Le XS (devrait être SX pour Source eXchange... mauvaise traduc peut-être):
quand deux mules se rencontrent, elle se racontent des histoires de sources (=personnes qui ont le fichier que tu veux)... tu peux l'interdire à la tienne (parles pas aux étrangers, sale bête !), et, avec le menu, l'autoriser pour un fichier donné.(ndlr : ou pour tous les fichiers si tu coches ici l'option)
Les ânes (donkey) ne sachant pas dire autre chose que "HiHan", la mule est bôcoup plus efficace pour ça.
En gros, c'est à désactiver sur une petite connection (style 56k)

Max UDP par fichier : nombre maxi de connections UDP acceptées par fichier. Le paramètre "max conn" de l'onglet "connection" correspond au maxi de connections TCP (total, pas par fichier). A cause de l'échange de sources, des commentaires, des parties obtenues, des messages, etc, il peut y avoir beaucoup trop d'UDP pour un fichier donné, ce qui fait perdre l'UDP d'un autre fichier (et donc les sources par exemple...). Ils conseillent de mettre ce paramètre à 0,75 fois le "maxi connections de l'onglet connection", je mettais plutôt 0,5... Je sais pas si ça change grand chose, d'autre mods n'ont pas cette option et s'en sortent très bien... Peut-être pour des fichiers très répandus avec trop de sources...

Sources max par fichier (faibles) : un fois cette valeur atteinte, emule ne demande plus de sources au serveur. La valeur proposée par LSD est de 90% celle du nombre maxi de sources (on continue alors à en recevoir avec le XS)...

**LSD Tweaks**
LSD tweaks I:
-Disable AutoSort: disables AutoSort queue (saves CPU usage)
-Reconnect on lowID: eMule reconnects if user has a lowID.
-Increase release priority: Option to Increase Release Priority, pushing to 1st position queue (Very good for rare/small files)
-Use old priority system: old priority system uses different credit modifier then new eMule versions (from 0.27a and up = new priority system!), for more info about the credit modifiers see the eMule FAQ "rating&score" section.
-Disable/Enable [XS] Exchanged Sources Between Clients.

-Force Drop NNS (not needed source): drops from queue this source has he has no parts you need at the moment, note that this user may have them later on.
-Force Drop Full Queue (FULLQ): drops from queue this source as his upload queue reached its max and have no room for new user, this source may have room for you later.
-Force Drop Unknown: drops unknown sources (sources with status Unknown are dead/timed out sources or if you are banned and other unknown situations).
-Disable Re-Ask NNS: disables the re-asking of NNS in the set interval.
-Disable Re-Ask FULLQ: disables the re-asking of FULLQ in the set interval.
-Disable Re-Ask Server: disables the re-asking of server for new sources in the set interval.
-Frequency of Auto A4AF (af4f=ask for another file), time interval for A4AF may be altered here.

-Uploads Slots:
-Uploads Min: user defined minimum number of upload slots for better control of bandwidth distribution.
-Uploads Max: user defined maximum number of upload slots for better control of bandwidth distribution.
-Max New Connections in 5 sec’s: This is the number of new connection's eMule opens during 5 seconds. Default is 20.
-Max UDP Per File: When this limit is reached eMule stops asking servers for sources except the one it is connected to. Further sources are gathered via Client to Client Source Exchange and the local server.
This value depends on the Max Sources per File setting. 10-20% of Max Sources should be fine. As this limit greatly helps to reduce the load on servers it shouldn't be set any higher than 100.
-Max Sources Per File soft limit: On Soft Limit eMule stops searching for sources via Client to Client Source Exchange and on all servers. Only sources from which users are directly connected to for up- or downloading are added until Hard Limit is reached. Soft Limit cannot be changed as it is calculated from Hard Limit
-Hard Limit: Hard Limit is the maximum number of sources allowed for a file. If this limit is reached eMule stops accepting sources for this file.
-Max Connections: This is the maximum allowed number of TCP/IP and UDP connections. Connections are only opened if there is data transfer in progress, for search and queue requests or Client to Client Source Exchange.
Altering this value is normally not necessary, except on Windows 98/ME, then don't set this value any higher than 50.

-In LSD tweaks there are 2 buttons default/optimal, default gives standard settings, optimal is recommended but not good for all internet connections.

Basic recommended settings. (by drLSD):
max soft: 2000/3000
max hard 3000/4000
udp:100/200
max con 5: 60/100
Total con: 20000+

-Soft/hard if put higher can cause high-CPU usage or slow speed.
-It is not recommended downloading at the same time more than 3 files with 4000 sources.

LSD Tweaks II:
MSS (Max Segment Size): (SiRoB/mighty knife)
This setting can lower the IP overhead.
Don't confuse IP overhead with eMule overhead, the second one is shown by eMule if you activate "Show overhead bandwidth".
Actually, you will have less IP packets send for the same amount of data (less TCP-IP headers and more data). So, the transfers will be optimized.
To know what is the best MSS for you, go to the URLs shown in the "LSD tweaks II" links in preferences.

LSD mod **main features**
Source management: (dr-LSD)
Disable Source Exchanging between clients: You won't send and receive sources from other clients (keep this unchecked, except if you have a very small connection).
Disable NNS re-ask time: You won't re-ask files in NNS (Not Needed Source -> sources that don't have the chunks you need) status. If unchecked, you can set a time for re-ask.
Disable Full Queue re-ask time: You won't re-ask files in Full Queue status. If unchecked, you can set a time for re-ask.
Disable Server re-ask time: You won't re-ask the server for new sources. If unchecked, you can set a time for re-ask.

Upload Slot control: (dr-LSD)
Can adjust min slots to 1-16 and Max slots x-150
this feature gives the user control on how many upload slots will be open, so users can control how to distribute their bandwidth.

Release file control (dr-LSD)
Move "Release Files" to 1st queue position. (on/off)

Save/Load Sources 2 (enkeyDEV/kei-kun/Ottavio84)
Activate/deactivate it on the "Extended Settings".
This function save sources (10 by default) for the files that have less than a determined number of sources (300 by default).
If you restart eMule, these sources won't have to be searched again.

A4AF (Asking For Another File) control: (from enkeyDEV)
With eMule/eDonkey, you can't ask a client for 2 different files. The status of one of the file is set to A4AF.
Swap all A4AF to this file auto: If you ask for 2 files from the same client, this function automatically download from the file that has the box checked.
Swap all A4AF to this file now: Same as before, but not automatic.
Swap all A4AF to any other file now: You can guess.
The first number of the source's count is the number of files in A4AF status.

AntiCreditTheft: (from lovelace)
Detect if 2 people use the same userhash and remove the userhash thief (and their credit) from upload queue.

MSS (Max Segment Size): (SiRoB/mighty knife)
This setting can lower the IP overhead.
Don't confuse IP overhead with eMule overhead, the second one is shown by eMule if you activate "Show overhead bandwidth".
Actually, you will have less IP packets send for the same amount of data (less TCP-IP headers and more data). So, the transfers will be optimized.
To know what is the best MSS for you, go to the URLs shown in the "LSD tweaks II" links in preferences.