光纤到底要不要改MTU，MSS？

ntjxad · 发表于 2005-5-17 20:54:39

这招要试用一下,先顶一下

fjingxu · 发表于 2005-5-17 21:26:36

E:\>ping www.163.com -f -l 1453Pinging www.cache.split.netease.com [202.106.168.104] with 1453 bytes of data:Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0msE:\>ping www.163.com -f -l 1452Pinging www.cache.split.netease.com [202.106.168.104] with 1452 bytes of data:Reply from 202.106.168.104: bytes=1452 time=140ms TTL=53Reply from 202.106.168.104: bytes=1452 time=150ms TTL=53Reply from 202.106.168.104: bytes=1452 time=210ms TTL=53Reply from 202.106.168.104: bytes=1452 time=170ms TTL=53Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),Approximate round trip times in milli-seconds: Minimum = 140ms, Maximum = 210ms, Average = 167msE:\>

parphy · 发表于 2005-5-17 21:53:53

QUOTE (fjingxu @ May 17 2005, 09:26 PM)
E:\>ping www.163.com -f -l 1453Pinging www.cache.split.netease.com [202.106.168.104] with 1453 bytes of data:Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0msE:\>ping www.163.com -f -l 1452Pinging www.cache.split.netease.com [202.106.168.104] with 1452 bytes of data:Reply from 202.106.168.104: bytes=1452 time=140ms TTL=53Reply from 202.106.168.104: bytes=1452 time=150ms TTL=53Reply from 202.106.168.104: bytes=1452 time=210ms TTL=53Reply from 202.106.168.104: bytes=1452 time=170ms TTL=53Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),Approximate round trip times in milli-seconds: Minimum = 140ms, Maximum = 210ms, Average = 167msE:\>
结论就是MSS=1452-40=1412不过那代表的是到www.163.com的，未必是ISP给你封装的，最好测试隔一个的路由器

parphy · 发表于 2005-5-17 21:59:59

补充一下，PPPOE是L2的，一般不能过路由器，因此通常PING隔一跳的路由器，就知道ISP给你怎样封装的，就可以确定你的MSS了

砂瀑 · 发表于 2005-5-19 01:30:28

QUOTE (parphy @ May 17 2005, 09:53 PM)

QUOTE (fjingxu @ May 17 2005, 09:26 PM)
E:\>ping www.163.com -f -l 1453Pinging www.cache.split.netease.com [202.106.168.104] with 1453 bytes of data:Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Packet needs to be fragmented but DF set.Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum =  0ms, Average =  0msE:\>ping www.163.com -f -l 1452Pinging www.cache.split.netease.com [202.106.168.104] with 1452 bytes of data:Reply from 202.106.168.104: bytes=1452 time=140ms TTL=53Reply from 202.106.168.104: bytes=1452 time=150ms TTL=53Reply from 202.106.168.104: bytes=1452 time=210ms TTL=53Reply from 202.106.168.104: bytes=1452 time=170ms TTL=53Ping statistics for 202.106.168.104: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),Approximate round trip times in milli-seconds: Minimum = 140ms, Maximum =  210ms, Average =  167msE:\>
结论就是MSS=1452-40=1412不过那代表的是到www.163.com的，未必是ISP给你封装的，最好测试隔一个的路由器
  错应该是1452+28-40 =1440

parphy · 发表于 2005-5-19 08:55:12

楼上说的对，我把28包头给忘了，哈哈IP 包头的大小为 20 字节，ICMP Echo 消息的 ICMP 包头为 8 字节

ntjxad · 发表于 2005-5-19 14:34:59

QUOTE (parphy @ May 17 2005, 09:59 PM)
补充一下，PPPOE是L2的，一般不能过路由器，因此通常PING隔一跳的路由器，就知道ISP给你怎样封装的，就可以确定你的MSS了
请问如何才能找到一跳的地址?

parphy · 发表于 2005-5-19 16:08:31

c:\>tracert www.sian.com.cnTracing route to www.sian.com.cn [218.30.114.195]over a maximum of 30 hops: 1

一路风尘 · 发表于 2005-5-20 00:51:34

QUOTE (parphy @ May 19 2005, 04:08 PM)
c:\>tracert www.sian.com.cnTracing route to www.sian.com.cn [218.30.114.195]over a maximum of 30 hops: 1

parphy · 发表于 2005-5-20 07:40:49

是的不过，ISP关了ICMP，还能PING通，超强

一路风尘 · 发表于 2005-5-21 21:03:32

QUOTE (parphy @ May 20 2005, 07:40 AM)
是的不过，ISP关了ICMP，还能PING通，超强
打错，都是PING不通的。

藤真 · 发表于 2008-3-17 17:09:54

我以前也是一直认为光纤不用改MTU和MSS 但是今天我遇到个问题，就是我访问www.yahoo.com的时候根本都打不开，其实的网站都很正常，于是就查了一下，光纤也要设置这个MTU和MSS的，我用ping 202.96.134.134 -f -l 1472 得到我的MTU值为1472 于是改了外网网卡的MTU值为1472 ，但是yahoo还是打不开，于就是在防火中加了一个改MSS值的规则改MMS值为1460 后 www.yahoo.com 打开了，谢谢你们的讨论mss=mtu+28-40我现在才清楚的知道了。。。

[ 本帖最后由藤真于 2008-3-17 17:33 编辑 ]

power6 · 发表于 2009-2-25 21:50:57

我换了网卡感觉就不对了，是不是还要重新设呀！

xing122333 · 发表于 2009-2-25 21:54:04

我100M的光纤，MSS=1400

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