Spigot Fix (https://github.com/PaperSpigot/Paper-1.7/blob/master/CraftBukkit-Patches/0037-Lower-Chunk-Compression.patch)

patches/net/minecraft/network/play/server/S21PacketChunkData.java.patch

@@ -1,5 +1,14 @@
 --- ../src-base/minecraft/net/minecraft/network/play/server/S21PacketChunkData.java
 +++ ../src-work/minecraft/net/minecraft/network/play/server/S21PacketChunkData.java
+@@ -45,7 +45,7 @@
+ 
+     private void deflate()
+     {
+-        Deflater deflater = new Deflater(-1);
++        Deflater deflater = new Deflater(4); // Spigot -1 -> 4
+         try
+         {
+             deflater.setInput(this.field_149278_f, 0, this.field_149278_f.length);
 @@ -198,8 +198,10 @@
              if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
              {
@@ -52,3 +61,9 @@
                  }
              }
          }
+@@ -293,4 +301,4 @@
+             public int field_150281_c;
+             private static final String __OBFID = "CL_00001305";
+         }
+-}
++}

patches/net/minecraft/network/play/server/S26PacketMapChunkBulk.java.patch

@@ -16,7 +16,7 @@
 +        protected Deflater initialValue()
 +        {
 +            // Don't use higher compression level, slows things down too much
-+            return new Deflater(6);
++            return new Deflater(4); // Spigot 6 -> 4
 +        }
 +    };
 +    // CraftBukkit end
@@ -115,3 +115,9 @@
          p_148840_1_.writeShort(this.field_149266_a.length);
          p_148840_1_.writeInt(this.field_149261_g);
          p_148840_1_.writeBoolean(this.field_149267_h);
+@@ -241,4 +251,4 @@
+     {
+         this.processPacket((INetHandlerPlayClient)p_148833_1_);
+     }
+-}
++}