Transcript Semester 6 – Chapter 4 - YSU Computer Science

Semester 6 – Chapter 4
ISDN
ISDN Uses
• Used primarily as a WAN backup
technology
• to provide remote access to
telecommuters and small offices
• to support large numbers of POTS
(analog modem) and/or ISDN Basic
Rate Interface (BRI) calls.
DSL vs ISDN
• offers much higher throughput at a lower cost.
• However, ISDN still used because
– ISDN is more widely available than DSL or cable.
– Many companies and service providers have
made a significant investment in ISDN equipment
and training, and plan to continue leveraging that
investment.
– Remote offices using ISDN can connect to central
offices directly, without traversing the public
Internet. Most DSL and cable implementations
require the remote host communicate with the
central site using a VPN over the Internet.
ISDN Advantages Over Analog
(Asychronous)
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Higher Speed
Faster Call Setup
Cheaper than leased lines
Can run voice and data simultaneously
BRI Characteristics
• Two 64-kbps bearer channels
• One 16-kbps delta channel
• 48 kbps of framing and synchronization
information
• Total speed of 192 kbps
• Although not commonly done, you may
reference the total bandwidth of an ISDN BRI,
including framing and synchronization, which
is 192 kbps.
PRI over T1
• 23 64-kbps bearer channels
• One 64-kbps D channel, carried in
timeslot 24
• 8 kbps of framing and synchronization
information
• Total speed of 1.544 Mbps
PRI Over E1
• 30 64-kbps bearer channels
• One 64-kbps D channel, carried in
timeslot 16
• 64 kbps of framing and synchronization
information
• Total speed of 2.048 Mbps
ISDN Call Processing
• Signaling System 7 (SS7) protocols
used to set up a path inside the public
switched telephone network (PSTN)
• 931.q is used between end user and
ISDN switch
• D channel is used for signaling
Designations
• E Telephone network standards
• I Concepts, terminology, and methods
• Q Signaling and switching
PRI
• a channel service unit/data service unit
(CSU/DSU) is required to connect a router
(the TE) to the carrier network. Internal
CSU/DSUs are common among modular
routers.
• PRI's primary application is modem
aggregation – not point-to-point connectivity
• Can provide both analog and digital dial
solutions
ISDN and OSI Model
• Operates at layers 1 2, and 3
• Layer 1
– .430 for BRI, .431 For PRI, ANSI T1.601 for BRI
• Layer 2
– As specified by Q.921, the D channel typically
frames data using Link Access Protocol on the D
channel (LAPD)
• Layer 3
– the B channel can carry datagrams using a variety
of Layer 3 protocols, including IP, IPX, and
AppleTalk.
TE1 Addresses
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0-63 for non-automatic TEI assignment
64-126 for automatic TEI assignment
127 for group assignment, or broadcast
TEI works together with the service access
point identifier (SAPI) to complete the Layer 2
address
– SAPI is a 6-bit number used to identify and
manage
– TEI represents the specific ISDN device, while the
SAPI represents the specific process running on
that device
ISDN Call Termination
• disconnect
• release
• release complete
– It issues a disconnect message to the calling
party.
– It starts a timer to ensure receipt of a released
message.
– It disconnects the switched path.
– When a released message is received from the
preceding exchange, it returns a release complete
message to the preceding exchange.
ISDN Addressing Tasks
• Assign the IP address
• Assign dialer group (for DDR),
• Assign ISDN service profile statements (SPID
numbers
• Include a dialer map command that
associates a statically mapped destination to
a destination IP address, hostname, and
ISDN dial number.
• ISDN switch type can be set in global mode
or assigned to individual interfaces
BRI Interface Commands
• RTA(config)#interface bri 0
RTA(config-if)#isdn switchtype basic-5ess
• Router(config-if)#encapsulation ppp
• Router(config-if)#ppp authentication chap
• Other encapsulations
– encapsulation [ppp | labp | hdlc | x25 | cpp]
DDR Configuration
• 1.Define what constitutes interesting traffic by
using the dialer-list command.
• 2.Assign this traffic definition to an interface by
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using the dialer-group command.
• 3.Define the destination address, hostname, and
• telephone number to dial by using the dialer
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map command.
• 4.(Optional) Define call parameters by using other
• dialer commands such as dialer idle-timeout,
dialer fast-idle, and dialer load-threshold.
Dial-on-Demand Commands
• Router(config)#dialer-list dialer-group-number
protocol protocol-name {permit | deny}
• RTA(config)#dialer-list 1
• Router(config)#access-list access-list-number
[permit |deny] {protocol | protocolkeyword}{source source-wildcard |
any}{destination destination-wildcard |
any}[protocol-specific-options] [log]protocol ip
permit
Attach Dialer List to Interface
• Router(config)#dialer-list 1 protocol ip
permit
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Router(config)#interface bri0
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Router(config-if)#dialer-group 1
• Note: For a given protocol and a given
dialer group, only one access-list can be
specified in the dialer-list command.
Dialer Map Command
• Identifies destination router information, such as
the phone number to dial:
–
Router(config-if)#dialer map protocol next-hopaddress [name hostname] [broadcast] dial-string
• Cisco IOS commands often contain the word
"map," which is used to statically map Layer 2
addresses to Layer 3 addresses
• Dialer maps for inbound calls are maps between
protocol addresses and authenticated user names
Call Parameters
• Router(config-if)#dialer idle-timeout seconds
• Router(config-if)#dialer fast-idle seconds
• Router(config-if)#dialer load-threshold load
[outbound | inbound |
• To manually set the idle timeout value, use the
dialer idle-timeout command
– By default, the idle-timeout is set to 120 seconds either]
• The dialer load-threshold command is used to
specify the interface load at which the router will
initiate another call to the destination
DDR Environment
• In a DDR environment, dynamic routing
can be a source of problems.
• Routing protocols such as RIP and OSPF
rely on regular communication between link
partners.
• If routers are connected via a dial-up link,
active connections are usually intermittent.
Routing Solutions
• WAN core and remote sites run different
protocols, route redistribution may be necessary to
"share" routing information between the different
protocols.
• use static and default routing to address the
challenge of routing in a DDR network
• use dynamic routing, including route
redistribution, to propagate routes
– Use snapshot routing for serial connections
• Static routes are entered manually – no need
for routing tables
– Central(config)#ip route 172.24.2.0
255.255.255.010.2.3.2
• At least one static route pointing to the
next-hop IP address is necessary for DDR to
work
– Router(config)#ip route 0.0.0.0 0.0.0.0 {nexthop-address | exit-interface}
Redistributing EIGRP/Static
• RTA(config)#ip route 123.22.1.1
255.255.255.0 bri0
• RTA(config)#router eigrp 100
• RTA (config-router)# redistribute static
Passive Interface
• R(config)#IP route 10.0.0.1 255.255.0.0
192.16.3.0
• R(config)#router rip
• R(config)#version 2
• R(config)#network 10.0.0.0
• R(config)#redistribute static
• R(config)#passive-interface bri0/0
– To avoid routing updates initiating a call
Snapshot Routing
• RIP for IP, IGRP for IP, Novell RIP and SAP
for Novell IPX, Routing Table Maintenance
Protocol (RTMP) for AppleTalk, Routing Table
Protocol (RTP) for Banyan VINES
– When distance vector router updates are not considered
interesting traffic, router drops call and route will drop
from table
– The hellos from OSPF will keep initiating calls
• Redistribute routes and using RIP between serial
connections
Snapshot Routing
• Uses the client-server design model
– one router is designated as the snapshot server and one
or more routers are designated as snapshot clients
• At the end of the active period, the router takes a
snapshot of the entries in its routing table. These
entries remain frozen during what is called the
quiet period
– client router determines the frequency at which it calls
the server router. The quiet period can be as long as
100,000 minutes (over 69 days)
Snapshot Commands
• Router(config-if)#snapshot server active-time
[dialer]
• Router(config-if)#snapshot client active-time
quiet-time [suppress-statechange-updates]
[dialer]
• Router(config-if)#dialer map snapshot sequencenumber dial-string
– The value of the active-time argument must be the same
for the client and server routers
– make sure your active time is long enough to allow any
routing updates to be sent
Suppress-Statechange
• suppress-statechange-update option disables
the exchange of routing updates each time
the line protocol goes from "down" to
"up"or from "dialer spoofing" to "fully up.
• The dialer map snapshot command specifies
which router to call as the snapshot
server.spoofing" to "fully up.
Aggregation
• Cisco Proprietary BOD
– triggered by outgoing traffic levels only
– load value is a number from 1 to 255
• 1 IS 0%; 255 IS 100%
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Multilink PPP (MLP)
– Triggers by outgoing or incoming traffic
– Both of these methods require the dialer load-threshold
command
• Router(config-if)#dialer load-threshold [inbound | outbound |
either ]
• only one end of a link should be configured with the dialer
load-threshold command.
Use PPP Multilink
• Asynchronous serial interfaces in dialer
rotary groups
• Synchronous serial BRI
• Multiple BRIs in dialer rotary groups
• Multiple BRIs using dialer profiles
• PRI B channels in dialer rotary groups
Accepting Calls
• You can ensure that only a single device answers
an incoming call by verifying the number or
subaddress in the incoming call against the device
configured number, subaddress, or both.
• ISDN routers can be configured to screen
incoming calls by using calling line identification
(CLID)
– Router(config-if)#isdn caller phone-number
ISDN Rate Adaptation
• Router(config-if)#dialer map protocol nexthop-address [name name] [speed speed]
[broadcast] dial-string
– Assigned on per destination basis
– Lower speed is accepted
Debugging Commands
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Show ip int bri0/0
Show ip int brief
Show isdn status
Show isdn history
Show dialer
Show ppp multilink
Debug dialer
Debug ppp multilink
Debug isdn events
Debug ppp authentication | negotiation
D Channel Debugging
• debug isdn q921 at Layer 2
• debug isdn q931 at Layer 3.
– display information about call setup and
teardown of ISDN network connections at
Layer 3 on the D channel.
• includes a call setup message, indicated by
"SETUP" in the first line.
• In the second line, the Bearer Capability value of
0x8890 indicates that the coding standard used is
ITU-T and the circuit mode is 64kbps.
PRI Configuration
• .Specify the correct PRI switch type that the
router interfaces with at the provider's Central
Office (CO).
• Specify the T1/E1 controller, framing type, and
line coding for the provider's facility.
• Set a PRI group timeslot for the T1/E1 facility and
indicate the speed used.
• Identify the interface that you will configure to act
with DDR.
T1/E1 Configuration
• Router(config)#controller {t1 | e1}{slot/port | unit
number}
• Router(config)#controller t1
• Router(config-controller)#framing {sf | esf}
• Router(config-controller)#framing{crc4 | no-crc4}
[australia]
• Router(config)#controller e1
• Router(config-controller)#framing crc4
• Router(config-controller)#linecode hdb3