1. © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 1 © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 1 © 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 © 2010 Cisco and/or its affiliates. All rights reserved. “Dr.” Mark Tunnel^Wtownsley, Cisco Fellow

2. © 2010 Cisco and/or its affiliates. All rights reserved. 2 When and where we think we need them for specific purposes

3. © 2010 Cisco and/or its affiliates. All rights reserved. 3 Tunnels act like the layer below that which they are carrying Often not perfectly, but “good enough” for a specific purpose IP tunnels act like Data Link Layers

4. © 2010 Cisco and/or its affiliates. All rights reserved. 4 All problems in computer science can be solved by another level of indirection… …except for the problem of too many levels of indirection - David Wheeler

5. They have a wide variety of uses…

6. © 2010 Cisco and/or its affiliates. All rights reserved. 6 While incompatible on the wire, IPv4 and IPv6 are both still “philosophically” IP

7. IPv4-Only Network IPv4-Only Network IPv4-Only Users NAT IPv6-Only Users CE Dual Stack Network Dual-Stack Users PE CE

8. IPv4-Only Network IPv4-Only Network IPv4-Only Users NAT IPv6-Only Dual Stack Network IPv6-Only Users CE 6↔4 Dual Stack Network I IPv6 Only Dual-Stack Users Dual-Stack Users IPv6 Only Dual Stack Network Dual Stack Network Dual-Stack Users PE CE