“ipv4 to ipv6 transition”

06/14/22 1 Babu Ram Dawadi @IOE Pulchowk Campus

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Transition Mechanisms Immediate migration to IPv6-only network is not possible IPv4 and IPv6 Coexists for long period of time. Some transition mechanisms have been standardized TUNNELING DUAL STACK & TRANSLATION (network address & protocol translation) Currently: IPv6 exists over IPv4 Islands Future: IPv4 exists over IPv6 Islands Finally IPv6-only Islands 4/26/2017


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Babu Ram Dawadi@IOE Pulchowk Campus

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Transition Mechanisms Immediate migration to IPv6-only network is not possible

IPv4 and IPv6 Coexists for long period of time.

Some transition mechanisms have been standardized TUNNELING DUAL STACK & TRANSLATION (network address & protocol translation)

Currently: IPv6 exists over IPv4 Islands

Future: IPv4 exists over IPv6 Islands

Finally IPv6-only Islands

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What is a tunnel? A tunnel identifies packets in a data stream

Identify by encapsulation (new header possibly new trailer)

Identify by labeling. Entry into a tunnel gives the data stream different

characteristicsE.g., Privacy, authentication, different routing

characteristicsSecurity is not always the goal of the tunnel

Also called virtual private networks (VPNs) in many situations

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TunnelingTunneling enables IPv6 hosts/routers to communicate with other IPv6

hosts/router over IPv4 network

Tunneling encapsulates IPv6 datagrams within IPv4 packets

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Tunneling…IPv4/IPv6 hosts and routers can tunnel IPv6 datagram

over regions of IPv4 routing topology by encapsulating them within IPv4 packets.

Tunneling techniques are classified by the way the encapsulating node determines the address of the node at the end of the tunnel:Host-to-hostHost-to-routerRouter-to-routerRouter-to-host

In router-to-router and host-to-router tunneling methods, the IPv6 packet is tunneled to a router

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IPv6 over IPv4 TunnelingThe IPv4 Protocol field is set to 41 to indicate an encapsulated IPv6

packet.The Source and Destination fields are set to IPv4 addresses of the tunnel

endpoints. The tunnel endpoints are either manually configured as part of the tunnel interface or are automatically derived from the next-hop address of the matching route for the destination and the tunneling interface.

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Host-to-Host In the host-to-host tunneling configuration, an IPv6/IPv4 node that resides

within an IPv4 infrastructure creates an IPv6 over IPv4 tunnel to reach another IPv6/IPv4 node that resides within the same IPv4 infrastructure.

IPv6/IPv4 hosts that use ISATAP addresses to tunnel across an organization’s IPv4 infrastructure.

IPv6/IPv4 hosts that use IPv4-compatible addresses to tunnel across an organization’s IPv4 infrastructure.

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Host-to-Router and Router-to-Host In the host-to-router tunneling configuration, an IPv6/IPv4 node that resides

within an IPv4 infrastructure creates an IPv6 over IPv4 tunnel to reach an IPv6/IPv4 router

In the router-to-host tunneling configuration, an IPv6/IPv4 router creates an IPv6 over IPv4 tunnel across an IPv4 infrastructure to reach an IPv6/IPv4 node

Figure below shows host-to-router (for traffic traveling from Node A to Node B) and router-to-host (for traffic traveling from Node B to Node A) tunneling.

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Router to Router Tunneling In the router-to-router tunneling configuration, two IPv6/IPv4 routers

connect two IPv6-capable infrastructures over an IPv4 infrastructureThe IPv6 over IPv4 tunnel between the two routers acts as a single hop.For each IPv6/IPv4 router, there is a tunnel interface representing the

IPv6 over IPv4 tunnel and routes that use the tunnel interface

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Tunneling (Contd…)Configured Tunneling

Tunnel end point address must be determined from configuration in the encapsulating node

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Automatic Tunneling Tunnel End Points address is determined by IPv4 compatible Destination

address (0::IPv4-address)

The packet being processed on the router will be redirected if the destination IPv6 address is an IPv4 compatible address and automatic tunneling is then used

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Automatic TunnelingThe nodes performing automatic tunneling are assigned an

IPv4 compatible address. This sort of address is identified by a 96 bit prefix consisting

only of zeros and an IPv4 address in the low-order 32 bits

IPv4 Compatible IPv6 Address FormatWhen the packet is being processed in the router, it is redirected if the

destination IPv6 address is an IPv4 compatible address, and automatic tunneling is then used

If the destination address is a native IPv6 address, automatic tunneling cannot be used.

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96-bits 32-bits

0:0:0:0:0:0 IPv4 Address

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Automatic Tunneling

6to4, 6over4 and ISATAP are examples of automatic Tunneling

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Description Source Address Destination Address

Packet from Host A Host B Src=IPv6 Dst=0::IPv4 of B

Tunnel from Router Host B Src=IPv4 Dst=IPv4

Tunnel from Host B Router Src=IPv4 Dst=IPv4

Packet from Host B Host A Src=0::IPv4 of B Dst=IPv6

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6to4 Tunneling6to4 is a mechanism for IPv6 sites to communicate with each other

over the IPv4 network without explicit tunnel set-up

A relay router is a 6to4 router configured to support transit routing between 6to4 addresses and native IPv6 addresses.

The IANA permanently assigned one IPv6 address prefix for “6to4”. It is 2002::/16.

The “6to4” prefix 2002::/16 can be prepended to a host or router’s globally-unique 32-bit IPv4 address (<IPv4-Addr>) to form a 48-bit “6to4” prefix 2002:<IPv4-Addr>

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6to4 Tunn.. In all scenarios the 6to4 router advertises the prefix 2002:IPv4::/48 to

the local net

6to4 is an efficient method for routing between 6to4 networks, but may be inefficient between native IPv6 networks and 6to4 networks

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DUAL-STACKDual-stack node has complete support for both IPv4 &


In communication with IPv6 host, it acts like IPv6 only node and to communicate with IP4 only host, it acts like IPv4 only node.

Three mode of operation: IPv6-stack, IPv4-stack & Dual-stack

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DSTM: Dual Stack Transition MechanismDSTM is an IPv4 to IPv6 transition proposal based on the use of IPv4

over IPv6 dynamic tunnels and the temporary allocation of IPv4 global addresses to Dual-Stack hosts

DSTM is intended for IPv6-only networks in which hosts still need to exchange information with other IPv4 hosts or applications

DSTM benefits IPv4 applications are run over an IPv6-only network. Network administration is simplified: only IPv6 is routed inside the

domain. Need of IPv4 global addresses are reduced: Hosts are given a global IPv4

address on a temporary basis only when an application requires it.

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DSTM: configuration A Dual-stack host in an IPv6-only network wishing to communicate using IPv4;

A DSTM server who administrates the IPv4 addresses pool and

A DSTM gateway in charge of encapsulation and decapsulation of IPv4 over IPv6 packets. In the architecture required for DSTM, only C needs to have direct IPv4 connectivity and a permanent IPv4 address.

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Tunnel BrokerTunnel broker with the dedicated servers to manage automatic tunnel request

form end users

Tunnel broker is the point where users connects to register and activate tunnels

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Tunnel Broker…Tunnel broker clients are the dual stack nodes where TB and clients

have to share pre-configured or automatically established security association.

TB Share load of network tunnel end points with several tunnel servers by sending configuration orders to relevant tunnel server whenever a tunnel has to be created.

Communication between the broker and the servers can take place with IPv4 or IPv6.

A tunnel server is a dual stack router connected to the internet

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TranslationMain goal is to provide transparent routing for nodes in IPv6 to

communicate nodes in IPv4.

Translate IPv6 packets into IPv4 packets & vice-versa

It offer transition mechanism in addition to tunneling/dual-stack.

Network Address Translation-Protocol Translation (NAT-PT) is the technique widely been used to overcome the limitation of IPv4 address.

IP, TCP, UDP, ICMP header s/messages are translated

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Stateless IP/ICMP Translation (SIIT) & Network Address translator Protocol Translator

NAT-PT allows IPv6 only host to talk to IPv4 only hosts and vice versa

IPv4 NAT=> Translate one IPv4 address to Another IPv4 address

Here NAT refers to translation of IPv4 address to IPv6 and Vice-Versa.

Provides routing between IPv4 and IPv6 address realms

All NAT-PT configurations are performed on router and hence no changes are made to hosts.

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Protocol TranslationTranslating IPv4 headers to IPv6 headers

Source address: The low-order 32 bits is the IPv4 source address. The high-order 96 bits is the designated PREFIX for all v4 communications. Addresses using this PREFIX will be routed to the NAT-PT gateway PREFIX::/96).

Destination address: NAT-PT retains a mapping between the IPv4 destination address and the IPv6 address of the destination node. The IPv4 destination address is replaced by the IPv6 address retained in that mapping.

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Protocol TranslationTranslating IPv6 headers to IPv4 headers

Source address: The NAT-PT retains a mapping between the IPv6 source address and an IPv4 address from the pool of IPv4 addresses available. The IPv6 source address is replaced by the IPv4 address retained in that mapping.

Destination address: IPv6 packets that are translated have a destination address of the form PREFIX::IPv4/96. Thus the low-order 32 bits of the IPv6 destination address is copied to the IPv4 destination address.

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To communicate with IPv4 node, NAT-PT generate fake IPv6 address of IPv4 node by appending IPv4 address of destination to the 96-bits prefix.

The prefix is supplied on the configuration

The fake address can be generated using Application Level gateway Program: Trick-Or-Treat Daemon (DNS-ALG)

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IPv6 Host A IPv4 Host BNAT-PT120.10.40/24

1-packetSrc: 2001:d30:119::2Dst: prefix::






4-packetSrc: prefix:: 2001:d30:119::2





ks ?

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DNS-ALG for NAT-PT: Trick Or Treat DaemonTOTD is a small DNS proxy name server which supports IPv6 and

enable IPv6 only sites to access IPv4 sites by using some translation mechanism such as NAT-PT

It is a IPv6 DNS proxy which receive DNS queries from clients and forward it to a normal DNS server

If the reachable normal DNS server is IPv4 only, TOTD must be configured with dual stack mechanism otherwise for IPv6 reachable DNS server, it can be configured for IPv6 only server

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TOTD..Events made when client make a request to TOTD server

Request an AAAA/A6 records: when a client request an AAAA/A6 record, the TOTD server simply forward the request to the client only if the requested record exists otherwise an A record is requested to normal DNS server and TOTD will receive an answer in IPv4 which will be translated into IPv6 address by adding certain PREFIX to the IPv4 address and forwards it to the client.

PTR lookup: when a client tries a PTR lookup, TOTD simply proxies the look up only if the PTR lookup is using normal global IPv6 address. Otherwise if the PTR lookup is using converted IPv6 address, TOTD will convert the address back to IPv4 and the PTR lookup result will be forwarded to the requested client.

Other request: other queries will be always ignored and the reply is simply forwarded to the client without modification.

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TOTDTOTD generates the fake IPv6 address by appending IPv4

address with IPv6/64 prefix.

The prefix is configured with TOTD configuration

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NAT-PT & DNS-ALG testTOTD: a DNS-ALG which is an IPv6 DNS proxy

Generates fake IPv6 address of IPv4 only node.

A combinational test with NAT-PT, DNS, DNS-ALG has been proposed.

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Totd ServerDNS-ALG


Client IPv6 Only Normal DNS


Internet IPv4/IPv6

IPv6 Only


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Users-IPv6 onlyUsers-IPv6 only

TOTD ServerTOTD Server

Issues a DNS query to ask for the IP address of


Forward the DNS querywww.ioe.edu.np

DNS Reply

DNS ServerDNS Server


DNS Reply 2001:D30:101:624:: CA46:5B06

Destination 2001:D30:101:624 ::CA46:5B06


IPv4 onlyIPv4 only












[root@tu-soi ~]# cat /etc/totd.confforwarder ::1 port 5353forwarder 2001:d30:101:1::11 port 53forwarder 2001:d30:102:1000::1001 port 53prefix 2001:d30:101:624::

[root@tu-soi ~]# ping6 www.ioe.edu.npPING www.ioe.edu.np(2001:d30:101:624::ca46:5b06) 56 data bytes64 bytes from 2001:d30:101:624::ca46:5b06: icmp_seq=0 ttl=44 time=2126 ms64 bytes from 2001:d30:101:624::ca46:5b06: icmp_seq=1 ttl=47 time=2153 ms 32

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Users-IPv6 onlyUsers-IPv6 only

TOTD ServerTOTD Server

DNS ServerDNS Server



IPv4 onlyIPv4 only


Proxy ServerProxy Server

Email ServerEmail ServerDNS












HTTP Traffic

HTTP Traffic


NAT-PT, DNS, DNS-ALG, SQUIDIPv6-SQUID: To reduce the processing overhead in NAT-PT

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[root@tu-soi ~]# tail -f /var/log/squid/access.log1199694696.227 1510 2001:d30:119:0:b091:e66d:22b:dca0 TCP_MISS/304 457 GET http://www.ioe.edu.np/stylet.css - PARENT_HIT/2001:d30:101:1::5 text/css1199694696.867 4980 2001:d30:119:0:b091:e66d:22b:dca0 TCP_MISS/200 10314 GET http://www.ioe.edu.np/ - DEFAULT_PARENT/2001:d30:101:1::5 text/html1199694697.742 1514 2001:d30:119:0:b091:e66d:22b:dca0 TCP_MISS/304 456 GET http://www.ioe.edu.np/bglink.css - PARENT_HIT/2001:d30:101:1::5 text/css


IPv4 Only web accessed via IPv6-

only Node

Address [2001:d30:119::2] port 3128

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IPv4 Mail Server accessed via IPv6-

only Node

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ComparisonMechanisms Remarks

Tunneling: Can communicate with remote IPv6 network without supporting IPv6 in ISP network Loads on the router (consumes time & CPU power for encapsulation and dcapsulation) MTU size issue and fragmentation problems

Dual-Stack: easy to use and can communicate with both hosts Two separate protocols running over single machine consumes CPU power and memory firewall protection for both protocols (burden)

Don’t solve the problem of IPv4 address exhaustion

Translation: Does not support Advanced IPv6 feature Easy to implement, single border router acting as NAT-PT IPv6 hosts can directly communicate with IPv4 hosts Independent of Hosts

Encourage for transition to IPv6 network

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Concluding RemarksMigration to IPv6 network should be done as soon as possible

due to IPv4 address inadequacy.

IPv6-Network is ready to implement, Though all the applications are not ready with IPv6 like what is available in IPv4.

More researches are needed for IPv6 compatible application implementation.

Upgrading current network to IPv6 seems difficult, so needs to upgrade by creating IPv6-only sub-network.

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Conclusion (Contd…)Currently Tunneling/Dual-Stack seems better

because IPv4 network is dominant but NAT-PT is the better approach when IPv6 become dominant.

Awareness & Training regarding the implementation is necessary in Nepal from the root by implementing IPv6 from academic research network

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The current status of IPv4/IPv6 shows that the world will have IPv6-only network beyond 2030

Conclusion (Contd…)


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Deployment Challenges and RiskFor the Government

Policy IssuesPolitical IssuesCost of overall transition (cost of HW/SW/Training)Lack of Human Resources

Private sectorsEconomical Issues-Cost of Migration (cost of HW/SW/Training)Service Related Issues

Quality and Reliability of Service after MigrationLevel of TrustNational Polices Meets with Global Standards

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Thank You!

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