Routing Protocol and WAN Protocol

in CCNA & CCENT
Hi,
i am really confused with routing protocol and WAN technologies
. i know we need WAN protocal (ppp or hdlc) to encapsulate the data to be transfered through the WAN.
what is ISDN?? why we stilll need encapsulations(ppp , hdlc etc) for isdn? isn't that ISDN is WAN Protocol ? maybe i got wrong concept on isdn.
frame relay, do i need an encapsulation for frame relay? please give me a little bit explanation on these topic thanks
i am really confused with routing protocol and WAN technologies

what is ISDN?? why we stilll need encapsulations(ppp , hdlc etc) for isdn? isn't that ISDN is WAN Protocol ? maybe i got wrong concept on isdn.
frame relay, do i need an encapsulation for frame relay? please give me a little bit explanation on these topic thanks
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Comments
A routing protocol is a method of determining the best route to send data through/accross a network, such as RIP or OSPF.
ISDN is an example of a circuit switching technology, its medium that data can travel accross, the data itself still needs encapsulating.
Frame Relay is a packet switching method which runs over ISDN etc this data also needs an encapulation method applied.
Maybe some of the other guys could correct me/point you in the right direction?
i have another question, say 2 LANs (network 1 and 2) and 1 router. the router is use to route between these 2 network. in this case, do you still need encapsulation(ppp etc) for the data to pass from network 1 to network 2?
To put it another way, you dont need to manually apply any encapsulation or put any commands into your router for your network to function
yes - the encapsulation is ETHERNET.
WAN technologies use different methods of encapsulation to transport data across.
In your LAN you can have a mix of encapsulation methods, like if you connect two routers by the serial interface, you are using HDLC there. So HDLC is just and encapsulation methods and not a WAN technology.
ISDN is like say DSL, is just another way to connect to the ISP, each with an encapsulation method.
Hope this can help a little bit.
that's very clear. so isdn, frame relay is the WAN Technology for connecting to isp or to remote lans. and PPP, HDLC etc is the encapsulation for the data that travel through the WAN.
Thanks
i will book the exam for mid jan next year. i have to re-read those WAN technologies. that's just too hard to stay in my head. Have nice X'mas