Saturday, October 29, 2011

Stateful and Stateless NAT64

It's very easy to deploy IPv6 for MPLSVPN service provider who uses IPv4 as transport IPv6 traffic. But in the case of mobile users or normal enterprise users, it is totally different.
In my previous post, I have mentioned traffic flow of DNS64 when IPv6 host communicates with IPv4 server. NAT64(Network Address Translation) works in either stateless or stateful mode. Both modes has its own advantages and disadvantages.

Stateless NAT64
Figure 1

In stateless NAT64, state is not preserved which means for every IPv6 user a dedicated IPv4 address is required. As we are in IPv4 depletion phase, its very difficult to adopt this mode of NAT64. The only advantage of using stateless NAT64 when you have few numbers of IPv6 addresses(NAT46). NAT64 stateless is useless because of the reasons mentioned by Ivan in his post.

Stateful NAT64
Figure 2

In stateful NAT64, states are maintained like it is happened in NAT-PT scenarios. A single IP Address is used for all the private users with different port numbers. In the above diagram, a single IPv4 address is used with different port numbers for all the users of IPv6 which are in that LAN to access a public IPv4 server.

Read the white paper stating the difference between stateless and stateful NAT64

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Thursday, October 27, 2011

NAT64 and DNS64 Traffic Flow

DNS(Domain Name System) is the crucial part of any service provider. As we are moving towards IPv6 world, DNS role would be crucial to resolve the IP addresses to name.

The utmost challenge is when the host is IPv6 and would like to access IPv4 internet servers. In that case DNS64 will come into play and make some amendments after getting reply from IPv4 servers and sent its request with synthesized AAAA reply to host.(Scenario 3)

I have made three different scenarios as depicted below:-
1. NAT44 DNS Flow
2. IPv6 User Accessing IPv6 Internet (DNS Flow)
3. IPv6 User Accessing IPv4 Internet (DNS Flow)

Scenario 1:- IPv4 User Accessing IPv4 Internet

Figure 1
DNS flow is very simple, IPv4 user sends a request to DNS server with A request, DNS server checks it locally and in case doesn't fid any results it sends an request to the internet DNS server which is also known as authoritative dns server. Internet DNS server replies it back with A reply. 

Scenario 2:- IPv6 User Access IPv6 Internet

Figure 2

This is the same flow as we have seen in scenario 1.

Scenario 3:- Ipv6 Host Access IPv4 Internet

Figure 3

Step 1:- IPv6 user sends a AAAA request of a website to DNS64 server. 
Step 2:- DNS64 server sends a request to the internet authoritative DNS server.
Step 3:- Internet DNS sends a NULL reply to the local DNS64 server, as it doesn't have AAAA entry of the request website.
Step 4:- Local DNS64 server sends A request to Internet DNS server.
Step 5:- Internet DNS server sends reply to A request.
Step 6:- Local DNS64 server creates a synthesised AAAA reply and sends it to local subscriber.
Steo 7:- Local Subscriber sends a IPv6 request website to NAT64 device which is also known as carrier grade nat device. That device creates a 6to4 entry in the table and forwards the request to the IPv4 internet server.

Check the depicted below example how DNS64 synthesised AAAA reply to IPv4 host when DNS64 receives IPv4 address from Internet server.

Figure 4

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Tuesday, October 18, 2011

How MPLS Looks In IOS-XR

Capturing few outputs from IOS-XR Command Line Interface. IOS-XR commands output is fully detailed with each and very data structure.

Show interface brief

Show interface brief sumamry

Show mpls ldp neighbor
 Show mpls ldp forwarding summary
 show mpls label table detail

show mpls ldp forwarding

show mpls label table

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Thursday, October 6, 2011

Apple's visionary Steve Jobs dead at 56

Steve Jobs, the transcendent Silicon Valley entrepreneur who reinvented the world's computing, music and mobile phone industries and changed the daily habits of millions around the globe, died on Wednesday at the age of 56.
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