Update socket_setttl_ttl.md

dgram/socket_setttl_ttl.md

@@ -4,12 +4,9 @@ added: v0.1.101
 
 * `ttl` {number} Integer
 
-Sets the `IP_TTL` socket option. While TTL generally stands for "Time to Live",
-in this context it specifies the number of IP hops that a packet is allowed to
-travel through.  Each router or gateway that forwards a packet decrements the
-TTL.  If the TTL is decremented to 0 by a router, it will not be forwarded.
-Changing TTL values is typically done for network probes or when multicasting.
-
-The argument to `socket.setTTL()` is a number of hops between 1 and 255.
-The default on most systems is 64 but can vary.
+设置 `IP_TTL` 套接字选项。
+一般来说，TTL表示"生存时间"，这里特指一个IP数据包传输时允许的最大跳步数。
+当IP数据包每向前经过一个路由或网关时，TTL值减1，若经过某个路由时，TTL值被减至0，便不再继续向前传输。
+比较有代表性的是，为了进行网络情况嗅探或者多播而修改TTL值。
 
+传给 `socket.setTTL()` 的参数是一个范围为0-255的跳步数。大多数系统的默认值是 `1` ，但是可以变化。