ttl | 易学教程

计算机网络实验设计-基于IP多广播的网络会议程序

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基于IP多广播的网络会议程序一．设计题目 Tracert 与Ping 程序设计与实现二．设计内容参照附录 2，了解 Tracert 程序的实现原理，并调试通过。然后参考 Tracert 程序和教材 4.4.2 节，编写一个 Ping 程序，并能测试本局域网的所有机器是否在线。三．设计步骤首先我们要明白tracert是什么，Tracert（跟踪路由）是路由跟踪实用程序，用于确定 IP 数据包访问目标所采取的路径。Tracert 命令用 IP 生存时间 (TTL) 字段和 ICMP 错误消息来确定从一个主机到网络上其他主机的路由。 Tracert原理：通过向目标发送不同IP生存时间 (TTL) 值的“Internet控制消息协议 (ICMP)”回应数据包，Tracert诊断程序确定到目标所采取的路由。要求路径上的每个路由器在转发数据包之前至少将数据包上的 TTL 递减 1。数据包上的 TTL 减为 0 时，路由器应该将“ICMP 已超时”的消息发回源系统。 Tracert 先发送 TTL 为 1 的回应数据包，并在随后的每次发送过程将TTL递增 1，直到目标响应或 TTL 达到最大值，从而确定路由。通过检查中间路由器发回的“ICMP 已超时”的消息确定路由。某些路由器不经询问直接丢弃 TTL 过期的数据包，这在 Tracert 实用程序中看不到。

TTL elastic search not working

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问题 I need to put a TTL with each of the logs exported from logstash. I have already created a folder 'mappings' under the config folder, under which I have a folder _default, under which I have the json file default .json, which has: { "_default_" : { "_ttl" : { "enabled" : true, "default" : "10s" } } } I am exporting my logs to elastic server with logstash. THe config file is: input { stdin { type => "stdin-type" } } filter { grok { type => "stdin-type" pattern => "I am %{USERNAME:username}"

Getting TTL of incoming UDP packet in Python

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问题 I'm using the socket module in Python to do some basic UDP client-server communication. What I would need to do is quite simple: client sends server a packet, server answers with client's public ip address, port and a number representing the TTL the UDP packet had when it got to the server. This is my main problem: is there any way to recieve a packet with recvfrom() or so, and read the TTL value it had when it reached my server? Thank you very much! Matteo Monti 回答1: I think you want to

Cassandra Timing out because of TTL expiration

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问题 Im using a DataStax Community v 2.1.2-1 (AMI v 2.5) with preinstalled default settings+ increased read time out to 10sec here is the issue create table simplenotification_ttl ( user_id varchar, real_time timestamp, insert_time timeuuid, read boolean, msg varchar, PRIMARY KEY (user_id, real_time, insert_time)); Insert Query: insert into simplenotification_ttl (user_id, real_time, insert_time, read) values ('test_3',14401440123, now(),false) using TTL 800; For same 'test_3' I inserted 33,000

Apply TTL in column level

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问题 Want to know, how to apply TTL in column level. below query set the TTL at record level INSERT INTO excelsior.clicks ( userid, url, date, name) VALUES ( 3715e600-2eb0-11e2-81c1-0800200c9a66, 'http://apache.org', '2013-10-09', 'Mary' ) USING TTL 86400; whereas my requirement is setting TTL for a particular column. Is there any way to achieve this 回答1: You can do an INSERT with partial data: cqlsh> create KEYSPACE test WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};

How to modify the TTL of all records set with a ttl of -1 in aerospike?

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问题 I want to modify the TTL of all the records that were accidentally set with a 'never expire' TTL (-1 in the client). How would I do that? 回答1: Just to clarify, setting a TTL of -1 in the client means never expire (equivalent to a default-ttl of 0 in the server's aerospike.conf file), while setting a TTL of 0 in the client means inherit the default-ttl for this namespace . With Predicate Filtering: If you're using the Java, C, C# and Go clients the easiest way to identify the records with a

not getting all ICMP time-exceeded messages: why?

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问题 I'm using Scapy to replay some dumped packets in which I change the TTL value. I've been getting very odd results even with TTL=1. When I run my test hours apart from each other, I can get from roughly 40% to 95% of packets replied to with an ICMP time-exceeded message. Then I can recursively replay unanswered packets and get each time more or less the same percentage of answered packets as before. Why is that? I've been sending packets with an interval of 0.1 seconds between each other. This

Messages with expiration are not removed from RabbitMQ

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问题 I am sending a normal message through a producer to RabbitMQ and then I send a second message with the expiration attribute assigned to a value. Then using the rabbitmqctl list_queues command I monitor the status of the messages. I found that if I send a normal message first and then a message with expiration , the rabbitmqctl list_queues is always showing me 2 messages pending on the queue. When I consume them, I get only one. On the other hand if I send just 1 message with expiration , in

Cassandra “default_time_to_live” property is not deleting data

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问题 I've created a table like: CREATE TABLE IF NOT EXISTS metrics_second( timestamp timestamp, value counter, PRIMARY KEY ((timestamp)) ) WITH default_time_to_live=1; And inserted some data like: UPDATE metrics_second SET value = value + 1 WHERE timestamp = '2015-01-22 17:43:55-0800'; When executing SELECT * FROM metrics_second I always see the data, even after a minute or so, although the default_time_to_live property of the table is set to one second. Why is that? 回答1: As @RussS confirmed,

TTL vs default_time_to_live which one is better and why?

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问题 Requirement is simple: we have to create a table which will have only 24 hours of data. We have two options Defile TTL with each insert Make table property default_time_to_live for 24 hours. I have general idea about both the things but internally which one will be helpful to deal with tombstones? or both will generate same amount of tombstones? Which one will be better and why any reference link will be appreciated. 回答1: If a table has default_time_to_live on it then rows that exceed this