What is the largest number of bytes I can send through one UDP send block packet using the UDP send block in the Beagle board support package?

Using Embedded Linux with Beagle Board, what is the maximum number of bytes I can send in a single packet with the Send UDP block? Can't find any reference to it in the documentation but when I try to send 2000 bytes (1000 16 bit words) Wireshark indicates it's getting fragmented.

Answer 1

[MathWorks Support Team]

The packet fragmentation limit depends on the Maximum Transfer Unit (MTU)

value set for LAN the customer is using. That is MTU is a mutually agreed

value in between all the computers, routers, switches in a LAN. The

following command displays MTU setting for the BeagleBoard:

/sbin/ifconfig eth0

eth0      Link encap:Ethernet  HWaddr 9a:73:16:80:18:6a
         inet addr:172.28.145.93  Bcast:172.28.145.255  Mask:255.255.255.0
         inet6 addr: fe80::9873:16ff:fe80:186a/64 Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1488  Metric:1
         RX packets:37368657 errors:0 dropped:0 overruns:0 frame:0
         TX packets:43107080 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:2299134916 (2.2 GB)  TX bytes:209271720 (209.2 MB)

Note that the default MTU is 1488 as seen above. One can change the MTU

value of a Linux system by using ifconfig command as explained in the

following article:

https://www.cyberciti.biz/faq/centos-rhel-redhat-fedora-debian-linux-mtu-size/

However, do note that this is no guarantee that UDP packets will not be

fragmented. The routers /switches in the LAN network can fragment UDP

packets even if it is transmitted at full size on the BeagleBoard.