Generic Routing Encapsulation

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Generic Routing Encapsulation

(networking, protocol)
(GRE) A protocol which allows an arbitrary network protocol A to be transmitted over any other arbitrary network protocol B, by encapsulating the packets of A within GRE packets, which in turn are contained within packets of B.

Defined in RFC 1701 and RFC 1702 (GRE over IP).
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

GRE

(Generic Routing Encapsulation) A tunneling protocol developed by Cisco that allows network layer packets to contain packets from a different protocol. It is widely used to tunnel protocols inside IP packets for virtual private networks (VPNs). For example, the point-to-point tunneling protocol (PPTP) is based on GRE, and GRE is used with IPsec to transmit routing protocol data from one router to another, which IPsec does not natively support. See tunneling protocol, PPTP and IPsec.
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References in periodicals archive ?
- For network protection from cyber security threats, WR224 features Firewall, OpenVPN, GRE tunnel, HTTPs/SSH secure login, TACACS+ multi-user authentication for privileged user management.
These two messages are exchanged over a GRE tunnel, and after this exchange the SGW and the PGW set up an additional bidirectional GRE tunnel for forwarding of UE's data flows.
The GRE tunnel is pointed to routers at the command posts to connect the unit's EPLRS backbone to the MCSC and allow the shared PLI feed of the combined database to publish down into the unit network.
Advantage of GRE tunnels is that the traffic other than Internet Protocol (IP) would also be routed through it and by using Internet Protocol Security (IPsec) in conjunction with GRE tunnel it is possible to secure the data travelling through it.
In general with conventional GRE tunneling, the inner IPv4 addresses are not routable over the network which the GRE tunnel forms.
* IPv6 using tunnels between CE-to-CE routers, including Manual Tunnel, GRE Tunnel, Automatic IPv4-Compatible Tunnel, and 6to4 Tunnel
* IPv6 using tunnels between PE-to-PE routers, including Manual Tunnel, GRE Tunnel, Automatic IPv4-Compatible Tunnel, and 6to4 Tunnel
Generate data and perform statistical analysis to determine if there is a statistically-significant difference among the performance metrics (delay, jitter, throughput) of IPv6 CE-to-CE tunneling mechanisms, specifically Manual Tunnel, GRE Tunnel, Automatic IPv4-Compatible Tunnel, and 6to4 Tunnel.
Generate data and perform statistical analysis to determine if there is a statistically-significant difference among the performance metrics (delay, jitter, throughput) of IPv6 PE-to-PE tunneling mechanisms, specifically Manual Tunnel, GRE Tunnel, Automatic IPv4-Compatible Tunnel and 6to4 Tunnel.
In a GRE tunnel environment, the PoP routers are only one hop away from each other regardless of how many hops the transport network is taking, which greatly simplifies troubleshooting.
"The only way to do that is establish a tunnel from one end to the other, and GRE tunnels solve this problem."
"Because the new design required that packets be sent through the GRE tunnels, we were losing visibility of the diffserv code-point flag on the packet, which tells the MPLS (multiprotocol label switching) network what priority the packet has," explains White.