Subject: Re: [EToSat] [External] - Re: TCP over satellite links

From: Nicolas Kuhn <[email-masked]>
Date: Mon, 30 Aug 2021 14:32:32 +0200

Dear Gabe,

Even if the PEPsal implementation is old, it exploits the kernel on which
it is installed - which makes it relevant for evaluations.We regularly use
it for assessing the performance of a split-TCP connection. While it may
not compete with industrial proxies, it can reach fair performance.

There are many parameters that can help TCP reach good performance.
Here is an example list :
https://wiki.net4sat.org/doku.php?id=openbach:exploitation:jobs:tcpconflinux_2.2
You may want to try them out depending on your use-case.

FYI, we proposed in [
https://www.ietf.org/archive/id/draft-jones-tsvwg-transport-for-satellite-00.txt
] a list of challenges that a congestion control faces in GEO systems:
- Getting up to Speed
- Sizing of Maximum Congestion Window
- Reliability (Loss Recovery/Repair)
- Flow Control
- ACK Traffic Reduction

Some pointers for performance improvements :
- Hystart : we have encountered some performance issues with Hystart - you
may be interested in Hystart ++ [
https://tools.ietf.org/id/draft-ietf-tcpm-hystartplusplus-00.html ]
- Buffer sizes : depending on the targeted BDP, increasing the buffer sizes
may be relevant [ slide 7 of
https://datatracker.ietf.org/meeting/interim-2020-panrg-01/materials/slides-interim-2020-panrg-01-sessa-updates-on-quic-over-in-sequence-paths-with-different-characteristics-00.pdf
]
- Adequate CC : CUBIC still reaches fair performance over satellite links

I hope this helps,
Kind regards,

Nico

-------

Gabriel Black <[email-masked]> Mon, 16 August 2021 17:06
UTCShow header

Thank you for the reply.

I think for now, the characteristics we are targeting is satcom (e.g.,
 ~500+ ms latency (GEO) and static ground station -- less of the
variability you’d find in LEOs). I’ve come across pepsal for a reference
implementation, but it seems very old and I question its performance. I was
wondering if since that time there were perhaps standard extensions/options
to TCP that could now be used instead that would perform well in GEOs or if
there were new implementations of a PEP that would perform well. For now,
I’m not worrying about header encryption (e.g., ipsec) – just want to
accelerate tcp connections. If any know of any reference implementations or
of extensions/tcp options that would give me the best bang for the buck,
I’d very much appreciate it.

Thanks again.

Gabe

From: Aaron Falk <[email-masked]>
Sent: Monday, August 16, 2021 10:25 AM
To: Gabriel Black <[email-masked]>
Cc: [email-masked]; [email-masked]
Subject: [External] - Re: TCP over satellite links

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cc: etosat

Hi Gabe-

You’ll find a bunch of information in the RFCs published by the  <
https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_wg_tcpsat_documents_&d=DwMFaQ&c=zeCCs5WLaN-HWPHrpXwbFoOqeS0G3NH2_2IQ_bzV13g&r=YnQ9DMJpb9J9GXU9h7_df_bzYNqCkodpRCL5l24fu74&m=zpJsKH-twIdq68wcDkXBkRPT-v9F-5pZOtaOg7HGYd8&s=T9SgSdod0Hg-FPqr8U1NdupW2K2L0f4JmO-kSZ0NJfQ&e=>
TCPSAT and  <
https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_wg_pilc_documents_&d=DwMFaQ&c=zeCCs5WLaN-HWPHrpXwbFoOqeS0G3NH2_2IQ_bzV13g&r=YnQ9DMJpb9J9GXU9h7_df_bzYNqCkodpRCL5l24fu74&m=zpJsKH-twIdq68wcDkXBkRPT-v9F-5pZOtaOg7HGYd8&s=ovwcfmh-m6OIhDtPGQq6oGcjpLjFV1STv__U7d7hfng&e=>
PILC working groups. I’ve cc’ed this response to a new mailing list
discussing satellite performance issues ( <
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ietf.org_mailman_listinfo_Etosat&d=DwMFaQ&c=zeCCs5WLaN-HWPHrpXwbFoOqeS0G3NH2_2IQ_bzV13g&r=YnQ9DMJpb9J9GXU9h7_df_bzYNqCkodpRCL5l24fu74&m=zpJsKH-twIdq68wcDkXBkRPT-v9F-5pZOtaOg7HGYd8&s=RaPojR1iX1qLXBKs5ZtZTt-VDV9PQVLf9Nx1yfxOTDg&e=>
etosat) and if you still have questions (eg, if you are looking at
performance issues around LEO constellations, you might find help there.
Regarding reference implementations, I think it will depend on which
performance optimizations you are interested in and that, in turn, will
depend on the characteristics of your satellite network.

Best,

--aaron

On 16 Aug 2021, at 12:12, Gabriel Black wrote:

Hello,

I am trying to accelerate TCP over satellite links and have found
documentation about SCPS-TP and other aspects of the TCP protocol that can
be modified to improve the performance over satellite links. However, I’m
finding it extremely difficult to find any sort of reference
implementations of the protocol or any extensions to accomplish that.

I was wondering if you might be aware of any reference implementations or
any extensions to tcp (if they have already been implemented), that would
be best suited to accelerating TCP through satellite links.

Thank you for your time.

Very respectfully,

Gabe Black