Internet Protocol, Version 6

Transcription

1 Outline Protocol, Version 6 () Introduction to Header Format Addressing Model ICMPv6 Neighbor Discovery Transition from to vs. Taken from:chun-chuan Yang Basics: TCP/ Protocol Suite Protocol (IP) Features: Layer 3 (Network layer) Unreliable, Connectionless, Datagram Best-effort delivery Popular version: Major functions Global addressing Datagram lifetime Fragmentation & Reassembly

2 Header companion protocols (1) ARP: Address Resolution Protocol Mapping from IP address to MAC address ICMP: Control Message Protocol Error reporting & Query IGMP: Group Management Protocol Multicast member join/leave Unicast Routing Protocols (Intra-AS) Maintaining Unicast Routing Table E.g. RIP, OSPF (Open Shortest Path First) companion protocols (2) Multicast Routing Protocols Maintaining Multicast Routing Table E.g. DVMRP, MOSPF, CBT, PIM Exterior Routing Protocols (Inter- AS) E.g. BGP (Border Gateway Protocol) Quality-of-Service Frameworks Integrated Service (ISA, IntServ) Differentiated Service (DiffServ) Why? Address space exhaustion New types of service Multicast Quality of Service Security Mobility (M) Header and format limitations

3 Advantages of over Header: from to Larger address space Better header format New options Allowance for extension Support for resource allocation Support for more security Support for mobility Changed Removed Header Format Traffic Class The 8-bit field in the header is available for use by originating nodes and/or forwarding routers to identify and distinguish between different classes or priorities of packets. E.g., used as the codepoint in DiffServ General requirements Service interface must provide means for upper-layer protocol to supply the value of traffic class Value of traffic class can be changed by source, forwarder, receiver An upper-layer protocol should not assume the value of traffic class in a packet has not been changed.

4 Flow Label Related sequence of packets Needing special handling Identified by src & dest addr + flow label Router treats flow as sharing attributes E.g. path, resource allocation, discard requirements, accounting, security May treat flows differently Buffer sizes, different forwarding precedence, different quality of service Alternative to including all info. in every header Payload Length 16-bit unsigned integer. Length of the payload, i.e., the rest of the packet following this header, in octets. Note that any extension headers present are considered part of the payload, i.e., included in the length count. Packet (PDU) Structure Extension Header Order Order Header Type Next Header Code 1 Basic Header 2 Hop-by-Hop Options 0 4 Routing header 43 5 Fragment header 44 6 Authentication header 51 7 Encapsulation Security Payload header 50 8 Destination Options 60 9 Mobility header 135 No Next header (Null) 59 Upper layer: TCP, UDP, ICMP 6, 17, 58

5 Hop-by-Hop Options Routing Header Must be examined by every router Specifies discard/forward handling Options Pad Jumbo payload Router alert (can be used for RSVP) List of one or more intermediate nodes to visit Header includes Next Header Header extension length Routing type (e.g. type 0 = Source Routing) Segments left Source Routing Example Fragment Header (1) Fragment Offset The offset, in 8-octet units, of the data following this header, relative to the start of the Fragmentable Part of the original packet Unfragmentable part: header + any extension headers that must be processed by nodes en route

6 Fragment Header (2) M flag: 1=more fragments, 0=last fragment Identification: combined with the src & dest addr uniquely identifies the original packet Text Representation of Address Colon-Hex 3ffe:3600:2000:0800:0248:54ff:fe5c:8868 Compressed Format: 3ffe:0b00:0c18:0001:0000:0000:0000:0010 becomes 3ffe:b00:c18:1::10 Address Type Prefixes Global Unicast Address Global routing prefix A (typically hierarchically-structured) value assigned to a site (a cluster of subnets/links) Subnet ID An identifier of a subnet within the site Interface ID Constructed in Modified EUI -64 format EUI - Extended Unique Identifiers

7 IEEE 802 Interface ID Site-Local Address Meaningful only in a single site zone, and may be reused in other sites Equivalent to the private address space Address are not automatically configured and must be assigned Prefix= FEC0::/48 Now Deprecated! Unique-Local Addresses Unique Local Addresses Used for: Local Communications Inter-site VPN Non Routable Prefix=FC00::/7 Link-Local Address Meaningful only in a single link zone, and may be reused on other links Link-local addresses for use during autoconfiguration and when no routers are present Required for Neighbor Discovery process, always automatically configuration An router never forwards link-local traffic beyond the link Prefix= FE80::/64 27

8 Special Address Loopback address (0:0:0:0:0:0:0:1 or ::1) Identify a loopback interface -compatible address (0:0:0:0:0:0:w.c.x.z or ::w.c.x.z) Used by dual-stack nodes traffic is automatically encapsulated with an header and send to the destination using the infrastructure mapped address (0:0:0:0:0:FFFF:w.c.x.z or ::FFFF:w.c.x.z) Represent an -only node to an node Never used as a source or destination address of packet Rarely implemented Address Autoconfiguration (1) Allow plug and play BOOTP and DHCP are used in DHCPng will be used with Two Methods: Stateless and Stateful Stateless: A system uses link-local address as source and multicasts to "All routers on this link" Router replies and provides all the needed prefix info All prefixes have a associated lifetime Address Autoconfiguration (2) Network Layer in v4 & v6 Stateful: Problem w/ stateless: Anyone can connect Routers ask the new system to go DHCP server (by setting managed configuration bit) System multicasts to "All DHCP servers" DHCP server assigns an address

9 ICMPv6 ICMPv6 Messages An integral part of and MUST be fully implement by every node (RFC 2463) Next Header value= 58 Report delivery or forwarding errors Provide simple echo service for troubleshooting Neighbor Discovery (ND): 5 ICMP messages Multicast Listener Discovery (MLD): 3 ICMP messages Neighbor Discovery (ND) Node (Hosts and Routers) use ND to determinate the link-layer addresses for neighbors known to reside on attached links and quick purge cached valued that become invalid Hosts also use ND to find neighboring router that willing to forward packets on their behalf Replace ARP, ICMP Router Discovery, ND Mechanisms (1) Router discovery Equivalent to ICMPv4 Router Discovery Prefix discovery Equivalent to ICMPv4 Address Mask Request/Reply Parameter discovery Discovery additional parameter (ex. link MTU, default hop limit for outgoing packet) Address auto-configuration Configure IP address for interfaces Address resolution: Equivalent to ARP in

10 ND Mechanisms (2) Neighbor unreachable detection (NUD) Duplicate address detection (DAD) Determine that an address considered for use is not already in use by a neighboring node First-hop Redirect function Inform a host of a better first-hop address to reach a destination, Equivalent to ICMPv4 Redirect Advantages of over (1) Feature Source and destination address 32 bits 128 bits IPSec Optional required Payload ID for QoS in No identification Using Flow label field the header Fragmentation Both router and the sending hosts Only supported at the sending hosts Header checksum included Not included Resolve IP address to a link layer address broadcast ARP request Multicast Neighbor Solicitation message Advantages of over (2) Feature Determine the address of the best default gateway ICMP Router Discovery(optional) ICMPv6 Router Solicitation and Router Advertisement (required) Send traffic to all Broadcast Link-local scope allnodes on a subnet nodes multicast address Configure address Manually or DHCP Autoconfiguration Manage local subnet group membership (IGMP) Multicast Listener Discovery (MLD) RFC 2460: References RFC 2461: Neighbor Discovery RFC 2462: Stateless Address Autoconfiguration RFC 3513: Addressing Architecture RFC 3679: Flow Label Specification RFC 4443: ICMPv6 RFC 3810: Multicast Listener Discovery (MLDv2)

11 Transition from to Ingredients for Transition Dual Stack hosts application layer gateways routers Tunneling Configured addresses relay routers 42 Dual Stack Host A dual stack host implement both and ; it is configured with both an address and an address Web browser Application TCP TCP MAC Dual Stack Local router MAC B HTTP TCP A HTTP TCP Dual Stack Router A dual stack router implements both and It becomes a multiprotocol router One routing table for, one for Web browser Application TCP TCP MAC Dual Stack Local router MAC B HTTP TCP A HTTP TCP Uses DNS to know whether to use or send packets hostname2addr(af_inet6, hostname) returns address (read from AAAA record) if available, else mapped address read from A record 43 44

12 Tunneling Definition: carry an IP packet as payload inside an IP packet in packets (and vice versa) In an IPV4 packet, Protocol = 41 means the payload is an packet In principle, a tunnel needs to be configured, the encapsulator must be configured with the address of the decapsulator Works only for isolated cases IP4/6 Router Island Header Payload A Network Header da = Header Payload IP4/6 Router B Island Header Payload 45 Addresses Introduced to support automatic tunnels, i.e. without configuration of encapsulator/decapsulator pairs Definition: address To any valid address n we associate the prefix 2002:n / 48 example: the address prefix that corresponds to is 2002: 80b2:9c26 An address that starts with 2002: is called a address The bits 17 to 48 of a address are the corresponding address 2002::/16 is the prefix reserved for addresses A host or router is one that is dual stack and uses as address In addition, the address is reserved for use in the context of addresses (see next slides) Example of Use: Isolated Hosts host A Network 2 Relay router R host B Network 5 host C FEDC:BA98::7654:3210 back A s address is ; its address is 2002:0102:0304:0:EUI A where EUI is A s 64-bit MAC address B s address is ; its address is 2002:0908:0706:0:EUI B where EUI is B s 64-bit MAC address A sends packet to B s address Dest addr is, therefore A encapsulates, with decapsulator s address = that of B Packet sent at 1 has source = ; dest = ; protocol = source = 2002:0102:0304:0:EUI A dest =2002:0908:0706:0:EUI B Addresses Simplify Address Allocation Normally, an address is Provider allocated prefix + subnet + host part If your network is connected to the, you receive a provider allocated prefix Else, you use the address of an address given to you by your provider host A 2002:0102:0304: 00AB:EUI S12 11 Local Network :0102:0304: ABCD:EUI A router S 2 Relay router R host B 5 host C 2001:BA98::7654:3210

13 Relay Router and the Anycast Address R is a relay router : has interfaces and is both on the and internets All of R s interfaces on the internet have an address plus the address This is a reserved anycast address. It is a normal address, but there can be several machines with this same address, as there are several relay routers on the. host A 2002:0102:0304: 00AB:EUI S12 11 Local Network :0102:0304: ABCD:EUI A router S 2 Relay router R host B 5 host C 2001:BA98::7654:3210 host A Example 2 Relay router R host B 5 host C 2001:BA98::7654:3210 A sends packet to C C s address does not have same prefix as A ( destination not on link ), so A sends to a router R is a relay router A s default router entry is R; more precisely, it is 2002:c058:6301::0, which is a address corresponding to A builds an automatic tunnel with decapsulator = R host A 2002:0102:0304: :00AB:EUI S12 11 Local Network :0102:0304 : :ABCD:EUI A router S Local Network 2 Relay router R host B A has packet to send to C 5 host C 2001:0620:0: :00AB:EUIS12 Destination not on link, send to router in local router Default route inside local network is 2002:0102:0304::, i.e. the address of interface 1 of router S S builds a tunnel with decapsulator = relay router R Rest as before, i.e. S s default router entry is R; more precisely, it is 2002:c058:6301::0, which is a address corresponding to L. Hugues Reference The Second Reinventing Computer Networking with ond_internet.pdf 52