Tunneling Protocols
This section covers tunneling protocols that encapsulate network traffic to enable secure or specialized communication across untrusted or incompatible networks. These protocols are widely used in VPNs, broadband services, and network interoperability solutions.
Protocol / Tech |
Description |
Use Case |
|---|---|---|
L2TP (Layer 2 Tunneling Protocol) |
Tunneling protocol often combined with IPsec for encryption. Encapsulates PPP frames for VPNs. |
Secure remote VPN access. |
PPPoE (Point-to-Point Protocol over Ethernet) |
Encapsulates PPP frames within Ethernet frames, enabling ISPs to manage individual subscriber sessions over a shared Ethernet infrastructure. PPPoE supports authentication protocols (PAP, CHAP), IP address assignment, and session management. Widely used for broadband Internet access via DSL lines. |
DSL broadband subscriber management |
PPP (Point-to-Point Protocol) |
A data link protocol that encapsulates network layer packets for transmission over serial links. Supports authentication, compression, and encryption. Common for dial-up and VPN links. |
Dial-up and VPN connections |
IP-in-IP (IP Encapsulation within IP) |
Encapsulates one IP packet inside another IP packet. Used for simple IP tunneling across different network segments. |
Site-to-site tunneling, mobile IP, IPv6 transition mechanisms |
RFC: RFC 2661
Main Features:
Tunnels PPP frames across IP networks
No built-in encryption (typically paired with IPsec)
Often used in legacy VPN setups
Use Cases:
L2TP/IPsec VPN for remote users
Legacy Windows VPN infrastructure
Alternative Protocols:
PPTP (deprecated)
OpenVPN, WireGuard
Let us learn more about L2TP:
RFC: RFC 2516
Main Features:
Encapsulates PPP frames within Ethernet frames
Supports authentication protocols like PAP and CHAP
Enables per-user session identification and accounting
Operates on standard Ethernet (Layer 2)
Provides dynamic IP address assignment
Used by ISPs for subscriber session management
Use Cases:
DSL broadband subscriber authentication and management
Session-based IP address leasing by ISPs
Accounting and usage-based billing for residential internet
Point-to-point virtual connections over Ethernet infrastructure
Alternative Protocols:
IPoE (IP over Ethernet) – A simpler alternative without PPP overhead
L2TP – For tunneling PPP over IP networks in broadband aggregation
802.1X + RADIUS – Secure enterprise authentication at Layer 2
DHCP + VLANs – For IP provisioning with logical segmentation
Let us learn more about PPPoE:
RFC: RFC 1661
Main Features:
Encapsulates Layer 3 protocols over point-to-point links
Supports authentication (PAP, CHAP)
Includes error detection and framing
Optional compression and encryption
Multi-protocol support (e.g., IP, IPX, AppleTalk)
Link negotiation and teardown mechanisms
Use Cases:
Dial-up modem internet access
Point-to-point leased lines (ISDN, serial links)
Tunneling PPP over IP networks (e.g., PPP over L2TP)
Remote user VPN and secure access
Alternative Protocols:
HDLC – Simpler point-to-point encapsulation
SLIP – Outdated protocol replaced by PPP
L2TP – Encapsulates PPP for tunneling
Ethernet – For LAN and broadband access
RFC: RFC 2003
Main Features:
Encapsulates a complete IP packet within another IP packet
Outer IP header is used for routing over intermediary networks
Supports both IPv4-in-IPv4 and IPv6-in-IPv6 encapsulation
Minimal overhead and no encryption
Used as a basic tunneling mechanism in many systems
Use Cases:
Site-to-site tunneling across intermediate IP networks
Transport of private IP traffic over a public IP backbone
Supporting Mobile IP (mobile node to home agent)
IPv6 transition technologies (6in4, ISATAP)
Alternative Protocols:
GRE – More flexible tunneling with protocol field and checksum
L2TP – Tunneling of PPP across IP
IPsec – Adds encryption and authentication to tunneling
VXLAN – Overlay network tunneling for data centers
Let us learn more about IP-in-IP: