<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
<br>
<br>
<br>
On 7/20/2011 1:15 AM, AMANI M. BIN SUWAIF wrote:
<blockquote cite="mid:4E266459.7070001@ies.etisalat.ae" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
Hi,<br>
<br>
The problem is that fail-over between A records is not standard
and might/might not work with various SIP clients. On the other
hand SRV in my opinion has been designed with that in mind, that's
why the additional complexity with 2 SRV records. <br>
<br>
<br>
<div class="moz-signature"> <font color="black" face="Georgia"
size="2">Thanks & Regards, </font><br>
<br>
<font color="darkgreen" face="Georgia" size="2"> <b>Amani</b></font><br>
<br>
<br>
<br>
</div>
On 7/20/2011 2:50 AM, Kevin Darcy wrote:
<blockquote cite="mid:4E260A45.7030107@chrysler.com" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<title></title>
On 7/18/2011 11:42 PM, AMANI MOHAMED BIN SUWAIF wrote:
<blockquote cite="mid:4E24FD36.6020702@ies.etisalat.ae"
type="cite">
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
Hi,<br>
<br>
I have the below scenario <br>
<br>
_TCP.EXAMPLE.COM IN SRV 10 0 5060
primary-sbg.example.com <br>
_TCP.EXAMPLE.COM IN SRV 20 0 5060
secondary-sbg.example.com <br>
<br>
I have 2 IP ranges and 2 SBGs host, my intention is <br>
<br>
for client in IP range1 <br>
primary-sbg IN A 1.1.1.1 <br>
secondary-sbg IN A 2.2.2.2 <br>
<br>
for client in IP range2 <br>
primary-sbg IN A 2.2.2.2 <br>
secondary-sbg IN A 1.1.1.1 <br>
<br>
can this be achieved without using a views? <br>
<br>
I thought this can be solved just by a sortlist, where <br>
primary-sbg IN A 1.1.1.1 <br>
primary-sbg IN A 2.2.2.2 <br>
secondary-sbg IN A 2.2.2.2 <br>
secondary-sbg IN A 1.1.1.1 <br>
<br>
and then introduce the sortlist, which sorts the position of
IP addresses based on the IP range client comes from? <br>
something like, <br>
<br>
sortlist { <br>
{ <br>
IPRANGE1; // 1st client IP selection matches any of
these <br>
{1.1.1.1; // return any of these response IPs as 1st
preference <br>
}; <br>
{ <br>
IPRANGE2; // 1st client IP selection matches any of
these <br>
{2.2.2.2; // return any of these response IPs as 1st
preference <br>
}; <br>
}; <br>
<br>
but in this case, <br>
client from IPRANGE1 receive 1.1.1.1 as a first choice for
both primary-sbg and secondary-sbg <br>
and <br>
client from IPRANGE2 receive 2.2.2.2 as a first choice for
both primary-sbg and secondary-sbg <br>
which is not the intention. sortlist doesn't not consider
domain name. <br>
The intention is to have primary SBG for first iprange act as
a secondary SBG for the second ip range and vice verse and in
similar manner for multiple IP ranges and SBGs. Problem with
views is that anytime this setup gets bigger and we will have
additional ip ranges and additional SBGs, it will require
additional views... <br>
<br>
(LOC)RANGE PRIMARY(LOC) SECONDARY(LOC) <br>
(L1)IPRANGE1 SBG1(L1) SBG6(L2) <br>
(L1)IPRANGE2 SBG2(L1) SBG7(L2) <br>
(L1)IPRANGE3 SBG3(L1) SBG8(L2) <br>
(L1)IPRANGE4 SBG4(L1) SBG9(L2) <br>
(L1)IPRANGE5 SBG5(L1) SBG10(L2) <br>
<br>
(L2)IPRANGE6 SBG6(L2) SBG1(L1) <br>
(L2)IPRANGE7 SBG7(L2) SBG2(L1) <br>
(L2)IPRANGE8 SBG8(L2) SBG3(L1) <br>
(L2)IPRANGE9 SBG9(L2) SBG4(L1) <br>
(L2)IPRANGE10 SBG10(L2) SBG5(L1) <br>
<br>
half of the SBGs is in one location (L1) and half in other
(L2), that's why it is important that for clients from ranges
in one location, first half of SBGs is preferred, and for
other clients from second location other half of SBGs is
preferred. Client configuration should be uniformed (same SRV)
regardless the location. <br>
</blockquote>
Are you over-engineering this? If the A-record failover by your
client is fast enough you might only need 1 SRV record, and then
sortlisting will work fine (subject to the usual caveats: as
long as you can control the sortlist config of every resolver
your clients will use, and keep them in sync).<br>
<br>
<br>
-
Kevin<br>
</blockquote>
</blockquote>
Well, you could always stand up some virtual IPs on the same servers
(or possibly NAT it upstream) and then perform some *fancy*
sortlisting, e.g.<br>
<br>
for clients in IP range1<br>
primary-sbg 1.1.1.1, 2.2.2.3<br>
secondary-sbg 2.2.2.2, 1.1.1.2<br>
<br>
for clients in IP range2<br>
primary-sbg 2.2.2.3, 1.1.1.1<br>
secondary-sbg 1.1.1.2, 2.2.2.2<br>
<br>
That way range1 clients would always fail over -- via SRV failover
or A-record failover -- from the 1.1.1.x server to the 2.2.2.x
server and range2 clients would always fail over from the 2.2.2.x
server to the 1.1.1.x server.<br>
<br>
Bear in mind that "view"s, i.e. giving different answers to the same
DNS query, depending on the client, is not something which is (as
far as I'm aware) sanctioned by the Internet Standards, but A-record
failover was specified as far back as RFC 1123 (1989):<br>
<br>
"2.3 Applications on Multihomed hosts<br>
<br>
When the remote host is multihomed, the name-to-address translation
will return a list of alternative IP addresses. As specified in
Section 6.1.3.4, this list should be in order of decreasing
preference. Application protocol implementations SHOULD be prepared
to try multiple addresses from the list until success is obtained.
More specific requirements for SMTP are given in Section 5.3.4.
"<br>
<br>
2.3 Applications on Multihomed hosts<br>
<br>
When the remote host is multihomed, the name-to-address<br>
translation will return a list of alternative IP addresses.
As<br>
specified in Section 6.1.3.4, this list should be in order of<br>
decreasing preference. Application protocol implementations<br>
SHOULD be prepared to try multiple addresses from the list
until<br>
success is obtained. More specific requirements for SMTP are<br>
given in Section 5.3.4.<br>
<br>
So if you're worried about what is "standard" and what isn't, you
should cast your lot with A-record failover and *not* any "view"
trickery.<br>
<br>
- Kevin<br>
<br>
<br>
</body>
</html>