Exhibit 99.4

Joinder Agreement

For

Phil Kaplan

The undersigned hereby agrees to be bound by the terms and conditions of the Employment Security Plan of Internap Network Services, Inc., dated as of November 14, 2007, as if he or she initially had executed such Plan as a party thereto, and, without by implication limiting the foregoing, agrees to each acknowledgment, covenant and other agreement contained therein.

Notwithstanding the provisions of the Employment Security Plan, (i) the Applicable Multiple for a Qualifying Termination During a Protection Period listed on Schedule B shall be two (2) and (ii) upon a Qualifying Termination other than during a Protection Period, the options held by Executive that were originally granted pre-merger on December 2, 2004 and December 16, 2005, shall become vested in their entirety.

         /s/ Phil Kaplan

         Employee

         November 14, 2007

         Date

Accepted:

INTERNAP NETWORK SERVICES, INC.

By:  /s/ Eric Suddith

Its:  Vice President, Human Resources

Date:  November 14, 2007