Abstract Of Atm And Fiber Channel Protocol

Published Date: 02 Nov 2017

INWK 6111

Kevin Sakariya (B00610486)

Contents:

1.1 Abstract of ATM and FCP

1.2 Introduction of ATM

1.3 Protocol Architecture of ATM

1.4 Layers in ATM

1.5 Cell structure of ATM

1.6 Virtual Connections of ATM

2.1 Introduction of Fibre Channel Protocol

2.2 Architecture of FCP

2.3 Protocols and Layers of FCP

2.4 Class of services provided by FCP

3.1 Conclusion

4.1 References

1.1) Abstract of ATM and Fiber Channel Protocol

Now a days world migrate form frame relay to ATM and Fiber Channel Protocol(FCP) networks because ATM provides various Quality of Service (QoS) regarding various data like video ,voice ,text ,audio (real time and no real time).Also , ATM and FCP provide Greater speed then Frame relay. ATM can use different network like LAN, MAN, WAN.

ATM introduced into late 1980 and cumulative development till 1998.ATM network should be between user to network and network to network and user to user. ATM and FCP packets should be carries by another network protocol like Frame relay, SDH. This paper gives general overview about how ATM and FCP can work. ATM supports single topology but FCP supports more.

1.2) Introduction of ATM

Asynchronous Transfer Mode (ATM) is used to transfer different kind of data. It is a connection oriented protocol. It is also support reliable and unreliable communication. Now a days delay insensitive data send by packet switching, delay sensitive data (mostly Voice) send through PSTN.ATM convert data into the fix size cell .If data is long, it can segment data into multiple fixed size cell. After that it choose proper virtual circuit channel into virtual circuit path and send it. This cell routes and transports from different kind of networks. ATM network connects User to User, User to Network and Network to Network. To make up these connections it provides different interfaces. All interfaces have unlike cell formats. ATM admits multiple virtual paths into one physical interface.

1.3) Protocol Architecture of ATM

Following figure shows architecture of ATM.It is three layer protocols. In figure there are different kind of management use because it supports very high speed (25.6 Mbps-622.08Mbps).It contain fix size of cell.

Figure 1 – General architecture of ATM

User Plane It provides different information about data. It also handles end to end error and flow control mechanisms.

Control Plane It handles different control function like connection setup and disconnection.

Layer and Plane Management It manage the resource which provided by switches.

AAL  ATM Adaption Layer. It is divided into two different sub layers.

1) CS Convergence Sub layer

2) SAR Segmentation and Reassembly Sub layer.

ATML Asynchronous Transfer Mode Layer

PL Physical Layer. It further divided into two sub layer.

1) TC Transmission Convergence Sub layer

2) PMD Physical Medium Dependent Sub layer.

Following figure shows the various connections between switch to switch, users to switch.

Figure – 2 Logical and physical connection of ATM

This figure shows that logical connections between user to user are handle by the AAL and user to switch or switch to switch handle by ATM Layer. There is only one Physical connection over network which is handling by Physical Layer.

Following two interfaces are there which cell structures are different.

1) UNI User Network Interface.

2) NNI Network Network Interface.

UNI provides connection between user and ATM switches. NNI connects two ATM switches.

1.4) LAYERS IN ATM

There are three Main Layers in ATM Protocol.

AAL

ATM

Physical Layer

Figure – 3 Layers Comparison with OSI

Physical Layer

This layer is bounds all network. It transmits bits at transmitter. These bits are provided by upper layer of protocol. The other side bits are receive and these bits are forward to the upper layer. There are different physical medium can use for transfer bits like Optical Fiber, twisted Pair, SONET. There are two sub layers

TC

PMD

Transmission Convergence Sub layer of PL

It transmits and receives cells. It generates extra cells for matching speed. It also verify the HEC (Header Error Control).It also check that packets are acceptable by ATM network or not.

Physical Medium Dependent Sub layer of PL

It provides encoding and decoding of digital signal. Generally Manchester differentially encoding is use. It also handles time synchronization between sender and receiver .It is responsible for bit alignment and bit transfer. It handles medium electrical function.

ATM Layer

There are many functions which can handle by this layer. It establishes virtual path and virtual circuit between the devices and maintains it. It create cell header for frame this frame provided by the upper layer. Moreover, it provides routing of cells in network .ATM Layer responsible for sequential delivery of cells. In addition, it administers multiplexing and demultiplexing of lines. It governs flow control of cells. It also verify cell header.

ATM Adaption Layer

This layer blocks detail of ATM cells’ processing and creation from the higher layer or vice-verse. There are two sub layers into AAL.

CS

SAR

Convergence Sub layer of ALL

It handles class of service of different type of data. It provides AAL services to NSAP. It contains set of protocols to maintain classes of service to upper layer.

Class of Service

Description about service

Loss

Sensitive

Application of use

CBR

Continuous Bit Rate

Yes

T1 circuits

RT-VBR

Real Time-Variable Bit Rate

Yes

Video conferencing

NRT-VBR

Non Real Time-Variable Bit Rate

Yes

Multimedia email

ABR

Available Bit Rate

No

For Browsing the web

UBR

Unspecified Bit Rate

No

For File transfer in background

Table -1 Service and application

Segmentation and Reassembly Sub layer of AAL

It is use for divide upper layer data into 48 bytes cell from sender side and reassembling to other side. It also handles traffic shaping for it.

Characteristics of AAL

AAL1

Service

AAL3/4 Service

AAL4 Service

AAL5 Service

Time require between sources and destinations

Yes

No

No

No

Data rates

Constant rate

Variable rate

Variable rate

Variable rate

Connection communication

Connection-oriented

Connection- oriented

Connectionless

Connection- oriented

Information traffic types

Voice and circuit emulation

Data

Data

Data

Table – 2 AAL Services

1.5) Cell Structures of ATM Protocol

Every Packet ATM is called by cell. A cell has 53 bytes including header bytes. There 5 bytes header and 48 bytes long data.

Figure - 4 cell construction of ATM

There are two types of devices which is connects through ATM

ATM SwitchIt uses NNI for connect two ATM switches.

ATM end-pointPC, LAN Switch, Routers etc. It uses UNI for connection.

Capture.PNG

Figure – 5 Cell structures of ATM interfaces.

GFC (4 bits) Generic flow Control type governs flow control of cells. GFC is only in UNI. There are two types of it

1) Controlled AccessIf GFC bit is set then it is Controlled mode. It tells that congestion occur in circuit.

2) Uncontrolled AccessIn this mode bit is zero .Therefor; there is no congestion over circuit. This mode is default to all cells.

VPIVirtual Path Indicator is used for identify the virtual path. In UNI it is 8 bits long but NNI has 12 bits long.

VCI (16 bits) Virtual Circuit Identifier is uses to identify the channel into virtual path.

PTI (3 bits) Payload Type indicate that what kind of information in a cell like control or data.

CLP (1 bit) Cell Loss Priority is use for which cell discarded if congestion occur, if it set to one.

HEC (8 bits) Header Error Control is for correcting error in header. It use CRC for that

DATA (48 Bytes) User data or control information.

1.6) Virtual Connections of ATM

ATM has two types of virtual circuits.

Permanent Virtual Circuit (PVC) main lease line.

Switch virtual Circuit (SVC) it created on demand.

It is similar to the Frame Relay but main different is virtual path. Frame Relay does not have any virtual path but ATM does.

Following figure shows Virtual Circuit Channel and Virtual Circuit Path.

http://flylib.com/books/4/329/1/html/2/images/fig29-2.jpg

Figure – 6 VP and VC in ATM

VP is group of VCC which has same end points. Advantage of VP is it control network cost .For establishment of Virtual path 20 bytes of NSAP Address necessary. After that VCC is only need IP address of end device. Therefore VP is only one time need to establish after that it do not need. Hence, Network cost is less and maintenances is very easy.

Following figure is describes how VP and VCC is establish between two devices.

http://flylib.com/books/4/329/1/html/2/images/fig29-3.jpg

Figure – 7 Flowchart of VP and VC connection

VP and VCC should be unidirectional or bidirectional. Moreover, because of VP reducing the processing time to each node and also decrease the connection set up time. It increases network reliability.

2.1) Introduction of Fibre Channel Protocol

Fibre Channel focuses on transfer data in very high speed, like gigabits per second, between mainframe, workstation, devices etc. through the various hop like router, switch. FCP is design by ANSI. It is combination of two data communication types, point to point type (Channel) and network type. Point to point is use for transfer data between hard disk and PC. There is various numbers of hops into networks for transmitting small chunk of data. Combination of this two is Fibre Channel Protocol. Now a days all data are stored in cluster and server so FCP is very use full to handle very fast data transfer.

Figure – 8 General use of FCP

2.2) Architecture of Fibre Channel

It is set of various protocols. FCP provides serial connection between units in network. These units are generally call hop or node. Each hop has one or more serial connection. This connection is full duplex. This connection establishes between node port and fabric port (intelligent fiber switch port).There is three main topologies for FCP.

Point to Point Topology

Arbitrary Loop Topology

Switch Fabric Topology

Point to Point Topology 

Point to Point topology provides direct communication between two nodes. For information transmission connection is establish between a workstation and storage server. This connection is maintained though out data transfer. There is no need to routing or collision.

Figure – 9 Point to Point Topology of FCP

Arbitrary Loop Topology

In Arbitrary Loop topology, there are individual connection between nodes and storage but it is in loop. Therefore, at a time only one connection is available for use. This all connection is time shared. This topology do not use switch. Maximum 127 devices are possible in loop. This connection is either full or half duplex. It is arbitrary decides that which hop can transmit information on the line.

Figure – 10 Arbitrary Loop Topology of FCP

Switch Fabric Topology 

Today, Storage Area Network uses switch fabric topology. In this topology all stations are connected to fabric switch. This switch maintains port to port connection between the node and storages server.

Figure -11 Switch Fabric Topology of FCP

2.3) Protocol and Layers of Fiber Channel

FCP has 5 layers architecture. These layers introduced because it simplifies the implementation and standards.

Figure -12 General Protocol and Layer Architecture of FCP

1) FC – 0 Layer 

This layer Contain all the physical and electrical characteristics of medium. It supports all mediums like twisted pair, optical fiber etc.

2) FC – 1 Layer 

This layer responsible for encodes and decodes of data. It first encodes information into 8 bit or 10 bit combination after that it transmits data.

3) FC-2 Layer 

This layer governs framing and flow control. It also provides various services relative to type of data. There are some rules which use for the data transmission.

Ordered Set  It contains for transmission words which is four bytes long. These words include the special character which has different meaning. It gives word synchronization and word alignment.

Frame

The main focus is the developing frame for transmitting data over network. Following figure shows frame format.

http://hsi.web.cern.ch/HSI/fcs/spec/ov4.gif

Figure -13 Packets and Header Detail of FCP

Sequence 

Sequence is the order number which is related to frame. This sequence number gives that it is one direction or bi direction from one node port.

Exchange 

It gives that sequence is unidirectional or bidirectional from two port.

Protocol 

Protocol gives that what kind of service use by the fibre channel. This service depends on the higher layers.

Flow Control 

It governs the flow between end to end nodes and fabrics switch to end node too.

4) FC – 3 Layer 

This layer provides the advance services like multicasting. Some functions are below.

Multicasting  One information can transmit to the group of nodes in to network.

Group Hunt  Response from the same alias nodes addresses.

It send single information frame simultaneously into different connection lines.

5) FC – 4 Layer 

It gives simple integration over existing standards. It is highest layer which is mapping the application over FCP. It supports various networks and protocols like

FDDI Fibre Distributed Data Interface.

SCSI  Small Computer System Interface.

IPI  Intelligent Peripheral Interface.

Token Ring

IP

ATM

Etc.

2.4) Class of Services provided by FCP

For effective transmission of different type of data like voice, video, text, graphics, files etc. It provides some service classes.

Class1  It is connection oriented and dedicate connection between nodes. It is reliable communication i.e. acknowledgement given by receiver. It is called circuit switch technology. It gives maximum bandwidth over connection.

Class 2  It gives connectionless service. Acknowledgements are out of order.

Class 3  It provides datagram communication .Therefore, it does not guarantee about frame delivery.

Class 4  It is use virtual circuit type service. Hence, it is connection oriented.

Class 6  It gives unidirectional connection between nodes. It also gives multicast reliable connection.

3.1) Conclusion

ATM gives various ranges of services for different kind of data. However, Frame Relay is not suitable for voice and video type data. Also, ATM gives much higher speed compare to Frame Relay. Hence, ATM is use for high speed multiplexing on the MAN, WAN and LAN too. Fibre Channel Protocol gives very much higher speed compare to ATM. It is costly compare to ATM. Therefore FCP uses only in SAN and long distance data transfer.