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Cramsession: Cisco WAN Switching Certification
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© 2001 All Rights Reserved – BrainBuzz.com
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Contents:
Contents: 1
ATM Basics 3
ATM Model 3
ATM Headers 3
ATM Addressing 5
Cisco ATM Addressing 5
ATM Adaptation Layer 5
Quality of Service 6
Service Categories 6
Frame Relay Basics 7
Voice Basics 8
Analog to Digital Conversion 9
Optimization 9
Signaling 10
General Installation 12
Tools Required 12
Installation Outline 12
Command Line Interface (CLI) 13
BPX 8600 Series 17
Card Types 17
Installing BPX Cards 17
Initial Configuration 20
IGX 8400 Series 22
Card Installation 22
Initial Configuration 26
MGX Series Installation 29
MGX 8220 29
Card Installation 30
Initial Configuration 32
MGX 8850 32
Card Installation 33
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MGX 8850 Interface Cards 35
Initial Configuration 38
Cisco WAN View 38
Cisco Wan Manager (CWM) 40
Components 40
Additional Features 41
Software and Firmware Upgrades 42
Downloading from CWM workstation 43
Download from a Switch 43
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ATM Basics
ATM is a packet-switched technology based on a 53-byte packet called a cell. Each
cell is divided into a 5-byte header and a 48-byte payload. The short, fixed length
cell reduces delay and jitter, allowing time sensitive information such as voice and
video to be transported along with data. There are various transmission media and
rates available with bandwidth measured in megabits to gigabits.
ATM Model
ATM is based on Broadband Integrated Services Digital Network, an extension of
ISDN. Similar to the OSI model, B-ISDN uses a seven-layer model. ATM redefines
the lower 3 layers into the Physical Layer, the ATM Layer and the ATM Adaptation
Layer.
• The Physical Medium sub-layer (PMD) interfaces with the physical medium.
• The Transmission Control sub-layer handles cell extraction from the data
stream and error checking.
ATM Headers
The ATM Cell has a 5-byte header, with the remaining 48-bytes left for payload
(data).
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There are two standard headers. Cisco added an addition header type to allow for
advanced ATM features.
• User-to-Network Interface (UNI) header-specifies interface between a user
device and a network. Note: A user device is not just a computer interface.
It can be a router or switch as well.
• Network-to-Network Interface (NNI) header-specifies interface between two
networks. Usually a private ATM network and a public ATM network.
• STI header-used between to Cisco ATM switching nodes to allow advanced
network features.
• Flow Control (4-bits)-a UNI field for controlling access and flow control.
Usually all zeros, as there is no defined standards.
• Virtual Path Indicator (VPI)-identifies the path to be taken by the ATM cell.
• Virtual Circuit Indicator (VCI)-indicates the circuit number on the path.
• Payload Type Indicator (PTI, 3-bits)-the type of data being carried in the
payload. High order bit is 0 for user data and 1 for connection management
information, second bit indicates if there was congestion, and the third bit
show if user data is from customer premises equipment.
• Payload Class (4-bits)-STI field indicating classes of service and BPX switch
queues.
• Cell Loss Priority bit (CL)-indicates the cell may be discarded if congestion is
encountered.
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ATM Addressing
• VCI identifies the circuit or connection.
• VPI identifies the virtual path.
• The path can be seen as a trunk that carries multiple circuits between
switches.
• VCI is 16-bits allowing 65, 535 circuit numbers. For the STI header VCI is 8-
bits for 256 circuits.
• VPI is 8-bits for the UNI header, 12-bits for the NNI header (4096 paths), and
10-bits for the STI header (1024 paths).
Cisco ATM Addressing
Three modes available depending on the hardware being used.
Addressing Node Header Type VPI/VCI Derivation Where Used
BAM-BPX switch
Addressing Mode
STI
Node derives
VPI/VCI
IPX switch to BPX switch, or
between IPX nodes
CAM-Cloud
Addressing Mode
UNI
User defined VPI
Node derived VCI
Between IPX or IGX nodes
and on networks switched on
VPI only
SAM-Simple
Addressing Node
UNI
User defined
VPI/VCI
Between IPX or IGX nodes
and on networks where
routing is user programmed
ATM Adaptation Layer
• ATM Adaptation Level (AAL)-used to convert data from various sources and
convert it to 48-byte segments that fit the payload of ATM cells.
• Four classifications of source traffic are outlined.
Traffic Class Class A Class B Class C Class D
Adaptation Layer
(AAL)
AAL-1 AAL-2 AAL-3/4 AAL-5 AAL-3/4
Connection Mode
Connection Connection Connection Connectionless
End-to-End Timing Yes Yes No No
Bit Rate Constant Variable Variable Variable
Examples
Uncompressed
iCttbit
Compressed Voice
dVid
Frame-relay, SNA,
TCP
/IP
il
SMDS
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voice, Constant bit-
rate video
and Video TCP/IP, e-mail
• Consists of Convergence sub-layer (CS) and Segmentation and Reassembly
sub-layer (SAR).
• CS receives data from the applications and sends it to the SAR to be
segmented into 48-byte blocks.
Quality of Service
These are some of the most important QoS parameters:
• Peak Cell Rate (PCR)-maximum rate a sender can send cells.
• Sustained Cell Rate (SCR)-required cell rate averaged over a long interval.
• Minimum Cell Rate (MCR)-minimum acceptable rate of cells per second.
• Cell Loss Ratio (CLR)-the fraction of cells not delivered or delivered late.
• Cell Transfer Delay (CTD)-time from source to destination (transmit time).
• Cell Error Ratio (CER)-fraction of cells delivered with incorrect bits.
• Cell Delay Variation (CDV or Jitter)-how regularly cells are delivered. Cells
from one conversation on a multiplexed connection may be delayed while
cells from another conversation are delivered.
• Cell Delay Variation Tolerance (CDVT)-amount of variation in cell
transmission times. Specified separately for PCR and SCR.
Service Categories
The ATM Forum specifies four service categories:
• Constant Bit Rate (CBR)-entire connection, from source to destination,
including intermediary switches, provides a set amount of bandwidth at all
times. Expensive because bandwidth is reserved even if it is not used.
• Variable Bit Rate (VBR)- guarantees an average bit rate over time, but allows
a higher peak bit rate, with no cells lost, for a certain amount of time each
minute. VBR is broken into two subclasses real time (rt) and non-real time
(nrt).
o rt-VBR is used for connections that require end-to-end timing, such as
voice or video connections using compression or noise reduction.
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o nrt-VBR can be used when timing relationships are not required, but
QoS is still needed.
• Available Bit Rate (ABR)-bit rate varies according to network conditions up to
a stated maximum. Source adjusts transmission rate due to network
information received from the network.
• Unspecified Bit Rate (UBR)-no set bit rate guarantee. Allows a transmission
rate up to a certain maximum, with no guarantee of cell loss or delivery.
Frame Relay Basics
Frame relay:
• Defines a connection between user equipment and a WAN, not the interface
or protocols of the WAN itself. Usually describes a LAN-to-LAN connection.
• A standard optimized for the transport of protocol-oriented data.
• Defines network paths using statistical multiplexing (creates virtual circuits).
• Does not allocate bandwidth until data needs to be transmitted.
• Combines packet switching and port sharing with time division multiplexing
circuit switching to allow multiple point-to-point permanent virtual circuits
over a single physical interface.
• Operates only on the Data Link and Physical layers of the OSI model. Routing
is general handled by the Network layer protocol.
Components of Frame Relay
• Committed Information Rate (CIR)-rate of data transfer under normal
operations. Generally the contracted rate from the public service provider.
CIR should never be set higher than the speed of the slowest physical
connection on a VC. CIR of 0=best effort.
• User-Network Interface (UNI)-describes a connection between user
equipment and a frame relay network. Usually, a router (DTE) and the
service provider.
• Network-Network Interface-describes connection between frame relay
networks.
• Local Management Interface (LMI)-monitors the status of DLCIs by
periodically polling the network. Can be used to exchange status information
between frame devices and the network. Also supports multicasting, global
addressing and flow control. Cisco switches support LMI.
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• Bandwidth on Demand-capacity is provided as a PVC requires it up to the
maximum CIR.
• Flag-First and last byte of a frame, indicating the beginning and the end.
There may be only one flag between frames with the end flag of one frame
used as the start flag of the next.
• Data Link Connection Identifier (DLCI)-10-bit routing address of the PVC at a
particular UNI or NNI. Some DLCIs are reserve for signaling, management
and future use so only 16 to 1007 are used to address virtual circuits.
• Command/Response (C/R)-not used. Always set to 0.
• Extended Address (EA)-allows the header to be lengthened to 3 or 4 bytes
allowing a DLCI longer than 10-bits (more VC addresses).
• Forward Explicit Congestion Notification (FECN)-set to 1 by the frame network
when congestion is occurring on the packet forwarding direction of the frame.
• Backward Explicit Congestion Notification (BECN)- set to 1 by the frame
network when congestion is occurring on the reversed packet forwarding
direction of the frame.
• Discard Eligibility (DE)-set by the end node to indicate frames to be discard if
congestion occurs.
• Data-also called the information field. May be as large as 4,520 bytes, but is
more efficient with a size of less than 4k.
• Frame Check Sequence (FCS)-standard cyclic redundancy check that detects
bit errors in the frame.
Voice Basics
Human voice can achieve a frequency of up to 4000 Hz (usually between 300 to
3000 Hz).
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Analog to Digital Conversion
• The coder-decoder (CODEC) converts analog voice signals to digital signals
using pulse code modulation (PCM).
• Multiple digital voice signals can be combined into a single channel using a
multiplexer (MUX). The process is called Time Division Multiplexing (TDM).
• A T1 connection can contain 24 channels or timeslots (called DS0s) of 64
kbps each.
• An E1 or J1 connection has 30 channels with two additional timeslots for
framing and signaling.
Sampling
• General rule is that sample rate should be twice the frequency of the signal to
be sampled (example: the human voice is capable of 4000 Hz so a sample
rate of 8000 samples per second would be required).
• Each sample is converted into a 8 bit word (8 bits per sample x 8000 samples
per sec = 64kbps).
Companding
• Part of the PCM process that determines the digital bits used to represent the
voice signals (whether the value of a sample is a digital one or zero).
• 2 companding laws:
o M-law (µ-law or mu-law): logarithmic method used in North America
o A-law: linear at lower levels and logarithmic at higher levels. Used in
Europe, Asia, Australia and South America.
• Different companding methods are not compatible (international voice traffic
requires conversion from one companding method to another).
Optimization
Adaptive Differential Pulse Code Modulation (ADPCM) Voice
Compression
• Uses fewer bits than PCM sampling because only the difference between
samples not the actual value of the sample amplitude is used.
• Defined in ITU-T G.726 recommendation.
• The following rates are available:
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o 40 kbps using 5-bit samples
o 32 kbps using 4-bit samples
o 24 kbps using 3-bit samples
o 16 kbps using 2-bit samples
• Does not use A-law or M-law coding.
• Not reliable for data or fax traffic above 4800 kbps.
Code Excited Linear Prediction (CELP) Compression
• Better than ADPCM at the same or higher data rate.
• Uses know characteristics of human speech to provide compression.
• Based on ITU-T G.729 standard.
• 8, 16, 24 and 32 kbps data rates are possible.
Silence Suppression
• Reduces bandwidth by stopping transmission during silent periods in the voice
signal.
• Dependant on language spoken, silence suppression can provide 60 percent
bandwidth reduction.
• Algorithm analyzes the signal to determine if a signal is voice or background
noise (based on known characteristics of human speech).
Signaling
Signaling occurs between a subscriber and a switch or a switch and a switch.
Signaling is the process of sending status and control information between network
elements. In voice communications, signaling is generally used to initiate a call or
connection.
Subscriber to switch signaling is used from handset to PBX and includes on-hook,
off-hook detection and dialing.
Switch to switch (or interswitch) signaling is used between the local exchange carrier
(LEC) and interexchange carrier (IXC) or between PBX and PBX (or switch).
Interswitch signaling is generally digital.
Two types of interswitch signaling:
[...]... TM Cramsession: Cisco WAN Switching Certification Single to Dual Height Slot Conversions • Begin at the left and move to the right Starting points can be slots 1 and 2 (with 17 and 18), or 9 and 10 SRM slots 15 and 16 can be converted out of sequence • After conversion the slot takes the number of the top single height slot © 2001 All Rights Reserved – BrainBuzz.com 34 TM Cramsession: Cisco WAN Switching. .. Frame Relay Connections o Connections are added using Cisco WAN manager o Frame Relay connections from IGX to BPX o ATM or Frame Relay connections from MGX to BPX o Connections are end-to-end and managed via SNMP © 2001 All Rights Reserved – BrainBuzz.com 21 TM Cramsession: Cisco WAN Switching Certification IGX 8400 Series • Multi-service switch supports WAN voice, data and video • 1 Gbps cellbus with a... manage the node using Cisco Wan manager (or the CLI) MGX 8850 MGX 8850 is an IP+ATM switch that can be used as a stand-alone device or as a feeder to a BPX 8600 series switch • As a feeder narrow-band and medium-band ATM, Frame Relay and voice into a single, wide-band ATM feeder trunk to the BPX © 2001 All Rights Reserved – BrainBuzz.com 32 TM Cramsession: Cisco WAN Switching Certification Stand-alone... that UPS meets Cisco requirements • Airflow and cooling must be suitable for the equipment being installed 2 Verify that all parts ordered are present and in good condition Record all part numbers and serial numbers © 2001 All Rights Reserved – BrainBuzz.com 12 TM Cramsession: Cisco WAN Switching Certification 3 Unpack and install the equipment in the desired rack (may be provided by Cisco or third... Alarm Relay module Front ARI Alarm Relay Interface, back card for ARM Back SCM System Clock Module, works with NPM Back Trunk cards (NNI) UXM Universal Switching Module © 2001 All Rights Reserved – BrainBuzz.com 23 Front TM Cramsession: Cisco WAN Switching Certification BC-UAI-4-155-MMF OC3/STM1, 2 or 4 port multimode or single mode fiber back card Back 3 or 6 port T3 back card with BNC connectors Back... Configure parameters Control templates-cnfict Channel utilization-cnfchutl Channel priorities-cnfchpri 11 Configure connections to access device (such as Cisco 3800) © 2001 All Rights Reserved – BrainBuzz.com 28 TM Cramsession: Cisco WAN Switching Certification o Up port to access device-upftcport o Add device to node-addad (view connected access devices with dspads) Default bandwidth parameters can... TM Cramsession: Cisco WAN Switching Certification Redundancy • Set up card redundancy-addyred (or addcdred) • Switch between active and redundant cards-resetcd • Switch between active and standby processor-switchcc BPX 8600 Series The BPX 8600 series switches are high capacity, standards based broadband ATM switches that support: • Backbone ATM • IP+ATM services • Multi Protocol Label Switching (MPLS)... card with the proper back card Installing BPX Cards • The card shelf has 15 slots numbered from left to right when viewed from the front © 2001 All Rights Reserved – BrainBuzz.com 17 TM Cramsession: Cisco WAN Switching Certification • When installing cards, follow ESD precautions • Slot 7 is reserved for BCC card Redundant nodes have a BCC card in slots 7 and 8 • Slot 15 is for the ASM/LM-ASM card pair... indicates the backplane is 19.2 Gbps capable • BCC-4 or later controller • Switch software release 8.1.18 or later • At least one BXM card © 2001 All Rights Reserved – BrainBuzz.com 18 TM Cramsession: Cisco WAN Switching Certification Table of BPX Cards Card Card Name Location BPX Common Core Group BPX-BCC-32 Broadband controller card, can be installed in redundant pairs Uses System Software ver 7.0 and... BPX-MMF-155-4-BC BPX-SMF-155-4-BC BPC-SMFLR-155-4-BC BPX-MMF-155-8-BC BPX-SMF-155-8-BC BPC-SMFLR-155-8-BC BPX-BXM-622 BPX-BXM-622-2 BPX-SMFLR-622-BC © 2001 All Rights Reserved – BrainBuzz.com 19 TM Cramsession: Cisco WAN Switching Certification BPX-XLR-622-BC 1500mm interface BPX-SMF-622-2-BC Back cards for BXM-622-2 and BME Single mode fiber, single mode, long range fiber and extra long-range fiber respectively .
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There are two standard headers. Cisco. multicasting, global
addressing and flow control. Cisco switches support LMI.
Cramsession: Cisco WAN Switching Certification
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