001. general topics.pdf

General Topics

FT48923EN03GLA0 2012 Nokia Siemens Networks

1

Content 1 LAN and VLAN: some considerations 3 1.1 Definitions 3 1.2 Domains in a traditional LAN 4 1.3 Domains in a VLAN 8 1.4 Traffic separation by VLAN 11 1.5 Tagging 12 1.6 VLAN Aware / Unaware 19 1.7 Links Types 20 1.8 Q-in-Q 23 1.9 Spanning Tree Protocol (802.1d) 27 1.10 Rapid Spanning Tree Protocol RSTP (802.1w) 33 1.11 Multiple Spanning Tree Protocol MSTP (802.1s) 35 2 Carrier Ethernet: Some Concepts 41 2.1 What is Carrier Ethernet 41 2.2 MEF: Metro Ethernet Forum 42 2.3 Cooperation with Other Standard Bodies 44 2.4 IEEE: Institute of Electrical and Electronics Engineers 44 2.5 IETF: The Internet Engineering Task Force 44 2.6 ITU: International Telecommunication Union Telecommunication

Standardization Sector 45 2.7 Carrier Ethernet Terminology: Basic Components 46 2.8 Carrier Ethernet Service Types 60 2.9 Circuit Emulation Services over Packet (CESoP) 61 2.10 FlexiPacket EVC and Services 67 3 Quality of Service in the HUB 71 3.1 QoS Mechanism 72 3.2 Classifier and Packet Marker 75 3.3 Policer 79 3.4 Buffer Manager: Congestion Avoidance 82

General Topics

General Topics


3

1 LAN and VLAN: some considerations 1.1 Definitions A LAN or Local Area Network is a computer network (or data communications network) which is confined in a limited geographical location. A Virtual (or logical) LAN is a local area network with a definition that maps workstations/PCs on some other basis than geographic location (for example, by department, type of user or primary application)

General Topics


4

1.2 Domains in a traditional LAN In a traditional Ethernet LAN, stations connected to the same media, share a domain. In this domain, every station hears broadcast frames transmitted by every other station. As the number of stations grows, contention and broadcast traffic increase a lot. At some point, the Ethernet becomes saturated. To operate efficiently, the LAN must be divided into smaller pieces. In a traditional LAN, stations are connected to each other by means of HUBS or REPEATERS.

HUB HUB

One collision Domain

One Broadcast Domain

Fig. 1 Domains in a traditional LAN (1)

General Topics


5

A BRIDGE (or a L2 SWITCH) is able to divide one collision domain in different collision domains.

HUB HUB

Two collision Domains

One Broadcast Domain

BRIDGE


General Topics


6

A BRIDGE (or a L2 SWITCH) do not forward collisions, but allows broadcast and multicast passing through. Broadcast domain refers to a part of network where a single broadcast packet is transmitted to all segments of the network (i.e. ARP request, NETBIOS name request). This type of traffic, affects the whole network because each device receiving a broadcast frame must analyze it. If broadcast frames increases in frequency, available bandwidth decrease up to be exhaust (BROADCAST STORM).

SWITCH = MULTIPORT BRIDGE

L2 SWITCH


General Topics


7

A ROUTER may be used to prevent Broadcast and Multicast from traveling through the network because it is able to segment a LAN in different Broadcast domains.

HUB HUB

Two collision Domains

Two Broadcast Domain

ROUTER

Fig. 4 Domains in a traditional LAN

General Topics


8

1.3 Domains in a VLAN VLANs allow a network manager to logically segment a LAN into different broadcast domains without using routers. Bridging software is used to define which workstations are to be included in the broadcast domain.

VLAN 2 Broadcast Damain


VLAN 1 Broadcast Domain


L2 SWITCH L2 SWITCH

Fig. 5 Domains in a VLAN (1)

General Topics


9

ROUTERS are necessary only to make possible communication between different VLANs. VLAN IS A LOGICALLY DEFINED BROADCAST DOMAIN.





L2 SWITCH L2 SWITCH

ROUTER


General Topics


10

The advantages of VLANs as regards to traditional LANs are shown in Fig. 7.

Periodically, sensitive data may be broadcast on a network. Placing only those users who can have access to have access to that data on a VLAN can reduce the chances of an outsider gaining access to the data

SECURITY

Routers are only used to interconnect different broadcast domains

REDUCED COSTS

Simply moves, adds and changesSIMPLIFIED ADMINISTRATION

Independent from the physical wiringVIRTUAL WORKGROUPS

Better control of broadcastPERFORMANCE


General Topics


11

1.4 Traffic separation by VLAN With VLANs it is possible to separate different logical networks on one physical infrastructure supporting the traffic separation. Figure Fig. 8 shows a Traffic Separation Example by VLAN.

RNC

Ethernet Network

Flexi BTS Nr.1

Flexi BTS Nr.2

VLAN1 -> Voice from Flexi BTS Nr.1 to RNC

Traffic over same physical port separated by VLAN.

VLAN2 -> Data from Flexi BTS Nr.1 to RNC

VLAN4 -> Data from Flexi BTS Nr.1 to RNC

VLAN3 -> Voice from Flexi BTS Nr.2 to RNC

Fig. 8 Traffic separation by VLAN

General Topics


12

1.5 Tagging Tagging is a process used to identify the VLAN originating. The VLAN tagging scheme in 802.1q results in four bytes of information being added to the frame following the source address and preceding the type/length field. This increases the maximum frame size in Ethernet to 1522 bytes. Fig. 9 reports a IEEE 802.3 untagged frame Fig. 10and Fig. 11 explain the TAG fields.

MAC DA6 bytes

Payload46-1500 bytes

FCS4 bytes

Basic IEEE 802.3 Ethernet Frame: minimum length 64 bytes, maximum length 1518 bytes

Destination & Source MAC Addresses:The Destination MAC Address field identifies the station or stations that are to receive the frame. The Source MAC Address identifies the station that originated the frame. A Destination Address may be a unicast destined for a single station, or a "multicast address" destined for a group of stations. A Destination Address of all 1 bits refers to all stations on the LAN and is called a "broadcast address".

Length/Type:If the value of this field is less than or equal to 1500, then the Length/Type field indicates the number of bytes in the Payload field. If the value of this field is greater than or equal to 1536, then the Length/Type field indicates protocol type.

Payload (MAC Client Data):This field contains the data transferred from the source station to the destination station or stations.

Frame Check Sequence:This field contains a 4-byte cyclical redundancy check (CRC) value used for error checking.

MAC SA6 bytes

Length/Type2 bytes

VLAN tags may be added here

Preamble+SD

8 bytes

InterframeGap

12 bytes

64-1518 bytes

Fig. 9 IEEE 802.3 Untagged Frame

General Topics


13

CFI

16 bits

TAG Protocol Identifier TPID 0x8100

1bit 12 bits3bits

Priority VLAN ID

TCI Tag Control Identifier

TPID TAG Protocol Identifier

2 bytes2 bytes

4 bytes

IEEE 802.3 Frame without VLAN Tag Header

IEEE 802.3 with 802.1Q 4-Byte VLAN Tag Header

User priority (Priority Code Point PCP) CFI (Canonical format identifier)

VLAN ID

General Topics


14

1.5.1 Class of Service (CoS) IEEE 802.1p The IEEE 802.1p provides a standard and interoperable way to set the priority bits in a frames header and to map these settings to TRAFFIC CLASSES. There are 8 TRAFFIC CLASSES (3 Bits) according to the table reported in Fig. 12.

000BEBEST EFFORT

001BKBACKGROUND

010RRESERVRD FOR FUTURE USE

011EEEXCELLENT EFFORT TRAFFIC

100CLCONTROLLED LOAD TRAFFIC

101VIVIDEO TRAFFIC

110VOVOICE TRAFFIC

111NCNETWORK CONTROL TRAFFIC

Fig. 12 Quality Of Service IEEE 802.1p (1)

WARNING Of course, network operators may choose to implement traffic differentiation on a per VLAN-ID basis rather than using the three CoS bits.

General Topics


16

FlexiPacket First Mile 200, HUB 800 and FlexiPacket MultiRadio have 8 queues and the association between PCP and Priority Queue is reported in Fig. 15.

FPFM-200/HUB-800/FPMR PriorityQueue

PCP

Fig. 15 FPFM-200/HUB 800/FPMR PCP - Priority queues association

General Topics


18

When 4 queues are available, like in the FlexiPacket ODU, the 8 PCPcodes could be associated to four priority values as reported in Fig. 17 (FlexiPacket ODU default).

37

26

25

24

13

12

01

00

Queue PriorityValue

PCP

Fig. 17 FlexiPacket ODU Priority Code Point Configuration

When 5 queues are available, like in FlexiPacket HUB 2200/1200, the 8 PCP codes could be associated to five priority values as reported in Fig. 16 (HUB 1200/2200 configuration).

47

36

25

24

13

12

01

00

Queue PriorityValue

PCP

Fig. 18 FlexiPacket HUB (2200/1200) Priority Code Point Configuration

General Topics


19

1.6 VLAN Aware / Unaware VLAN AWARE If the data is to go to a device that knows about VLAN implementation (VLAN Aware), the VLAN identifier is added to the data. VLAN UNAWARE If it is to go to a device that has no knowledge of VLAN implementation (VLAN Unaware), the BRIDGE sends the data without the VLAN identifier.

TAG added/removed

TAGTAG

FrameFrame

TAGTAG

FrameFrame

TAGTAG

FrameFrame

FrameFrameFrameFrame

FrameFrameFrameFrameFrameFrameFrameFrame

TAG added/removed

L2-Switch L2-Switch

VLAN awareBridge/L2-Switch

VLAN aware

VLAN unaware stations

Bridge/L2-Switch

Fig. 19 VLAN Aware/Unaware

General Topics


20

1.7 Links Types Devices on a VLAN can be connected in three ways based on whether the connected devices are VLAN Aware or VLAN Unaware as reported in Fig. 20, Fig. 21, Fig. 22. Recall that a VLAN aware device is one which understands VLAN memberships (i.e. which users belong to a VLAN) and VLAN formats.

This is a combination of the previous two links. This is a link where both VLAN aware and VLAN Unaware devices are attached.A hybrid link can have both tagged and untagged frames, but all the frames for a specific VLAN must be either tagged or untagged.

Hybrid Link

An access link connects a VLAN Unaware device to the port of a VLAN Aware Bridge.Access Link

All the devices connected to a trunk link, including workstations, must be VLAN Aware.All frames on a trunk link must have a special header attached. These special frames are called TAGGED FRAMES.

Trunk Link

DESCRIPTIONLINK TYPE

Fig. 20 Link Types

General Topics


21

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

L2-SwitchL2-Switch

Trunk Link

Trunk Link

VLAN-aware Workstation

VLAN-aware Bridge/L2-Switch


Fig. 21 Trunk Link

General Topics


22

L2-Switch

Access Link

VLAN-unaware Device


Fig. 22 Access Link

General Topics


23

1.8 Q-in-Q In the VLAN tag field defined in IEEE 802.1Q, only 12 bits are used for VLAN IDs, so a device can support a maximum of 4,094 VLANs. In actual applications, however, a large number of VLAN are required to isolate users, especially in metropolitan area networks, and 4,094 VLANs are far from satisfying such requirements. The so called Q-in-Q (IEEE 802.1ad) feature enables the encapsulation of double VLAN tags within an Ethernet frame, with the inner VLAN tag being the customer network VLAN tag while the outer one being the VLAN tag assigned by the service provider to the customer. In the backbone network of the service provider (the public network), frames are forwarded based on the outer VLAN tag only, while the customer network VLAN tag is shielded during data transmission. The Q-in-Q feature enables a device to support up to 4,094 x 4,094 VLANs.

DA SA

DA SA

DA SA

LEN/Etype Data FCS

TPID TAG LEN/Etype Data FCS

TPID TAG LEN/Etype Data FCSTPID TAG

Untagged Ethernet Frame

Service Provider Tagging

Customer Tagging

6 6 2 446 to 1500

2 2

2 2

Bytes

Single Tagged Ethernet Frame

Double Tagged Ethernet Frame

Fig. 23 Untagged, Single Tagged and Double Tagged Ethernet Frames

General Topics


24

Double TAG VLAN Tag Control Identifier (TCI) is reported in Fig. 24

DA SA TPID TAG LEN/Etype Data FCSTPID TCI

2 2Double Tagged Ethernet Frame

User PriorityPriority Code Point D

EI S-VIDService V-LAN Identifier

3 bits 1 bit 12 bits

1 bit Drop Eligible Indicator drop first, if congestion occurs

Fig. 24 Double TAG VLAN Tag Control Identifier

General Topics


25

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Double Tag Example

S-VLAN 2

C-VLAN 2

A

D C

E

B

23

4

S-VLAN 2

C-VLAN 2

Swap outer with 4 and forward to D- port 2

221

Forwarding DecisionVLAN Outer Tag

VLAN Inner Tag

A-Port

S-VLAN 2

C-VLAN 2

x1S-VLAN 4

C-VLAN 2

1

2

S= Service ProviderC= Customer

Fig. 25 Double TAG Example

General Topics


26

1.8.1 Q in Q TPID The QinQ frame contains the modified tag protocol identifier (TPID) value of VLAN Tags. By default, the VLAN tag uses the TPID field to identify the protocol type of the tag. The value of this field, as defined in IEEE 802.1Q, is 0x8100. The device determines whether a received frame carries a service provider VLAN tag or a customer VLAN tag by checking the corresponding TPID value. After receiving a frame, the device compares the configured TPID value with the value of the TPID field in the frame. If the two match, the frame carries the corresponding VLAN tag. For example, if a frame carries VLAN tags with the TPID values of 0x88a8 and 0x8100, respectively, while the configured TPID value of the service provider VLAN tag is 0x88a8 and that of the VLAN tag for a customer network is 0x8200, the device considers that the frame carries only the service provider VLAN tag but not the customer VLAN tag. In addition, the systems of different vendors might set the TPID of the outer VLAN tag of QinQ frames to different values. For compatibility with these systems, you can modify the TPID value so that the QinQ frames, when sent to the public network, carry the TPID value identical to the value of a particular vendor to allow interoperability with the devices of that vendor. The TPID in an Ethernet frame has the same position with the protocol type field in a frame without a VLAN tag.

General Topics


27

1.9 Spanning Tree Protocol (802.1d) In order to increase the availability may be useful to introduce redundancy. In presence of simultaneous alternative paths, copies of frames are created producing the so called LOOPS. In order to avoid loops, a SPANNING TREE algorithm must be implemented to disable some bridge interfaces. Spanning Tree Protocol (STP) is a link manager protocol that provides path redundancy while preventing loops in the network. STP algorithm creates a tree topology, and loop free path from the root to all of the nodes in the LAN.

1.9.1 Spanning Tree Root bridge selection The bridges exchange Configuration Bridge Protocol Data Units (BPDUs) in order to learn the topology of the network. A root bridge is selected according to MAC or priority. A lowest cost path to the root is chosen, and redundant links are blocked.

Root Bridge

= blocked links

Fig. 26

General Topics


28

In case of link failure, BPDUs are again exchanged in the network to notify tree of the topology change. Redundant routes are enabled.

Root Bridge

Fig. 27 Redundant root enabled

General Topics


29

1.9.2 Spanning Tree Port roles Spanning Tree port roles are:

Root port (R): pointing towards the root bridge. Designated port (D): active ports that arent root ports. Non Designated Alternate port (A): one side of a blocked link (the other side is

Designated port).

Root Bridge

R

RR

R DD

D

D

D

D

A

A

Fig. 28

TIP 1) The root sends hello BPDU (cost of 0) out all interfaces. 2) Neighboring bridges forward hellos out their non-root designated ports, identifying root, with their cost added. 3) Each bridge in the network repeats the previous step. 4) Root repeats step 1 every {hello time}.

General Topics


30

1.9.3 Spanning Tree Port states Spanning Tree Port states are:

Blocking Listening Learning Forwarding Disable

Root BridgePort role: RootPort state: Forwarding

Port role: RootPort state: Forwarding

Port role: Non DesignatedPort state: Blocking

Fig. 29 Spanning Tree Port States

General Topics


31

Port states diagram is reported in Fig. 30.

Listening

Forwarding

Blocking Learning

Forwarding

DelayM

ax Age

Forwarding

Delay

Fig. 30 Port States Diagram

Blocking - its the default state of an STP port when a bridge is powered on, and when a port is shut down to eliminate a loop Ports in a blocking state do not forward frames or learn MAC addresses. They will still listen for BPDUs from other switches, to learn about changes to the switching topology. Port remains in the state of blocking as long as it continues to receive BPDUs containing information better than those already held (i.e. it receives a BPDU that indicates a better path to the root switch. When there is a topology change, the port starts a Message_Age_Timer, which is initialized to the value Max Age. When the timer expires, the port goes into Listening state.

Listening- the port will listen for BPDUs to participate in the election of a Root Bridge, Root Ports, and Designated Ports. Ports in a listening state will not forward frames or learn MAC addresses.

General Topics


32

Learning- After a brief period of time, called Forwarding Delay, a port in a listening state will be elected either a Root Port or Designated Port, and placed in a learning state. Ports in a learning state listen for BPDUs, and also begin to learn MAC addresses. However, ports in a learning state will still not forward frames.(Note: If a port in a listening state is not kept as a Root or a Designated Port, it will be placed into a blocking state and not a learning state.)

Forwarding - After another Forward Delay, a port in learning mode will be placed in forwarding mode. Ports in a forwarding state can send and receive all data frames, and continue to build the MAC address table.

Disabled - A port in disabled state has been administratively shut down, and does not participate in STP or forward frames at all.

Standard Parameters: Max Age = 20s Forwarding Delay = 15s Spanning Tree Convergence(Time to change from Blocking to Forwarding) Max Age + 2x Forwarding Delay = 50s

General Topics


33

1.10 Rapid Spanning Tree Protocol RSTP (802.1w) Regular STP (802.1d) provides very slow failure recovery time: 30-60 sec. Thus the STP mechanism was improved, and a new protocol was published: RSTP (802.1w). RSTP offers ~1 sec failure recovery time. How RSTP differs from STP In many aspects STP and RSTP work the same way. They reduce the bridged network to a single spanning tree topology in order to eliminate loops. Either algorithm reactivates redundant connections in the event of a link or component failure. The main difference is convergence time. While STP may take 30 to 50 seconds to re-converge, RSTP does it in dramatically less time. In a carefully designed network, RSTP re-converges in less than a second. Although computation of the Spanning Tree is identical between STP and RSTP, there are differences in the behavior of the two algorithms. The main differences are reported in the following figures

Nokia Siemens Networks

Fig. 31 STP/RSTP differences (1)

General Topics


34



General Topics


35

1.11 Multiple Spanning Tree Protocol MSTP (802.1s) The 802.1D and 802.1w spanning tree protocols operate without regard to a networks VLAN configuration, and maintain one common spanning tree throughout a bridged network. These protocols map one loop-free, logical topology on a given physical topology. In a VLAN environment, the problem could be put in evidence considering the Fig. 34. The figure shows a network of two switches with two configured VLANs. If the switches are running STP or RSTP, all the links for VLAN 2 would be blocked. This is because both STP and RSTP support only a single spanning tree for the whole network and block the redundant links. The above situation can be rectified by using MSTP. The 802.1s Multiple Spanning Tree protocol (MSTP) uses VLANs to create multiple spanning trees in a network, which significantly improves network resource utilization while maintaining a loop-free environment.

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

VLAN 1 VLAN 2

X X

Switch 1 (root Bridge)

Switch 2

Fig. 34 Example of two switches with two configured VLANs

General Topics


36

1.11.1 Multiple spanning tree concepts MST Instance (MSTI) MSTP enables the grouping and mapping of VLANs to different spanning tree instances each with a different root bridge. A MST Instance (MSTI) is a particular set of VLANs that are all using the same spanning tree.

Spanning tree of MSTI= 1 containingvlans 1, 2, 3, 4Spanning tree of MSTI= 2 containingvlans 5, 6, 7, 8Spanning tree of MSTI= 3 containingvlans 9, 10, 11, 12

Same Physical connection

RootBridge

RootBridge

RootBridge

Fig. 35 Different spanning trees created by different MSTIs on the same physical layout

General Topics


42

2.2 MEF: Metro Ethernet Forum The Metro Ethernet Forum (MEF) is a global industry alliance comprising more than 145 organizations. Nokia Siemens Network is part of the MEF The MEF develops technical specifications and implementation agreements to promote interoperability and deployment of Carrier Ethernet worldwide.

Fig. 41 MEF

General Topics


43

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fig. 42 Nokia Siemens Networks is part of the MEF

General Topics


46

2.7 Carrier Ethernet Terminology: Basic Components UNI, EVC and NNI are the Fundamental Constructs of an Ethernet Service

2.7.1 The User Network Interface (UNI) The UNI is the physical interface or port that is the demarcation between the customer and the service provider. The UNI is always provided by the Service Provider The UNI in a Carrier Ethernet Network is a physical Ethernet Interface at operating speeds 10Mbs, 100Mbps, 1Gbps or 10Gbps.

CE: Customer Equipment, UNI: User Network Interface. MEF certified Carrier Ethernetproducts

Carrier Ethernet Network

UNIUNICECE

Fig. 43 User Network Interface

General Topics


47

2.7.2 Network to Network Interface (NNI) NNI is the demarcation between carrier Ethernet networks operated by one or more carriers

UNI: User Network Interface, UNI-C: UNI-customer side, UNI-N network sideNNI: Network to Network Interface, E-NNI: External NNI; I-NNI Internal NNI

Service Provider 1 Carrier Ethernet Network

CECE

UNIUNI

Subscriber Site

ETHUNI-CETH

UNI-CETH

UNI-NETH

UNI-NETH

UNI-NETH

UNI-NETH

E-NNIETH

E-NNIETH

UNI-CETH

UNI-C

UNIUNI

CECE

I-NNII-NNI E-NNIE-NNI

Service Provider 2

I-NNII-NNI

ETHE-NNIETH

E-NNI

Subscriber Site

Fig. 44 UNI and NNI Interfaces

General Topics


49

2.7.3 FlexiPacket UNI / NNI ports In the FlexiPacket Indoor Unit, each Ethernet port (both copper and fiber) can be configured either as UNI (User to Network Interface) or NNI (Network to Network Interface). As default, all ports are configured as NNI. Fig. 45 illustrates a generic network scenario in which UNI and NNI interfaces are highlighted.

IDU -- 1 NNIUNI3rd

party IDU - N3rd

partyNNInetwork UNI

Access to Network Network to AccessNetwork to Network

End-to-end connection

Fig. 45 User to Network and Network to Network Interfaces

In order to provide end-to-end connections, mapping criteria are required at each interface boundary:

Incoming packet arriving at the UNI port is mapped to a specific connection, which is identified by VLAN.

The mapping operation is done once per packet in the network.

After packet is mapped and tagged (VLAN), it already has its association to the service, and on the next hopes (NNI port) mapping is not needed.

General Topics


50

FlexiPacket Radio ODUs are connected to A2200/A1200/First Mile/HUB 800 IDUs by either UNI or NNI ports, as illustrated in Fig. 46, Fig. 47 and Fig. 48.

IDU

NNI

3rd

party

IDU

3rd

party

IDU

3rd

party

NNI NNI

-

NNI

network

NNI

UNI UNI UNI

Fig. 46 FlexiPacket ODU IDU connections by UNI/NNI ports (1)

3rdparty

FP-ODU

IDU

3rd

party

UNI

UNI NNI

FP-ODU FP-ODU


General Topics


51

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

network

IDU

NNIBTS

FP-ODU FP-ODU

UNI


General Topics


52

2.7.3.1 UNI Interface functions Here below are reported the UNI functions

Mapping: performed on the incoming traffic in order to identify the connection it is associated to. Mapping functionality allows associating to all incoming traffic a specific VLAN ID identifying the EVC. The mapping is based on configurable mapping rules, different for each equipment and software releases.

WARNING Please refer yourself to the "HUB Structure chapter" for further details about mapping

TIP Once the mapping has been performed, all the incoming traffic has been associated to a specific EVC. This means that the VLAN tag associated to the Carrier Ethernet service is appended to each frame and it is used across the entire Carrier Ethernet network for delivering the frame towards the destination. This tag is called S-tag.

Manipulation: Manipulation is configurable per EVC. The configuration foresees two options: VID preservation: transparent transport of the incoming frames; no modifications are performed on the incoming frame; in egress the S-VID is removed thus the frame come out the original C-tag; VID translation: removal of the C-tag of the incoming traffic (if present): in case of tagged frames the tag of the incoming frames is overwritten by S-tag; this functionality allows modifying the frame format from that one received at the UNI to a new one suitable for the treatment inside the network.

WARNING Please refer yourself to the HUB Structure chapter for further details about Manipulation

Marking / Policing: the ingress traffic is marked by using 3 bits (Priority Code Point) for defining priority and color.

WARNING Please refer yourself to the HUB Structure chapter for further details about Marking and Policing.

Congestion Management: mechanism used for congestion avoidance by randomly dropping packets according to congestion level (queue fill level), color and priority.

WARNING Please refer yourself to the QoS chapter for further details about Congestion Management

General Topics


54

2.7.4 Ethernet Virtual Connection (EVC) The EVC is the Logical representation of an Ethernet service as defined by the association between 2 or more UNIs. It permits to transfer Ethernet Frames from one site to another one. The EVC prevents data transfer between sites that are not part of the same EVC They are typically distinguished by VLAN tags or Q-in-Q. Three types of EVCs are defined by MEF as reported in Fig. 49, Fig. 50 and Fig. 51:

Point-to-Point, Multipoint-to-Multipoint, Rooted Multipoint (Point-to-Multipoint)

Point-to-Point EVC


CECE UNIUNI

CECEUNIUNI

CECE

UNIUNI

ISPPOP

UNIUNI

Storage Service Provider

Internet

Fig. 49 Point to Point EVC

General Topics


55

Multipoint-to-Multipoint EVC


CECE

UNIUNI

CECE

UNIUNI


Fig. 50 Multipoint to Multipoint

Service Multiplexed

Ethernet UNI

Point-to-Multipoint EVC


CECEUNIUNI

UNIUNI

UNIUNI

CECE

UNIUNI

CECE

Fig. 51 Point to Multipoint EVC

General Topics


56

2.7.5 EVC Basic Service Attributes Details regarding the EVC include:

Bandwidth profiles Class of Service (CoS) Identification Service Performance Frame Delay (Latency) Frame Delay Variation (Jitter)

2.7.5.1 Definition Bandwidth Profiles parameters for policing 4 main parameters are defined to determine the Bandwidth Profiles: two bandwidth limitsCIR and EIRand two burst sizes CBS and EBS. CIR Committed Information Rate: the average rate up to which Service Frames are delivered per the service performance parameters. The CIR is an average rate because all Service Frames are always sent at the UNI speed, e.g., 10Mbps, and not at the CIR, e.g., 2Mbps. EIR Excess Information Rate specifies the average rate up to which Service Frames are admitted into the providers network. The EIR is an average rate because all Service Frames are sent at the UNI speed, e.g., 10Mbps, and not at the EIR, e.g. 8Mbps. PIR Peak Information Rate: = CIR + EIR CBS Committed Burst Size: is the maximum number of bytes (e.g. 2K bytes) allowed for incoming packets to burst above the CIR, but still be marked green. EBS Excess Burst Size: is the maximum number of bytes (e.g. 2K bytes) allowed for incoming packets to burst above the EIR and are marked yellow. When the burst size has been exceeded, packets above the EIR are marked red.

General Topics


57

2.7.5.2 Color Marking A way to describe Service Frames when their average rate is in profile or out of profile is using the colors according to the Fig. 52

Green = conformant to CIR bandwidth profile

Yellow = conformant to EIR bandwidth profile. Yellow packets have higher drop elegibility (will be dropped first in case of congestion).

Performance requirements delay, jitter and loss are not applied to yellow packets within transport network

Red = not conformant and discarded immediately.

CIR Conformant

Traffic CIREIR Conformant

Traffic CIRNo traffic

Traffic EIR

Fig. 52 Color Marking

TIP See more in MEF10.1, section 7.11

General Topics


58

EVC-1

CIR

EIREVC-2

CIR

EIR

EVC-3

CIREIR

Fig. 53

General Topics


59

2.7.5.3 Three Types of Bandwidth Profiles MEF defines three Bandwidths profiles as reported in the example of Fig. 54

Fig. 54 Bandwidths Profiles

General Topics


60

2.8 Carrier Ethernet Service Types Using the EVCs it's possible to support the Ethernet Services Three Ethernet Service types are available as reported in Fig. 55:

E-Line Service Type E-LAN Service Type E-Tree Service Type

E-LINE

E-LAN

E-TREE

Fig. 55 Carrier Ethernet Service Types

General Topics


61

2.9 Circuit Emulation Services over Packet (CESoP) Circuit Emulation Services Enables TDM Services to be transported across Carrier Ethernet network, re-creating the TDM circuit at the far end. They run on a standard Ethernet Line Service (E-Line).

TDM Circuits(e.g. T1/E1/STM Lines)

Carrier Ethernet NetworkTDM Circuits

(e.g. T1/E1/STM Lines)Circuit Emulated

TDM Traffic

Fig. 56 Circuit Emulation Services

General Topics


62

2.9.1 Standards Different standards are available to provide the transport of a TDM service, typically an E1/T1, through a bridged/routed packet network:

IETF RFC5086 (CESoPSN). IETF RFC5087 (TDMoIP), IETF RFC4553 (SAToP) MEF8 (CESoETH). The standard adopted by the 1st release of the FlexiPacket Radio product family was the RFC5086. The A1200 Drop 3 is able to support the MEF8 standard. FM200 and HUB800 release 2 are able to support CESoPSN and SAToP

NSN FlexiPacket IDUs provide the Interworking Function (IWF) to support the initiation and termination of a CESoPSN / SAToP service. The ODU just provide prioritized transport of the packet flows related to the CES service.

CESoPSN Internet Working Function (IWF)

Fig. 57 Internet Working Function

General Topics


63

2.9.2 Pseudowire Pseudowire is a mechanism that emulates the attributes of a TDM service such as an E1, T1 or a fractional nx64 TDM service over a Packet switched network (PSN) TDM pseudowire has to support:

Packetization and Encapsulation of TDM Traffic Packet Delay Variation (PDV) attenuation Frame Loss and Out-of Sequence Packets Clock recovery and Synchronization Packetization and Encapsulation Packetization refers to the process of converting the PDH or SONET/SDH bit stream into Ethernet frames. Specific packet connectivity information is dependent on the type of PSN: Ethernet, MPLS or IP. The encapsulation process places a pseudowire control word in front of the TDM data in order to define the format identifier, to support error flags, length and sequence number (see "Frame Loss and Out-of Sequence Packets" point).

E1/T1Frame

E1/T1FrameEthernet Frames Ethernet Frames

PacketSwitchedNetwork

Header

Fig. 58 from TDM to Packets

General Topics


64

Packet delay variation (PDV) is mainly due to the variable load conditions of network elements and interfaces, randomly occurring in the network. Although priority-based schedulers are implemented in each network element of the FlexiPacket products, still a delay variation is present for high priority packets (such as CESoP packets) passing through a network element. The packet delay variation is compensated by the playout buffer located in the receiving IWF. The basic criterion for dimensioning the playout buffer is to estimate the overall packet delay variation of the network between the initiating and the terminating CESoPSN IWF and to assign the receiving IWF a buffer size more than twice the estimated packet delay variation. Actually the packet delay variation is defined as the difference between the maximum delay of the CESoP packets to be supported without impairments (i.e. without errors or out-of-service conditions on the E1 stream) and their minimum delay. For what concerns the estimation of the total E1 end-to-end delay this will correspond to the network delay of CESoP packets added to the delay provided by the playout buffer.

WARNING The "playout buffer" dimensioning is calculated by means of a proper tool. Please refer yourself to the Annex for detailed information about that.

Frame Loss and Out-of Sequence Packets Frames may occasionally not arrive in the order in which they were sent out. In some cases, the frames may arrive very late or not at all, resulting in frames being discarded. TDM and SONET/SDH networks don't have the concepts of resending frames hence such frames are considered lost if they are not received within the window of the jitter buffer at the destination. The destination must have the ability to re-sequence the arriving frames. This is achieved through the use of sequence numbers within the headers.

General Topics


65

Clock recovery and Synchronization In the PDH network, the difference between in clock frequencies between TDM links is compensated for using bit stuffing technologies. With a packet network, that connection between the ingress and egress frequency is broken, since the packets are discontinuous in time. The consequence of a long-term mismatch in frequency is that the queue at the egress of the packet network will either fill up or empty. For this reason particular techniques such as "Differential Clock Recovery" and "Adaptive Clock Recovery" must be implemented.

WARNING About Clock recovery and synchronization please, refer to the chapter "Synchronization"

General Topics


66

Different pseudowires are available according to the different standards: CESoPSN (Circuit Emulation over PSN) Pseudowire CESoPSN Pseudowire is able to transmit emulated structured TDM signals. That is it can identify and process the frame structure and transmit signaling in TDM frames A benefit of CESoPSN is that unused timeslots are not transported in the payload, thereby saving on bandwidth. CESoPSN provides three encapsulation modes:

IP/UDP (IP over User Datagram Protocol : solution actually adopted in FlexiPacket

MPLS (Multi-Protocol Label Switching) L2TPv3 (layer 2Tunneling Protocol Version 3: alternative protocol to MPLS) TDMoIP Pseudowire The main difference between TDMoIP and CESoPSN is that the first packetizes TDM data in multiples of 48 bytes while the second uses multiples of the TDM frame itself. TDMoIP provides the same encapsulation modes as CESoPSN and the pure Ethernet encapsulation SAToP (Structure Agnostic TDM over Packet) Pseudowire SAToP differs from the previous Pseudowires technologies because it treats the TDM traffic as a data stream and ignores the framing or the timeslots. SATOP provides the same encapsulation modes as CESoPSN CESoETH (CES over Ethernet) Pseudowire CESoETH define TDM Circuit Emulation packets encapsulated by bare Ethernet. Emulated TDM CS data is distinguished based on the Emulated Circuit Identifier (ECID).

General Topics


67

2.10 FlexiPacket EVC and Services NSN FlexiPacket IDUs provide Ethernet Virtual Connections (EVC), each one associated to a service. Each service initiates at the ingress and terminates at the egress of a network, running over both NNI and UNI ports.

WARNING Since the mapping of traffic into connections / services is performed on UNI ports only, both the initiation and termination of a service is possible on UNI ports only (see Fig. 59).

NNIUNI3rd

party3rd

partyNNInetwork UNI

Access to Network Network to Network

End-to-end connection

FlexiPacketIDU

FlexiPacketIDU

Access to Network

Fig. 59 User to Network and Network to Network Interfaces

Three types of Services are supported by FlexiPacket IDU:

CESoP (Circuit Emulation Service over Packet) SAToP (Structure Agnostic TDM over Packet; it's implemented in FM200 R2.0 and

HUB800 R2.0)

CESoETH (CES over Ethernet) pseudowire; its implemented in A1200 release 5.0 Drop 3

E-line it is based on point-to-point EVC, running end-to-end between UNI

ports. A unique VLAN ID is reserved in the network to identify each E-line service.

E-LAN it is based on multipoint-to-multipoint EVC. In A1200 and A2200

Release 4.5, only one management E-LAN can be defined and it identifies the management domain between FPR and A2200/A1200 devices. A unique VLAN ID, VIDMGT, is reserved for the management E-LAN service (default value = 127). Forwarding is based on bridge functionality. Destination MAC address is used to reach the target.

General Topics


68

WARNING In FPH-2200 Release 5.0 and FPH-1200 Release 5.0 Drop3 is possible to manage E-LAN services via CLI and Web UI.

WARNING In FPFM-200 and HUB 800, both E-Lines and E-LANs can be configured; one E-LAN is reserved for the management/DCN service. By default, this service is identified by (VLAN ID=127).

In Fig. 60, E-Lines and E-LAN (management) examples are shown. At UNI:

Mapping of traffic to the Service Assignment to a Class of Service Policing (CIR /EIR) according to SLA CE-VLAN manipulation (transparent/translation) At NNI:

Traffic of a Service is identified by a VLAN ID

NNI

UNI

UNI

DCN

Untaggedframes

3rd

party

untagged framesUNI

3rdparty

E-line 1

UNI

3rd

party

NNI NNI

E-line 2

E-line 3

E-line 4

NNI

Packetnetwork

E-LAN

NMS

IDU IDU IDU

Fig. 60 FlexiPacket E-Lines and E-LAN Example

General Topics


134

8.3 Timing-over-Packet (ToP) IEEE1588 v2 (official Title: Precision Time Protocol)

With this technique, Network clocks are organized in Master-Slave hierarchy. A two way timing exchange will be established where the Master sends messages to its slaves to initiate synchronization. Each slave then responds to synchronize itself to its Master. This sequence is repeated throughout the specific network to achieve and maintain clock synchronization.

The ToP Master transmits timing packets over the asynchronous data path The ToP Slave recovers timing from the timing packets Timing packets are time stamped at the start of frame (SOF) of the corresponding Ethernet packet. Timing packets can transparently traverse both Layer 3 and Layer 2 networks. Using IEEE1588, it is possible to synchronize, in the sub-microsecond range, the local clocks using the same Ethernet network that also transports the process data. No special requirements are placed on memory or CPU performance, and only minimal network bandwidth is needed. The low administration effort for this protocol is also significant. As redundant masters are also supported, a PTP domain automatically configures itself using the best master clock algorithm and is also fault-tolerant. A Master-Slave connection is reported in Fig. 105 where the External Reference Synch could be a Signal coming from a PRC or from a GPS system.

General Topics


135

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1GbEPHY

1GbEPHY

Master ToPEngine

PLL

External Reference Clock

Slave ToPEngine

PLL

Data Packets Timing Packets

Master Slave

Fig. 105 IEEE1588 Master Slave Connection

General Topics


140

8.3.2 Precision Time Protocol (PTP) Clocks

Grandmaster Clock The ultimate source of time on the network is called Grandmaster. Grandmasters are typically referenced to GPS or PRC so that they are both very stable and very accurate. A grandmaster time stamps PTP packets with very high time stamp accuracy. A grandmaster has to be able to support hundreds or thousands of PTP clients. This is usually made possible in part by sending "PTP Synch" and "Follow Up Messages" periodically using multicast addressing, and in part by being able to quickly and accurately process PTP client initiated "Delay Request" and "Delay Response messages".

TIP Nokia Siemens Networks has selected "Symmetricom", a leading company in synchronization solutions, to become its first supplier for IEEE 1588v2 masters.

Ordinary Clock Ordinary clock has a single PTP port in a domain and maintains the time scale used in the domain.

TIP The PTP Domain is a logical grouping of PTP clocks that synchronize to each other using the PTP protocol, but that are not necessarily synchronized to PTP clocks in another domain.

It may provide time to an application or and device.

Boundary Clock Boundary clock (see Fig. 109) has multiple PTP ports in a domain and maintains the timescale used in the domain. It may serve as a source of time, i.e., be a master, or may synchronize to another clock, i.e., be a slave. It may provide time to an application. A boundary clock that is a slave has a single slave port, and transfers timing from that port to the master ports.

General Topics


141

Grandmaster

BoundaryClock

Ordinary Clock

M

S Ordinary ClockS

2MHz/2Mpbs

GPS

S

M M

Fig. 109 Boundary Clock

M M M

Switch with Grandmasterfunction

2MHz/2Mpbs

GPS

Switch with Boundaryfunction

Switch with Boundaryfunction

S

S

OrdinaryClock

OrdinaryClock

S S

M

OrdinaryClock

S

OrdinaryClock

S

OrdinaryClock

S

M

M M

Fig. 110 IEEE 1588 System Configuration

General Topics


151

10 Digital Radio Relay Signals

General Topics


152

10.1 Quadrant Amplitude Modulation (QAM) Fig. 119 represents a generic Quadrant Amplitude Modulation (QAM). The bit rate defines the rate at which information is passed. The Intermediate Frequency (IF) is the Modulator Output Each symbol represents "N" bits, and has "M" signal states, where "M = 2N". The symbol rate is the rate at which the carrier moves from one point in the constellation to the next point

QAM Modulator

Bit Rate

Intermediate frequency

Symbol Rate =Bit Rate

N

04 QAM N = 2 M = 4 16 QAM N = 4 M = 16 64 QAM N = 6 M = 64

128 QAM N = 7 M = 128 256 QAM N = 8 M = 256

Signal States in the Constellation = M

I

Q1

2

3

12

3

Time

QAM Constellation with M = 16

QAM Signal versus Time

Fig. 119 QAM (1)

General Topics


153

From Fig. 120 to Fig. 122, different QAM Modulations are shown. As reported in Figures, the Phase and Amplitude can easily represented in vector co-ordinates as a discrete point in the I-Q Plane where I stands for in-phase (i.e. phase reference and Q stands for Quadrature (i.e. 900 out of phase). Increasing the modulation levels, more information is transmitted (bits associated to the signal state) As the number of modulation stages increases, the requirements concerning linearity and low AM/PM conversion of all the stages used also rise sharply. This may lead to decrease the Tx Output Power in order to increase the TX amplifier linearity.

16QAM

I

Q

4QAM = 4PSK

Symbol Rate = Bit Rate/2

Symbol Rate = Bit Rate/4I

Q

Fig. 120 QAM (2)

General Topics


154

64QAM

Q

I Symbol Rate = Bit Rate/6

128QAMI

Q


Fig. 121 QAM (3)

General Topics


155

256QAM

Q

I


Fig. 122 QAM (4)

256QAM128QAM64QAM32QAM16QAM4QAM

FlexiPacket MultiRadio Supported Modulations

256QAM128QAM64QAM16QAM4QAM

FlexiPacket Radio Supported Modulations

Fig. 123 FlexiPacket Radio/MultiRadio supported Modulations

General Topics


162

10.3 Adaptive Modulation The concept of Dynamic Modulation rises when thinking about the compromise between the planned Microwave dimensioning (that has to take availability and performances into consideration) and the need for more capacity. Usually Microwave link is considered to work in normal conditions and to provide good performances (according to Standards), and being unavailable or giving poor performances for a certain percentage of time, due to fading or bad propagation conditions (typically rain, affecting propagation in frequency bands above 15 GHz). In planning phase, the link is engineered (frequency, bandwidth/modulation, capacity, antenna diameter) to meet the worst case, but this way the link capacity is under utilized for most of the operating time. Thus, basically Dynamic Modulation introduces a way to transmit more capacity with higher modulation formats when the propagation conditions are good, and switch to more robust modulation formats in case of fading phenomena to preserve high priority traffic (i.e. voice vs Data/Video). For basic and delay sensitive service (voice), the basic capacity can be considered guaranteed, allowing Data to exploit the rest of additional capacity provided, as shown in Fig. 132.

Fig. 132 Dynamic Modulation

General Topics


163

10.3.1 FlexiPacket ODU Adaptive Modulation Five different profiles (from 4QAM to 256QAM) are available inside the FlexiPacket Radio and 6 profiles in the FlexiPacket MultiRadio 2.1. The switching criteria to pass from a modulation to another one is based on the Mean Square Error (MSE) estimation This parameters is dependant from the received signal level and modulation type.

Capacity

16 QAM

4 QAM

64 QAM

128 QAM

FPR ACM Switching CriteriaThe switching criteria is based on the Mean Square Error (MSE) estimationThis parameters is dependant from the received signal level and modulation type

Rx Level

256 QAM

MostValuableTraffic

High Priority

Services

Max ThroughputAll services transported

Hitless Switchfor Speed of

Attenuation up to 50dB/s

Fig. 133 FlexiPacket Radio Adaptive Modulation (1)

001. general topics.pdf

Documents