Transcript Cisco S4C5

Cisco S4C5
ISDN
ISDN
• Designed to solve low bandwidth problems
in small offices
• Also designed for dial-in users with
traditional telephone dial-in services
• Designed to use existing telephone wiring
• WAN length brought up for duration of call
• Sane process as when you call a friend
Benefits
• Carries many types of network traffic (data, voice,
video)
• Sets up calls faster than basic telephone service
• Faster data transfer rate than modems
– Uses D channel (out of band) signaling
– B channel 64 Kbps up to 128 when both B channels are
used
• Uses UNI (user-network interface)
• International compatibility
– Standards for end-to-end digital connectivity
ISDN Components
• TE1
connects to network termination of type
1 or 2 –device compatible with ISDN
• TE2
device that is not compatible– requires
terminal adapter
• TA
Converts standard electrical signals to
ISDN form
• NT1
Connects four-wire ISDN subscriber
wiring to conventional two-wire local loop
• NT2
performs layer 2 and layer 3 protocol
services
ISDN Reference Points
• R connections between non ISDN and a
TA
• S connections to customer switching
device
• T outbound connection from NT2 to ISDN
or NT1
• U connections NT1 and ISDN owned by
telephone company – only in NA
Switch Types
• North America
– AT&T 5ESS
Nortel DMA-100
Japan
NTT
UK
Net3 Net5
ISDN Protocols
• E recommend telephone network
standards; e.g. E.164 international
addressing
• I concepts, terminology and methods; e.g.
I.100 concepts and structure
• Q switching and signaling; signaling
means process of call setup
Layers
• Physical
– ISDN BRI and PRI
• Data Link
– LAPD; LAPB
• Network Layer
– Q.930 – user to user, circuit switched, and
packet switched connections
Physical Layer
• 48 bits or 24 bits plus 24 bits
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Framing – synchronization
Load Balancing
Echo of previous D channel bits
Activation bit
Spare bit
B1 channel bits
B2 channel bits
D channel bits
• 8000 frames per second; effective rate is 144 Kbps
Data Link Layer
• Flag, address, control, data, FCS, flag
• Address – SAPI C/R EA TEI EA
• LAPD – similar to HDLC
– Used to ensure control and signaling
information flows and is received properly
– Flag and control fields identical to HDLC
– The address field can be expanded to 2 bytes
Network Layer
• ITU-T.1.450
• ITU-TQ.931
– Support user to user, circuit switched and
packet switched connections
– Specifies call establishment, termination,
information, and miscellaneous messages
ISDN and OSI Reference Model
• Two most common encapsulations
– PPP and HDLC
– ISDN defaults to HDLC
– PPP is more robust – authentication and negotiation of
compatible link and protocol configuration
• ISDN allows only one encapsulation type
– Most use PPP – peer to peer
– Can be used by IP and IPX to establish network
connectivity
– PPP specified by RFC 1661 – open standard
– PPP uses LCP to establish link
PPP Security
• PAP
Password Authentication Protocol
• CHAP Challenge Handshake
Authentication Protocol
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If syn used on one end, asyn used on other
LCP established Point to point
PPP provides primary security – RFC 1334
CHAP is bidirectional
PAP is unidirectional
ISDN Uses
• Remote access
– Lowest speed link in enterprise
• Remote nodes
– Remote user appears to be network node
– Components are ISDN router and remote client sw
• Small office/home office
– ISDN router with multiple users - dialup
– Fees depend on geographic area, service availability,
and billing method
– May be distance limitations
ISDN Services
• BRI
– 2 B and 1 D channel, 144 kbps total bandwidth
– B channels provide service; D channel used for
signaling
• PRI
– 23 B 8-bit channels and 1 8-bit D channel
– 1.544 Mbps
– In Europe, 30 8-bit channels and 1 D
How It Works
• Routers provide routing by using DDR (dial
on demand) routing to provide transparent
connectivity
• DDR controls B channels based on load
thresholds
• Multilink PPP is used to provide bandwidth
aggregation
Configuration Tasks
• Global
– Select switch type, specify traffic to trigger DDR call
• Set destination details
• Interface Configuration
– Select interface specs, configure ISDN addressing
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Specify BRI and number for BRI port
Configure with ID supplies by service provider
Can configure waiting time for carrier to respond
Involves ISDN, switch type, and ISDN SPIDs
BRI Configuration
• INTERFACE BRI 0
– Number describes port, connector, or interface
card number
– Displayed with SHOW INTERFACES
command
Switch Types
• Need to define ISDN Switch type before
using BRI
• Use global configuration mode
– ISDN Switch-type name-of-switch-type
SPIDS
• ISDN spid1 spid-number [idn] seta a B
channel service profile identifier
– SPIDs allow multiple ISDN devices to share
local loop
– Typically used for dialup connectivity
Typical Commands
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Isdn switch-type
Dialer-list 1 protocol ip permit
Interface bri 0
Dialer-group 1
Dialer wait-for-carrier-time
Ip
Bane
Connection number
Show ISDN status
DDR Operations
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Ping/Telnet
Show dialer – diagnostics
Show ISDN Active – monitor call in progress
Show ISDN status – shows statistics of all line
connections
• Debug isdn q921
• Debug dialer
• Clear interface