Hi!
It seems like something has broken with the tcp code in 1.3.87.
I have problem with normal ftp.
With 1.3.86 I get the following:
( ior is running 1.3.79 )
  henrik@triton ~ > ftp triton
  ftp> get /usr/local/bin/netscape /tmp/temp
  4546564 bytes received in 4.21 secs (1.1e+03 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp
  4546564 bytes received in 4.18 secs (1.1e+03 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 6.76 secs (6.6e+02 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 4.73 secs (9.4e+02 Kbytes/sec)
  henrik@triton ~ > ftp ior
  ftp> get /usr/local/bin/netscape /tmp/temp
  4014084 bytes received in 6.07 secs (6.5e+02 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp
  4014084 bytes received in 6.94 secs (5.6e+02 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 9.72 secs (4.6e+02 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 8.79 secs (5.1e+02 Kbytes/sec)
But when I try the same under 1.3.87 there is trouble...
  henrik@triton ~ > ftp triton
  ftp> get /usr/local/bin/netscape /tmp/temp
  4546564 bytes received in 3.13 secs (1.4e+03 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp                                            <---
  200 PORT command successful.                                                          <---
  150 Opening BINARY mode data connection for /usr/local/bin/netscape (4546564 bytes).  <---
     [Here I have to press Ctrl+C after 10 sek.]                                        <---
  receive aborted                                                                       <---
  waiting for remote to finish abort
  426 Transfer aborted. Data connection closed.
  226 Abort successful
  2765184 bytes received in 16.9 secs (1.6e+02 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp
  4546564 bytes received in 2.24 secs (2e+03 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp
  4546564 bytes received in 1.99 secs (2.2e+03 Kbytes/sec)
  ftp> get /usr/local/bin/netscape /tmp/temp                                            <---
  200 PORT command successful.                                                          <---
  150 Opening BINARY mode data connection for /usr/local/bin/netscape (4546564 bytes).  <---
    [One more time ...]                                                                 <---
  receive aborted                                                                       <---
  waiting for remote to finish abort
  426 Transfer aborted. Data connection closed.
  226 Abort successful
  3162584 bytes received in 17.4 secs (1.8e+02 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 2.49 secs (1.8e+03 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp                                            <---
  200 PORT command successful.                                                          <---
  150 Opening BINARY mode data connection for /tmp/temp.                                <---
    [and again.. Ctrl+C after 10 sek]                                                   <---
  send aborted                                                                          <---
  waiting for remote to finish abort                                                    <---
    [ftp totaly stops - I have to press Ctrl+Z and kill ftp ]                           <---
  henrik@triton ~ > ftp triton
  ftp> put /usr/local/bin/netscape /tmp/temp                                            <---
  200 PORT command successful.                                                          <---
  150 Opening BINARY mode data connection for /tmp/temp.                                <---
    [Ctrl+C after 10 sek]                                                               <---
  send aborted                                                                          <---
  waiting for remote to finish abort                                                    <---
  [Ctrl+Z and kill after 10 sek]                                                        <--- 
  henrik@triton ~ > ftp ior
  ftp> put /usr/local/bin/netscape /tmp/temp
  4546564 bytes sent in 8.15 secs (5.4e+02 Kbytes/sec)
  ftp> put /usr/local/bin/netscape /tmp/temp
  200 PORT command successful.
  150 Opening BINARY mode data connection for /tmp/temp.                               <---
    [Ctrl+C after 10 sek]                                                              <---
  send aborted                                                                         <---
  waiting for remote to finish abort                                                   <---
  [Ctrl+Z and kill after 10 sek]                                                       <---
  henrik@triton ~ > ftp ior
  ftp> get /usr/local/bin/netscape /tmp/temp 
  4014084 bytes received in 4.55 secs (8.6e+02 Kbytes/sec)                           :)
  ftp> get /usr/local/bin/netscape /tmp/temp 
  4014084 bytes received in 6.13 secs (6.4e+02 Kbytes/sec)
  ftp> quit
If I do a 'strace -p' on the ftp process it is waiting in a read ( 'read(5, ' )
It doesn't work if I run ftp from ior either.
There has not been any major problem for me with the latest kernel versions ( 80-85 ).
triton is :
Pentium 100 MHz, 16Mb RAM, triton MB, 2 ide disks and I have a direct 
connection to internet. I'm running :
basically debian development but also,
libc 5.3.9
procps-0.99a
patched sysvinit-2.59
modules-1.69f
net-tools-1.3.50f
binutils-2.6.0.12
.config:
CONFIG_MODULES=y
CONFIG_KERNELD=y
CONFIG_NET=y
CONFIG_PCI=y
CONFIG_PCI_OPTIMIZE=y
CONFIG_SYSVIPC=y
CONFIG_BINFMT_AOUT=m
CONFIG_BINFMT_ELF=y
CONFIG_KERNEL_ELF=y
CONFIG_M586=y
CONFIG_BLK_DEV_FD=m
CONFIG_BLK_DEV_IDE=y
CONFIG_BLK_DEV_TRITON=y
CONFIG_BLK_DEV_RAM=m
CONFIG_INET=y
CONFIG_IP_NOSR=y
CONFIG_SKB_LARGE=y
CONFIG_NETDEVICES=y
CONFIG_NET_ISA=y
CONFIG_NE2000=y
CONFIG_MINIX_FS=m
CONFIG_EXT2_FS=y
CONFIG_FAT_FS=m
CONFIG_MSDOS_FS=m
CONFIG_PROC_FS=y
CONFIG_NFS_FS=m
CONFIG_SERIAL=y
CONFIG_PRINTER=m
CONFIG_WATCHDOG=y
CONFIG_SOFT_WATCHDOG=y
CONFIG_SOUND=m
I hope this helps. 
( I can do additional testings if its needed. )
I liked these improved transfer rate :) , so I hope it can be fixed...
thanks!
/ Henrik Wallin, henrik@triton.campus.luth.se