High performance fiber networks
EITP10
Lecture 5: Protocols and networking
STEFAN HÖST
Some important protocols
• Networking
• Ethernet
• VLAN
• SONET/SDH (Core and metro network)
• CPRI (Mobile fronthaul)
Stefan Höst EITP10 Lecture 5 1
OSI and TCP/IP models
Application
Presentation
Session
Transport
Network
Data link
Physical
OSI (by ISO)
Seven layer model
Application
Transport
Internet
Network
access Access to media. Signal propagation.
Framing. Error control. Local addressing
Routing between end units. Global address
Communication between processes at units
Application specific. User interaction
TCP/IP (by DARPA)
Four layer model
Stefan Höst EITP10 Lecture 5 2
Encapsulation of frames
When you click on a link in a browser, it initiates an HTTP-request, sent with TCP.
The idea with a layered model is to use encapsulation:
Application
Transport
Internet
HTTP, Mail, DHCP, …
TCP, UDP, RTP, …
IP, IPsec
Ethernet,
SONET/SDH,
WiFi, Mobile, …
Data
TCP dataTCP header
IP dataIP header
Ethernet dataEth. header
Network
access Eth. footer
Stefan Höst EITP10 Lecture 5 3
Example of layered traffic
Application
Presentation
Session
Transport
Network
Data link
Physical
Data link
Physical
Data link
Physical
Network
Data link
Physical
Network
Data link
Physical
Application
Presentation
Session
Transport
Network
Data link
Physical
802.11 MAC 1000BASE-T 1000BASE-LX
IP IP
TCP
HTTP
Switch and access point RouterPhone Server
WiFi
Copper (Cat6)
FttH (2xSMF)
Stefan Höst EITP10 Lecture 5 4
Tunneling
Use a packet as payload in another protocol, to deliver over network, e.g.
• IP over IP (IPv4 over IPv6 network and vice versa)
• IP over IPsec (secure connection, e.g. VPN)
• GTP (GPRS tunneling protocol. Used by GSM, UMTS, LTE and 5G)
Stefan Höst EITP10 Lecture 5 5
GTP tunneling
User data
IP (user)
GTP
UDP
IP
L1+L2
EPCeNBUE
User data
IP (user)
L1+L2
GTP
UDP
IP
L1+L2
PDCP
RLC
L1+L2
PDCP
RLC
L1+L2
IP (user)
User data
IP (user) encryptedGTP
Header
UDP
Header
IP
Header
Eth
Header
Eth
Tail
Stefan Höst EITP10 Lecture 5 6
Ethernet
Started as LAN-protocol in 1980s, as a bus over coax. Today include standards for most
(fix) medium and rates, e.g.
Name Rate Description
100BASE-TX 100 Mbps Cat5 TP cables, 1 pair each direction
1000BASE-T 1 Gbps Cat5 TP cables, 4 bi-directional pairs
10GBASE-T 10 Gbps Cat 6a, 100 m
100BASE-FX 100 Mbps Fiber, two fibers
1000BASE-LX 1 Gbps Fiber, two SMF, 10 km, in Ethernet in the first mile
10GBASE-LR 10 Gbps Long-reach 10 km, uses Fabry–Pérot laser
10GBASE-PR 10 Gbps PON
40GBASE-LR4 40 Gbps WDM (4×10G NRZ)
100GBASE-ER4 100 Gbps WDM, (4×25G NRZ)
400GBASE-LR8 400 Gbps WDM (8×50G PAM4)
Stefan Höst EITP10 Lecture 5 7
Typical structures of Ethernet
Point-to-point (P2P) Bus
Star Star of stars or Tree
Stefan Höst EITP10 Lecture 5 8
Line coding in Ethernet
In NRZ long runs of same output might be problematic for synchronisation. Prevent long
sequences of 1s or 0s.
Runlength coding like 8b/10b or 64b/66b (Ethernet). Ex. 4b/5b:
Data Codew
0000 11110
0001 01001
0010 10100
0011 10101
Data Codew
0100 01010
0101 01011
0110 01110
0111 01111
Data Codew
1000 10010
1001 10011
1010 10110
1011 10111
Data Codew
1100 11010
1101 11011
1110 11100
1111 11101
Stefan Höst EITP10 Lecture 5 9
Frame structure (general)
PRE Preamble, 7 bytes 10101010. Synchronisation
SFD Start of frame delimiter, 10101011
DA Destination address, 6 byte (MAC address)
SA Source address, 6 byte (MAC address)
Length / type 2 bytes, if ≤ 1500 it is payload length (bytes) and if ≥ 1536 it is an
optional parameter
Payload Data. Between 46-1500 B. In Gigabit ethernet 500-1500.
FCS 4 Byte (32 bit) CRC, error detection
Stefan Höst EITP10 Lecture 5 10
Frame structure (VLAN)
VLAN header 4 bytes
If two first bytes are 0x8100 then next two bytes are VLAN identifier
Use 12 bit to assign VLAN tag (1-4094)
• Standard: IEEE 802.1Q
• A way to build several virtual networks (LANs) over one physical network (LAN).
• VLANs are extensively used for e.g. (virtual) management networks and traffic
separation.
Stefan Höst EITP10 Lecture 5 11
SONET/SDH
• PDH, Pleisiochronious digital hierarchy (from 1960s), multiplexing of phone calls
– Voice band: 4 kHz
– Sample with 8 kHz and quantize with 8 bit/sample: 64 kbps
• SONET/SDH are two, very similar, extensions of PDH (in 1980s)
– SONET, Synchronous optical network (in North Amarica) [ANSI]
– SDH, Synchronous digital hierarchy (Rest of the world) [ETSI + ITU]
– Transmission of several phone calls with TDM
Stefan Höst EITP10 Lecture 5 12
SONET/SDH
• Packet based circuit switched paths (containers for data)
• Can carry most traffic, e.g. Ethernet or IP
• Multiplexing
– Very efficient multiplexing strategies
– Clock synchronisation between nodes in network (master clock)
– Easy to add or extract lower rate streams
• Mangement
Channel for management data, Performance monitoring traffic identification, etc
• Interoperability
Well defined standard
Stefan Höst EITP10 Lecture 5 13
SONET/SDH Framing
STS-1 frame:
• Transmission 8 k frames/s
125 µs/frame
• 810B⇒ 51.84 Mbps
(810×64 kbps)
• Data: 783B⇒ 50.112 Mbps
Stefan Höst EITP10 Lecture 5 14
SONET/SDH Framing
STS-N frame: Multiplex N STS-1 frames
Stefan Höst EITP10 Lecture 5 15
Data channels in SONET/SDH
Phy SONET Factor SDH Rate [Mbps]
OC-1 STS-1 (STM-0) 51.84
OC-3 STS-3 3 STM-1 155.52
OC-12 STS-12 4 STM-4 622.08
(OC-24) (STS-24) 2 1 244.16
OC-48 STS-48 2 STM-16 2 488.32
OC-192 STS-192 4 STM-64 9 953.28
OC-768 STS-768 4 STM-256 39 814.32
Concatenation STS-Nc, where N: 3, 12, 48, 192
Concatenates N adjecent frames
Virtual concatenation (VCAT) STS-N-Mv, where M arbitrary
Concatenates M (possibly non-contiguous) STS-N frames
Stefan Höst EITP10 Lecture 5 16
Line coding in SONET/SDH
In NRZ long runs of same output might be problematic for synchronisation. Interleaver or
scrambler (SONET/SDH)
Stefan Höst EITP10 Lecture 5 17
SONET/SDH networking
Equipment
• Terminal multiplexer (TM)
End node in network
• Add/drop multiplexer (ADM)
Add or drop lower rate streams from/to multiplexed stream
• Digital crossconnect (DCS)
Control (software) of streams in a central office (CO)
Topology
• Point to point (P2P)
• Ring
– Unidirectional path-switched ring (UPSR)
– Bidirectional line-switched ring (BLSR)
Stefan Höst EITP10 Lecture 5 18
SONET/SDH networking
OC-48 ADM
ADM
ADM
ADM
TM
TM
TM
DCSOC-192 ADM
ADM
ADM
ADM
TM
TM
TM
TM
ADM
Stefan Höst EITP10 Lecture 5 19
Mobile network and CPRI
Mobile core
EPC
eNB
BBU
RU
CPRI
Stefan Höst EITP10 Lecture 5 20
C-RAN
C-RAN, Cloud Radio Access Network
Mobile core
EPC
BBU
RRUCPRI
Backhaul Fronthaul
BBU Baseband unit. Produce baseband radio samples
RRU Remote radiohead. DAC, shift to RF and analog front-end (amplifier)
CPRI Common public radio interface. Transport of radiosamples
Stefan Höst EITP10 Lecture 5 21
CPRI
CPRI is a protocol for transport of digital radio signals.
• Frames are containers for radio frames
Basic frame: samples for 260.416 ns radio signal
• Supports GSM/EDGE (2G), UTRA (3G), E-UTRA/LTE (4G), WiMAX
• Normally point-to-point, but also supports multiplexing
• Can operate over at least 10 km
• At most 5 µs delay (excl. propagation delay) and at most 10−12 BER
• Sampling 8-20 b/real sample. Normal 15 b/real sample (⇒ 30 b/sample)
⇒ data expansion by a factor of about 10-14
• Line coding: 8B/10B or 64B/6B
Stefan Höst EITP10 Lecture 5 22
Number antenna signals and required bitrates
WLTE[MHz]/Rb[Mbps]
Line 1.25 2.5 5 10 15 20
Option Rate[Mbps] coding 77 154 307 614 921 1 229 (Mb/s)
1 614 8/10 8 4 2 1 − −
2 1 229 8/10 16 8 4 2 1 1
3 2 458 8/10 32 16 8 4 2 1
4 3 072 8/10 40 20 10 5 3 2
5 4 915 8/10 64 32 16 8 5 4
6 6 144 8/10 80 40 20 10 6 5
7 9 830 8/10 128 64 32 16 10 8
63 127 253 507 760 1 013 (Mb/s)
8 10 138 64/66 160 80 40 20 13 10
9 12 165 64/66 192 96 48 24 16 12
Stefan Höst EITP10 Lecture 5 23

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