Study on Migration from IPv4 to IPv6 of a Large Scale Network

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Introduction
Currently, the Internet consists of native IPv4, native IPv6, and IPv4/IPv6 dual stack networks.Unfortunately, IPv4 and IPv6 are unsuited protocols.When both IP versions are available and the users of Internet desire to connect without any limitations, a transition mechanism is mandatory.During the occasion of migration from IPv4 to IPv6 networks, a number of transition mechanisms have been suggested by IETF to ensure smooth, stepwise and independent changeover.The conception of transiting from IPv4 mesh to IPv6 mesh is being processed strongly.The transition between IPv4 internet and IPv6 will be a long procedure as they are two completely separate protocols.IPv6 is not backward well-suited with IPv4, and IPv4 hosts and routers will not be adept to deal directly with IPv6 traffic and vice-versa.As IPv4 and IPv6 will co-exist for a long time, this wants the transition and inter-operation mechanism.Due to this cause several transitions mechanisms have been developed that can be used to build the transition to IPv6 efficiently.Most of the applications today support IPv4 and therefore there is a need to run these applications on IPv6 access network, especially to persons who are generally on mobile and they want to securely connect to their home network so as to reach IPv4 services.IPv6 is developed as a network layer protocol, overcoming the problems in IPv4.Its 128-bit address format considerably enlarges the address space and will gratify the address demands for a fairly long time.Although, IPv6 has no built-in backwards compatibility with IPv4, which means IPv6 networks cannot correspond with IPv4 in environment.Competently IPv6 has considered a parallel, independent network that coexists with its support IPv4.IPv6-supported applications and IPv6-accessible contents are still the marginal; the majority of network resources, services and applications still remain in IPv4.A number of transition techniques are existing to maintain the connectivity of both IPv4 and IPv6, to accomplish inter connection between IPv4 and IPv6, and also support the adoption process of IPv6.Vendors expect to invest on implementing well-developed transition techniques, so that their products can have good capability and bring high profits.As for internet service providers (ISP), they require to find a way to provide the existing services for both IPv4 and IPv6 users, and organize their services with an expected deployment of transition techniques on the Internet.
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Transiti
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Dual S
The Dual parallel on vice versa the edge.T migration routers.On servers and performan simultaneo availability a result, IP The IP header version field would play an important role in receiving and sending packets.In other words, this kind of IPv6 transition is the encapsulation of IPv6 within IPv4.The complete transition can be managed by domain name system (DNS).

Tunnelling
Tunnelling, from the insight of transitioning, enables unsuited networks to be bridged and it is usually applied in a point-to-point or sequential manner of a network.Three mechanisms of tunnelling are offered: IPv6 over IPv4, IPv6 to IPv4 automatic tunnelling and tunnel broker.Tunnelling IPv6 traffic over an IPv4 network is another possibility.This approach allows the IPv6 traffic to be encapsulated in an IPv4 packet and forwarded, creating an IPv6 tunnel over the IPv4 infrastructure.A tunnel can be created as a solution for transporting IPv6 traffic, from IPv6 node to the destination IPv6 node, over the IPv4-only network.A "virtual link" is created and, from the perspective of the two establishing IPv6 nodes, this appears as a point-to-point link.The different types of tunnelling techniques can be categorized into two types: manually configured and automatic tunnelling.A point-to-point link has to be manually configured, as the name suggests.For automatic tunnelling, an IPv6 node can dynamically tunnel packets by using a 6 to 4 address.This is used to transfer data between compatible networking nodes over incompatible networks.There are two ordinary scenarios to apply tunnelling: the allowance of end systems to apply off link transition devices in a distributed network and the act of enabling edge devices in networks to inter-connect over incompatible networks.

Translation
The meaning of translation is to convert directly protocols from IPv4 to IPv6 or vice versa, which might result in transforming those two protocol headers and payload.This mechanism can be established at layers in protocol stack, consisting of network, transport, and application layers.The translation method has many mechanisms, which can be either stateless or stateful.While stateless means that the translator can perform every conversion separately with no reference to previous packets, stateful is the vice versa, which maintains some form of state in regard to previous packets.The translation process can be conducted in either end systems or network devices.
The fundamental part of translation mechanism in transition process is the conversion of IP and ICMP packets.All translation methods, which are used to establish communication between IPv6-only and IPv4-only hosts, for instance, NAT-PT or BIS, apply an algorithm known as stateless IP/ICMP translator (SIIT).

Design a Large Scale Network in Dual Stack
In this paper, a large scale network is design based on dual stack network.This dual stack network is designed for a nationwide ISP.Design considerations are given below:

Topology Design
In this paper our designed ISP has 4 main operating area or region.Each region has 2 small POP.Each region network has one data centre to host content.Regional network are inter-connected with multiple link.
(i) Regional Network Each regional network has three routers.One core and two edge routers, point of presence (POP) for every region.POP will use a router to terminate customer network, i.e. edge router.Each POP is an aggregation point of ISP customer.
(ii) Design Consideration Registries will regularly assign the next block to be contiguous with the first allocation, minimum allocation is /32.Very expected that subsequent allocation block will make this up to a /31.

Address Plan for IPv6
For the address planning we followed RFC 3849, which is IPv6 address prefix reserved for documentation.Details IP address plan for IPv6 is given below (Tables 1 to 8):

Address Plan for IPv4
IP address Plan for IPv4 is given below (Table 9 to 12):   together in order to minimize the number of routing information carried by the core routers, which makes it a dominant Internet routing protocol and allows the aggregation of routers.Internet Protocol version 6 (IPv6) uses CIDR routing technology and CIDR notation in the same way as Internet Protocol version 4 (IPv4).IPv6 was designed for fully classless addressing.In CIDR, all Internet blocks can be of random size and classless addressing uses a variable number of bits for the network and host portions of the address.A view of the traffic collected using Wireshark is shown in Figure 4.It illustrates the protocol structure for a randomly selected BGP update message, which contains path attributes for the advertised Network Layer reach ability Information (NLRI).It opens and saves captured packet data, imports and exports packet data from and to other capture programs, filters and searches packets based on various criteria, colorizes packet display based on filters, and creates various statistics.As messages originate from multiple protocols, the frame shows Ethernet protocol source and destination address, the source and destination addresses of IP, source and destinations port numbers for TCP, and details of BGP.The update message has a marker of 16 bytes and length of 19 bytes.There are four types of message like type 1 indicates open message, Type 2 indicates that this message is an update message, type 3 indicates notification message, and type 4 indicates keepalive message.IGP is assigned to the origin attribute, AS path attribute has a length of 19 bytes, maximum hop limit 64, and payload length 39 bytes.

TCP Operations
The TCP operation is defined in RFC1323 are no operation (for padding), maximum window size (SYN), window scale (SYN), SACK permitted (SYN), SACK option (Acknowledges), time stamp (SYN & Acknowledges).The usage of the TCP SACK option is negotiated during the 3-Way hand shake.The Selective acknowledgement (SACK) option can be activated from one or both sides.Without SACK option, only the last received segment of a contiguous series can be acknowledged.The SACK Option allows acknowledging non-contiguous segments of a series and can request for specific segments.The SACK Option can improve the throughput of LFN's significantly.Acknowledges (ACK) is used to point whether the acknowledgment field is valid.PSH is place when the sender requests the remote application to push this data to the remote application.RST is used to reset the connection.SYN (for synchronize) is used inside the connection start up phase, and FIN (for finish) is used to close the connection in an arranged mode.Information gathered during the handshake consists of the sender and receiver advertised window Sizes (rwnd), maximum segment size (MSS), whether a window scale option (WS) is being used, and if the sender and receiver support selective acknowledgement (SACK) options.The TCP checksum is applied to a synthesized header that contains the source and destination addresses from the external IP datagram.The first stage of a TCP session is establishment of the connection.This requires a three-way handshake, ensuring that both sides of the connection have an explicit understanding of the sequence number space of the remote side for this session.
The performance insinuation of this protocol exchange is that it takes one and a half round-trip times (RTTs) for the two schemes to synchronize status before any data can be sent.Once the connection is established, TCP starts slowly to determine the bandwidth of the connection and to avoid overflowing the receiving host and other devices or links in the path.After the connection has been established, the TCP protocol manages the consistent exchange of data between the two systems.The traffic service reply time is explicit as the time between a request and the corresponding response.A single packet of length 19 is sent with the PSH flag set.The PSH flag indicates to the receiver that the contents of the receive buffer should be immediately passed to the application layer.Another data packet of size 19 is sent.At this point there are 20 bytes of in flight or unacknowledged data on the wire.8 average RTT for IPv6 address 2406:6400::4 to 2406:6400::5 are below 0.05 s.Sometimes we got higher RTT when router working process becomes high.In the Figure 9 shows RTT for IPv4 address 172.16.15.5 to 172.16.15.4.In Figures 8 and 9 shown for IPv4 and IPv6 average RTT are below 0.05 s.The differences in round trip time on IPv4 and IPv6connection do not show significant difference.

TCP CUBIC
TCP CUBIC is an achievement of TCP that has an optimized congestion control algorithm for networks with large bandwidth delay product (BDP).The key aspect of CUBIC is that its window enlargement function is defined in real time so that its increase will be independent of RTT.Instead, window development depends only on the time between two successive congestion events.This property of CUBIC makes it friendly and fair to other flows in heterogeneous network.Congestion window of CUBIC is determined by the following function: Wcubic = C(t-K) 3 + Wmax, where C is a scaling factor, t is the elapsed time from the lastwindow reduction,Wmaxis the window dimensions just before the last window reduction and K= Wmaxß/C, whereK is theestimated time period that would take to reach Wmax.Disregarding further packet loss, K is computed as follows: Wmin is the reduced window size just after the last congestion event.Congestion window after congestion event is in steady state where it grows concavely up to Wmax, after which it enters probing state and grows convexly until next congestion event.ß is a constant multiplicative decrease factor applied to window reduction at the time of loss event.As per the Figure 8 exposed, the minimum RTT was around 0.03 sec and maximum RTT was around 0.18.The congestion C=0.5, t=0.18,K=3, β=0.8 K= 65535*0.8/0.5=47.1553 Wcubic = 0.5(0.18-47.1553) 3 + 65535 = 13705.3004or 13705 approx.In this Graph we study that, CUBIC set up snooping for bandwidth in which the window grows step-by-step at the start, accelerating its development as it proceeds away from Wmax.This assessed development Wmax improves the constancy of the protocol and increase the consumption of the network while the fast growth left from Wmax ensures the scalability of the protocol.

Throughput
Throughput is imperative to understanding end-to-end performance.In Figure 10 shows the TCP throughput outcomes of a perfect form and a real IPv6 backbone for different packet sizes.From the TCP throughput outcomes we discerned the very close throughputs for both IPv4 and IPv6 networks in terms of small message sizes.From the TCP throughput results, we furthermore discoveredthat throughputs for both IPv4 and IPv6 networks in any message size are very similar.In a real large dual stack network, the throughputs of the IPv6 augment rapidly in small message sizes of 256 bytes.Then the throughput becomes level until the 768-byte message size range.Conversely, the throughputs decreased a little bit up to the 1408-byte message size range.In a real large-scale network, we attained a minor degradation for IPv6 compared to IPv4 networks because the overhead of the IPv6 address size is more significant.TCP reflect on two most important factors: TCP window size and the round trip latency to transfer data.If the TCP window size and the round trip latency are known, the maximum possible throughput of a data transfer between two hosts may be calculated in spite of of the bandwidth using the expression: TCP-Window-Size-in-bits / Latency-in-seconds = Bits-per-second throughput.Instantaneous throughput is the rate (bps) at which a host receives the packets.
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Conclus
In Figure /48 network address for whole backbone.Customers get one /48 block network address.Unless they have more than 65k subnets inwhich case they get a second /48 (and so on).In typical deployments today Several ISPs give small customers a /56 or single LAN end-sites a /64, e.g.: /64 if end-site will only ever be a LAN.A /56 block network for medium end-sites (e.g.small business) and a /48 network block for large end-sites.

Table 1 .
Top level distribution infrastructure and customers

Table 2 .
Summarization option infrastructure and customers

Table 4 .
Details loopback address