网络工程 - 为什么 traceroute 为使用的不同协议提供不同的跃点数？ - 吾爱随笔录

在使用不同协议探索 traceroute 时，它给了我以下响应：

对于 TCP：

user@200411DC0:~$ sudo traceroute -T facebook.com
traceroute to facebook.com (157.240.16.35), 30 hops max, 60 byte packets
 1  10.0.24.2 (10.0.24.2)  1.717 ms  1.839 ms  1.991 ms
 2  edge-star-mini-shv-01-bom1.facebook.com (157.240.16.35)  0.200 ms  0.225 ms  0.225 ms

对于 ICMP：

user@200411DC0:~$ sudo traceroute -I facebook.com
traceroute to facebook.com (157.240.16.35), 30 hops max, 60 byte packets
 1  10.0.24.2 (10.0.24.2)  0.752 ms  0.842 ms  1.002 ms
 2  10.0.20.30 (10.0.20.30)  0.905 ms *  0.906 ms
 3  182.19.61.58 (182.19.61.58)  3.459 ms  3.468 ms  3.911 ms
 4  182.19.106.103 (182.19.106.103)  29.733 ms  29.375 ms  29.393 ms
 5  ae41.pr01.bom1.tfbnw.net (103.4.99.20)  30.119 ms  30.576 ms  30.545 ms
 6  157.240.40.229 (157.240.40.229)  30.089 ms  29.540 ms  29.514 ms
 7  173.252.67.117 (173.252.67.117)  29.244 ms  29.260 ms  28.869 ms
 8  edge-star-mini-shv-01-bom1.facebook.com (157.240.16.35)  28.978 ms  30.854 ms  30.523 ms

正常跟踪路由 (UDP)：

user@200411DC0:~$ sudo traceroute facebook.com
traceroute to facebook.com (157.240.16.35), 30 hops max, 60 byte packets
 1  10.0.24.2 (10.0.24.2)  0.709 ms  0.849 ms  0.989 ms
 2  10.0.20.30 (10.0.20.30)  0.592 ms  1.083 ms  1.082 ms
 3  182.19.61.58 (182.19.61.58)  7.468 ms  7.487 ms  7.988 ms
 4  182.19.106.103 (182.19.106.103)  29.952 ms  29.969 ms  30.641 ms
 5  ae41.pr01.bom1.tfbnw.net (103.4.99.20)  46.561 ms  46.580 ms  47.507 ms
 6  po101.psw02.bom1.tfbnw.net (157.240.33.239)  31.415 ms  31.164 ms 157.240.40.229 (157.240.40.229)  30.246 ms
 7  173.252.67.85 (173.252.67.85)  29.516 ms 173.252.67.59 (173.252.67.59)  29.732 ms 173.252.67.121 (173.252.67.121)  29.985 ms
 8  * * *
 9  * * *
10  * * *
11  * * *
12  * * *
13  * * *
14  * * *
15  * * *
16  * * *
17  * * *
18  * * *
19  * * *
20  * * *
21  * * *
22  * * *
23  * * *
24  * * *
25  * * *
26  * * *
27  * * *
28  * * *
29  * * *
30  * * *
user@200411DC0:~$

有人可以解释结果的差异以及输出中的 * 吗？