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Telecommunications
Concepts
Chapter 4.2
IPv4 and
Other Networks
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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
The Internet Sublayer
IP approach
Application 1
Application 2
TCP
Application 3
UDP
any
network
Internet Protocol
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11-01-K.Steenhaut & J.Tiberghien - VUB
Transmitting IP Datagrams
IP
router
Underlying
Network
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IP Datagram
IP
router
Underlying Network Frame Underlying
Network
11-01-K.Steenhaut & J.Tiberghien - VUB
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
TCP
Application 3
UDP
Internet Protocol
Ethernet
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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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11-01-K.Steenhaut & J.Tiberghien - VUB
IP over IEEE 802 LANs
4
4
3
3
2b
802.2 cls
2b
2a
2a
1
1
IP addresses need to be translated into LAN addresses
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IP over traditional LANs
4
4
3
3
2a
2a
1
1
IP addresses need to be translated into LAN addresses
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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
Directly linked Routers
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General Purpose SDH Networks
PABX
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PABX
11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
IP Networks
Router
1.2
3.2
1.1
1.3
4.1
4.2
4.3
3.3
5.2
2.1
1.4
2.2
5.1
5.3
6.1
7.2
7.1
2.3
6.3
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6.2
11-01-K.Steenhaut & J.Tiberghien - VUB
Serial Line Internet Protocol
• 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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Point to Point Protocol
• 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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11-01-K.Steenhaut & J.Tiberghien - VUB
Point to Point Protocol
• Multiple protocols over PPP
TCP
UDP
Application,
Transport &
Network layers
?
IP
IPX
?
Physical layer
Lines
Leased
ADSL
GSM
ISDN
PSTN
PPP
• Various physical layers under PPP
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PPP
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
IP over X25
4
4
3
3
3
3
X25
2
2
1
1
X25 overhead VCN
IP datagram
IP addresses need to be translated into X25 addresses
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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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11-01-K.Steenhaut & J.Tiberghien - VUB
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
4
3
3
2
2
FR
1
FR overhead VCN
1
IP datagram
IP addresses need to be translated into PVC numbers
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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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aal
ATM
any
network
aal
ATM
Application 3
Application 2
Application 1
Application 3
Application 2
Application 1
IP over ATM
TCP-UDP
IP
11-01-K.Steenhaut & J.Tiberghien - VUB
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
4
3
3
AAL
1
ATM/AAL overhead vcn
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ATM
1
IP datagram
11-01-K.Steenhaut & J.Tiberghien - VUB
ATM Adaptation Layer
Data encapsulation
Higher layer PDU
pad AAL
ATM
header
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pad AAL
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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
ATM
Network
Router
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ARP Server
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LLC
any
network
ATM
Application 3
Application 2
Application 1
Application 3
Application 2
Application 1
LAN emulation
???
TCP-UDP
???
IP
11-01-K.Steenhaut & J.Tiberghien - VUB
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
ATM
Network
Router
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LES,BUS,LECS Servers
Bridge
11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
IP v4 Header (2)
Ver Len Typ.Ser.
Total Length
Fl.
Ident
Frag.Offset
TTL
Proto
Header Checksum
Source IP Address
Destination IP Address
Options
Padding
Typ.Serv.:
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Precedence (0 = normal, 7 = control)
D = Short delay wanted (best effort)
T = High throughput wanted (best effort)
R = High reliability wanted (best effort)
11-01-K.Steenhaut & J.Tiberghien - VUB
IP v4 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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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
Multi Protocol Over ATM
Single or initial frame
ATM
Network
= MPOA server
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11-01-K.Steenhaut & J.Tiberghien - VUB
Multi Protocol Over ATM
Subsequent frames
ATM
Network
= MPOA server
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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
Multi Protocol Label Switching
Any Network
= Ingres/Egres Router
Add signaling protocol to network to allow
establishment of virtual circuit for some data flows.
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11-01-K.Steenhaut & J.Tiberghien - VUB
Multi Protocol Label Switching
X25 overhead label
IP datagram
FR overhead
label
IP datagram
ATM overhead label
IP datagram
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 v6 Header
Ver Pri
Payload Length
Flow Label
Next Hdr Hop Lim.
Source IP Address
Destination IP Address
Flow Label : enables MPLS in IP V6
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
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11-01-K.Steenhaut & J.Tiberghien - VUB
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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11-01-K.Steenhaut & J.Tiberghien - VUB
The Future ???
Application
Application
Application
Application
Application
IP
IP+MPLS
IP+MPLS
IP+MPLS
IPv6
ATM
ATM/FR
ATM/FR
ATM/FR
ATM/FR
SDH
SDH
SDH
SDH
SDH
Optical Fibers + WDM
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11-01-K.Steenhaut & J.Tiberghien - VUB