Changes between Version 7 and Version 8 of Internal/OpenFlow/TunnelNotes

Timestamp:

Sep 28, 2010, 6:01:59 PM (14 years ago)

Author:

ssugrim

Comment:

—

Internal/OpenFlow/TunnelNotes

@@ -52 +52 @@
        Tcpdump only captures software forwarding packets(i.e. packet-ins and packet-outs). So most of the packets handled by hardware are not shown.
     }}}
+ 1. TFTP Bug: When imaging a node the the entire imaging process dies during tftp stage.  '''Solved 8/19/2010'''
 
 
@@ -132 +133 @@
 ./nox_core -c ./etc/nox.xml -v -i ptcp:6633 routing
 }}}
+
+=== 8/19/2010 ===
+
+Apparently the TFTP problem is due to MTU size. The main issue is that in order to make room for the tcp/ip header, the tunnel has to shift the frame by 40 bytes, and then unshifts on the other size. The default configuration of the tftp server is to negotiate the maximum  Ethernet frame size, which is 1460. When the frame is passed through to the other side, the tftp client sees the frame as corrupt (missing 40 bytes) and then drops it.  Thus the process never gets passed the first block, and the whole process times out. The temporary solution (read "hack") was to lower the mtu in the tftp daemon so that the frame is under filled and can pass through the tunnel "uncorrupted". To wit we needed to change the repository1:/etc/default/tftpd-hpa file and add the option -B 1024. 
+
+The current file looks like so:
+{{{
+ssugrim@repository1.:/etc/default$ more tftpd-hpa
+# /etc/default/tftpd-hpa
+
+TFTP_USERNAME="root"
+TFTP_DIRECTORY="/tftpboot"
+TFTP_ADDRESS="0.0.0.0:69"
+TFTP_OPTIONS="-l -B 1024 -s"
+}}}