Implementation and Evaluation of a NAT-Gateway for the General Internet Signaling Transport Protocol


Roland Bless
Martin Röhricht


The IETF's Next Steps in Signaling (NSIS) framework provides an
up-to-date signaling protocol suite that can be used to dynamically
install, maintain, and manipulate state in network nodes. In its
two-layered architecture, the General Internet Signaling Transport
(GIST) protocol is responsible for the transport and routing of
signaling messages. The strong presence of Network Address Translation
(NAT) gateways in today's Internet infrastructure causes some major
challenges to network signaling protocols like NSIS.
The address translation mechanisms performed by common NAT gateways
are primarily concerned with address information contained in the
IP and transport layer headers.
Signaling sessions between two signaling peers do, however, rely
on address information contained in GIST data units. If a non GIST-aware
NAT gateway merely adapts addresses in the IP and transport headers only,
inconsistent state will finally be installed at the signaling nodes.
In this paper we present the design, implementation,
and evaluation of an application level gateway for the GIST
protocol, that translates GIST messages in a way that allows to
establish signaling sessions between any two GIST nodes
across a NAT gateway.


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