03 ft48923 en02gla0_general topics_

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Content
1 LAN and VLAN: some considerations 3
1.1 Definitions 4
1.2 Domains in a traditional LAN 5
1.3 Domains in a VLAN 9
1.4 Traffic separation by VLAN 12
1.5 Tagging 13
1.6 VLAN Aware / Unaware 21
1.7 Links Types 22
1.8 Q-in-Q 25
1.9 Spanning Tree Protocol (802.1d) 29
1.10 Rapid Spanning Tree Protocol RSTP (802.1w) 32
1.11 Multiple Spanning Tree Protocol MSTP (802.1s) 33
2 Carrier Ethernet: Some Concepts 39
2.1 What is Carrier Ethernet 39
2.2 MEF: Metro Ethernet Forum 40
2.3 Cooperation with Other Standard Bodies 42
2.4 IEEE: Institute of Electrical and Electronics Engineers 42
2.5 IETF: The Internet Engineering Task Force 42
2.6 ITU: International Telecommunication Union Telecommunication
Standardization Sector 43
3 Carrier Ethernet Terminology 45
3.1 Basic Components 46
3.2 Carrier Ethernet Service Types 63
3.3 Circuit Emulation Services over Packet (CESoP) 64
3.4 FlexiPacket EVC and Services 71
4 Quality of Service in the HUB 75
4.1 QoS Mechanism 76
4.2 Classifier and Packet Marker 79
4.3 Policer 83
General Topics

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4.4 Buffer Manager: Congestion Avoidance 86
4.5 Queue Scheduler 89
5 Quality of service in the FlexiPacket Radio Rel.1.3 EP1 99
5.1 Quality of Service Mechanism 99
5.2 Classification 100
5.3 Egress Scheduling 102
6 Quality of service in the FlexiPacket MultiRadio Rel 2.1 103
6.1 Quality of Service Mechanism 103
6.2 QoS Classification Criteria 104
6.3 Egress Scheduling 104
7 Ethernet OAM 105
7.1 OAM Definition 106
7.2 OAM Layers 107
7.3 Ethernet Link Fault Management OAM (EFM OAM) 802.3ah 111
7.4 Connectivity Fault Management (CFM) – 802.1ag 112
7.5 Performance Monitoring - ITU-T Y.1731 120
7.6 E2E OAM – Ethernet AIS 124
7.7 Remote Defect Indication (RDI) 125
8 Network Synchronization 127
8.1 Introduction 128
8.2 Physical Layer Synchronization – Synchronous Ethernet (SyncE) 129
8.3 Timing-over-Packet (ToP) IEEE1588 v2 (official Title: Precision Time
Protocol) 136
8.4 IEEE-1588 and Synchronous Ethernet 146
8.5 FlexiPacket Synchronization 148
9 CESoP Clock Recovery 151
9.1 Clock Recovery 152
9.2 CESoP with Differential Clock Recovery 153
10 Digital Radio Relay Signals 155
10.1 Quadrant Amplitude Modulation (QAM) 156
10.2 Filtered Spectrum 160
10.3 Adaptive Modulation 166

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1 LAN and VLAN: some considerations

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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)

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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)

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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

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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

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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

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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 2 Broadcast
Damain
VLAN 1 Broadcast
Domain
VLAN 1 Broadcast
Domain
L2 SWITCH L2 SWITCH
Fig. 5 Domains in a VLAN (1)

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ROUTERS are necessary only to make possible communication between different
VLANs.
VLAN IS A LOGICALLY DEFINED BROADCAST DOMAIN.
VLAN 2 Broadcast
Damain
VLAN 2 Broadcast
Damain
VLAN 1 Broadcast
Domain
VLAN 1 Broadcast
Domain
L2 SWITCH L2 SWITCH
ROUTER

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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

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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

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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 DA
6 bytes
Payload
46-1500 bytes
FCS
4 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 SA
6 bytes
Length/Type
2 bytes
VLAN tags may be added here
Preamble
+SD
8 bytes
Interframe
Gap
12 bytes
64-1518 bytes
Fig. 9 IEEE 802.3 Untagged Frame

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C
F
I
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 <= 4094)
4 bytes are added in the Ethernet frame between the MAC Source Address and
the Type-Field.
802.1Q – VLAN (single tagged)
MAC DA
6 bytes
Payload
48-1500 bytes
FCS
4 bytes
MAC SA
6 bytes
Length/Type
2 bytes
Preamble
+SD
8 bytes
Interframe
Gap
12 bytes
Payload
48-1500 bytes
FCS
4 bytes
Length/Type
2 bytes
Interframe
Gap
12 bytes
MAC DA
6 bytes
MAC SA
6 bytes
Preamble
+SD
8 bytes
TPID TCI
Fig. 10 802.1Q Single Tagged Frame (1)

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Is used to uniquely identify the VLAN to which the
frame belongs. There can be a maximum of 212 -1
VLANs. Zero is used to indicate no VLAN ID
Vlan IDentifier
Always 0 if Ethernet.It is used to make
compatibility between Ethernet and Token Ring
Canonical Format Indicator
It allows priority information to be encoded in the
frame. Eight levels of priority are allowed
Priority Code Point (PCP)
It Indicates that it will follow a 802.1q TAG and
not the payload; the Default TPID value in IEEE
802.1Q, is 0x8100
Tag Protocol IDentifier
DESCRIPTIONTC FIELD
Fig. 11 802.1Q Single Tagged Frame (2)

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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 frame’s 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.

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The TRAFFIC CLASSES are assigned to separate queues with different priorities.
Traffic classes
queues
map to
outgoing
Priority bits
Fig. 13 Quality Of Service IEEE 802.1p (2)
If a switch provides 8 queues for the 8 priorities settings, each queue will store
frames with a specific priority setting to provide complete differentiated services.
Fig. 14 Switch with 8 queues; each priority has one queue

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

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To minimize costs, however, fewer queues may be provided in such switches.
Frames from several priority settings may be stored together in one queue.
Fig. 16 Switch with less than 8 queues; more than one priority in one queue

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

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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
FrameFrame
FrameFrame
FrameFrameFrameFrameFrameFrame
FrameFrame
TAG
added/removed
L2-Switch L2-Switch
VLAN aware
Bridge/L2-Switch
VLAN aware
VLAN unaware stations
Bridge/L2-Switch
Fig. 19 VLAN Aware/Unaware

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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

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L2-Switch
L2-Switch
Trunk Link
Trunk Link
VLAN-aware Workstation
VLAN-aware
Bridge/L2-Switch
VLAN-aware
Bridge/L2-Switch
Fig. 21 Trunk Link

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L2-Switch
Access Link
VLAN-unaware Device
VLAN-aware
Bridge/L2-Switch
Fig. 22 Access Link

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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

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Double TAG VLAN Tag Control Identifier (TCI) is reported in Fig. 24
DA SA TPID TAG
LEN/
Etype Data FCSTPID TCI
2 2
Double Tagged Ethernet Frame
User Priority
Priority Code Point
DEI
S-VID
Service 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

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Double Tag Example
S-VLAN 2
C-VLAN 2
A
D
C
E
B
2
3
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
x
1S-VLAN 4
C-VLAN 2
1
2
S= Service Provider
C= Customer
Fig. 25 Double TAG Example

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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.

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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 (BPDU’s) 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

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In case of link failure, BPDU’s are again exchanged in the network to notify tree of
the topology change.
Redundant routes are enabled.
Root Bridge
Fig. 27

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1.9.2 Spanning Tree Port roles
Spanning Tree port roles are:
• Root port: pointing towards the root bridge.
• Designated port: active ports that aren’t root ports.
• Alternate port: one side of a blocked link (the other side is designated).
Root Bridge
R
R
R
R D
D
D
D
D
D
A
A
Fig. 28

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1.9.3 Spanning Tree Port states
Spanning Tree Port states are:
• Forwarding: all frames are forwarded on the port.
• Discarding: all user data is dropped. BPDUs are forwarded.
• Learning: Port is still inactive, but learns MAC addresses.
Root BridgePort role: Root
Port state: Forwarding
Port role: Root
Port state: Forwarding
Port role: Alternate
Port state: Discarding
Fig. 29
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.

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1.11 Multiple Spanning Tree Protocol MSTP (802.1s)
The 802.1D and 802.1w spanning tree protocols operate without regard to a
network’s 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.
30.
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. 30 Example of two switches with two configured VLANs

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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 containing
vlans 1, 2, 3, 4
vlans 5, 6, 7, 8
vlans 9, 10, 11, 12
Same Physical connection
Root
Bridge
Root
Bridge
Root
Bridge
Fig. 31 Different spanning trees created by different MSTIs on the same physical layout

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Regions
A MST region is a set of interconnected switches that all have the same values for
the following parameters:
• MST configuration name: the name of the MST region
• Revision level: the revision number of configuration (The revision level is an
arbitrary number that you assign to a MST region. It can be used to keep track of
the number of times that MST configuration has been updated for the network. If
the revision level is not set explicitly by the command, the default revision level
value will be 0.
• Configuration Digest: the mapping of which VLANs are mapped to which MST
instances
Each MST instance created is identified by an MSTI number. This number is locally
significant within the MST region. Therefore, a MSTI will not span across MST
regions.
MSTI1
MSTI2
MSTI3
MSTI4
MSTI2
MSTI4
The MSTI2 in Region 1 is unrelated to the MSTI2 in Region 3 and the MSTI4 in Region 2 is unrelated to
the MSTI4 in Region 3.
Region 1
Region 2
Region 3
Same Physical
Connection
Fig. 32 MSTIs in different regions

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Common and Internal Spanning Tree (CIST)
The CIST is the default spanning tree instance of MSTP, i.e. all VLANs that are not
members of particular MSTIs are members of the CIST.
Also, an individual MST region can be regarded a single virtual bridge by other MST
regions.
The spanning tree that runs between regions is the CIST. The CIST is also the
spanning tree that runs between MST regions and Single Spanning Tree (SST)
entities.
So, in Fig. 33, the STP that is running between the regions, and to the Single
Spanning Tree bridges, is the CIST.
MSTP
Region 1
MSTP
Region 2
MSTP
Region 3
Switch non MSTP capable
= CIST
Fig. 33 Common and Internal Spanning Tree (CIST)

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Returning now to the example of Fig. 30, the problem can be solved mapping
VLAN 1 and VLAN 2 to different MSTIs.
The MSTP configures separate spanning tree for VLANs 1 and 2 and blocks the
redundant links for VLAN 2.
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
VLAN 1 VLAN 2
X
Switch 1
(root Bridge)
Switch 2
MSTI1= VLAN1
MSTI2= VLAN2
Fig. 34 Active topologies for MSTI 1 and MSTI 2
1.11.2 Load Balancing
We have seen that with MSTP, each spanning tree instance can include one or more
VLANs and applies a separate, per-instance forwarding topology.
This means that where a port belongs to multiple VLANs, it may be dynamically
blocked in one spanning tree instance, but forwarding in another instance.
This achieves load-balancing across the network while keeping the switch’s CPU
load at a moderate level (by aggregating multiple VLANs in a single spanning tree
instance).

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2 Carrier Ethernet: Some Concepts
2.1 What is Carrier Ethernet
Carrier Ethernet is the use of high-bandwidth Ethernet technology for Internet access
and for communication among business, academic and government local area
networks (LANs).
The use of Carrier Ethernet technology within a metropolitan area network (MAN) is
known as Metro Ethernet.
Fig. 35 What's Carrier Ethernet

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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. 36 MEF

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Fig. 37 Nokia Siemens Networks is part of the MEF

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2.3 Cooperation with Other Standard Bodies
The goal of the MEF is to create Implementation Agreements (IAs) that leverage
existing standards defined by other organizations such as IEEE, ITU-T and IETF
rather than creating competing standards. Where necessary, the MEF will:
• make recommendations to existing standards bodies. MEF has liaisons to IEEE
and ITU-T. MEF also works closely with IETF.
• As a last resort, create standards that are not being developed by other standards
bodies.
2.4 IEEE: Institute of Electrical and Electronics
Engineers
The IEEE, a non- profit organization, is the world's leading professional association
for the advancement of technology.
The IEEE is a leading developer of international standards that underpin many of
today's telecommunications, information technology and power generation products
and services.
2.5 IETF: The Internet Engineering Task Force
The IETF is the principal body engaged in development of new Internet standard
specifications.
It is a large open international community of network designers, operators, vendors
and researchers concerned with the evolution of the Internet Architecture and the
smooth operation of the Internet.
Its mission includes:
• identifying and proposing solutions to operational and technical problems in the
Internet;
• specifying the development or usage of protocols and near-term architecture to
solve such technical problems for the Internet;
• making recommendations to the Internet Engineers Steering Group (IESG)
regarding the standardization of protocols and protocol usage in the Internet;
• Providing a forum for the exchange of information within the Internet community
between vendors, users, researchers, agency contractors and network managers.

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2.6 ITU: International Telecommunication Union
Telecommunication Standardization Sector
The ITU is an international organization under the United Nations within which
government and the private sector coordinate global telecom networks and services.
ITU-T: Telecommunication Standardization Sector
The main products of ITU-T are the Recommendations. At present, more than 3,000
Recommendations (Standards) are in force.
Recommendations are standards that define how telecommunication networks
operate and interwork.
ITU-T Recommendations are non-binding, however they are generally complied with
due to their high quality and because they guarantee the interconnectivity of networks
and enable telecommunication services to be provided on a worldwide scale.

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3 Carrier Ethernet Terminology

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3.1 Basic Components
UNI, EVC and NNI are the Fundamental Constructs of an Ethernet Service
3.1.1 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 Ethernet
products
Carrier Ethernet
Network
UNIUNI
CECE
Fig. 38 User Network Interface

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3.1.2 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 side
NNI: Network to Network Interface,
E-NNI: External NNI;
I-NNI Internal NNI
Service Provider 1 Carrier Ethernet
Network
CECE
UNIUNI
Subscriber
Site
ETH
UNI-C
ETH
UNI-C
ETH
UNI-N
ETH
UNI-N
ETH
UNI-N
ETH
UNI-N
ETH
E-NNI
ETH
E-NNI
ETH
UNI-C
ETH
UNI-C
UNIUNI
CECE
I-NNII-NNI E-NNIE-NNI
Service Provider 2
I-NNII-NNI
ETH
E-NNI
ETH
E-NNI
Subscriber
Site
Fig. 39 UNI and NNI Interfaces

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3.1.3 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. 40 illustrates a generic network scenario in which UNI and NNI interfaces are
highlighted.
IDU -- 1 NNIUNI3rd
party
IDU - N
3rd
party
NNI
network UNI
Access to Network
Network to AccessNetwork to Network
End-to-end connection
Fig. 40 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.

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FlexiPacket Radio ODUs are connected to A2200/A1200/First Mile IDUs by either
UNI or NNI ports, as illustrated in Fig. 41, Fig. 42 and Fig. 43.
IDU
NNI
3rd
party
IDU
3rd
party
IDU
3rd
party
NNI NNI
-
NNI
A2200/1200
network
NNI
UNI UNI UNI
Fig. 41 FlexiPacket Radio –IDU connections by UNI/NNI ports (1)
3rd
party
FPR
IDU
3rd
party
UNI
UNI NNI
FPRFPR

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network
IDU
NNI
BTS
FPR FPR
UNI

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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

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• Queuing, Shaping (per port) and Scheduling
 5 queues per port in A1200/A200 and 8 queues in FPFM 200/HUB 800
 both Strict Priority (SP) and Weighted Round Robin (WRR) are mixed
for scheduling
WARNING
Please refer yourself to the QoS chapter for further details about Queuing and
Scheduling
• Per Hop Behavior decoding: by configuration it is possible to replace Priority
Code Point bits with new values in order to give different marking.

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NNI Interface functions
Here below are reported the UNI functions:
• Congestion Management
• Queuing, shaping (port) and scheduling
• Per Hop Behavior (PHB) Decoding: by configuration it is possible to replace PCP
bits with new values in order to give different marking.
The egress traffic flowing from the network to the access is already mapped to a
specific service. Therefore the mapping function is no more needed.

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3.1.4 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. 44, Fig. 45 and Fig. 46:
• Point-to-Point,
• Multipoint-to-Multipoint,
• Rooted Multipoint (Point-to-Multipoint)
Point-to-Point EVC
Carrier Ethernet
Network
CECE
UNIUNI
CECE
UNIUNI
CECE
UNIUNI
ISP
POP
UNIUNI
Storage Service Provider
Internet
Fig. 44 Point to Point EVC

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Multipoint-to-Multipoint EVC
Carrier Ethernet Network
CECE
UNIUNI
CECE
UNIUNI
Fig. 45 Multipoint to Multipoint
Service
Multiplexed
Ethernet UNI
Point-to-Multipoint EVC
Carrier Ethernet
Network
CECE
UNIUNI
UNIUNI
UNIUNI
CECE
UNIUNI
CECE
Fig. 46 Point to Multipoint EVC

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3.1.5 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)
3.1.5.1 Definition Bandwidth Profiles parameters for policing
4 main parameters are defined to determine the Bandwidth Profiles:
two bandwidth limits—CIR and EIR—and 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 provider’s 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.

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3.1.5.2 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. 47
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 ≤ CIR
EIR Conformant
Traffic ≥ CIR
No traffic
Traffic ≥ EIR
Fig. 47 Color Marking
TIP
See more in MEF10.1, section 7.11

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EVC-1
CIR
EIR
EVC-2
C
IR
EIR
EVC-3
CIREIR
Fig. 48

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3.1.6 Three Types of Bandwidth Profiles
MEF defines three Bandwidths profiles as reported in the example of Fig. 49
Fig. 49 Bandwidths Profiles

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3.2 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. 50:
• E-Line Service Type
• E-LAN Service Type
• E-Tree Service Type
E-LINE
E-LAN
E-TREE
Fig. 50 Carrier Ethernet Service Types

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3.3 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)
TDM Circuits
(e.g. T1/E1/STM Lines)
Circuit Emulated
TDM Traffic
Fig. 51 Circuit Emulation Services

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3.3.1 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.
WARNING
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. 52 Internet Working Function

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3.3.2 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/T1
Frame
E1/T1
FrameEthernet Frames Ethernet Frames
Packet
Switched
Network
Header

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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.

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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"

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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).

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3.4 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. 54).
NNIUNI3rd
party
3rd
party
NNI
network UNI
Access to Network Network to Network
End-to-end connection
FlexiPacket
IDU
FlexiPacket
IDU
Access to Network
Fig. 54 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)
• 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.

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WARNING
In FPH-A1200 Release 5.0 drop 2, only one E-LAN can be configured and it is
reserved for the management/DCN service. By default, this service is identified
by (VLAN ID=127). In FPH-2200 Release 5.0 is also 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. 55, 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
Untagged
frames
3rd
party
untagged frames
UNI
3rd
party
E-line 1
UNI
3rd
party
NNI NNI
E-line 2
E-line 3
E-line 4
NNI
Packet
network
E-LAN
NMS
IDU IDU IDU
Fig. 55 FlexiPacket E-Lines and E-LAN Example

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In Fig. 56, FlexiPacket CES and E-Line Services are shown.
2G
3G
3G
2G3G
2G
3G
Tail Site 2G+3G
Chain Site 2G+3G
Tail Site 3G
MW Hub Site
Packet i/f
CES : Circuit Emulation Service
•E1 over Ethernet via Pseudo Wire Emulation
•Higher priority in the network
UNI
UNI
E-Line
•Point to point service for Ethernet traffic
•Configurable Committed and Peak data Rate
•Basic entity for traffic provisioning and monitoring
TDM i/f
Fig. 56

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4 Quality of Service in the HUB

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4.1 QoS Mechanism
Quality of Service Mechanism implemented in the HUB includes (Fig. 57):
• Classifier and Packet Marker
a) Classifier makes the association EVC ↔ CoS based on settable "Classification
Rules".
b) Packet Marker marks QoS level at packet header (Green = conformant to CIR
bandwidth profile; Yellow = conformant to EIR bandwidth profile; Red = not
conformant and discarded immediately).
• Policer:
Protecting network resources by preventing usage in excess of guaranteed
bandwidth (bps), i.e. compare incoming traffic rate with Traffic Profile
• Buffer manager:
Congestions avoidance mechanisms
• Queue Scheduler:
decide which packet forward first based on its priority
WARNING
A way to describe Service Frames when their average rate is in profile or out of
profile is using the colors.
Packet colors are:
Green = conformant to CIR bandwidth profile
Yellow = conformant to EIR bandwidth profile
Red = not conformant and discarded immediately
Green or yellow color is marked into packet (Priority Code Point PCP bits) and
it will be carried to next phases in network.

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.....
.....
Queue Scheduler
Meter
Dropper
Policer
#1
Marker
Meter
Dropper
Policer
#2
Marker
Meter
Dropper
Policer
#3
Marker
Meter
Dropper
Policer
#N
Marker
Output Port
PacketMarker
Scheduler
Q1
Q2
Q3
Qn
ClassifierandPacketMarker
BufferManager
Fig. 57 QoS Process Internal View

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4.2 Classifier and Packet Marker
Classification is based on the Service Level Agreement (SLA) set up between the
service provider and the user. Traffic is classified in different priorities.
FlexiPacket Hub A1200/2200 Classification Criteria are characterized as following:
• Only one per-EVC basis criterion: each EVC is associated to a Class of Service
(CoS). The same classification criteria foreseen for the EVC mapping are still valid
for the CoSs mapping.
• Apply Customer Priority (ACP): this feature allows the user to flow traffic of
different priorities over the same service, all sharing the service's BW. When
enabled, packets for the service should be assigned with a Priority Code Point
(PCP) according to the C-Tag priority value and the customer priority decode
table.
FlexiPacket FirstMile-200 and HUB 800 also support two types of classification
criteria:
• Per EVC: each EVC is associated to a CoS.
• Multi-CoS: traffic belonging to the same EVC can be split in several CoSs.
Once the CoS has been identified, the PCP field of the VLAN tag associated to the
service is properly marked.
The PCP values will be used by the schedulers to select the proper queue.
PCP values to be associated to the CoSs are configurable in FPFM200 and HUB
800.
The association between CoS and PCP in FlexiPacket First Mile 200 and in the
FlexiPacket HUB 800 is reported in Fig. 58.
The association between CoS and PCP is fixed in A1200/A2200 and is reported in
Fig. 59.
Each queue is associated to a specific identification string (reported in the following
pictures); such identification string derives from the standard nomenclature
associated to the Differentiated Services (DiffServ) architecture specified by the
IETF.
IETF defines a set of six CoSs (in order of decreasing priority): EF, AF4, AF3, AF2,
AF1, BE.

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Some considerations about FPH-x200 respect to IETF architecture
FPH-x200 does not consider the entire set of identifiers:
It does not foresee the AF4 ID;
It foresees the additional EF1 ID;
FPH-x200 uses an opposite order of priorities for AFx classes:
AFx ID is associated to an higher priority with respect the AFx+1ID (i.e. in order of
decreasing priority AF1, AF2, AF3);
WARNING
In FPH-x200, traffic associated to the same CoS is handled in the same queue,
but with different discarding eligibility as reported in Fig. 59.

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0Queue 0: SP/WFQBest EffortsBE
1Queue 1: SP/WFQcontrolAF
2Queue 2: SP/WFQNormalAF3
3Queue 3: SP/WFQBusiness CriticalAF2
4Queue 4: SP/WFQControlAF1
5Queue 5: SP/WFQControlEF
6Queue 6: SP/WFQCESEF1
7Queue 7: SP/WFQDelay SensitiveEF2
PCPTreatment
(programmable)
ServiceIdentification
String
EF= Expedited Forwarding
AF= Assured Forwarding
Fig. 58 association between CoSs and PCP in FlexiPacket First Mile 200 and FlexiPacket HUB 800
1 (green)
0 (yellow)
Queue 0: WFQBest EffortsAF3
3 (green)
2 (yellow)
Queue 1: WFQBusiness CriticalAF2
5 (green)
4 (yellow)
Queue 2: WFQManagementAF1
6 (green)Queue 3: SPDelay SensitiveEF2
7 (green)Queue 4: SPCESEF1
PCPTreatment
(Fix)
ServiceIdentification
String
EF= Expedited Forwarding
AF= Assured Forwarding
Fig. 59 association between CoSs and PCP in A1200/A2200

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The characteristics of the classes are:
• EF1
 Lowest delay and delay variation
 No packet loss
 Similar to DiffServ Expedited Forwarding
 Usually reserved for Circuit Emulation Service (TDM services)
 May be used for Voice
• EF2
 Low delay, delay variation, and no packet loss
 Used for Voice, Video, other real-time application
• AF1
 Low packet loss
 Reserved for internal network control traffic (OSPF, configuration, download
etc.)
• AF2
 Lower delay and packet loss than Normal Data
 Better excess BW treatment than Normal Data
 Similar to DiffServ Assured Forwarding
• AF3
 Not just Best effort – may still have guaranteed BW
• BE
 Best Effort

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4.3 Policer
The Meter (Fig. 60) measures incoming traffic (bps), compares it with traffic profile
and sends the results (Conform, Exceed, Violate) to the "Policer Action".
Policer Actions decisions are:
• Pass: Forwarding packet
• Mark : Change value of L2 802.1p (Marker block in Fig. 60 )
• Drop: Discarding packet (Dropper block in Fig. 60)
Meter
Policer
Packet
In
Packet
Out
Dropper
Marker
Fig. 60 Policer

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4.3.1 Meter Algorithm: Two rate - three color marker (trTCM)
A token bucket analogy is used to describe the algorithm that performs the metering.
The algorithm decides which particular packets are within the bandwidth limits, and
which are in excess the limit.
Two buckets are used, one with a volume equal to the CBS (C bucket) and one with
the volume equal to the EBS (E bucket).
How does it works (see Fig. 61)
• The token buckets C and E are initially (at time 0) full, i.e.:
 the token count Tc(0) = CBS
 the token count Te(0) = EBS.
• Tokens are dropped into the buckets at rates equal to the CIR and EIR
respectively.
• Simultaneously, every time a packet comes past, a set of tokens equal to the size
of the packet are taken out of the buckets.
• As long as the C bucket is not empty, packets are market green.
• When the C bucket is empty, but the E bucket is not, packets are marked yellow.
• If both buckets are empty, packets are marked red
• When the source remains idle (no incoming frames) tokens accumulate in the
bucket.
• The idle “credits” can be recovered by the source via sending packets later at a
speed faster than CIR bits/sec.
The value of CBS will depend upon the type of applications or traffic that the service
is targeting to support.
For example, for a service designed to support bursty TCP-based data applications,
CBS will be much larger than for a service supporting more constant rate UDP-based
applications.

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Dropped
Incoming
Frames
Bucket size
according to EBS
Bucket size
according to CBS
Excess Rate
Bucket
Committed Rate
Bucket
Outgoing Frames
at a regular rate
with controlled burst
CIR - Committed Information Rate, CBS - Committed Burst Size, PIR - Peak Information Rate, MBS -
Maximum Burst Size, EIR: Excess Information Rate
Metering: Two rate - three color marker Algorithm (trTCM)
New token added CIR/8 times/second
Check packet size against
“number of tokens“ in
Bucket
If OK, go on and subtract
packet size.
If not OK, drop packet.
New token added EIR/8
times/second
One token = one byte
c
E
…
…
…
…
…
…
.
Violating Frames
(above EIR)
Conforming Frames
(within EIR)
Conforming Frames
(within CIR)
Exceeding Frames
between CIR and PIR
Fig. 61 Metering algorithm

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4.4 Buffer Manager: Congestion Avoidance
RED Algorithm
Random Early Detection (RED) is an algorithm which simply drops packets if too
many are being received.
This causes the devices which are sending the packets to notice a problem and
reduce their transmissions.
This mechanism is especially useful in TCP traffic where the TCP can adjust its BW
according to the network congestion levels.
The key to this policy is the hypothesis that a packet randomly drop from all incoming
traffic will belong to a particular user with a probability proportional to the average
rate of transmission of that user.
The design idea of RED is very simple: two preset thresholds are used to detect
incipient congestion and control the average queue size.
Fig. 62 illustrates the general idea of RED.
According to the estimated average queue length, there are three different working
states.
• When the average queue length is less than the minimum threshold, all incoming
packets are processed and forwarded properly, and no packet is dropped.
• When average queue length is between the minimum and maximum thresholds,
arriving packets are randomly dropped with a probability that is a function of the
average queue length.
• When the average queue length is greater than the maximum threshold, every
arriving packet is discarded.
However, the probability of packet discard when the queue depth equals the
maximum threshold is 1/ (MPD) where MPD is the so called Mark Probability
Denominator
For example, if the mark probability denominator was set to 10, when the queue
depth reached the maximum threshold, the probability of discard would be 1/10 (that
is, a 10 percent chance of discard).

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RED – Drop Profile
•RED: Random early detect
Idea: Throw away certain packets before the buffers run completely full.
Without RED
(Tail Drop)
Queue filling
level
Drop Probability
0
0 Max
0
0
100%
Max
With RED
No
dropping
random
dropping
full dropping100%
probability of discard at
the maximum threshold
Equal to 1/MPD)
Fig. 62 RED general Idea
WARNING
Red Algorithm is implemented inside the First Mile 200 and HUB 800 and it only
works for yellow packets. The green packets will be dropped only when the
buffer becomes full. All the red packets are dropped.

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WRED Algorithm
Unlike RED, Weighted Random Early Detection (WRED) has a profile for each
priority marking.
For example, a packet marked "yellow" might have a minimum threshold of 25
packets, whereas a packet marked "green" might have a minimum threshold of 30
packets. In this example, "yellow" packets start to be discarded "before" green.
0
0
100%
Max
Lower class is treated with a more
aggressive Drop-Profile
DropProbability
Queue filling
Fig. 63 WRED general idea
WARNING
WRED Algorithm is implemented inside the A1200/A2200

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4.5 Queue Scheduler
By means of scheduling algorithms is possible to decide which frames forward first
based on its priority and how to manage the shared available bandwidth in case of
congestion.
Five strategies can be considered:
1) Without QoS management: FIFO (First In First Out) queuing (Fig. 64)
• Only one queue
• Frames are transmitted in the same order they arrive
In case of congestion:
• All frames experience queue delay irrespective of their class of service
• Frames may be discarded irrespective of their class of service
First In First Out
Fig. 64 FIFO Queuing
WARNING
FIFO could be implemented inside FPFM200 and HUB 800

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2) Strict priority queuing (Fig. 65)
• One queue for each class
• Queues are processed in descending order (highest to lowest).
• Queues assigned as high priority are serviced until they are empty.
Low priority queues potentially can be starved; in order to avoid it, high priority traffic
should be kept small.
Strict Priority Queuing (SPQ)
• SPQ Uses multiple queues
• Allows prioritization
• Always empties higher priority queue before going to the next queue:
– Empty Queue Q3
– If Queue Q3 empty, then dispatch from Queue no. 2
– If both Queue Q3 and Queue Q2 empty, then dispatch from Queue Q0…
1 3 6 6 7 7 7
Queues
Until Queue 3 is emptied
Direction of Data flow
7 7 7
6
3
Q3
Q2
Q1
1
Q0
6
Queue Priority
Q3 7
Q2 6,5
Q1 3,4
Q0 1,2
Fig. 65 Example of Strict Priority Queuing
Strict Priority is implemented inside A1200, A2200 and First Mile 200
FlexiPacket A1200/A2200 has 5 queues
FPFM200 and HUB 800 have 8 queues

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3) Weighted Round Robin (WRR) (Fig. 66)
• The weight is a variable that indicates how many packets have to be sent in each
cycle from each queue.
• A sequence of scheduling is generated automatically according to this value.
• If a queue has fewer packets than the value of the weight, the WRR scheduler
outputs the existent number of packets and begins to serve the next queue.
• The WRR scheduler does not take the size of the transmitted packets into
account.
Weighted Round Robin (WRR)
• Allows prioritization
• Assign a “weight” to each queue
• Dispatches packets from each queue proportional to an
assigned weight
3 67 77
Queues
Direction of Data flow
7 77
6
3
6
6
Queue Priority Weight
Q3 7 3
Q2 6 2
Q1 3 1
Q3
Q1
Q2
Q3
Q2
Q3
Q1
Q3
Q2
Fig. 66 Example of Sequence of Scheduling in a Weighted Round Robin
Weighted Round Robin is implemented inside A1200/A2200/ First Mile 200/HUB
800

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4) Deficit Round Robin (DRR)
An inherent limitation of the WRR mode is that bandwidth is allocated in terms of
packets. WRR works well if the average packet size of each coarse-grained CoS
queue flow is known. In most instances, however, this attribute is traffic-dependent
and can vary over time. DRR provides a bandwidth allocation scheduler mode that
takes into account the variably sized packet issue by maintaining sufficient state
information when arbitrating across the CoS queues.
According to the DRR algorithm, each queue "I" has a counter associated called
Deficit Counter (DCi), which indicate the amount of resources (bytes) the flow can
use in a round.
Flows are visited in a round robin fashion.
Each flow is visited only once during each round.
Upon each visit the flow’s deficit counter DCi is increased by a fixed quantity Q called
quantum.
A packet is sent only if its length is smaller than the deficit counter’s current value,
otherwise the flow is skipped.
After a packet is sent the deficit counter is decreased by the size of the transmitted
packet.
Let's consider one example in which there are 4 queues with the same "quantum" in
order to simplify the example.
The example is reported from Fig. 67 to Fig. 70.
As reported in Fig. 67 the "Quantum" is equal to 500 bytes.
As you can see in the example, the packet is sent only if it's ≤ respect to the "Deficit
Counter's current value".
The "Deficit Counter's current value" may include a "Credit" coming from the previous
"round".

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500700
200500
400
Initial State
Queue 1
Queue 2
Queue 3
Queue 4
Quantum = 500 bytes for all queues (may have different quantum for each queue)
Empty space Bytes of the packet Round Robin
1°packet2°packet
2°packet 1°packet
1°packet
600
2°packet
500
3°packet
x..x
Fig. 67
500700
200500
400
Deficit Counter
500
0
500
500
1° Round
Current Value Credit Packet Sent
0
0
300
100
Q1
Q3
Q4
Queue 1
Queue 2
Queue 3
Queue 4
Packet 1 of queue1 gets served (500 ≥ 500) => credit = 0
Quantum
size
Empty space Bytes of the packet Round RobinPacket sent
600
500
Fig. 68

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700
500
Deficit Counter
500
0
800
600
2° Round
500
0
300
0
Q3
Queue 1
Queue 2
Queue 3
Queue 4
500
Quantum size+
1° round credit
Quantum
size
Packet 2 of queue1 not served (500 < 700) => credit = 500
Packet 2 of queue3 gets served (300+500 > 500)=> credit = 300
Packet 2 of queue 4 gets served (600 =>600 credit = 0
Empty space Bytes of the packet Round RobinPacket sent
600
Quantum size+
1° round credit
Q4
Fig. 69

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700
Empty queue
500
Deficit Counter
1000
0
800
0
3° Round
300
0
300
0
Q3
Queue 1
Queue 2
Queue 3
Queue 4
Q1
Quantum size+ credit
Quantum size+ 2°
round credit
Packet 3 of queue1 gets served (500 + 500 > 700) => credit = 300
Packet 3 of queue3 gets served (300 + 500 > 500) => credit = 300
Empty space Round RobinPacket sent
Fig. 70
WARNING
A reset operation avoids outstanding packets. No accumulate credits for a long
period
WARNING
Quantum may be different for each queue introducing a different "weight" for
each queue
FlexiPacket First Mile 200 and HUB 800 give the possibility to select the DRR
Scheduling mode

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5) Multi stage: two strategies can be combined together
Example: Weighted Round Robin Queuing + Strict Priority (Fig. 71)
WARNING
Weighted Round Robin + Strict Priority Multi Stage is implemented inside
A1200/A2200/FPFM200 and HUB 800. In A1200/A2200 there is a fix Multi stage:
2SP+3WRR (Fig. 71). In First Mile 200/HUB 800 the Multi stage is fully
programmable (Fig. 72).
Deficit Round Robin + Strict Priority is implemented inside FPFM200/HUB800

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A1200/A2200 QoS Classes Summary
Fig. 71 A1200/A2200 QoS Classes Summary
Fig. 72 FPFM 200 WRR/DRR and Strict Priority scheduling

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5 Quality of service in the FlexiPacket Radio
Rel.1.3 EP1
WARNING
Please, skip this chapter and jump to the chapter 6 if the course is about the
FlexiPacket MultiRadio
5.1 Quality of Service Mechanism
Quality of Service Mechanism implemented in the FlexiPacket Radio includes (Fig.
73):
• Classification
• Egress scheduling
Classification
Egress
Scheduling
IDU Side ODU Side
Fig. 73 FlexiPacket Radio Quality of Service (1)
FPR SVR1.x supports QoS mechanism in only one direction: from the gigabit
Ethernet side towards the radio side.
This derives from the fact that the bandwidth available on the gigabit interface is
much bigger than the capacity over the radio link (1 Gbps versus about 400 Mbps).
This implies that there is no need to apply QoS to traffic coming from the radio
interface towards the Ethernet one.
Moreover, frames coming from the radio have been already scheduled and properly
enquired on the remote FPR where QoS has been applied.
The QoS suite foresees a scheduler whose characteristics are described in the
following.
WARNING
As you can see in Fig. 73 metering function is not supported since FPR SVR1.x
does not support the UNI interface, where traffic is metered and marked
accordingly.

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5.2 Classification
Incoming packets are classified according to specified rules in order for them to be
queued in the corresponding Tx queue and then scheduled.
Four Tx queues are available (Fig. 74).
FlexiPacket Radio classifies packets according to the following rules, allowing
multiple classifications (user selectable):
• VLAN ID field (Highest precedence)
• IEEE 802.1p VLAN priority field
• IPv4 DSCP field
• IPv6 traffic class field
• Port (Lowest precedence, always enabled). This criterion is not configurable and it
is exclusively used to assign a CoS to traffic which has not been classified in
anyway. The priority associated to this traffic is based on the port which traffic is
received from. In details: If traffic is received from gigabit Ethernet interface frames
are queued into priority 0 queue (lowest); If traffic is generated internally by the
microprocessor frames are queued into priority 2 queue (second highest).
It is possible to enable the criteria either separately or in combination (the criterion
based on the port is always enabled) but it is not possible to modify the associated
priority (if VLAN ID and PCP criteria are enabled, VLAN ID field will be always
checked first) . The incoming frame is processed starting from the highest
precedence criteria. Lower precedence criteria are considered only if the frame
doesn’t match the higher ones.

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fig. 74 ODU Quality of Service

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5.3 Egress Scheduling
FlexiPacket Radio supports four egress scheduling algorithms to handle Ethernet
frames towards the radio:
1) FIFO (First In First Out) queuing (see Fig. 64)
2) Strict priority queuing (Fig. 65)
3) Weighted Round Robin (Fig. 66)
4) Multi stage: Weighted Round Robin+ Strict Priority
Two strategies can be combined together.
FlexiPacket Radio supports 2 SP + 2 WRR with configurable weights (default) or
1 SP + 3 WRR with configurable weights
WARNING
FlexiPacket Radio has four queues

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6 Quality of service in the FlexiPacket
MultiRadio Rel 2.1
WARNING
Please, skip this chapter if the course is about the FlexiPacket Radio
6.1 Quality of Service Mechanism
Figure Fig. 75 shows the QoS architecture, structured in two main functional blocks:
• Classification
• Egress scheduling
Classification
Egress
Scheduling
IDU Side ODU Side
Fig. 75 FlexiPacket MultiRadio Quality of Service (1)
Incoming Ethernet packets are classified according to the specified criteria in order to
be queued inside the correspondent buffer, waiting to be scheduled.
The Egress scheduling applies the QoS scheduling criteria among all queues to
prioritize the egress traffic sent to the radio.
Up to 8 egress queues could be configured and used for scheduling the egress
traffic.

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6.2 QoS Classification Criteria
The incoming Ethernet packets are classified according to the following criteria also
called classification rules in the following:
• Ethernet Source and Destination MAC address
• EtherType field
• IEEE 802.1p VLAN priority field
• VLAN ID field
• Pv4 ToS/DSCP field
• IPv6 traffic class field
• MPLS EXP field
6.3 Egress Scheduling
FlexiPacket MultiRadio supports three egress scheduling algorithms to handle
Ethernet frames towards the radio:
1) FIFO (First In First Out) queuing (see Fig. 64)
2) Strict Priority Queuing (Fig. 65)
In Strict Priority Queuing strategy, the active egress queues are served in descending
order of priority, from the highest to the lowest: each queue is served till it is
completely empty.
3) Weighted Round Robin (Fig. 66)
In Weighted Fair Queuing strategy, the available bandwidth is shared among all
active queues proportionally to specific weights associated to each queue: these
weights permit defining the amount of traffic that will be scheduled out for each
queue.
The weighting is configurable: the weights can be assigned to each priority queue.
Moreover a queue limiter is implemented in order to limit the amount of traffic from a
specific queue.
4) Multi stage: Weighted Round Robin+ Strict Priority
Two strategies can be combined together.

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7 Ethernet OAM

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7.1 OAM Definition
OA&M (operations, administration, and maintenance) generally speaking means a
set of functions used by the user that enables detection of network fault and
measurement of network performance, as well as distribution of fault-related
information.
Ethernet OAM means Management Capabilities associated with Ethernet
Technology and used mainly in the Access network.
It refers to the tools and utilities available to install, monitor, and troubleshoot the
network and allow service providers to offer improved levels of services assurance.
What is OAM? Here below there are some OAM tasks:
Operations:
• Automatic monitoring of environment (e.g. discovery)
• Detect and isolate faults (e.g. connectivity verification, path trace)
• Alert administrators (e.g. AIS, RDI, SNMP trap)
Administration:
• Performance monitoring (utilization, latency, loss, error rate, jitter)
• Capacity planning
Maintenance:
• Upgrades
• New feature deployment
• Monitor health

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7.2 OAM Layers
Ethernet as a technology may overlay a set of physical layer segments on one hand
and on the other hand enable seamless layer-2 services end-to-end.
Considering the OA&M requirements of such technology and its objectives (efficient
troubleshooting), the entire solution can be divided into the following layers:
• Service Layer
 Measures and represents the status of the services as seen by the
customer.
 Produces metrics such as throughput, roundtrip delay, and jitter
that need to be monitored to meet the SLAs contracted between
the provider and the customer.
• Network Layer
 Monitors path between two non-adjacent devices.
• Transport Layer
 Ensures that two directly connected peers maintain bidirectional
communication.
 Must detect “link down” failure and notify higher layer for protocol
to reroute around the failure.
 Monitors link quality to ensure that performance meets an
acceptable level.
Relationship among layers and standards is reported in Fig. 76.
• Each layer supports OAM capabilities independently
• OAMs interoperate
• Component responsibilities are complementary
E2E Performance
Monitoring
E2E Fault Monitoring
P2P Link Fault
Management
E-LMI= Ethernet Local Management Interface
Fig. 76 OAM Layer Components

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Fig. 77 resumes the Ethernet OAM Standards.
Ethernet OAM
IEEE 802.1ag:
Connectivity Fault Management (CFM)
Also referred as Service OAM
IEEE 802.3ah (clause 57)
Ethernet Link OAM
Also referred as 802.3 OAM, Link OAM or Ethernet in the First Mile (EFM) OAM
ITU-T Y.1731
OAM functions and mechanisms for Ethernet-based networks
MEF E-LMI
Ethernet Local Management Interface
Fig. 77 Ethernet OAM Standards

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The Ethernet OAM architecture building block is reported in Fig. 78
Point-to-Point EVCPoint-to-Point EVC
Carrier A
E-NNI
UNI
Multi-point to
Multi-point EVC
Multi-point to
Multi-point EVC
UNIUNI
Point-to-Point EVCPoint-to-Point EVC
UNI
UNI
UNI
Link OAM
•Fault-802.3ah
E2E Service OAM
•Fault-802.1ag
•Perform-Y.1731
Carrier B
Fig. 78 Ethernet OAM architecture building block

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7.3 Ethernet Link Fault Management OAM (EFM OAM)
802.3ah
Ethernet Link Fault Management (see Fig. 79 ) has the following main tasks:
• Monitors the physical connection between two devices
• Troubleshoot individual links
• Fault Detection and Notification (Alarms)
• Count Frame and Symbol errors
• Remote Link Fault
• Loop-back testing – out-of-service
802.3ah 802.3ah 802.3ah 802.3ah 802.3ah 802.3ah 802.3ah 802.3ah
UNI UNI
E-NNI
802.3ah
E-Line Service
Operator 1 Operator 2
Fig. 79 EFM OAM

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7.4 Connectivity Fault Management
(CFM) – 802.1ag
CFM is an end-to-end per-service-instance Ethernet layer OAM protocol that includes
the following proactive Fault Management functions:
• Fault Detection/Monitoring
 Continuity check (CC)
• Fault Verification
 Loopback (LB)
• Fault Isolation
 Link Trace (LT)
7.4.1 802.1ag: Terminology
Maintenance Domain (MD)
It's a part of a network that is controlled by a single operator.
It's defined by a set of internal and external (boundary) ports.
A Domain is assigned by the administrator a unique Maintenance Level (0 – 7).
The level of the domain is useful in defining the hierarchical relationships of multiple
domains.
CFM maintenance domains allow different organizations to use CFM in the same
network, but independently.
For example (Fig. 80), let's consider a service provider who offers a service to a
customer, and to provide that service, they use two other operators in segments of
the network.
In this environment, the customer can use CFM between their CE devices, to verify
and manage connectivity across the whole network, the service provider can use
CFM between their PE devices to verify and manage the services they are providing
and each operator can use CFM within their operator network, to verify and manage
connectivity within their network.
Recommended values of levels are as follow:
• Customer Domain largest (e.g. 7)
• Provider Domain in between (e.g. 3)
• Operator Domain smallest (e.g. 1)

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Maintenance Domains are nested but not overlapped.
The encompassing domain must have a higher level than the domain it encloses as
reported in Fig. 80.
Operator 1 Domain level 1 Operator 2 Domain level 0
Service Provider Domain level 6
Core CoreAccess Access
Customer Domain level 7
Fig. 80 Different CFM Maintenance Domains across a Network
.
Maintenance Association (MA)
It's used to monitor connectivity for a single service instance within the Maintenance
Domain.
It's a set of MEPs (see next point) established to verify the integrity of a single service
instance.
Maintenance Point (MP)
A CFM Maintenance Point (MP) is an instance of a particular CFM service on a
specific interface.
CFM only operates on an interface if there is a CFM maintenance point on the
interface; otherwise, CFM frames are forwarded transparently through the interface.
A maintenance point is always associated with a particular CFM service, and
therefore with a particular maintenance domain at a particular level.
Maintenance points generally only process CFM frames at the same level as their
associated maintenance domain.
Frames at a higher maintenance level are always forwarded transparently, while
frames at a lower maintenance level are normally dropped.
This helps enforce the maintenance domain hierarchy, and ensures that CFM frames
for a particular domain cannot leak out beyond the boundary of the domain.

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There are two types of Maintenance Point: MEP and MIP (see next step and Fig. 81)
Maintenance End Point (MEP)
It resides at the edge of a maintenance domain. Proactively transmits Continuity
Check (CC) Messages. MEP processes/Drops/Forwards CFM frames based on MD
level. It transmits trace-route and Loopback messages upon operator request.
There are two types of MEP (Fig. 82):
• UP (inward in respect to the device)
• DOWN (outward in respect to the device)
The terms Down MEP and Up MEP are defined in the IEEE 802.1ag and ITU-T
Y.1731 standards, and refer to the direction that CFM frames are sent from the MEP.
The terms should not be confused with the operational status of the MEP.
Maintenance Intermediate Point (MIP)
It's a passive functional entity located at intermediate points in a Maintenance
Domain.
MIP maintains CCM Database and responds to trace-route and Loopback messages.
Operator 1 Domain Operator 2 Domain
Service Provider Domain
MEPMIPMEP MIP
MEPMIPMIP
MEPMIP
MEPMIPMEP
MEP
MEP
PHY
Core CoreAccess Access
CFM
Customer Domain
Fig. 81 CFM Terminology
WARNING
In CFM diagrams, the conventions are that triangles represent MEPs, pointing
in the direction that the MEP sends CFM frames, and circles represent MIPs.

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