The Dreaded Lag Monster

Lag is a term Second Life users have become all for familiar with.

It is a common occurrence to see comments about being bitten by the lag monster but lag comes in many shapes and sizes, shapes and levels of announce. Here are a few examples:

“My avatar takes forever to start walking and will keep walking after I try to stop”; chat does not appear for a long time; does not appear in the order sent; or does not appear at all. Lag can cause a long list of rez issues and of course our all-time favorite is getting kicked off without warning. These problems are just symptoms with a variety of causes. Let’s discusses the sources of lag and what you can do about it.

The first thing to learn is that no matter with whom you talk, you will not find anyone who will admit to being part of the problem. Lag is the hot potato of the SL.

When you are logged in, there are several things that have to work smoothly together to minimize lag. These are your computer, the Internet connection, and the Linden Lab servers and internal network and databases. There is plenty of blame to spread around so let’s start with your screen and working outward.

Your Computer:

Second Life is both graphics-intensive, and requires a lot of bandwidth to communicate with the Linden Lab servers. Therefore your computer must be capable enough to run the Viewer program with minimal problems.

Graphics Hardware: Your monitor and graphics card are what together produce the images you see on the screen. Graphics chips vary a great deal in speed.

CPU and Memory: The Second Life Viewer program tends to use a lot of your computer resources. On a windows system, typing Ctrl-Alt-Del will open the "Windows Task Manager", whose performance tab can show you the current percentage utilization of your CPU. If you find out it is stuck at 100%, you can shut down any other programs you have running, reduce the settings within the Viewer, or try a different viewer with lower requirements.

The program also uses several hundred MB of main memory. Once the real physical memory has been used up, most computers will swap data out to the hard drive temporarily. This is a slow process. If you see the "Commit Charge" (actual memory used) is more than the amount of physical RAM installed in your computer, you have two options: shut down other programs and reduce settings in the SL Viewer, or add more memory to your computer.

Rule of thumb
As a guide, 512MB would be barely usable, 768MB is usable on the lowest settings, 1 GB is adequate, and more than that is good, especially if you want to run other programs at the same time

Another interesting thing I have noticed is that no matter what configuration your computer has it will not match the specs listed under Linden Lab requirements. I harbor my own suspicions that a computer that matches those specs can even exist.

If you wish to compare your hardware and software the Linden Lag requirements you can check out their site http://secondlife.com/support/system-requirements/

Internet Connection

Second Life requires constant communication with the Linden Lab servers. Data speed is highest when you first arrive at a new location, are moving around quickly, or in an area where lots of people are coming and going. All of these require sending you new data so you can see it all.

If you are on a wireless router, or entirely wireless connection, you may not be getting these speeds. Dial-up is definitely too slow for Second Life. Once your surroundings have downloaded, your bandwidth will stabilize at anywhere from 4 to 50 kilobits per second. Paradoxically, a connection speed that is too high can cause problems. Your computer has to do something with the new data as it comes in. If it is too busy, it can miss data packets, which then get re-sent. This makes the problem worse.

In addition the routers do get outmoded. Just because it is still working does not mean it is working well. If your router is not at least N 300 it is not keeping up high connect speeds needed to run SL. A look at the bottom of your router will tell you the rating.

On the Server side:

The Linden Lab servers have to keep track of everything happening in a map region, and send that information to all the users who can see the region. If they have too much to do, they will slow down the simulator frame rate so as to not lose data. If too much communication is required to fetch data about objects and send them to all the users, they can become backlogged. That is what is happening when chat is messed up.

There is a Lag Meter to break down Client, Network, and Server lag, with corresponding lights show lag for each. A few things to look at on the "Statistics Bar" is percentage of packet loss. If packet loss shows as 0% that means you have a fast connection and you can experiment with increasing bandwidth for faster downloading. Another thing to watch is frame rate.

The "Statistics Bar" shows packet loss as a percentage. If it anything above 0% on a steady basis, go to top menu Edit > Preferences > Network > Maximum Bandwidth and try lowering the value to reduce packet loss. On the other hand, if you have a fast connection and can handle it, you can increase the bandwidth to download data faster.

On the same tab, Disk Cache Size: controls how much data sent from the servers is saved on your hard drive. This includes textures, animations, inventory list, sound clips, and other items. A higher setting will keep from having to repeat downloading items again when you see them.

Streaming audio and video media, and voice chat all require increased bandwidth. Look at the top menu bar and use Edit > Preferences > Audio & Video > Streaming Preference gives you choices about features you want and those you can turn off. . Voice chat also uses an accessory program from Vivox to run, and turning it off will also lower CPU use.

The Graphics Card Chart (http://wiki.secondlife.com/wiki/Typical_Frame_Rate_Performance_by_Graphics_Card/GPU) gives a relative range of performance for Second Life, though your frame rate will vary depending on settings and where you are in the 3D world. A more up to date relative ranking of cards can be found at Tom's Hardware Guide (http://www.tomshardware.com/reviews/best-graphics-card,2387-7.html). The lowest few groups on that list will not be able to run Second Life adequately. See the System Requirements page for basic information.

The Second Life world is both large and "live" (constantly changing). So some very fast algorithms (ie BSP trees and pre-compiled maps) used in other 3D games can't be used here. Instead the data to create the view has to be downloaded and then transformed into the 3D view in real time. This means you will get a lower Frames-Per-Second (FPS) rate than you will get with most other games.

To see what you are getting for frame rates, open the Statistics floating window using (CTRL - Shift - 1) or the top menu View > Statistics Bar item.

If you already know you have a lower performance video card, there are settings that will increase speed at the expense of quality. If you are getting good frame rates, you can set some of these higher:

Run Second Life in a window - Uncheck and select a lower resolution

Draw Distance - The single most important control that affects lag is how far from you world details become visible. When this distance doubles, the amount of data that must be downloaded and displayed goes up 4-8 times. So lowering this slider can make a big difference.

Shaders, Reflection Detail, Avatar Rendering: - All these checkboxes should be UNchecked.

Lighting Detail, Terrain Detail: - Set to Sun and Moon only, and Low, respectively.

Max Particle Count: - to 256

Mesh Detail: sliders all the way to the left

Filtering: - Leave unchecked

Antialiasing: - Disabled

Texture Memory (MB): - Normally set to same as your graphics card memory size

As you have probably guessed by now, a SL performance is a complicated series of interacting systems that make it nearly impossible to narrow the blame down to just one thing.

On the up side, symptoms can sometimes help to pin-point areas to check.

"I can't walk (I can only rotate in place)", "my avatar keeps moving several minutes after I try to stop", and "the mini-map turns red (or objects and the terrain disappear)".

• All of these are signs that you are (at least partially) disconnected from Second Life. While you're logged into Second Life, you're connecting to several different parts of the Second Life servers (for the region you're in, your inventory, your cash balance, etc.) It's possible to get disconnected from some parts of Second Life and not others, resulting in your avatar getting stuck. When this happens, you need to close and restart Second Life to get reconnected.  If this happens consistently after a certain period of time (like a few minutes), it's likely there's other software on your computer (firewall or internet security software) that's disconnecting Second Life.
• 
  
  
• If you're using wireless, you may want to try a wired connection.
• 
  
  
• If this happens when someone else at your location tries to log onto Second Life, you might need to tweak your network a little to let multiple computers use Second Life.
• 
  
  
• Finally, the region you're in may be busy or overloaded. Try to see if going somewhere else reduces the problem.
• 
  
  

This barely scratches the surface of the issues that feed the Lag Monster but it is a start.

Here are other places to check for answers.

* Graphics Cards - Information on selecting a card (http://wiki.secondlife.com/wiki/Graphics_Cards)

* How to identify your graphics card (http://wiki.secondlife.com/wiki/How_to_identify_your_graphics_card)

* Updating drivers - Having the latest drivers can improve performance a bit  (http://wiki.secondlife.com/wiki/Updating_drivers)

* SL's Knowledge Base (http://wiki.secondlife.com/wiki/How_do_I_check_for_packet_loss_%28network_lag%29%3F