Datatek IPv6 Transformer User Manual - Manual (Page 54)

S E C T I O N 8 W E B G U I S Y S T E M
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8.11 FTP Gateway
FTP uses a command and response protocol over a connection from a client to a server
established to a predefined TCP port. The FTP protocol is used to initiate file transfers and other
data transfers over dynamically established connections.
When using the Transformer, an IPv4 host that uses FTP, either as a client or a server, is
positioned on the v4 side of the Transformer, with the rest of the network on the other side. That
host may need to continue using FTP, but now a layer of addressing and protocol transformation
stands between that host and any remote host. The major problem is that the protocol requires
exchanging address and protocol information, but the two sides have differing views of both the
addressing and the protocol. To resolve that problem, the Transformer provides an “application
layer gateway” (ALG) to provide the transformation that allows the two hosts to communicate.
Figure 23. FTP Gateway Screen shows there are 2 choices that a user can select: to enable the
FTP-ALG calling a host-side and/or network-side server on the standard FTP port. By checking
one or both entries, the ALG is activated, which will perform the proper IPv4-IPv6 translation
between the client and server. The variations covered by the FTP-ALG are:
Client on IPv4 host, IPv6 server on network
Client on IPv4 host, IPv4 server on network
IPv6 client on network, server on IPv4 host
IPv4 client on network, server on IPv4 host