TCP/IP Tutorial and Technical Overview - IBM Redbooks

14.2.6 Security issues
multicast option is described in RFC 2090. Figure 14-8 is an example of a TFTP
read request packet modified to include the multicast option.
Figure 14-8 The TFTP Multicast header
If the server accepts the multicast, it sends an option acknowledgment (OACK)
packet to the server including the multicast option. This packet consists of the
multicast address and a flag that specifies whether the client should send
acknowledgments (ACK).
Because TFTP does not have any authentication mechanism, the server is
responsible for protecting the host files. Generally, TFTP servers do not allow
write access and only allow read access to public directories. Some server
implementations also might employ host access lists to restrict access to only a
subset of hosts.
14.3 Secure Copy Protocol (SCP) and SSH FTP (SFTP)
Secure Copy Protocol (SCP) and Secure Shell File Transfer Protocol (SFTP) are
two methods of implementing secure transfer of files from one host to another.
Neither protocol has been architected to perform authentication, and instead rely
on the underlying SSH protocol on which they were built. This not only simplifies
the implementation of the protocol, but avoids the pitfalls of traditional FTP (see
14.1, “File Transfer Protocol (FTP)” on page 514) by encrypting all data that
passes between the two hosts.
Neither protocol is RFC architected, though an Internet draft currently exists for
SFTP. Despite this lack of standardization, the protocol is implemented widely
enough to be considered a de facto industry standard, and thus warrants
discussion.
14.3.1 SCP syntax and usage
SCP functions much like the copy (cp) command on UNIX-based systems, and
takes the following format:
scp flags sourceFile destinationFile
Chapter 14. File-related protocols 533