Chapter 9: Domain Name System (DNS) and Amazon Route 53
- C. An AAAA record is used to route traffic to an IPv6 address, whereas an A record is used to route traffic to an IPv4 address.
- AAAA record是為ipv6設(shè)置的
- A record 是為ipv4準(zhǔn)備的
- B. Domain names are registered with a domain registrar, which then registers the name
to InterNIC.
- 域名注冊商提供域名注冊服務(wù)斟叼；
- C. You should route your traffic based on where your end users are located. The best
routing policy to achieve this is geolocation routing.
- 如果按照位置訪問尉咕，最好的 route policy就是 geolocation routing
- routing policy：
- Simple—Most commonly used when you have a single resource that performs a given
function for your domain - Weighted—Used when you want to route a percentage of your traffic to one particular
resource or resources - Latency-Based—Used to route your traffic based on the lowest latency so that your
users get the fastest response times - Failover—Used for DR and to route your traffic from your resources in a primary
location to a standby location - Geolocation—Used to route your traffic based on your end user’s location
- D. A PTR record is used to resolve an IP address to a domain name, and it is commonly referred to as “reverse DNS.”
- PTR record用來解析IP地址到域名，或者稱作 reverse DNS
- B. You want your users to have the fastest network access possible. To do this, you would use latency-based routing. Geolocation routing would not achieve this as well as latency based routing, which is specifically geared toward measuring the latency and thus would direct you to the AWS region in which you would have the lowest latency.
- geolocation policy無法保證低延遲，直接使用低延遲策略，會將最低延遲的服務(wù)路由給客戶；
- C. You would use Mail eXchange (MX) records to define which inbound destination mail
server should be used.
- MX records是郵件交換服務(wù)用的；
- B. SPF records are used to verify authorized senders of mail from your domain.
- SPF records是反垃圾郵件的records；
- B. Weighted routing would best achieve this objective because it allows you to specify
which percentage of traffic is directed to each endpoint.
- 基于權(quán)重的路由策略可以將流量按照比重分流到不同的服務(wù)區(qū)域骂束；
- D. The start of a zone is defined by the SOA; therefore, all zones must have an SOA
record by default.
- SOA records是默認(rèn)的區(qū)域的默認(rèn)records（start of authority record),）
- D. Failover-based routing would best achieve this objective.
- 容災(zāi)只用使用failover的路由策略；
- B. The CNAME record maps a name to another name. It should be used only when there are no other records on that name.
- cname records可以將域名指向另外一個域名成箫；
- C. Amazon Route 53 performs three main functions: domain registration, DNS service,
and health checking.
- R53支持三個主要功能：域名注冊展箱、DNS解析和健康檢查，不支持負(fù)載均衡５挪混驰！
- A. A TXT record is used to store arbitrary and unformatted text with a host.
- txt record從來存儲域名的描述信息；
- C. The resource record sets contained in a hosted zone must share the same suffix.
- 一個域名zone內(nèi)必須是后綴相同皂贩；
- B. DNS uses port number 53 to serve requests.
- DNS解析用的端口是53
- D. DNS primarily uses UDP to serve requests.
- DNS解析主要是UDP協(xié)議
- A. The TCP protocol is used by DNS server when the response data size exceeds 512 bytes or for tasks such as zone transfers.
- TCP協(xié)議被啟用返回請求栖榨，當(dāng)數(shù)據(jù)大于512B
- B. Using Amazon Route 53, you can create two types of hosted zones: public hosted
zones and private hosted zones.
- 使用R53你可以創(chuàng)建公網(wǎng)域名和內(nèi)網(wǎng)域名；
- D. Amazon Route 53 can route queries to a variety of AWS resources such as an Amazon CloudFront distribution, an Elastic Load Balancing load balancer, an Amazon EC2 instance, a website hosted in an Amazon S3 bucket, and an Amazon Relational Database (Amazon RDS).
- R53是沒法把請求轉(zhuǎn)發(fā)到一個解決方案明刷。智能轉(zhuǎn)發(fā)到具體的端口服務(wù)商婴栽；
- D. You must first transfer the existing domain registration from another registrar to
Amazon Route 53 to configure it as your DNS service.
- 只有將域名轉(zhuǎn)移到R53，才能使用后續(xù)的R53服務(wù)辈末；
知識點(diǎn)總結(jié)
Understand what DNS is. DNS is the methodology that computers use to convert humanfriendly domain names (for example, amazon.com) into IP addresses (such as 192.0.2.1).
理解什么是DNS愚争。DNS是計(jì)算機(jī)將域名轉(zhuǎn)換成IP服務(wù)映皆；
Know how DNS registration works. Domains are registered with domain registrars that
in turn register the domain name with InterNIC, a service of ICANN. ICANN enforces
uniqueness of domain names across the Internet. Each domain name becomes registered in a central database known as the WhoIS database. Domains are defined by their TLDs. TLDs are controlled by IANA in a root zone database, which is essentially a database of all available TLDs.了解DNS的注冊工作。域名是通過域名注冊商在interNIC注冊准脂，是ICANN的一種服務(wù)劫扒。ICANN強(qiáng)制保持互聯(lián)網(wǎng)上域名的一致性檬洞。每個域名被注冊到一個WhoIS的數(shù)據(jù)庫狸膏。域名在ICANN在root zone數(shù)據(jù)庫中設(shè)置TLD。
Remember the steps involved in DNS resolution. Your browser asks the resolving DNS
server what the IP address is for amazon.com. The resolving server does not know the address, so it asks a root server the same question. There are 13 root servers around the world, and these are managed by ICANN. The root server replies that it does not know the answer to this, but it can give an address to a TLD server that knows about .com domain names. The resolving server then contacts the TLD server. The TLD server does not know the address of the domain name either, but it does know the address of the resolving name server. The resolving server then queries the resolving name server. The resolving name server contains the authoritative records and sends these to the resolving server, which then saves these records locally so it does not have to perform these steps again in the near future. The resolving name server returns this information to the user’s web browser, which also caches the information.記得DNS解析的過程添怔。瀏覽器請求DNS服務(wù)器amazon.com的IP地址是多少湾戳。解析服務(wù)器不知道IP地址，所以他咨詢root server广料。ICANN管理的全世界的13個root server砾脑，他們來識別域名對應(yīng)的域名，如果他識別不了艾杏，他將請求轉(zhuǎn)發(fā)給TLD服務(wù)器韧衣，TLD服務(wù)器也不知道域名地址，但是他知道解析域名的服務(wù)器购桑，這個解析服務(wù)查詢解析域名的服務(wù)器畅铭，這個服務(wù)器包含官方的解析記錄并返回。然后解析服務(wù)器在本地保存以規(guī)避后續(xù)再次請求解析勃蜘。本次瀏覽器將此次解析也進(jìn)行cache保存硕噩。
Remember the different record types. DNS consists of the following different record
types: A (address record), AAAA (IPv6 address record), CNAME (canonical name record or alias), MX (mail exchange record), NS (name server record), PTR (pointer record), SOA (start of authority record), SPF (sender policy framework), SRV (service locator), and TXT (text record). You should know the differences among each record type.理解不同的record type。
A：域名的IP地址缭贡；
AAAA：IPV6的地址記錄炉擅；
CNAME：別名或者稱作規(guī)范名稱；
MX：郵件服務(wù)器記錄
NS：name server
PTR：通過IP地址解析域名阳惹；可以稱作反向DNS解析谍失；
SOA：授權(quán)記錄的開始，每個域名解析默認(rèn)都有莹汤；
SPF：防垃圾郵件的策略框架快鱼；
SRV：服務(wù)資源記錄，描述哪個計(jì)算機(jī)提供了哪些服務(wù)体啰；
txt：服務(wù)器的文本描述攒巍；
Remember the different routing policies. With Amazon Route 53, you can have
different routing policies. The simple routing policy is most commonly used when you have a single resource that performs a given function for your domain. Weighted routing is used
when you want to route a percentage of your traffic to a particular resource or resources.
Latency-based routing is used to route your traffic based on the lowest latency so that your users get the fastest response times. Failover routing is used for DR and to route your traffic from a primary resource to a standby resource. Geolocation routing is used to route your traffic based on your end user’s location.理解不同的route 策略；
simple策略：是最通過的路由策略荒勇，將你的單一資源映射到一個特定的功能函數(shù)上柒莉；
weighted策略：當(dāng)你想將一定百分比的流量導(dǎo)向一個特定的資源；
latency-based策略：被用來將你的流量導(dǎo)向最低延遲的服務(wù)器沽翔；
failvoer策略：是將你的容災(zāi)服務(wù)器提供到你的主服務(wù)兢孝，作為standby窿凤；
Geolocation策略：被用來將你的流量基于終端用戶的位置進(jìn)行分發(fā)；
