CCIE DC: Advanced FCIP MTU

Upon further investigation, it appears that there is no point increasing the FCIP MTU beyond 2300 as the FC Traffic will never exceed a certain size as per the IETF RFC:


http://tools.ietf.org/html/draft-ietf-ips-fcovertcpip-00

5.2 FC Frame Mapping to TCP/IP packets


     Fig.2  shows the mapping of the FC frame into an TCP/IPv4 Packet.
     The FC to TCP/IP  mapping (and the reverse) mapping is one-to-one
     since  the maximum size  of the encapsulated FC  Frame along with
     the header fields does not exceed 2148 bytes.

     The  minimum size FC  Frame is 36 bytes resulting in a  maximally
     minimum IP MTU size of 156 bytes. (The maximally minimum MTU size
     is  the IP packet  with the minimum size payload and  the maximum
     size IP headers and TCP headers).

     The maximum size FC frame is 2148 bytes resulting in a nominal IP
     packet size of 2188 bytes.  Fig. 2  shows the  format of the IPv4
     packet  with  the  standard  20-byte  IP fixed header,  a 40-byte
     optional IP header, the standard 20-byte TCP fixed header and TCP
     options.  For the case of the maximum size payload of 2148 bytes,
     the maximum TCP/IPv4 packet size is 2268 bytes.

     The  maximum  size  FC  frame  can  cause  the  IP  packet  to be
     fragmented  when  the  data  link  cannot  support this MTU size.
     Furthermore, TCP may also segment the data if the maximum segment
     size (MSS) is less than the size of the frame.  When an IP packet
     is fragmented, the required parts of the header must be copied by
     all fragments and the option field may or may not be copied. When
     a TCP packet is segmented, normal TCP  operations are responsible
     for receiving  and re-sequencing the data prior  to passing it on
     to the FC processing portion of the device.