Horrible lag when playing Halo reach

Uhh cycling won't help if his PC is fine.

It's your cable if you're wired. Try a different one. If you're wireless, then something's messing with the signal. So, go wired or change the position of the console so it's not so close to walls/stuff that blocks other stuff/phones/anything wireless/microwaves
even though popcorn is nice. 155 ms is a lot. With that latency I don't think you'll be hosting any Reach lobbies any time soon :V

Have you considered powercycling your modem/router by unplugging for 10 seconds? That may help with the connection.

Hey man, I've been having the same exact problem. I play Halo: Reach and the past couple of days I've been lagging horribly. I never ever lag and it just recently started happening. I have no idea what's going on either.. I want answers!

This may help

Improve Xbox LIVE speed

Last Modified 02/06/2011

Are you experiencing any of the following Xbox LIVE problems?

Slow game play

Poor performance or "lag" between actions

Video streaming pauses

Frequent disconnections

Step through the solutions below to improve the performance of Xbox LIVE:

1: Restart your network hardware

If Xbox LIVE performance seems slow, try restarting your network hardware. Here’s how:

Turn off your Xbox 360 console and any network hardware (for example, your modem and router).

Wait 30 seconds.

Turn on your modem and wait one minute.

Turn on the next piece of hardware (for example, your router) and wait another minute.

Turn on your Xbox 360 console.

Sign in to Xbox LIVE and see if the performance is better.

If Xbox LIVE performance is still slow, try the next solution.

2: Improve your wireless signal (wireless only)

A weak wireless signal can cause poor Xbox LIVE performance. Check your wireless signal strength Here’s how:

Go to My Xbox, and then select System Settings.

Select Network Settings.

Select your wireless network name if you are prompted to do so.

Select Test Xbox LIVE Connection.

Do one of the following:

If your wireless signal strength is one or two bars, try improving your signal strength using the tips below.

If your wireless signal is three or four bars, try the next solution.

How to improve your wireless signal

Move your router or gateway off the floor and away from walls and metal objects (such as metal file cabinets).

Minimise obstructions along a straight-line path between your console and your wireless router or gateway.

Shorten the distance between your console and your wireless router or gateway. Ideally, your network hardware should be near the centre of your home.

Change the position of the aerial on your Xbox 360 Wireless Networking Adaptor (external adaptor only).

Turn off wireless devices. If your router uses the 2.4 GHz band, try turning off wireless devices, such as 2.4 GHz cordless telephones, Bluetooth devices and baby monitors. If you are using a wireless headset with a base station such as the Turtle Beach
wireless headset, try moving the transmitter away from your Xbox 360 console, or temporarily turn it off to see if your wireless network signal improves.

Try changing your wireless channel. Wireless routers and gateways can broadcast on different channels, and one channel might be clearer than another. See your hardware documentation for help with changing wireless channels.

Add a wireless repeater to extend your wireless network range. You can boost your signal strength by placing a wireless repeater halfway between your router or gateway and your console.

Add an Xbox 360 Wireless N Networking Adaptor. If your wireless router is not near the console, an Xbox 360 Wireless N Networking Adaptor might improve the signal strength. When you connect a wireless networking adaptor to an Xbox 360 S console, the console
will automatically use the wireless adaptor instead of the internal Wi-Fi. Learn how to connect a wireless adaptor.

Switch wireless signal bands. If you have a dual-band router and an external wireless adaptor, try switching the router to a wireless protocol that transmits on the 5 GHz band (wireless protocol A or N). See your hardware documentation for help with changing
the wireless protocol.

Do not use satellite, 3G or 4G phone type connections. These types of connections are not supported and you are likely to experience slow game performance or have problems downloading or streaming content. For the best Xbox LIVE experience, an Internet service
provider (ISP) with a high-speed cable or DSL connection is recommended.

If these tips did not improve your Xbox LIVE performance, try the next solution.

3: Maximise your bandwidth

When you play games or videos on Xbox LIVE, make sure that other computers in your home are not downloading or transferring files. When someone in your house browses the Internet, they use bandwidth that could be going to your Xbox 360 console.

Note Bandwidth is the amount of information transferred over your Internet connection. If your bandwidth is limited or fluctuates dramatically, it can affect the performance of Xbox LIVE.

If no one else is accessing the Internet and Xbox LIVE performance is still slow, try the next solution.

4: Reduce the number of players

Your Internet connection speed might not support a large number of players. Try reducing the number of players that can join your Xbox LIVE game. For example, reduce the number of players who can join your game from 16 to 8. If you notice an improvement,
contact your Internet service provider to see if you can upgrade your broadband connection speed.

Note Your connection upload speed determines how efficiently you can host games. The faster the upload speed, the more players you can host. There are several online connection tests that you can use to check your Internet connection speed.

If your Xbox LIVE performance is still slow, try the next solution.

5: Play at a different time of day

Xbox LIVE game performance can fluctuate with the speed of your Internet connection. Residential Internet networks are often busiest in the evenings when people are at home. You may get the best Internet connection speed during the day.

If your Xbox LIVE performance is still slow, try the next solution.

6: Try a wired connection (wireless only)

A wired connection is the fastest and most reliable connection type. If you're using a wireless connection, try switching to a wired connection to see if your Xbox LIVE performance improves. Here’s how:

Plug one end of a network cable into the back of your Xbox 360 console and the other end into a port on your router or gateway.

Test your Xbox LIVE Connection:

Go to My Xbox and then select System Settings.

Select Network Settings.

Select Wired Connection.

Select Test Xbox LIVE Connection.

Check your Xbox LIVE performance.

If your Xbox LIVE performance is still slow, try the next solution.

7: Contact your Internet service provider

Contact your Internet service provider (ISP) to see if there are performance problems in your area. Your ISP may have a service status webpage that you can visit.

If your Xbox LIVE performance is still slow, try the next solution.

8: Have a friend try these solutions

Found this in another post, here are my answers:

What Country/State/Province do you live in? Arkansas

Modem brand & model number: AT&T 3800-HGV-B

Router brand & model number: integrated into the modem

If Wireless, are you using a white or black external adapter, or an internal (Xbox 360S) adapter? n/a (wired)

Things you have tried:

Is UPnP Enabled? Yes/no/Unknown: modem doesn't support upnp (but no issues like this until the past week)

Do you have a NAT error? If so, what is your NAT? No. In Halo Reach NAT is listed as open, the other two as undetected (and have been that way since Reach was released)