Hi group:
I want to thank you all for the quick response.
The QUESTION was:
Is there a way I can find what the value of TTL is, particullary for telnet ?
Is there a dafault value for it ?. Is it possible to change it ? I am running
OSF/1 3.0.
Many thanks to:
Arnaud Valeix fnet_at_ifh.sncf.Fr
Pascal Pederiva pascal_at_zuo.dec.com
Arrigo Triulzi arrigo_at_lpac.ac.uk
Matt Thomas thomas_at_lkg.dec.com
Michael R. Kline mike_at_lib.utexas.edu
Thanks to this people I found that the default values for TCP TTL is 60
and for UDP is 30 (I am running OSF/1 3.0).
There are several ways to inspect the value for TTL (time-to-live):
1) In /usr/sys/include/netinet/inet_config.h there are two lines with the
dafault values for TTL:
int tcpttl; /* Default time to live (60) */
int udpttl; /* Default time to live (30) */
2) Using the Netconfig utility which you can get in
ftp://cs.ucsd.edu/pub/csl/Netconfig/netconfig2.3.tar.gz
Once you build it, you type the command with no arguments and
you get the following:
Sockets:
Max socket buffer size (_sb_max): 131072
Large mbuf use threshold (_mbufthreshold): 1024
Max listen queue len (_somaxconn): 8
IP:
Routing (_ipforwarding): 0
Ipgateway (_ipgateway): off
ICMP:
Redirects (_ipsendredirects): on
TCP:
Output Buffer Size (_tcp_sendspace): 32768
Input Buffer Size (_tcp_recvspace): 32768
Retransmit Threshold (_tcprexmtthresh): 3
Default Max Seg Size (_tcp_mssdflt): 536
Keepalive Idle Time (_tcp_keepidle): 14400
Keepalive Interval (_tcp_keepintvl): 150
Default TTL (_tcp_ttl): 60
Don't scale windows (_tcp_dont_winscale): off
Subnets Are Local (_subnetsarelocal): on
UDP:
Checksum (_udpcksum): on
Max Send Msg Size (_udp_sendspace): 9216
Max Rcv Buffer (_udp_recvspace): 41600
Default TTL (_udp_ttl): 30
TCP/IP Misc.:
Internet checksum routine active (_nocksum):off
3) The other way to examine tha values for TTL is by using the dbg.
Type as root:
dbx -k /vmunix
(dbx) print tcp_ttl
and you can also change the values by using something like:
(dbx) assign tcp_ttl = 128
(dbx) patch tcp_ttl = 130
Finally, I got this interesting comment about TTL:
>
>As the worldwide Internet grows the number of routers keeps
>increasing, which increases the total hop count (number of router
>"hops") a packet must transit to get to its destination.
>
>This can be a problem since the Time To Live (TTL) value in the packet
>is decremented at each router hop. If the TTL value is 32 and there
>are 40 routers in the path to the destination, then the packet will be
>discarded when the TTL reaches zero and won't make it to the
>destination.
>
>The following web page lists common TTL values in various operating
>systems along with tools that can be used to increase the size of the
>TTL value.
>
>http://www.switch.ch/switch/docs/ttl_default.html
>
>-Charles
>
>-
>Charles Spurgeon
>c.spurgeon_at_mail.utexas.edu
>512.475.9265
>
>
Anyone with interest about TTL values should take a look to the document:
http://www.switch.ch/switch/docs/ttl_default.html
This document has a comment about the default values for TTL in OSF/1, it says:
OSF/1 3.2A
TCP TTL is 60 but UDP has too low TTL of 30. Modification of TCP/IP stack
parameters can be made with netconfig2.3
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Received on Tue Jan 16 1996 - 21:11:48 NZDT