Communication apparatus, IP address acquisition method and
Contents
1. reply for IP address request back to the AP 12 and an IP address for example 172 16 40 10 is allocated to the AP 12 by the DHCP server 18 On the other hand when the DHCP server 18 cancels out an IP address that has been allocated to a DHCP client the DHCP server 18 sends a message DHCP RELEASE to invalidate the IP address allocated In the above manner since the AP 12 has a connection with the network 16 the above mentioned some settings regarding the AP 12 can be manipulated from another PC via the network 16 A description will now be given of a correspondence between the PC 14 and the STA 10 being in the STA mode Suppose that the PC 14 has such a setting that the PC 14 acquires an IP address by using DHCP Further suppose that an IP address for example 192 168 1 1 is allocated to the SAT 10 as a default and that the SAT 10 uses the IP address until the SAT 10 knows an IP address of the AP 12 by estab lishing a connection with the AP 12 Currently the STA 10 and the AP 12 are assumed to have no connection each other In the above situation at step 5 the PC 14 sends a mes sage DHCP DISCOVER to the STA 10 At step 6 the STA 10 sends a message DHCP OFFER back to the PC 14 At step 7 the PC 14 sends a message DHCP REQUEST IP address request to the STA 10 At step 8 the STA 10 sends a message DHCP ACK reply for IV address request back to the PC 14 and a temporary IP address for examp2. to the PC 14 so as to invalidate the temporary IP address that has been allocated to the PC 14 At step 16 the PC 14 sends the message DHCP DISCOVER again so as to acquire an IP address This message DHCP DISCOVER is sent to the DHCP server 18 via the network 16 because the STA 10 and the AP 12 have the connection currently According to the above mentioned procedure that the AP 12 acquires the IP address from the DHCP server 18 at step 17 the DHCP server 18 sends the message DHCP OFFER back to the PC 14 At step 18 the PC 14 sends the message DHCP REQUEST IP address request to the DHCP server 18 At step 19 the DHCP server 18 sends the message DHCP ACK reply for IP address request back to the PC 14 whereby the PC 14 acquires an IP address A description will now be given with reference to flow charts in FIGS 5 and 6 of the above process between the STA 10 and the AP 12 FIG 5 shows a flowchart illustrating a process regarding the STA mode which corresponds to the process of the STA 10 in this case On the other hand FIG 6 shows a flowchart illustrating a process regarding the AP mode which corresponds to the process of the AP 12 in this case A description will be given of a flowchart illustrating a process regarding the STA mode in FIG 5 At step S101 it is determined whether or not a communication apparatus is in the STA mode If the communication apparatus is not in the STA mode th
3. 1 1 i Io default j i 13 DHCP OFFER i 1 i O A O O a 1 14DHCP REQUEST 1P 172 16 40 11 CI9DHCP ACK i B probe Request 8 Authentication Lo Authantication i i 2 Probe Response j i T Li i i i 10 Assoc Request j an i t Assoc Response i l pziz21840 0 12 DHCP DISCOVER tt 4i IP XXXX DDHCP DISCOVER ee eee 2 DHCP OFFER 3 DHCP REQUEST TG DHCI 172 18 40 10 POHOP ACK SETTINGS OF AP i IP i to ux a ECL i i U S Patent Apr 6 2010 Sheet 1 of 8 US 7 694 017 B2 FIG 1 PRIOR ART FIG 2 NETWORK US 7 694 017 B2 Sheet 2 of 8 Apr 6 2010 U S Patent 66 AHOWA3WN d34J3n amp 8 I3NVY3 OIN 39u49u33 OHJNOO YO fido US 7 694 017 B2 Sheet 3 of 8 Apr 6 2010 maman Lay s Pr O U S Patent Xov dOHd d61 1S3n63u dOHQ 8I Ya440 dOHQ LI our ramma a a A ee A dV 40 SONLLL3S MOV donat 1 i i1S3n63M doHQ 43440 doHa z y3A09SIO dona OL Or 91 22 l dl XXX X dl esuodsay Issy rh E _ ysanbay sossy uoneonuayyny 1 esuodssy s3044 01 ysanboy sqq V Old OL OP S 2Ll el opor aL ZLI dl 1189126 l dl Y
4. address as its own address instead of the default address In such a manner after establishing the connection between the STA 10 and the AP 12 the STA 10 sends a message DHCP DISCOVER that the STA 10 has already received from the PC 14 and the message DHCP DISCOVER is sent to the DHCP server 18 via the network 16 According to the above mentioned procedure that the AP 12 acquires the IP address from the DHCP server 18 at step 13 the DHCP server 18 sends the message DHCP OFFER to the PC 14 At step 14 the PC 14 sends the message DHCP REQUEST IP address request to the DHCP server 18 At step 15 the DHCP server 18 sends the message DHCP ACK reply for IP address request back to the PC 14 whereby the PC 14 acquires an IP address A description will now be given with reference to FIG 8 of a roaming of the PC 14 possessing an IP address through the above process The roaming in this description means that as shown in FIG 8 the PC 14 and the STA 10 move and in turn connect with an AP 32 different from the AP 12 with which the PC 14 and the STA 10 have maintained a connec tion heretofore In this case the STA 10 needs to discard an IP address that the STA 10 has used and acquire a new IP address In addition if the AP 32 has a network address different from the AP 12 the PC 14 also needs to acquire a new address In the following a description will be given with reference to a flowchart of FIG 9
5. allocates an IP address in a case that it is impossible that a first communication apparatus is connected with a second communication apparatus when the first communica tion apparatus receives an IP address request message from a terminal FIG 5 is a flowchart illustrating a process in an STA mode FIG 6 is a flowchart illustrating a process in an AP mode FIG 7 is a sequence diagram illustrating how a DHCP server allocates an IP address in a case that it is possible that a first communication apparatus is connected with a second communication apparatus when the first communication apparatus receives an IP address request message from a terminal US 7 694 017 B2 5 FIG 8 is a diagram illustrating a configuration wherein a roaming is conducted and FIG 9 is a flowchart illustrating a roaming process DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following embodiments of the present invention will be described with reference to the accompanying drawings FIG 2 shows an entire configuration according to the embodiment of the present invention In FIG 2 there are illustrated communication apparatuses 10 and 12 a PC 14 connected with the communication apparatus 10 a network 16 connected with the communication apparatus 12 and a DHCP server 18 connected with the network 16 The com munication apparatus 10 is connected with the PC 14 ina cable such as a 10Base T and the communication apparatus 12 is also connected
6. do not authenticate each other Ifthe STA 10 does not receive the message DeAuthentication the STA returns to step S306 If the STA 10 receives the message DeAuthentication the STA 10 sends a message Authentication for requesting the authentication to the AP 32 at step S308 and is waiting for a message Authentication meaning an acceptance of the authentication When receiving the message Authentica tion at step S309 the STA 10 sends a message ReAssocia tion Requests reconnect request to the AP 32 at step S310 and is waiting for a message ReAssociation Response re connect reply Then the STA 10 receives the message ReAssociation Response at step S311 The message ReAssociation Response includes a new IP address that the AP 32 allocates to the STA 10 When the IP address is set to the STA 10 the roaming process for the STA 10 is completed As mentioned above if the AP 32 has a network address different from the AP 12 the PC 14 also needs to acquire a new address Accordingly the STA 10 sends the message DHCP RELEASE shown in FIG 4 to the PC 14 in order to let the PC 14 discard an IP address that the PC 14 currently maintains The PC 14 sends the message DHCP DISCOVER to the DHCP server 18 in order to acquire a new IF address The message DHCP DISCOVER is sent to the DHCP server 18 via the STA 10 and the AP 32 because the STA 10 and the AP 32 have already established a connecti
7. of a roaming method including a way in which these two addresses are allocated FIG 9 shows the flowchart illustrating a roaming process At step 301 the STA 10 performs a normal operation such as a transit operation At step S302 it is determined whether or not the AP 12 disappears If not the process returns to step 301 and the STA 10 performs the normal operation Ifthe AP 12 disappears the STA 10 sends a message Probe Request at step S303 and is looking for another AP Regarding the disappearing determination when the STA 10 cannot receive a beacon propagated by the AP 12 it is supposed that the AP 12 disappears After sending the message Probe Request the STA 10 is waiting for receiving a message Probe Response At step S304 if the STA 10 cannot receive the message Probe Response the STA 10 sends the message 20 25 30 35 40 45 50 55 60 65 10 Probe Request again Ifthe STA 10 can receive the message Probe Response the STA 10 sends a message ReAssocia tion Request reconnect request at step S305 At step S306 if the STA 10 receives a message ReAssociation Response the STA 10 returns to step S301 If not it is determined whether or not the STA 10 receives a message DeAuthenti cation The message DeAuthentication means an authen tication denial which is sent in a case that the STA 10 and the AP 32 which is expected to be a substitute for the AP 12
8. sary to acquire and set an IP address for a terminal There are two methods to set the IP address for the terminal One is a method in which the IP address is manually set The other is a method in which the IP address is set by using DHCP Dynamic Host Configuration Protocol When the IP address is manually set a network administrator needs to manage IP addresses for terminals therein so that an identical IP address cannot be simultaneously allocated to a plurality ofterminals Tn contrast under the DHCP an IP address is dynamically and automatically allocated to a terminal In the DHCP when a terminal gains access to a DHCP server an IP address is allocated for the terminal The DHCP is currently used in a large number of networks On the other hand a wireless LAN has been widespread recently As shown in FIG 1 in a wireless LAN information is communicated by wireless between a station 10 connected with a PC 14 and an access point 12 connected with the LAN In FIG 1 the station is connected with the PC 14 by a fixed line and the access point 12 is connected with a network by a fixed line Also a DHCP server 18 is connected with the network In such a wireless LAN IP addresses have to be allocated to not only the PC 14 but also the station 10 and the access point 12 that are serving to implement wireless communica tion A description will be given of a procedure to set an IP address for the PC 14 by using the DHCP server 18 under
9. this configuration At the beginning there are prepared the same number of IP addresses as the number of access points In this configuration just one IP address should be prepared because there is only one access point 12 Next a temporary IP address is manually set to the PC 14 As the temporary IP address there is provided an IP address whose network address to be mentioned later is identical to that of the prepared address After receiving the temporary IP address the PC 14 is engaged to set the prepared IP address to the station 10 and the access point 12 Since this configuration has just the access point 12 therein the station 10 and the access point 12 may have an identical IP address Thus the identical IP address is allocated to the station 10 and the access point 12 The station 10 and the access point 12 to which the iden tical IP address is allocated are connected with the PC 14 and a network 16 respectively In this manner the PC 14 gains a connection with the network 16 via the station 10 and the access point 12 After that an IP address setting ofthe PC 14 is modified into a setting such that the PC 14 acquires an IP address through DHCP and then the PC 14 is rebooted to apply the modification In the above mentioned procedure the PC 14 can acquire an IP address from the DHCP server 18 via the station 10 and the access point 12 20 25 30 35 40 45 50 55 60 65 2 As mentioned above even
10. when the DHCP is used to set an IP address automatically in a wireless LAN it is necessary to perform complicated tasks for setting some apparatuses to implement a wireless LAN and further reboot a PC to apply a new setting SUMMARY OF THE INVENTION It is a general object of the present invention to provide a communication apparatus an IP address acquisition method and a roaming method in which the above mentioned prob lems are eliminated A more specific object ofthe present invention is to provide a communication apparatus an IP address acquisition method and a roaming method in which a terminal can auto matically acquire an IP address from an addressing server in a wireless network necessary for the IP address In order to achieve the above mentioned objects there is provided according to one aspect of the present invention an IP address acquisition method for acquiring an IP address for a terminal from a dynamic addressing server in a communi cation system having a first communication apparatus con nected with the terminal and a second communication appa ratus connected with the dynamic addressing server wherein the first communication apparatus communicates via the sec ond communication apparatus connected by wireless with the first communication apparatus the method comprising the steps of providing a temporary IP address to the terminal in a case where it is impossible to connect the first communica tion apparatus to the s
11. with the network 16 in a cable such as a 10Base T A description will now be given of the communication apparatuses 10 and 12 The communication apparatuses 10 and 12 are formed of a similar type of communication appa ratus and can switch into a plurality of modes to be men tioned later FIG 3 shows a block diagram illustrating hard ware of the communication apparatuses 10 and 12 The communication apparatuses 10 and 12 shown in FIG 3 com prise a CPU for control 20 a frame buffer memory 22 an Ethernet MAC Controller 24 for connecting to a network a MAC part 26 in a MAC layer serving for a media access control in a MAC sub layer a PHY part 28 for serving as an interface with a physical layer and an antenna 30 In this configuration data from the Ethernet MAC Controller 24 is temporally stored in the frame buffer memory 22 Then the MAC part 26 performs a media access control in accordance with the CSMA CA method IEEE802 11 for the data and the data is formed as a frame in accordance with the IEEES02 11 and is delivered in the PHY part 28 which is eventually propagated through the antenna 30 On the other hand data from the antenna 30 is lifted in the PHY part 28 from the physical layer to the MAC sub layer and the MAC part 26 performs a media access control for the data Then the data is temporally stored in the frame buffer memory 22 and is sent through the Ethernet MAC Controller 24 The CPU for control 20 is responsible to co
12. 2 Sashihara etal 455 11 1 OTHER PUBLICATIONS Linksys Wireless USB Network Adapter Linksys 2001 Linksys Wireless Network Access Point Linksys 2001 Archive org Instant Wireless Jun 2001 Wavitl 1 User manual Dec 2001 Mitsumi cited by examiner Primary Examiner Thu Nguyen Assistant Examiner Julian Chang 74 Attorney Agent or Firm Ladas amp Parry LLP 57 ABSTRACT In a wireless network in which an addressing server allocates an IP address there are provided an IP address acquisition method a communication apparatus and a roaming method whereby a terminal can automatically acquire an IP address from the addressing server An IP address acquisition method for acquiring an IP address for a terminal 14 from a address ing server 18 comprises the steps of providing the terminal 14 with a temporary IP address in a case that a first commu nication apparatus 10 is not capable of connecting with a second communication apparatus 12 when the first commu nication apparatus 10 receives an IP address request message from the terminal 14 discarding the temporary IP address from the terminal 14 when it becomes possible to connect with the second communication apparatus 12 and a commu nication path is established and acquiring an IP address for the terminal 14 from the addressing server 18 via the com munication path 1 Claim 8 Drawing Sheets IP XXXX 5 DHCP DISCOVER i P 192 168
13. 3AODSIA dOHQ 91 j S A 39Y3138 dOHAG YLS JO SONILLAS WOW doHO k l LSINOJY dOoHQ E A B3330 dOHQ 9 _ u3A09SId dOHQ S 11 0y 91 32 l dl XXX X dI 18916 l dl XXX X dl LN3MO doHQ Od U S Patent Apr 6 2010 Sheet 4 of 8 US 7 694 017 B2 FIG 5 START 101 S STATION NO S112 MODE 102 SEND YES Probe Request Sida MODE s113 RJ45 CABLE CONNECTED RECEIVE Probe Response 2 ES S104 YES NO S114 IP ADDRESS S105 SETTING SEND Authentication S100 TUNES ADDRESS MANUAL 115 SEND DHCP SETTING OPERATION AVE S107 NORMAL OPERATION YES S116 S108 SEND Association RECEIVE Request DHCP DISCOVER 109 YES E SEND DHCP OFFER s110 YES s118 RECEIVE DHCP REQUEST SEND DHCP RELEASE 5j ves 5119 SEND DHCP ACK NORMAL OPERATION U S Patent Apr 6 2010 Sheet 5 of 8 US 7 694 017 B2 FIG 6 201 YES TO STA MODE IP ADDRESS SETTING YES 205 206 ADDRESS MANUAL SETTING SEND DHCP DISCOVER OPERATION YES 207 RECEIVE DHCP OFFER YES S208 SEND DHCP REQUEST 208 RECEIVE DHCP ACK i YES 210 NORMAL OPERATION US 7 694 017 B2 Sheet 6 of 8 Apr 6 2010 U S Patent dV 30 SONLLLAS T MOV dOHa Li A1Sano3s dOHC E u34JO0 dOHA 2 l ua o9sia douati u3A09SIQ dOHACL Ol or StL d i M3AOOSIQ d
14. OHA Z 1 j OL OP BEZLI al suodsay 005Sy qu ysenbay Sossy Q 1 voneonueyany 6 i uoneonuauiny go COIs 4nejap 1 1 891 261 d 01 j ADV dOHG S LSANOSY dOHACr 1 H3440 dOHA E A A YIAOISIO doHQ S e LN3NO dOHQ 9d y Log OL Lt dl XXX X dl U S Patent Apr 6 2010 Sheet 7 of 8 US 7 694 017 B2 STA 10 PC 14 MOVE ROAMING FIG 8 M0 4 y enam U S Patent Apr 6 2010 Sheet 8 of 8 FIG 9 NORMAL OPERATION YES AP 302 DISAPPEAR YES S303 SEND Probe Request RECEIV Probe Response ReAssociation Response ny Authentication SEND ReAssociation Request RECEIVE ReAssociation Response YES US 7 694 017 B2 US 7 694 017 B2 1 COMMUNICATION APPARATUS IP ADDRESS ACQUISITION METHOD AND ROAMING METHOD BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention relates to communication appara tuses connecting between a terminal and a network by wire less and more particularly to a communication apparatus an IP address acquisition method and a roaming method in which the terminal can acquire an IP address from an address ing server 2 Description of the Related Art In order to communicate by using IP Internet Protocol in a network such as a LAN Local Area Network it is neces
15. US007694017B2 a2 United States Patent 10 Patent No US 7 694 017 B2 Saitoh 45 Date of Patent Apr 6 2010 54 COMMUNICATION APPARATUS IP 6 687 755 Bl 2 2004 Fordetal meo 709 245 ADDRESS ACQUISITION METHOD AND ROAMING METHOD 75 Inventor Atsushi Saitoh Tama JP 73 Assignee Mitsumi Electric Co Ltd Tokyo JP Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 940 days 21 Appl No 10 293 639 22 Filed Nov 13 2002 65 Prior Publication Data US 2003 0097473 A1 May 22 2003 30 Foreign Application Priority Data Nov 16 2001 JP esses 2001 351469 51 Int CI G06F 15 16 2006 01 52 UIS CL deett peers 709 245 58 Field of Classification Search 709 245 See application file for complete search history 56 References Cited U S PATENT DOCUMENTS 6 064 649 A 5 2000 Johnston 370 310 2 6 195 705 B1 2 2001 Leung eee 709 245 5 2001 Nishino 455 435 2 6 2001 Karlsson etal 370 244 6 2003 Sharony 370 312 7 2003 Peters se 709 220 6 233 452 B1 6 246 670 B1 6 577 600 B2 6 601 093 B1 PC DHCP CLIENT 5 2005 Grob et al 370 335 6 894 994 Bl 709 229 2001 0023446 Al 9 2001 Balogh 2001 0024953 Al 9 2001 Balogh 455 432 2002 0045423 Al 4 200
16. ded according to another aspect ofthe present invention an IP address acquisition method for acquiring an IP address for a terminal from a dynamic addressing server in a communication system having a first communication apparatus connected with the terminal and a second communication apparatus connected with the dynamic addressing server wherein the first communication apparatus communicates via the second communication apparatus connected by wireless with the first communication apparatus the method comprising the steps of establishing a communication path between the first communication appa ratus and the second communication apparatus in a case US 7 694 017 B2 3 where it is possible to connect the first communication appa ratus to the second communication apparatus when the first communication apparatus receives an IP address request mes sage from the terminal transferring the IP address request message to the dynamic addressing server and acquiring an IP address for the terminal from the dynamic addressing server via the communication path In the above mentioned IP address acquisition method the first communication apparatus may serve for the step ofestab lishing a communication path between the first communica tion apparatus and the second communication apparatus and the step of transferring the IP address request message to the dynamic addressing server and the terminal may serve for the step of acquiring an IP address for t
17. e process proceeds to the AP mode at step S102 In this case since the communication apparatus the STA 10 isinthe STA mode the process proceeds to step S103 At step 103 it is determined whether or not the STA 10 is connected with an RJ 45 cable and in other words whether or not the STA 10 is connected with the physical layer If not this step is repeated until the STA 10 has a connection with the physi cal layer If the connection is established at step S104 it is determined whether or not an IP address acquisition setting of the STA 10 is set as an automatic setting If not the process proceeds to step S105 of a manual setting If the IP address acquisition setting is automatic the STA 10 sends a message DHCP RELEASE for the following reason When the PC 14 has already an IP address it is likely to lack consistency with the STA 10 Thus the STA sends the message one more time in order to invalidate the IP address allocated to the PC 14 Then at step S107 the STA 10 executes a normal opera tion The normal operation means that the STA 10 is in a state wherein the STA 10 is currently waiting for data or a message This state continues until the STA 10 receives the message DHCP DISCOVER from the PC 14 that has received the message DHCP RELEASE At step S109 when receiving the message DHCP DISCOVER the STA 10 sends a mes sage DHCP OFFER to the PC 14 and then is waiting for a message DHCP REQUEST f
18. econd communication apparatus when the first communication apparatus receives an IP address request message from the terminal discarding the temporary IP address from the terminal when it is possible to connect the first communication apparatus with the second communica tion apparatus and establish a communication path and acquiring an IP address for the terminal from the dynamic addressing server via the communication path In the above mentioned IP address acquisition method the first communication apparatus may serve for the step of pro viding a temporary IP address to the terminal and the step of discarding the temporary IP address from the terminal and the terminal may serve for the step of acquiring an IP address for the terminal According to the above mentioned invention in a state that there is no connection between the first communication appa ratus and the second communication apparatus and the first communication apparatus cannot connect to the second com munication apparatus when receiving an IP address request message from the terminal the first communication appara tus provides the terminal with a temporary IP address After establishing a connection with the second communication apparatus the first communication apparatus makes the ter minal discard the temporary IP address and the terminal can acquire an IP address from the dynamic addressing server via the established communication path Additionally there is provi
19. f the second communication apparatuses to the another one of the an 5 20 25 30 40 45 55 60 65 4 second communication apparatuses Also even if the termi nal has already acquired an IP address from the dynamic addressing server the terminal can acquire an IP address corresponding to a network address to which the another one of the second communication apparatuses belongs by dis carding the old IP address if necessary As a result the roam ing is successfully accomplished Additionally there is provided according to another aspect of the present invention a communication apparatus for relay ing by wireless between a terminal and a dynamic addressing server comprising a temporary IP address providing part providing the terminal with a temporary IP address when an IP address request message is received from the terminal and a temporary IP address throwing part discarding the tempo rary IP address from the terminal According to the above mentioned invention when it is impossible to establish a communication path with the dynamic addressing server the temporary IP address part makes it possible to communicate between the communica tion apparatus and the terminal Once the communication path between the dynamic addressing server and the terminal is established the temporary IP throwing part makes the terminal discard an IP address and send an IP address request message again As a result the terminal ca
20. g a DHCP OFFER to the DHCP client the DHCP client transmitting a DHCP REQUEST for an IP address to the STA the STA transmitting a DHCP ACK and the temporary IP address to the DHCP client and the DHCP client acquiring the temporary IP address by receiving the DHCP ACK thereby establishing a physi cal communication between the DHCP client and the STA and the method further comprises upon establishing the physi cal communication between the DHCP client and the STA initialing the wireless communication between the STA and the AP
21. he terminal According to the above mentioned invention in a state that there is no connection between the first communication appa ratus and the second communication apparatus when receiv ing an IP address request message from the terminal the first communication apparatus attempts to connect to the second communication apparatus After establishing a communica tion path the first communication apparatus sends the IP address request message to the dynamic addressing server via the established communication path As a result the terminal can acquire an IP address from the dynamic addressing server Additionally there is provided according to another aspect of the present invention a roaming method for conducting a roaming in a communication system having a first communi cation apparatus connected with a terminal and a plurality of second communication apparatuses connected with a dynamic addressing server wherein the first communication apparatus has communicated via one of the second commu nication apparatuses that maintains a connection by wireless with the first communication apparatus and conducts a roam ing from the one of the second communication apparatuses to another one of the second communication apparatuses the method comprising the steps of requesting a reconnection with the another one of the second communication appara tuses and establishing a communication path when the first communication apparatus detects a disconnec
22. l now be given with reference to a flow chart of FIG 6 ofa process regarding the AP mode It should be noted that the process regarding the AP mode shown in FIG 6 is related to the connection between the AP 12 and the DHCP server 18 At step S201 it is determined whether or not a communi cation apparatus is in the AP mode If the communication apparatus is not in the AP mode the process proceeds to the STA mode at step S202 Since the communication apparatus the AP 12 is in the AP mode in this case the process proceeds to step S203 At step S203 it is determined whether ornot the AP 12 is connected with an RJ 45 cable and in other words whether or not the AP 12 is connected with the physi cal layer If not this step is repeated until the AP 12 has a connection with the physical layer If the connection is estab lished at step S204 it is determined whether or not an IP address acquisition setting of the AP 12 is set as an automatic setting If not the process proceeds to step S205 of a manual setting If the IP address acquisition setting is automatic the AP 12 sends a message DHCP DISCOVER to the DHCP server 18 and is waiting for a message DHCP OFFER When receiving the message DHCP OFFER at step S207 the AP 12 sends a message DHCP REQUEST to the DHCP server 18 at step S208 and is waiting for a message DHCP ACK from the DHCP server 18 When receiving the mes sage DHCP ACK at step S209 the AP 12
23. le 192 168 1 2 is allocated to the PC 14 by the STA 10 In the above manner since the STA 10 has a connection with the PC 14 the above mentioned some settings regarding the STA 10 can be manipulated from the PC 14 Now since the STA 10 and the PC 14 are connected each other if the STA 10 and the AP 12 are connected the PC 14 and the network 16 are connected Regarding a connection between the STA 10 andthe AP 12 at step 9 the STA 10 sends a message Probe Request to the AP 12 At step 10 the AP 12 sends a message Probe Response back to the STA 10 The exchange of these mes sages serves to check whether or not it is possible to commu nicate between the STA 10 and the AP 12 At steps 11 and 12 the STA 10 and the AP 12 send messages Authentica US 7 694 017 B2 7 tion each other to authenticate between the STA 10 and the AP 12 After completing the authentication the STA 10 sends a message Association Request to the AP 12 so as to con nect thereto At step 14 the AP 12 sends a message Asso ciation Response together with an IP address 172 16 40 10 back to the STA 10 This IP address is the address that has been already allocated to the AP 12 by the DHCP server 18 The STA 10 uses this IP address as its own address instead of the default IP address of the STA 10 After completing the connection between the STA 10 and the AP 12 in the above manner the STA 10 sends a message DHCP RELEASE
24. n acquire an IP address from the dynamic addressing server Additionally there is provided according to another aspect of the present invention a communication apparatus for relay ing by wireless between a terminal and a dynamic addressing server comprising a maintaining part maintaining an IP address request message when the IP address request mes sage is received from the terminal and a transferring part transferring the IP address request message maintained According to the above mentioned invention when an IP address request message is received from the terminal if it is possible to establish a connection path between the terminal and the dynamic addressing server the IP address request message is maintained After the communication path is established the maintained IP address request message is transferred to the dynamic addressing server and an IP address is allocated to the terminal Other objects features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a diagram illustrating a configuration ofa wireless LAN FIG 2 is adiagram illustrating a configuration ofa wireless LAN according to an embodiment of the present invention FIG 3 is a block diagram illustrating hardware of a com munication apparatus FIG 4 is a sequence diagram illustrating how a DHCP server
25. ntrol such a data receiving and sending process A description will now be given of the above mentioned operational mode As the operational mode there are pre pared at least two modes a station mode Hereinafter notated as an STA mode and an access point mode Hereinafter notated as an AP mode The STA mode is a mode as the communication apparatus 10 for performing a connecting process with the PC 14 The AP mode is a mode as the communication apparatus 12 for performing a connecting process with the network 16 and serving as an access point between the communication apparatus 10 and the network 16 A description will now be given of some settings regarding the communication apparatuses 10 and 12 Among primary setting items regarding the communication apparatuses 10 and 12 there are a mode setting regarding the above opera tional modes an SSID setting a cipher setting an authenti cation setting and a roaming setting The SSID is a kind ofa name of an apparatus and is an ID represented as a sequence formed of32 characters of an ASCII code The cipher setting which is involved in ciphering data exchanged between the STA mode and the AP mode sets a ciphering mode a bit length a type of cipher and a length of key The authentica tion setting which is involved in authentication between an 20 25 30 35 40 45 50 55 60 65 6 apparatus in the STA mode and an apparatus in the AP mode sets an authentica
26. on each other through the above mentioned process The PC 14 acquires the IP address in accordance with the procedure of the DHCP shown in FIG 4 Under the above mentioned embodiment of the present invention the operations 9 through 14 in FIG 4 the opera tions S112 through S117 in FIG 5 and the operations 6 through 11 in FIG 6 correspond to a means to establish a communication path Also the operation 6 in FIG 4 and the operation 109 in FIG 5 correspond to a means to provide a temporary IP address The operation 15 in FIG 4 and the operation 118 in FIG 5 correspond to a mean to discard the temporary IP address The operations 303 through 311 correspond to a reconnect request at a roaming The present invention is not limited to the specifically disclosed embodiments and variations and modifications may be made without departing from the scope of the present invention The present application is based on Japanese priority appli cation No 2001 351469 filed Nov 16 2001 the entire con tents of which are hereby incorporated by reference What is claimed is 1 A method for acquiring an IP address for a DHCP client from a DHCP server in a wireless communication system the wireless communication system including a station STA physically connected with the DHCP client and an access point AP physically connected with the DHCP server wherein in response to receipt of an IP address request from the AP via a net
27. other PC via the network 16 A description will now be given of a correspondence between the PC 14 and the STA 10 Suppose that the PC 14 has a setting in which the PC 14 acquires an IP address by the DHCP Further suppose that an IP address for example 192 16 8 1 1 is allocated to the SAT 10 as a default and that the SAT 10 continues the IP address until the SAT knows an IP address of the AP 12 by establishing a connection with the AP 12 Currently the STA 10 and the AP 12 are assumed to have no connection each other In the above state at step 5 the PC 14 sends a message DHCP DISCOVER to the STA 10 At this time the STA 10 attempts to connect to the AP 12 At step 6 the STA 10 sends a message Probe Request to the AP 12 At step 7 the AP 12 sends a message Probe Responses back to the STA 10 The exchange of these messages serves to check whether or not it is possible to communicate between the STA 10 and the AP 12 At steps 8 and 9 the STA 10 and the AP 12 senda message Authentication each other to authenticate After completing the authentication at step 10 the STA 10 sends a message Association Request to the AP 12 so as to con nect thereto At step 11 the AP 12 sends a message Asso ciation Response together with an IP address 172 16 40 10 back to the STA 10 This IP address is the address that has been already allocated to the AP 12 by the DHCP server 18 The STA 10 uses this IP
28. proceeds to the normal operation at step S210 The process to allocate an IP address to the PC 14 by using the DHCP has been described under the case that it is impossible to connect with the com munication apparatus 12 when the communication apparatus 10 receives an IP address request from the PC 14 A description will now be given with reference to FIG 7 ofthe case that it is possible to connect with the communica tion apparatus 12 when the communication apparatus 10 receives an IP address request from the PC 14 At the beginning at step 1 the AP 12 sends a message DHCP DISCOVER search to search a DHCP server 18 At step 2 the DHCP server 18 sends a message DHCP OFFER reply for search back to the AP 12 to show that the DHCP server 18 works At step 3 the AP 12 sends a mes sage DHCP REQUEST IP address request to the DHCP server 18 At step 4 the DHCP server sends a message DHCP ACK reply for IP address request back to the AP 12 and an IP address for example 172 16 40 10 is allocated to the AP 12 by the DHCP server 18 On the other hand when the DHCP server 18 cancels out an IP address that has been allocated to a DHCP client the DHCP server 18 sends a message DHCP RELEASE to invalidate the IP address allocated In the above manner since the AP 12 has a connec US 7 694 017 B2 9 tion with the network 16 the above mentioned some settings regarding the AP 12 can be manipulated from an
29. rom the PC 14 At step S110 when receiving the message DHCP REQUEST the STA 10 sends a message DHCP ACK to the PC 14 Through the above process the PC 14 acquires a temporary IP address Then the STA 10 proceeds to a process for connecting with the AP 12 At step 112 the STA 10 sends a message Probe 0 a 5 20 25 30 35 40 45 50 60 8 Request to the AP 12 and is waiting for a message Probe Response from the AP 12 When receiving the message Probe Response at step S113 the STA 10 sends a message Authentication to authenticate and is waiting for the mes sage Authentication from the AP 12 When receiving the message Authentication at step S115 the STA 10 sends a message Association Request to connect with the AP 12 and is waiting for a message Association Response At step S117 the STA 10 receives the message Association Response from the AP 12 Through the above process the STA 10 has the connection with the AP 12 Now the PC 14 is ready to communicate with the DHCP server 18 via the two communication apparatuses In order to establish the connec tion with the DHCP server 18 properly the STA to needs to let the PC 14 discard the temporary address that the STA 10 has already provided for the PC 14 Thus the STA 10 sends a message DHCP RELEASE to the PC 14 at step S118 and executes the normal operation at step S119 A description wil
30. tion algorithm These settings can be set by connecting with a computer such as a PC The description will now be given of a way in which the PC 14 acquires an IP address from the DHCP server 18 by using the communication apparatuses 10 and 12 provided under the above mentioned configuration The description will be given separately from two cases One case is that it is impos sible to connect with the communication apparatus 12 when the communication apparatus 10 receives an IP address request from the PC 14 The other is that it is possible to connect with the communication apparatus 12 when the com munication apparatus 10 receives an IP address request from the PC 14 It should be noted that the communication appa ratuses 10 and 12 are represented as an STA 10 and an AP 12 in the following description respectively A description will now be given with reference to FIG 4 of the case that it is impossible to connect with the commu nication apparatus 12 when the communication apparatus 10 receives an IP address request from the PC 14 At the begin ning at step 1 the AP 12 sends a message DHCP DIS COVER search to search a DHCP server 18 At step 2 the DHCP server 18 sends a message DHCP OFFER reply for search back to the AP 12 to show that the DHCP server 18 works At step 3 the AP 12 sends a message DHCP REQUEST IP address request to the DHCP server 18 At step 4 the DHCP server sends a message DHCP ACK
31. tion between the first communication apparatus and the one of the second communication apparatuses discarding an IP address from the terminal when a network address of the one of the second communication apparatuses is different from a network address of the another one of the second communication apparatuses and acquiring an IP address from the dynamic addressing server via the communication path established by a reconnection request of the first communication apparatus and conducting a roaming from the one of the second com munication apparatuses to the another one of the second communication apparatuses In the above mentioned roaming method the first commu nication apparatus may serve for the step of requesting a reconnection with the another one of the second communica tion apparatuses and establishing a communication path and the step of discarding an IP address from the terminal and the terminal may serve for the step of acquiring an IP address from the dynamic addressing server According to the above mentioned invention even if the first communication apparatus has already acquired an IP address from the dynamic addressing server when the first communication apparatus detects a disconnection with one of the second communication apparatuses the first communica tion apparatus can request a reconnection with another one of the second communication apparatuses establish a commu nication path and accomplish a roaming from the one o
32. work the DHCP server assigns a first IP address to the AP in response to detection of a physical connection with the DHCP client the STA assigns a possessed temporary IP address to the STA itself and the DHCP client thereby US 7 694 017 B2 11 establishing a communication between the DHCP client and the STA via the physical connection and enabling the DHCP client to set the STA in response to receipt of an IP address request from the DHCP client via a default IP address pre assigned to the STA the STA transmits temporary IP address to the DHCP client in response to detection of a physical connection with the DHCP server the DHCP server assigns an IP address thereby establishing a communication between the DHCP server and the AP via the physical connection and enabling the DHCP server to set the AP when the STA establishes a wireless connection with the AP the STA acquires the first IP address and transmits an IP address release to the DHCP client to cause the DHCP client to invalidate the temporary IP address in response to receipt of the IP address release from the STA the DHCP client invalidates the temporary IP address and transmits an IP address request to the DHCP 15 12 server via the STA and the AP wirelessly connected with each other to acquire a second IP address dedicated to the DHCP client wherein the setting the STA comprises the DHCP client transmitting a DHCP DISCOVER to the STA the STA transmittin
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