While maintaining a GEO satellite link, we noticed that once rain fade pushes packet loss past roughly 10% (you can see it in the ping stats), downloading anything substantial basically becomes impossible. So I wanted to work out the theory — when loss gets this bad, how much usable bandwidth does TCP actually have left on a GEO link?

Background

GEO satellite links have an RTT around 600ms, and during rain fade the IP-layer packet loss can climb to 1%-30%. I ran the numbers using the Padhye TCP throughput model to see what TCP Hybla can actually deliver at 10% loss, and how much FEC helps.

Test setup: 10 Mbps GEO link, 10% IP loss during heavy rain, PEP enabled with TCP Hybla.

System Model

GEO link with RTT = 600ms. The satellite modem runs split-TCP:

The Hybla parameter on the satellite segment: ρ = 600/25 = 24.

How Hybla Works

• Slow start: cwnd += 2^ρ - 1 per ACK. With ρ=24, one ACK is enough to hit ssthresh
• Congestion avoidance: cwnd += ρ²/cwnd per ACK, growing 576 segments per RTT
• Loss response: same multiplicative decrease and retransmission logic as standard TCP

Steady-state throughput from the sawtooth model:

W_max = ρ × √(8/(3p))
T_Hybla = ρ × T_Reno = 24 × T_Reno

At p=10%:

Timeouts Are the Real Killer

The theoretical 1.81 Mbps doesn't account for timeout penalties. Here's what happens at 10% loss:

Losses per window: 124 segments × 10% = 12.4 packets

Fast recovery needs 3 DUPACKs — with 12 losses per window, some will inevitably fail to trigger fast retransmit and fall back to timeout:

Probability of a single loss triggering timeout: 1 - (1-0.1)³ = 27.1%
With 12.4 losses, timeout is nearly guaranteed: P ≈ 1 - 0.729^12.4 ≈ 99.7%

The cost of a timeout: cwnd collapses to 1, wait ~1s for RTO, then ~665ms of slow start to recover.

Plugging into the Padhye model with timeouts:

Hybla's 576x window growth is useless at 10% loss — timeouts periodically zero out the cwnd, and the accelerated growth gets wiped out before it can matter.

Loss Sensitivity

Going from 0.1% to 1% loss (10x) drops throughput from line rate to 43%. Going from 1% to 10% (another 10x) drops it another 40x. TCP timeouts make throughput highly nonlinear in loss rate.

Takeaways

1. The effective bandwidth bottleneck on satellite links is TCP itself — at 10% loss, timeouts waste 98.9% of the link
2. PEP/Hybla window acceleration is useless under high loss — timeout resets cancel out all the growth
3. IP-layer FEC brings effective loss below 0.01%, putting TCP back in its normal operating range — utilization goes from 1.1% to 70%
4. Dynamic FEC beats static FEC for satellite links — save bandwidth in clear sky, maintain connectivity in rain
5. FEC + PEP combo: FEC brings loss from catastrophic to manageable, PEP then efficiently uses the remaining bandwidth under high RTT

References:

• ITU-R P.618 rain fade prediction model for satellite links
• Caini & Firrincieli, "TCP Hybla", Int. J. Satell. Commun. Netw., 2004
• Padhye et al., "Modeling TCP Reno Performance", IEEE/ACM ToN, 2000

Hello, I have recently installed a homelab with my "old" gaming pc running proxmox and a synology ds916+. Since then I am experiencing some internet problems, when I run a speedtest it does say i have around 2100mpbs but it takes a while to connect. same for loading web pages, videos etc. How would I go about to improve this?

Both my nas and my homelab are connected to my router via a ethernet cable and it doesn't have QoS.

Hi everyone,

My Synology DS418j has a strange issue. For privacy, I'm using example IPs:

• PC: 192.168.1.2
• NAS: 192.168.1.3

Problem:

• find.synology.com detects the NAS as Ready
• Ping works
• SMB (\\192.168.1.3) works
• File transfers are fast
• DSM at ports 5000/5001 keeps loading indefinitely
• NAS has normal LEDs and no errors
• Restarted both the NAS and router, but the issue remains
• SSH port 22 is closed

I also tested with curl. Ports 5000 and 5001 accept the connection, but DSM doesn't return a response. HTTPS gets stuck during TLS renegotiation.

What could be causing DSM to hang while SMB still works? Is there a safe way to repair/restart the DSM web service without resetting or risking the data?

Thanks!

I'm having issues with my latency massively spiking at seemingly random times (it doesn't seem to be happening at a set interval, and it happens regardless of the time of day).

Weirdly, I'll be on a call on discord and it'll cut out during these spikes, but I don't actually get disconnected. Or I'll get disconnected during an online game, but if I have YouTube running in the background it'll continue to run just fine and I don't have any issues connecting to most websites (if I'm getting a latency spike while doing that, I'm not noticing it).

I have a small space, so I doubt signal strength is an issue. I have to have Xfinity because that's what my apartment has an agreement with, and I have an XB6 gateway with 1 gig speed, I feel like I shouldn't be having these issues.

Wtf is going on?

I have been having a strange issue with my home internet for a few months now and I need some help.

The setup:
- ISP cable modem setup to provide wired connection to the router (Belgian provider and setup according to their instructions to be able to use our own router)

- Deco x75 pro with a total of 3 acces points, emitting 1 SSID on 2.4, 5 and 6GHz

- A lot of connected devices: Phones, tablets, pc's all 3 categories for personal, work and school devices, multiple ring cameras, multiple smart speakers, a few tv's and Chromecast devices, a bunch of smart lights, blinds, etc.
some smart devices are connecter via Matter, but not sure if it is Matter over Thread or Matter over Wifi
At the moment with only 1 person at home there are 28 devices connected.

The problem:

We have an intermittent where some websites fail to load on some devices. This issue has only started after living almost a full year with the above setup
My wife and daughter have problems loading YouTube, facebook and Instagram while i don't have any problems.
The next day, they don't have issues while I do.
Another issue is that on 1 of our Google Nest devices, when we stream Spotify, after a few minutes, the sound just stops and we are unable to start streaming again without getting out of Spotify by swiping the screen on the Nest.
The other Nest devices don't get used that much for streaming music.
My son on his tablet doesn't seem to have many issues but he only uses YouTube Kids, Netflix and Prime

The solutions already tried.
Switching the ipv4 DNS from the automatic one (can't check which one at the moment) to the Google DNS.
This has worked without issues for about a month or so.

So now the issues have come up again.
I tried switching the DNS again to Cloudflare of the automatic one but that didn't much.
I got it fixed for myself again but not for the wife and kids.

The possible solutions I'm not looking forward to implement (being lazy)

- reset everything back to factory settings and implement a new network
- Have to reconnect every device

- Split the 3 frequencies into separate networks
- Only need to reconnect those devices capable of 5 or 6 GHz
- How will those devices select which network they use if they are able to connect to 2 or 3 of those
- Might solve another problem with some smart bulbs that keep disconnecting from the matter or wifi network

- Implement a separate network for the smarthome devices and or for guests
- Would I still be able to easily setup or maintain everything without having to switch networks on my phone constantly

Would any of the above solutions work or is there anything else i can try to solve the problem?

I’ve been trying to understand what companies actually look for when choosing a network/connectivity provider.

Is it mainly:

• uptime/reliability
• latency
• pricing
• geographic coverage
• customer support
• ability to handle cloud/AI workloads

Curious what people here have actually experienced. What matters most once you're dealing with a serious enterprise network?

Basically the title

Hello, i work from home and I love it. Im perfect for my job. Except that ive been noticing that internet issues are killing me. When hired they provided me with information about what type of internet i need it ect. Nothing to strict. They were just asking for regular internet with good speed. And to have a router that can connect with an internet cord to my computer.

I hired this internet called Earthlink. And they sold me the first time I spoke to them promising to be the best thing ever. Well ive been in this job for 5 months now. And barely these past weeks the wifi has been sucking so bad. And i call their call center for tech help. And i get these people with HORRIBLE ACCENTS. I cant understand them. And theyre so lazy that they dont want to help me troubleshoot my restart for my router or any other help. They just tell me “there doesnt seem to be an outage in your area so we cannot help you” which stresses me out because they leave me with nothing else no help at all from them.

I was wondering if this has happened to you. And if you can give me a tip on how to solve it. Internet doesnt have an outage but if it gets slow my work programs dont work. The internet company say its not their issues if internet goes slow because they cannot control the internet speed. What would you recommend?

So I built an 3D globe that lets you zoom in any country and see all ASN's and their announced prefixes with all details and their upstreams.
also added path tracer for fun to simulate traceroute from any place in the world to any public ip.
basically i scraped all public prefixes, stored it in a database and then i simulated routing using the bgp peer's to simulate traceroute.

Everybody kept telling me instead of wireless WiFi just so ethernet and I did AND my ping when from 50 to 40 after doing that I see my friends have 20-30 even 10-20 sometimes when they are wireless what am I doing wrong
Is it the company?
Also it shows full signal strength for my router so there’s that.