Transcript Chapter 14

Chapter 14
Wide Area Networks
Introduction
►The main difference between LAN and WAN is distance
►Generally WAN services are leased from service providers
►The idea of using WAN protocols is to change networks with large distances
between them into LAN-like connected network
Defining WAN Terms
☼Customer premises equipment: (CPE) Customer premises equipment (CPE)
is equipment that’s owned by the subscriber and located on the subscriber’s
premises.
☼Demarcation point: The demarcation point is the precise spot where the
service provider’s responsibility ends and the CPE begins. It’s generally a device
in a telecommunications closet owned and installed by the telecommunications
company (telco). It’s your responsibility to cable (extended demarc) from this box
to the CPE, which is usually a connection to a CSU/DSU or ISDN interface.
☼Local loop: The local loop connects the demarc to the closest switching office,
which is called a central office.
☼Central office (CO): This point connects the customer’s network to the
provider’s switching network. Good to know is that a central office (CO) is
sometimes referred to as a point of presence (POP).
☼Toll network: The toll network is a trunk line inside a WAN provider’s network.
This network is a collection of switches and facilities owned by the ISP.
Data Terminal Equipment (DTE) & Data
Communicational Equipment (DCE)
►All CISCO serial interfaces are DTE and they need a DCE to provide clock rate
to them
►The Channel Service Unit/ Data Service Unit (CSU/ DSU) provides clock rate
and makes connection between Digital LAN network & Digital WAN network
►The modem provides clock rate and makes connection between Digital LAN
network & Analogue WAN network
WAN Services focus on:
Layer 2
Layer 1
Cables
Major cables are Serial cables:
DB-60 pin from router side and
EIA/TIA-232
EIA/TIA-449
V.35
X.21
EIA-530(DTE only) at CSU/DSU side
Encapsulation
WAN encapsulation protocols
HDLC, PPP, Frame Relay,
X.25, ATM, LAPB, LAPD,
PPPoE, Cable, DSL, MPLS
WAN Connection Types
•All these encapsulation protocols make error detection since they all use CRC
in the FCS of the frame
•LAPD is the only protocol who by default make Error Correction, PPP also
support error correction but it’s not enabled by default
Leased lines
►referred to as a point-to-point or dedicated connection
►pre-established WAN communications
►no hard setup procedures are required
►expensive
►synchronous serial lines
►up to 45Mbps
►frequently use HDLC and PPP
High Level Data Link Control
(HDLC)
•Protocol at Data Link layer.
•Encapsulate only one Network Layer
protocol (IP, IPX, or Apple Talk) at the
same link.
•Work only on Synchronous Interfaces
(Serial, BRI) and is the default
encapsulation on all CISCO Serial
Interfaces.
•Does not have Authentication, Callback,
or Dynamic addressing capability.
•Work only on similar vendors.
Point-To-Point Protocol
(PPP)
•Protocol at Data Link layer.
•Can Encapsulate several Network Layer
protocol (IP, IPX, or Apple Talk) at the
same link.
•Work on Synchronous Interfaces (Serial,
BRI) and Asynchronous Interfaces (Aux).
•Support Authentication, Callback, and
Dynamic addressing capability.
•Can Work on different vendors.
PPP uses
1- LCP Line Control Protocol
-It is a method for Establishing, configuring maintaining and
terminating PPP connection
-LCP offers different PPP encapsulation options:
-authentication
-compression
-error detection
-multilink
-PPP callback
2- NCP Network Control Protocol
allow PPP to simultaneous use of multiple network layer protocols, for
example IPCP ( Internet Protocol Control Protocol)
PPP Session Establishment
1. Link establishment phase
each router sends LCP packet to configure and test the link, the LCP packet
contains the option field to negotiate about authentication, compression, data size
2. Authentication phase
using PAP or CHAP
3. Network layer protocol phase
the PPP will use NCP to choose the network layer like IP
PPP Authentication Methods
Password Authentication Protocol
(PAP)
Challenge Handshake Authentication
Protocol (CHAP)
Two-way Handshake
Three-Way Handshake
•Remote Router sends his user name and
password and continue until authentication
is acknowledged or connection is
terminated
•Password is sent in clear text
•Remote Router is in control of the
frequency and timing of the login
attempts
•Local Router sends “Challenge”, the
remote router. Response with a value
calculated using one-way hash function
MD5 based on Password and Challenge
message
•The local router checks the response by
his own expected hash if the value match
authentication is acknowledged or
connection is terminated
•The hash value is unique and random
(actual password is not sent across the
link)
•Local Router controls the frequency and
timing of challenges
Configuring PPP
Router(config)#hostname RouterA
RouterA(config)#enable secret cisco
RouterA(config)#username RouterB password cisco
RouterA(config)#int s0
RouterA(config-if)#encapsulation ppp
RouterA(config-if)#ppp authentication chap pap
RouterA(config-if)#ppp pap sent-username RouterA password cisco
Viewing PPP Status
RouterA#sh int s0
1. Authenticated but without checking IPs
UP
UP
LCP
Open
Open: IPCP
Check validity of IPs using command: Router#sh cdp neighbors detail
2. Wrong password or user name
UP
Down
LCP
Closed
Closed: IPCP, CDPCP
3. Mismatched encapsulation
UP
Down
LCP
REQsent
Closed: IPCP, CDPCP
RouterA#debug ppp authentication
Packet Switching
►always connected (like leased line)
►bandwidth sharing
►synchronous serial
►56Kbps to 45Mbps
►use virtual circuit
►to send data constantly DO NOT USE PACKET SWITCHING
►frame relay and X.25 are packet switching technologies
Frame Relay
►saves money
►high performance
►successor of X.25 but does not use error correction
►Non Broadcast Multi Access NBMA (i.e. by default no broadcast is passing through it)
►dynamic bandwidth allocator
►connection oriented data-link technology
►deals with data-link layer and physical layer
►in data-link layer frame-relay encapsulates information from the upper OSI layers, as
example IP traffic would be encapsulated into a frame format that can be transmitted
over frame-relay link
►in physical layer the same serial cables that support ppp support frame-relay, they are:
EIA/TIA-232, EIA/TIA-449, V.35, X.21 EIA/TIA-530
Why we use Frame Relay
Frame-relay reserves the leased B.W to you, this B.W is a part of a shared B.W (let’s
say 256 Kbps of 1.544 Mbps)
When the rest of the B.W is not used you can use it, this is offered by packet-switch
nets
Frame-relay sites will share telecommunication company backbone net
Telecommunication company switches are responsible of mapping the connections
between the sites
Frame Relay Structure
T1 Link
1.544 Mbps
CIR
256 Kbps
Frame Relay Terminology
Access
Rate
128 Kbps
T1: 1.544 Mbps
a
Access Rate: the maximum speed that
frame relay interface can transmit
CIR (Committed Information Rate): the
maximum B.W that your service provider
guarantee to be delivered
b
256 Kbps
c
64 Kbps
Supposing link a and link b are not transmitting right now then link c can extend
beyond the 64 Kbps and use all available B.W that may reach to 1.544 Mbps
Any sent data more than CIR is flagged with the Discard Eligibility (DE)= 1
When congestion happens in frame-relay switch, it sends Backward Explicit
Congestion Notification (BECN) to the source, sends Forward Explicit
Congestion Notification (FECN) to the destination, and starts deleting any packet
with DE= 1
When notifications reach source and destination they both start using flow
control
DLCI Data Link Connection Identifier
DLCI is a number that identify the logical circuit between router and frame-relay switch
(16 - 1007), it is supplied by provider.
Router(config-if)#frame-relay interface-dlci 400 <16 - 1007>
Local DLCI
Global DLCI
LMI Local Management Interface
Signaling standard between router and frame relay switch
LMI is responsible for managing the connection and maintaining the status between
devices
It will provides messages about
Keepalive: verify that data is flowing
Multicasting: allow efficient distribution of routing information and ARP requests over
frame relay network. Multicasts use DLCI 1019 – 1022
Global addressing: allow global significant making frame relay cloud to work exactly
like LAN
Status of virtual circuit:
Active: every thing is up and routers can exchange information
Inactive: remote router is not working
Deleted: no LMI is being received from switch could be line failure
LMI Types:
Cisco (also called gang of four)
ANSI
Q.933A
Router(config-if)#frame-relay lmi-type cisco
ansi
q933a
Auto sensed in 11.2 or newer
DLCI Mapping
Dynamic Mapping x Static Mapping
In order For each router to get to the remote router ,it will built Mapping Table in
one of two way :
1. Dynamic Mapping using Inverse ARP .
2. Static Mapping.
Both map Local DLCI no. with Remote Router IP address.
Router(config)#frame-relay inverse-arp protocol DLCI
Protocol: IP, IPX, Apple Talk
DLCI: DLCI of the interface we want to exchange IARP
IARP is ON by default
Frame Relay switch builds mapping table by doing the following:
1. Reads source DLCI
2. Searches the opposite DLCI
3. Sends the slot port that is connected to the destination
Static Mapping
Static mapping is used to spread broadcast (for example to publish RIP)
Router(config-if)#frame-relay map protocol destination_address local_DLCI broadcast
Frame Relay Encapsulation Types
• Cisco (default)
• IETF Internet Engineering Task Force
Router(config-if)#encapsulation frame-relay
Router(config-if)#encapsulation frame-relay ietf
Frame Relay Topologies
Star (Hub and Spoke)
• Least expensive Topology
• Most Poplar
• Use single interface
• Must use subinterfaces to connect to multiple PVCs
Full Mesh
• Costly
• Needs direct connection to each site (many physical interfaces)
• Redundancy
Partial Mesh
• Not all sites have direct access to all other sites
Configuring Frame Relay
RouterA(config)#int s0
RouterA(config-if)#ip add 172.16.5.5 255.255.255.0
RouterA(config-if)#no shut
RouterA(config-if)#encapsulation frame-relay
RouterA(config-if)#frame-relay interface-dlci 100
RouterB(config)#int s0
RouterB(config-if)#ip add 172.16.5.7 255.255.255.0
RouterB(config-if)#no shut
RouterB(config-if)#encapsulation frame-relay
RouterB(config-if)#frame-relay interface-dlci 400
RouterB(config-if)#frame-relay lmi-type ansi
No static mapping is required because IARP is
on but if you turn it off then static mapping will
be like this:
No static mapping is required because IARP is
on but if you turn it off then static mapping will
be like this:
RouterA(config-if)#frame-relay map ip 172.16.5.7
100 broacast
RouterB(config-if)#frame-relay map ip 172.16.5.5
400 broacast
Configuring Subinterfaces
Point-to-Point
Multipoint
• Each point-to-point subinterface requires
it’s own subnet
•Subinterfaces act like leased lines
• Use single subnet so it saves address
space
• Subinterfaces act like NBMA so they do not
solve split-horizon problem
Configuring Point-to-Point
RouterA(config)#int s0/0
RouterA(config-if)#no ip add
RouterA(config-if)#no shut
RouterA(config-if)#encapsulation frame-relay
RouterA(config-if)#int s0/0.110 point-to-ponit
RouterA(config-subif)#ip add 172.17.0.1 255.255.255.0
RouterA(config-subif)#frame-relay interface-dlci 110
RouterA(config-subif)#bandwidth 64
RouterA(config-subif)#int s0/0.120 point-to-ponit
RouterA(config-subif)#ip add 172.18.0.1 255.255.255.0
RouterA(config-subif)#frame-relay interface-dlci 120
RouterA(config-subif)#bandwidth 64
172.17.0.2
S0/0.110 172.17.0.1
DLCI 110
RouterB
RouterA
RouterC
S0/0.120 172.18.0.1
DLCI 120
172.18.0.2
Configuring MultiPoint
RouterA(config)#int s0/0
RouterA(config-if)#no ip add
RouterA(config-if)#no shut
RouterA(config-if)#encapsulation frame-relay
RouterA(config-if)#int s0/0.2 multiponit
RouterA(config-subif)#ip add 172.17.0.1 255.255.255.0
RouterA(config-subif)#bandwidth 64
RouterA(config-subif)#frame-relay map ip 172.17.0.2 120 broadcast
RouterA(config-subif)#frame-relay map ip 172.17.0.3 130 broadcast
RouterA(config-subif)#frame-relay map ip 172.17.0.4 140 broadcast
172.17.0.2
S0/0.210 172.17.0.1
DLCI 120
DLCI 130
DLCI 140
172.17.0.3
172.17.0.4
Configuring 2500 Router to act like
Frame Relay Switch
2500(config)#frame-relay switching
2500(config)#int s0
2500(config-if)#no ip add
2500(config-if)#no shut
2500(config-if)#clock rate 56000
2500(config-if)#encapsulation frame-relay
2500(config-if)#frame-relay intf-type dce
2500(config-if)#frame-relay route 110 interface s1 220
2500(config-if)#int s1
2500(config-if)#no ip add
2500(config-if)#no shut
2500(config-if)#clock rate 56000
2500(config-if)#encapsulation frame-relay
2500(config-if)#frame-relay intf-type dce
2500(config-if)#frame-relay route 220 interface s0 110
2500
2600A
S0/1
DLCI 110
IP 172.17.0.1 /30
S0
S1
Frame Relay
Switch
2600B
S0/0
DLCI 220
IP 172.17.0.2 /30
Show Frame-relay CMDs
Router#sh int s0/0
To view encapsulation, LMI DLCI (default 1023, ansi or q.933a 0), B.W, MTU, Keepalive,
MAC, Status of interface
Router#sh frame-relay map
To view value of DLCI, IP of next hop, MAPPING TYPE [dynamic (IARP), static
(broadcast)]
Router#sh frame-relay pvc
To view PVC status, no. of each type of PVC, value of DLCI, presence of congestion,
presence of packets with DE= 1, BECN and FECN
Circuit Switched
►like phone call
►low cost
►no data can transfer before an end-to-end connection is established
►uses dial-up modems or ISDN
►low-bandwidth
►asynchronous serial
ISDN (Integrated Service Digital
Network)
►a replacement to the traditional analogue modem
►features:
1. Ability to carry variety of user traffic, video, telex, and telephone, in the same time
2. Faster call setup (less than a second) by using D-channel (Delta-channel) which is
responsible of call setup, alarm messages (signaling information)
3. Faster data transfer rate using B-channel (Bearer-channel) (64Kbps), each Bchannel can carry one type of data
ISDN Standard Access Methods
BRI Basic Rate Interface
2B
+
2x64K
+
1D
1x16K
(max B.W)= 144Kbps
1D
1x64K
~
(max B.W)= T1 1.544Mbps
1D
1x64K
~
(max B.W)= 2.048Mbps
PRI Primary Rate Interface
USA and Japan
23B
+
23x64K +
Europe
30B
+
30x64K +
BRI and PRI Call Process
1.
2.
3.
4.
The D-channel from the local router to the local switch comes up
The ISDN switch uses Signaling System 7 SS7 to setup a path to remote switch
The remote switch setup the D-channel link to the remote router
The B-channels are then connected end to end
ISDN Components
‼Function (Devices)
•
•
Native ISDN (TE1): device with BRI interface
Non-native ISDN (TE2): device without BRI interface (serial only)
‼Reference Point (Interface cables)
R
S
T
U
U
TE1
NT1
BRI
U
S/T
NT1
TE1
R
R
U
S/T
NT1
TA
U
S/T
TA
NT1
NT2
S/T
ISDN Service Provider
•
•
•
•
ISDN Basic Configuration
Router(config)#isdn switch-type basic-ni to define type of switch of provider
Router(config)#int bri0
Router(config-if)#isdn spid1 123…12 5551111 a SPID is a number supplied by the
provider to identify line configuration of BRI service
Router(config-if)#isdn spid2 123…12 5552222
Dial- on Demand Routing DDR
1. The message reaches the router and be compared with R.T, the router determines the
exit interface. If it is the BRI then
2. Check that is the message allowed to pass through DDR, if yes then establishment of
call (D-channel is working)
3. The router determines the next hop and determines how to call it
4. Wait 120 sec idle then disconnect if there is no traffic
Configuring DDR
1. Define static routes
2. Define the interest traffic (also known as dialer list)
3. Dialer information (no. to call) + BRI interface (on which dialer list will applied)
RouterA
RouterB
BRI1
ISDN Network
10.10.0.1
5551000
BRI0
10.10.0.2
5552000
10.30.0.0
Step 1: Define static routes
RouterA(config)#ip route 10.30.0.0 255.255.255.0 10.10.0.2
RouterA(config)#ip route 10.40.0.0 255.255.255.0 10.10.0.2
RouterA(config)#ip route 10.10.0.2 255.255.255.255 bri1
10.40.0.0
Step 2: Define the interest traffic (also known as dialer list)
RouterA(config)#dialer list 1 protocol IP permit
OR
RouterA(config)#dialer list 1 protocol IP list 110
RouterA(config)#access-list 110 permit tcp any any eq telnet
Step 3: Dialer information (no. to call) + BRI interface (on which dialer list will applied)
RouterA(config)#int bri1
RouterA(config-if)#ip address 10.10.0.1 255.255.255.0
RouterA(config-if)#no shut
RouterA(config-if)#encapsulation ppp
RouterA(config-if)#ppp authentication chap
RouterA(config-if)#dialer-group 1
RouterA(config-if)#dialer string 5552000
OR
RouterA(config-if)#dialer map IP 10.10.0.2 name RouterB 5552000
RouterA(config-if)#dialer idle-timeout 120
RouterA(config-if)#dialer load-threshold 125
Show ISDN CMDs
To view current call, phone number, and time left to end call
Router#sh isdn active
To check for switch connectivity problems
Router#sh isdn status
To view number of reached dialer string, idle time out of B-channel, and good
information about dialer
Router#sh isdn dialer
To view layer 2 information only
Router#sh isdn q921
To view layer 3 information, including call setup and teardown
Router#sh isdn q931
To debug using call setup and teardown activity
Router#debug dialer
Router#isdn disconnect bri0 or Router(config-if)#shutdown
Cable and DSL
How to select
1. Speed
2. Security
3. Popularity
4. Customer Satisfaction
Cable
1. Headend
2. Distribution network: HFC Hybrid Fiber-Coaxial architecture with 1002000 customers
3. DOCSIS (data over cable service interface specification)
Digital Subscriber Line (DSL)
Most popular types are:
• Symmetrical DSL
• Asymmetrical DSL
But The term xDSL covers a number of DSL variations, such as ADSL, high-bit-rate DSL
(HDSL), Rate Adaptive DSL (RADSL), Synchronous DSL (SDSL), ISDN DSL (IDSL), and
very-high-data-rate DSL (VDSL) which is employed by cisco to build new technology
called Cisco Long Range Ethernet (LRE) with speeds from 5 to 15Mbps (full duplex)
at distances up to 5,000 feet traveling over existing twisted-pair wiring