router 140 without requiring that intermediate router to further fragment the transmission packet during processing and transmission, the intermediate router 140 will not send an echo (“packet too big”) response message to the home agent LMA/PDN 150. In this manner, the home agent LMA/PDN 150 will be able to determine the lowest MTU value for the intermediate router 140 when the home agent LMA/PDN 150 does not receive an echo response from any intermediate router 140.
After not receiving an echo response from the intermediate router 140, the home agent LMA/PDN 150 will transmit similar echo request messages to the other nodes on the transmission path, such as to the foreign agent MAG/SGW 130 in echo request 525. The foreign agent MAG/SGW 130 responds to the home agent LMA/PDN 150 with an echo (“packet too big”) response message 530 if the MTU parameter value in the echo request message is greater than the MTU value that can be accommodated by the foreign agent MAG/SGW 130 without requiring that foreign agent MAG/SGW 130 to further fragment the transmission packet during processing and transmission.
If the home agent LMA/PDN 150 receives this type of echo response, it will re-send its echo transmission message 535 with a lower MTU parameter value. If the MTU parameter value in the echo transmission 535 is equal to or less than MTU value that can be accommodated by the foreign agent MAG/SGW 130 without requiring that foreign agent MAG/SGW 130 to further fragment the transmission packet during processing and transmission, the foreign agent MAG/SGW 130 will not send an echo (“packet too big”) response message to the home agent LMA/PDN 150. Otherwise, the foreign agent MAG/SGW 130 will respond with an echo response 540. In this manner, the home agent LMA/PDN 150 will be able to determine the lowest maximum MTU value for the foreign agent MAG/SGW 130 when it does not receive an echo response from the foreign agent MAG/SGW 130.
After all the nodes in the transmission path have been polled by the home agent LMA/PDN 150, the home agent LMA/PDN 150 will be able to determine the lowest maximum MTU value for the nodes in the transmission path when the home agent LMA/PDN 150 does not receive an echo response from the foreign agent MAG/SGW 130 or any other intermediate routers 140 on the transmission path. The home agent LMA/PDN 150 can use an initial MTU parameter value that is a high value and work toward lower MTU parameter values for each node on the transmission path. The home agent LMA/PDN 150 and/or the foreign agent MAG/SGW 130 then sets its MTU size based on this lowest maximum transmission unit for all the nodes on the transmission path, so that transmission packets processed by the home agent LMA/PDN 150 and/or foreign agent MAG/SGW 130, respectively, will be initially fragmented into a size that will not require any further internal processing or fragmentation by the intermediate processing entities and routers on the transmission path. This will eliminate the need for further fragmentation processing along the transmission path, which will result in less processing delays and system resource usage and greater transmission throughput on the system.
As an alternative embodiment shown in
The intermediate router 140 responds to the home agent LMA/PDN 150 with response (“packet too big”) message 620 if the data packet size of message 610 is greater than the MTU value that can be accommodated by the intermediate router without requiring that intermediate router to further fragment the transmission packet during processing and transmission. If the home agent LMA/PDN 150 receives this type of response 620, it will re-send its data packet transmission message 610 with a smaller data packet size. If the data packet size in the message 610 is equal to or less than MTU value that can be accommodated by the intermediate router 140 without requiring that intermediate router to further fragment the transmission packet during processing and transmission, the intermediate router 140 will not send a response message 620 to the home agent LMA/PDN 150. In this manner, the home agent LMA/PDN 150 will be able to determine the lowest MTU value setting for the intermediate router 140 when it does not receive a response message 620 from any intermediate router 140.
After not receiving a “packet too big” (PTB) response 620 from the intermediate router 140, the home agent LMA/PDN 150 will transmit similar data packet message 630 to the other nodes on the transmission path, such as to the foreign agent MAG/SGW 130 in data packet message 630. The foreign agent MAG/SGW 130 responds to the home agent LMA/PDN 150 with a “packet too big” (PTB) response message 640 if the data packet size in the request message 630 is greater than the MTU value that can be accommodated by the foreign agent MAG/SGW 130 without requiring that foreign agent MAG/SGW 130 to further fragment the transmission packet during processing and transmission. If the home agent LMA/PDN 150 receives a “packet too big” (PTB) response message 640, it will re-send its data packet message 630 with a lower data packet size.
If the data packet size in the transmission 630 is equal to or less than lowest MTU value that can be accommodated by the foreign agent MAG/SGW 130 without requiring that foreign agent MAG/SGW 130 to further fragment the transmission packet during processing and transmission, the intermediate router 140 will not send PTB (“packet too big”) response message 640 to the home agent LMA/PDN 150. Otherwise, the foreign agent MAG/SGW 130 will respond with a PTB response 640. In this manner, the home agent LMA/PDN 150 will be able to determine the lowest MTU value for the foreign agent MAG/SGW 130 path when it does not receive a response 640 from the foreign agent MAG/SGW 130.
After sending out data packets of various sizes to the nodes on the transmission path, the home agent LMA/PDN 150 will be able to determine the lowest maximum MTU value for all the nodes on the transmission path when it does not receive a response from the foreign agent MAG/SGW 130 or any other intermediate routers 140 on the transmission path. The home agent LMA/PDN 150 can start with a high data packet size for these transmissions and reduce the data packet size to determine the lowest maximum transmission unit (MTU) size accommodated by all nodes on the transmission path.
The home agent LMA/PDN 150 and/or the foreign agent MAG/SGW 130 then sets its MTU size setting based on this lowest maximum transmission unit (MTU) size for each of the nodes on the transmission path, so that transmission packets processed by the home agent LMA/PDN 150 and/or foreign agent MAG/SGW 130, respectively, will be fragmented into a size that will not require any further processing or fragmentation by the other processing entities and intermediate routers on the transmission path. The home agent LMA/PDN 150 may send the lowest MTU size to the foreign agent MAG/SGW 130 in message 650, or may send regular data packets to the foreign agent MAG/SGW 130 in step 650. This will eliminate the need for further fragmentation processing along the transmission path, which will result in less processing delays and system resource usage and greater transmission throughput on the system.
As a further embodiment, a traceroute message is used to determine the lowest MTU value for the nodes on the transmission path is shown in
The home agent MAG/SGW 130 receives responses 720 from the intermediate router 140 and responses 730 from the foreign agent MAG/SGW 130 to the requests 710, which responses include the maximum transmission unit (MTU) size assigned to each foreign agent MAG/SGW 130 and/or intermediate router 140 in the transmission path, respectively. The home agent MAG/SGW 130 accumulates maximum transmission unit (MTU) information from messages 720 and 730 transmitted from the foreign agent MAG/SGW 130 and/or intermediate router 140, and uses the accumulated MTU information to calculate the lowest maximum transmission unit (MTU) for all the nodes on the transmission path. The home agent LMA/PDN 150 can also send the foreign agent MAG/SGW 130 (and other nodes on the transmission path) a message, which includes the lowest maximum transmission unit (MTU) for the nodes on the transmission path.
The home agent LMA/PDN 150 and/or the foreign agent MAG/SGW 130 then sets its MTU size based on this lowest maximum transmission unit for all the nodes on the transmission path, so that transmission packets processed by the home agent LMA/PDN 150 and/or foreign agent MAG/SGW 130, respectively, will be fragmented into a size that will not require any further processing or fragmentation by the intermediate entities and routers on the transmission path. This will eliminate the need for intermediate fragmentation processing along the transmission path, which will result in less processing delays and system resource usage and greater transmission throughput on the system.
While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention.
This application is related to Provisional Patent Application Ser. No. 61/053,485 filed on May 15, 2008, and priority is claimed for this earlier filing under 35 U.S.C. §119(e). The Provisional patent application is also incorporated by reference into this utility patent application.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2009/003046 | 5/15/2009 | WO | 00 | 11/9/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61053485 | May 2008 | US |
