Network Address translation for SCTP

Guided by:

Mrs. Suganthi K

Dept of CSE .

Submitted by:

PAVITHRA M K

1GS05CS400

Contents• Introduction to NAT• SCTP overview• Similarities and Difference between SCTP and TCP• Multihoming• SCTP NAT Traversal scenario• Why is SCTP needed given TCP and UDP are widely

available?• Applications• Conclusion• References

Introduction to NATWhat is NAT?

Network Address Translation is a common method for separating Private networks from Global networks by translating private IP addresses to global IP address .

• NAT implementations that

support SCTP in a way

Similar TCP or UDP are

being developed first .

Why is SCTP needed given TCP and UDP are widely available?

UDP : It is a message-oriented, unreliable transport protocol.

UDP conservers the message boundaries, each message is independent of any other message.

TCP: It is a connection-oriented, reliable transport protocol.

SCTP : It combines the best features of UDP and TCP.It is a reliable message-oriented protocol.

SCTP Overview• Stream Control Transmission Protocol is a new reliable ,

connection oriented transport layer protocol.

• SCTP supports Multiple streams with an association Message oriented service Full-Duplex Communication Multi homing.

The basic association setup procedure is based on four

handshake and follows the client-server principle, This is as shown in the figure.

First the SCTP message is sent from the client

to server.

The server responds with an SCTP message,

which also contains just one chunck , the

INIT-ACK.

The client sends the state cookie in a COOKIE-ECHO chunk to the server, the server responds with a COOKIE-ACK chunck and the association established.

How NAT supports to TCP and UDP? The server addresses its packets to this global addresses, reaches the NAT, which substitutes the destination address with the address of the client.

NAT implementations that support SCTP in a way similar to TCP or UDP.

This works well for single homed SCTP association, it does not work for multi homed SCTP associations.

It is important to have NAT middle boxes that not only support SCTP in a limited way, but with all features, especially multihoming.

The transport layer checksum used by SCTP is different from the one used by UDP and TCP

Multihoming

Multi homing is defined as the ability of an association to support multiple IP addresses or interfaces at a given end point.

Continuation…..

The benefit of multi-homing is potentially greater survivability of the session in case of network failures.

The ability for a single SCTP endpoint to support multiple IP addresses.

To support multi-homing, SCTP endpoints exchange lists of addresses during initiation of the association.

SCTP NAT Traversal ScenarioSingle Point Traversal

The SCTP association go through a single NAT

Multi-Point Traversal

SCTP association in different paths.

The two SCTP endpoints in this case can be either single-homed or multi-homed.

One of the main benefits of SCTP multi-homing is redundant paths, the NAT function represents a single point of failure in the path of the SCTP multi-home association.

However, the rest of the path may still benefit from path diversity provided by SCTP multi- homing.

An SCTP-Specific Variant of NATSingle homed client and a single homed server

Single-Homed Client to Multihomed Server

Adding New NAT Middle boxes

Multihomed Client and Server

BenefitsThe existance of the multiple NAT traverse

points can preserve the path diversity of a multihomed association for the entire path.

Improve the robustness of the communication.

Applications

Available in all major operating systems, including GNU/Linux, BSD, and Solaris.

Included into the 2.6 Linux kernel.

In telephone signaling

Conclusion

In this article, we proposed a comprehensive solution for the support of SCTP in NAT middle boxes .

Motivate the necessity for a specific NAT concept with NAPT functionality, where the verification tags provided by SCPT are used to distinguish between association .

Several scenarios were analyzed to explain the manipulation of the NAT table in single-homed, multi-homed.

References

Q. Xie et al., “SCTP NAT Traversal Considerations,” draft-xie-behave-sctpnat-cons-03.txt (work in progress), Nov. 2007.

R. Stewart and M. Tüxen, “Stream Control Transmission Protocol (SCTP) NAT,” draft-stewart-behave-sctpnat-03.txt (work in progress), Nov. 2007.

R. Stewart, “Stream Control Transmission Protocol,” RFC 4960, Sept. 2007.

Queries ???