[네트워크] 22. 다음 세대 IP(Next Generation IP)

IPv6 Addressing

• The main reason for migration from IPv4 to IPv6 is the small size of the address space in IPv4
• An IPv6 address is 128 bits or 16 bytes (octets) long, four times the address length in IPv4
  • 2³² -> 2¹²⁸

IPv6: Address Space

• The address space of IPv6 contains 2¹²⁸ addresses.
• This address space is 2⁹⁶ times the IPv4 address—definitely no address depletion—as shown, the size of the space is

Global Unicast Address

• 2000::/3 → three leftmost bits (001), Size of this block 2¹²⁵

전 세계 단말들과 통신

n: 48 (3 + 45) -> 앞에 3bit는 빼야하니까 사실상 45bit

m: 16

q: 64

로 권장됨

 

Mapping EUI-64 and Ethernet MAC

Special Addresses

• 0000::/8

IPv4와 주소 변환을 위해서 쓰는 주소

 

Other Assigned Blocks

Autoconfiguration and Renumbering

• Dynamic Host Configuration Protocol, DHCP, can be used to allocate an IPv4 address to a host that joins the network.
  • In IPv6, DHCP protocol can still be used to allocate an IPv6 address to a host, but a host can also configure itself.
  • host가 자기 자신을 configure(renumbering)
  • provider와 prefix 교환
• To allow sites to change the service provider, renumbering of the address prefix (n) was built into IPv6 addressing. If the site changes the provider, the address prefix needs to be changed. A router to which the site is connected can advertise a new prefix and let the site use the old prefix for a short time before disabling it. In other words, during the transition period, a site has two prefixes.

 

IPv6 Protocol

• Better header format, New options
• Allowance for extension, Support for resource allocation
• Support for more security

IPv4와 다르게 header length가 고정

Traffic class: 특급우편, 일반 우편(In IPv4, TOS와 유사한 것)

Flow label: 각 flow의 label을 붙임.

• resource allocation을 달리한다던가 서비스를 더 좋게.

hop limit: Time-to-Leave에 해당하던 것

 

IPv6 Packet Format

• Version, Traffic class, Flow label
• Payload length, Next header, Hop limit
• Source and destination addresses, Payload

Extension Header

Comparison between IPv4 and IPv6

ICMPv6 Protocol

• ICMPv6 is more complicated than ICMPv4

• 보조 protocol이 ICMPv6로 통합

 

 

ICMPv6 Messages

• Error-reporting messages
  • Four types of errors are handled
  • Destination unreachable, packet too big, time exceeded(hop limit), and parameter problems.
  • Source-quenched message, which is used to control congestion in version 4, is eliminated because the priority and flow label fields in IPv6 are supposed to take care of congestion.
• Information messages
  • Echo-request message and echo-reply message
• Neighbor-discovery messages
  • Router-solicitation message, router-advertisement message
  • Neighbor-solicitation message, neighbor-advertisement message
  • Redirection message, inverse-neighbor-solicitation message, inverse neighbor-advertisement message
• Group membership messages
  • Membership-query message and membership-report message

 

Transition from IPv4 to IPv6

• Dual Stack
  • 공존할 때 어떻게 통신할 것인지
  • 두 개의 스택을 가지고 운용

• Tunneling
  • 중간에 IPv4 header로 encapsulation시켜서 IPv4 지역을 지나갈 수 있도록 한다.
    • 도착할 때는 decapsulation

• Header translation

IPv6를 지원하지 않는 망에 가는 연결 시 router가 해석하여 mapping 시켜 보내 줌