RFC 2764 IP Based Virtual Private Networks February 2000 5.3.4 Intra-VPN Reachability Information ........................ 34 5.3.4.1 Directory Lookup ........................................ 34 5.3.4.2 Explicit Configuration .................................. 34 5.3.4.3 Local Intra-VPRN Routing Instantiations ................. 34 5.3.4.4 Link Reachability Protocol .............................. 35 5.3.4.5 Piggybacking in IP Backbone Routing Protocols ........... 36 5.3.5 Tunneling Mechanisms ...................................... 36 5.4 Multihomed Stub Routers ..................................... 37 5.5 Multicast Support ........................................... 38 5.5.1 Edge Replication .......................................... 38 5.5.2 Native Multicast Support .................................. 39 5.6 Recommendations ............................................. 40 6.0 VPN Types: Virtual Private Dial Networks ................... 41 6.1 L2TP protocol characteristics ............................... 41 6.1.1 Multiplexing .............................................. 41 6.1.2 Signalling ................................................ 42 6.1.3 Data Security ............................................. 42 6.1.4 Multiprotocol Transport ................................... 42 6.1.5 Sequencing ................................................ 42 6.1.6 Tunnel Maintenance ........................................ 43 6.1.7 Large MTUs ................................................ 43 6.1.8 Tunnel Overhead ........................................... 43 6.1.9 Flow and Congestion Control ............................... 43 6.1.10 QoS / Traffic Management ................................. 43 6.1.11 Miscellaneous ............................................ 44 6.2 Compulsory Tunneling ........................................ 44 6.3 Voluntary Tunnels ........................................... 46 6.3.1 Issues with Use of L2TP for Voluntary Tunnels ............. 46 6.3.2 Issues with Use of IPSec for Voluntary Tunnels ............ 48 6.4 Networked Host Support ...................................... 49 6.4.1 Extension of PPP to Hosts Through L2TP .................... 49 6.4.2 Extension of PPP Directly to Hosts: ...................... 49 6.4.3 Use of IPSec .............................................. 50 6.5 Recommendations ............................................. 50 7.0 VPN Types: Virtual Private LAN Segment ..................... 50 7.1 VPLS Requirements ........................................... 51 7.1.1 Tunneling Protocols ....................................... 51 7.1.2 Multicast and Broadcast Support ........................... 52 7.1.3 VPLS Membership Configuration and Topology ................ 52 7.1.4 CPE Stub Node Types ....................................... 52 7.1.5 Stub Link Packet Encapsulation ............................ 53 7.1.5.1 Bridge CPE .............................................. 53 7.1.5.2 Router CPE .............................................. 53 7.1.6 CPE Addressing and Address Resolution ..................... 53 7.1.6.1 Bridge CPE .............................................. 53 7.1.6.2 Router CPE .............................................. 54 7.1.7 VPLS Edge Node Forwarding and Reachability Mechanisms ..... 54 7.1.7.1 Bridge CPE .............................................. 54 Gleeson, et al. Informational