Dahdi Installation Failure

I have downloaded dahdi-linux-complete-current.tar.gz from the download.digium.com and followed its instructions for installation.

[server] tar -zxvf dahdi-linux-complete-current.tar.gz
[server] cd dahdi-linux-complete-2.2.1+2.2.1
[server] make

Below is the output I receive from that command
make -C linux all
make[1]: Entering directory /root/dahdi-linux-complete-2.2.1+2.2.1/linux' make -C drivers/dahdi/firmware firmware-loaders make[2]: Entering directory/root/dahdi-linux-complete-2.2.1+2.2.1/linux/drivers/dahdi/firmware’
Attempting to download dahdi-fwload-vpmadt032-1.20.0.tar.gz
–2010-03-24 15:27:31-- downloads.digium.com/pub/telepho … 0.0.tar.gz
Resolving downloads.digium.com…
Connecting to downloads.digium.com||:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: 146556 (143K) [application/x-gzip]
Saving to: `dahdi-fwload-vpmadt032-1.20.0.tar.gz’

100%[======================================>] 146,556 196K/s in 0.7s

2010-03-24 15:27:32 (196 KB/s) - `dahdi-fwload-vpmadt032-1.20.0.tar.gz’ saved [146556/146556]

make[2]: Leaving directory /root/dahdi-linux-complete-2.2.1+2.2.1/linux/drivers/dahdi/firmware' You do not appear to have the sources for the 2.6.18-164.el5PAE kernel installed . make[1]: *** [modules] Error 1 make[1]: Leaving directory/root/dahdi-linux-complete-2.2.1+2.2.1/linux’
make: *** [all] Error 2

I get the same error when running the command [server] make install
The error message is clear, where can I get the sources required?

Run this command : yum install kernel-devel