zxing barcode scanner c# example Tunneling and Transition Mechanisms in Software

Draw QR Code 2d barcode in Software Tunneling and Transition Mechanisms

For an IPv6 host or network to operate on the Internet or other non-IPv6 domain, the IPv6 traffic uses the existing IPv4 infrastructure to transport packets using a technique known as tunneling Tunneling encapsulates IPv6 packets within IPv4 and, as such, the

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IPv6 application considers IPv4 as a data link layer within the network stack Tunneling examples that you may be familiar with include Layer 2 Tunneling Protocol (L2TP) for virtual private network (VPN) tunnels and IPSec The tunneling technologies used to bridge IPv6 to IPv4 are transition mechanisms They are how a network with IPv6 hosts communicates with backwards compatibility while other networks upgrade to IPv6 They are not meant to be permanent, but you can figure on them being around for a long time nonetheless Automatic Tunneling Tunnel endpoints are determined by IPv6 routers Three automatic tunneling options include 6to4, Teredo and ISATAP: 6to4 tunneling The recommended technique for automatic tunneling is 6to4 tunneling Tunnel endpoints are determined by using a well-known IPv4 anycast addresses on the remote side and embedding IPv4 address information within IPv6 addresses on the local side This type of tunneling is widely available in modern routing infrastructures Teredo This type of tunneling uses UDP encapsulation, which most NAT devices can forward IPv6 hosts behind NAT services can be used as Teredo tunnel endpoints even when they don't have a dedicated public IPv4 address Using Teredo, IPv6 hosts on separate IPv4 networks can communicate without any alteration to the routing infrastructure Though not yet widely available, Teredo is enabled by default in Vista, but is inactive NOTE Teredo was first released with the Advanced Networking Pack for Windows XP with Service Pack 1, and is also included with Windows XP Service Pack 2 and Windows Server 2003 Service Pack 1 Teredo IPv6 addresses are global in scope and unique within the Internet To activate it, simply use an application that requires it, or configure a rule in Windows Firewall to allow edge traversal Vista s implementation of Teredo includes the following characteristics: It is enabled for domain member computers, where Teredo for Windows XP and Windows Server 2003 automatically disabled itself if the computer was a member of a domain It can now work if there is one Teredo client behind one or more symmetric NATs A symmetric NAT maps the same private address to different public addresses, depending on the external destination address Teredo for Windows XP and Windows Server 2003 disables itself if it detects that it is behind a symmetric NAT This new behavior allows Teredo to work between a larger set of Internet-connected hosts

Intrasite Automatic Tunnel Addressing Protocol (ISATAP) ISATAP is defined in RFC 4214 Cisco and Microsoft are developing an implementation

of it at the time of this writing With ISATAP, IPv4 network hosts emulate a logical IPv6 subnet scheme This enables ISATAP nodes located on the IPv4 network to tunnel to each other with logical IPv6 connectivity through an ISATAP router IPv4 infrastructures can provide unicast IPv6 connectivity with the addition of an ISATAP router Configured Tunneling Configured tunneling is a technique whereby the tunnel endpoints are configured explicitly, either by a human operator or by an automatic service known as a tunnel broker A tunnel broker provides IPv6 tunnels to end users/end sites using manual, scripted, or automatic configuration Tunnel brokers offer protocol 41, or proto-41, tunnels, which encapsulate IPv6 inside IPv4 packets and update the IPv4 header The header s protocol field is set to 41, which is IPv6 NOTE Configured tunneling is usually more deterministic and easier to debug than automatic tunneling, and is, therefore, recommended for large, well-administered networks Configured tunneling typically uses a protocol 41 tunnel (recommended) or raw UDP encapsulation