1. IT246 introduction to networkS
Prof. Alfred J Bird, Ph.D., NBCT

2. What is the Difference Between a LAN and a WAN?
LAN –Local Area Network
In most cases now, these are Ethernet Networks
Interconnect sites that are close to each other, for example in the same building.
WAN – Wide Area Network
Generally use the TELCO network for communications
Interconnect sites that are geographically distributed

3. Data Rates DS-0 64kbps (56kbps) T1 (DS-1) 1.544Mbsp
T2 (DS-2) Mbps
T3 (DS-3) Mbps
T4 (DS-4) Mbps
E Mbps
E Mbps

4. What Really Happens!

5. Important Terms Multiplexed – Combining data packets for transport
Point of Presence (POP) – The point where the customer connects the network data traffic to the communications carrier
Line of Demarcation – The point where ownership of the communications equipment changes from the communications carrier to the user
CSU/DSU – The Channel Service Unit / Data Service Unit

6. Placement of the CSU/DSU

7. CSU / DSU Alarms
Red Alarm – A local equipment alarm that indicates that the incoming signal has been corruptes
Yellow Alarm – Indicates that a failure in the link has been detected
Blue Alarm – Indicates a total loss of incoming signal

8. Important Terms HDLC – High Level Data Link Control
High level data link control, a synchronous proprietary protocol
PPP – Point to Point Protocol
Generally used with modems
Data Encapsulation – The data is properly packages for transport over a serial communications line

9. Important Terms
V.44/V.34 – The standard for all analog modem connections with a maximum data rate of 34 kbps
V.92/V.90 – The standard for a combination of analog and digital modem connections with a maximum data rate of 56kbps
Asymmetric Operation – Describes the modem operation where the data transfer rate to and from the service provider differs

10. Cable Modems
Capitalize on the high-bandwidth network of a cable provider two-way to deliver high speed data
Data rates can range up to (and maybe greater than) 50Mbps
Potential of collisions problems
Currently using ethernet protocols

11. FIOS Fiber Optical Network Not available everywhere
Performance equal to cable modem systems

12. DSL DSL – Digital Subscriber Line
DSL uses a point to point technology
Sends signals over copper telephone lines
Limited ranges
xDSL – generic term for many forms of DSL
ADSL – Asymmetric DSL - <18,000ft
SDSL – Symmetric DSL - < 10,000ft
Many other (see the text)

13. DSL

14. Remote Access Server RAS - Remote Access Server
The last piece needed to gain access to the network
Provided by the POTS (Plain Old Telephone Service) or the cable modem or other types of connections

15. Metro Ethernet / Carrier Ethernet
Why not use Ethernet protocols for a WAN?
Ethernet now has speeds up to 10Gbps
IT has been doing a lot of engineering and development work on Ethernet equipment and protocols.
Three (3) types of technologies defined by the MEF (Metro Ethernet Forum)
Ethernet Line Service (E-Line)
Point to point service
Ethernet ELAN Service (E-LAN)
Multipoint to multipoint service
Ethernet Tree Service (E-Tree)
Point to multipoint service

16. Ethernet Line Service (E-Line)
Point to point connection
Similar to a dedicated leased line, frame relay or ATM
From the customer it appears everyone is on the same LAN

17. Ethernet LAN Service (E-LAN)
Provides connectivity to two or more subscribers
It appears to the customer that everyone on on the same LAN

18. Ethernet Tree Service (E-TREE)
Like a hub and spoke service. Called a root and leaf environment
Customer sites cannot exchange traffic with each other

19. Important Terms CIR - (Committed Information Rate)
Bandwidth the network must deliver
CBR – (Committed Burst Size)
The traffic size that is allowed to burst
EIR – (Excess Information Rate)
Average size in bps used to allow traffic greater that the CIR when the network is not busy
EBS – (Excess Burst Size)
Burstable size allowed when the when the traffic is in the EIR mode

20. Network Services – DHCP & DNS
DHCP – Dynamic Host Configuration Protocol
Extension of BOOTP (Bootstrap Protocol)
Way to assign IP addresses to a networked computer
DNS – Domain Name Service
Way to match up a URL to an IP

21. DHCP
The networked computer issues a request using a broadcast to find a DHCP server
The DHCP server sends an IP to the networked computer
Will also send other info such as lease time, gateway, subnet mask, etc.

22. DNS Forward Domain Name Service Reverse Domain Name Service
Translation of a URL (name) to a IP address
Reverse Domain Name Service
Translation of an IP address to an URL (name)

23. Important Terms IANA – Internet Assigned Name Authority
ICANN – Internet Corporation of Assigned Names and Numbers
Domain Registers
A organization that is authorized to register Internet domain names