linux_base-8 mystery

[Bsd B]

Hi, 
I have a question that has really stumped me. I have
searched far and wide and have found no literature on
it.
My question - Why can't i install linux_base-8 from
packages?

I am running linux_base-7.1_7 on FreeBSD 4.10-RELEASE
and wish to upgrade to linux_base-8. As root I type
"pkg_add -r linux_base-8" and get the following

Error: FTP Unable to get
ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages-4.10-release/Latest/linux_base-8.tgz:
File unavailable (e.g., file not found, no access)
pkg_add: unable to fetch
'ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages-4.10-release/Latest/linux_base-8.tgz'
by URL

It installs perfectly from ports, but why not from
packages? I am puzzled. Does any one know why or can
point me to some reference or literature explaining
this mystery?
Cheers
Bob

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