11/22/2013 1
Week3-4 Point-to-Point, LAN, WAN Review 11/22/2013 2
What will you learn? Representatives for Point-to-Point Network LAN Wired Ethernet Wireless Ethernet WAN ATM (Asynchronous Transfer Mode) 11/22/2013 3
IP model & its underlying hardware network @ISP @university @home @ISP Application Application Transport Transport Internet Internet Internet Internet P-to-P P-to-P WAN3 WAN3 LAN1 LAN1 11/22/2013 4
Point-to-Point Network Any direct connection between two computers Dedicated line between two routers Dialup connection (from telephone company) On-demand basis, low speed Leased line (from telephone company) Permanent basis, High-speed xdsl Link-level protocol required for framing PPP is popular TCP/IP views as an independent physical network Containing only 2 computers at the both end 11/22/2013 5 Note: some experts argue the terminology is incorrect because a connection limited to two endpoints is not technically a network
Point-to-point network protocol Layer 1 s modem Internet Internet P-to-P network PPP Leased line, Dial-up, xdsl Layer 2: framing Layer 1: bit transmission PPP Leased line, Dial-up, xdsl P-to-P network Most of point-to-point network uses PPP protocol Link detection, authentication, framing Layer 1 will be any selected link options providing Direct bit transmission 11/22/2013 6 Note: practical ADSL implementation is more complicated
PPP protocol LCP: detect/setup/configure/terminate (layer 1)link AP: exchange authentication info NCP: configure parameter/type of Network layer protocol 11/22/2013 7
PPP Frame Format Frame is often written in blocks of 32 bits. It is easily to present on a paper 11/22/2013 8
PPP state transition diagram 11/22/2013 9
PPP connection example 11/22/2013 10
PPP connection example (cont.) 11/22/2013 11
Local Area Network: Ethernet Extremely popular Can run over Copper (twisted pair: UTP, STP) Optical fiber (single mode, multi-mode) wireless IEEE standard is 802.x Wired Ethernet (802.3) Four generations 10Base-T (Standard Ethernet)operates at 10 Mbps 100Base-T (Fast Ethernet) operates at 100 Mbps 1000Base-T (Gigabit Ethernet) operates at 1 Gbps 10 Gigabit Ethernet operates at 10 Gbps Shared medium with MAC protocol=> CSMA/CD Wireless Ethernet (802.11) Shared frequency with MAC protocol=> CSMA/CA 11/22/2013 12
Ethernet network protocol Ethernet NIC Internet Internet Ethernet network LLC MAC Physical link options Layer 2: framing, MAC Layer 1: bit transmission LLC MAC Physical link options Ethernet network Layer 2 is divided into 2 sublayers LLC => frame format MAC => medium access method Layer 1 will be Ethernet link options providing Direct bit transmission Wired, wireless 11/22/2013 13
Wired Ethernet (802.3) Frame Format Header format fixed (Destination, Source, Type fields) Frame data size can vary from packet to packet Maximum 1500 octets, Minimum 46 Octets Address is represented by Hexadecimal notation 11/22/2013 14 E.g., 02:07:01:00:27:BA Preamble, SFD and CRC removed by framer hardware (NIC) before frame stored in computer s memory
Example Ethernet Frame In Memory Octet shown in hexadecimal Destination is 02:07:01:00:27:ba Source is 08:00:2b:0d:44:a7 Frame type is 08.00 (IP) 11/22/2013 15
Standard Ethernet 11/22/2013 16
Standard Ethernet (Cont.) 11/22/2013 17
Ethernet MAC: CSMA/CD 11/22/2013 18
Ethernet MAC: CSMA/CD (cont.) 11/22/2013 19
Manchester encoding 11/22/2013 20
Changes in Standard Ethernet Standard Ethernet => Bridged Ethernet => Switched Ethernet Then, Fast Ethernet, Gigabit Ethernet, Ten- Gigabit Ethernet 11/22/2013 21 Bandwidth Sharing on Ethernet
Bridged Ethernet Collision Domain => area in which collision may occur Broadcasting Domain => area in which broadcast frame propagates Bridge filters out frames whose destination address is not for each side 11/22/2013 22
Frame filtering in Bridge 11/22/2013 23
Switched Ethernet Implement dynamic bridge in which only a computer at each port belongs to its own collision domain No sharing of bandwidth in case of unicast 11/22/2013 24
Fast Ethernet As 802.3u, for 100 Mbps speed 11/22/2013 25 100 meters 100 meters 100 meters
Gigabit Ethernet As 802.3z, for 1000 Mbps speed 550 meters 5000 meters 25 meters 100 meters 11/22/2013 26
10 Gigabit Ethernet Target for the Backbone LAN 11/22/2013 27
Extending LAN coverage Using Repeater Repeat all signals from one LAN to the other Ethernet HUB Using Bridge Selective repeat frames from one LAN to the other Selective repeat => based on frame s (hardware) address Ethernet (Layer-2) SWITCH 11/22/2013 28
Collision & Broadcast Domain HUB: same Collision & broadcast domain L2 SW: Collision domain covers only at the SW port, while broadcast domain covers all segments 11/22/2013 29
VLAN implemented by L2-SW VLAN => the LAN configured by software, not by physical wiring 11/22/2013 30
Example of Wireless Standard 11/22/2013 31
IEEE 802.11 Normal Station: mobile station Stationary station: AP 11/22/2013 32
802.11 Extended Service Set Distribution System is usually a wired LAN 11/22/2013 33
Protocol Stack of 802.11 PCF is optional protocol (used by AP for time sensitive transmission): Polling DCF is mandatory: CSMA/CA 11/22/2013 34
MAC Frame Structure WEP:Wired Equivalent Privacy 11/22/2013 35
Addressing Mechanism 11/22/2013 36
Wide Area Network: ATM Provide high-speed connection-oriented service (using virtual circuit switching technology) Each connection is identified by the assigned VPI/VCI Each end point is identified by ATM address (come with ATM NIC) Basic transferring packet is called cell 53 octets fixed size (5 octets for header) User data will be divided by AAL method before being filled into ATM cell 11/22/2013 37
ATM network protocol ATM NIC ATM network Internet AAL ATM Physical link options Data conversion layer ATM ATM PHYPHY PHYPHY Internet AAL ATM Physical link options ATM network Layer 3 11/22/2013 38 AAL layer => data conversion Layer 2 (OSI layer 3 function) ATM layer => cell switching Layer 1 will be high speed link options providing Direct bit transmission Mostly, optical fiber Bit transmission Cell switching
Virtual Circuit Switched Concept A special type of packet switch Connection establishment is needed To reserve resource Short (locally unique) value is assigned as one-time address dynamically, it will last within this session=> called virtual connection (circuit) identifier Routing process is the same as packet switching, excepting that it uses local one-time address (VCI) Very fast routing Connection release is needed To release resource Guarantee QoS (Quality of Service) 11/22/2013 39
Virtual Circuit Switched (Con Request) Need connection establishment to assign VCI 11/22/2013 40
Virtual Circuit Switched Model (con Ack) Need connection establishment to assign VCI 11/22/2013 41
Virtual Circuit Switched (Transfer) Need connection establishment to assign VCI 11/22/2013 42
Delay in Virtual Circuit Switched 11/22/2013 43
ATM cell switching 11/22/2013 44 ATM uses two-level virtual connection Identifier VPI VCI
ATM cell format 5 bytes 48 bytes 11/22/2013 45 Between end-computer and ATM switch Between ATM swtich and ATM switch
AAL5: Filling Data from computer into ATM cell 11/22/2013 46 Note: to transfer IP packet over ATM network, The AAL5 is often used
ATM used in LAN ATM switch will physically look like Ethernet switch Typical usage: LANE (LAN Emulation) software will be used to make the ATM behave as the Ethernet in LAN environment 11/22/2013 47
P-to-P Special case: ADSL Asymmetric Digital Subscriber line Subscriber line Copper wire (UTP3) from nearest telephone office to your home Called local loop, subscriber loop or last mile Digital Digital data or binary data Asymmetric Different data rates in uploading/downloading direction To utilize existing local loop line for high-speed digital data transmission 11/22/2013 48
@home Typical ADSL Point-to-point system Your home Ethernet splitter Local loop (UTP3) Telephone company ATM ISP company @ISP IP PPP PPPoE ADSL router (bridged mode) PPPoEPPPoA DSLAM (ADSL modem @telephone company) IP PPP PPPoA Ethernet Ethernet AAL5 ATM ATM ATM ATM ATM AAL5 ATM PPPoE => PPP over Ethernet an extension of PPP defined how PPP frame is sent over Ethernet frame PPPoA => PPP over ATM 11/22/2013 49 ASDL PHYSICAL LAYER extension of PPP defined how PPP frame is sent over ATM cells
ADSL System Architecture 11/22/2013 50 @ home ADSL router: combined IP router+ ADSL modem @ Central office DSLAM: Digital subscriber line access multiplexer DSLAM will connect to ISP s router via WAN
ADSL Physical Layer Shared UTP3 with telephone signal Telephone signal (voice): 0-4KHz ADSL signal Upload: 26kHz-108kHz Download: 138kHz-1104kHz Splitter splits TEL & ADSL signal by low-pass & high-pass filter ADSL model Employs DMT modulation technique 11/22/2013 51
DMT in ADSL 11/22/2013 52 DMT is equivalent to OFDM in wireless system