Intro

Welcome to Adventures in Security. In this lesson, we explore various ways data is sent across both private and public wide area networks. Some of this technology, such as frame relay, is getting harder to find in actual implementation, but you still need to understand it for the exam and for dealing with organizations that still might use it. The script for this video, downloadable from above, is formatted as an easy-to-use study guide.

Considerations

Although this information might seem less exciting than other technology topics, you need to understand their advantages and disadvantages and how they relate to cost, security protocols supported, fault tolerance, resistance to failure, and access to equipment. Before looking at transmission media, we need to understand three approaches to user or device communication over that media.

TELNET

The first is telnet. Telnet, developed in 1969, is a way to access and manage remote devices using a command line. It is an acronym for telecommunications and networks, and it's best known for its use on UNIX platforms. Using a protocol specified in RFC 854, telnet represents a terminal-like interface to the user. This is an easy-to-use utility, but it is not secure. Telnet does not support encryption or reasonable authentication techniques, making any attempts at authentication susceptible to interception, and leaving the transfer of information open to theft. This utility has fallen from use and is not installed by default on commonly used operating systems.

SSH

SSH, or secure shell, was developed in 1995 as a secure replacement for telnet. Like telnet, it enables terminal interface access to remote devices under management. Unlike telnet, SSH provides encryption for both secure authentication and data transfer, using layered protocols that help protect confidentiality and integrity connected devices communicate by a secure tunnel, through which pass multiple logical communication channels. SSH, largely within popular implementations like PuTTY and OpenSSH is commonly used today.

SOCKS

Entities use the SOCKS, sockets secure protocol for secure access to devices, by passing through a proxy. The current version, SOCKS5, enables authentication and the use of other protocols, like OpenSSH, to ensure a safe, encrypted session. It is the defacto standard for circuit level firewalls. All connections to a server, for example, appear to come from the gateway instead of a client. SOCKS is commonly used to manage firewalls and remotely access resources behind firewalls. It is not considered as secure as VPN. Also, it enables users to bypass web filters and other restrictions, so it's one of the protocols security teams must monitor for and manage. Various approaches to WAN communications exist. In this video, we look at four technologies: frame relay, ATM, MPLS, and SD-WAN.

Frame Relay

Frame relay, the technology that organizations are quickly moving away from, is designed to connect local area networks, forming a wide area network, a WAN, it replaces an earlier approach shown here of point-to-point connections using full or fractional T1 or T3 connections. Point-to-point connections are expensive and subject to failure. I once worked for a manufacturer set up like this. A connection between a plant and the main data center was via a single point-to-point T1 line. Environmental factors occasionally caused the cable to fail, resulting in an interruption in some operations. Frame relay reduces cost and introduces failover possibilities. As shown in this graphic, frame relay is a switched circuit managed by the carrier that uses packet switching to route traffic. If the circuit fails, traffic can be routed around the failure. An organization can contract for one or two frame relay services: switched or permanent. A switched circuit is a short-term virtual circuit or SVC. It's created whenever a circuit is needed for a transaction and then it's dropped. A PVC, or permanent virtual circuit, is always up and available, working like a permanent point-to-point connection. PVCs are the most common type of frame relay, and they come at a lower cost and add a level of failover not seen with point-to-point connections. Frame relay is good for standard application data, but it tends to fall short when using it for video and voice.

ATM

Asynchronous transfer mode, or ATM, is normally used by internet service providers on private long-distance networks, operating at layer 2 and it's a high-speed networking standard. It supports both voice and data communication designed to integrate voice and data networks. ATM doesn't use routing. Instead, it uses ATM switches that establish point-to-point connections that meet quality of service challenges in four ways. First, constant bit rate that specifies a constant peak cell rate or PCR; a variable bit rate or VBR, that establishes a sustainable cell rate or SCR, which can peak at a certain level, the PCR; Available bit rate or ABR, which guarantees a certain bandwidth; and unspecified bit rate or UBR, is the bandwidth available outside the available bit rate. A core protocol used over synchronous optical networking, or SONET, and synchronous digital hierarchy, or SDH, ATM WANs can be provisioned as a permanent circuit or as a connectionless service with a service provider implementing a VLAN in the cloud. Service providers can also provide ATM service via switched virtual circuits, or SVCs, already covered in this lesson.

MPLS

The use of only frame relay or ATM WANs gave way to MPLS, a protocol that blends the benefits of both, using labels to direct traffic. It retains the speed of ATM without having some of the ATM overhead, operating on the fence between OSI layers 2 and 3.

SD-WAN

As with any technology, researchers and designers always come up with a better way. Organizations are now considering software-defined WAN, or SD-WAN, to make WAN communication more efficient. As shown in this graphic, SD-WANs use software to intelligently route network traffic based on the most cost-effective efficient method available, whether MPLS, wireless cellular, or broadband internet, or other media. Changes are centrally controlled and immediate, not having to wait for carriers to make needed changes. That's it for this lesson. If you have questions, please ask. ...and until next time, be careful what you click.

Outro

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