1. Introduction  
2. An Overview of TCP Working Mechanism  
3. TCP’s Challenges in CRNs  
4. The Existing Transport Protocols for CRNs  
4.1 Taxonomy of Available Proposals  
4.2 Transport Protocols for Single Hop Environments  
4.3 Transport Protocols for Multi-hop Environments  
5. Research Challenges and Open Issues  
6. Conclusion