Simple stuff , but works perfect if you want to monitor some particular transfers between nodes.

/etc/sysconfig/iptables
on the client host. Just below the line
*filter
Add rules like:
### count rules below ###
:count-rule - [0:0]
-A INPUT -j count-rule
-A OUTPUT -j count-rule
# add both rules below for each host you want to monitor
-A count-rule -d <remote host to monitor>
-A count-rule -s <remote host to monitor>
### end counting rules ###
Restart iptables:
# service iptables restart
Flushing firewall rules:                                   [  OK  ]
Setting chains to policy ACCEPT: filter                    [  OK  ]
Unloading iptables modules:                                [  OK  ]
Applying iptables firewall rules:                          [  OK  ]
Loading additional iptables modules: ip_conntrack_netbios_n[  OK  ]
#
Now you can check the packets/bytes using:
# iptables -v -n -L count-rule
Chain count-rule (2 references)
 pkts bytes target  prot opt in   out   source      destination
 44  2960            all  --  *    *   0.0.0.0/0   24.85.243.94
 30  22040           all  --  *    *  24.85.243.94   0.0.0.0/0 
# 
and if you want to zero the counters, use:
# iptables -Z count-rule