J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
UNIT – I HIGH SPEED NETWORKS
Frame Relay Networks – Asynchronous transfer mode – ATM Protocol Architecture, ATM logical
Connection, ATM Cell – ATM Service Categories – AAL, High Speed LANs: Fast Ethernet, Gigabit
Ethernet, Fiber Channel – Wireless LANs: applications, requirements – Architecture of 802.11
1. FRAME RELAY:
Frame Relay often is described as a streamlined version of X.25, offering fewer of the robust
capabilities, such as windowing and retransmission of last data that are offered in X.25.
Frame Relay Devices
Devices attached to a Frame Relay WAN fall into the following two general categories:
• Data terminal equipment (DTE) • Data circuit-terminating equipment (DCE)
DTEs generally are considered to be terminating equipment for a specific network and
typically are located on the premises of a customer. In fact, they may be owned by the customer.
Examples of DTE devices are terminals, personal computers, routers, and bridges.
DCEs are carrier-owned internetworking devices. The purpose of DCE equipment is to provide
clocking and switching services in a network, which are the devices that actually transmit data
through the WAN. In most cases, these are packet switches. Figure 10-1 shows the relationship
between the two categories of devices.
1.1 FRAME RELAY NETWORKS:
 Designed to eliminate much of the overhead in X.25
 Call control signaling on separate logical connection from user data
 Multiplexing/switching of logical connections at layer 2 (not layer 3)
 No hop-by-hop flow control and error control
 Throughput an order of magnitude higher than X.25
1.2 FRAME RELAY ARCHITECTURE:
Figure :- Comparison of X.25 to frame relay architecture




X.25 has 3 layers: physical, link, network
Frame Relay has 2 layers: physical and data link (or LAPF)
LAPF core: minimal data link control
o Preservation of order for frames
o Small probability of frame loss
LAPF control: additional data link or network layer end-to-end functions
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
LAPF CORE FUNCTIONS:
 Frame delimiting, alignment and transparency
 Frame multiplexing/demultiplexing
 Inspection of frame for length constraints
 Detection of transmission errors
 Congestion control
Figure:- Frame relay Virtual Connections
1.3 USER DATA TRANSFER (STANDARD FRAME RELAY FRAME):
Standard Frame Relay frames consist of the fields illustrated in Figure below
Each frame relay PDU consists of the following fields:
Flag Field. The flag is used to perform high level data link synchronization which indicates the
beginning and end of the frame with the unique pattern 01111110. To ensure that the 01111110
pattern does not appear somewhere inside the frame, bit stuffing and destuffing procedures are
used.
Address Field. Each address field may occupy either octet 2 to 3, octet 2 to 4, or octet 2 to 5,
depending on the range of the address in use. A two-octet address field comprising the
EA=ADDRESS FIELD EXTENSION BITS and the C/R=COMMAND/RESPONSE BIT.
DLCI-Data Link Connection Identifier Bits. The DLCI serves to identify the virtual connection so
that the receiving end knows which information connection a frame belongs to. Note that this DLCI
has only local significance. A single physical channel can multiplex several different virtual
connections.
 FECN, BECN, DE bits. These bits report congestion:
 FECN=Forward Explicit Congestion Notification bit
 BECN=Backward Explicit Congestion Notification bit
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

DE=Discard Eligibility bit
Figure :- LAPF CORE - formats
Information Field. A system parameter defines the maximum number of data bytes that a host
can pack into a frame. Hosts may negotiate the actual maximum frame length at call set-up time. The
standard specifies the maximum information field size (supportable by any network) as at least 262
octets. Since end-to-end protocols typically operate on the basis of larger information units, frame
relay recommends that the network support the maximum value of at least 1600 octets in order to
avoid the need for segmentation and reassembling by end-users.
Frame Check Sequence (FCS) Field. Since one cannot completely ignore the bit error-rate of
the medium, each switching node needs to implement error detection to avoid wasting bandwidth
due to the transmission of erred frames. The error detection mechanism used in frame relay uses the
cyclic redundancy check (CRC) as its basis.
1.3 FRAME RELAY CALL CONTROL
Similar to X.25, Frame relay also supports multiple connections over a single link known as ‘datalink connections’, each as unique DLCI field.
Data Transfer involves the following stages;
o Establish a logical connection & assign a unique DLCI to it.
o Exchange information in data frames.
o Release the logical connection.
It involves 4 messages;
 SETUP  may request a logical connection by sending SETUP message
 CONNECT  the other side must reply with a CONNECT message, if it accepted
 RELEASE  may request to clear or leave a logical connection by sending
RELEASE message
 RELEASE COMPLETE  other side respond with RELEASE COMPLETE message
if it accepts the RELEASE message.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
1.4 FRAME RELAY VERSUS X.25
The design of X.25 aimed to provide error-free delivery over links with high error-rates. Frame
relay takes advantage of the new links with lower error-rates, enabling it to eliminate many of the
services provided by X.25. The elimination of functions and fields, combined with digital links,
enables frame relay to operate at speeds 20 times greater than X.25.
X.25 specifies processing at layers 1, 2 and 3 of the OSI model, while frame relay operates at
layers 1 and 2 only. This means that frame relay has significantly less processing to do at each node,
which improves throughput by an order of magnitude.
X.25 prepares and sends packets, while frame relay prepares and sends frames. X.25
packets contain several fields used for error and flow control, none of which frame relay needs. The
frames in frame relay contain an expanded address field that enables frame relay nodes to direct
frames to their destinations with minimal processing .
X.25 has a fixed bandwidth available. It uses or wastes portions of its bandwidth as the load
dictates. Frame relay can dynamically allocate bandwidth during call setup negotiation at both the
physical and logical channel level.
2. ASYNCHRONOUS TRANSFER MODE (ATM)
Asynchronous Transfer Mode (ATM) is an International Telecommunication UnionTelecommunications Standards Section (ITU-T) standard for cell relay wherein information for
multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells.
2.1 INTRODUCTION
ATM networks are connection-oriented.
ATM is a cell-switching and multiplexing technology that combines the benefits of circuit
switching (guaranteed capacity and constant transmission delay) with those of packet switching
(flexibility and efficiency for intermittent traffic).
It provides scalable bandwidth from a few megabits per second (Mbps) to many gigabits per
second (Gbps). Because of its asynchronous nature, ATM is more efficient than synchronous
technologies, such as time-division multiplexing (TDM).
With TDM, each user is assigned to a time slot, and no other station can send in that time slot. If a
station has much data to send, it can send only when its time slot comes up, even if all other time
slots are empty. However, if a station has nothing to transmit when its time slot comes up, the time
slot is sent empty and is wasted. Because ATM is asynchronous, time slots are available on demand
with information identifying the source of the transmission contained in the header of each ATM cell.
ATM transfers information in fixed-size units called cells. Each cell consists of 53 octets, or
bytes. The first 5 bytes contain cell-header information, and the remaining 48 contain the payload
(user information). Small, fixed-length cells are well suited to transferring voice and video traffic
because such traffic is intolerant of delays that result from having to wait for a large data packet to
download, among other things. Figure illustrates the basic format of an ATM cell. Figure :An ATM
Cell Consists of a Header and Payload Data
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
ATM allows multiple logical connections to multiplex over a single physical interface. In the case
of ATM, the information flow on each logical connection is organised into fixed-size packets, called
cells.
ATM is a streamlined protocol with minimal error and flow control capabilities: this reduces the
overhead of processing ATM cells and reduces the number of overhead bits required with each cell,
thus enabling ATM to operate at high data rates.
The use of fixed-size cells simplifies the processing required at each ATM node, again
supporting the use of ATM at high data rates.
2.2 ATM PROTOCOL ARCHITECTURE:
The ATM architecture uses a logical model to describe the functionality that it supports. ATM
functionality corresponds to the physical layer and part of the data link layer of the OSI reference
model.
The protocol reference model shown makes reference to three separate planes:
User Plane provides for user information transfer, along with associated controls (e.g., flow
control, error control).
Control Plane performs call control and connection control functions.
Management Plane includes plane management, which performs management function related
to a system as a whole and provides coordination between all the planes, and layer management
which performs management functions relating to resource and parameters residing in its protocol
entities.
Figure:- ATM PROTOCOL ARCHITECTURE
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
The ATM reference model is composed of the following ATM layers:
• Physical layer—Analogous to the physical layer of the OSI reference model, the ATM
physical layer manages the medium-dependent transmission.
• ATM layer—Combined with the ATM adaptation layer, the ATM layer is roughly analogous
to the data link layer of the OSI reference model. The ATM layer is responsible for the simultaneous
sharing of virtual circuits over a physical link (cell multiplexing) and passing cells through the ATM
network (cell relay). To do this, it uses the VPI and VCI information in the header of each ATM cell.
• ATM adaptation layer (AAL)—Combined with the ATM layer, the AAL is roughly analogous
to the data link layer of the OSI model. The AAL is responsible for isolating higher-layer protocols
from the details of the ATM processes. The adaptation layer prepares user data for conversion into
cells and segments the data into 48-byte cell payloads.
Finally, the higher layers residing above the AAL accept user data, arrange it into packets, and
hand it to the AAL. Figure: illustrates the ATM reference model.
2.3 STRUCTURE OF AN ATM CELL
An ATM cell consists of a 5 byte header and a 48 byte payloads.
ATM defines two different cell formats: NNI (Network-network interface) and UNI (Usernetwork interface). Most ATM links use UNI cell format.
Diagram of the UNI ATM Cell
7
4 3
0
Diagram of the NNI ATM Cell
7
GFC
VPI
VPI
VPI
VCI
VPI
VCI
4 3
VCI
VCI
VCI
PT
VCI
PT
CLP
HEC
Payload
0
CLP
HEC
(48
bytes)
Payload
(48
bytes)
GFC= Generic Flow Control (4 bits) (default: 4-zero bits)
VPI = Virtual Path Identifier (8 bits UNI) or (12 bits NNI)
VCI = Virtual channel identifier (16 bits)
PT = Payload Type (3 bits)
CLP = Cell Loss Priority (1-bit)
HEC= Header Error Correction (8-bit CRC, polynomial = X8 + X2 + X + 1)
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
The PT field is used to designate various special kinds of cells for Operation and
Management (OAM) purposes, and to delineate packet boundaries in some AALs.
Several of ATM's link protocols use the HEC field to drive a CRC-Based Framing algorithm,
which allows the position of the ATM cells to be found with no overhead required beyond what is
otherwise needed for header protection. The 8-bit CRC is used to correct single-bit header errors
and detect multi-bit header errors. When multi-bit header errors are detected, the current and
subsequent cells are dropped until a cell with no header errors is found.
In a UNI cell the GFC field is reserved for a local flow control/sub multiplexing system between
users. This was intended to allow several terminals to share a single network connection, in the
same way that two ISDN phones can share a single basic rate ISDN connection. All four GFC bits
must be zero by default. The NNI cell format is almost identical to the UNI format, except that the 4bit GFC field is re-allocated to the VPI field, extending the VPI to 12 bits. Thus, a single NNI ATM
interconnection is capable of addressing almost 212 VPs of up to almost 216 VCs each (in practice
some of the VP and VC numbers are reserved).
A Virtual Channel (VC) denotes the transport of ATM cells which have the same unique identifier,
called the Virtual Channel Identifier (VCI). This identifier is encoded in the cell header. A virtual
channel represents the basic means of communication between two end-points, and is analogous to
an X.25 virtual circuit.
A Virtual Path (VP) denotes the transport of ATM cells belonging to virtual channels which share a
common identifier, called the Virtual Path Identifier (VPI), which is also encoded in the cell header. A
virtual path, in other words, is a grouping of virtual channels which connect the same end-points.
This two layer approach results in improved network performance. Once a virtual path is set up, the
addition/removal of virtual channels is straightforward.
ATM Classes of Services
ATM is connection oriented and allows the user to specify the resources required on a perconnection basis (per SVC) dynamically. There are the five classes of service defined for ATM (as
per ATM Forum UNI 4.0 specification). The QoS parameters for these service classes are
summarized in Table 1.
Service Class
Quality of Service Parameter
This class is used for emulating circuit switching. The cell rate is constant
constant bit rate with time. CBR applications are quite sensitive to cell-delay variation.
(CBR)
Examples of applications that can use CBR are telephone traffic (i.e., nx64
kbps), videoconferencing, and television.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
This class allows users to send traffic at a rate that varies with time
variable bit rate–
depending on the availability of user information. Statistical multiplexing is
non-real
time
provided to make optimum use of network resources. Multimedia e-mail is an
(VBR–NRT)
example of VBR–NRT.
variable bit rate– This class is similar to VBR–NRT but is designed for applications that are
real time (VBR– sensitive to cell-delay variation. Examples for real-time VBR are voice with
RT)
speech activity detection (SAD) and interactive compressed video.
This class of ATM services provides rate-based flow control and is aimed at
data traffic such as file transfer and e-mail. Although the standard does not
require the cell transfer delay and cell-loss ratio to be guaranteed or
available bit rate
minimized, it is desirable for switches to minimize delay and loss as much as
(ABR)
possible. Depending upon the state of congestion in the network, the source
is required to control its rate. The users are allowed to declare a minimum
cell rate, which is guaranteed to the connection by the network.
unspecified
rate (UBR)
bit
Technical
Definition
Parameter
cell
loss
ratio CLR is the percentage of cells not delivered at their destination because they
(CLR)
were lost in the network due to congestion and buffer overflow.
cell
transfer
delay (CTD)
cell
cell
implies larger buffering for delay-sensitive traffic such as voice and video.
rate The maximum cell rate at which the user will transmit. PCR is the inverse of
the minimum cell inter-arrival time.
sustained
cell This is the average rate, as measured over a long interval, in the order of the
rate (SCR)
(BT)
called the CTD. It includes propagation delays, queuing delays at various
delay CDV is a measure of the variance of the cell transfer delay. High variation
(PCR)
burst
The delay experienced by a cell between network entry and exit points is
intermediate switches, and service times at queuing points.
variation (CDV)
peak
This class is the catch-all, other class and is widely used today for TCP/IP.
tolerance
connection lifetime.
This parameter determines the maximum burst that can be sent at the peak
rate. This is the bucket-size parameter for the enforcement algorithm that is
used to control the traffic entering the network.
Benefits of ATM
The benefits of ATM are the following:
 high performance via hardware switching
 dynamic bandwidth for bursty traffic
 class-of-service support for multimedia
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING




scalability in speed and network size
common LAN/WAN architecture
opportunities for simplification via VC architecture
international standards compliance
ATM Adaptation Layers (AAL)
The use of Asynchronous Transfer Mode (ATM) technology and services creates the need for an
adaptation layer in order to support information transfer protocols, which are not based on ATM. This
adaptation layer defines how to segment and reassemble higher-layer packets into ATM cells, and
how to handle various transmission aspects in the ATM layer.
Examples of services that need adaptations are Gigabit Ethernet, IP, Frame Relay, SONET/SDH,
UMTS/Wireless, etc.
The main services provided by AAL (ATM Adaptation Layer) are:
 Segmentation and reassembly
 Handling of transmission errors
 Handling of lost and misinserted cell conditions
 Timing and flow control
The following ATM Adaptation Layer protocols (AALs) have been defined by the ITU-T. It is meant
that these AALs will meet a variety of needs. The classification is based on whether a timing
relationship must be maintained between source and destination, whether the application requires a
constant bit rate, and whether the transfer is connection oriented or connectionless.

AAL Type 1 supports constant bit rate (CBR), synchronous, connection oriented traffic.
Examples include T1 (DS1), E1, and x64 kbit/s emulation.

AAL Type 2 supports time-dependent Variable Bit Rate (VBR-RT) of connection-oriented,
synchronous traffic. Examples include Voice over ATM. AAL2 is also widely used in wireless
applications due to the capability of multiplexing voice packets from different users on a single
ATM connection.

AAL Type 3/4 supports VBR, data traffic, connection-oriented, asynchronous traffic (e.g. X.25
data) or connectionless packet data (e.g. SMDS traffic) with an additional 4-byte header in the
information payload of the cell. Examples include Frame Relay and X.25.

AAL Type 5 is similar to AAL 3/4 with a simplified information header scheme. This AAL
assumes that the data is sequential from the end user and uses the Payload Type Indicator (PTI)
bit to indicate the last cell in a transmission. Examples of services that use AAL 5 are classic IP
over ATM, Ethernet Over ATM, SMDS, and LAN Emulation (LANE). AAL 5 is a widely used ATM
adaptation layer protocol. This protocol was intended to provide a streamlined transport facility
for higher-layer protocols that are connection oriented.
AAL 5 was introduced to:
 Reduce protocol processing overhead.
 Reduce transmission overhead.
 Ensure adaptability to existing transport protocols.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
AAL1 PDU
The structure of the AAL1 PDU is given in the following illustration:
SN
SNP
CSI
SC
CRC
EPC
1 bit
3 bits
3 bits
1 bit
SARPDU
Payload
47 bytes
AAL1 PDU
SN - Sequence number
Numbers the stream of SAR PDUs of a CPCS PDU (modulo 16). The sequence number is
comprised of the CSI and the SN.
CSI - Convergence sublayer indicator
Used for residual time stamp for clocking.
SC - Sequence count
The sequence number for the entire CS PDU, which is generated by the Convergence Sub layer.
SNP- Sequence number protection
Comprised of the CRC and the EPC.
CRC
Cyclic redundancy check calculated over the SAR header.
EPC
Even parity check calculated over the CRC.
SAR PDU payload
47-byte user information field.
AAL2
AAL2 provides bandwidth-efficient transmission of low-rate, short and variable packets in delay
sensitive applications. It supports VBR and CBR. AAL2 also provides for variable payload within cells
and across cells. AAL type 2 is subdivided into the Common Part Sub layer (CPS) and the Service
Specific Convergence Sub layer (SSCS).
AAL2 CPS Packet
The CPS packet consists of a 3 octet header followed by a payload. The structure of the AAL2 CPS
packet is shown in the following illustration.
CID
LI
UUI
HEC
Information payload
8 bits
6 bits
5 bits
5 bits
1-45/64 bytes
AAL2 CPS packet
CID – Channel identification
LI - Length indicator. This is the length of the packet payload associated with each individual user.
Value is one less than the packet payload and has a default value of 45 bytes (may be set to 64
bytes).
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
UUI - User-to-user indication
Provides a link between the CPS and an appropriate SSCS that satisfies the higher layer application
HEC - Header error control.
AAL2
The structure of the AAL2 SAR PDU is given in the following illustration.
Start field
CPS-PDUpayload
OSF
SN
P
6 bits
1 bit
1 bit
AAL2 PDU
payload
PAD
0-47 bytes
AAL2 CPS PDU
OSF - Offset field
Identifies the location of the start of the next CPS packet within the CPS-PDU.
SN- Sequence number
Protects data integrity.
P- Parity
Protects the start field from errors.
SAR PDU payload
Information field of the SAR PDU.
PAD - Padding.
AAL2 SSCS Packet
The SSCS conveys narrowband calls consisting of voice, voiceband data or circuit mode data. SSCS
packets are transported as CPS packets over AAL2 connections. The CPS packet contains a SSCS
payload. There are 3 SSCS packet types.
Type 1 Unprotected; this is used by default.
Type 2 Partially protected.
Type 3 Fully protected: the entire payload is protected by a 10-bit CRC which is computed as for
OAM cells. The remaining 2 bits of the 2-octet trailer consist of the message type field.
AAL2 SSCS Type 3 Packets:
The type 3 packets are used for the following:
 Dialled digits
 Channel associated signalling bits
 Facsimile demodulated control data
 Alarms
 User state control operations.
The following illustration gives the general sturcture of AAL2 SSCS Type 3 PDUs. The format varies
and each message has its own format according to the actual message type.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Redundancy
Time stamp Message
dependant
information
2
14
Message
type
16
6
CRC-10
10 bits
AAL2 SSCS Type 3 PDU
Redundancy
Packets are sent 3 times to ensure error correction. The value in this field signifies the transmission
number.
Time stamp
Counters packet delay variation and allows a receiver to accurately reproduce the relative timing of
successive events separated by a short interval.
Message dependant information
Packet content that varies, depending on the message type.
Message type
The message type code.
CRC-10
The 10-bit CRC.
AAL3/4
AAL3/4 consists of message and streaming modes. It provides for point-to-point and point-tomultipoint (ATM layer) connections. The Convergence Sublayer (CS) of the ATM Adaptation Layer
(AAL) is divided into two parts: service specific (SSCS ) and common part (CPCS ). This is illustrated
in the following diagram:
AAL3/4 packets are used to carry computer data, mainly SMDS traffic.
AAL3/4 CPCS PDU
The functions of the AAL3/4 CPCS include connectionless network layer (Class D), meaning no need
for an SSCS; and frame relaying telecommunication service in Class C. The CPCS PDU is
composed of the following fields:
Header
Info
Trailer
CPI
Btag
Basize
CPCS SDU
Pad
0Etag
Length
1
1
2
0-65535
0-3
11
2 bytes
AAL3/4 CPCS PDU
CPI
Message type. Set to zero when the BAsize and Length fields are encoded in bytes.
Btag
Beginning tag. This is an identifier for the packet. It is repeated as the Etag.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
BAsize
Buffer allocation size. Size (in bytes) that the receiver has to allocate to capture all the data.
CPCS SDU
Variable information field up to 65535 bytes.
PAD
Padding field which is used to achieve 32-bit alignment of the length of the packet.
0
All-zero.
Etag
End tag. Must be the same as Btag.
Length
Must be the same as BASize.
AAL3/4 SAR PDU
The structure of the AAL3/4 SAR PDU is illustrated below:
ST
SN
2
4
MID
Information
LI
CRC
10
352
6
10 bits
44 bytes
2-byte trailer
2-byte header
48 bytes
AAL3/4 SAR PDU
ST - Segment type
SN - Sequence number
Numbers the stream of SAR PDUs of a CPCS PDU (modulo 16).
MID - Multiplexing identification
This is used for multiplexing several AAL3/4 connections over one ATM link.
Information
This field has a fixed length of 44 bytes and contains parts of CPCS PDU.
LI - Length indication
Contains the length of the SAR SDU in bytes, as follows:
CRC
Cyclic redundancy check.
Functions of AAL3/4 SAR include identification of SAR SDUs; error indication and handling; SAR
SDU sequence continuity; multiplexing and demultiplexing.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
AAL5 The type 5 adaptation layer is a simplified version of AAL3/4. It also consists of message and
streaming modes, with the CS divided into the service specific and common part. AAL5 provides
point-to-point and point-to-multipoint (ATM layer) connections.
AAL5 is used to carry computer data such as TCP/IP. It is the most popular AAL and is sometimes
referred to as SEAL (simple and easy adaptation layer).
AAL5 CPCS PDU
The AAL5 CPCS PDU is composed of the following fields:
Info
Trailer
CPCS payload
Pad
UU CPI Length
CRC
0-65535
0-47
1
4 bytes
1
2
AAL5 CPCS PDU
CPCS
The actual information that is sent by the user. Note that the information comes before any length
indication (as opposed to AAL3/4 where the amount of memory required is known in advance).
Pad
Padding bytes to make the entire packet (including control and CRC) fit into a 48-byte boundary.
UU
CPCS user-to-user indication to transfer one byte of user information.
CPI
Common part indicator is a filling byte (of value 0). This field is to be used in the future for layer
management message indication.
Length
Length of the user information without the Pad.
CRC
CRC-32. Used to allow identification of corrupted transmission.
AAL5 SAR PDU
The structure of the AAL5 CS PDU is as follows:
Information
PAD
UU
CPI
Length
CRC-32
1-48
4 bytes
0-47
1
1
2
8-byte trailer
AAL5 SAR PDU
High-Speed LANs
Emergence of High-Speed LANs
 2 Significant trends
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
o Computing power of PCs continues to grow rapidly
o Network computing
 Examples of requirements
o Centralized server farms
o Power workgroups
o High-speed local backbone
Classical Ethernet
 Bus topology LAN
 10 Mbps
 CSMA/CD medium access control protocol
2 problems:
 A transmission from any station can be received by all stations
 How to regulate transmission
 Solution to First Problem
o Data transmitted in blocks called frames:
o User data
o Frame header containing unique address of destination station
CSMA/CD
Carrier Sense Multiple Access/ Carrier Detection
 If the medium is idle, transmit.
 If the medium is busy, continue to listen until the channel is idle, then transmit immediately.
 If a collision is detected during transmission, immediately cease transmitting.
 After a collision, wait a random amount of time, then attempt to transmit again (repeat from
step 1).
Medium Options at 10Mbps
 <data rate> <signaling method> <max length>
 10Base5
o 10 Mbps
o 50-ohm coaxial cable bus
o Maximum segment length 500 meters
 10Base-T
o Twisted pair, maximum length 100 meters
o Star topology (hub or multipoint repeater at central point)
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Hubs and Switches
 Hub
o Transmission from a station received by central hub and retransmitted on all outgoing
lines
o Only one transmission at a time

Layer 2 Switch
o Incoming frame switched to one outgoing line
o Many transmissions at same time
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Bridge
 Frame handling done in software
 Analyze and forward one frame at a time
 Store-and-forward
Layer 2 Switch
 Frame handling done in hardware
 Multiple data paths and can handle multiple frames at a time
 Can do cut-through
Layer 2 Switches
 Flat address space
 Broadcast storm
 Only one path between any 2 devices


Solution 1: subnetworks connected by routers
Solution 2: layer 3 switching, packet-forwarding logic in hardware
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Benefits of 10 Gbps Ethernet over ATM
 No expensive, bandwidth consuming conversion between Ethernet packets and ATM cells
 Network is Ethernet, end to end
 IP plus Ethernet offers QoS and traffic policing capabilities approach that of ATM
 Wide variety of standard optical interfaces for 10 Gbps Ethernet
Fibre Channel
 2 methods of communication with processor:
 I/O channel
 Network communications
Fibre channel combines both
 Simplicity and speed of channel communications
 Flexibility and interconnectivity of network communications
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
I/O channel
 Hardware based, high-speed, short distance
 Direct point-to-point or multipoint communications link
 Data type qualifiers for routing payload
 Link-level constructs for individual I/O operations
 Protocol specific specifications to support e.g. SCSI
Fibre Channel Network-Oriented Facilities
 Full multiplexing between multiple destinations
 Peer-to-peer connectivity between any pair of ports
 Internetworking with other connection technologies
Fibre Channel Requirements
 Full duplex links with 2 fibres/link
 100 Mbps – 800 Mbps
 Distances up to 10 km
 Small connectors
 high-capacity
 Greater connectivity than existing multidrop channels
 Broad availability
 Support for multiple cost/performance levels
 Support for multiple existing interface command sets
Fibre Channel Protocol Architecture
 FC-0 Physical Media
 FC-1 Transmission Protocol
 FC-2 Framing Protocol
 FC-3 Common Services
 FC-4 Mapping
Wireless LAN Requirements
 Throughput
 Number of nodes
 Connection to backbone
 Service area
 Battery power consumption
 Transmission robustness and security
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING




Collocated network operation
License-free operation
Handoff/roaming
Dynamic configuration
IEEE 802.11 Services
 Association
 Reassociation
 Disassociation
 Authentication
 Privacy
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
UNIT II
CONGESTION AND TRAFFIC MANAGEMENT
Queuing Analysis - Queuing Models - Single Server Queues - Effects of Congestion - Congestion
Control - Traffic Management - Congestion Control in Packet Switching Networks - Frame Relay
Congestion Control.
QUEING ANALYSIS
In queuing theory, a queuing model is used to approximate a real queuing situation or system, so
the queuing behaviour can be analysed mathematically. Queuing models allow a number of useful
steady state performance measures to be determined, including:
 the average number in the queue, or the system
 the average time spent in the queue, or the system
 the statistical distribution of those numbers or times
 the probability the queue is full, or empty
 the probability of finding the system in a particular state
These performance measures are important as issues or problems caused by queuing situations are
often related to customer dissatisfaction with service or may be the root cause of economic losses in
a business. Analysis of the relevant queuing models allows the cause of queuing issues to be
identified and the impact of any changes that might be wanted to be assessed.
NOTATION
 Queuing models can be represented using Kendall's notation:
A/B/S/K/N/Disc
Where :
o
o
o
o
o
o
A is the inter arrival time distribution
B is the service time distribution
S is the number of servers
K is the system capacity
N is the calling population
Disc is the service discipline assumed
Some standard notation for distributions (A or B) are:
o M for a Markovian (exponential) distribution
o Eκ for an Erlang distribution with κ phases
o D for Deterministic (constant)
o G for General distribution
o PH for a Phase-type distribution
MODELS
CONSTRUCTION AND ANALYSIS
Queuing models are generally constructed to represent the steady state of a queuing system, that
is, the typical, long run or average state of the system. As a consequence, these are stochastic
models that represent the probability that a queuing system will be found in a particular
configuration or state.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
A general procedure for constructing and analyzing such queuing models is:
1. Identify the parameters of the system, such as the arrival rate, service time, Queue
capacity, and perhaps draw a diagram of the system.
2. Identify the system states. (A state will generally represent the integer number of
customers, people, jobs, calls, messages, etc. in the system and may or may not be
limited.)
3. Draw a state transition diagram that represents the possible system states and identify the
rates to enter and leave each state. This diagram is a representation of a Markov chain.
4. Because the state transition diagram represents the steady state situation between state
there is a balanced flow between states so the probabilities of being in adjacent states can
be related mathematically in terms of the arrival and service rates and state probabilities.
5. Express all the state probabilities in terms of the empty state probability, using the interstate transition relationships.
6. Determine the empty state probability by using the fact that all state probabilities always
sum to 1.
Whereas specific problems that have small finite state models are often able to be analyzed
numerically, analysis of more general models, using calculus, yields useful formulae that can be
applied to whole classes of problems.
Single-Server Queue
Single-server queues are, perhaps, the most commonly encountered queuing situation in real life.
One encounters a queue with a single server in many situations, including business (e.g. sales
clerk), industry (e.g. a production line), transport (e.g. a bus, a taxi rank, an intersection),
telecommunications (e.g. Telephone line), computing (e.g. processor sharing). Even where there are
multiple servers handling the situation it is possible to consider each server individually as part of the
larger system, in many cases. (E.g. A supermarket checkout has several single server queues that
the customer can select from.) Consequently, being able to model and analyse a single server
queue's behaviour is a particularly useful thing to do.
Poisson Arrivals and Service
M/M/1/∞/∞ represents a single server that has unlimited queue capacity and infinite calling
population, both arrivals and service are Poisson (or random) processes, meaning the statistical
distribution of both the inter-arrival times and the service times follow the exponential distribution.
Because of the mathematical nature of the exponential distribution, a number of quite simple
relationships are able to be derived for several performance measures based on knowing the arrival
rate and service rate.
This is fortunate because, an M/M/1 queuing model can be used to approximate many queuing
situations.
Poisson Arrivals and General Service
M/G/1/∞/∞ represents a single server that has unlimited queue capacity and infinite calling
population, while the arrival is still Poisson process, meaning the statistical distribution of the interarrival times still follow the exponential distribution, the distribution of the service time does not. The
distribution of the service time may follow any general statistical distribution, not just exponential.
Relationships are still able to be derived for a (limited) number of performance measures if one
knows the arrival rate and the mean and variance of the service rate. However the derivations a
generally more complex.
A number of special cases of M/G/1 provide specific solutions that give broad insights into the best
model to choose for specific queuing situations because they permit the comparison of those
solutions to the performance of an M/M/1 model.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Multiple-Servers Queue
Multiple (identical)-servers queue situations are frequently encountered in telecommunications or a
customer service environment. When modelling these situations care is needed to ensure that it is a
multiple servers queue, not a network of single server queues, because results may differ depending
on how the queuing model behaves.
One observational insight provided by comparing queuing models is that a single queue with multiple
servers performs better than each server having their own queue and that a single large pool of
servers performs better than two or more smaller pools, even though there are the same total
number of servers in the system.
One simple example to prove the above fact is as follows: Consider a system having 8 input lines,
single queue and 8 servers.The output line has a capacity of 64 kbit/s. Considering the arrival rate at
each input as 2 packets/s. So, the total arrival rate is 16 packets/s. With an average of 2000 bits per
packet, the service rate is 64 kbit/s/2000b = 32 packets/s. Hence, the average response time of the
system is 1/(μ-λ) = 1/(32-16) = 0.0667 sec. Now, consider a second system with 8 queues, one for
each server. Each of the 8 output lines has a capacity of 8 kbit/s. The calculation yields the response
time as 1/(μ-λ) = 1/(4-2) = 0.5 sec. And the average waiting time in the queue in the first case is ρ/(1ρ)μ = 0.25, while in the second case is 0.03125.
Infinitely Many Servers
While never exactly encountered in reality, an infinite-servers (e.g. M/M/∞) model is a convenient
theoretical model for situations that involve storage or delay, such as parking lots, warehouses and
even atomic transitions. In these models there is no queue, as such, instead each arriving customer
receives service. When viewed from the outside, the model appears to delay or store each customer
for some time.
Queuing System Classification
With Little's Theorem, we have developed some basic understanding of a queuing system. To further
our understanding we will have to dig deeper into characteristics of a queuing system that impact its
performance. For example, queuing requirements of a restaurant will depend upon factors like:
 How do customers arrive in the restaurant? Are customer arrivals more during lunch and
dinner time (a regular restaurant)? Or is the customer traffic more uniformly distributed (a
cafe)?
 How much time do customers spend in the restaurant? Do customers typically leave the
restaurant in a fixed amount of time? Does the customer service time vary with the type of
customer?
 How many tables does the restaurant have for servicing customers?
The above three points correspond to the most important characteristics of a queuing system. They
are explained below:
The probability density distribution that determines the customer
Arrival Process
arrivals in the system.
In a messaging system, this refers to the message arrival probability
distribution.
The probability density distribution that determines the customer
service times in the system.
Service Process
In a messaging system, this refers to the message transmission time
distribution. Since message transmission is directly proportional to
the length of the message, this parameter indirectly refers to the
message length distribution.
Number of servers available to service the customers.
Number of Servers
In a messaging system, this refers to the number of links between
the source and destination nodes.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Based on the above characteristics, queueing systems can be classified by the following convention:
A/S/n
Where
 A is the arrival process
 S is the service process and n is the number of servers
A and S can be any of the following:
M (Markov)
Exponential probability density
D (Deterministic)
All customers have the same value
G (General)
Any arbitrary probability distribution
Examples of queuing systems that can be defined with this convention are:

M/M/1: This is the simplest queuing system to analyze. Here the arrival and service time are
negative exponentially distributed (Poisson process). The system consists of only one server.
This queuing system can be applied to a wide variety of problems as any system with a very
large number of independent customers can be approximated as a Poisson process. Using a
Poisson process for service time however is not applicable in many applications and is only a
crude approximation. Refer to M/M/1 Queuing System for details.

M/D/n: Here the arrival process is Poisson and the service time distribution is deterministic.
The system has n servers. (e.g. a ticket booking counter with n cashiers.) Here the service
time can be assumed to be same for all customers)

G/G/n: This is the most general queuing system where the arrival and service time processes
are both arbitrary. The system has n servers. No analytical solution is known for this queuing
system.
Markovian Arrival Processes
In queuing theory, Markovian arrival processes are used to model the arrival customers to queue.
Some of the most common include the Poisson process, Markovian arrival process and the batch
Markovian arrival process.
Markovian arrival processes have two processes. A continuous-time Markov process j(t), a Markov
process which is generated by a generator or rate matrix, Q. The other process is a counting process
N(t), which has state space
(where
is the set of all natural numbers). N(t)
increases every time there is a transition in j(t) which marked.
Poisson Process
The Poisson arrival process or Poisson process counts the number of arrivals, each of which has a
exponentially distributed time between arrival. In the most general case this can be represented by
the rate matrix,
Markov Arrival Process
The Markov arrival process (MAP) is a generalisation of the Poisson process by having nonexponential distribution sojourn between arrivals. The homogeneous case has rate matrix,
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Little's law
In queuing theory, Little's result, theorem, lemma, or law says:
The average number of customers in a stable system (over some time interval), N, is equal to their
average arrival rate, λ, multiplied by their average time in the system, T, or:
Although it looks intuitively reasonable, it's a quite remarkable result, as it implies that this behavior is
entirely independent of any of the detailed probability distributions involved, and hence requires no
assumptions about the schedule according to which customers arrive or are serviced, or whether
they are served in the order in which they arrive.
It is also a comparatively recent result - it was first proved by John Little, an Institute Professor and
the Chair of Management Science at the MIT Sloan School of Management, in 1961.
Handily his result applies to any system, and particularly, it applies to systems within systems. So in
a bank, the queue might be one subsystem, and each of the tellers another subsystem, and Little's
result could be applied to each one, as well as the whole thing. The only requirement is that the
system is stable -- it can't be in some transition state such as just starting up or just shutting down.
Mathematical Formalization of Little's Theorem
Let α(t) be to some system in the interval [0, t]. Let β(t) be the number of departures from the same
system in the interval [0, t]. Both α(t) and β(t) are integer valued increasing functions by their
definition. Let Tt be the mean time spent in the system (during the interval [0, t]) for all the customers
who were in the system during the interval [0, t]. Let Nt be the mean number of customers in the
system over the duration of the interval [0, t].
If the following limits exist,
and, further, if λ = δ then Little's theorem holds, the limit
exists and is given by Little's theorem,
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Ideal Performance
Effects of Congestion
‘
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Congestion-Control Mechanisms
 Backpressure
o Request from destination to source to reduce rate
o Useful only on a logical connection basis
o Requires hop-by-hop flow control mechanism
 Policing
o Measuring and restricting packets as they enter the network
 Choke packet
o Specific message back to source
o E.g., ICMP Source Quench
 Implicit congestion signalling
o Source detects congestion from transmission delays and lost packets and reduces flow
Explicit congestion signalling
Frame Relay reduces network overhead by implementing simple congestion-notification mechanisms
rather than explicit, per-virtual-circuit flow control. Frame Relay typically is implemented on reliable
network media, so data integrity is not sacrificed because flow control can be left to higher-layer
protocols. Frame Relay implements two congestion-notification mechanisms:
•
Forward-explicit congestion notification (FECN)
•
Backward-explicit congestion notification (BECN)
FECN and BECN each is controlled by a single bit contained in the Frame Relay frame header. The
Frame Relay frame header also contains a Discard Eligibility (DE) bit, which is used to identify less
important traffic that can be dropped during periods of congestion.
The FECN bit is part of the Address field in the Frame Relay frame header. The FECN mechanism is
initiated when a DTE device sends Frame Relay frames into the network. If the network is
congested, DCE devices (switches) set the value of the frames' FECN bit to 1. When the frames
reach the destination DTE device, the Address field (with the FECN bit set) indicates that the frame
experienced congestion in the path from source to destination. The DTE device can relay this
information to a higher-layer protocol for processing. Depending on the implementation, flow control
may be initiated, or the indication may be ignored.
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
The BECN bit is part of the Address field in the Frame Relay frame header. DCE devices set the
value of the BECN bit to 1 in frames traveling in the opposite direction of frames with their FECN bit
set. This informs the receiving DTE device that a particular path through the network is congested.
The DTE device then can relay this information to a higher-layer protocol for processing. Depending
on the implementation, flow-control may be initiated, or the indication may be ignored.
Frame Relay Discard Eligibility
The Discard Eligibility (DE) bit is used to indicate that a frame has lower importance than other
frames. The DE bit is part of the Address field in the Frame Relay frame header.
DTE devices can set the value of the DE bit of a frame to 1 to indicate that the frame has lower
importance than other frames. When the network becomes congested, DCE devices will discard
frames with the DE bit set before discarding those that do not. This reduces the likelihood of critical
data being dropped by Frame Relay DCE devices during periods of congestion.
Frame Relay Error Checking
Frame Relay uses a common error-checking mechanism known as the cyclic redundancy check
(CRC). The CRC compares two calculated values to determine whether errors occurred during the
transmission from source to destination. Frame Relay reduces network overhead by implementing
error checking rather than error correction. Frame Relay typically is implemented on reliable network
media, so data integrity is not sacrificed because error correction can be left to higher-layer protocols
running on top of Frame Relay.
Traffic Management in Congested Network – Some Considerations
 Fairness
o Various flows should “suffer” equally
o Last-in-first-discarded may not be fair
 Quality of Service (QoS)
o Flows treated differently, based on need
o Voice, video: delay sensitive, loss insensitive
o File transfer, mail: delay insensitive, loss sensitive
o Interactive computing: delay and loss sensitive
 Reservations
o Policing: excess traffic discarded or handled on best-effort basis
Frame Relay Congestion Control
 Minimize frame discard
 Maintain QoS (per-connection bandwidth)
 Minimize monopolization of network
 Simple to implement, little overhead
 Minimal additional network traffic
 Resources distributed fairly
 Limit spread of congestion
 Operate effectively regardless of flow
 Have minimum impact other systems in network
 Minimize variance in QoS
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Congestion Avoidance with Explicit Signaling
Two general strategies considered:
Hypothesis 1: Congestion always occurs slowly, almost always at egress nodes
 forward explicit congestion avoidance
Hypothesis 2: Congestion grows very quickly in internal nodes and requires quick action
 backward explicit congestion avoidance
Explicit Signaling Response
 Network Response
o each frame handler monitors its queuing behavior and takes action
o use FECN/BECN bits
o some/all connections notified of congestion
 User (end-system) Response
o Receipt of BECN/FECN bits in frame
o BECN at sender: reduce transmission rate
o FECN at receiver: notify peer (via LAPF or higher layer) to restrict flow
Frame Relay Traffic Rate Management Parameters
 Committed Information Rate (CIR)
o Average data rate in bits/second that the network agrees to support for a connection
 Data Rate of User Access Channel (Access Rate)
o Fixed rate link between user and network (for network access)
 Committed Burst Size (Bc)
o Maximum data over an interval agreed to by network
 Excess Burst Size (Be)
o Maximum data, above Bc, over an interval that network will attempt to transfer
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
Relationship of Congestion Parameters
CS 2060 – High Speed Networks
NOTES
J.J. COLLEGE OF ENGINEERING AND TECHNOLOGY
Ammapettai, Tiruchirappalli – 620 009.
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
CS 2060 – High Speed Networks
NOTES