The DHCP option 114 which can be used to configure the URL of the provisioning server in Gigaset IP phones is <114> and implemented as following:

URL Option
This option is used to configure the provisioning server URL. URLs are specified in RFC 1738. 
The code for this option is 114, and its maximum length is 74 characters -->

  Code  Len    URL
  +------+---+----+----+----+---
   | 114 | n | c1 | c2 | c3 | ...
  +------+---+----+----+----+---

Communication flow

(Wireshark filter "bootp")

DHCP Discover ---->

DHCP Offer <----

DHCP Request ---->

DHCP ACK <----

Option: (114) URL

Length:

Value: