1. Jonathan Brewer Technical Director Araneo Wireless Solutions www.araneo.net.nz 23-03-2006 Layer 3 Tunnels for Broadband Delivery

2. 2 Layer 3 Tunnels for Broadband Delivery – Outline What's the Point? Open-Access Networks Why Segregate Traffic? Sub-Layer 3 Traffic Segregation (VLAN & MPLS) Point-to-Point Protocol (PPP) Generic Routing Encapsulation (GRE) Point-to-Point Tunneling Protocol (PPTP) Point-to-Point Protocol over Ethernet (PPPoE) IP in IP Tunneling (IPIP) Layer 2 Tunneling Protocol (L2TP) Next Steps – L2TPv3 References

3. 3 What's the Point of this Talk? Layer 3 Tunnels are useful for delivery of broadband Private Layer 2 services are expensive IP Services are cheap and reliable enough They're not without their quirks and issues I'll show how we use these services day to day

4. 4 Open-Access Networks A physical access network shared by multiple operators Any user can select any service provider Any service provider can deliver services

5. 5 Homogeneous Open-Access Network Ethernet Based Metropolitan Area Network

6. 6 Heterogeneous Open-Access Network Multi-Modal Wide Area Network

7. 7 Why Segregate Traffic? Gain Simple Traffic Engineering P-P circuits are easy to rate-limit Reduce Network Complexity Avoid using an IGP Avoid ugly source routing Add Security to End Users No proxy-arp related outages :-) Increase Safety to Network / Network Operator Hide internal router addresses Provide a seamless end-user experience End user doesn't see what goes on behind the curtain

8. 8 Sub-Layer 3 Traffic Segregation VLAN – 802.1Q Bridged Ethernet Segments Frames with a VLAN id for traffic segregation Inexpensive and standards based Difficult over Heterogeneous Networks MPLS – Multi-Protocol Label Switching Any protocol (though in practice mostly IP) Designed for creating virtual circuits over packet nets Expensive to buy, implement, maintain Different implementations from each vendor

9. 9 Point-to-Point Protocol (PPP) (RFC 1661) Can encapsulate many layer 3 protocols Link Control Protocol manages up/down/maintain Authentication can happen before network brought up PAP, CHAP, MSCHAPv1, MSCHAPv2 Used for virtually all dial-up Internet connections Used over L3 in some tunnel technologies

10. 10 Generic Routing Encapsulation (GRE) (RFC 1701/2) Put any Layer 3 packet inside another Layer 3 packet Packets are IP Protocol 47 Completely Stateless Reduces packet size in most cases (24 byte overhead)

11. 11 Point-to-Point Tunneling Protocol (PPTP) (RFC 2637) GRE + PPP = PPTP GRE Session managed on TCP port 1723 Cisco-developed protocol licensed to Microsoft Popular because included in MS Windows Uses established PPP authentication infrastructure MPPE Encryption Optional (Typical)

12. 12 PPTP Example – CafeNET VPN Access CafeNET = CityLink owned WiFi access network Typical user experience is a captive portal + pay per mb ISPs can have tunnels allowed to particular addresses User first receives a CafeNET IP address via DHCP On PPTP establishment, user receives an ISP address VPN can then be used to deliver ISP service End user is routed a /32 on the ISP network

13. 13 PPP over Ethernet (PPPoE) (RFC 2516) Not a Layer 3 tunnel, but worth mentioning Encapsulation of PPP inside of Ethernet Allows PPP to run directly over Ethernet links Requires a bridged Ethernet topology Not going to do this on top of cheap IP services Popular with DSL and Wireless broadband services

14. 14 IP in IP Tunneling Encapsulates an IP packet inside of another IP packet Used to simplify complex routing problems Easy way of creating a non-secure VPN Overhead of 20 bytes (did you know Halliburton has their own /8?)

15. 15 Layer 2 Tunneling Protocol (L2TP) (RFC 2661) PPP over UDP/IP (Port 1701) PPP can carry any protocol L2TP frequently carries IP traffic over IP networks When run over IP, can be encrypted via IPSEC Used extensively in New Zealand (UBS)

16. 16 L2TP & IPIP Example – Araneo Access Network Ten ISPs offering broadband services Eight Commodity IP network connections

17. 17 Next Steps for Tunneling – L2TPv3 Standardized Frame Relay, ATM, Ethernet over IP Even 802.1Q VLANs can be encapsulated with L2TPv3 Seen as robust and a pragmatic challenger to MPLS How about Frame over 802.11?

18. 18 References PPP http://www.ietf.org/rfc/rfc1661.txt GRE http://www.ietf.org/rfc/rfc1701.txt IPIP http://www.ietf.org/rfc/rfc2003.txt PPPoE http://www.ietf.org/rfc/rfc2516.txt PPTP http://www.ietf.org/rfc/rfc2637.txt L2TP http://www.ietf.org/rfc/rfc2661.txt MPLS http://www.ietf.org/rfc/rfc3031.txt L2TPv3 http://www.ietf.org/rfc/rfc3931.txt