Example of Older 10Base2 Card BNC Source: Black Box
Example of Older 10BaseT Card RJ 45 ISA Source: Black Box
Example of Older Combo Card Combo Source: Black Box RJ 45 BNC
D-Link Fast Ethernet Card (100BaseTX)
D-Link 100BaseTX Specs (Source D-Link)
A manageable 10/100MB Dual Speed Ethernet PCI Network Interface Card with Wake-On-LAN (WOL)
Fully compliant with IEEE802.3 10Base-T, IEEE 802.3u 100Base-T specifications
Supports ACPI/WOL (Advanced Configuration Power Management Interface) feature, IP Multicast packet filtering, PXE (PreBoot execution Environment) Boot ROM, IEEE 802.1p, IEEE 802.1Q, and DMI (Desktop Management Interface).
A Note on Remote Wake on LAN (Source: Intel)
A remote wake-up technology that enables you to remotely power systems "on" for off-hours maintenance. A result of the Intel-IBM Advanced Manageability Alliance and part of the Wired for Management Baseline Specification, this technology helps save time on automated software installations, upgrades, disk backups and virus scans. Equally important, it increases end-user productivity by moving such planned disruptions to off-hours.
Fast Ethernet PC Multi-Port Card NIC and modem connections
Fast Ethernet Card Specs. The D-Link DMF-560TX is a 10/100Mb Dual Speed Ethernet PC Card with an integrated V.90/K56flex Data/Fax Modem. The DMF-560TX is targeted at notebook and laptop users that connect to a wide variety of data-communications devices and services, and require access to faster technologies. Laptop users are able to seamlessly connect to both Ethernet and Fast Ethernet LANs, as well as send and receive faxes, connect to the Internet, and dial into a Remote Access Server or PC using this one PCMCIA PC Card solution. The DMF-560TX strictly adheres to the IEEE Ethernet standards and the ITU Data Communications and Modem standards in order to ensure maximum interoperability. The DMF-560TX attempts to connect at the highest speed supported by an ISP, LAN, host modem, or fax machine and automatically defaults to a lower speed until a stable connection can be created.
Wireless PC Card Specs D-Link Air DWL-650 PC Card Type-II 11Mbps Wireless LAN Adapter The D-Link DWL-650 is an IEEE 802.11b compliant PC Card Type-II 11Mbps wireless LAN adapter. The DWL-650 will operate in 2.4 GHz Direct Sequence Spread Spectrum (DSSS) for wireless networks in the home or office environment. It is designed to operate in 3.3V or 5.0V DC slots. In addition, the DWL-650 uses a 64/128-bit WEP (Wired Equivalent Privacy) Encryption for a secure network connection. The D-Link DWL-650 can operate in either Ad-Hoc mode (Peer-to-Peer networking without access point) or Infrastructure mode (Peer-to-Peer networking using an access point). In Infrastructure mode, the DWL-650 can be connected to a broadband residential gateway or a DSL/Cable modem for high-speed wireless Internet access on the existing network.
Wireless PC Card Specs The DWL-650 can transmit data at 11, 5.5, 2 or 1 Mbps per channel. The DWL-650 transmit rate values can be manually selected for Auto Select 1 or 2 Mbps, Fixed 1 Mbps, Fixed 11 Mbps, Fixed 2 Mbps, Fixed 5.5 Mbps and Fully Auto. The DWL-650 has full mobility and seamless roaming from cell to cell as well as across access points. The range of coverage per cell for indoor use is up to 328 feet and up to 984 feet per cell for outdoor use. The DWL-650 comes with an internal non-detachable diversity patch antenna and one built-in green LED indicator for power, network link and activity. The DWL-650 is compatible with Windows 98, Windows ME, Windows 2000, Windows XP.
Wireless PCI Card
Wireless PCI Card Specs The D-Link Air DWL-520 is an IEEE 802.11b wireless PCI adapter. The DWL-520 provides an integrated PCI solution that will operate within the 2.4 GHz Direct Sequence Spread Spectrum (DSSS) for wireless networks in the home or office environment. Along with the advanced wireless technology that is incorporated into the DWL-520, wide range motherboard support is assured by compliance to the latest PCI 2.2 standard interface. The DWL-520 is the solution for users and network administrators looking for the convenience offered by a wireless connection.
Wireless PCI Card Specs Cont.
The D-Link DWL-520 can operate in either Ad-Hoc mode (Peer-to-Peer networking without an access point) or Infrastructure mode (Peer-to-Peer networking using an access point). In Infrastructure mode, the DWL-520 can be connected to a wireless residential gateway with a broadband connection to enable wireless sharing of the High-speed Internet access.
The DWL-520 can transmit data at rates of 11Mpbs, 5.5Mbps, 2Mps and 1 Mbps per channel. With its detachable antenna using a reverse SMA connector, the DWL-520 has an effective range of up to 230 feet for indoor use and up to 984 feet in an outdoor environment. In addition, the DWL-520 supports 64/128-bit WEP (Wired Equivalent Privacy) Encryption for network security.
Wireless 5 GHz
Wireless 5 GHz Specs
Next generation of wireless products with its high-performance D-Link Air Pro series of 5GHz networking technology.
Designed for indoor use, the D-Link Air Pro DWL-A650 is a powerful notebook PC CardBus adapter that allows users to have mobile access to networks. It provides roaming capabilities from cell to cell and network to network.
At 54 Megabits per second (Mbps), the D-Link Air Pro DWL-A650 5GHz high speed wireless CardBus adapter delivers the fastest standards-based wireless technology in the industry. With IEEE 802.11a standard compliance, the D-Link Air Pro DWL-A650 high-speed wireless adapter provides excellent network interoperability.
Wireless 5 GHz Specs (Continued)
A proprietary “Turbo” mode allows the D-Link Air Pro DWL-A650 to operate at significantly greater data rates up to 72Mpbs. Eight non-overlapping channels create less interference, which supplies higher average cell throughput to clients. The D-Link Air Pro DWL-A650 employs enhanced 152-bit Wired Equivalent Privacy (WEP) and Dynamic Key Exchange to protect data from unauthorized access.
The D-Link Air Pro DWL-A650 is easily installed into a laptop PC to provide connectivity directly to another wireless enabled device (ad-hoc mode) or through an 802.11a based access point (infrastructure mode).
END OF MODULE
MODULE NIC Resources
Base memory address, if provided
DMA, if provided
Must be unique for each device, unless it is steered
An NIC requires an IRQ
IRQ is used to gain the attention of the CPU
There are a limited number of IRQs available on a computer
IRQ Assignment (learnthat.com) IRQ Device 0 Timer 1 Keyboard 2 Wired to IRQ 9 3 COM 2 (COM 4) 4 COM 1 (COM 3) 5 Available (often LPT2, sound cards, or network cards) 6 Floppy Disk Controller 7 LPT1 8 Clock 9 Wired to IRQ 2 10 Unused 11 Unused 12 Mouse Port 13 Coprocessor 14 Hard Disk Controller 15 Unused
Must be unique to each device
Each device of port must have an I/O address
The NIC must have an I/O Address as well
Common I/O Address Assginemnt (learnthat.com) Address (Hex) Device 00-0F DMA Controller 20-21 Interrupt Controller 40-43 Timer 1F0-1F8 Hard Disk Controller 200-20F Joystick Controller 238-23B Bus Mouse 278-27F LPT2 2E8-2EF COM4 Serial Port 2F8-2FF COM2 Serial Port 300-30F Ethernet Card 330-33F MIDI Port 378-37F LPT1 Port 3E8-3EF COM3 Serial Port 3F0-3F7 Floppy Disk Controller 3F8-3FF COM1 Serial Port
I/O Address ( www.techencylopedia.com )
There is a 64K address space for I/O addresses, although typically less than 1K is used. Each board that uses an I/O address contains a few bytes of memory (16, 32, etc.) set to a default address range. One or more alternate addresses is also provided to resolve conflicts with other boards. These I/O spaces are a bunch of tiny memory banks scattered over different devices. As long as each one is set to a different address, the CPU can transmit signals to the appropriate boards without conflict. Following are the default I/O addresses for the serial and parallel ports in a PC.
I/O Address Continued ( www.techencylopedia.com )
An I/O address operation takes place as follows. If a program needs to send a byte to the serial port, it issues an OUT instruction to the CPU with the address of that serial port. The CPU notifies the address bus to activate the I/O space, not regular memory, and the address bus signals the appropriate byte location on the board. The CPU then sends the data character over the data bus to that memory location.
Base Memory Address
Must have a unique range for the NIC card
Some older cards did not require the base memory address to be specified
Direct Memory Access
Channels are assigned for DMA
Not all the NIC cards have DMA
Newer PCI technologies used for expansion slots have made DMA somewhat obsolete
DMA Use (Source learnthat.com)
In most PCs, there are 8 DMA Channels.
In most modern PCs, DMA shouldn't be used as it just slows it down. But, older PCs may use DMA.
Channels 4-7 are usually available, while Channel 0 is used to refresh DRAM, Channel 1 is used by a hard disk controller or sound card, and Channel 2 is usually used by the floppy disk controller.
Resource Allocation on a NIC
Examining the Network Resources Device Manager NIC Properties Resources
END OF MODULE
MODULE Network Connectors and Hubs
An interface between the NIC and the cables
Used at both ends of a bus network
Terminator T Connector
Example of T-Connector and Terminator T Connector Terminator Source: Black Box
Connectors : Hubs
Simply provides the physical and the electrical connection for the network
A Multi-port device
Amplifies LAN signals
Has built-in manageability
Some are manageable hubs
Connectors : Passive Hub MAU WS WS Hub Connecting A Token-ring Network WS
A Manageable Hub/ Switches Backbone Manageable Hub/ Switch Remote Workstation WS WS WS Remote Monitor Active Hub
LAN Management Software
Monitor the network traffic through each of the ports
Standardized protocol for remote management exists
SNMP (Simple Network Management Protocol)
A major protocol used in the management of networks
A number of LAN management software is based on the SNMP protocol
SNMP Cont. (Source: Cisco)
The Simple Network Management Protocol (SNMP) is an application-layer protocol designed to facilitate the exchange of management information between network devices.
By using SNMP-transported data (such as packets per second and network error rates), network administrators can more easily manage network performance, find and solve network problems, and plan for network growth.
SNMP is a relatively simple protocol, yet its feature set is sufficiently powerful to handle the difficult problems presented in trying to manage today's heterogeneous networks.
Today, SNMP is the most popular protocol for managing diverse commercial internetworks as well as those used in universities and research organizations.
Like the Transmission Control Protocol (TCP), SNMP is an Internet protocol.
There are two versions of SNMP: Version 1 and Version 2.
Most of the changes introduced in Version 2 increase SNMP's security capabilities. Other changes increase interoperability by more rigorously defining the specifications for SNMP implementation.
SNMP's creators believe that after a relatively brief period of coexistence, SNMP Version 2 (SNMPv2) will largely replace SNMP Version 1 (SNMPv1).
Obtain additional information on the following LAN troubleshooting software
Example of a Hub Used in Ring Network Source: Black Box
Example of Hubs Used in the Star Network Stackable Hubs Source: Black Box
END OF MODULE
MODULE Server and Workstation Hardware
Give an overview of the different types of the server hardware
Discuss the desired characteristics of a server
Provide a specification for a workstation
Mini and large computers are used as servers
In a client-server environment, the server also acts as an engine for database execution
In general, the server is used for the sharing of stored data and application
Desired Characteristics of Server: Processor and Storage Requirement
Latest Pentium Processor for example
Multiple processors, if necessary
Large storage space
Several gigabytes at a minimum
Actual requirement will vary with LAN size
Fast disk access speed
Less than 10 ms, for example
Versatile CD-ROM access (Towers)
Intel Pentium 4, 32-bit processors
Intel Itanium 64-bit processors
Special Xeon processors meant for servers
Symmetric Multi-Processing (SMP)
Spark (Sun), AMD, Motorola, IBM’s own processors etc.
SMP (symmetric multiprocessing) is the processing of program s by multiple processor s that share a common operating system and memory . In symmetric (or "tightly coupled") multiprocessing, the processors share memory and the I/O bus or data path. A single copy of the operating system is in charge of all the processors. SMP, also known as a "shared everything" system, does not usually exceed 16 processors.
Chip sets designed for servers to boost I/O operation
Hard Disk Technologies
Serial ATA (SATA)
Fiber channel storage
Overview of Storage Technologies
SCSI, Small Computer Systems Interface, is widely used in mid- to high- performance workstations and servers.
SCSI offers faster transfer rates than ATA / IDE , the interface most commonly used in desktop PCs.
In general, ATA/IDE is considered easier to implement and less expensive than SCSI but does not offer as many features.
For example, SCSI can support up to 16 devices on a single bus (IDE offers two), generally offers faster throughput, uses less CPU horsepower during operation, and is therefore more efficient in demanding multiple initiator applications for multi-users and uses. This is significant because it allows the processor to perform more commands at one time making for greater efficiency.
SCSI Standards SCSI Fast SCSI Ultra SCSI Wide Ultra SCSI Ultra2 SCSI Wide Ultra2 SCSI Ultra3 SCSI Data transfer rates max. Bus speed (MB/sec) 5 10 20 40 40 80 160 Maximum Data Bus width (bits) 8-bit 8-bit 8-bit 16-bit 8-bit 16-bit 16-bit Max. cable length (meters) 6 3 1.5 - 3 1.5 - 3 12 12 12 Max. device support 8 8 8 - 4 8 - 4 8 16 16
SCSI Terms (source: IBM)
The SCSI terms Fast, Ultra, or Ultra2 typically refer to data rate increases that move data faster on the bus, while the term Wide refers to adding more lanes to the bus, typically transferring 16 bits of data at one time rather than eight bits. Other differences between the standards include the maximum cable length and the number of devices that can exist on the same SCSI bus.
Ultra 3 SCSI (source: IBM)
As one of the recent developments in SCSI, Ultra3 SCSI presents significant feature and benefit enhancements over Ultra2 SCSI products. Ultra3 SCSI products are designed to offer, at a minimum, the following features: Cyclic Redundancy Check (CRC) , domain validation , and double transition clocking , none of which are available in Ultra2 SCSI products.
These features are designed to improve speed, performance, and overall manageability of SCSI.
Ultra 160 (source: IBM)
The subset of Ultra3 that includes the three features, Cyclic Redundancy Check (CRC) , domain validation , and double transition clocking , is commonly called Ultra160, for its speed 160MB per/sec. The main difference between Ultra3 and Ultra160 is that Ultra3 implementations may offer other features in addition to those listed above.
The term ATA stands for Advanced Technology Attachment , for the standard bus interface on the original IBM AT computer. This interface also is called IDE , for Integrated Drive Electronics; ATA is the official ANSI (American National Standard Institute) standard designation.
Also known as Ultra DMA , ATA is generally the least expensive hard drive interface; many computer motherboards include ATA controllers and cable connectors that typically control the "C" drive that contains the operating system. However, ATA is a slightly slower drive interface, so it is used primarily in single user computer applications or low-end RAID systems.
ATA Variations ATA/ ATA-2 Ultra-ATA/33 Ultra-ATA/66 Data transfer rates max. Bus speed (MB/sec) 8.3 16.6 33 66 Maximum Data Bus width (bits) 16-bit 16-bit 16-bit 16-bit Max. device support 2 2 2 2
Serial ATA (SATA)
Fiber Channel - Arbitrated Loop (FC-AL) is an exceptionally high-bandwidth industry-standard interface primarily targeted toward high-end servers and similar demanding applications.
FC-AL uses fiber optic cabling in a loop configuration to produce maximum transfer speeds of 100 MB/second and is designed to connect up to 127 devices as far as 10 kilometers apart, enabling data storage in remote, secure locations distant from the server.
More on Fiber Channel
FC-AL devices can be dual ported, providing two simultaneous input/output sessions that doubles maximum throughput, and FC-AL enables "hot swapping," so you can add and remove hard drives without interrupting system operation, an important option in server environments.
FC-AL adapters tend to cost more than SCSI adapters.
PCI BUS Technology
PCI is preferred
32-bit and 64-bits
An extension to the PCI Bus interface
General PCI standards
PCI 1.0, 2.0 and 3.0
A Note on PCI-X 2.0 (Source PCISIG)
PCI-X 2.0 is an evolutionary, backward compatible technology that builds on the foundation of PCI and PCI-X while offering bandwidths 4 times higher than PCI-X without increasing pin-count.
These new, higher bandwidths are ideal for server-oriented adapter cards in the areas of Fibre Channel, RAID, networking, InfiniBand™ Architecture, SCSI, iSCSI, and other high-bandwidth technologies.
PCI-X 2.0 Performance Advantage (Source PCISIG)
Doubles and Quadruples PCI-X bandwidth.
Enables 10Gb Ethernet, 10Gb Fiber Channel, InfiniBand™ Architecture, and other IO technologies.
Performance 32 times higher than the first generation of PCI.
Desired Characteristics of Server: Bus and Memory Technologies
Better bus technology
In excess of 512 Mbytes
SDRAM or similar memory technology functioning at 10 nanoseconds or less
The 168-pin SDRAM is also known as the DIMM chips as opposed to the 72-pin SIMM chips
182 DDR RAM
Desired Characteristics of Server: Reliability
Good back-up facilities
Uninterruptible Power Supply (UPS)
Fault Tolerant Feature for Servers
RAID storage technology
A system based on multiple disk
Redundant power supply
Hot-swappable power supply
Hot Pluggable and Hot Swappable
When a card or a device is plugged into the computer (PCI), the computer will recognize the device automatically and install the device
An example is a NIC
A device that can be removed and replaced without having switch off the computer
An example is a hard drive
Most applications are executed at the workstation in the case of a file server
Therefore, it must be powerful in terms of the processor and the memory
As a rule of thumb, the workstation must be as powerful as it were to be used as a standalone unit to run the applications
Workstation Processor and Memory
Pentium class processor
32 Mbytes or more
DIMM preferred although fast EDO SIMM may also be used
Workstation Storage and Compatibility
Storage in gigabytes
Important in a client-server environment
Front-end tools are stored on the workstation
Speed of storage
Ultra DMA or SCSI preferred
EIDE may also be used
Hardware components with appropriate drivers for the client operating system
Power surge protector
Uninterruptible Power Supply (UPS), for critical applications
END OF MODULE
An Overview of Repeaters
Used for extending the physical span of a network
An example is the extension of the distance between a hub and a node
Span is often limited by design considerations
The span is limited to 500 meters
A Repeater Connection Expanding the Span of the Network Source: Black Box
Another Example of Repeater Connection Extending the distance between the backbone and the nodes. Source: Black Box
Current Day Use of Repeaters
Fiber optic repeaters are used for extending the distance between two nodes in a link or a network
Operations of a Repeater Within the ISO OSI Model
Operates at the lower level of the ISO OSI model, namely layer 1
Medium Physical Layer Repeater Medium Physical Layer
Other Devices Used for Extending the Span of a Network
Another Layer 1 Device
This is simply an electrical connecting device used in the configuration of a network
The topology in this case would be that of a star topology
END OF MODULE
An Overview of a Bridge
A device used for connecting two LANs operating usually under the same protocol
There are bridges that connect LAN segments operating under different protocols
Currently, the term bridge is loosely being used to describe different interconnecting devices
Used now for connecting LANs operating under different protocols as well
Purpose of a Bridge
Facilitate the movement of data packet from one network segment to another
Not a sophisticated internetworking device
Bridge does not perform the routing of information to different segments of a network
Connects two network segments and not multiple network segments
Bridge : ISO-OSI Layer of Operation Bridge X Medium X Medium Physical Layer Physical Layer Data Link Layer Data Link Layer A simple bridge operates at the second layer of the ISO model.
Practical Bridge Implementations
Local and Remote Bridges
Connects two different LANs located locally
Connects LAN segments that are geographically apart
An example is a device that provide dial-up access to a LAN
A Practical Bridge Example
END OF MODULE
Switch Definition and Purpose
A switch is defined as a device that allows a LAN to be segmented
The segments will operate under the same protocol
Difference Between a Switch and a Bridge
A switch focuses on segmenting a LAN
A bridge is concerned with linking two network segments that operate under different protocols
Purpose of a Switch
Improve the network performance and reliability
Better manage the network in general
Switch : ISO-OSI Layer of Operation Switch X Medium X Medium Physical Layer Physical Layer Data Link Layer Data Link Layer A simple Switch operates at the second layer of the ISO model.
Layer 3 Switches
Some switches operate at Layer 3 of the ISO-OSI model
These switches perform routing as well
Performance Improvement in Segmented Networks
Performance is improved especially in the case of a bus network
Multiple bus paths are now available for communication
Each segment can engage in simultaneous communication within itself
Easier to isolate a problem to a segment
Thus, better manage the entire network
When one segment does not function, the other segments can continue to function
Offers better reliability to at least part of the function
Switches in Ethernet and Token Ring LANs
Switches were originally designed for segmenting Ethernet LANs
Used extensively in configuring large Ethernet bus LANs
Physically the network configured would still largely remain based on the star topology
Switches are now available for token ring networks as well
Use of Switches in Linking LAN Segments Switch Hub Hub WS Server WS Server Segment 1 Segment 2 Crossover Traffic
Using A Switch to Link Bus LAN Segments Switch Segment 1 Segment 2
Use of Switches in Internetworking
Because the typical inter-networking connection involves multiple segments, the use of a switch is more common than the use of a bridge
Use of Switches for Higher Bandwidth WS 100 MBps Switch WS WS WS Each port in theory has a bandwidth of 100 Mbps.
END OF MODULE
MODULE Switching Technology
Explain the basic operation of a switch
List the switching technologies and describe their operation
Cut-through and store-and-forward technologies
The Basic Operation of Switches
A data packet is analyzed
Receiver’s addresses is checked
If it indicates the receiver to be in the same segment, the packet is dropped
If it indicates the receiver to be in a different segment, the packet is forwarded to a different segment
Receiver’s Address Sender’s Address Data
There are two major types of switching technologies
In each of the two cases of switching technologies no protocol conversion takes place
Forwarding and filtering are done at the MAC layer
A switch switches the traffic based on MAC address
END OF MODULE
The Purpose of a Router
Connect LANs operating under different protocols
The LANs connected are better known as sub-networks instead of network segments
The term segments is nevertheless used in practice
Each segment basically represents a subnet
A router is a true internetworking device
Connects different sub-networks together
Establishes a logical path of communication between the sub-networks
Contributes to the modular construction of a network
Network itself is better managed
Network resources are better utilized
Internetworking with a Router IEEE 802.3 Sub-network IEEE 802.5 Sub-network PC-NFS Sub-network Router
Routers, Switches and Hubs in Perspective Switch Switch Hub Hub S WS WS WS Router Hub S WS Hub WS S Hub WS WS Hub WS S Sub-network 1 Sub-network 2 Backbone
Difference Between Routers, Switches and Hubs
Simply provides the mechanical and electrical connections between the nodes
Examine the data packet for the destination address
Do not alter the data packets
Switches based on MAC address
Basically a Layer 2 device
Examine and alter the data packet format
Perform protocol conversion
Routes based on IP address
Basically a Layer 3 device
Requires more processing power compared to switches and bridges
Operations fall within the network layer of the ISO-OSI communication model
Router : Network Layer Interface X MEDIUM X MEDIUM PHYSICAL LAYER PHYSICAL LAYER DATA LINK LAYER DATA LINK LAYER NETWORK LAYER ROUTER NETWORK LAYER
Devices and Layers PHYSICAL LAYER DATA LINK LAYER NETWORK LAYER Switches Routers Hubs and Repeaters Switches Layer 1 Layer 2 Layer 3
A Practical Router Example Router Router Router Router Router
END OF MODULE
Build a small network consisting of 4 workstations and 1 server for a small business
Provide details of the hardware in terms of the types of hardware and the cost of the hardware
Connect the network to the Internet
Again provide the cost associated with the hardware required to make the connection
In both of the above cases, also provide a schematic diagram showing the network connections
An Introduction to Gateways
Gateways are comprehensive internetworking devices
They can be computers themselves
Gateways in the Past
They were the only devices that could be used for internetworking
Computers of the past were not designed with network connections in mind
Interconnection of different computer systems has to be managed and driven by an advanced device such as a gateway
The Present Scenario
Computers are now designed with due consideration given to network connections
Larger networks could today be configured using internetworking devices
Routers, switches, hubs etc.
Even, mainframes can be connected easily using the above internetworking devices
In the past, because of the different nature of the network (SNA), connecting a mainframe to a LAN often required a gateway (SAN Gateway)
Use of Gateways at Present
Used in the rare occasion when neither of the internetworking devices could be used for connecting the sub-networks together
Connection of a legacy mainframe system to a bus LAN
Rule of Thump
Gateways are used for interconnecting vastly differing computing environments together
SNA Gateway SNA Gateway WS WS Mainframe LAN - Ethernet IBM - SNA FEP NIC Card Gateway software Gateway Interface Card
Gateway’s Functional Relationship to the ISO-OSI Model Application Presentation Session Transport Network Data Link Physical Gateway Application Presentation Session Transport Network Data Link Physical