BCRAN - Fundamentals

WAN Connection Characteristic:
1. Dedicated connection
- Circuit switching
- End to End. i.e phone.
2. On-demand connection
- packet switching
- broadband.

Dedicated Circuit-switched Connection:
1. Leased Lines:
Router -----CSU/DSU----------CSU/DSU-------Router

2. TDM Circuits

Packet-Switched Connections:
- Virtual circuit (frame relay/ATM)
- Share bandwidth statistically

Broadband Access:
- Use existing infrastructure
- Terminate at service provider POP Internet transport.

DSL Limitation:
- Distance. The closer you need to be to the nodes to provider faster connection to nodes.
- Currently, ADSL requires 1.5km.

- A WAN can be characterized by connection duration, type of switching, form of synchronization, data rate, termination and media type.
- WAN connection types are dedicated, on-demand circuit-switched, packet-switched, and broadband.
- Dedicated connection are continuously available, typically using a CSU/DSU to connect to service provider time-division multiplexing (TDM) network.
- Asynchronous on-demand circuit-switched connections used a process such as DDR when there is a bacup connection needed.
--> Floating static route.

Defining WAN Encapsulation Protocols:
1. PPP
- Open standard
- Multilink (bundling)
- Authentication (CHAP, PAP, MSCHAP)
- Compresion
- Error detection (magic sequence number)
- Vendor specific (Every vendor has own HDLC)
3. Frame-Relay

PPP Encapsulation:
1. LCP (Link Control Protocol)
- Layer 2 (carries multi-protocol across)
- Authentication, compression

2. NCP
- Layer 3

Frame Relay:
- Cost saving
- Leased line is very expensive, depending on distance.
- Frame relay can work up to a maximum of E3 line. (30 * 64) =1920 mbps.

WAN Connections:
Leased Line - High control, full bandwidth, high-cost enterprise networks, and last-mile access.
+ Cable - A very fast connection shared through a LAN to the Internet. Low cost, but performance can vary.
--> MODEM is different.
A COAX cable has to be pulled from the fiber optic switch.
+ DSL - Converts existing telephone lines into access paths for multimedia and high-speed data transfers. Most high-performance DSL connections have distance limitations.
ISDN - Creates a digital loop. Higher bandwidth than typeical dialup, often with significatnly higher cost.
Analog - Slow setup and transmission speeds. Location flexibility.

Connection Selection Considerations:

- Selecting a WAN connection involves considering things as - Availability, Bandwidth, Cost, Ease of management, Application traffic, QoS and reliability, Access control

MODEM for out-of-band-management:
- Console, AUX and TTYp are out-of-band or backdoor management.
- In-band interfaces are ethernet and etc.

Vulnerability and risk:
- Add a terminal server that provides more secured access.
- Limit access to modems, phone numbers and etc.
- AUX port to cable --> using straight cable.

CTS = Clear to Send
RTS = Ready to send
DSR = Data set ready

Configuration of AUX line:
router(config-line)#modem autoconfigure discovery
router(config-line)#speed 56000
router(config-line)#transport input telnet
router(config-line)#flowcontrol hardware
router(config-line)#pass cisco

Terminating a call over the analog phone line:
DTE-initiated termination
- Router or laptop drops DTR
- Modem must be programmed to terminate connection on loss of DTR and restore to saved settings.
- Triggered by users.

DCE-initiated termination
- Router detects CD low and terminates connection.
- Modem must be programmed so that CD reflects the carrier state.
- Triggered by the other side.

"debug confmodem"
Different modem has different AT commands.

- Out-of band management uses an AUX or console port; in-band management uses regular interfaces.
- Modems can provide dial-up connectivity to a router for out-of-band administration and troubleshooting.

Describing PPP Fundamentals:

"ip unnumbered loopback 0" - when people connect to my router via the aux port, it will always resume the IP of the loopback 0.
"async dynamic address" - when connected, you get an IP address.

- Asynchronous connections can be used either an in-band PPP session or an out-of-band EXEC session.
- To start either a PPP session or an EXEC session, use the async mode interactive command.

PPP Authentication:
CHAP uses plain-text while PPP uses MD-5 encryption.

labC(config)#username EVEN password 2468
labC(config)#int serial 0
labC(config-if)#ppp authentication pap
labC(config-if)#ppp pap sent-username ODD pass 1357
labC(config-if)#int serial 1
labC(config-if)#ppp authentication pap
labC(config-if)#ppp pap sent-username ODD pass 1357

Backward Compatible:
lab(config-if)#ppp authentication pap chap --> if pap doesn't work, try using chap.

- When user enters the ppp command, the system determines the type of authentication configured. if no authentication is configured, the PPP process starts immediately.
- PPP is a one-way authentication between a host and a router or a two-way authentication between routers. It sends a password in plaintext.

PPP Callback and Compression:

Setup a normal ISDN:

1. Apply IP address to BRI0
2. Apply the appropriate IDSN switchtype - Basic NAT 3
3. Apply PPP encapsulation.

PPP Callback configuration:
labA(config)#username routerB password cisco
labA(config)#int bri 0
labA(config-if)#dialer map ip name labB **21
labA(config-if)#ppp callback request
labA(config-if)#ppp authenticate chap callin
labA(config)#username labB pass cisco --> create username and password for CHAP.

labB(config-if)#encap ppp
labB(config-if)#dial callback-secure
labB(config-if)#dialer map ip name labA class callback **11
labB(config-if)#ppp callback accept
labB(config-if)#ppp authentication chap

labB(config)#map-class dialer callback --> create a map class called "callback"
labB(config-map-class)#dialer callback-server username --> dialer for callback-server will be sending across a username

- Predictor (router to router)
+ based on hash
+ CPU intensive technique

- Stacker (router to router)
+ Substitution
+ Memory intensive

- MPPC : Proprietary standard by Microsoft.
+ Memory intensive

- TCP header (host to router)
+ Only can be applied to asynchronous interface (bcoz it is from host to router)
+ Memory intensive

labC(config)#int serial 1
labC(config-if)#compress stac

MP3, ZIP and etc are compressed files. Thus, if you apply compression to these files, it will be redundant.

Multilink PPP:
- When you perform a dial-up, only one B-Channel will open up.
- Packet fragmenting.

labC(config)#int bri0
labC(config-if)#encap ppp
labC(config-if)#ppp multilink
labC(config-if)#dialer load-threshold 1 either

In BCMSN, when created an etherchannel, a port-channel will be created.
Over here, when created a multilink, a virtual-access channel will be created.


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