Maintaining an existing connection between nodes
Contents
1. Jeu 93 g Jppy uono uuoo 491118159 ei uuoo ues g Jppy UOI O UUu09 JO SS ppE Ju umno uuoju ZS 85 1591 9p M ss Ju uuusi qe S9 91 uono uuo2o 10 59 S uonoauuoo Jo uolnd o1 d 0 8 1PPV TLL d Jppy ss ippe mou u uino ubisse cs 89 Jake Uono uuoo uoneoldde JouBlssy Ippy M S Uppy NN g pv a HOES NUH v Jan 3 2008 Sheet 3 of 5 US 2008 0002686 A1 Patent Application Publication LV s pou MN 0 J M 9 SUE Bi 2 p usilqe1s 1 g Jppy AI9991 Jppe 19 OV Jo d 55 yun 1 usilqe s 81 401 0 yun guppy Buuoyluoul Jppe snolaaid yun Bunjnsuoo yun 10 29 p Jan 3 2008 Sheet 4 of 5 US 2008 0002686 A1 Patent Application Publication kg SOPOU MN WOJ O py N Jppy ye Buiddew weu o ss spe 15 g Jppy Buisn uono uuoo usilqe s 9 1 Mag ippv JO JouBissv a PPY mou yun 51 4 159 1 Al RS nb l uono uuoo o ne Janie SUBL 68 y n u nd ol d uono uuoo Jan 3 2008 Sheet 5 of 5 US 2008 0002686 A1 Patent Application Publication S 12. 9g PPY g W3INW dn yoo ayepdn sessaippe LSY N poubisse jo WIN SUBI 95 y2 3 1 yun juswebeuew 1u uno JO s nb ssolppe mau peubisse SV s pou ie M S Jppy pou juswabeuew ssaippy US 2008 0002686 A1 MAINTAINING AN EXISTING CONNECTION BETWEEN NODES FIELD OF THE INVENTION 0001 The present invention relates to a method of main taining an existing connection between a first node and a second node communicating with each other via a connec tion within a communication network wherein data com municated between the nodes via the connection are com municated on the basis of addresses assigned to the respective nodes and at least one of the addresses changes during the connection as vvell as to a corresponding system and the respective nodes thereof BACKGROUND OF THE INVENTION 0002 With recent progress in communication technol ogy various scenarios will arise in which an address of a node may change during a connection with another node For example a connection between nodes is broken or generally exhibits an outage e g due to fast moving termi nal nodes in mobile networks or the like Nodes such as terminals of end users or even servers acting as a node with which a terminal is communicating will however experi ence such outage e g caused by a break failure in the connection
3. 0118 The invention is generally applicable to similar cases in other tunnelling scenarios and protocols It is also be generally applicable to any network where the IP address changes and where there is a naming service such as a dynamic DNS which is updated after the new address has been obtained from an address assigning server or node 0119 As disclosed above the present invention refers to a method performed in and corresponding nodes constituting a system which is configured to maintain an existing con nection between a first node A and a second node B communicating with each other via a connection within a communication network Data are communicated between the nodes A B via the connection on the basis of addresses assigned to the respective nodes The addresses are managed by an address management node Addr_Serv of the commu nication network The system comprises a detector unit A2 at the first node A configured to detect an outage of the existing connection between the nodes A B a consulting unit A3 at said first node A configured to consult after detecting the outage of the connection the address manage ment node Addr Serv of the communication network to verify the address assigned to the second node B a trans ceiver unitAS1 at said address management node Addr_ Serv configured to return a current address assigned to the second node B responsive to a request from the consulting unit to the first node and a connect
4. IP address of the second node B has changed Node A starts resending of the packets to the new IP address of node B before the appli cation or the underlying connection is timed out in order to maintain the connection 0062 Note that the expression addresses being managed by an address management node of the communication US 2008 0002686 A1 network is to a certain extent a simplification for explana tory purposes The invention relates for example to a gen eralization of a scenario where dynamic DNS is used in the IP world Each node has an address IP address and a name hostname e g www nokia com The communica tion network provides a name to address mapping function DNS that a node can use to learn the address of another node based on the name The invention is particularly useful in cases where the address of the node may occasionally change and where the node consequently updates the address mapped to its name in the name to address function which implies in a specific example that the DNS is a dynamic DNS For the purposes of this invention the name can be assumed unchanging 0063 Thus address management describes the keeping track of the address assigned to a node of a given name and the possibility to provide for a looking up of the node to address assignment Assigning of the addresses can be accomplished separately from the address management e g by a DHCP server entity although both functions c
5. address from a memory unit of the address management node 31 An address assignor node comprising a node configured to assign a current address to a second node the assigned address being associated with a life time attribute for the current address for caching address_to_node_name mapping entries in other nodes than the address management node the lifetime attribute being set to zero or about 0 32 A system configured to maintain an existing connec tion between a first node and a second node comprising detecting means for detecting by the first node an outage of an existing connection between the first and second nodes consulting means for consulting by said first node after detecting the outage of the connection an address management node of a communication network to verify an address assigned to the second node returning means for returning from said address manage ment node a current address assigned to the second node and establishing means for re establishing the existing con nection by said first node based on the current address assigned to the second node 33 Amethod as recited in claim 1 wherein said first node and said second node communicate via a connection within a communication network 34 Asystem as recited in claim 12 wherein said first node and said second node are configured to communicate with each other via a connection within a communication net work
6. clarity of the explanation of the present invention these aspects of the present invention are described with reference to separated figures in order to keep the explanation simple It is how ever to be understood that each node can combine the functionality of node A as described herein as well as of node B as described herein Also any of the nodes may be a terminal or client e g of a end user or a server within a network 0102 FIG 3 shows a block circuit diagram of a node node A referred to in the present invention as a first node and in connection therewith one first aspect of the present invention is explained US 2008 0002686 A1 101031 As shown in FIG 3 node A has a transceiver unit A1 which is configured to receive and to send messages data from and to the network and or other nodes within the netvvork Those nodes can be communication partner nodes or other netvvork entities constituting the communication netvvork It is to be noted that any node here need not necessarily be a terminal of a user but may also be a netvvork node such as a server The node comprises further a detector unit A2 vvhich is configured to detect an outage of an existing connection betvveen this node and another node via a communication netvvork The detector unit is either con figured to receive an error message via a receiving unit not shown constituting part of the transceiver unit Al trans mitter receiver or is configured to detect the
7. communication network to verify an address assigned to the second node a transceiver unit at said address management node configured to return a current address assigned to the second node responsive to a request from the consult ing unit to the first node and a connection re establisher unit at said first node con figured to re establish the connection based on a current address assigned to the second node wherein data is communicated between the first and second nodes on the basis of addresses assigned to the respective nodes and wherein the addresses are man aged by the address management node of the commu nication network 13 The system according to claim 12 wherein said detector unit comprises a receiving unit configured to receive an error message informing the first node that a message addressed from the first node to the second node was not delivered 14 The system according to claim 12 wherein said detector unit comprises a receiving unit configured to experience a timeout when waiting for a response or acknowledgement from the second node 15 The system according to claim 12 further comprising an address assignor node configured to assign a current address to the second node the assigned address being associated with a life time attribute for the current address for caching address_to_node_name mapping entries in other nodes than the address management node the lifetime attribute being set to zero or abou
8. interval expires 0044 the monitoring unit is configured to stop the timer unit and to end the process of re establishing the connection when the connection to the second node could be re established by using the earlier known address of the second node before the time interval expires 0045 data communicated between the nodes via the connection are data relating to an application carried on a layer above a layer of the connection and the time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 0046 the outage of the connection is based on a change of the logical or physical channels of the connection 0047 the connection changes from one type of connec tion to another type of connection 0048 In addition there is disclosed a node comprising 0049 a detector unit configured to detect an outage of an existing connection between the first node and a second node via a communication network a consulting unit con figured to consult after detecting the outage of the connec tion an address management node of a communication network to verify the address assigned to the second node and a connection re establisher unit configured to re estab lish the connection based on a current address assigned to the second node Jan 3 2008 0050 said detector unit comprises a receiving unit con figured to receive an error message informing the first node that a m
9. memory depends on the size of nodes network addresses of nodes managed by the address management node 0113 Thus as explained herein before in detail but now stated in other words the invention could be described briefly as follows A first node A has set up e g a real time communication with a second node B For some reasons the address of the second node B changes e g the IP address in case of an IP based connection Concerning Node B there is an immediate update of its address associated to its node name to an address mapping table look up table in the address management node s memory such as DNS server s memory In this context optionally a life time attribute for caching this mapping information in other nodes such as time to live TTL is set to 0 or close to zero Node A detects that it can t reach node B anymore Node A starts a timer and optionally tries to re establish the connection to node B with the last known e g IP based address settings The timer expires before the upper layer applications are timed out When the timer expires node A re checks the IP address of node B via e g DNS query to retrieve the current new address Node A re establishes the connection by using the Jan 3 2008 returned IP addresses from the DNS query concerning node B s address to name mapping 0114 Hereinbefore the present invention has been described on a general level as it is applicable to nearly all address based comm
10. new address to node name mapping received from the address assignor node or some other source e g from the node which received a new assigned address itself such as the node B Such new address is forwarded to a management unit AS2 The management unit AS2 of the address management node is configured to manage responsive to receipt of such a new address from the address assignor node or from the node itself a current address of the second node B This means that the manage ment unit AS2 updates a look up table in a memory AS3 of the address management node with the new current address i e it replaces address ADDR_B for node B by ADDR_B for node B This assigned new address ADDR B can optionally be informed via the transceiver unit AS1 of the address management node to the second node node B in case of a scenario as explained above related to step S7 in FIG 2 Furthermore associated to the management unit AS2 the address management node comprises a memory AS3 in which addresse s to node name mappings are maintained Assigned addresses are updated therein by means of a write operation and read therefrom by means of a fetch operation The memory unit AS3 is thus e g a RAM or a Flash memory or any other memory to which data can be written and from which data can be read In the presently illustrated example this memory contains address ADDR_A for node A and the newly assigned current address ADDR_ B for node B The size of this
11. response or acknowledgement from the second node 4 The method according to claim 1 further comprising assigning to the second node a current address wherein the assigned address is associated with a life time attribute for the current address for cach ing address_to_node_name mapping entries in other nodes than the address management node the life time attribute being set to zero or about 0 5 The method according to claim 1 wherein said con sulting comprises monitoring a time interval by said first node responsive to the detection of the outage realizing by said first node that the time interval expired requesting by the first node the current address of the second node from the address management node responsive to realizing that the time interval has expired 6 The method according to claim 5 wherein said con sulting comprises trying to re establish the connection to the second node by using an earlier known address of the second node until the time interval expires 7 The method according to claim 6 wherein the timer is stopped and the process of re establishing the connection ends when the connection to node B could be re established by using the earlier known address of the second node before the time interval expires 8 The method according to claim 5 wherein data communicated between the nodes via the connection are data relating to an application carried on a layer above a layer of the c
12. the address assignor node sets a lifetime attribute for caching of the address to name mapping of the second node B in other nodes than the ADDR_SERV to zero or close to 0 For example in case of the address assignment being performed in line with DNS Domain Name Service the lifetime attribute is TTL Time To Live for caching and this attribute is set to zero or close to 0 By doing this it is avoided that the address to node name mapping is cached in other nodes than the ADDR_SERV Thus a DNS query on the node name will result always in an address look up operation done by or at the ADDR_SERV node The assigned new address ADDR_B is informed to the address management node ADDR SERV e g in step S7a and further to the node B in step S7 This informing of the new address can occur in two different transmissions or in one transmission e g S7a which is relayed S7 from the address management node further to the node concerned node B 0090 Note that such a lifetime attribute for caching such as the TTL value is typically set just once per given address to name mapping entry i e DNS entry at the time of the creation of the entry In rare cases it might be updated too if some maintenance work is done Thus no changes are usually done to the lifetime attribute e g TTL at the time when the e g IP address changes The e g TTL value is already zero or near zero when the address changes and the invention is applied This being sa
13. to another experiencing a change of the node s IP address of the IPv4 connection The node may also change intentionally the IPv4 connectivity e g from GPRS to WLAN if WLAN becomes available which could also lead to a change of the IPv4 connection node address 0014 Ifthe underlying IPv4 connectivity experiences an outage the same applies as well to the IPv6 tunnel and possible peer to peer connections with applications that have been established between this node and other nodes 0015 This results in applications losing the peer to peer connections and requiring from the user manual re estab lishment of the connection 10016 In case of e g group VOIP Voice over IP com munication as an application example with members of the VOIP group moving around in a metropolitan area the usability of the application would be ruined if in practice every time you want to communicate with the group you would first have to manually check with whom you have lost the connection and re establish the connections manually Otherwise the peers nodes that have dropped the peer to peer connection with your node will not receive the VOIP message US 2008 0002686 A1 0017 To summarize there are situations emerging which lead to the problem of how a node can maintain IP connectivity or generally an ongoing communication con nection with another node whose IP address changes with out terminating the application s running between the no
14. US 20080002686A1 a2 Patent Application Publication ao Pub No US 2008 0002686 A1 as United States Valli et al 43 Pub Date Jan 3 2008 MAINTAINING AN EXISTING CONNECTION BETVVEEN NODES 54 75 Inventors Jyrki Valli Tampere FT Seppo Pohja Tampere FI Correspondence Address SQUIRE SANDERS amp DEMPSEY L L P 14TH FLOOR 8000 TOWERS CRESCENT TYSONS CORNER VA 22182 73 21 22 Assignee Nokia Corporation Appl 11 642 638 Filed Dec 21 2006 30 Foreign Application Priority Data Jun 30 2006 EP 06 116 432 3 Publication Classification Int CI H04L 12 56 51 2006 01 US Chu u Ziyana 370 389 52 Node A detector unit previous addr Addr_B 75 connection re establisher unit monitoring unit 57 ABSTRACT The present invention refers to a method performed in and corresponding nodes constituting a system vvhich is config ured to maintain an existing connection betvveen a first node A and a second node B communicating vvith each other via a connection within a communication network Data is communicated between the nodes A B via the connection on the basis of addresses assigned to the respective nodes The addresses are managed by an address management node Addr_Serv of the communication network The system comprises a detector unit A2 at the first node A con figured to detect an outage of t
15. as rather inconvenient A temporary connection outage need not necessarily be caused by a connection failure which is usually related to e g a failure on the physical layer though this is not excluded here Rather a connection outage as discussed in the present invention is mostly due to a node address change caused e g by a physical connection change or the like 0003 For the purpose of the present invention to be described herein below it should be noted that 0004 a node may for example be any kind of commu nication device such as a wireless or wired device e g personal computer mobile phone or the like irrespective of a specific standard to which these conform as long as they are compatible to a communication network a node may be a terminal also referred to as client or a server 0005 for the communication network any suitable pro tocol for operating message exchange is possible only as an example it is noted that packet based communication net works such as IP based networks e g conforming to 1 4 or IPv6 are particularly suitable to be used with the present invention 0006 method steps likely to be implemented as software code portions and being run using a processor at one of the nodes are software code independent and can be specified using any known or future developed programming lan guage as long as the functionality defined by the method steps is preserved 0007 generally any method step is suitabl
16. cond type of connection such as WLAN or GPRS This is a Jan 3 2008 special case of a handover where the handover occurs to a different connection type In another case the change of the logical or physical channels can for example be based on a handover within the same connection type In both cases the address of the remote node i e node B when referring to the example described here could change but could also remain the same 0098 During the monitored time interval which is moni tored by the timer the first node A tries to re establish the connection based on the previous known address ADDR_B of the second node B see S10 If this was found to be successful in step 511 the connection is continued in S12 this might be for example the case if a handover within the same connection type happens e g between two adjacent base stations However such situation is not the main concern of the present invention 0099 In such case the timer is stopped and the process of re establishing the connection ends when the connection to node B could be re established by using the earlier known address of node B ADDR_B before the time interval expires 101001 If however the connection re establishment to the known previous address ADDR_B was found to be not successful in Step S1 it is checked in step S13 whether the timer expired If not the processing at node A returns from step S13 to step S10 If it is found in step S13 t
17. connection outage by itself e g by experiencing a timeout when waiting for a response from the other node For example instead of an error message the detector may await an acknowledgment message and the absence of receipt of such acknowledgement message for a defined time period may result in detection of the connection outage The receiving unit is configured to receive an error message from the network informing the first node about the connection outage and forwards it internally within the node A to the detector unit A2 Alternatively the receiving unit is con figured to normally receive an acknowledgement message and to forward it to the detector unit The detector unit is connected to a consulting unit A3 The detector unit thus triggers the consulting unit A3 upon detecting an outage of an existing connection The consulting unit is configured to consult after detecting the outage of the connection an address management node ADDR_SERV of the communi cation network to verify the address assigned to the second node B communication partner node such as a second terminal or a server The consulting unit is equipped with a monitoring unit A4 comprising a timer configured to moni tor a time interval responsive to the detection of the outage The monitoring unit timer A4 is configured to realize that the time interval expires According to an option during the timer monitoring the time interval the consulting unit may instruct a c
18. cting comprises receiving an error mes sage that the connection to the second node is interrupted 0029 said detecting comprises experiencing a timeout when waiting for a response or acknowledgement from the second node 0030 the method further comprises assigning to the second node a current address wherein the assigned address is associated with a life time attribute for the current address for caching address_to_node_name mapping entries in other nodes than the address management node the lifetime attribute being set to zero or about 0 0031 said consulting comprises monitoring a time inter val by said first node responsive to the detection of the outage realizing by said first node that the time interval expired requesting by the first node the current address of the second node from the address management node respon sive to realizing that the time interval has expired 0032 said consulting comprises trying to re establish the connection to the second node by using an earlier known address of the second node until the time interval expires 0033 the timer is stopped and the process of re estab lishing the connection ends when the connection to node B could be re established by using the earlier known address of the second node before the time interval expires 0034 data communicated between the nodes via the connection are data relating to an application carried on a layer above a layer of the connection and a
19. d to the node by e g a DHCP Dynamic Host Configuration Protocol server for a lease period Upon lease expiration the node gets a different address from the DHCP server 0021 The public address is assigned to the node by e g a NAT Network Address Translation or NAPT Network Address Port Translation server which sud denly assigns a different address to the node 0022 The public address is assigned to the node by e g a tunnelling server which suddenly assigns a different address to the node 0023 Thus problems as those mentioned in the above examples may occur on any network where the node address may change without a warning e g on the Internet if the server uses dynamic DNS and its address changes say under DHCP 0024 Furthermore in connection with IP based net works Dynamic Domain Name Service DynDNS is widely know in the Internet and has been into use there for a long time Nevertheless DynDNS has not been used as a mechanism to recover from node address changes for real time traffic in a fast enough manner to prevent terminating of e g the real time application running on top of the connection Recovery from IP address changes for a stan dard DynDNS implementation is slow and takes some time in the area of minutes for example the minimum time to live time for caching of DNS entries is defined to 60 s SUMMARY 0025 Hence the present invention addresses the above mentioned problem to maintain an
20. des on top of it 1 e on top of the IP connectivity layer This is especially critical for any type of real time applications where the tolerable connection interruption time on the application layer is quite short However the applicability of the present invention as described hereinafter is not limited to real time applications Rather real time applications are merely referred to as an example for applications which fail in cases or require specialized code to cope with situations in which the address of a communication partner node changes Generally it is to be noted that the present inven tion is advantageously applicable to applications which fail in cases or require specialized code to cope with situations in which the address of a communication partner node changes Real time applications are only referred to as a descriptive example without limiting the scope of applica bility of the present invention 0018 Irrespective of the above examples focusing on peer to peer scenarios it has to be kept in mind that examples of client server scenario also exist The invention is also not limited to cases where tunnelling is used 0019 Generally the following example cases are appli cable where one of the nodes has a public address to which traffic from another node can be routed i e the node is addressable and reachable and the address changes during an ongoing transmission between the nodes 0020 The public address is assigne
21. disclosed an address management node Addr_Serv comprising 0057 a transceiver unit configured to return a current address assigned to a second node responsive to a request from a consulting unit of a first node 0058 the address management node further comprises a management unit configured to manage a current address of the second node by writing the current address into or fetching the address from a memory unit of the address management node 0059 Additionally there is disclosed an address assignor node 0060 configured to assign a current address to a second node the assigned address being associated with a life time attribute for the current address for caching address_to_ node_name mapping entries in other nodes than the address management node the lifetime attribute being set to zero or about 0 0061 Thus stated in other words if a first node A is facing a situation where it is about to abandon an application and or a connection to a second node B because e g a timeout limit is reached for the application or the connec tion i e the sent packets are not reaching node B anymore the invention proposes for example that node A makes a query to an address management node such as e g a DNS query on node B in order to check if the IP address of node B has changed before the application running on top of the connection or the connection is finally terminated If the first node A recognises that for example the
22. e basis of addresses assigned to the respective nodes and wherein the addresses are managed by the address manage ment node of the communication netvvork 100391 said detector unit comprises a receiving unit con figured to receive an error message informing the first node that a message addressed from the first node to the second node vvas not delivered 100401 said detector unit comprises a receiving unit con figured to experience a timeout vvhen vvaiting for a response or acknovvledgement from the second node 0041 the system further comprises an address assignor node configured to assign a current address to the second node the assigned address being associated with a life time attribute for the current address for caching address to node name mapping entries in other nodes than the address management node the lifetime attribute being set to zero or about 0 10042 the consulting unit comprises a monitoring unit configured to monitor a time interval responsive to the detection of the outage the monitoring unit being configured to realize that the time interval expires and vvherein the re establisher unit is configured to request the current address of the second node from the address management node responsive to realizing that the time interval has expired 100431 said re establisher unit is configured to try to re establish the connection to the second node by using an earlier known address of the second node until the time
23. e to be imple mented as software or by hardware without changing the idea of the present invention in terms of the functionality implemented 0008 method steps and or devices or parts of devices referred to as units likely to be implemented as hardware components at one of the server terminal entities are hard ware independent and can be implemented using any known or future developed hardware technology or any hybrids of these such as MOS Metal Oxide Semiconductor CMOS Complementary MOS BiCMOS Bipolar CMOS ECL Emitter Coupled Logic TTL Transistor Transistor Logic Jan 3 2008 etc using for example ASIC Application Specific Inte grated Circuit components or DSP Digital Signal Proces sor components as an example 0009 devices can be implemented as individual devices but this does not exclude that they are implemented in a distributed fashion throughout the system as long as the functionality of the device system is preserved 0010 Although the present description will be given on a general level as the invention is applicable to any com munication network it is pointed out that the invention is most suitable for IP based networks 0011 For example two nodes communicating with each other on an application level are having a so called peer to peer communication The application level is carried on a connection level A level as mentioned here corresponds to a layer in a layered communication model Howe
24. ent in the actual scenario concerned or S5 are taking place In any case the timing relation of message S6 and S8 in relation to steps S3 S4 S5 is of no importance in the present invention 0095 After detecting the connection outage of the com munication in step S8 the first node A will consult the address management node ADDR SERV of the communi cation netvvork NVV to verify the address assigned to the second node B if the connection to node B can t be re established in a defined period of time 0096 To this end the first node A starts a timer in step 59 after the connection outage in step S8 has been detected The timing value or time value is labeled as to indicate the time interval is related to the connection layer This time interval T_CONN has a length that is shorter than the time required for the application carried out in the application layer to indicate a failure and probably to terminate the application 0097 Generally a connection outage or failure can have various reasons For example the outage of the connection is based on a temporary interruption of the logical or physical channels of the connection Also the outage of the connection is for example based on a change of the logical or physical channels of the connection Such a change can occur if the connection changes from a first type of connec tion such as GPRS or WLAN GPRS General Packet Radio Service WLAN Wireless Local Area Network to a se
25. essage addressed from the first node to the second node was not delivered 0051 said detector unit comprises a receiving unit con figured to experience a timeout when waiting for a response or acknowledgement from the second node 0052 the consulting unit comprises a monitoring unit configured to monitor a time interval responsive to the detection of the outage the monitoring unit being configured to realize that the time interval expires and wherein the re establisher unit is configured to request a current address of the second node from the address management node responsive to realizing that the time interval has expired 0053 said re establisher unit is configured to try to re establish the connection to the second node by using an earlier known address of the second node B until the time interval expires 0054 the monitoring unit is configured to stop the timer unit and to end the process of re establishing the connection when the connection to the second node could be re established by using the earlier known address of the second node B ADDR B before the time interval expires 0055 data communicated between the first node and the second node via a connection comprises data relating to an application carried on a layer above a layer of the connec tion and wherein the time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 0056 Further there is
26. etting the e g TTL value first before remaining aspects features of the invention take place such as the address change the DNS entry update note no TTL value update the check of the other node vvhether the DNS entry has been updated etc which have already been or will in the following be described herein above or belovv 100931 Note this is just one way how the new address ADDR_B is assigned to the node B and how the address management node ADDR SERV is informed about the address change Another option not shown in FIG 2 could for example be that the ADDR_ASSIGNOR node assigns and informs the new address ADDR B directly to the second node B and the second node B takes care about the update of the address to node name entry in the look up table of the address management node ADDR SERV actual manner in vvhich the nevv address is informed to the address management node ADDR SERV and the node B is Of no importance for the present invention 100941 Tn step S8 the node A detects that the previously existing connection to node B is interrupted for example by receiving an error message from the netvvork as shovvn in step S6 or by experiencing a timeout when waiting for a response from node B in step S8 In the context of the present invention it is not important hovv the connection outage is detected Step S6 and S8 can be advanced in time and perhaps occur during the period of time in vvhich steps S3 or S4 if pres
27. gical or physical channels of the connection 21 The system according to claim 20 wherein the connection changes from one type of connection to another type of connection 22 A first node comprising a detector unit configured to detect an outage of an existing connection between the first node and a second node via a communication network a consulting unit configured to consult after detecting the outage of the connection an address management node of a communication network to verify the address assigned to the second node and a connection re establisher unit configured to re establish the connection based on a current address assigned to the second node 23 The first node according to claim 22 wherein said detector unit comprises a receiving unit configured to receive an error message informing the first node that a message addressed from the first node to the second node was not delivered 24 The first node according to claim 22 wherein said detector unit comprises a receiving unit configured to experience a timeout when waiting for a response or acknowledgement from the second node 25 The first node according to claim 22 wherein the consulting unit comprises a monitoring unit configured to monitor a time interval responsive to the detection of the outage the monitor ing unit being configured to realize that the time interval expires and wherein the re establisher unit is configured to request a current add
28. hat the timer expired node A realizes this and responsive thereto requests the current address of the second node B from the address management node ADDR_SERV in step S14 The address management node ADDR SERV in step 515 responsive thereto looks up the current address ADDR_B of node B in a memory unit thereof e g a look up table realized as a RAM random access memory or flash memory or the like and returns the current address assigned to the second node B ADDR_B to the first node A in step S15 The first node A then accepts the current address ADDR_B assigned to the second node B as returned from the address management node ADDR SERV and replaces the internal stored previ ous address of the node B ADDR_B with the new current address of node B ADDR_B Node A uses then the stored current address of node B ADDR_B for communicating with the second node B and re establishes in step S17 the connection to the second node B 0101 FIG 3 shows a block diagram of the first node A and FIG 4 shows a block diagram of the second node B referred to hereinabove For the sake of clarity it is pointed out that every node whether A or B can have the function ality and internal construction as shown with regard to node A and with regard to node B This means the functions performed depend on which node involved in the commu nication perceives first the connection failure or is assigned a new address first However for the sake of
29. he connection re establisher unit A5 0106 The connection re establisher unit comprises an acceptor unit A6 This acceptor unit A6 is configured to accept the current address assigned to the second node B as returned from the address management node ADDR SERV i e the newly assigned address ADDR_B as it is for use by the first node A for communicating vvith the second node B via the connection The re establisher unit A5 is configured to re establish the connection to the second node B based on that accepted returned new current address ADDR_B assigned to the second node The functionality realized by these units corresponds to steps S16 S17 shown in FIG 2 Note that the node A may have obtained the knovvledge of the previous address ADDR in a similar way as obtaining the knowledge of the current address ADDR_B 101071 FIG 4 shovvs a block diagram of a second node B and aspects involved therevvith according to the present invention Note again that the functionalities units of the first and the second node can simultaneously be present in one of the nodes but that these aspects functionalities are described merely distinctly to keep the description and explanation simple to understand 101081 Asin FIG 3 the node B shown in FIG 4 comprises a transceiver unit B1 configured to receive and send mes sages requests and or data from and to the network and other nodes 0109 According to the scenario illustrated in FIG 2 the n
30. he existing connection between the nodes A B a consulting unit A3 at said first node A configured to consult after detecting the outage of the connection the address management node Addr_Serv of the communication network to verify the address assigned to the second node B a transceiver unit AS1 at said address management node Addr_Serv configured to return a current address assigned to the second node B responsive to a request from the consulting unit to the first node and a connection re establisher unit A5 at said first node A configured to re establish the connection based on the cur rent address assigned to the second node B to from NW nodes trans ceiver Al request addr receive addr Addr_B re established acceptor b Jan 3 2008 Sheet 1 of 5 US 2008 0002686 A1 Patent Application Publication big MN W JS S 4aAe uono uuoo s ublu uoneoiidde UONEO UNWLUOD uul e 1 4 1ppv 8 V PPV V Joubissy 1ppy AJ9S Jppy Jan 3 2008 Sheet 2 of 5 US 2008 0002686 A1 Patent Application Publication 2 8 Jppy uono uuoo ysiiqeyse a1 1S se g jo ssauppe QLS Meu 149206 ssoalppe 4 GLS juawno dn yoo di JO 55 juaund ysonbas YLS 8919
31. id it is to be noted that it is of a subordinated aspect of the present invention which entity of a network sets the TTL value as long as it has been set In certain scenarios and when referring to a DNS scenario to which the invention is applicable the owner of the DNS entry i e the person or organization who own e g the name host somedomain com is given credentials to a management interface of the DNS so that they can create and or maintain the DNS entry Typical scenarios today are owner uses the web based management interface provided by the DNS and sets the value manually or owner has some management software that programmatically interfaces with the DNS and sets the value 0091 Incase of Dynamic DNS the owner often places a DynDNS client in the computer whose DNS entry is being updated and it updates the DNS entry when the IP address US 2008 0002686 A1 changes The DynDNS client is in essence an example of the management software that programmatically interfaces with the DNS except the DynDNS client does not touch the TTL In principle it could designed to do that too but there is no need since the TTL value is assumed constant 10092 For the purpose of the present invention it can thus be assumed that the lifetime attribute such as the TTL value as present also in regard to the addresses managed in the address management node has been set by some mechanism or entity Thus there is a one time operation of s
32. ion re establisher unit A5 at said first node A configured to re establish the connection based on the current address assigned to the second node B 0120 Various modifications to the present invention as outlined herein above are possible without departing from the spirit and scope of the present invention as defined in the appended claims US 2008 0002686 A1 1 A method of maintaining a connection between a first node and a second node comprising detecting by the first node an outage of an existing connection between the first and second nodes consulting by said first node after detecting the outage of the connection an address management node of a communication netvvork to verify an address assigned to the second node returning from said address management node a current address assigned to the second node and re establishing the existing connection by said first node based on the current address assigned to the second node vvherein data is communicated betvveen the first and second nodes on the basis of addresses assigned to the respective nodes and wherein the addresses are man aged by the address management node of the commu nication netvvork 2 The method according to claim 1 vvherein said detect ing comprises receiving an error message that the connec tion to the second node is interrupted 3 The method according to claim 1 vvherein said detect ing comprises experiencing a timeout when waiting for a
33. is is illustrated by the bidirectional arrow labeled S1 At a certain point of time during the ongoing e g real time communication the con nection at the lower layer fails or experiences an outage as illustrated in by the interrupted arrow labeled S2 in FIG 2 Causes for such an outage could be for example 0082 a connection interruption on the lower layer 0083 a change from one connection type to another connection type 0084 handover of the connection e g to another base station 0085 node address change e g due to DHCP lease time expiry 0086 In one example scenario as illustrated and assumed in FIG 2 such outage may be caused e g due to disruption in coverage of the network such as loosing data connection coverage in a GPRS or 3G network environment In such scenario Node B perceives such connection outage or failure in step S3 Responsive to this perception the second node B automatically requests re establishing the lower layer connection to the network NW in step S4 According to one particular aspect of such automatically requesting re establishing the connection such request is forwarded within the network NW to the address assignor node ADDR_ASSIGNOR In an example implementation the address assignor may be realized as a DHCP server IP tunneling server providing an IP address for the other end point of the tunnel or similar entity In a step S5 the address assignor node of the communication netw
34. n FIG 1 an existing connection is established and ongoing between the first node A and the second node B In the illustrated case it is assumed that as an example a real time communication application is established via this connection The illustrated real time communication com prises at least two layers These are the connection layer as the lower layer and an application layer as a higher layer The connection layer serves to transport the data on the physical logical channels and the application layer is a higher layer application in relation to which payload use data are communicated 0078 The present invention is not limited to a particular communication network or network system The nodes can be wired nodes or wireless nodes The communication is for example packet based and can be based on the Internet protocol IP It is not important which protocol version is concerned IPv4 or IPv6 or any other In case of an IP based network messages communicated between the nodes are IP packets and the address management node is a name server such as a DNS Domain Name Service server while the address assignor is e g a DHCP server In case of a US 2008 0002686 A1 communication network based on IPv6 the messages com municated are also IP packets based on that protocol version and the address management server is a dynamic DNS server Still further it is possible that the present invention is applied in a scenario or architecture in
35. nd ADDR_B Data communicated between the nodes A B are communicated on the basis of these addresses assigned to the respective nodes Addresses are assigned to the respec tive nodes by an address assignor node Addr Assignor Indicated by arrows is the functionality that the nodes A B to which addresses are assigned are informed about the assigned addresses Also the address assignor node may inform a further node within the network of the new address to node name assignment address management node ADDR_SERV of the communication network which is also shown in FIG 1 and which manages the address to node name assignments so that these can be looked up Note that there may exist also other ways how to inform the address management node about new address to node name assignments e g the address management node is informed by the node itself which receives the new address The address management node ADDR_SERV has thus knowledge of the addresses assigned to the nodes in the networks receives requests for node address information for requested node names and returns the information concern ing assigned addresses as illustrated by the double arrows at the address management node ADDR_SERV Associated to or part of the address management node is a memory in which the addresses to node names mapping is maintained FIG 1 shows that node A is assigned address ADDR_A and node B is assigned the address ADDR_B Furthermore as shown i
36. ned by the address assignor to the node B without a preceding request of the node itself For example in case the lifetime of the address expires a new address is assigned to the node B by the address assignor The new address is then informed to the node B e g from the address assignor directly via the transceiver unit B1 e g at the auto connection re establisher unit B3 or another inter nal unit of the node B Likewise if the new address is informed directly to the node B and the address management node ADDR SERV is not yet aware of the new address to name mapping for the node B the node B may instruct an US 2008 0002686 A1 update of the address to node name mapping at the address management node ADDR_SERV This may also be accom plished by the unit B3 of the node B in cooperation with the transceiver unit B1 101111 FIG 5 shows a block circuit diagram of the address management node ADDR_SERV As mentioned before in case of an Internet protocol based communication network such an address management node may be implemented as a Domain Name Service server DNS server 10112 As shown in FIG 5 the address management node ADDR_SERV comprises a transceiver unit AS1 configured to exchange data messages with other network entities and or nodes such as nodes A B and the address assignor server described above mainly in relation to FIG 2 In particular the transceiver unit AS1 forwards internally to the address management node a
37. ode B comprises a perception unit B2 which is configured to perceive an outage of the connection between the node B and another node The another node can be a terminal or a server To this end the perception unit B2 is in cooperation with the transceiver unit B1 in order to acquire the necessary information concerning the connection Once the perception unit B2 perceives an outage of the connection the percep tion unit B2 instructs an auto connection re establisher unit B3 to automatically request re establishing of the connec tion To this end the auto connection re establisher unit B3 requests a new address to be assigned to the node from the address assignor node ADDR_ASSIGNOR via the trans ceiver unit B1 Also via the transceiver unit B1 the auto connection re establisher unit B3 receives the requested new address from either the address assignor node directly or via the intermediate of e g the address management node as explained above in connection with the signaling in FIG 2 Other signaling paths are also optionally possible as long as the node B is informed from the network and or its entities of the newly assigned current address Upon receipt thereof the auto connection re establisher unit B3 then uses this new current address ADDR_B to re establish the connection via the transceiver unit B1 0110 Alternatively according to the option described in connection with FIG 2 but not shown in FIG 2 a new address may be assig
38. ongoing communication connection with another node whose address changes with minimal loss of performance and with minimal disturbance for an application carried on top of such a connection Jan 3 2008 0026 According to aspects of the present invention this object is for example achieved by a method system and nodes as defined in the respective independent claims Advantageous further developments of those aspects of the present invention are for example defined in respective dependent claims 0027 In detail according to particular aspects of the present invention and respective sub aspects thereof there is disclosed a method of maintaining a connection between a first node and a second node comprising detecting by the first node an outage of an existing connection between the first and second nodes consulting by said first node after detecting the outage of the connection an address manage ment node of a communication network to verify an address assigned to the second node returning from said address management node a current address assigned to the second node and re establishing the existing connection by said first node based on the current address assigned to the second node wherein data is communicated between the first and second nodes on the basis of addresses assigned to the respective nodes and wherein the addresses are managed by the address management node of the communication network 0028 said dete
39. onnection and a time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 9 The method according to claim 1 wherein the outage of the connection is based on a change of logical or physical channels of the connection 10 The method according to claim 9 wherein the connection changes from one type of connection to another type of connection Jan 3 2008 11 Acomputer program product embodied on a computer readable medium configured to control a processor to perform a method comprising detecting by the first node an outage of an existing connection between the first and second nodes consulting by said first node after detecting the outage of the connection an address management node of a communication network to verify an address assigned to the second node returning from said address management node a current address assigned to the second node and re establishing the existing connection by said first node based on the current address assigned to the second node 12 A system configured to maintain an existing connec tion between a first node and a second node comprising a detector unit at the first node configured to detect an outage of an existing connection between the first and second nodes a consulting unit at said first node configured to consult after detecting the outage of the connection an address management node of a
40. onnection establisher unit connection re estab lisher unit AS to try to re establish the connection based on a previous address in the example ADDR_B of the second node B According to the above option if this is not successful the connection re establisher unit A5 returns the corresponding result to the consulting unit which in turn instructs the connection re establisher unit A5 again to try to re establish the connection via the transceiver unit A1 This exchange of data between the consulting unit A3 and the connection re establisher unit AS is expressed in FIG 3 by the two arrows indicating this signaling between these nodes and in FIG 2 by the loop between steps 510 and S13 In case the connection could not be re established during or upon lapse of the time interval the consulting unit A3 instructs the connection re establisher unit A5 to request the current address of the second node B from the address management node ADDR_SERV 0104 Alternatively the consulting unit may simply await timer expiry before instructing the connection re establisher unit to re establish the connection based on the previous address of the second node 0105 The request for the current address of the second node B is forwarded from the re establisher unit A5 via the transceiver unit to the address management node Simi larly the new address ADDR_B is received at the trans Jan 3 2008 ceiver unit Al of the node and forwarded internally to t
41. ork assigns a new lower layer address ADDR_B to the second node B 0087 Note that dependent on the implementation assign ing of a new address may not necessarily be request based Jan 3 2008 but could also be accomplished automatically once the address assignor node is informed by a mechanism different from a request of the node B In this regard as an alternative example not shown in FIG 2 transparently for the node B a certain mechanism accomplishes assignment of a new address to node B Step S5 is thus performed at the address assignor based on a trigger event differing from the request in step S4 from node B 0088 Just as an example for such an trigger event the lifetime of an address assigned to node B may expire for example the DHCP lease time and a new address is thus necessary to be assigned to node B Steps S3 and S4 shown in FIG 2 then do not occur Further in such scenario the connection outage experienced in step S2 would occur rather as a result of that address change since data transmitted from node A to node B based on the old address of node B can no longer be delivered to node B with the new address being assigned thereto Thus step S5 takes place prior to step S2 in such a modified scenario 0089 To clarify the previously ongoing e g real time communication with node B was based on node B s address ADDR_B In step S5 the current new address ADDR_B is assigned to node B Furthermore optionally
42. ould reside in the same network node 0064 The invention relates under a particular aspect to tackling the problem of maintaining IP connectivity with another node whose IP address changes due to break up in IP connectivity Nevertheless the present invention is not limited to specific types of networks and could be used always when the address e g IP address of one party during an ongoing call changes and the IP connectivity shall be maintained Note changing of IP addresses might happen for example due to a temporary connection inter ruption outage when changing the connection from e g GPRS to WLAN if WLAN becomes available or when the lease time for an IP address expires and the node gets a new IP address assigned by e g a DHCP server 0065 Accordingly with the present invention at least the following advantages can be achieved whether individually or in combination 0066 According to an aspect of the present invention a method comparable with DynDNS is suggested which is improved with respect to the performance response time 0067 Moreover the present invention provides IP mobil ity support for e g real time applications Applications are kept alive if the local and or remote node IP address changes even if also a tunneling server IP address changes 0068 The method mechanism and nodes of the system as described under aspects of this invention can be applied in any network where mobility shall be su
43. pported 0069 The invention improves usability of e g a tunnel ing network scenario as connections are automatically re established instead of manual re establishment BRIEF DESCRIPTION OF THE DRAWINGS 0070 The aspects of the present invention will hereinaf ter be described with reference to the drawings in which 0071 FIG 1 shows an overview of the system according to the present invention 0072 FIG 2 shows a signaling diagram of aspects involved in the present invention 0073 FIG 3 shows a block diagram of a node node A according to the present invention 0074 FIG 4 shows a block diagram of a node node B according to the present invention and Jan 3 2008 0075 FIG 5 shows a block diagram of an address management node ADDR_SERV according to the present invention DESCRIPTION OF ASPECTS OF THE PRESENT INVENTION 0076 The aspects of the present invention will now be described with reference to the accompanying Figures in more detail The present invention is applicable to all above described example scenarios even though the following description may focus on only one of these examples or only on a common aspect thereof 0077 FIG 1 shows an overview of the system according to an aspect of the present invention As shown in FIG 1 the system comprises a part of a network NW The network comprises a first node A and a second node B The nodes A B are identified by respective addresses ADDR_A a
44. ress of the second node from the address management node responsive to realizing that the time interval has expired 26 The first node according to claim 25 wherein said re establisher unit is configured to try to re establish the connection to the second node by using an earlier known address of the second node B until the time interval expires Jan 3 2008 27 The first node according to claim 26 wherein the monitoring unit is configured to stop the timer unit and to end the process of re establishing the connection when the connection to the second node could be re established by using the earlier known address of the second node B ADDR B before the time interval expires 28 The first node according to claim 25 wherein data communicated between the first node and the second node via a connection comprises data relating to an application carried on a layer above a layer of the connection and wherein the time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 29 An address management node comprising a transceiver unit configured to return a current address assigned to a second node responsive to a request from a consulting unit of a first node 30 The address management node according to claim 29 further comprising a management unit configured to manage a current address of the second node by writing the current address into or fetching the
45. t 0 16 The system according to claim 12 wherein the con sulting unit comprises a monitoring unit configured to monitor a time interval responsive to the detection of the outage the monitor ing unit being configured to realize that the time interval expires and wherein the re establisher unit is configured to request the current address of the second node from the address management node responsive to realizing that the time interval has expired 17 The system according to claim 16 wherein said re establisher unit is configured to US 2008 0002686 A1 10 try to re establish the connection to the second node by using an earlier known address of the second node until the time interval expires 18 The system according to claim 17 wherein the monitoring unit is configured to stop the timer unit and to end the process of re establishing the connection when the connection to the second node could be re established by using the earlier known address of the second node before the time interval expires 19 The system according to claim 16 wherein data communicated between the nodes via the connection are data relating to an application carried on a layer above a layer of the connection and the time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 20 The system according to claim 12 wherein the outage of the connection is based on a change of the lo
46. time interval monitored has a length that is shorter than a time required for the application to indicate a failure or terminate 0035 the outage of the connection is based on a change of logical or physical channels of the connection 0036 the connection changes from one type of connec tion to another type of connection 0037 Also there is disclosed a computer program prod uct comprising computer implementable instructions for carrying out the method according to any of the above aspects and sub aspects when executed on a processor 0038 Further there is disclosed a system configured to maintain an existing connection between a first node and a second node comprising a detector unit at the first node configured to detect an outage of an existing connection US 2008 0002686 A1 between the first and second nodes a consulting unit at said first node configured to consult after detecting the outage of the connection an address management node of a commu nication network to verify an address assigned to the second node a transceiver unit at said address management node configured to return a current address assigned to the second node responsive to a request from the consulting unit to the first node and a connection re establisher unit at said first node configured to re establish the connection based on a current address assigned to the second node vvherein data is communicated betvveen the first and second nodes on th
47. unication networks Therefore refer ence has been made to specific names of nodes in such networks only by way of example Depending on the com munication network to which the present invention is applied the actual names of the nodes may differ from the examples used herein 0115 As mentioned before the present invention is also applicable between e g a node A and a server B The connection between these can also be a tunnelling connec tion 0116 For example when the node A client connects to the server B it negotiates and establishes e g an IPv6 over an IPv4 tunnel with the tunnelling server The IPv4 lower layer connection may experience an outage e g because of mobile phone node handover with resulting IPv4 address change The node may also change intentionally the IPv4 connectivity e g from GPRS to WLAN if WLAN becomes available which might result also in an IPv4 address change If the underlying IPv4 connectivity breaks it breaks as well the IPv6 tunnel and possible peer to peer connections that have been established between this node and other nodes 0117 This invention makes it possible to re establish the peer to peer node to node connections automatically after an outage in IPv4 connectivity before the application util ising the IPv4 tunnel breaks A outage in IPv4 connectivity means here such loss and re establishment of IPv4 connec tivity that results in a change of the IPv4 address allocated to the node
48. ver the present invention is not limited to a specific OSI layer or layers OSI Open System Interconnection 0012 Nevertheless a communication between two nodes as described in examples of scenarios to which the present invention is applicable is not limited to a peer to peer communication Rather IETF Internet Engineering Task Force defines a client as a host node that initiates e g IP communication by sending the first packet to another node and a server as a host that when idle waits and listens to incoming packets from a client In such a framework two peers are nothing but two hosts that can assume the role of either a client or a server or both Other definitions of peer to peer exist too in abundance Nonetheless the invention is also applicable to a variety of client server scenarios Its applicability to peer to peer scenarios is a by product of its applicability to client server scenarios under the above given definition of peer to peer 0013 For example a peer to peer communication appli cation between two nodes A and B may reside in a scenario as follows A node client negotiates and establishes an IPv6 tunnel over an IPv4 connection to a tunnelling server The tunnelling server and the intermediate IPv6 network then route IPv6 traffic to and from another node The IPv4 connection may break or be subject to an outage uninten tionally e g because of a node e g a mobile phone will move from one BTS area
49. volving tunneling In such a scenario the connection layer can be an IPv4 layer and the application layer can for example be a tunneled application based on IPv6 0079 FIG 2 shows a signaling diagram of signaling and processing performed in an example scenario at respective nodes In the horizontal direction the nodes involved are illustrated whereas the vertical sequence of processing steps signaling messages reflects the sequence in time in a rough outline 0080 As shown in FIG 2 the system constituents already described above with reference to FIG 1 are involved Other nodes and or network entities are not shown merely for the reasons of keeping the explanation and drawings simple and easy to understand It is however not excluded that depending on the actual network concerned to which the present invention may be applied corresponding further network entities are involved in the background without influencing the aspects of the present invention described herein in order to contribute to the in other aspects normal behavior functioning of the network 0081 As shown in the example scenario of FIG 2 node A has an ongoing for example real time communication with node B Node A is assigned address ADDR_A and node B is assigned address ADDR_B The real time communica tion in the example scenario relies e g on a peer to peer application layer higher layer on top of a connection layer lower layer as shown in FIG 1 Th
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