Maybe it has an MTU of less. Obsolete IP option 12 can send this during connect without the ICMP of PATH MTU Discovery.
The MSS is the total remote buffer, the MTU is the packet max. Disregarding the chance of TCP options, a packet header is 20 IP + 20 TCP, so a packet sends MTU - 40, and the number of packets sent before ack is MSS/(MTU-40) including any partial. Since this is local, the ack round trip should be very short, so packets should not be MSS trimmed unless there is blocking downstream.
Thanks for your support.
Well, I don't find anything in the IP header(s) which looks like IP option 12. Have attached a small wireshark dump, if you would like to have look though.
If it is to any help, the MTU of the interface at my host machine is set to 1500. And regarding the chip, I know it can handle a MTU of 536 + headers, as I can see the Windows application send it packets of this size (from the same machine too).
Hi,
When i try this command
ping ukblx151.ukhx.astrazeneca.net -n 3 | grep icmp
it gives following error :mad::
0821-077 ping: illegal packet size.
But when i give command
ping ukblx151.ukhx.astrazeneca.net
It returns correct output.:D
Could you please help? (2 Replies)
how to get network packet size
I would like get network output rate(kb/sec)
I type command "netstat -i"
Ipkts Ierrs Opkts Oerrs 653387 0 678202 0
but i didn't know what is it packet size ,
how could i get it? (1 Reply)
Hello,
I'm having an issue with TCP sockets.
When the TCP connection is terminated on one end, TCP packet with RST flag set is being sent to the sender. All the packets sent so far were carrying the DSCP 'AF21' set by me. But packet with RST flag is carrying DSCP '0'.
Is this expected or... (0 Replies)
Hi all,
I need to change the source port number of an outgoing TCP packet. First I have to bind the socket to a particular port(suppose 9001) but when I send the TCP packet I want to change the source port number lets say to 9002 still letting the socket to be bound to the same old port (9001).... (0 Replies)
We're running Solaris 7 on FDDI n/w on an E6500 host and wish to use MTU (packet size) > 1500, more like 3072 bytes to begin with and possibly up to 4096 bytes.
Linux has /etc/network/interfaces. Does ANYONE remember the equivalent in Unix? When I do ifconfig eth0 mtu 4000, I get the error... (0 Replies)
Greetings, I'm stuck in a time warp using ancient machines from the prehistoric era that should be rightfully displayed in the Smithsonian.
We're running Solaris 7 on FDDI n/w on an E6500 host and wish to use MTU (packet size) > 1500, more like 3072 bytes to begin with and possibly up to 4096... (9 Replies)
I have problem with oracle solaris 10 running on oracle sparc T4-2 server.
Os information: 5.10 Generic_150400-03 sun4v sparc sun4v
Output from tcpstat.d script
TCP bytes: out outRetrans in inDup inUnorder
6833763 7300 98884 0... (2 Replies)
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thanks. (14 Replies)
Discussion started by: orange47
14 Replies
LEARN ABOUT CENTOS
synos
synos(1) Mail Avenger 0.8.3 synos(1)NAME
synos - guess operating system from TCP SYN fingerprint
SYNOPSIS
synos [--mtu mtu] [--db path] syn-fingerprint
DESCRIPTION
synos takes a SYN fingerprint, in the format described for the CLIENT_SYNFP environment variable in the avenger(1) man page, and outputs a
guess as to the type of the client operating system. synos makes use of the OpenBSD SYN fingerprint database (which is also repackaged
with Mail Avenger).
OPTIONS
--mtu val
Certain operating systems set the initial TCP window size based on the maximum transmission unit, or MTU, of the network. For such
operating systems, synos usually checks the window size using both the client's MSS option plus 40 bytes (for TCP and IP headers), or a
hard-coded MTU, which defaults to 1,500 bytes. If either value works, the fingerprint is considered to match the operating system.
You can change the value 1,500 by specifying this option. A value of 0 tells synos to use only the value derived from the MSS option.
--db file
Specifies an alternate location for the SYN fingerprint database.
FILES
/usr/local/share/pf.os
Default location of SYN fingerprint database.
SEE ALSO avenger(1), asmtpd(8)
The Mail Avenger home page: <http://www.mailavenger.org/>.
The OpenBSD home page: <http://www.openbsd.org/>.
BUGS
The operating system type is determined by heuristics that are not always reliable. Moreover, not all operating systems can be
distinguished. The database may not even contain a client's particular operating system and version.
It is not hard to fool synos deliberately by changing TCP socket options or injecting raw packets onto the network.
AUTHOR
David Mazieres
Mail Avenger 0.8.3 2012-04-05 synos(1)