diff options
Diffstat (limited to 'Documentation/networking/ip-sysctl.txt')
| -rw-r--r-- | Documentation/networking/ip-sysctl.txt | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 3c5e465296e1..ac3b4a726a1a 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -11,7 +11,9 @@ ip_forward - BOOLEAN for routers) ip_default_ttl - INTEGER - default 64 + Default value of TTL field (Time To Live) for outgoing (but not + forwarded) IP packets. Should be between 1 and 255 inclusive. + Default: 64 (as recommended by RFC1700) ip_no_pmtu_disc - BOOLEAN Disable Path MTU Discovery. @@ -185,7 +187,7 @@ tcp_cookie_size - INTEGER tcp_dsack - BOOLEAN Allows TCP to send "duplicate" SACKs. -tcp_ecn - BOOLEAN +tcp_ecn - INTEGER Enable Explicit Congestion Notification (ECN) in TCP. ECN is only used when both ends of the TCP flow support it. It is useful to avoid losses due to congestion (when the bottleneck router supports @@ -708,10 +710,28 @@ igmp_max_memberships - INTEGER Change the maximum number of multicast groups we can subscribe to. Default: 20 -conf/interface/* changes special settings per interface (where "interface" is - the name of your network interface) -conf/all/* is special, changes the settings for all interfaces + Theoretical maximum value is bounded by having to send a membership + report in a single datagram (i.e. the report can't span multiple + datagrams, or risk confusing the switch and leaving groups you don't + intend to). + The number of supported groups 'M' is bounded by the number of group + report entries you can fit into a single datagram of 65535 bytes. + + M = 65536-sizeof (ip header)/(sizeof(Group record)) + + Group records are variable length, with a minimum of 12 bytes. + So net.ipv4.igmp_max_memberships should not be set higher than: + + (65536-24) / 12 = 5459 + + The value 5459 assumes no IP header options, so in practice + this number may be lower. + + conf/interface/* changes special settings per interface (where + "interface" is the name of your network interface) + + conf/all/* is special, changes the settings for all interfaces log_martians - BOOLEAN Log packets with impossible addresses to kernel log. |