Transcript Review, Mobitex - Data Link Layer , Cont

Southern Methodist University Fall 2003
EETS 8316/NTU CC745-N
Wireless Networks
Lecture 7: Mobile Data, Part II
Instructor: Jila Seraj
email: [email protected]
http://www.engr.smu.edu/~jseraj/
tel: 214-505-6303
EETS 8316/NTU TC 745, Fall 2003
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#1
Session Outline
Review of last week
More GPRS
LAN Primer
IP Primer
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#2
Review, Aloha
Aloha is a wireless network designed in
Hawaii and thus the name Aloha
It was experimented in many way to find a
good solution for wireless communication
The system consisted of wireless devices
communicating together using a
communication satellite
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#3
Review, Aloha
Aloha
—Stations starts sending when they have
something to send
—Pure Aloha, no contention resolution, relies
on timed-out acks, max throughput
approximately 18%
—Slotted Aloha, no contention resolution,
relies on timed-out acks, only can start
sending in the beginning of a slot, max
through put approximately 36%
EETS 8316/NTU TC 745, Fall 2003
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#4
Review, Pure ALOHA Throughput
— In equilibrium, throughput (rate of successfully
transmitted frames) = rate of new transmissions, S
S = GP0
where P0 = probability of successful transmission
(no collision)
— P0 depends on “vulnerable interval” for frame, 2T
- transmission attempt at time 0
frame A
- collision if starts in interval (-T,0)
frame B
frame C
-T
0
EETS 8316/NTU TC 745, Fall 2003
- collision if starts in interval (0,T)
time
T
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#5
Review, Pure ALOHA
P0 = Pr(no other frame in 2T interval)
— Assume total number of frames in any interval t is
also Poisson distributed, with average G:
Pr(k transmissions in t) = (Gt)ke-Gt/k!
then P0 = e-2G
— By substitution, throughput is
S = GP0 = Ge-2G
— This is maximum at G = 0.5, where S = 1/2e =
0.184 (frames per interval T)
• Pure ALOHA achieves low throughput
EETS 8316/NTU TC 745, Fall 2003
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#6
Review, Slotted ALOHA
Slotted ALOHA is a modification to increase
efficiency
— Time is divided into time slots = transmission time
of a frame, T
— All stations are synchronized (e.g., by periodic
synchronization pulse)
— Any station with data must wait until next time slot
to transmit
— Any time slot with two or more frames results in a
collision and loss of all frames – retransmitted after
a random time
EETS 8316/NTU TC 745, Fall 2003
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#7
Review, Slotted ALOHA
“Vulnerable interval” is reduced by factor of
2 to just T
-T
frame A
- transmission attempt at time 0
frame B
- collision if frame B was ready in
interval (-T,0)
0
EETS 8316/NTU TC 745, Fall 2003
time
T
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#8
Review, Slotted ALOHA
Throughput
P0 = Pr(no frames ready in previous time slot) = e-G
— Now throughput is
S = GP0 = Ge-G
— This is maximum at G = 1, where S = 1/e = 0.368
(frames per interval T)
• Slotted ALOHA doubles throughput of pure ALOHA
EETS 8316/NTU TC 745, Fall 2003
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#9
Primer: Slotted ALOHA
Note that throughput is never very high
Also, at high loads, throughput goes to 0 –
a general characteristic of networks with
shared resources
— Number of empty time slots and successful slots
decrease, number of collisions increase
— Average number of retransmissions per frame
increases
— Average delay (from first transmission attempt to
successful transmission) increases
EETS 8316/NTU TC 745, Fall 2003
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#10
Review, CSMA
Carrier Sense Multiple Access =
CSMA
Sense the presence of carrier, sense the
channel is free, send data, wait for Ack, resend if timed-out, if busy back off and try
again. Max throughput 60%
EETS 8316/NTU TC 745, Fall 2003
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#11
Review, CSMA
Family of CSMA protocols defined by rules
for backing off with varying degrees of
persistence
— 1-persistent CSMA: stations are most persistent
— P-persistent CSMA: persistence increases with
value of p
— Non-persistent CSMA: stations are not that
persistent
EETS 8316/NTU TC 745, Fall 2003
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#12
Review, CSMA (Cont)
Carrier Sense Multiple Access-Collision
Detection (CSMA-CD)
— Send when carrier is free, listen to detect collision.
— CSMA-CA is the method of choice
Carrier Sense Multiple Access-Collision
Avoidance (CSMA-CA)
— Uses two messages before transmission, RequestTo-Send (RTS) and Clear-To-Send (CTS) .
— Method of choice for wireless LAN
EETS 8316/NTU TC 745, Fall 2003
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#13
Review, Mobile Data
2 main options for wireless packet data:
—High speed wireless LANs (e.g., 802.11)
—Low speed wide area services
• Mobitex/RAM Mobile Data
• CDPD (cellular digital packet data)
• GPRS (general packet radio service)
• ARDIS (advanced radio data information
services)
EETS 8316/NTU TC 745, Fall 2003
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#14
Review, Mobile Data , Cont...
ERMES (European Radio Message System)
was standardized by ETSI early 1980.
Originated by Swedish Telecom (now Telia
Mobitel) as private mobile alarm system for
field personnel
Development Continued by MOA (Mobitex
Operators Association) and Ericsson
Mobile Communications
http://www.ericsson.com/wireless/products/
mobsys/mobitex/mobitex.shtml)
EETS 8316/NTU TC 745, Fall 2003
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#15
Review, Mobitex/RAM Mobile Data
Mobitex - widely accepted de facto standard
for wireless packet data
—Developed by Swedish Telecom (now Telia
Mobitel) as private mobile alarm system for
field personnel
—Development Continued by MOA (Mobitex
Operators Association) and Ericsson
—1986 Commercial operation in Sweden
—Now widely deployed in Europe, US,
Australia
EETS 8316/NTU TC 745, Fall 2003
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#16
Review, Mobitex , Cont...
1986 Commercial operation in Sweden
Now widely deployed in Europe, US,
Australia
In US, RAM Mobile Data, a joint venture
between RAM broadcasting and Cingular.
http://www.cingular.com/business/mobitex_
map
EETS 8316/NTU TC 745, Fall 2003
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#17
Review, Mobitex, Major features, Cont...
Major features
—Seamless roaming
—Store and forward of messages
—Dependability above 99.99%
—Interoperability and many connectivity
options
—Capacity to support millions of subscribers
—Security against eavesdropping
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#18
Review, Mobitex, Major features, Cont...
Major features
—Packet switching occurs at lowest level of
system hierarchy - relieves backbone traffic
—Packet multicasting (to multiple recipients) is
handled by network
—Closed User Group (CUG) feature
—Frequency depends of the country, 900
MHZ in US and 450 in most others.
EETS 8316/NTU TC 745, Fall 2003
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#19
Review, Mobitex - Architecture
NCC
NCC: network
Control center
Main
exchange
Regional
switch
Local
switch
Regional
switch
Local
switch
Base stations use 1-4
frequencies each 8 kb/s
FEP
EETS 8316/NTU TC 745, Fall 2003
Local switch covers a
service
area, each with 10-30
frequency pairs
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#20
Review, Mobitex - Architecture , Cont...
Network Control Center (NCC), provides
network management functions
Main Exchange and Regional Switch have
basically the same function, but they reside
on different level of network hierarchy.
—Packet switching
—Protocol handling (X.25 and HDLC)
—Subscriber data for nodes below
—Multiple connection to other switches
—Alternate routing
EETS 8316/NTU TC 745, Fall 2003
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#21
Review, Mobitex - Architecture , Cont...
Local Switches, similar to regional
switches. Also handles
—Communication with base stations
—Connection to host computers via FEP
(Front-End-Processor)
FEP provides
—Protocol conversion to hosts supporting
X.25, TCP/IP, and SNA
—Convert connectionless protocol to
connection oriented protocol.
EETS 8316/NTU TC 745, Fall 2003
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#22
Review, Mobitex, protocol architecture
Applications
4-7 Applications
3
2
1
MPAK
MPAK
MPAK
MASC
MASC
RS232
RS232 GMSK
Mobile
EETS 8316/NTU TC 745, Fall 2003
ROSI
ROSI HDLC
GMSK X.21
Base
Station
Radio
modem
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MPAK
HDLC
X.25
X.21 X.21
Local
switch
MPAK
X.25
X.21
Server
#23
Review, Mobitex - Network Layer
Network layer packet = MPAK (Mobitex
PAcKet)
—User data, segmented into packets of
maximum 512 bytes
—Alert messages (high priority)
—Network layer signaling, e.g., login/logout
requests
EETS 8316/NTU TC 745, Fall 2003
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#24
Review, Mobitex - Network Layer , Cont...
MPAK header Contains
—Identification of application that generated
packet
—Class (significance)
—Type (priority)
—Whether can be stored in recipient’s mailbox
(temporary storage) if cannot be delivered
immediately
EETS 8316/NTU TC 745, Fall 2003
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#25
Review, Mobitex - Data Link Layer
Data link layer protocol is MASC (Mobitex
Asynchronous Communication)
MPAK delivers user packets plus
addressing and network data to MASC
Data link layer functions
—Selection of most suitable base station
—Retransmissions of frames lost on the radio
channel (stop-and-wait ARQ)
—Channel access procedure - variation of
slotted ALOHA
EETS 8316/NTU TC 745, Fall 2003
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#26
Review, Mobitex - Data Link Layer , Cont...
—Base station initiates a Contention cycle by
sending a FREE frame downlink
—Mobile stations can Contend for number of
free timeslots by choosing a random slot
and transmitting during that slot
—If mobile has more data than fits in a time
slot, it can start by sending a short access
request message
—Base station grants access to requesting
mobile stations after a free cycle
EETS 8316/NTU TC 745, Fall 2003
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#27
Review, Mobitex - Data Link Layer , Cont...
ROSI (Radio Signaling), takes care of
transmission towards Mobitex
infrastructure
GMSK (Gaussian Minimum Shift Keying)
X.21 and X.25 are the packet data
communication protocols used for many
years. Good for connectionless short
bursts of data.
EETS 8316/NTU TC 745, Fall 2003
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#28
Review, Mobitex - Radio Interface , Cont...
—Data link also handles channel access
procedure - variation of slotted ALOHA
• Base station broadcasts a FREE frame
indicating a free cycle, including number
and length of time slots in the free cycle
• Mobile terminal chooses a random
timeslot in next free cycle and transmits
its frame then
EETS 8316/NTU TC 745, Fall 2003
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#29
Review, Mobitex - common functions
Requires subscription
—individual
—groups of terminals
—host computer
—groups of host computers
Security
—Password based
—ESN
—CUG (Closed User Group)
EETS 8316/NTU TC 745, Fall 2003
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#30
Review, Mobitex - Mobility
Mobiles monitor and evaluate signals from
other base stations
At power-up, mobile tries to register with
the last base station in its memory, if
possible
Base station provides necessary
information, such as acceptable signal
strength, neighbor list,etc periodically.
EETS 8316/NTU TC 745, Fall 2003
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#31
Review, CDPD
Cellular digital packet data (CDPD):
connectionless packet-switched data
designed to work with an analog cellular
system (e.g., AMPS)
—Originated by IBM as packet-switching
overlay to analog cellular system, early
1990s developed by CDPD Forum, now
developed by Wireless Data Forum
—Overlay system uses unused bandwidth in
cellular system and existing AMPS functions
and capabilities
EETS 8316/NTU TC 745, Fall 2003
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#32
Review, CDPD , Cont...
CDPD is a value added system. Other users
do not need to be aware of its presence in
the network. This has implications:
CDPD transmission must not interfere with
transmission of other services
No dedicated bandwidth, uses only idle
time between users, channel-hop
No dedicated Control channel, all Control is
in-band.
EETS 8316/NTU TC 745, Fall 2003
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#33
Review, CDPD , Cont...
CDPD is transparent to voice system
—To avoid collisions with voice calls, CDPD
uses channel hopping when antenna
detects a power ramp-up (indicating
initiation of voice traffic)
—Base station closes current transmission
channel within 40 msec and new idle
channel is chosen to hop to
EETS 8316/NTU TC 745, Fall 2003
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#34
Review, CDPD , Cont...
CDPD is transparent to voice system
—New channel may or may not be announced
before old channel closed
• If not announced, mobile terminal must
hunt around set of potential CDPD
channels to find new one
EETS 8316/NTU TC 745, Fall 2003
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#35
Review, CDPD - Network Architecture
Internet or other
networks
IS
IS
MD-IS
Intermediate systems = generic
packet switches in backbone
network
IS
Mobile data intermediate
systems = packet switches
with mobility management
capabilities
MD-IS
Mobile data base station =
base station
EETS 8316/NTU TC 745, Fall 2003
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#36
Review, CDPD - Network Architecture , Cont...
Mobile end system (MES): may be handheld
PDA to laptop to terminal
—Stationary or mobile, but treated as
potentially mobile
—Network Continually tracks location to
ensure that packets are delivered even if
physical location changes
—May sleep - messages are then queued in
network
EETS 8316/NTU TC 745, Fall 2003
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#37
Review, CDPD - Network Architecture , Cont...
Mobile data base station (MDBS): mobile
data link relay
—Supports CDPD MAC and data link
protocols across radio interface
—Handles radio channel allocation,
interoperation of channels between CDPD
and voice calls, tracks busy/idle status of
channels
—Often co-located with AMPS base stations
(shares AMPS antenna)
EETS 8316/NTU TC 745, Fall 2003
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#38
Review, CDPD - Network Architecture , Cont...
Mobile data intermediate system (MD-IS)
—Mobility management: location tracking,
registration, authentication, encryption
• Exchange location information by CDPDspecific mobile network location protocol
(MNLP)
• “Mobile home function” (MHF) in home
network maintains current location info
for a mobile end system and forwards
packets
EETS 8316/NTU TC 745, Fall 2003
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#39
Review, CDPD - Network Architecture , Cont...
Mobile data intermediate system (MD-IS)
• “Mobile serving function” (MSF) in visited
network maintains info for visiting mobile
end systems in its area (through
registration process)
—Accounting and billing (based on usage)
EETS 8316/NTU TC 745, Fall 2003
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#40
Review, CDPD , Cont...
CDPD network layer
—Internet protocol (IP and mobile IP) and
connectionless network protocol (CLNP,
OSI’s equivalent of IP) are supported
—Backbone network of intermediate systems
(IS) provides connectionless packet routing
• IS can be off-the-shelf IP or CLNP
routers
EETS 8316/NTU TC 745, Fall 2003
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#41
GPRS - Network Architecture
Internet or other
networks
HLR
SGSN
MSC/
VLR
GGSN
Gateway GSN = packet switch
interworks with other networks
SGSN
Serving GPRS support node
= packet switch with mobility
management capabilities
BSC/PCU
GPRS makes use of existing
GSM base stations
EETS 8316/NTU TC 745, Fall 2003
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#42
GPRS , Cont...
GSM Release’97 introduced general packet
radio service (GPRS) for bursty data
Make use of existing GSM network
equipment and functions
In Contrast to CDPD, it is integrated into
GSM, i.e. dedicated Control channel and
data channel.
Requires two new network element, GGSN
and SGSN
EETS 8316/NTU TC 745, Fall 2003
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#43
GPRS , Cont...
SGSN = Serving GPRS Support Node
—Ciphering
—Authentication, IMEI check
—Mobility Management
—Logical Link Management towards mobile
station
—Packet routing and transfer
—Connection to HLR, MSC, BSC and SMSMC
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GPRS , Cont...
GGSN = Gateway GPRS Support Node
— External interfaces
— Routing
GPRS register maintains GPRS subscriber
data and routing information. Normally it is
integrated in GSM HLR
PCU (Packet Control Until) is collocated
with BSC.
EETS 8316/NTU TC 745, Fall 2003
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#45
GPRS , Cont...
Three class of mobile terminals
—Class A: Operates GPRS and Circuit
switched service simultaneously
—Class B: Monitors the Control channels of
GPRS and GSM simultaneously but can
operate one set of services at a time
—Class C: Only CS or GPRS capable.
EETS 8316/NTU TC 745, Fall 2003
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#46
GPRS , Cont...
For mobility management a new concept is
defined, Routing Area
RAI = MCC +MNC + LAC + RAC
EETS 8316/NTU TC 745, Fall 2003
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#47
GPRS Features
Packet data can use up to 8 timeslots to
provide 115.2 kb/s
Suitable for bursty data such as web
browsing
EETS 8316/NTU TC 745, Fall 2003
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#48
GPRS Interfaces
EETS 8316/NTU TC 745, Fall 2003
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GPRS – Data Connection
GPRS data connection starts with Attach
and ends with Detach.
Attach is the phase when the mobile
informs the network of its intention to
create a data connection
At conclusion of Attach, SGSN is ready to
set up data services on behalf of the mobile
user.
EETS 8316/NTU TC 745, Fall 2003
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#50
GPRS – Data Connection, Cont…
Detach is the phase when mobile
terminates the connection.
GPRS requires subscription
EETS 8316/NTU TC 745, Fall 2003
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#51
GPRS Attach Scenario
BTS
BSS
SGSN
HLR
IMSI, P_TMSI+OLD RAI…
Update Location
Insert Subs. Data
Insert Data Ack
Update Location
GPRS Attach Accepted
EETS 8316/NTU TC 745, Fall 2003
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#52
GPRS – Mobile Attach Scenario
Mobile sends Attach message. This
message contains P-TMSI or TMSI. It also
contains NSAPI (Network Service Point
Identifier)
SGSN contacts HLR to verify if the user is
permitted to use the service
After authentication, SGSN send back
Attach Accepted together with a TLLI
(Temporary Logical Link Identity)
EETS 8316/NTU TC 745, Fall 2003
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#53
GPRS – Mobile Attach Scenario
A database in SGSN is now populated with
mobile identity and TLLI. TLLI is used by
logical link controller in the SGSN.
EETS 8316/NTU TC 745, Fall 2003
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#54
GPRS – Setting Up Packet Data Session
After attach the mobile is known by SGSN
and have an identity there, but it is not
known to the external network.
First it needs to create an identity for itself
by performing a procedure called PDP
Context Activation. PDP is Packet Data
Protocol, which could be IP or x.25
protocol.
EETS 8316/NTU TC 745, Fall 2003
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#55
PDP Context Activation
BTS
BSS
SGSN
Activate PDP Context
Create PDP
Context Request
NASPI, PDP type
PDP, QoS,APN
Activate PDP Context Accepted
PDP Type, PDP Address, QoS
EETS 8316/NTU TC 745, Fall 2003
GGSN
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Create PDP
Context Response
PDP Address, QoS
ENGINEERING
#56
PDP Context Activation, Cont..
Mobile requests PDP Context Activation
Based on the information provided, SGSN
determines which GGSN to connect to. The
GGSN should be capable to support the
PDP requested by mobile
GGSN updates its data base and assign a
TID to the mobile and SGSN
SGSN updates its data base with the GGSN
address and TID. It then send PDP Context
Activation Accepted message to mobile
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#57
Actually Sending Data
After PDP Context Activation the mobile is
known to the external packet network (PDN)
When SGSN receives data from mobile, it
looks up its database and relate the TLLI to
NSAPI.
SGSN and SNDPC pad the IP packet and
replace the destination address with GGSN
IP address and sets GTP header to TID
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#58
Actually Sending Data, Cont…
Packets are then sent to GGSN with SGSN
as sender
At GGSN, the additional information is
removed to get the original packet . The
packet can now be routed to its intended
destination.
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#59
GPRS Terminology
APN = Access Point Name
PDP = Packet Data Protocol
NSAPI = Network Service Area Point
Identifier
TLLI = Temporary Logical Link Identifier
LLC = Logical Link Control
TID = Tunnel Identifier
EETS 8316/NTU TC 745, Fall 2003
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#60
GPRS Terminology
PDN = Packet Data Network
SNDCP = Sub network Dependent
Convergence Protocol
GTP = GPRS Tunneling Protocol
EETS 8316/NTU TC 745, Fall 2003
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#61
Local Area Networks Primer
General characteristics
—Small number of stations (e.g., tens hundreds)
—Diameter of a few kilometers (e.g., building)
—High bandwidth of several Mb/s or more
—Single (private) ownership
—Homogeneous user community
—Random contention for a shared medium
(radio) follows a medium access control
(MAC) protocol
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#62
LAN Primer, Cont
—Why not fixed-assignment multiple access?
• Each station could use separate
frequency bands (FDMA), time slots
(TDMA), or codes (CDMA)
• No contention but inefficient because LAN
data is typically bursty
—Topology is usually bus or dual bus, ring or
dual ring, star
• Logical topology can be different from
physical topology
EETS 8316/NTU TC 745, Fall 2003
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#63
LAN Primer, Cont
Ring
Bus
Star
Dual bus
EETS 8316/NTU TC 745, Fall 2003
Dual ring
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#64
LAN Primer, MAC Protocols
MAC protocol is a sub layer in data link
layer
For LANs, data link layer = logical link
control (LLC) sub layer + MAC sub layer
network
LLC
data link
MAC
physical
EETS 8316/NTU TC 745, Fall 2003
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- defines how stations
access the shared
medium
#65
LAN Primer, Cont MAC Protocol, Cont..
—LLC sub layer builds on MAC sub layer to
provide medium-independent
communication service to higher layers
(makes MAC sub layer transparent)
—LLC can provide appearance of
connectionless or connection-oriented
service
EETS 8316/NTU TC 745, Fall 2003
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#66
LAN Primer, MAC Protocol, Cont..
• Connectionless service treats each
message independently
–No connection setup and no
sequential order
• Connection-oriented service requires
connection setup and preserves
sequential order of messages
EETS 8316/NTU TC 745, Fall 2003
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#67
LAN Primer, Token Passing
Token ring and token bus
— Every station connected to the bus is given a token
— The token is passed according to order
— When a station has something to send, it keeps the
token until it is done, before sending it to the next
station.
It is fair and has no contention
The system encounters delays for sending
the token.
EETS 8316/NTU TC 745, Fall 2003
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#68
LAN Primer, Token Passing, Cont…
Token passing is another technique to
eliminate contention (collisions)
Token is short packet representing
permission to transmit
— Token is passed from station to station according to
an arranged order defining a logical token ring
topology
— A station with the token can transmit for a limited
time
— After transmission, token is sent to next station in
ring
EETS 8316/NTU TC 745, Fall 2003
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#69
LAN Primer, Polling
Objective to eliminate random contention
(collisions) which reduces throughput of
system
Polling is centralized control
— One station will periodically poll other stations to
see if they have data to transmit
— A polled station may transmit data, otherwise
controller will poll next station in a list
Polling involves exchange of control
messages between stations and controller
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#70
LAN Primer, Polling, Cont)…
—Efficient only if (1) roundtrip propagation
delay is small (2) overhead due to control
messages is small (3) user population is
not large and bursty
—As population increases with more bursty
users, performance of polling degrades
Polling is used widely in wired network
environments but not popular in wireless
networks
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#71
LAN Primer, Token passing, Cont
Commonly used in wired LANs (IEEE 802.4
token bus and 802.5 token ring), token
passing has not found much adoption in
wireless networks
Overhead is increased to improve
throughput under heavy load
— Issue is efficiency
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#72
Internet Primer
Internet is a set of rules that helps different
network to connect to each other. Thus the
name internet.
Any network connected to a internet
capable router can be connected to other
internet capable routers.
A host is a hardware and software entity
connected to a local loop and served by a
router.
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#73
Internet Primer (cont)
Every host has an IP address.
A node with multiple connection to the
internet has multiple IP addresses.
The IP address is used for sending
information to the host.
IP address consists of 32 bits and is
normally shown as a doted decimal
notation. Every decimal indicates one octet,
for example C013F112 is shown as
192.19.241.18
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#74
Internet Primer (cont)
Internet can be seen as collection of
network with diverse physical layer and
application connected to each other by
routers.
Nodes can join and leave the network at
anytime.
The service provided in the internet is “best
effort”, in other words, no quality of service
is guaranteed.
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#75
Internet Primer, TCP/IP Reference Model
Termial Emulator
Application
TELNET
Web Browser
FTP
HTTP
Remoter File
Access
User
Interfaces
RIP
Application
protocols
TCP
NFS
UDP
Operating
System
ICMP
Network
prorocols
Internet Protocol (IP)
802.3
UTP
PPP
RS-232
Transport
Protocols
FDDI
Fiber
Link
prorocols
Device Driver
and
Hardware
Network
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#76
Internet Primer, Abbreviations
TCP
Transmission Control Protocol
IP
Internet Protocol
FTP
File Transfer Protocol
UDP
User Datagram Protocol
RIP
Routing Information Protocol
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#77
Internet Primer, Abbreviations
DNS
Domain Name Server
ICMP
Internet Control Message Protocol
PPP
Point-to-Point Protocol
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#78
Internet Primer, Components of IP
Header
Vers
IHL
Type of
Total length
Service
Identification
Flags
Fragment Offset
Time to Live
Protocol
Header Checksum
Source Address
Destination Address
IP Options
Transport Layer (eg TCP) Header
Application Layer (eg HTTP) Header
Application Layer Data (eg Web Page)
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#79
Internet Primer, IP Address
Every node connected to the IP has an IP
address.
An address is 32 bits and contains a prefix
and a host number
In most cases, host numbers are assigned
dynamically.
Each router maintains a routing table.
Addressing in the internet is not
hierarchical.
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#80
Internet Primer, Routing
Routing in Internet is distributed.
Routing table in a router is used for
forwarding a packet towards its destination.
Three types of entry in a routing table
• Host specific. 32 bits specifies an IP Destination
Address.
• Network specific, 1< prefix length<31. Defines
the network address
• Default route, prefix =0, only if no matches are
found in the table, this route is used.
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#81
Internet Primer, Routing
If no routes matches, the node sends ICMP
Unreachable message error to the source
packet. Every node on the same link must
have identical network prefix.
DNS (Domain Name Server) are used to
translate alphanumeric address to 32 bits IP
address.
Entries in the DNS can be manual or
dynamic, almost the same way a host gets
IP address.
EETS 8316/NTU TC 745, Fall 2003
SMU
ENGINEERING
#82