Dr. Whai-En Chen. Institute of Computer Science and Information Engineering National Ilan University TEL: #340

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1 IPv6 Transition ( 轉移機制 ) Dr. Whai-En Chen Assistant Professor Institute of Computer Science and Information Engineering National Ilan University wechen@niu.edu.twedu TEL: #340

2 Outline Introduction Dual Stack Tunneling Manual Configuration 6to4 Tunnel (Automatic Tunneling) Tunnel Broker Teredo (NAT Traversal for IPv6 Tunnel) Translation Porting SIP User Agent to IPv6 BIS/BIA Mechanisms SIIT&NAT-PT 2

3 Outline Introduction Dual-stack Tunneling Translation 3

4 IPv4 to IPv6 Transition Strategy (RFC 2893) Dual Stack Reduce the cost invested in transition by running both IPv4/IPv6 protocols on the same machine. Tunneling Reduce the cost in wiring by re-using current IPv4 routing infrastructures as a virtual link. Translation Allow IPv6 realm to access the rich contents already developed on IPv4 applications Dual Stack NGTRANS Tunneling Translator 4

5 Transition Mechanisms 5

IPv6 轉移 Roadmap Roadmap ( 參考韓國發展現況 ) Transition Roadmap by Government (23 Feb 2001) Phase I (~2001) Phase II (2002~2005) Phase III (2006~2010) Phase IV (2011~) IPv4 Only IPv4 Ocean IPv4 Island

6 IPv6 轉移 Roadmap Roadmap ( 參考韓國發展現況 ) Transition Roadmap by Government (23 Feb 2001) Phase I (~2001) Phase II (2002~2005) Phase III (2006~2010) Phase IV (2011~) IPv4 Only IPv4 Ocean IPv4 Island IPv4/IPv6 Translation Required IPv6 Only Experimental IPv6 Network IPv6 Island IPv6 Ocean Validation Operation Promotion IMT2000 Service Translation Service Commercial IPv6 Service (wire/wireless) Complete native IPv6 6

7 我國 IPv6 位址分配現況 7

8 Outline Introduction Dual-stack Tunneling Translation 8

9 Dual Stack (RFC 2893) Dual-stack 應用層傳輸層 (TCP/UDP) IPv4 IPv6 Dual Stack 表示同時裝有 IPv4 與 IPv6 兩個通訊協定堆疊當兩台機器通訊時, 可以使用 IPv4 通訊, 或是 IPv6 通訊當 IPv6 已經廣泛地被使用時, 就可以移除 IPv4 通訊協定, 而全面使用 IPv6 協定網路介面層 9

10 Dual Stack Example Applications TCP/UDP Routing protocols IPV4 IPV6 TCP/UDP Device Driver IPV4 IPV6 Device Driver Host V4/V6 network Router V6 network V4 network 如果所有的機器都是 Dual Stack, 還需要其他的轉換機制嗎? 10

11 Outline Introduction Dual-stack Tunneling Manual Configuration 6to4 Tunnel (Automatic Tunneling) Tunnel Broker Teredo (NAT Traversal for IPv6 Tunnel) Translation 11

12 Tunnels es of IPv6 over IPv4 IPv6 Header Transport Header Data IPv6 Host IPv6 Network Dual-stack Router IPv4 Dual-stack Router IPv6 Network IPv6 Host IPv4 Header Tunnel: IPv6 in IPv4 packet IPv6 Header Transport Header Data Encapsulating the IPv6 packet in an IPv4 packet Tunneling can be used by routers and hosts 12

13 Manually Configured Tunnel Dual-Stack Router IPv4 Dual-Stack Host IPv4: IPv6: 2001:288:03a1:210::3/127 IPv4: IPv6: 2001:288:03a1:210::2/127 IPv6 Tunnel 的建立需要哪些參數? FreeBSD4.7# gifconfig gif ifconfig gif0 inet6 2001:288:03a1:210::2 2001:288:3a1:210::3 prefixlen

14 6to4 Tunnel (RFC 3056) IPv6 Network Network prefix: 2002:83F3:812C::/48 6to4 6to4 Router1 Router2 E0 IPv4 E0 IPv6 Network Network prefix: = = 2002:8C6E:C7FA::/48 6to4 Tunnel: Is an automatic tunnel method Gives a prefix to the attached IPv6 network 2002::/16 assigned to 6to4 Requires one global IPv4 address on each site router2# interface Ethernet0 ip address ipv6 address 2002:8C6E:C7FA:1::/64 eui-64 interface Tunnel0 no ip address ipv6 unnumbered Ethernet0 tunnel source Ethernet0 tunnel mode ipv6ip 6to4 ipv6 route 2002::/16 Tunnel0 14

15 6to4 Tunnel 2002:83F3:812C:1::3 IPv6 Network Network prefix: 2002:83F3:812C::/ :8C6E:C7FA:2::5 6to4 6to4 Router1 Router2 E0 IPv4 E0 IPv6 Network Network prefix: 2002:8C6E:C7FA::/48 IPv6 SRC 2002:83F3:812C:1::3 IPv6 DEST 2002:8C6E:C7FA:2::5 IPv4 SRC IPv4 DEST IPv6 SRC 2002:83F3:812C:1::3 IPv6 DEST 2002:8C6E:C7FA:2::5 IPv6 SRC 2002:83F3:812C:1::3 IPv6 DEST 2002:8C6E:C7FA:2::5 Data Data Data 15

16 IDC Tunnel Broker IPv4 網路 3 IPv6 網路 1 2 Tunnel Broker imac IPv6 通道 4 IPv6 伺服器 Tunnel Router/Server 1. User registers a new account and fill his public IPv4 address information. 2. Tunnel Broker assigns Client/Server IPv6 addresses and Tunnel Server s IPv4 address. 3. Tunnel Broker setup IPv6 tunnel to Tunnel Server. 4. Through h IPv6 tunnel, the host can communicate with IPv6 servers. 16

17 國內 Tunnel Broker 列表國立東華大學中研院計算中心中華電信研究所 HiNet * 注意 * 使用 IPv6 Tunnel Broker 一定要先有 Public IPv4 位址 17

18 18

19 CHTTL Tunnel Broker Service Step 1- 註冊新帳號 Step 2- 登入網頁 Step 3- 新增 Tunnel Step 4- 檢視 Tunnel Step 5- 刪除 Tunnel 19

20 註冊新帳號 20

21 登入網頁 (1) 21

22 登入網頁 (2) 22

23 新增 Tunnel 23

24 新增 Tunnel(1) 24

25 新增 Tunnel(2) 25

26 檢視 Tunnel 26

27 刪除 Tunnel 27

28 IPv6 Tunneling Problem over NAT It does not work when the IPv4 address is not globally routable B4 is a private address! A IPv6 host IPv6 site B IPv4 C IPv4 D IPv6 E 6to4 router NAT Address translation IPv4 D4 6to4 E6 IPv6 router B4 Relay A6 host router A to B: IPv6 Src: A6 Dest: E6 data Src: B4 Dest: D4 Src: A6 Dest: E6 Src: N4 Dest: D4 Src: A6 Dest: E6 Src: N4 Dest: D4 Src: A6 Dest: E6 Src: A6 Dest: E6 data D to E: IPv6 B to C: IPv4 (encapsulating IPv6) data data data C to D: IPv4 (encapsulating IPv6) A v6 IP: 2002:a02:3fe::2/48 (A6) B v6 IP: 2002:a02:3fe::1/48 (B6) B v4 IP: (B4) E v6 IP: 2001:238:f88:4::2/64 (E6) D v6 IP: 2001:238:f88:4::1/64 (D6) D v4 IP: (D4) NAT address: (N4)

29 Teredo edo Service To allow hosts behind NAT to access IPv6, without modifying NAT. Teredo is not a long-term solution If NAT also supports IPv6 routing, the problem of NAT traversal will disappear. 29

30 Teredo edo Definitions Teredo client A node wants to gain access to the IPv6 Internet. t Teredo server helper to provide IPv6 connectivity to Teredo clients. Teredo relay An IPv6 router that can receive traffic destined to Teredo clients and forward it to Teredo client. Teredo bubble minimal IPv6 packet, made of an IPv6 header and null payload, no Next Header. Teredo service The transmission of IPv6 packets over UDP. 30

31 Operation Model IPv6 A client has pre-configured server location. A client gets IPv6 prefix from the Teredo server. Teredo server IPv4 Teredo IPv6 prefix? IPv4 NAT Teredo client Teredo relay Tunnel Teredo IPv6 prefix, your mapped address Teredo server is stateless. Traffic goes directly between the relay router and the client. Teredo Relay announces reachability of Teredo prefix on IPv6 realm. Relay and Client maintain peer list to avoid sending Teredo message too often. 31

32 Teredo edo Address Encoding Prefix Server IPv4 Flags Port Client IPv4 Prefix: the 32 bit Teredo service prefix. 3FFE:831F::/32 Server IPv4: the IPv4 address of a Teredo server. Flags: a set of 16 bits that document type of address and NAT. 16 bits flag: C00000UG C=1 if NAT is cone. UG should set to 00. Port: the obfuscated "mapped UDP port" of the client Client IPv4: the obfuscated "mapped IPv4 address" of a client Obfuscated: XOR every bits in the field with 1, prevent over-genius NAT s translation. 32

33 Obtaining an Address(1/2) IPv6 Teredo server IPv4 NAT Teredo relay : IPv4 UDP IPv6 RS Teredo client sends a UDPv4 tunneled IPv6 Router Solicitation to the Teredo server. Teredo server replies UDPv4 tunneled IPv6 Router Advertisement with origin indication. IPv4 IPv4 UDP Origin indication IPv6 RA :1234 Teredo client Origin indication format 0x00 0x00 mapped port # mapped IPv4 address 33

34 Obtaining an Address(2/2) Client get Teredo service prefix 3FFE:831F::/32 (PREF= 3FFE:831F) Client get mapped address/port from origin indication Mapped address: :4096 Generated Teredo IPv6 address 3FFE:831F:102:304::EFFF:F6FF:FFFE Already known server IP: Address and port are obfuscated. Must keep alive address mapping on NAT Default refresh interval: 30 seconds. 34

35 Packet from Teredo Node to IPv6 Node (1/3) A does not know which relay will IPv6 B 2000::B be chosen by B. Teredo Teredo A sends ICMPv6 echo request" Server Relay toward B. S R S forwards echo request to :3544 IPv6 realm. IPv :3544 IPv4 NAT : Src. Dest. IPv6 Src. IPv6 Dest : :3544 PREF:102:304::EF 2000::B FF:F6FF:FFFE 10002: :1234 Teredo Client A PREF:102:304::EFFF:F6FF:FFFE PREF:102:304::EF FF:F6FF:FFFE 2000::B 35

36 Packet from Teredo Node to IPv6 Node (2/3) IPv6 B sends the echo reply B 2000::B back to Teredo Client. The IPv6 packet will be S R queued by Teredo Relay :3544 IPv :3544 If Teredo edo Client is behind a restricted NAT, a :4096 bubble must be sent to NAT Teredo Server. IPv IPv6 Src. IPv6 Dest. 2000::B PREF:102:304::E FFF:F6FF:FFFE :1234 A PREF:102:304::EFFF:F6FF:FFFE 36

37 Packet from Teredo Node to IPv6 Node (3/3) IPv6 B 2000::B S R :3544 IPv : :4096 NAT IPv4 R sends the queued echo reply to A. A knows B can be reached through address :3544. A will send all further packets directly through R :1234 Teredo Client A PREF:102:304::EFFF:F6FF:FFFE 37

38 Outline Introduction Dual-stack Tunneling Translation Porting SIP User Agent to IPv6 BIS/BIA Mechanisms SIIT&NAT-PT 38

39 提供轉換 IPv4 程式到 IPv6 之方法介紹 IPv4 與 IPv6 之長度不同介紹為何需要改變應用程式介紹不用轉換的 Socket API 介紹需要轉換的 Socket API 介紹需要轉換的資料結構 39

40 為何需要轉換應用程式 New Solutions for Applications IPv4 AP IPv6 AP V4/v6 Protocol-independent Application TCP/UDP TCP/UDPv6 TCP/UDP TCP/UDPv6 IPv4 IPv6 IPv4 IPv6 Layer 1 and 2 Layer 1 and 2 40

41 不需要轉換的 Socket API ( 依序 ) Server 端的程式碼 socket open a socket bind bind local address to the socket listen listen on a port accept wait for the connection read/write if TCP recvfrom/sendto if UDP Client 端的程式碼 socket open a socket connect connect to a server read/write if TCP recvfrom/sendto if UDP 41

42 轉換需要改變的部分與 IP 位址相關的 Socket API 與參數需要修改程式部分有運用到 IP 位址的部分位址轉換函式位址複製函式位址比較函式位址相關之記憶體指派與變數宣告 IPv4 程式設計者的自訂的函式與變數也需要修改 42

43 API 與資料結構的轉換 Socket 參數名稱轉換 IPv4 IPv6 AF_INET AF_INET6 PF_INET PF_INET6 IN_ADDR_ANY inaddr6_any 43

44 API 與資料結構的轉換資料結構轉換 IPv4 in_addr IPv6 in6_addr sockaddr sockaddr_in6 sockaddr_in sockaddr_in6 44

45 API 與資料結構的轉換資料結構參數轉換 IPv4 sin_len sin_family sin_port sin_addr IPv6 sin6_len sin6_family sin6_port sin6_addr s_addr s6_addr 45

46 API 與資料結構的轉換函式轉換 Name-to_address Functions Address conversion Functions IPv4 inet_aton() inet_addr() inet_ntoa() gethostbyname() gethostbyaddr() IPv6 inet_pton() inet_ntop() getipnodebyname() getipnodebyaddr() getnameinfo() getaddrinfo() 46

47 IPv6 SIP-based User Agent 軟硬體需求軟體需求 Windows 2000/XP/2003 IPv6 Protocol Stack (Win2000 需 Patch) SIPv6 User Agent 硬體需求 Pentium III 1.3G 以上 CPU USB Camera ( 網路攝影機 ) 耳機麥克風 IPv6 網路連線 47

48 啟動 SIPv6 User Agent 2 Click right botton 1 Double-click 4 Next Page 3 48

49 設定 SIPv6 User Agent 的 IPv6 位址 1 1. 選擇 User Settings 分頁 2. 在 User IP Address 選項中, 選擇 Global Unicast IPv6 Address ( 如 :2001:238:f88:131:2e0:18ff:feea:f782) 3. 如果要跨越 IPv4 網路, 則需要選擇 6to4 位址 (Prefix 是 2002::/16) 2 3 Next Page 49

50 設定 SIPv6 User Agent 的伺服器選擇 Server Settings 分頁 2. 取消 Use Proxy 選項 3. 取消 Registration ; 若是有 IPv6 SIP 伺服器, 則可以選取選項, 並填入伺服器的 IPv6 位址 3 4 Next Page 50

51 設定 SIPv6 User Agent 的 Codec 參數選擇 Codec Settings 分頁 2. 將要用的 Codec 放入 Active Codecs 選項中 3. 選取 Use Video, 若不需要影像則可以取消此選項 4. 按下確定按鈕, 完成設定 4 Next Page 3 51

52 開始撥號 ( 輸入 SIP URI) 1. 按下圖中按鈕 2. 可以直接輸入 SIP URI ( 如 :SIP:7221@3ffe:3600:1::1) 3. 或是可以按下 List 按鈕, 從選單中選取 4-6. 按下 Load 按鈕, 選取 SIP URI, 按下 OK 完成 Next Page

53 撥號與接聽 1 2 發話方受話方 1. 按下 Dial 按鈕, 開始撥號 2. 受話方案下圖中電話筒圖案即可接聽 53

54 研發分組 IPv6 第四層以上協定分析計畫展示項目 - SIPv6 User Agent (UA) 移植成果 Using IPv6 Addresses 4. 通訊影像 SIPv6 UA 1. 設定 4. RTP 4. 通訊影像 3.1 INVITE OK 3.7 ACK IPv6 Network (Showroom) 2. 撥號 Dual-stack Router Tunneling 3.2 INVITE OK 3.8 ACK 4. RTP 圖例 : Internet (IPv4) SIP Signaling (IPv6) SIP Signaling (Tunnel) Dual-stack Router 3.3 INVITE OK 3.9 ACK IPv6 Network SIPv6 UA 4. RTP (NCTU VoIP Lab)

55 設計主機端轉換之中介軟體可是要將應用程式升級成 IPv6 會有以下問題需要改用新的 API 需要改用新的 Data structure 以 SIP-based VoIP User Agent 為例約有 200 行 Socket API 資料結構需要轉換共約有 600 行位址相關函式變數記憶體指派需要修改短期內將程式升級 IPv6 不容易需要改的函式變數需要追蹤修訂程式版本升級時, 亦需隨之修訂提出一個轉換 v4/v6 的中介軟體, 以 BIA 為基礎, 設計應用層轉換機制 (Socket-layer Translator) 55

56 Address Translations a s Bump-In-the-Stack Bump-In-the-Application ti 56

57 Key Components for BIS/BIA BIS or BIA Functions Extension Name Resolver Address Mapper Translator (Function Mapper) Translation Middleware 57

58 Address Translation Example: Originator Dual Stack Host6 DNS IPv4 app. Extension Name Resolver Address Mapper Translator IPv6 Resolve an IPv4 address for host6 Query A Query A and AAAA for host6 Reply only with AAAA Request one IPv4 address (internal IPv4 address allocation) Reply with the IPv4 address Reply with the A record Send an IPv4 packet to Host6 Translate IPv4 to IPv6 An IPv6 Packet An IPv6 packet ( Reply) An IPv4 packet Request IPv6 address Reply with the IPv6 address Request IPv4 address Reply with the IPv4 address Translate IPv6 into IPv4 An IPv4 packet Translation (v4->v6) Translation (v6->v4) 58

59 Address Translation Example: Recipient Dual Stack Host6 IPv4 Extension app. Address Name Mapper Resolver Translator IPv6 Receive a data from host6 An IPv6 packet Request IPv4 address from table Reply with the IPv4 address Translate IPv6 to IPv4 header An IPv4 packet Translation (v6->v4) Reply pyan IPv4 data to host6 An IPv4 reply packet Request IPv6 address from table Reply with the IPv6 address Translation (v4->v6) Translate v4 packet to v6 An IPv6 packet 59

IPv6 and IPv4 Translator Architecture (NAT-PT with DNS-ALG) RFC 2766 IPv6 網路與 IPv4 網路之間的通訊 DNS1 DNS 3ffe:3600:1::2 IPv6 Network DNS-ALG Translator 140.113.87.

60 IPv6 and IPv4 Translator Architecture (NAT-PT with DNS-ALG) RFC 2766 IPv6 網路與 IPv4 網路之間的通訊 DNS1 DNS 3ffe:3600:1::2 IPv6 Network DNS-ALG Translator DNS2 DNS IPv4 Network UA1 The NAT-PT translator configuration UA2 3ffe:3600:1::3 Address Pool: ua1.ipv6.nctu.edu.tw NAT-PT Prefix: 3ffe:3600:2::/96 ua2.ipv4.nctu.edu.tw 60

61 SIIT (Stateless IP/ICMP Translation) RFC

62 Translating sa from IPv4 to IPv6 IPv6 Header IPv4 Header Transport Layer Header Data Fragment Header (If Present) Transport Layer Header Data 62

63 Translating IPv4 Headers into IPv6 Headers - If IPv4 DF is set. IPv6 Header Fields Value Version 6 Traffic Class 0 Flow Label 0 Payload Length Next Header IPv4 Total length IPv4 IHL IPv4 Protocol field Hop Limit IPv4 TTL - 1 Source Address Destination Address High-order 96 bits = IPv6 prefix Low-order order 32 bits = IPv4 source address IPv6 in NAT-PT Mapping table 63

64 Translating IPv4 Headers into IPv6 Headers - If IPv4 DF is set. IPv4 Header Version IHL [4] TOS [8] Total Length [16] Identification [16] 0 DFMF Fragment Offset [13] TTL [8] Protocol [8] Header Checksum [16] Source Address [32] Destination Address [32] Version Traffic Class [8] Flow Label [20] Payload Length [16] Next Header [8] Max. Hop [8] IPv6 Header Source Address [128] Destination Address [128] 64

65 Translating IPv4 Headers into IPv6 Headers - If IPv4 DF is not set. IPv6 Header Fields Payload Length Next Header Value IPv4 Total length IPv4 IHL + 8 (Fragment Header) Fragment Header Fragment Header Next Header Fragment Offset Value IPv4 Protocol field IPv4 Fragment Offset field M Flag IPv4 More Fragment(MF) bit Identification High-order 16 bits = 0 Low-order 16 bits = IPv4 Identification 65

66 Translating IPv4 Headers into IPv6 Headers - If IPv4 DF is not set. IPv4 Header Version IHL [4] TOS [8] Total Length [16] Identification [16] 0 DFMF Fragment Offset [13] TTL [8] Protocol [8] Header Checksum [16] Source Address [32] Destination Address [32] Version Traffic Class [8] Payload Length [16] Flow Label [20] Next Header [8] Max. Hop [8] IPv6 Header Source Address [128] Destination Address [128] Fragment Header Next Header [8] Res. [8] Fragment Offset [13] Res. MF Identification [32] 66

67 Translating ICMPv4 Headers into ICMPv6 Headers - ICMP Query Message ICMP Header Type [8] Code [8] Checksum [16] Message Body [32] : ICMPv4(Type) ICMPv6(Type) Echo Request(8) / Reply(0) Type = 128/129 Information Request(15) / Reply(16) Timestamp Request(13) / Reply(14) Address Mask Request(17)/ Reply(18) Silently drop (Undefine) Silently drop (Undefine) Silently drop (Undefine) ICMP Router Adver.(9) Silently drop (Single Hop) ICMP Router Solicit.(10) Unknown ICMP4 types Silently drop (Single Hop) Silently drop 67

68 Translating ICMPv4 Headers into ICMPv6 Headers - ICMP Error Message ICMPv4(Type) Code ICMPv6 3 (Destination Unreachable) 0/1 Type = 1, Code = 0 (no route to destination) 2 Type = 4, Code = 1, Pointer to 6NexHead 3 Type = 1, Code = 4 (port unreachable) 4 Type = 2, Code = 0 (Packet too Big) 5 Type = 1, Code = 0 6/7/8 Type = 1, Code = 0 9/10 Type = 1, Code = 1 (Administratively Prohibited) 11/12 Type = 1, Code = 0 5 (Redicrect) Silently drop (Single Hop) 4(S (Source Quench) Silently drop (Obsoleted in ICMPv6) 11 (Time Exceed) 0/1 Type = 3, Code=0/1 12 (Parameter Problem) 0 Type = 4, Code=0, Pointer to the correspon. Field Unknow error message Silently drop 68

69 Translating sa from IPv6 to IPv4 IPv6 Header Fragment Header (If Present) Transport Layer Header Data IPv4 Header Transport Layer Header Data 69

70 Translating IPv6 Headers into IPv4 Headers - If there is no IPv6 Fragment header. IPv4 Header Fields Version 4 Internet H. L. ToS and Precedence 0 Total Length Identification 0 Value 5 (no IPv4 option) Payload Length + IPv4 IHL Flags MF = 0, DF = 1 Fragment Offset 0 Time to Live IPv6 Hop Limit 1 Protocol Header Checksum Source Address Destination Address IPv6 Next Header Recompute IPv4 in NAT-PT Mapping table Destination address of IPv6 Low-order 32 bits 70

71 Translating IPv6 Headers into IPv4 Headers - If there is a IPv6 Fragment header. IPv4 Header Fields Value Total Length Payload Length - IPv4 IHL + 8(Fragment header) Identification Identification in Fragment header Flags MF = M in the Fragment header, DF = 1 Fragment Offset Fragment Offset in Fragment header Protocol Next Header in Fragment header 71

72 Translating ICMPv6 Headers into ICMPv4 Headers - ICMPv6 Query Message ICMPv6(Type) ICMPv4(Type) Echo Request(128) / Reply(129) Type = 8/0 MLD Multicast Listener Query/Report/Done (130/131/132) Neighbor Discover messages ( ) Unknown ICMP6 types Silently drop (Single Hop & Undefine) Silently drop (Single Hop) Silently drop 72

73 Translating ICMPv6 Headers into ICMPv4 Headers - ICMPv6 Error Message ICMPv6(Type) Code ICMPv4 1 (Destination Unreachable) 0 Type = 3, Code = 1 (host unreachable) 1 Type = 3, Code = 10 (Admin. Prohibited) 2 Type = 3, Code = 1 (host unreachable) 3 Type = 3, Code = 1 (host unreachable) 4 Type = 3, Code = 3 (port unreachable) 2 (Packet Too Big) 0 Type = 3, Code = 4 (fragmentation needed) 3 (Time Exceeded) 0/1 Type = 11, Code = 0/1 11 (Parameter Problem) 1 Type = 3, Code = 2 (protocol unreachable) other Type =12, Code = 0 Unknown error message Silently drop 73

74 Checksum Modification Internet checksum use 16-bits 1 s complement checksum 2ki kinds of policy Re-Compute Algorithm Adjustment Algorithm Case Policy IPv6 Header IPv4 Header Re-Compute Algorithm ICMPv6 Header ICMPv4 Header TCP UDP Adjustment Algorithm Adjustment Algorithm Adjustment Algorithm 74

75 NAT-PT operations with DNS-ALG (IPv6 IPv4) IPv4) IPv6 Network IPv4 Network DNS-ALG UA1 DNS1 + DNS2 UA2 NAT-PT DNS Query (AAAA) DNS Query (AAAA) DNS Query (A) 1.4 DNS Response (A) DNS Response (AAAA) DNS Response (AAAA) 1.9 ICMPv6 Message (MAC Address Query) 1.10 ICMPv6 Message (MAC Address Response) 1.11 IPv6 Packet 1.12 ARP Message (MAC Address Query) ARP Message (MAC Address Response) IPv4 Packet 75

76 NAT-PT operations with DNS-ALG (IPv4 IPv6) IPv6) UA1 IPv6 Network DNS1 IPv4 Network DNS-ALG + NAT-PT DNS2 UA2 DNS Query (A) 2.2 DNS Query (A) DNS Query (AAAA) 2.5 DNS Response (AAAA) DNS Response (A) DNS Response (A) ARP Message (MAC Address Query) ARP Message (MAC Address Response) ICMPv6 Message (MAC Address Query) IPv4 Packet ICMPv6 Message (MAC Address Response) 2.14 IPv6 Packet 76

77 Q&A 要連上 IPv6 網站, 你需要哪些配備? 有哪些 Tunnel 機制? 在什麼情況下會用到這些機制? 要設定一個主機端的 Tunnel, 需要哪些參數? NAT-PT 轉換器可能在什麼情況下會用到? BIS/BIA 在什麼狀況下會用到? 如何撰寫 IPv4/IPv6 通用的網路應用程式? 77

港專單一登入系統 (SSO) 讓本校的同學, 全日制及兼職老師只要一個登入帳戶, 便可同時使用由本校提供的網上系統及服務, 包括 Blackboard 網上學習平台, 港專電郵服務, 圖書館電子資料庫及其他教學行政系統.

港專單一登入系統 (SSO) 讓本校的同學, 全日制及兼職老師只要一個登入帳戶, 便可同時使用由本校提供的網上系統及服務, 包括 Blackboard 網上學習平台, 港專電郵服務, 圖書館電子資料庫及其他教學行政系統. 港專單一登入網站網址 http://portal.hkct.edu.hk (HKCT 之教職員, 學生 ) http://portal.ctihe.edu.hk (CTIHE 之教職員,