Telecommunications Concepts

volleyballbeginnerNetworking and Communications

Oct 27, 2013 (3 years and 11 months ago)

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Telecommunications

Concepts

Chapter 4.2

IPv4 and

Other Networks

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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The Internet Sublayer

IP approach

Application 1

Application 2

Application 3

TCP

Internet Protocol

any

network

UDP

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Transmitting IP Datagrams

IP

router

IP

router

Underlying

Network

Underlying

Network

IP Datagram

Underlying Network Frame

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP over Ethernet

Application 1

Application 2

Application 3

TCP

Internet Protocol

Ethernet

UDP

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Address Resolution Protocol


Problem :


Mapping of IP and Ethernet addresses


Solution :


ARP entity broadcasts IP address over
Ethernet


All hosts compare broadcasted IP address with
their own (software defined) IP address


Identified host answers the ARP broadcast.


IP datagrams for resolved address are
encapsulated in Ethernet frame with Ethernet
destination address.

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IP over IEEE 802 LANs


4

3

2b

4

3

2b

1

1

IP addresses need to be translated into LAN addresses

2a

2a

802.2 cls

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IP over traditional LANs


4

3

4

3

1

1

IP addresses need to be translated into LAN addresses

2a

2a

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Reverse

Address Resolution Protocol


Problem :


Diskless workstations can not keep their (software
defined) IP address.


Solution :


A configuration server keeps mapping between IP
addresses and corresponding Ethernet addresses.


At boot time a diskless station broadcasts a RARP
frame.


Configuration server reads source Ethernet address
in RARP frame and answers with corresponding IP
address.

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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Directly linked Routers

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General Purpose SDH Networks

PABX

PABX

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP Networks

Router

1.2

1.4

1.3

1.1

2.1

3.3

3.2

4.1

4.3

4.2

5.2

2.2

2.3

6.1

6.2

5.3

5.1

7.1

7.2

6.3

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S
erial
L
ine
I
nternet
P
rotocol


Designed in 1984 by Rick Adams (RFC 1055)


For temporary IP links


Data Link :


IP datagrams encapsulated in SLIP frames


Frame delimited by unique character (11000000)


Character stuffing within the frame


No error detection (nor correction !)


Network Layer : no layer 3 functions


Many slightly different versions (RFC 1144)


Essentially obsolete !

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P
oint to
P
oint
P
rotocol


Designed by the IETF (RFC 1661,RFC 1662,RFC 1663)


For temporary links (various network protocols)


Data Link : similar to HDLC or 802.2, but with bytes


Payload encapsulated in P frames


Frame delimited by 802.2 flag (01111110)


Character

stuffing within the frame


Optional error correction with sliding window


Network Layer : support for different protocols


Connection management, with authentication


Network protocol identifier field

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P
oint to
P
oint
P
rotocol


Multiple protocols over PPP











Various physical layers under PPP

TCP

IP

PPP

UDP

IPX

?

Application,

Transport &

Network layers

Physical layer


PSTN



ISDN



GSM


Leased


Lines


ADSL


?

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P P P


Advantages over SLIP


CRC on every frame for error detection


A link control protocol to:


establish connection


negotiate options


close connection


Specific network control protocols


e.g. dynamic IP address assignment


e.g. TCP/IP header compression

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IP over ISDN


Usage :


Temporary interconnections


Back
-
up for leased lines


Additional capacity for overloaded leased lines


Main problem :

IP : Connectionless >< ISDN : Connection oriented


Solutions :


One call per datagram (fast connection)


Keep connection for entire billing units


Keep connection during work
-
hours

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP over X25


4

3

4

3

1

1

2

2

X25

IP datagram

VCN

X25 overhead

IP addresses need to be translated into X25 addresses

3

3

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IP over X25


Fast select call :
best match between IP and X25


Virtual circuit between source and destination routers


Switched :
opened and closed when ?


Permanent :
analog to leased line, preferred solution


Address resolution :



IP address need to be translated into


X25 address for fast select call or for opening circuit


VC number for forwarding packet(s)

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP over Frame Relay


4

3

2

4

3

2

1

1

FR

IP datagram

VCN

FR overhead

IP addresses need to be translated into PVC numbers

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IP over Frame Relay


IP addresses need to be translated into Permanent
Virtual Circuit Numbers.


Assigning different application flows to PVC’s with
different CIRs can enforce QOS criteria


Passing the Congestion Notification bits to the
transport layer could be useful but requires special IP
and TCP/UDP implementations

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP over ATM

Application 1

Application 2

Application 3

TCP
-
UDP

IP

any

network

Application 1

Application 2

Application 3

ATM

aal

ATM

aal

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IP over ATM,
but...


IP is connectionless,


each packet contains destination and origin
addresses.


Broadcasting of messages frequently required


ATM is connection oriented,


Virtual channels need to be established (and
evt. closed)


each cell contains a Virtual Channel number


ATM addresses are unrelated to IP addresses


No broadcasting


Connection management required.


Address Translation mechanism required.


Broadcast server required

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IP over ATM


4

3

4

3

1

1

ATM

IP datagram

vcn

ATM/AAL overhead

AAL

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ATM Adaptation Layer

Data encapsulation

pad

AAL

pad

AAL

Higher layer PDU

ATM

header

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IP over ATM,
solutions

1
. Classical IP over ATM


Initially proposed by IETF


ARP server translates the addresses


All addresses stored on one ARP server define
one subnet


Different subnets have to communicate via
routers


Broadcasts have to be generated by IP entity


Requires modified IP implementation

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Classical IP over ATM

Router

ARP Server

ATM

Network

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LAN emulation

Application 1

Application 2

Application 3

TCP
-
UDP

IP

any

network

ATM

LLC

Application 1

Application 2

Application 3

???

???

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IP over ATM,
solutions

2
. LAN emulation


Proposed by ATM Forum


Ethernet MAC emulation


Two or three servers:

»
Lan Emulation Server registers and
translates MAC addresses

»
Broadcast and Unknown Server distributes
the broadcast and multicast packets

»
Lan Emulation Configuration Server keeps
ATM addresses of Lan Emulation Servers


No modifications to IP

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LAN Emulation

Router

LES,BUS,LECS Servers

ATM

Network

Bridge

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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IP and QOS


Facts :


Connectionless IP is unable to guarantee QOS


Multi
-
media applications require QOS


Solutions :


Provide more than enough capacity between routers


Force, for specific flows, special routes.


Use QOS resources of underlying network

»
Traditional routing algorithms do not allow
differentiation between datagrams with same
destination.

»
Additional intermediate protocols needed

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IP and QOS


Facts :


Connectionless IP is unable to guarantee QOS


Multi
-
media applications require QOS


Solutions :


Provide more than enough capacity between routers


Force, for specific flows, special routes.


Use QOS resources of underlying network

»
Traditional routing algorithms do not allow
differentiation between datagrams with same
destination.

»
Additional intermediate protocols needed

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IP and QOS


Facts :


Connectionless IP is unable to guarantee QOS


Multi
-
media applications require QOS


Solutions :


Provide more than enough capacity between routers


Force, for specific flows, special routes.


Use QOS resources of underlying network

»
Traditional routing algorithms do not allow
differentiation between datagrams with same
destination.

»
Additional intermediate protocols needed

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IP
v
4

Header
(2)

Source IP Address

Destination IP Address

Options

Padding

Header Checksum

Ident

Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver

Len

Typ.Serv.:

Precedence (0 = normal, 7 = control)



D = Short delay wanted (best effort)



T = High throughput wanted (best effort)



R = High reliability wanted (best effort)

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IP v
4

Options

Class 0






Length

Option


1 : End of option list





1


2 : Security and handling restrictions

11


3 : Loose Source Routing



var


7 : Record route




var


9 : Strict Source Routing



var

Class 2

Option


4 : Internet timestamp



var

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QOS Routing

Ser = D

Ser = T

Ser = R

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IP and QOS


Facts :


Connectionless IP is unable to guarantee QOS


Multi
-
media applications require QOS


Solutions :


Provide more than enough capacity between routers


Force, for specific flows, special routes.


Use QOS resources of underlying network (ATM)

»
Traditional routing algorithms do not allow
differentiation between datagrams with same
destination.

»
Additional intermediate protocols needed

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Multi Protocol Over ATM

Single or initial frame

ATM

Network


= MPOA server

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Multi Protocol Over ATM

Subsequent frames

ATM

Network


= MPOA server

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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Multi Protocol Label Switching



= Ingres/Egres Router

Any Network

Add signaling protocol to network to allow
establishment of virtual circuit for some data flows.

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Multi Protocol Label Switching

IP datagram

label

X25 overhead

IP datagram

label

FR overhead

IP datagram

label

ATM overhead

Optimizes IP address to VC number translation

by explicitly identifying flows of datagrams

with common QOS requirements.

MPLS = attempt to standardize these labels

(RFC 3031
-

Jan 2001)

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IP
v
6

Header

Source IP Address

Destination IP Address

Payload Length

Flow Label

Next Hdr

Hop Lim.

Ver

Pri

Flow = connection oriented communication

implemented through connectionless service

Flow uniquely identified by

source address

flow label

Avoids label field between layer 2 and 3 overhead

Flow Label :
enables MPLS in IP V6

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Contents


Transmitting IP datagrams


IP over Local Area Networks


IP over Wide Area Networks


IP over leased lines


IP over circuit switched networks


IP over packet switched networks

»
IP over X25

»
IP over Frame Relay

»
IP over ATM

»
IP and Quality of Service


MPLS


Conclusions

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The Future ???

IP

ATM

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

Optical Fibers + WDM

IPv6

ATM/FR

SDH

Application