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Questions tagged [anycast]

48 questions
120
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4 answers

What is the difference between unicast, anycast, broadcast and multicast traffic?

I have never had the privilege of working in an environment that required complicated routing or if it did require it, it was handled upstream of me. I've always used very simple static routing configurations and never needed to do any multipath…
user62491
90
votes
8 answers

What is "anycast" and how is it helpful?

I'd never heard of anycast until a few seconds ago when I read "What are some cool or useful server/networking tricks?". The wikipedia "Anycast" article on it is quite formal and doesn't really evoke a mental picture of how it would be used. Can…
username
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80
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11 answers

Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not good for high availability. When 1 IP goes down…
Valentino Miazzo
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32
votes
9 answers

What's the piece of hardware listening on Facebook's or Wikipedia's IP address?

I am trying to understand how massive sites like Facebook or Wikipedia work, for my intellectual curiosity. I read about various techniques for building scalable sites, but I am still puzzled about one particular detail. The part that confuses me is…
Igor Ostrovsky
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22
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3 answers

What is needed to use anycast IPs?

So, there're a bunch of questions on SF about the uses and how anycast IPs are cool. My approach is something more practical. What specifically I need to have to use one of those addresses? Do I need to be an AS (Autonomous System)? If I want to…
coredump
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21
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3 answers

What is the difference between Anycast and GeoDNS / GeoIP wrt HA?

Based on the Wikipedia description of Anycast, it includes both the distribution of a domain-name-to-many-IP-mapping across many DNS servers as well as replying to clients with the most geographically close (or fastest) server. In the context of a…
Riyad Kalla
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11
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3 answers

If public IPs are pinned to a single AS, how does BGP anycast work?

It is my understanding that public IP blocks are assigned from IANA, which assigns sub-blocks to RIRs, which assigns sub-blocks to ISPs, which assigns sub-blocks to individual ASs as outlined in this question: How are IP addresses actually…
turtlemonvh
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11
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3 answers

How do I get anycast for my servers?

I want to have anycast for my web service, but I cannot find any information on how to achieve this or any company that can help. I've found loads of companies offering anycast DNS, but that's not what I need. I have a stateless web service that I…
Filip Haglund
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10
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3 answers

How does anycast work with tcp?

TCP, being stateful, should require subsequent packets to reach the same server. (Stateless) HTTP runs on top of TCP, and CDN's can use anycast. So how does TCP work with anycast? What if the syn and the ack go to different servers? I think I've…
Filip Haglund
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9
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3 answers

How do big companies like Youtube load balance traffic with only one IP?

Examining the A records for youtube.com (for example), I see only one IP address. How can this be possible, given the volume of traffic they handle? Do they use anycast with load balancers behind it?
Victor Lft
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9
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3 answers

DNS servers already use anycast. Will adding more IPs enhance scalability?

RFC 1034 requires us to assign at least two IP addresses for DNS servers. However, redundancy can already be achieved by a single IP address if we use anycast addressing. BGP anycast seems to scale well into hundreds or even thousands of servers. If…
Pacerier
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9
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1 answer

Is there a way to set up Avahi to implement "anycast name resolution" on a LAN?

First, some background: We've got a lab containing a handful of dedicated Linux servers that run on an isolated LAN. All the servers run the same OS (Debian Linux) and the same proprietary server software, and the server processes communicate with…
Jeremy Friesner
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8
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2 answers

How to determine IP address is unicast or anycast?

I searched the Internet and unable to find an answer. Anyone can help?
John Wong
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5
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3 answers

Practical Anycast

I've read How can I send visitors to the closest server using DNS? post, but there's still some thing, on a practical level that I don't understand. Say I have two servers. One in NY another in Paris. Both of them have different IP adresses 1.1.1.1,…
Daniel
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4
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1 answer

Anycast network - steps required to implement one?

As part of our cloud-based security service, we have a DNS server deployed in the cloud. Instead of providing different IPs to customers in different geo-locations, we want to use a unified Anycast network that can provide the myriad benefits of…
Vinay
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