DNS server
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... DNS based Request-Routing
techniques, a specialized DNS server is inserted in the DNS
resolution process. The server is capable of returning a different
...
... domain or a sub domain. The DNS server returns the IP address of the
best surrogate in an A record ...
... IP address of the
best surrogate in an A record to the requesting DNS server. The IP
address of the surrogate could also be a virtual IP(VIP) address ...
...
In this approach, the Request-Routing DNS server returns multiple
replies such as several A records for various surrogates. Common
...
... A records for various surrogates. Common
implementations of client site DNS server's cycles through the
multiple replies in a Round-Robin fashion. The order in which the
...
...
In this approach multiple Request-Routing DNS servers can be involved
in a single DNS resolution. The rationale of utilizing multiple
...
... DNS resolution. The rationale of utilizing multiple
Request-Routing DNS servers in a single DNS resolution is to allow
one to distribute more complex decisions from a single server ...
... single server to
multiple, more specialized, Request-Routing DNS servers. The most
common mechanisms used to insert multiple Request-Routing DNS servers ...
... DNS servers. The most
common mechanisms used to insert multiple Request-Routing DNS servers
in a single DNS resolution is the use of NS ...
... NS and CNAME records. An
example would be the case where a higher level DNS server operates
within a territory, directing the DNS lookup to a more specific DNS
server ...
... DNS server operates
within a territory, directing the DNS lookup to a more specific DNS
server within that territory to provide a more accurate resolution.
...
... level domain to another Request-Routing DNS server. The, technique
allows multiple DNS server to be involved in the name resolution
...
... Routing DNS server. The, technique
allows multiple DNS server to be involved in the name resolution
process. For example, a client site DNS server ...
... DNS server to be involved in the name resolution
process. For example, a client site DNS server resolving
a.b.example.com [10] would eventually request a resolution of
...
... Routing NS server. In this case the Request-Routing DNS
server can either return a set of A records or can redirect the
resolution of the request a.b.example.com to the DNS server ...
... DNS
server can either return a set of A records or can redirect the
resolution of the request a.b.example.com to the DNS server that is
authoritative for example.com using NS records.
...
... NS records is that the number of
Request-Routing DNS servers are limited by the number of parts in the
DNS name. This problem results from DNS ...
... DNS policy that causes a client
site DNS server to abandon a request if no additional parts of the
DNS name are resolved in an exchange with an authoritative DNS
server ...
... DNS server to abandon a request if no additional parts of the
DNS name are resolved in an exchange with an authoritative DNS
server.
A second drawback is that the last DNS server ...
... DNS
server.
A second drawback is that the last DNS server can determine the TTL
of the entire resolution process. Basically, the last DNS server ...
... DNS server can determine the TTL
of the entire resolution process. Basically, the last DNS server can
return in the authoritative section of its response its own NS
...
... security reasons. Another drawback is
the added delay in resolving the request due to the use of multiple
DNS servers.
...
...
In this scenario, the Request-Routing DNS server returns a CNAME
record to direct resolution to an entirely new domain ...
... the new domain might employ a new set of Request-Routing DNS servers.
One disadvantage of this approach is the additional overhead ...
... domain name. The main advantage of this approach
is that the number of Request-Routing DNS servers is independent of
the format of the domain name.
...
... Furthermore, to combine measurement and redirection, the
Request-Routing DNS server can advertise an anycast address as its IP
address. The same address ...
... IP
address. The same address is used by multiple physical DNS servers.
In this scenario, the Request-Routing DNS server ...
... DNS servers.
In this scenario, the Request-Routing DNS server that is the closest
to the client site DNS server ...
... DNS server that is the closest
to the client site DNS server in terms of OSPF and BGP routing will
...
... Drawbacks of this approach are listed below:
o The DNS server may not be the closest server in terms of routing
to the client ...
... available at resolution time. The disadvantage is that the client
site DNS server has to perform multiple resolutions to retrieve a
single Web page, which might increase rather than decrease the
overall latency ...
... may be needed in order to be able to react quickly in the face of
outages. This in return may increase the volume of requests to
DNS servers.
o Some DNS ...
... DNS Request-Routing is based only on knowledge of the client DNS
server, as client addresses are not relayed within DNS ...
... client's proximity to the surrogate.
o DNS servers can request and allow recursive resolution of DNS
names. For recursive resolution of requests, the Request-Routing
...
... DNS
names. For recursive resolution of requests, the Request-Routing
DNS server will not be exposed to the IP address of the client's
...
... site DNS server. In this case, the Request-Routing DNS server
will be exposed to the address of the DNS server ...
... DNS server
will be exposed to the address of the DNS server that is
recursively requesting the information on behalf of the client's
...
... recursively requesting the information on behalf of the client's
site DNS server. For example, imgs.example.com might be resolved
by a CN ...
...
o Users that share a single client site DNS server will be
redirected to the same set of IP addresses during the TTL ...
... limitations. For example, the use of such techniques can overburden
third party DNS servers, which should not be allowed [19]. In [11]
...
... Routing system, the
measurements are made to the client's local DNS server. However,
when the IP address of the client ...