The article covers

• VPN Gateway
• TCP/IP Gateway protocols
• Two major divisions in gateway protocols
• VPN Products

VPN Gateway

Gateway is a device (software/hardware) that converts one protocol to another. It is usually and enhancement to a router, firewall or security appliance. A network gateway converts packets from one network protocol to another. Gateway serves as an entry and exit point where some sort of processing is done on the information that passes through it. Many times it is also referred to as a router or layer 3 Switch. Gateway is also analogous to a voice-to-IP device that converts an analog voice stream, or a digitized version of the voice, into IP packets.

A network gateway is a system that joins two networks together. It can be implemented completely in software, completely in hardware, or as a combination of the two.

Gateways can operate at any level in a protocol (from application to low level signaling). Associated functionality is like firewalls are present in gateway software’s or hardware. There are many gateways and they are termed so because of the specific nature of the work and protocols they relate to.

• Cable/DSL gateway connects multiple computers to a single cable.DSL line for internet access. This includes a broadband router an Ethernet switch for attaching more computers.
• Signaling gateway is responsible for translating signaling messages between two media usually public switched telephone networks (PSTN) and Internet (IP). In modern VoIP it is usually a softswitch.
• Application gateway is also known as application proxy. It is an application program that runs on the firewall system between two networks.
• WAP gateway decodes and encodes requests and messages between a smart phone browser and the internet
• Circuit level gateway is a type of firewall.
• Media gateway is a device that converts multimedia input into data formats meant to be transmitted on a network

TCP/IP Gateway protocols

The core of the internet is made up of many autonomous systems. Each autonomous system is controlled by either a person or group or and organization. Each of these individual systems or groups uses a similar protocol like internet protocol for communication. Although inside a LAN other protocols may be used. The communication between these various individual systems may be internalized if it were a LAN or WAN and externalized if it were the internet. Thus the two major divisions in gateway protocols

• IGP- Interior gateway/routing protocols- RIP,OSPF, GGP, HELLO,IGRP,EIGRP
• EGP- Exterior gateway/routing protocols – EGP, BGP

IGP – Interior Gateway Protocol

This protocol is used to exchange routing information within and autonomous network like corporate LAN’s. These protocols are used to facilitate exchange of information between various gateways/routers.

• RIP-Routing Information Protocol is a distance vector protocol determining a route based on smallest hop count between source and destination
• OSPF- Open Shortest Path First protocol uses the Dijkstra’s algorithm to calculate the shortest path tree. A link state database is constructed and is identical to all routers. This determines the best path for routing traffic over a TCP/IP based network.
• GGP- Gateway to gateway protocol enables core-gateways to communicate with each other. This is used in VPN gateway to gateway connection.
• HELLO is a protocol that interior gateways use to communicate. It calculates the shortest path to other networks using delay time
• IGRP -Interior Gateway Routing Protocol is an enhancement over RIP
• EIGRP- Enhanced IGRP provides enhancements not there in IGRP like the ability to detect a loop in the network.

EGP-Exterior gateway protocols

It is a category of routing protocols used by autonomous systems to share routing information.
EGP- is a distance vector protocol that uses polling to retrieve information. This was developed in the early days of the internet and EGPv3 is used to interconnect autonomous systems.
BGP-Border gateway protocol replaces EPG protocol and is presently popular. It requires all manual configurations. Continue to: VPN Products for gateways