Abstract:
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.

Description:
RELATED APPLICATION DATA 
       [0001]    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. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    A method and system for the transmission of fragmented packets on a packet-based communication network. 
       BACKGROUND OF THE INVENTION 
       [0003]    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. 
         [0004]    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. 
         [0005]    A “mobile node” encompasses PC&#39;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). 
         [0006]    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. 
       Registration of Mobile Node 
       [0007]    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. 
         [0008]    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. 
         [0009]    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. 
       Mobile Node Mobility 
       [0010]    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. 
         [0011]    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&#39;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. 
         [0012]    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&#39;s packets as the mobile node&#39;s care-of address. 
         [0013]    The home agent or local mobility anchor will confirm that the mobile node&#39;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. 
       Fragmentation of Tunneled Packet Transmissions 
       [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]    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. 
         [0019]    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. 
       SUMMARY OF THE INVENTION 
       [0020]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    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: 
           [0022]      FIG. 1  is a mobile IP-based communication system as used in the present invention, 
           [0023]      FIG. 2  is a graphic depiction of encapsulation/external fragmentation of a transmission packet; 
           [0024]      FIG. 3  is a graphic depiction of internal fragmentation/encapsulation of a transmission packet; 
           [0025]      FIG. 4-7  are protocols according to the present invention for discovery of the lowest maximum transmission unit for an exemplary set of nodes (foreign agent, intermediate router, and home agent) in the transmission path. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    In  FIG. 1 , the overall architecture of the IP-based mobile system  100  is shown with user equipment  101  or mobile node  101  coupled to a transceiver station (Xan)  110  by a wireless connection. The connection to the mobile node may also be a land based connection for the purposes of this invention. 
         [0027]    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 Network 1   125  by connection  122 . The IP Network 1   125  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 Network 2   135  by connection  132 . 
         [0028]    The IP Network 2   135  is coupled to an intermediate router RTR  140  by connection  137 . The intermediate router RTR  140  is coupled to the IPNetwork 3  by connection  142 , and the IPNetwork 3  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 . 
         [0029]    In the present invention, the home agent LMA/PDN  150  encapsulates a transmission packet  201  shown in  FIG. 2  for transmission to the mobile node  101 . The transmission packet  201  is shown with IP header  202  and data payload  203 , and once encapsulated the transmission packet  205  has an encapsulation IP header  210 , UDP designation  211 , GTP designation  213 , IP header  202  and data payload  203 . If the home agent LMA/PDN  150  (or the other nodes on the network) conducts external fragmentation of the encapsulated packet  205 , the home agent LMA/PDN  150  will generate fragmented transmission packets  230  and  220 . Fragmented transmission packet  230  will have a fragmented encapsulated IP header  232 , UDP designation  211 , GTP designation  213 , IP header  202  and a portion of the data payload  203  designated as data payload  232 . The second fragmented transmission packet  220  will have the fragmented encapsulated IP header  235  and a second portion of the data payload  203  designated as data payload  222 . 
         [0030]    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  FIG. 3  has an IP header  303  and a data payload  302 , and upon fragmentation, the transmission packets  310  and  322  are generated. Transmission packet  310  has the IP header  303  and a portion of the data payload  302  designated as data payload  312 . 
         [0031]    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 . 
         [0032]    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) 
         [0033]    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. 
         [0034]    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. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Application Tra           Characteristic Parameters 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 A           
               
               
                 Application 
                   
                 Through          ) 
                 Mean p           at 
                 Mean Duration 
                   
                   
                 (by          ) 
               
             
          
           
               
                 Class 
                 Applications 
                 Min 
                 Max 
                 cell size           
                 (B          ) 
                 DLF 
                 ULF 
                 DIL 
                 UIL 
               
               
                   
               
             
          
           
               
                 Interactive 
                 Interactive Gaming 
                 
                           
                 
                            5 
                   
                 3000 
                 1 
                 0.2 
                 300 
                 300 
               
               
                 Gaming 
               
               
                 VoIP,            
                 VoIP 
                 3 
                 64 
                   
                 120 
                 1 
                 1 
                 40 
                 40 
               
               
                 Conference 
                 Video Te           
                 32 
                 3          4 
                   
                 1500 
                 1 
                 1 
                 500 
                 500 
               
               
                 Streaming Mode 
                 M           
                 5 
                 125 
                   
                 
                           
                 
                 1 
                 0 
                 1500           
                 40 
               
               
                   
                 Video Clips (          ) 
                 20 
                 364 
                   
                 3000 
                 1 
                 0 
                 1530           
                 40 
               
               
                   
                 Movie Streaming (PTY) 
                 300 
                 3803 
                   
                 3800 
                 1 
                 0 
                 1500           
                 40 
               
               
                   
                   
                   
                 (           
               
               
                   
                   
                   
                 HDTV) 
               
               
                 Information 
                 IM 
                 10 
                 20 
                 0.088 
                 40 
                 1 
                 0.07 
                 200 
                 200 
               
               
                 Technology 
                 Web Browsing 
                 500 
                   
                 54.3 
                 Mean Interval: 30 
                 1 
                 0 
                 350 
                 40 
               
               
                   
                   
                   
                   
                   
                 seconds 
               
               
                   
                 E           
                 500 
                   
                 10.7 
                   
                 1 
                 0.5 
                 500 
                 400 
               
               
                   
                 E           
                 500 
                   
                 162 
                   
                 1 
                 0.5 
                 1000 
                 1000 
               
               
                   
                 T           
                 10 
                 20 
                 0.5 
                   
                 1 
                 0 
                 1000 
                 200 
               
               
                             Control 
                            , Movie Download 
                 1000 
                   
                 2000 
                 Mean Interval: 180 
                 1 
                 0.1 
                 1500           
                 40 
               
               
                   
                 (FTP) 
                   
                   
                   
                 seconds 
               
               
                   
                 PSP 
                 500 
                   
                 1000 
                   
                 1 
                 1 
                 200 
                 200 
               
               
                 WAP 
                   
                 10 
                 20 
                 0.512 
                   
                 1 
                 0 
                 200 
                 200 
               
               
                   
               
               
                             indicates data missing or illegible when filed 
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE II 
               
               
                   
               
               
                 Application 
                 Traffic Parameters 
                 Outage Limit and Definition (performance reference) 
                 
                           
                 
               
               
                   
               
             
             
               
                 FTP 
                 File size: Mean 2M bytes (max 5M bytes) 
                 2% outage based on user packet call throughput &lt; P 
                 10% 
               
               
                   
                 Reading time: Mean 180 seconds 
                 P = 128 Kbps for BW &gt; 2.5 MHz 
               
               
                   
                   
                 No delay not throughput guarantees 
               
               
                 Web Browsing/ 
                 The total mean object file size is about 
                 2% outage based on user packet call throughput &lt; Q 
                 20% 
               
               
                 HTTP 
                 64k byte 
                 Q = 128 Kbps for BW &lt; 2.5 MHz 
               
               
                   
                 Reading time; Mean −30 seconds 
                 No delay not throughput guarantees 
               
               
                 Video 
                 500k bps source could be appiled 
                 2% outage based on user having &gt;2% dropped 
                 20% 
               
               
                 Streaming 
                 Typical packet size 1500 byte (DL) 
                 packets (recommended packet loss rates in the range 
               
               
                   
                 Long duration 3000 seconds 
                 of 10           
               
               
                   
                   
                 Maximum acceptable jitter delay factor (DF) 
               
               
                   
                   
                 [          ] = 50 ms latency &lt;200 ms for IPTV; 
               
               
                   
                   
                 Delay tolerated of streaming at stored video: −5 secs 
               
               
                   
                   
                 and −400 ms for Real-time interactive video: 
               
               
                 VoIP 
                 Average throughput 25 kbps 
                 2% outage based on user having &lt;98% of its speech 
                 30% 
               
               
                   
                 Average packet size 40 byte payload with 
                 frames delivered successfully within [40] ms 
               
               
                   
                 20 ms frames 
                 (air interface delay). 
               
               
                   
                 Average duration 120 seconds 
                 Consecutive speech frames erased &lt; [0.05]% of time 
               
               
                   
                   
                 Recommended upper limit for end to end 
               
               
                   
                   
                 delay −150 ms 
               
               
                 Interactive 
                 Minimum 50 kbps throughput 
                 A mobile network gaming user is in outage if the 
                 20% 
               
               
                 Gaming 
                 Long duration 3600 seconds 
                 average pocket delay &gt;60 ms 
               
               
                   
                 Average packet size 300 byte 
                 Maximum delay to all uplink packets: 160 ms 
               
               
                   
                   
                 Jittering Similar to real-time interactive video 
               
               
                   
               
               
                             indicates data missing or illegible when filed 
               
             
          
         
       
     
         [0035]    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. 
         [0036]    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. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE III 
               
             
             
               
                   
                   
               
               
                   
                 Gain 
               
             
          
           
               
                   
                 PGW 
                 R1 CPU 
                 SGW 
                 R2 CPU 
                 eNB 
               
               
                 LTE Model # 
                 CPU 
                 cost 
                 CPU 
                 cost 
                 CPU 
               
               
                   
               
               
                 1 (Static MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                   0% 
                   0% 
               
               
                 2 (Dyn MTU: Ext Frag) 
                   0% 
                  100% 
                  16% 
                  100% 
                   8% 
               
               
                 3 (Static MTU: Int Frag) 
                   −8% 
                   0% 
                   0% 
                   0% 
                   8% 
               
               
                 4 (Dyn MTU: Int Frag) 
                   −8% 
                  100% 
                  32% 
                  100% 
                  25% 
               
               
                   
               
             
          
           
               
                 Traffic mix 
                 Comparing Model 4 with Model 1 
               
               
                   
               
             
          
           
               
                 10% 
                 −0.8% 
                 10.0% 
                 3.2% 
                 10.0% 
                 2.5% 
               
               
                 20% 
                 −1.5% 
                 20.0% 
                 6.5% 
                 20.0% 
                 4.9% 
               
               
                 30% 
                 −2.3% 
                 30.0% 
                 9.7% 
                 30.0% 
                 7.4% 
               
               
                 40% 
                 −3.1% 
                 40.0% 
                 12.9%  
                 40.0% 
                 9.8% 
               
               
                 50% 
                 −3.8% 
                 50.0% 
                 16.1%  
                 50.0% 
                 12.3%  
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE IV 
               
             
             
               
                   
                   
               
               
                   
                 Gain 
               
             
          
           
               
                   
                 PGW 
                 R1 CPU 
                 SGW 
                 R2 CPU 
                 eNB 
               
               
                 LTE Model # 
                 CPU 
                 cost 
                 CPU 
                 cost 
                 CPU 
               
               
                   
               
               
                 1 (Static MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                   0% 
                   0% 
               
               
                 2 (Dyn MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                   0% 
                   0% 
               
               
                 3 (Static MTU: Int Frag) 
                   −8% 
                   0% 
                  19% 
                   0% 
                  18% 
               
               
                 4 (Dyn MTU: Int Frag) 
                   −8% 
                   0% 
                  19% 
                   0% 
                  18% 
               
               
                   
               
             
          
           
               
                 Traffic mix 
                 Comparing Model 4 with Model 1 
               
               
                   
               
             
          
           
               
                 10% 
                 −0.8% 
                 0.0% 
                 1.9% 
                 0.0% 
                 1.8% 
               
               
                 20% 
                 −1.5% 
                 0.0% 
                 3.8% 
                 0.0% 
                 3.6% 
               
               
                 30% 
                 −2.3% 
                 0.0% 
                 5.8% 
                 0.0% 
                 5.4% 
               
               
                 40% 
                 −3.1% 
                 0.0% 
                 7.7% 
                 0.0% 
                 7.1% 
               
               
                 50% 
                 −3.8% 
                 0.0% 
                 9.6% 
                 0.0% 
                 8.9% 
               
               
                   
               
             
          
         
       
     
         [0037]    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. 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE V 
               
             
             
               
                   
                   
               
               
                   
                 Gain 
               
             
          
           
               
                   
                 PGW 
                 R1 CPU 
                 SGW 
                 R2 CPU 
                 eNB 
               
               
                 LTE Model # 
                 CPU 
                 cost 
                 CPU 
                 cost 
                 CPU 
               
               
                   
               
               
                 1 (Static MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                   0% 
                   0% 
               
               
                 2 (Dyn MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                   0% 
                   0% 
               
               
                 3 (Static MTU: Int Frag) 
                   −6% 
                   0% 
                   0% 
                   0% 
                  12% 
               
               
                 4 (Dyn MTU: Int Frag) 
                   −6% 
                   0% 
                   0% 
                   0% 
                  12% 
               
               
                   
               
             
          
           
               
                 Traffic mix 
                 Comparing Model 4 with Model 1 
               
               
                   
               
             
          
           
               
                 10% 
                 −0.6% 
                 0.0% 
                 0.0% 
                 0.0% 
                 1.2% 
               
               
                 20% 
                 −1.3% 
                 0.0% 
                 0.0% 
                 0.0% 
                 2.5% 
               
               
                 30% 
                 −1.9% 
                 0.0% 
                 0.0% 
                 0.0% 
                 3.7% 
               
               
                 40% 
                 −2.6% 
                 0.0% 
                 0.0% 
                 0.0% 
                 4.9% 
               
               
                 50% 
                 −3.2% 
                 0.0% 
                 0.0% 
                 0.0% 
                 6.1% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE VI 
               
             
             
               
                   
                   
               
               
                   
                 Gain 
               
             
          
           
               
                   
                 PGW 
                 R1 CPU 
                 SGW 
                 R2 CPU 
                 eNB 
               
               
                 LTE Model # 
                 CPU 
                 cost 
                 CPU 
                 cost 
                 CPU 
               
               
                   
               
               
                 1 (Static MTU: Ext Frag) 
                   0% 
                   0% 
                   0% 
                  0% 
                   0% 
               
               
                 2 (Dyn MTU: Ext Frag) 
                   0% 
                  100% 
                  14% 
                 100% 
                   8% 
               
               
                 3 (Static MTU: Int Frag) 
                   −6% 
                   0% 
                 −14%  
                  0% 
                   4% 
               
               
                 4 (Dyn MTU: Int Frag) 
                   −6% 
                 100% 
                  14% 
                 100% 
                  19% 
               
               
                   
               
             
          
           
               
                 Traffic mix 
                 Comparing Model 4 with Model 1 
               
               
                   
               
             
          
           
               
                 10% 
                 −0.6% 
                 10.0% 
                 1.4% 
                 10.0% 
                 1.9% 
               
               
                 20% 
                 −1.3% 
                 20.0% 
                 2.8% 
                 20.0% 
                 3.6% 
               
               
                 30% 
                 −1.9% 
                 30.0% 
                 4.2% 
                 30.0% 
                 5.7% 
               
               
                 40% 
                 −2.6% 
                 40.0% 
                 5.6% 
                 40.0% 
                 7.6% 
               
               
                 50% 
                 −3.2% 
                 50.0% 
                 6.9% 
                 50.0% 
                 9.5% 
               
               
                   
               
             
          
         
       
     
         [0038]    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. 
         [0039]    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. 
         [0040]    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. 
         [0041]    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. 
         [0042]    The present invention is described in the embodiment described in  FIG. 4  as follows. The foreign agent MAG/SGW  130  transmits a proxy binding update message  410  to the home agent LMA/PDN  150  with the foreign agent&#39;s maximum transmission unit (MTU) size, which is the maximum size of packet that can be received and processed by the foreign agent MAG/SGW  130  without requiring that foreign agent entity to further fragment the transmission packet during processing and transmission. 
         [0043]    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. 
         [0044]    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. 
         [0045]    As an alternative embodiment shown in  FIG. 5 , the home agent LMA/PDN  150  may determine what the lowest MTU value for intermediate router  140  by sending an echo transmission request  510  to the intermediate router  140  with an initial MTU parameter value of the maximum transmission unit (MTU). This initial MTU parameter value will be derived from information set by the foreign agent MAG/SGW  130 , or it may be set as a predetermined high MTU value. 
         [0046]    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 . 
         [0047]    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. 
         [0048]    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 . 
         [0049]    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. 
         [0050]    As an alternative embodiment shown in  FIG. 6 , the home agent LMA/PDN  150  may determine what the lowest MTU value for intermediate router  140  by sending a data packet message  610  to the intermediate router  140 , where the data packet size corresponds to the initial MTU parameter value of the maximum transmission unit (MTU). This data packet size and initial MTU value may be received from the foreign agent MAG/SGW  130 , or it may be set as a predetermined high MTU value. 
         [0051]    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 . 
         [0052]    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. 
         [0053]    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 . 
         [0054]    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. 
         [0055]    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. 
         [0056]    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  FIG. 7 . The home agent LMA/PDN  150  sends a traceroute echo request message  710  to the foreign agent MAG/SGW  130  and each intermediate router  140  in the transmission path. The request message  710  includes a request to each of the foreign agent MAG/SGW  130  and intermediate router  140  in the transmission path, said request that each of these entities send the home agent LMA/PDN  150  the maximum transmission unit (MTU) size assigned to each foreign agent MAG/SGW  130  and/or intermediate router  140  in the transmission path. The MTU assigned to each entity is the maximum size of packet that can be received and processed by that entity (e.g. foreign agent MAG/SGW  130  or intermediate router  140 ) without requiring that entity to further fragment the transmission packet during processing and transmission. 
         [0057]    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. 
         [0058]    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. 
         [0059]    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.