For Networking in the ISP space, for me the most helpful have been:
- Interdomain Multicast Routing: Practical Juniper Networks and Cisco Systems Solutions
- Inside Cisco IOS Software Architecture
- MPLS-Enabled Applications: Emerging Developments and New Technologies
This one's not a textbook but proved invaluable to me in learning optical networking:
- New and Updated - Everything You Always Wanted to Know About Optical Networking - https://www.youtube.com/watch?v=__wn9zXFiy8
- Interdomain Multicast Routing: Practical Juniper Networks and Cisco Systems Solutions
- Inside Cisco IOS Software Architecture
- MPLS-Enabled Applications: Emerging Developments and New Technologies
This one's not a textbook but proved invaluable to me in learning optical networking: - New and Updated - Everything You Always Wanted to Know About Optical Networking - https://www.youtube.com/watch?v=__wn9zXFiy8