Multiple SPs do not benefit from SSO

[MA Lanxin]

Dear all,

I encountered a problem when I deploy shibboleth. Could anybody help me?

I have one IDP(version 2.1) with UserPassword mothed against LDAP. 
I have several web contents that I want to protect in different hosts, 
and integrated SP 2.4.3 with Apache at each host. I have no DS currently. 

for example: 

https://sp1.ihep.ac.cn/secure
https://sp2.ihep.ac.cn/app


I passed the SSO authentication when I access 

https://sp1.ihep.ac.cn/secure  

I could get user's information(username,email,telephone,......) from  apache header. 
After this,I access another one at the same browser 

https://sp2.ihep.ac.cn/app

It redirected to the authentication page requesting to type username/password. 
It seems that it do not benefit from SSO when I access sp2. If I understood correctly, 
it should not re-authenticate. 

I do not configure "forceAuthn" on my SPs.   
Here is the configure in shibboleth2.xml on SP1 and SP2 

 <SSO entityID="https://idp.ihep.ac.cn/idp/shibboleth">
              SAML2 SAML1 
            </SSO>

Here is the configuration in apache on sp1 
<Location /secure>
  AuthType shibboleth 
  ShibRequestSetting requireSession 1 
  require valid-user 
</Location>


This is the configuration in apche on sp2 
<Location /app>
  AuthType shibboleth 
  ShibRequestSetting requireSession 1 
  require valid-user 
</Location>

DO I miss some configuration on IDP or SP?   

THank you very much!! 

REgards, 
Lanxin