2 port

OSI Layer Physical Component

7-Application

Applicaton Software

LAN-Compatible Software E-Mail, Diagnostics, Word Processing, Database

Network Applications

6-Presentation

Data- Conversion Utilities

Vendor-Specific Network Shells and Gateway™ Workstation Software

5-Session

Network Operating System

SPX

NetBIOS

DECnet™

TCP/IP

AppleTalk®

4-Transport

Novell® NetWare® IPX™

PC LAN

LAN Mgr

DECnet

PC/TCP®

VINES™

NFS

TOPS®

Apple Share®

3-Network Control

2-Data Link

Network

E

A

TR

P

TR

E

TR

E

E

E

P

E

P

1-Physical

E=Ethernet; TR=Token Ring; A=ARCNET®; P=PhoneNET®

With the rapid development of computer networks over the last decade, high-end switching has become one of the most important functions on a network for moving data efficiently and quickly from one place to another.

Here’s how a switch works: As data passes through the switch, it examines addressing information attached to each data packet. From this information, the switch determines the packet’s destination on the network. It then creates a virtual link to the destination and sends the packet there.

The efficiency and speed of a switch depends on its algorithms, its switching fabric, and its processor. Its complexity is determined by the layer at which the switch operates in the OSI (Open Systems Interconnection) Reference Model (see above).

OSI is a layered network design framework that establishes a standard so that devices from different vendors work together. Network addresses are based on this OSI Model and are hierarchical. The more details that are included, the more specific the address becomes and the easier it is to find.

The Layer at which the switch operates is determined by how much addressing detail the switch reads as data passes through.

Switches can also be considered low end or high end. A low-end switch operates in Layer 2 of the OSI Model and can also operate in a combination of Layers 2 and 3. High-end switches operate in Layer 3, Layer 4, or a combination of the two.

Layer 2 Switches (The Data-Link Layer)

Layer 2 switches operate using physical network addresses. Physical addresses, also known as link-layer, hardware, or MAC-layer addresses, identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process.

Switches operating at Layer 2 are very fast because they’re just sorting physical addresses, but they usually aren’t very smart—that is, they don’t look at the data packet very closely to learn anything more about where it’s headed.

Layer 3 Switches (The Network Layer)

Layer 3 switches use network or IP addresses that identify locations on the network. They read network addresses more closely than Layer 2 switches—they identify network locations as well as the physical device. A location can be a LAN workstation, a location in a computer’s memory, or even a different packet of data traveling through a network.

Switches operating at Layer 3 are smarter than Layer 2 devices and incorporate routing functions to actively calculate the best way to send a packet to its destination. But although they’re smarter, they may not be as fast if their algorithms, fabric, and processor don’t support high speeds.

Layer 4 Switches (The Transport Layer)

Layer 4 of the OSI Model coordinates communications between systems. Layer 4 switches are capable of identifying which application protocols (HTTP, SNTP, FTP, and so forth) are included with each packet, and they use this information to hand off the packet to the appropriate higher-layer software. Layer 4 switches make packet-forwarding decisions based not only on the MAC address and IP address, but also on the application to which a packet belongs.

Because Layer 4 devices enable you to establish priorities for network traffic based on application, you can assign a high priority to packets belonging to vital in-house applications such as Peoplesoft, with different forwarding rules for low-priority packets such as generic HTTP-based Internet traffic.

Layer 4 switches also provide an effective wire-speed security shield for your network because any company- or industry-specific protocols can be confined to only authorized switched ports or users. This security feature is often reinforced with traffic filtering and forwarding features.

Common Criteria (EAL4+) defines a common set of tests regarding the process of the design, testing, verification, and shipping of new security products. Common Criteria enables customers to assess a level of trust in how a product has been designed, tested, built, and shipped.

TEMPEST testing, while classified, is regarded as a process that assesses the threat of data linking by various covert electromagnetic eavesdropping mechanisms. The TEMPEST designation is often required by military organizations. TEMPEST, as a security standard, pertains to technical security countermeasures, standards, and instrumentation that prevent or minimize the exploitation of vulnerable data communications equipment by technical surveillance or eavesdropping.

Both testing standards are important, they just test for different things.

TEMPEST-Secure KVM Switches
For 2 or 4 ports, with USB, and DVI-I or VGA the ServSwitch Secure KVM Switch with USB (page 382) provides control and separation of up to four PCs connected to secure and unsecure networks through just one keyboard, monitor, and mouse.