2. History and usage of PPP related to OSI layers.

PPP creates data paths and sets up flow control between devices on a WAN enviroment. PPP uses a layered architecture based on the OSI model
Network Layer - Protocols
Data Link Layer - Auth, etc, LCP
Physical Layer - Der...

3.

TE1 - S - NT2 - T - NT1 - U - Frame Relay Cloud
TE2-R-TA---^

R — References the connection between a non-ISDN compatible device Terminal Equipment type 2 (TE2) and a Terminal Adapter (TA), for example an RS-232 serial interface.

S — References the points that connect into the customer switching device Network Termination type 2 (NT2) and enables calls between the various types of customer premises equipment.

T — Electrically identical to the S interface, it references the outbound connection from the NT2 to the ISDN network or Network Termination type 1 (NT1). 

U — References the connection between the NT1 and the ISDN network owned by the telephone company. 

4.

called a virtual circuit (VC). Virtual circuits may be established dynamically by sending signaling messages to the network. In this case they are called switched virtual circuits (SVCs). However, SVCs are not very common. Generally permanent virtual circuits (PVCs) that have been preconfigured by the carrier are used. A VC is created by storing input-port to output-port mapping in the memory of each switch and thus linking one switch to another until a continuous path from one end of the circuit to the other is identified. 

5. WAN Devices

Router - Routes... duh?
Switch - Switches... der?
CSU/DSU - The communications link needs signals in an appropriate format. For digital lines, a channel service unit (CSU) and a data service unit (DSU) are required. The two are often combined into a single piece of equipment, called the CSU/DSU. The CSU/DSU may also be built into the interface card in the router.
Communication Server - Communication servers concentrate dial-in user communication and remote access to a LAN. They may have a mixture of analog and digital (ISDN) interfaces and support hundreds of simultaneous users.
CPE - Devices on the subscriber premises are called customer premises equipment (CPE).  The subscriber owns the CPE or leases the CPE from the service provider. A copper or fiber cable connects the CPE to the service provider’s nearest exchange or central office (CO). This cabling is often called the local loop, or "last-mile". A dialed call is connected locally to other local loops, or non-locally through a trunk to a primary center. It then goes to a sectional center and on to a regional or international carrier center as the call travels to its destination. 
DCE/DTE - In order for the local loop to carry data, a device such as a modem is needed to prepare the data for transmission. Devices that put data on the local loop are called data circuit-terminating equipment, or data communications equipment (DCE). The customer devices that pass the data to the DCE are called data terminal equipment (DTE).  The DCE primarily provides an interface for the DTE into the communication link on the WAN cloud. The DTE/DCE interface uses various physical layer protocols, such as High-Speed Serial Interface (HSSI) and V.35. These protocols establish the codes and electrical parameters the devices use to communicate with each other. 
MUX - Multiplexer - A scheme that allows multiple logical signals to be transmitted simultaneously across a single physical channel. Compare with demultiplexing. 

6. PPP Frames

Flag | Address | Control | (DATA) | FCS | Flag

9. PPP Link Establishment

Link-establishment phase - In this phase each PPP device sends LCP frames to configure and test the data link. LCP frames contain a configuration option field that allows devices to negotiate the use of options such as the maximum transmission unit (MTU), compression of certain PPP fields, and the link-authentication protocol. If a configuration option is not included in an LCP packet, the default value for that configuration option is assumed.  Before any network layer packets can be exchanged, LCP must first open the connection and negotiate the configuration parameters. This phase is complete when a configuration acknowledgment frame has been sent and received. 
Authentication phase (optional) - After the link has been established and the authentication protocol decided on, the peer may be authenticated. Authentication, if used, takes place before the network layer protocol phase is entered. As part of this phase, LCP also allows for an optional link-quality determination test. The link is tested to determine whether the link quality is good enough to bring up network layer protocols.  
Network layer protocol phase - In this phase the PPP devices send NCP packets to choose and configure one or more network layer protocols, such as IP.  Once each of the chosen network layer protocols has been configured, packets from each network layer protocol can be sent over the link. If LCP closes the link, it informs the network layer protocols so that they can take appropriate action. The show interfaces command reveals the LCP and NCP states under PPP configuration. 

The PPP link remains configured for communications until either of the following:

LCP or NCP frames close the link 
An inactivity timer expires 
A user intervenes

10. Config PPP + CHAP on intf

Router#configure terminal 
hostname Left
username Right passwordf sameone
Router(config)#interface serial 0/0 
ip address
Router(config-if)#encapsulation ppp
ppp authentication CHAP

11. Config ISDN
conf t
isdn switch-type basic-ni
int bri 0/0
no shut
Router(config-if)#isdn spid1 51055540000001 5554000 
Router(config-if)#isdn spid2 51055540010001 5554001 

12. Config FR
conf t
int s0/0
ip address
encap frame-relay [cisco/ietf]
frame-relay lmi-type [cisco/ansi]
(frame-relay map ip [address] [DLCI]) //Static Route

13. IOS Commands

A Commands - action -  - apply -  - attach -  - auto-sync -  - B Commands - boot config -  - C Commands - cd -  - channel-group -  - channel-protocol -  - class-map -  - clear catalyst6000 traffic-meter -  - clear counters -  - clear interface gigabitethernet -  - clear interface vlan -  - clear ip access-template -  - clear ip auth-proxy watch-list -  - clear ip cef epoch full -  - clear ip cef inconsistency -  - clear ip flow stats -  - clear ip igmp group -  - clear lacp counters -  - clear mac-address-table dynamic -  - clear mls -  - clear mls exclude protocol -  - clear mls ip multicast statistics -  - clear mls nde counters -  - clear mls nde flow -  - clear mls qos -  - clear pagp -  - clear spanning-tree detected-protocol -  - clear vlan counters -  - copy /noverify -  - D Commands - debug adjacency -  - debug backup -  - debug callback -  - debug cca -  - debug condition interface -  - debug condition standby -  - debug condition vlan -  - debug earl -  - debug ehsa -  - debug entry -  - debug etherchnl -  - debug ethernet-interface -  - debug fastethernet -  - debug fm -  - debug gssapi -  - debug icc -  - debug iccshim -  - debug interface -  - debug ipc -  - debug ip rgmp -  - debug l2-mgr events -  - debug l3-mgr -  - debug local-ack -  - debug ltl -  - debug mergeapi -  - debug mls ip multicast -  - debug mls rp -  - debug monitor -  - debug msc -  - debug netdr -  - debug nvram -  - debug pagp -  - debug pf -  - debug pm -  - debug priority -  - debug qm -  - debug qm-sp -  - debug rpc -  - debug scp -  - debug smf updates -  - debug spanning-tree -  - debug spanning-tree backbonefast -  - debug spanning-tree switch -  - debug spanning-tree uplinkfast -  - debug sw-vlan -  - debug sw-vlan ifs -  - debug sw-vlan notification -  - debug sw-vlan vtp -  - debug tcam -  - debug udld -  - debug vacl -  - debug vlog -  - define interface-range -  - diagnostic level -  - disconnect qdm -  - do -  - dot1x default -  - dot1x max-req -  - dot1x multi-hosts -  - dot1x port-control -  - dot1x reauthentication -  - dot1x system-auth-control -  - dot1x timeout -  - duplex -  - E Commands - erase -  - errdisable detect cause -  - errdisable recovery -  - F Commands - fabric lcd-banner -  - fabric required -  - fabric switching-mode allow -  - file verify auto -  - flowcontrol -  - format -  - fsck -  - H Commands - hw-module reset -  - I Commands - instance -  - interface -  - interface port-channel -  - interface range -  - interface vlan -  - ip access-list hardware permit fragments -  - ip auth-proxy max-login-attempts -  - ip auth-proxy watch-list -  - ip cef table consistency-check -  - ip flow-cache entries -  - ip flow-export destination -  - ip flow-export source -  - ip flow-export version -  - ip igmp snooping -  - ip igmp snooping fast-leave -  - ip igmp snooping l2-entry-limit -  - ip igmp snooping last-member-query-interval -  - ip igmp snooping mrouter -  - ip igmp snooping querier -  - ip igmp snooping static -  - ip local-proxy-arp -  - ip multicast rpf backoff -  - ip multicast rpf interval -  - ip pim autorp listener -  - ip rgmp -  - ip route-cache flow -  - ip sticky-arp -  - ip verify unicast reverse-path -  - ip verify unicast source reachable-via -  - ip wccp redirect exclude in -  - ip wccp web-cache accelerated -  - L Commands - l2protocol-tunnel -  - l2protocol-tunnel cos -  - l2protocol-tunnel drop-threshold -  - l2protocol-tunnel shutdown-threshold -  - lacp port-priority -  - lacp system-priority -  - link debounce -  - M Commands - mac access-list extended -  - mac-address-table aging-time -  - mac-address-table static -  - mac-address-table unicast-flood -  - match -  - maxconns (real server configuration submode) -  - maximum-paths -  - mdix auto -  - mkdir disk0: -  - mls aclmerge algorithm -  - mls aging fast -  - mls aging long -  - mls aging normal -  - mls exclude protocol -  - mls flow -  - mls ip -  - mls ip cef arp-throttling -  - mls ip cef rate-limit -  - mls ip cef load-sharing full -  - mls ip directed-broadcast -  - mls ip inspect -  - mls ip multicast (global configuration mode) -  - mls ip multicast (interface configuration mode) -  - mls ip multicast connected -  - mls ip multicast consistency-check -  - mls ip multicast non-rpf-netflow (global configuration mode) -  - mls ip multicast non-rpf-netflow (interface configuration mode) -  - mls ip multicast stub -  - mls ip multicast threshold -  - mls ip pbr -  - mls ipx (interface configuration mode) -  - mls nde flow -  - mls nde interface -  - mls nde sender -  - mls netflow -  - mls netflow sampling -  - mls qos (global configuration mode) -  - mls qos (interface configuration mode) -  - mls qos aggregate-policer -  - mls qos bridged -  - mls qos channel-consistency -  - mls qos cos -  - mls qos flow-policing -  - mls qos map cos-dscp -  - mls qos map dscp-cos -  - mls qos map ip-prec-dscp -  - mls qos statistics-export (global configuration mode) -  - mls qos statistics-export (interface configuration mode) -  - mls qos statistics-export aggregate-policer -  - mls qos statistics-export class-map -  - mls qos statistics-export delimiter -  - mls qos statistics-export destination -  - mls qos statistics-export interval -  - mls qos trust -  - mls qos trust extend -  - mls qos vlan-based -  - mls rp ip (global configuration mode) -  - mls rp ip (interface configuration mode) -  - mls rp ipx (global configuration mode) -  - mls rp ipx (interface configuration mode) -  - mls rp management-interface -  - mls rp nde-address -  - mls rp vlan-id -  - mls rp vtp-domain -  - mls sampling -  - mode -  - monitor session -  - mpls l2transport route -  - mpls load-balance per-label -  - mtu -  - N Commands - name -  - net -  - P Commands - pagp learn-method -  - pagp port-priority -  - policy-map -  - port-channel load-balance -  - power enable -  - power inline -  - power redundancy-mode -  - ppp link -  - private-vlan -  - private-vlan mapping -  - private-vlan synchronize -  - protocol-filtering -  - R Commands - rcv-queue cos-map -  - rcv-queue queue-limit -  - rcv-queue random-detect -  - rcv-queue threshold -  - redundancy -  - redundancy force-switchover -  - reload -  - remote command -  - remote login -  - remote-span -  - reset -  - retry -  - revision -  - rmon alarm -  - rmon event -  - S Commands - scheduler allocate -  - service-policy input -  - session slot -  - set ip dscp -  - set ip precedence (policy-map) -  - show -  - shutdown vlan -  - snmp ifindex clear -  - snmp ifindex persist -  - snmp-server enable traps -  - snmp-server ifindex persist -  - spanning-tree backbonefast -  - spanning-tree bpdufilter -  - spanning-tree bpduguard -  - spanning-tree cost -  - spanning-tree etherchannel guard misconfig -  - spanning-tree extend system-id -  - spanning-tree guard -  - spanning-tree link-type -  - spanning-tree loopguard default -  - spanning-tree mode -  - spanning-tree mst -  - spanning-tree mst configuration -  - spanning-tree mst forward-time -  - spanning-tree mst hello-time -  - spanning-tree mst max-age -  - spanning-tree mst max-hops -  - spanning-tree mst root -  - spanning-tree pathcost method -  - spanning-tree portfast (interface configuration mode) -  - spanning-tree portfast bpduguard default -  - spanning-tree portfast bpdufilter default -  - spanning-tree port-priority -  - spanning-tree uplinkfast -  - spanning-tree vlan -  - speed -  - squeeze -  - stack-mib portname -  - standby delay minimum reload -  - standby track -  - standby use-bia -  - storm-control level -  - switchport -  - switchport access vlan -  - switchport autostate exclude -  - switchport capture -  - switchport capture allowed vlan -  - switchport mode -  - switchport port-security -  - switchport port-security aging time -  - switchport port-security mac-address -  - switchport port-security maximum -  - switchport port-security violation -  - switchport private-vlan host-association -  - switchport private-vlan mapping -  - switchport protocol -  - switchport trunk -  - switchport voice vlan -  - sync-restart-delay -  - system jumbomtu -  - Show Commands - show adjacency -  - show arp -  - show asic-version -  - show bootflash: -  - show bootvar -  - show cable-diagnostics prbs -  - show cable-diagnostics tdr -  - show catalyst6000 -  - show cdp neighbors -  - show class-map -  - show counters interface -  - show cwan -  - show diagnostic -  - show dot1q-tunnel -  - show dot1x -  - show environment alarm -  - show environment status -  - show environment temperature -  - show eobc -  - show errdisable detect -  - show errdisable recovery -  - show etherchannel -  - show fabric -  - show fm features -  - show fm inband-counters -  - show fm insp -  - show fm interface -  - show fm reflexive -  - show fm summary -  - show fm vlan -  - show icc -  - show idprom -  - show interfaces -  - show interfaces capabilities -  - show interfaces counters -  - show interfaces debounce -  - show interfaces description -  - show interfaces flowcontrol -  - show interfaces private-vlan mapping -  - show interfaces status -  - show interfaces summary -  - show interfaces switchport -  - show interfaces trunk -  - show ip auth-proxy watch-list -  - show ip cache flow -  - show ip cef epoch -  - show ip cef inconsistency -  - show ip cef summary -  - show ip cef vlan -  - show ip igmp interface -  - show ip igmp snooping mrouter -  - show ip mroute -  - show ip rpf events -  - show ip wccp web-cache detail -  - show ipc -  - show l2protocol-tunnel -  - show l3-mgr -  - show lacp -  - show mac-address-table -  - show mls asic -  - show mls cef -  - show mls cef adjacency -  - show mls cef exact-route -  - show mls cef hardware -  - show mls cef ip -  - show mls cef ipx -  - show mls cef logging -  - show mls cef mac -  - show mls cef statistics -  - show mls cef summary -  - show mls ip -  - show mls ip multicast -  - show mls ip statistics -  - show mls ipx -  - show mls nde -  - show mls netflow -  - show mls netflow ip -  - show mls netflow ipx -  - show mls qos -  - show mls qos aggregate policer -  - show mls qos statistics-export info -  - show mls sampling -  - show mls statistics -  - show mls table-contention -  - show module -  - show monitor session -  - show mpls l2transport vc -  - show mpls ttfib -  - show msfc -  - show pagp -  - show platform -  - show policy-map -  - show policy-map interface -  - show port-security -  - show power -  - show protocol-filtering -  - show qdm status -  - show qm-sp port-data -  - show queueing interface -  - show redundancy -  - show rom-monitor -  - show rpc -  - show running-config -  - show scp -  - show slot0: -  - show spanning-tree -  - show spanning-tree mst -  - show standby delay -  - show sup-bootflash -  - show tcam counts -  - show tcam interface -  - show tech-support -  - show udld -  - show vlan -  - show vlan access-log -  - show vlan access-map -  - show vlan counters -  - show vlan dot1q tag native -  - show vlan filter -  - show vlan internal usage -  - show vlan mapping -  - show vlan private-vlan -  - show vlan remote-span -  - show vlans -  - show vtp -  - T Commands - tcam priority -  - test cable-diagnostics -  - time-range -  - U Commands - udld -  - udld port -  - udld reset -  - upgrade rom-monitor -  - username -  - V Commands - verify -  - vlan (config-VLAN submode) -  - vlan (global configuration mode) -  - vlan (VLAN configuration submode) -  - vlan access-log -  - vlan access-map -  - vlan database -  - vlan dot1q tag native -  - vlan filter -  - vlan internal allocation policy -  - vlan mapping -  - vtp -  - W Commands - wrr-queue bandwidth -  - wrr-queue cos-map -  - wrr-queue queue-limit -  - wrr-queue random-detect -  - wrr-queue threshold