Loss of DNS? in Leeds 4 times in the last 6 days

Originally Posted by monkeybreath

@ Viras- PM me the mac address of your modem and i'll have a look at what is going on with your connection tomorrow.

Viras - as a newcomer, you may not be aware, but MB does work for NTL and it's OK to PM him this info (but don't post it on the forum). Hopefully a mod will come along and confirm this.

[steveh]

Originally Posted by Paul M

What do you mean by a "DNS timeout" ?

The likes of:

> www.metafilter.com
Server: cache1.ntli.net
Address: 194.168.4.100

DNS request timed out.
timeout was 10 seconds.
DNS request timed out.
timeout was 10 seconds.
*** Request to cache1.ntli.net timed-out

Happening for a range of different sites - although possibly more for those with DNS hosted in the US.

[~Dan~]

My broswing was being a tad sluggish, so I just changed to a Manchester webcache and things seem to be flying now! If it doesn't stuff up again then it looks like it might have been the webcache.

[~Dan~]

Furthermore I'll add that whenever I turn off the proxy webcache I'm using, my default is ALWAYS leed-cache-9.server.ntli.net. Have ntl not heard of distributing the users across the different caches to spread the load?

[rdhw]

Originally Posted by ~Dan~

Furthermore I'll add that whenever I turn off the proxy webcache I'm using, my default is ALWAYS leed-cache-9.server.ntli.net. Have ntl not heard of distributing the users across the different caches to spread the load?

The load-spreading within the cluster is done by destination URL, not by user. So if you always use the same test site for identifying your proxy, you will always get the same answer. Each member of the cluster has its own little bit if the internet to cache, and your connection will utilise all members of the cluster according to the URL sought. It's more efficient that way.

[Matth]

Originally Posted by rdhw

The load-spreading within the cluster is done by destination URL, not by user. So if you always use the same test site for identifying your proxy, you will always get the same answer. Each member of the cluster has its own little bit if the internet to cache, and your connection will utilise all members of the cluster according to the URL sought. It's more efficient that way.

Absolutely! if the users of the same site were spread across all the caches, every cache would have to fetch a copy.

As for DNS timeout, I've seen my firewall catch attempts to issue ICMP destination unreachable, when the reply finally arrives too late to be any use.

If there's a way to tune this behaviour (in Win98SE), I've not found it yet.

What beats me, is that the address of NTL's email server (I might try plugging the ip address in directly) seems to be a victim as often as any remote address.

One thing which can disrupt DNS, is excessive load from firewall reverse DNS lookups (my firewall is set NOT to R-DNS every damn ping!, but many are).
That can magnify the normal DNS load by a huge margin.

[iadom]

Originally Posted by Matth

One thing which can disrupt DNS, is excessive load from firewall reverse DNS lookups (my firewall is set NOT to R-DNS every damn ping!, but many are).
That can magnify the normal DNS load by a huge margin.

Would this impinge on the network in general or my own PC ? The reason I ask is that I have a small problem that I suspect is DNS related.

My AV software, Command CSAV, from Authentium is set to auto update deffiles but I also receive instant notification via e-mail whenever new deffiles are posted, ( three or four times each day recently ). If I receive an e-mail notification I will always open my AV program to use the manual update even before auto update has kicked in. Sometimes manual update tells me that no new files are available, I put this down to DNS not yet updated and allow auto update to do its thing or try later. However over the past 2 days I have had several e-mail notifications but cannot update manually or automatically.
This morning as an experiment I disabled my Ntl BB and fired up my Zen dial up account and was instantly able to download deffiles that had been posted only a short time earlier.

[Matth]

The DNS should not be changing, though if it's the "slow DNS" problem, repeating the action after a few seconds, by which time the DNS has fetched the required record, should succeed - another alternative is to switch to an outside DNS, or for sites that rarely change address, stick the name/number in the hosts file.

http://www.analogx.com/contents/download/network/fc.htm
If nothing else in your system caches DNS (Windows does, but to a very limited degree), then this may help your performance. The first lookup will still be slow, but it'll slice some delay off so long as it remains in the cache.


The firewall issue is basically the problem that if a firewall does R-DNS every suspicious packet (and some DO), then it creates an additional (number of firewall users active) X (number of junk packets they get) load on the DNS server - if many firewalls are doing this, the load could considerably exceed the normal user load, since DNS is normally used only once at connection initiation, and even if no other cache is present, it should not be required again while browsing the same site - if you look at 100 forum posts, you will not be making 100 DNS requests.