I. Introduction  
II. History of the Network Update Problem from the Origins to SDN  
III. Taxonomy of Update Techniques  
IV. Update Techniques to Guarantee Connectivity Consistency  
V. Update Techniques to Guarantee Policy Consistency  
VI. Update Techniques to Guarantee Congestion-Aware Consistency  
VII. Further Considerations in Network Updates  
VIII. From Theory to Practice  
IX. Future Research Directions  
X. Conclusion  