[c-nsp] Cisco 2811 performance issue - dual(new) isp

Vinny Abello vinny at abellohome.net
Mon Dec 19 17:21:42 EST 2011

Hash: SHA1


I don't believe Verizon FiOS uses compression. Neither would the Windows machine plugged directly into the hand off, so it would not compress or decompress data in communicating with Verizon's hardware. Compression of an entire link is CPU intensive and doesn't scale well, especially at higher speeds. I think it would be much much easier for Verizon to provide more bandwidth than to provide more hardware with faster CPU's to aggregate all the customers. Compression can take place between web servers and web browsers, but that has nothing to do with the ISP's speed.

The Verizon speed optimizer turns on TCP 1323 extensions, adjusts the TCP receive window and adjusts the MTU to 1492. None of these things involve compression. Most of them involve enabling settings in the operating system (which should be on by default in newer versions of Windows) to take advantage of the size of the pipe. They are also transparent to routers in the middle (except the MTU) including the 2811. I think the optimizer is mostly for older versions of Windows. I'm suspecting you are seeing slow throughput on your *nix box because it may not have 1323 extensions enabled to support window scaling and selective acknowledgements... or perhaps you just have a simple duplex mismatch somewhere. It's very difficult to scale the bandwidth without these things especially when latency is introduced. You might want to look into seeing if a sysctl or similar knob can turn them on and try again. All the recent *nix OS's I have seem to have this enabled already by default.

The last thing I heard about ISP's and compression was from years ago using that Propel software which was for dial-up and slower broadband connections. The compression was lossy though and would decrease the quality of most images. If I remember correctly, there are speed tests out there that will run with highly compressible vs uncompressible data for contrast just to verify. I'm sure there could be some oddball compression things being done out there by some ISPs, but Verizon FiOS isn't one of them based on all the information I've come across over the years since I've followed their roll out.

On the topic of the 2811, what features are enabled? This can have a huge impact on throughput. With just straight IP routing and firewall features enabled, I used to get 40 to 50Mbps out of an 1841 without any problems. This was of course maximizing the MTU size to achieve this. IPS features usually drag the speed down quite a bit as do a lot of types of protocol inspection. It's all about PPS rather than Mbps. The closer to the MTU the packet size is, the higher throughput you'll achieve. 5000 pps @64 bytes vs 5000 pps @1500 bytes is pretty much the same to the router for just packet forwarding, but the difference is 320Kbps vs 7.5Mbps when it comes to throughput.

- -Vinny

On 12/19/2011 1:21 PM, harbor235 wrote:
> The provider is using compression to get you the 50/5 number. The 2811
> represents the true bandwidth allocation.
> Did they ask you to go to a provider site to optimize your laptop?
> Verizon did that to me, they told me I have 25 symteric although
> I only get 8 symetric when I use my *NIX box to validate.
> Mike
> On Mon, Dec 19, 2011 at 1:06 PM, Adam Atkinson <ghira at mistral.co.uk> wrote:
>> I saw a 2811 flattened recently by MTU / MSS issues, so
>> would be curious to see "show ip traffic"
>> ______________________________**_________________
>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>> https://puck.nether.net/**mailman/listinfo/cisco-nsp<https://puck.nether.net/mailman/listinfo/cisco-nsp>
>> archive at http://puck.nether.net/**pipermail/cisco-nsp/<http://puck.nether.net/pipermail/cisco-nsp/>
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/

Version: GnuPG v2.0.17 (MingW32)


More information about the cisco-nsp mailing list