我想测量本地时钟和
运行 NTP 服务器的远程处理器。
我可以获得响应的 tx_time,如下所示,但更好的估计将包括对网络延迟的一些估计。 NTP 响应消息中还应使用其他字段。
import ntplib
from time import ctime,time
addr_remote = '128.128.204.207'
c = ntplib.NTPClient()
remote = c.request(addr_remote)
local = time()
print("REMOTE: " + ctime(remote.tx_time) + " <reference clock> ")
print("LOCAL: " + ctime(local) + " delta: " + str(local - remote.tx_time ))
如果我看“远程”:
for attr in dir(remote):
print("remote.%s = %r" % (attr, getattr(remote, attr)))
I see:
remote.delay = 0.0
remote.dest_time = 1531863145.9309998
remote.dest_timestamp = 3740851945.9309998
remote.from_data = <bound method NTPPacket.from_data of <ntplib.NTPStats object at 0x000000000265B2E8>>
remote.leap = 0
remote.mode = 4
remote.offset = -1.8789582252502441
remote.orig_time = 1531863145.9309998
remote.orig_timestamp = 3740851945.9309998
remote.poll = 0
remote.precision = -7
remote.recv_time = 1531863144.0520415
remote.recv_timestamp = 3740851944.0520415
remote.ref_id = 0
remote.ref_time = 0.0
remote.ref_timestamp = 2208988800.0
remote.root_delay = 0.0
remote.root_dispersion = 0.0
remote.stratum = 9
remote.to_data = <bound method NTPPacket.to_data of <ntplib.NTPStats object at 0x000000000265B2E8>>
remote.tx_time = 1531863144.0520415
remote.tx_timestamp = 3740851944.0520415
那么,我该如何使用这些:
消除网络延迟并更好地估计时钟差异?
NTP 客户端发送包含本地时间的数据包orig_time
,NTP 服务器在服务器时间接收到的recv_time
。然后服务器在服务器时间回复tx_time
客户端在当地时间收到回复dest_time
.
往返行程delay
计算为recv_time - orig_time + dest_time - tx_time
,时钟之间的偏移是offset = (recv_time - orig_time + tx_time - dest_time) / 2
.
假设两个 NTP 数据包采用一致的路径,则正确的调整时间很简单dest_time + offset
,这相当于tx_time + delay/2
.
本文内容由网友自发贡献,版权归原作者所有,本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容,请联系:hwhale#tublm.com(使用前将#替换为@)