Dial Services

Dial-On-Demand: WAN link is established between 2 routers only when the need arises to send data. Reduces cost

Dial Backup: backup line is established when primary line fails. Backup line inherits circuit information of the primary line

Bandwidth-on-Demand: Allows aggregation of WAN links into a single circuit, with each link being used when needed (brought up/taken down based on user-defined utilization criteria)


Dial Services is comprised of 3 basic components:
- Logical Lines: are created when building a pool, each line has one reference to the pool it is associated with (backup/demand/bandwidth-pool). Lines represent physical layer in OSI model.

- Circuit Definitions: when creating individual dial circuits, the circuit definition ties all the layers together.

- Upper Layer Interfaces: identify the networking protocols and services that are used over the circuit:
--- IP
--- IPX
--- AT
--- Bridging


ISDN

- Better line speed
- Digital Signal
- Quick Call Setup
- Flexibilty

(B Channel = Bearer Channel)

BRI service: provides up to 2 B Channels.

PRI service: provides up to 23->30 B Channels.

Both services can combine channels or lines to create a bigger pipe.

Extra channel for call setup/teardown and keepalive: D Channel

BRI: 1 D Channel @ 16Kb/s
PRI: 1 D Channel @ 64Kb/s

PRI Multirate allows grouping of B Channels in multiples of 64Kb/s to dynamically allocate bandwidth between 128Kb/s to 1472Kb/s.
Multirate is usefull as backup for a high speed WAN line.