IETF QUICに至るプロトコルの透過性問題とその対策

26*$ʹ͍ͭͯ ฏ੒29೥12݄5೔ ୈ̎ճΠϯλʔωοτ௨৴ϓϩτίϧͷ௨৴ίωΫγϣϯվળʹؔ͢Δҙݟަ׵ձ Ϡϑʔגࣜձࣾେ௡ൟथ *&5'26*$ʹࢸΔϓϩτίϧͷಁաੑ໰୊ͱͦͷରࡦ

%JTDMBJNFS ຊൃදٴͼࢿྉͷ಺༰͸ɺϠϑʔגࣜձࣾΛ୅දͨ͠΋ͷͰ ͸͋Γ·ͤΜɻ͝ཧղɺྃ͝ঝ͍ͨͩ͘Α͏͓ئ͍க͠·͢ɻ

಺༰ w ݱࡏ*&5'26*$͸࢓༷ࡦఆ࡞ۀͷਅͬ࠷தͰ͋Γɺݱࡏͷ υϥϑτͷ಺༰͸ࠓޙେ͖͘มߋ͞ΕΔՄೳੑ͕͋Γ·͢ɻ w *&5'26*$ͷಛ௃ͱͯ͠Ӆಗੑ͕͋ΓɺػີੑΛ࣮ݱ͢Δ ηΩϡϦςΟཁ͚݅ͩͰͳ͘ϓϩτίϧͷಁաੑΛͰ͖Δ ͚ͩ֬อ͢Δ໨తʹ΋ͳ͍ͬͯ·͢ɻ w աڈɺ֤छϓϩτίϧʹ͓͍ͯػೳ֦ுΛ્Μͩඇಁաੑ
ͷࣄྫͱɺͦΕΛड͚ͨ*&5'26*$࢓༷ʹ͓͚ΔಁաੑΛ ߴΊΔ࢓૊Έʹ͍ͭͯ࿩Λ͠·͢ɻ

1SPUPDPM0TTJpDBUJPO ࠓճ঺հ͢Δ1SPUPDPM0TTJpDBUJPOͷࣄྫ w 5$1ɺ5-4ɺ(PPHMF26*$ .JEEMF#PY 4FSWFS $MJFOU

5$10TTJpDBUJPO

5$16OLOPXO0QUJPOͷಁաੑ *TJU4UJMM1PTTJCMFUP&YUFOE5$1 IUUQDPOGFSFODFTTJHDPNNPSHJNDEPDTQQEG IUUQTUSBOTQBSFODZSFQPSUHPPHMFDPNIUUQTPWFSWJFX ݱࡏͷํ͕)5514ͷ%FQMPZ͕ਐΈɺUDQͷಁաੑ͸ΑΓམ͍ͪͯΔ͔΋͠Εͳ͍ɻ )5514ͷϖʔδಡΈࠐΈ཰ 64 ɺ+1

5$1'BTU0QFO ͷಁաੑ "QQMFɿz.PTUMZ 5'0XPSLTTVDDFTTGVMMZ d TVDDFTTSBUF #BENJEEMFCPYFTBSFJOUFSGFSJOH XJUI5$1'BTU0QFO
.JDSPTPGUʮ5$1'BTU0QFOඪ४Λ׬શʹαϙʔτ͍ͯ͠ ͳ͍ωοτϫʔΫ؀ڥͷ.JDSPTPGU&EHFϢʔβʔ͕ɺҰ෦ ͷ8FCαΠτʹ઀ଓͰ͖ͳ͍໰୊Λमਖ਼͠·ͨ͠ɻϢʔβʔ ͸BCPVUqBHTͰ5$1'BTU0QFOΛ࠶༗ޮԽ͢Δ͜ͱ͕Ͱ ͖·͢ɻʯ IUUQTUPPMTJFUGPSHIUNMSGD IUUQTXXXOBOPHPSHTJUFTEFGBVMUpMFT1BBTDI@/FUXPSL@4VQQPSUQEG IUUQTTVQQPSUNJDSPTPGUDPNKBKQIFMQXJOEPXTVQEBUFLC

5$1XJOEPXͷ্ݶ 5IF26*$5SBOTQPSU1SPUPDPM%FTJHOBOE*OUFSOFU4DBMF%FQMPZNFOU IUUQTTUBUJDHPPHMFVTFSDPOUFOUDPNNFEJBSFTFBSDIHPPHMFDPNKBQVCTBSDIJWFQEG 6.5 Video Rebuffer Rate ... We believe
that the low advertised maximum receive window for TCP is likely due to the absence of window scaling, which in turn may be caused by legacy clients that lack support for it and/or middlebox interference. ׂ͕̒ۙ͘ ,#ҎԼ

5-40TTJpDBUJPO

5-4'BMTF4UBSU ͷಁաੑ $ISPNF POUIFEFWDIBOOFMBUpSTU XJMMDPOUBJOB MJTUPGUIFPGQSPCMFNBUJDTJUFTBOEXFXPOU VTF'BMTF4UBSUXJUIUIFN 0OF
GBJSMZNBKPS 44-UFSNJOBUPSWFOEPSSFGVTFE UPVQEBUFUPpYUIFJS'BMTF4UBSUJOUPMFSBODF EFTQJUFQSPCMFNTUIBUUIFJSDVTUPNFSTXFSF IBWJOH IUUQTUPPMTJFUGPSHIUNMSGD IUUQTXXXJNQFSJBMWJPMFUPSHCMBDLMJTUJOHIUNM IUUQTXXXJNQFSJBMWJPMFUPSHGBMTFTUBSUIUNM

5-4"-1/ ͷಁաੑ IUUQTUPPMTJFUGPSHIUNMSGD IUUQTUPPMTJFUGPSHIUNMSGD IUUQEIBUFOBOFKQKPWJ IUUQEIBUFOBOFKQKPWJ ෛՙ෼ࢄϕϯμʔͷΤϯδχΞΑΓόΠτ௒Ͱ໰୊͕ղܾ͞ΕΔͱ͍͏৘ใΛड͚ɺ
$MJFOU)FMMPΛόΠτҎ্ʹ๲Β·ͤΔQBEEJOHFYUFOTJPO Λಋೖ͠ղܾɻ

5-4 ESBGU ͷಁաੑ 7FSTJPO/FHPUJBUJPOΛ$MJFOU)FMMPͷFYUFOTJPOʹมߋ 3FDPSE-BZFSதͷ7FSTJPO'JFMEΛ5-4ʹݻఆ

5-4 ESBGU ͷಁաੑ ಁաੑΛ๦͛Δ.JEEMFCPYϕϯμʔ໊Λެ։͢΂͖ͱͷ੠΋͋ͬͨ ͕ɺΞοϓσʔτ͠ͳ͍ϢʔβଆͷݪҼ΋͋Δͱͷ͜ͱͰɺESBGU Ͱ͸ݟ্͔͚5-4ͱ΄΅۠ผ͕͔ͭͳ͍Α͏ʹมߋɻ IUUQTEBUBUSBDLFSJFUGPSHNFFUJOHNBUFSJBMTTMJEFTUMTTFTTBUMT

(PPHMF26*$ 0TTJpDBUJPO

(PPHMF26*$ͷಁաੑ &YQFSJFODFTXJUI.JEEMFCPYFT w 8FJEFOUJpFEUIFNJEEMFCPYBOESFBDIFEPVUUP UIFWFOEPS5IFWFOEPSBEESFTTFEUIFJTTVFCZ VQEBUJOHUIFJSDMBTTJpFSUPBMMPXUIFWBSJBUJPOTTFFO JOUIFqBHT5IJTpYXBTSPMMFEPVUUPUIFJS DVTUPNFSTPWFSUIFGPMMPXJOHNPOUI 5IF26*$5SBOTQPSU1SPUPDPM%FTJHOBOE*OUFSOFU4DBMF%FQMPZNFOU IUUQTTUBUJDHPPHMFVTFSDPOUFOUDPNNFEJBSFTFBSDIHPPHMFDPNKBQVCTBSDIJWFQEG

(PPHMF26*$ͷಁաੑ w ೥݄೔$ISPNF4UBCMF$IBOOFM6QEBUF . w IUUQTDISPNFSFMFBTFTHPPHMFCMPHDPN TUBCMFDIBOOFMVQEBUFGPSEFTLUPQIUNM w HPPHMFDPNΛݟΔͱ&33@26*$@13050$0-@&3303͕සൃ
w IUUQTCVHTDISPNJVNPSHQDISPNJVNJTTVFTEFUBJM JE w .D"GFFϢʔβ͔ΒͷJTTVFɻ͕ͩ࠷ऴతͳݪҼ͸ެද͞Εͣɻ

(PPHMF26*$@7&34*0/@8JSF'PSNBU 1VCMJD'MBHT CZUF 1VCMJD 'MBHT DPOOFDUJPO *%
2VJD 7FSTJPO 4FRVFODF /VNCFS 1SJWBUF 'MBHT '&$ 'SBNF 'SBNF SFTFSWFE NVMJUJQBUI qBH QBDLFUOVNCFSMFOHUI CZUF CZUFT CZUFT CZUFT DPOOFDUJPOJEMFOHUI CZUFT CZUF CZUFT CZUFT STU WFSTJPO

(PPHMF26*$@7&34*0/@8JSF'PSNBU 1VCMJD'MBHT CZUF
SFTFSWFE NVMJUJQBUI qBH QBDLFUOVNCFSMFOHUI CZUF CZUFT CZUFT CZUFT DPOOFDUJPOJE MFOHUI CZUFT CZUFT OPODF qBH STU WFSTJPO 1VCMJD 'MBHT DPOOFDUJPO *% 2VJD 7FSTJPO /PODF 4FRVFODF /VNCFS 1SJWBUF 'MBHT '&$ 'SBNF 'SBNF

໰୊Λىͨ͜͠෦෼ 21VCMJD'MBHT CZUF
SFTFSWFE NVMJUJQBUI qBH QBDLFUOVNCFSMFOHUI CZUF CZUFT CZUFT CZUFT DPOOFDUJPOJE MFOHUI CZUFT CZUFT OPODF qBH STU WFSTJPO 21VCMJD'MBHT CZUF SFTFSWFE NVMJUJQBUI qBH QBDLFUOVNCFSMFOHUI CZUF CZUFT CZUFT CZUFT DPOOFDUJPOJEMFOHUI CZUFT CZUF CZUFT CZUFT STU WFSTJPO CJUͷ࢓༷มߋ ͕ಁաੑΛ્֐

*&5'26*$%SBGUͷ 0TTJpDBUJPOରࡦ ஫ ҙ ɻ ক དྷ ม ߋ ͢
Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ

*&5'26*$W ஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ
Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ

*&5'26*$ESBGU8JSF'PSNBU -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF
7FSTJPO/FHPUJBUJPO $MJFOU*OJUJBM 4FSWFS4UBUFMFTT3FUSZ 4FSWFS$MFBSUFYU $MJFOU$MFBSUFYU 3551SPUFDUFE $POOFDUJPO*% 1BDLFU /VNCFS 7FSTJPO $MFBSUFYU 1BZMPBE 4IPSU)FBEFS )FBEFS 'PSN TIPSU $POOFDUJPO *%'MBH PNJUUFE QSFTFOFE ,FZ 1IBTF #JU 5ZQF 1BDLFU /VNCFS4J[F PDUFU PDUFUT PDUFUT $POOFDUJPO*% 1BDLFU /VNCFS 1SPUFDUFE1BZMPBE ஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ CZUF "&"%1SPUFDUFE "&"%1SPUFDUFE 5-4Ͱ҉߸Խ ޙड़Ͱ҉߸Խ

ର.JEEMFCPYͷ࢓૊Έ 26*$$MFBSUFYU๷ޚ w ϋϯυγΣΠΫதͷ$MFBSUFYUΛESBGU͔Β'/7Bϋογϡ͔Β 5-4@"&4@@($.@4)"Ͱ҉߸Խʹมߋɻ΋ͱ΋ͱ͸σʔλΤϥʔݕ஌༻్ɻ w 26*$όʔδϣϯݻ༗ͷTBMUͱDMMJFOUDPOOFDUJPOJE͔Βڞ༗伴Λੜ੒ɻ w ׬શʹػີੑ΍׬શੑΛकΔΘ͚Ͱ͸ͳ͍͕ɺӅಗੑ͕େ͖͘޲্ɻόʔδϣϯ্͕ ͕ΔͱTBMUΛߋ৽͠ͳ͍ݶΓϛυϧϘοΫε͕ղಡͰ͖ͳ͘ͳΔɻ
஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF 7FSTJPO/FHPUJBUJPO $MJFOU*OJUJBM 4FSWFS4UBUFMFTT3FUSZ 4FSWFS$MFBSUFYU $MJFOU$MFBSUFYU 3551SPUFDUFE $POOFDUJPO*% 1BDLFU /VNCFS 7FSTJPO $MFBSUFYU 1BZMPBE "&4($.Ͱ҉߸Խ "&"%1SPUFDUFE

ର.JEEMFCPYͷ࢓૊Έ 4UBUFMFTT3FTFU w αʔό͕ΫϥογϡͳͲͰDPOOFDUJPOTUBUFΛҡ࣋Ͱ͖ͳ͍৔߹ʹΫϥ ΠΞϯτʹ&OE5P&OEͰ3FTFUΛ௨஌͢Δ࢓૊Έɻ1BUI͕มΘΓ 4PVSDF"EESFTT7BMJEBUJPO͕Ͱ͖ͳ͍৔߹Ͱ΋3FTFU͕ՄೳʹͳΔɻ w ࣄલʹαʔόΫϥΠΞϯτؒͰ҉߸Խ͞ΕͨϋϯυγΣΠΫதʹ 4UBUFMFTT3FTFU5PLFOΛަ׵ɻ w
௨ৗͷ26*$ϑϨʔϜʹࣅͤͯ࠷ޙʹ4UBUFMFTT3FTFU5PLFOΛ෇༩ɻ .JEEMFCPY͸҉߸Խ͞Εͨ௨ৗͷ26*$௨৴ͳͷ͔4UBUFMFTT3FTFU͔۠ ผ͕͔ͭͳ͍͠ɺ3FTFUΛ4QPPG͢Δ͜ͱ΋ෆՄೳɻ ஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ )FBEFS 'PSN TIPSU $POOFDUJPO *%'MBH PNJUUFE QSFTFOFE ,FZ 1IBTF #JU 5ZQF 1BDLFU /VNCFS4J[F PDUFU PDUFUT PDUFUT $POOFDUJPO*% 1BDLFU /VNCFS 3BOEPN0DUFU 4UBUFMFTT3FTFU 5PLFO

1VCMJD)FBEFSΛΊ͙Δٞ࿦ -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF
7FSTJPO/FHPUJBUJPO $MJFOU*OJUJBM 4FSWFS4UBUFMFTT3FUSZ 4FSWFS$MFBSUFYU $MJFOU$MFBSUFYU 3551SPUFDUFE 4IPSU)FBEFS )FBEFS 'PSN TIPSU $POOFDUJPO *%'MBH PNJUUFE QSFTFOFE ,FZ 1IBTF #JU 5ZQF 1BDLFU /VNCFS4J[F PDUFU PDUFUT PDUFUT CZUF CZUF 6%1.VMUJQMFYJOHPG4351%5-4 3'$ WT26*$ IUUQTEBUBUSBDLFSJFUGPSHEPDIUNMESBGUUIPNTPONVYQSJODJQMFT 4QJO#JUGPS355NFBTVSFNFOU IUUQTEBUBUSBDLFSJFUGPSHEPDESBGUUSBNNFMMRVJDTQJO ஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ ৄ͘͠͸*&5'ͷ26*$8(.JOVUFTΛࢀরͯ͠Լ͍͞ɻ

26*$*OWBSJBOUTͷٞ࿦ 7FSTJPO*OEFQFOEFOU1SPQFSUJFTPG26*$ IUUQTEBUBUSBDLFSJFUGPSHEPDESBGUUIPNTPORVJDJOWBSJBOUT ஫ ҙ ɻ ক དྷ ม ߋ
͢ Δ Մ ೳ ੑ ͕ ͋ Γ · ͢ɻ ৄ͘͠͸*&5'ͷ26*$8(.JOVUFTΛࢀরͯ͠Լ͍͞ɻ -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF 7FSTJPO/FHPUJBUJPO $MJFOU*OJUJBM 4FSWFS4UBUFMFTT3FUSZ 4FSWFS$MFBSUFYU $MJFOU$MFBSUFYU 3551SPUFDUFE $POOFDUJPO*% 7FSTJPO 1BDLFU /VNCFS 1BZMPBE 4IPSU)FBEFS )FBEFS 'PSN TIPSU $POOFDUJPO *%'MBH PNJUUFE QSFTFOFE ,FZ 1IBTF #JU 5ZQF 1BDLFU /VNCFS4J[F PDUFU PDUFUT PDUFUT $POOFDUJPO*% 1BDLFU /VNCFS 1SPUFDUFE1BZMPBE 26*$*OWBSJBOUTҊ

*&5'26*$8($IBSUFS 5IFpGUIGPDVTBSFBXJMMQSPWJEFBO"QQMJDBCJMJUZBOE .BOBHFBCJMJUZ4UBUFNFOU EFTDSJCJOHIPX BOEVOEFSXIBU DJSDVNTUBODFT 26*$NBZCFTBGFMZVTFE BOEEFTDSJCJOH EFQMPZNFOUBOENBOBHFBCJMJUZJNQMJDBUJPOTPGUIFQSPUPDPM
"QQMJDBCJMJUZPGUIF26*$5SBOTQPSU1SPUPDPM IUUQTEBUBUSBDLFSJFUGPSHEPDESBGUJFUGRVJDBQQMJDBCJMJUZ .BOBHFBCJMJUZPGUIF26*$5SBOTQPSU1SPUPDPM IUUQTEBUBUSBDLFSJFUGPSHEPDESBGUJFUGRVJDNBOBHFBCJMJUZ ௨৴ۀऀ༷ʹ͸ͪ͜Βͷํ͕ॏཁɻ ͋Δఔ౓࢓༷͕མͪண͍͔ͯΒυϥϑτ͕ਐΉ͜ͱʹͳΓ·͢ɻ

IETF QUICに至るプロトコルの透過性問題とその対策

IETF QUICに至るプロトコルの透過性問題とその対策

Shigeki Ohtsu

More Decks by Shigeki Ohtsu

Other Decks in Technology

Featured

Transcript

26$ʹ͍ͭͯ ฏ੒29೥12݄5೔ ୈ̎ճΠϯλʔωοτ௨৴ϓϩτίϧͷ௨৴ίωΫγϣϯվળʹؔ͢Δҙݟަ׵ձ Ϡϑʔגࣜձࣾେ௡ൟथ &5'26*$ʹࢸΔϓϩτίϧͷಁաੑ໰୊ͱͦͷରࡦ

%JTDMBJNFS ຊൃදٴͼࢿྉͷ಺༰͸ɺϠϑʔגࣜձࣾΛ୅දͨ͠΋ͷͰ ͸͋Γ·ͤΜɻ͝ཧղɺྃ͝ঝ͍ͨͩ͘Α͏͓ئ͍க͠·͢ɻ

1SPUPDPM0TTJpDBUJPO ࠓճ঺հ͢Δ1SPUPDPM0TTJpDBUJPOͷࣄྫ w 5$1ɺ5-4ɺ(PPHMF26*$ .JEEMF#PY 4FSWFS $MJFOU

5$10TTJpDBUJPO

5$16OLOPXO0QUJPOͷಁաੑ *TJU4UJMM1PTTJCMFUP&YUFOE5$1 IUUQDPOGFSFODFTTJHDPNNPSHJNDEPDTQQEG IUUQTUSBOTQBSFODZSFQPSUHPPHMFDPNIUUQTPWFSWJFX ݱࡏͷํ͕)5514ͷ%FQMPZ͕ਐΈɺUDQͷಁաੑ͸ΑΓམ͍ͪͯΔ͔΋͠Εͳ͍ɻ )5514ͷϖʔδಡΈࠐΈ཰ 64 ɺ+1

5$1'BTU0QFO ͷಁաੑ "QQMFɿz.PTUMZ 5'0XPSLTTVDDFTTGVMMZ d TVDDFTTSBUF #BENJEEMFCPYFTBSFJOUFSGFSJOH XJUI5$1'BTU0QFO

5$1XJOEPXͷ্ݶ 5IF26$5SBOTQPSU1SPUPDPM%FTJHOBOEOUFSOFU4DBMF%FQMPZNFOU IUUQTTUBUJDHPPHMFVTFSDPOUFOUDPNNFEJBSFTFBSDIHPPHMFDPNKBQVCTBSDIJWFQEG 6.5 Video Rebuffer Rate ... We believe

5-40TTJpDBUJPO

5-4'BMTF4UBSU ͷಁաੑ $ISPNF POUIFEFWDIBOOFMBUpSTU XJMMDPOUBJOB MJTUPGUIFPGQSPCMFNBUJDTJUFTBOEXFXPOU VTF'BMTF4UBSUXJUIUIFN 0OF

5-4"-1/ ͷಁաੑ IUUQTUPPMTJFUGPSHIUNMSGD IUUQTUPPMTJFUGPSHIUNMSGD IUUQEIBUFOBOFKQKPWJ IUUQEIBUFOBOFKQKPWJ ෛՙ෼ࢄϕϯμʔͷΤϯδχΞΑΓόΠτ௒Ͱ໰୊͕ղܾ͞ΕΔͱ͍͏৘ใΛड͚ɺ

5-4 ESBGU ͷಁաੑ 7FSTJPO/FHPUJBUJPOΛ$MJFOU)FMMPͷFYUFOTJPOʹมߋ 3FDPSE-BZFSதͷ7FSTJPO'JFMEΛ5-4ʹݻఆ

5-4 ESBGU ͷಁաੑ ಁաੑΛ๦͛Δ.JEEMFCPYϕϯμʔ໊Λެ։͢΂͖ͱͷ੠΋͋ͬͨ ͕ɺΞοϓσʔτ͠ͳ͍ϢʔβଆͷݪҼ΋͋Δͱͷ͜ͱͰɺESBGU Ͱ͸ݟ্͔͚5-4ͱ΄΅۠ผ͕͔ͭͳ͍Α͏ʹมߋɻ IUUQTEBUBUSBDLFSJFUGPSHNFFUJOHNBUFSJBMTTMJEFTUMTTFTTBUMT

(PPHMF26*$ 0TTJpDBUJPO

(PPHMF26$ͷಁաੑ w ೥݄೔$ISPNF4UBCMF$IBOOFM6QEBUF . w IUUQTDISPNFSFMFBTFTHPPHMFCMPHDPN TUBCMFDIBOOFMVQEBUFGPSEFTLUPQIUNM w HPPHMFDPNΛݟΔͱ&33@26$@13050$0-@&3303͕සൃ

(PPHMF26$@7&340/@8JSF'PSNBU 1VCMJD'MBHT CZUF 1VCMJD 'MBHT DPOOFDUJPO *%

(PPHMF26$@7&340/@8JSF'PSNBU 1VCMJD'MBHT CZUF

໰୊Λىͨ͜͠෦෼ 21VCMJD'MBHT CZUF

&5'26$%SBGUͷ 0TTJpDBUJPOରࡦ ஫ ҙ ɻ ক དྷ ม ߋ ͢

&5'26$W ஫ ҙ ɻ ক དྷ ม ߋ ͢ Δ

&5'26$ESBGU8JSF'PSNBU -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF

1VCMJD)FBEFSΛΊ͙Δٞ࿦ -POH)FBEFS )FBEFS 'PSN MPOH 5ZQF

26$OWBSJBOUTͷٞ࿦ 7FSTJPOOEFQFOEFOU1SPQFSUJFTPG26$ IUUQTEBUBUSBDLFSJFUGPSHEPDESBGUUIPNTPORVJDJOWBSJBOUT ஫ ҙ ɻ ক དྷ ม ߋ

&5'26$8($IBSUFS 5IFpGUIGPDVTBSFBXJMMQSPWJEFBO"QQMJDBCJMJUZBOE .BOBHFBCJMJUZ4UBUFNFOU EFTDSJCJOHIPX BOEVOEFSXIBU DJSDVNTUBODFT 26*$NBZCFTBGFMZVTFE BOEEFTDSJCJOH EFQMPZNFOUBOENBOBHFBCJMJUZJNQMJDBUJPOTPGUIFQSPUPDPM