2. 1 Chapter 2 The Architecture of Networks Organizing with Layers and Hierarchies Layers organize effort-divide and conquer

3. 2 第N層第N層 第 N-1 層 第1層第1層 傳輸介質 Chapter 2 The Architecture of Networks Organizing with Layers and Hierarchies 對等協定 (Peer Protocol)

4. 3 Chapter 2 The Architecture of Networks Organizing with Layers and Hierarchies FTP TCP IP Encapsulation and Decapsulation

5. 4 Chapter 2 The Architecture of Networks Organizing with Layers and Hierarchies Hierarchies organize information and delegate responsibility

6. 5 Chapter 2 The Architecture of Networks Organizing with Layers and Hierarchies Layering Advantages : Isolating the various services from one another Flexibility (changing from cable to fiber without your knowing) Hierarchies Advantages: Organize information and delegate responsibility

7. 6 ISO OSI 的 參考模 型 應用層 表達層 交談層 傳輸層 網路層 資料連結層 實體層 應用層 表達層 交談層 傳輸層 網路層 資料連結層 實體層 傳輸介質 application presentation session transport network data link physical Chapter 2 The Architecture of Networks Layers different communication protocols Hierarchies Internet naturally organizes its components into hierarchies

8. 7 Chapter 2 The Architecture of Networks Two distinct roles for Internet Host and Router The TCP/IP Internet: TCP/IP Protocols TCP/IP Layering

9. 8 Chapter 2 The Architecture of Networks The TCP/IP Internet: Links, Subnetworks, and Internets Network: has a completely routing ability Internet: join several network (herein define subnetwork) together

10. 9 Chapter 2 The Architecture of Networks The TCP/IP Internet: Hosts: send or receive messages Routers: relay messages across networks

11. 10 Chapter 2 The Architecture of Networks The TCP/IP Internet: Hosts and Routers (protocol stacks)

12. 11 Chapter 2 The Architecture of Networks The TCP/IP Internet: Internet Hierarchy Site: collection of networks, controlled by a single administrator

13. 12 Chapter 2 The Architecture of Networks Communication Services: Connectionless Delivery

14. 13 Chapter 2 The Architecture of Networks Communication Services: Connectionless Delivery

15. 14 Chapter 2 The Architecture of Networks Communication Services: Connection-Oriented Delivery

16. 15 Chapter 2 The Architecture of Networks Communication Services: Connection-Oriented Delivery

17. 16 Chapter 2 The Architecture of Networks Communication Services: Combining Services (TCP, CO) (IP, CL) (TCP, CO)

18. 17 Chapter 2 The Architecture of Networks Network Addressing Internet Protocol software must hide the details of physical networks and offer the facilities of a large virtual network (hide the differential network technology). The Internet designers are free to choose addresses, packet formats, and delivery techniques independent of the details of the physical hardware. Addressing is a critical component of the Internet abstract. To give the appearance of a single, uniform system, all host computers must use a uniform addressing scheme.

19. 18 Chapter 2 The Architecture of Networks Network Addressing: The role of network addresses IP addresses do not specify an individual computer, but a connection to a network. TCP/IP addresses identify interfaces, not systems Multi-home host: more than one network interface, each interface requires one network address

20. 19 Chapter 2 The Architecture of Networks Network Addressing: Type of Addresses Unicast, Muticast, Anycast

21. 20 Chapter 2 The Architecture of Networks Network Addressing: Type of Addresses Unicast, Muticast, Anycast (compromise between unicast and multicast) Anycast address refers to any one of interfaces, not all of them Ex: router recognizes that the message has already reached at least one appropriate interface

22. 21 §IP denoted - in the form each number represents, in decimal, 1 byte of the 4-byte IP address. §Why are IP addresses necessary? l Easy to find the destination station l IP addresses are hierarchical addresses Every IP address has two parts. –network number (provided by InterNIC) –host number (provided by local administrator) l Where to find the IP address International Network Information Center, or InterNIC l There are five classes of Network (Five type IP) only three of these are used commercially. These are the class "A," "B," and "C" networks the class “D” is reserved for multicast the class “E” is reserved for experiment/research Network Addressing: IPv4 address format (32-bit address)

23. 22 Chapter 2 The Architecture of Networks Network Addressing: IPv4 address format (32-bit address) 投影片 26 class A07-bit netid24-bit hostid class B1 016-bit hostid class C1 1 08-bit hostid 14-bit netid 21-bit netid class D1 1 1 0 28-bit multicast group ID class E1 1 1 1 0 reserved for future use Note that the IP address has been defined in such a way that it is possible to extract the hostid or netid portions quickly. Routers, which use the netid portion when deciding where to send a packet, depend on efficient extraction to achieve high speed. 0 ~ 127 128 ~ 191 192 ~ 223 224 ~ 239 240 ~ 255

24. 23 §What IP addresses are reserved for the Networks? l Network address : all host address are set to zero l Broadcase address : all host address are set to one §Question: What would the network/broadcase address be for devices such as the one with an IP address of 197.22.103.221? §In order to provide extra flexibility for the network administrator, often networks, particularly large networks, are divided into smaller networks called subnetworks. Most of the time subnetworks are simply referred to as subnets. §Who assigns subnet addresses? l this is done by the network administrator

25. 24 Chapter 2 The Architecture of Networks Network Addressing: IPv4 address format (32-bit address) IPv4 address weakness: The most obvious disadvantage is that addresses refer to network connections, not to host computer: If a host computer moves from one network to another, its IP address must change. Inconvenient for mobile computers Another weakness: Class C is too small while class B is too large.

26. 25 Chapter 2 The Architecture of Networks Network Addressing: IPv4 address format (32-bit address) Typical Routing Table Format (Router A) Destination-Network Next Hop Mask 100.203.10.x 100.204.10.1 255.255.255.0 Router ARouter 100.204.10.1 100.203.10.1 What is NetMask?

27. 26 Chapter 2 The Architecture of Networks Network Addressing: IPv4 address format (32-bit address) Network Mask Subnetting: Subdivide the host-id field in IP address divide class C into subnets of power of 2 for example: assign 192.100.100.0~63, 64~127, 128~191, 192~255 to four subnets. We can have a mask of 255.255.255.192 Supernetting: Assign class C in chunks of power of 2 (supernet). For example, Assign 203.64.0.* ~ 203.64.3.* to one organization. Then we can have a mask of 255.255.252.0. Classless Inter Domain Routing (CIDR)

28. 27 Chapter 2 The Architecture of Networks Network Addressing: IPv4 address format (32-bit address) IPv4 address weakness: Another problem: RAB Network 1 Network 2 The usual A to B path I When link I fails, we have one address that can be used to reach B and another that can't. Routing table only records one path. It may take a long time to find out the other path.

29. 28 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Text Representation of Addresses There are three conventional forms for representing IPv6 addresses as text strings: 1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the hexadecimal values of the eight 16-bit pieces of the address. Examples: FEDC:BA98:7654:3210:FEDC:BA98:7654:3210 1080:0:0:0:8:800:200C:417A

30. 29 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Text Representation of Addresses 2. Due to the method of allocating certain styles of IPv6 addresses, it will be common for addresses to contain long strings of zero bits. In order to make writing addresses containing zero bits easier a special syntax is available to compress the zeros. The use of "::" indicates multiple groups of 16-bits of zeros. The "::" can only appear once in an address. The "::" can also be used to compress the leading and/or trailing zeros in an address.

31. 30 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) For example the following addresses: 1080:0:0:0:8:800:200C:417A 1080::8:800:200c:417A FF01:0:0:0:0:0:0:43 FF01::43 0:0:0:0:0:0:0:1 ::1 (Loopback address) 0:0:0:0:0:0:0:0 :: (unspecified address) Text Representation of Addresses

32. 31 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Text Representation of Addresses 3. An alternative form that is sometimes more convenient when dealing with a mixed environment of IPv4 and IPv6 nodes is x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of the six high-order 16-bit pieces of the address, and the 'd's are the decimal values of the four low-order 8-bit pieces of the address (standard IPv4 representation). For example, 0:0:0:0:0:0:13.1.68.3 in compressed form is ::13.1.68.3

33. 32 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Hierarchy: solve the routing table explosion Different level only lookup the associated level information 3+5+16+16+8+32=80 The remaining 48 bits define the particular system on the subnetwork.

34. 33 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Address Prefixes An address prefix indicates both an address itself, and the number of significant bits in the addresses.

35. 34 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv6 Address Allocation – Special Addresses Allocation Prefix Fraction of (binary) Address Space ------------------------------- -------- ------------- Reserved hierarchy 0000 0000 1/256 (0::/8) Unassigned 0000 0001 1/256 (100::/8) Reserved for NSAP Allocation 0000 001 1/128 (200::/7) Reserved for IPX Allocation 0000 010 1/128 (400::/7) Unassigned 0000 011 1/128 (600::/7) Unassigned 0000 1 1/32 (800::/5) Unassigned 0001 1/16 (1000:/4)

36. 35 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv6 Address Allocation Allocation Prefix Fraction of (binary) Address Space ------------------------------- -------- ------------- Aggregatable Global Unicast Addresses 001 1/8 (2000::/3) Unassigned 010 1/8 (4000::/3) Unassigned 011 1/8 (6000::/3) Unassigned 100 1/8 (8000::/3) Unassigned 101 1/8 (A000::/3) Unassigned 110 1/8 (C000::/3) Unassigned 1110 1/16 (E000::/4)

37. 36 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv6 Address Allocation Allocation Prefix Fraction of (binary) Address Space ------------------------------- -------- ------------- Unassigned 1111 0 1/32 (F000::/5) Unassigned 1111 10 1/64 (F800::/6) Unassigned 1111 110 1/128 (FC00::/7) Unassigned 1111 1110 0 1/512 (FE00::/9) Link Local Unicast Addresses 1111 1110 10 1/1024 (FE80::/10) Site Local Unicast Addresses 1111 1110 11 1/1024 (FEC0::/10) Multicast Addresses 1111 1111 1/256 (FF00::/8)

38. 37 IPv6 Address Allocation – Special Addresses 0:0:0:0:0:0:0:0 unspecified address (never appear in the destination field) 0:0:0:0:0:0:0:1 loopback address Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address)

39. 38 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Two types of IPv6 addresses support the transition from IPv4. IPv4-compatible and IPv4-mapped IPv4-compatible IPv6 Addresses The IPv6 transition mechanisms include a technique for hosts and routers to dynamically tunnel IPv6 packets over IPv4 routing infrastructure. Router at the boundary of the IPv4 network can convert those address to true IPv4 addresses IPv6 nodes that utilize this technique are assigned special IPv6 unicast addresses that carry an IPv4 address in the low-order 32-bits. This type of address is termed an "IPv4- compatible IPv6 address" and has the format: 96 bits |0000..............................00000000| IPv4 address |

40. 39 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv4-compatible IPv6 Addresses

41. 40 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv4-mapped IPv6 address IPv4-mapped addresses indicate systems that do not support IPv6. They are instead limited to IPv4. As long as intervening routers perform the mapping, these addresses let IPv6 systems communicate with IPv4-only systems The format is 80 bits of zero, 16 bits of one, and 32 bits of an IPv4 address. Ex: IPv4: 4.3.2.1, IPv4-mapped: ::FFFF:0403:0201

42. 41 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) IPv4-mapped IPv6 address

43. 42 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) The structure of both IPv4-compatible and IPv4-mapped addresses is not arbitrary. Both formats were chosen because of the particular checksum algorithm that many TCP/IP protocols use. (for pseudo header) Either address format contributes the same value to the checksum, whether it is specified as an IPv6 addresses or as an IPv4 address.

44. 43 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Anycast Address (the subnet-router address)

45. 44 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Multicast Address: begin with eight bits of 1, the next eight bits give more information about the address (so far, only the fourth bit ha a defined meaning) T=0: a global authority has permanently assigned the address to a particular group. Ex: FF02::1 identifies the group of all systems on a link

46. 45 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Multicast Address

47. 46 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Multicast Address

48. 47 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Multicast Address

49. 48 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Multicast Address Standard identified five permanently assigned address FF01::1 all systems node-local scope FF02::1 all systems link-local scope FF01::2 all routers node-local scope FF02::2 all routers link-local scope FF05::2 all routers site-local scope

50. 49 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Solicited node address (one of multicast address) Every unicast (or anycast) address maps to exactly one solicited node address. Different unicast addresses may form the same solicited node address. TO create a solicited node address, a system takes the last 24-bits of its unicast or anycast address and appends them to the 104-bit prefix FE02::1:FF00/104. For example, a host with unicast address FEDC:BA98:7654:3210:FEDC:BA98:7654:3210 automatically belongs to the group of systems with multicast address FE02::1:FF54:3210. ICMP uses solicited node addresses to perform neighbor discovery and duplicate address detection.

51. 50 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Addresses that host must support

52. 51 Chapter 2 The Architecture of Networks Network Addressing: IPv6 address format (128-bit address) Addresses that router must support