(4)optix hybrid mstp technology introduction

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Content

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Overview...................................................................................................Pa

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M P L S T u n n e l

Technology ............................................................................Page16

M P L S - T P

Technology ...Page36

Q i n Q

Overview ....Page43

P W E 3

Overview ...Page46

P-0 Hybrid MSTP Technology Introduction


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Understanding the IP address knowledge are the basics for the further IP address

configuration or planning in OptiX OSN 1500/3500/7500/7500II Hybrid MSTP

products.

MPLS basics and MPLS LSP are the emphasis of the course, it is the generic basics

of OptiX OSN 1500/3500/7500/7500II Hybrid MSTP products application and

configuration.

Understanding the PWE3 position in the OptiX Hybrid MSTP network and its

basic concepts.



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The physical layer contains the protocols relating to the physical medium on which TCP/IP will be communicating.

Electrical/optical protocols describe signal characteristics such as voltage or photonic levels, bit timing, encoding, and signal shape.

Mechanical protocols are specifications such as the dimensions of a connector or the metallic makeup of a wire.

Functional protocols describe what something does.

Procedural protocols describe how something is done. For example, a binary 1 is represented on an EIA-232-D lead as a voltage more negative than 3 volts.

The data link layer contains the protocols that control the physical layer: how the medium is accessed and shared, how devices on the medium are identified, and how data is framed before being transmitted on the medium. Examples of data link protocols are IEEE 802.3/Ethernet, IEEE 802.5/Token Ring, and FDDI.

The network layer, corresponding to the OSI network layer, is primarily responsible for enabling the routing of data across logical internetwork paths, by defining a packet format and an addressing format.

The transport layer, corresponding to the OSI transport layer, specifies the protocols that control the network layer, much as the data link layer controls the physical layer. Both the transport and data link layers can define such mechanisms as flow and error control. The difference is that while data link protocols control traffic on the data link, the physical medium connecting two devices, the transport layer controls traffic on the logical link, the end-to-end connection of two devices whose logical connection traverses a series of data links.

The application layer corresponds to the OSI session, presentation, and application layers. The most common services of the application layer provide the interfaces by which user applications access the network.



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The physical layer contains the protocols relating to the physical medium on

which TCP/IP will be communicating.

The data link layer contains the protocols that control the physical layer: how the

medium is accessed and shared, how devices on the medium are identified, and

how data is framed before being transmitted on the medium. Examples of data

link protocols are IEEE 802.3/Ethernet, PPP, HDLC, FR etc.

The network layer is primarily responsible for enabling the routing of data across

logical internet paths, by defining a packet format and an addressing format.

Examples of network layer protocols are IP, ICMP, ARP etc.

The transport layer controls traffic on the logical link, the end-to-end connection

of two devices whose logical connection traverses a series of data links. Examples

of transport layer protocols are TCP/UDP.

The most common services of the application layer provide the interfaces by

which user applications access the network. Examples of transport layer

protocols are HTTP, Telnet, FTP, Ping etc.



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Version: Identifies the I P version to which the packet belongs. This four-bit field

is usually set to binary 0100; version 4 (IPv4) is in current, common use. A newer

version of the protocol, is version 6 (IPv6).

Header Length: tells the length of the IP header.

Type of Service (TOS): generally used for Qos. This field actually can be broken

down into two subfields: Precedence and TOS.

Total Length: specifying the total length of the packet, including the header, in

octets.

Identifier/ Flags/ Fragment Offset: these three fields are used for fragmentation of

a packet.

Time to Live (TTL): is set with a certain number when the packet is first generated.

As the packet is passed from router to router, each router will decrement this

number.

Protocol: gives the "address," or protocol number, of the host-to-host or transport

layer protocol for which the information in the packet is destined.

Header Checksum: is the error correction field for the IP-header.

Source and Destination Addresses: are the originator of the packet and the

destination of the packet.

Options: is a variable-length field, and is optional.

Padding: ensures that the header ends on a 32-bit boundary by adding zeros after

the option field until a multiple of 32 is reached.



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IP addresses are 32 bits long; like all network-level addresses, they have a

network portion and a host portion. The network portion uniquely identifies the

network and is common to all devices attached to the network. The host portion

uniquely identifies a particular device attached to the network.

The hierarchical design of IP address reduces the size of route entry and it is very

flexible.

The binary to decimal calculation is as the example,

the binary 11101001 is represented by decimal format:

1*128+1*64+1*32+0*16+1*8+0*4+0*1+1*1=233.



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Class A IP addresses are for big internetworks. The first octet is the network

portion, and the last three octets are the host portion. Only 256 numbers are

available in the eight-bit network part, but 224 or 16,777,216 numbers are

available in the host part of each of those network addresses.

Class B addresses are for medium-size internetworks. The first two octets are the

network portion , and the last two octets are the host portion. There are 216 or

65,536 available numbers in the network part and an equal number in the host

part.

Class C addresses are just the opposite of class A. The first three octets are the

network portion, and the last octet is the host.

Class D addresses are reserved for multicast. Class E addresses are reserved for

future use.

The most commonly used addresses are from A, B and C. The IP addresses are

allocated by International Network Information Center.



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Private IP addresses are usually used by enterprise internal network.

Inter-NIC reserved the following IP addresses for private use:

Class A: 10.0.0.0~10.255.255.255

Class B: 172.16.0.0~ 172.31.255.255

Class C: 192.168.0.0~192.168.255.255

Private IP addresses can not be used to access Internet, because public network

has no routes for private IP addresses. NAT (Network Address Translation) can be

used to translate private addresses into public addresses



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The address for an entire data link, a non-host-specific network address is

represented by the network portion of an IP address, with all host bits set to zero.

Each device or interface will be assigned a unique, host-specific address such as

192.168.1.1. The device obviously needs to know its own address, but it also

needs to be able to determine the network to which it belongs, in this case,

192.168.1.0.

This task is accomplished by means of an address mask. The address mask is a 32-

bit string, one bit for each bit of the IP address. As a 32-bit string, the mask can

be represented in dotted-decimal format just like an IP address.



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A single class A, B, or C address can be used only on a single data link. To build an

internetwork, separate addresses must be used for each data link so that those

networks are uniquely identifiable. If a separate class A, B, or C address were

assigned to each data link, less than 17 million data links could be addressed

before all IP addresses were depleted. This approach is obviously impractical, as

is the fact that to make full use of the host address space in the previous example,

more than 65,000 devices would have to reside on data link 172.16.0.0.

The only way to make class A, B, or C addresses practical is by dividing each

major address, such as 172.16.0.0, into sub-network addresses.

The IP address now has three parts: the network part, the subnet part, and the

host part. The address mask is now a subnet mask, or a mask that is longer than

the standard address mask.

For example, the first three octets of the address of 192.168.1.17 will always be

192.168.1, but the fourth octet whose first four bits are now subnet bits instead

of host bits. The range is 0 to 15. it has 16 subnets and 14 host IP addresses in

each subnet.



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For point to point link, two IP addresses is enough, so the mask length is 30:

255.255.255.252

For broadcast link, the mask length is decided by host number of broadcast

network: if there are 60 hosts, mask length should be 26. if there are 120 hosts,

mask length should be 25.

For device identifier, for example, OSPF and BGP Router ID, loopback address is

used directly. The mast length for loopback address is 32, which is the same to

MPLS LSR ID.



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The Internet based on the IP technology prevails in the middle 1990s. The IP

technology, however, performs poorly in forwarding packets because of the

inevitable software dependence on searching routes through the longest match

algorithm. As a result, the forwarding capability of IP technology becomes a

bottleneck to the network development.



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To improve the forwarding capability, the Asynchronous Transfer Mode (ATM)

technology comes out. It uses labels (namely, cells) of fixed length and maintains a

label table that is much smaller than a routing table. Therefore, compared with

the IP technology, the ATM technology performs much better in forwarding

packets. The ATM technology, however, is difficult to popularize because of its

complex protocol and high cost in deployment.



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The traditional IP technology is simple and costs little in deployment.

People then are eager to making a technical breakthrough to combine

advantages of IP and ATM technologies. Thus, the MPLS technology

comes forth.

Initially, MPLS emerges to increase the forwarding rate of routers.

Compared with IP routing, when forwarding packets, MPLS analyzes the

IP packet header only on the network edge but not at each hop. In this

way, the time to process packets is shortened.



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MPLS is the abbreviation of Multi-Protocol Label Switching. MP means it support

more than one protocol, such as IP, IPv6, IPX, SNA, etc. as we know, in IP

network, the routers forwarding packets by using packets destination IP address

and looking for the IP routing table to get the next hop, while in MPLS network,

we using label to forward the packets, named label switching. MPLS uses a short

label of fixed length to encapsulate packets. MPLS use FEC (Forwarding

Equivalent Class) to classify the forwarding packets. The packets of the same FEC

are treated the same in the MPLS network. later we will introduce the FEC.

By adding a label to the packet at the entrance of MPLS network, the packet is

forwarded by label switching, some thing like ATM Switching. And when leaving

the MPLS network, the label added is removed and the label packet is restored to

original protocol packet.

For more details about MPLS, refer to RFC 3031 (Multi-protocol Label Switching

Architecture).



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LSR is the basic component of the MPLS network. The network consisting of LSRs,

is called an MPLS domain. The LSR which located at the edge of the domain and

having a neighbor which not running MPLS is an edge LSR, also called Labeled

Edge Router (LER).

The LSR located inside the domain is called a core LSR. The core LSR can be either

a router that supports MPLS or an ATM-LSR upgraded from an ATM switch. MPLS

runs between LSRs in the domain, and IP runs between an LER and an router

outside the domain.

The LSRs along which labeled packets are transmitted form an LSP.



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Label Switched Path

The path that IP packets pass through on an MPLS network is called the

LSP. An LSP is a unidirectional path in the same direction with the data

flow.

The beginning node of an LSP is called the ingress. The end node of the

LSP is called the egress. The nodes between both ends along the LSP are

transits. An LSP may have none, one, or several transit(s), but only one

ingress and one egress.

Ingress

Indicates the beginning of an LSP. Only one ingress exists on an LSP.

The ingress pushes a new label to the packet and encapsulates the IP

packet as an MPLS packet to forward.

Transit

Indicates the middle node of an LSP. Multiple transits may exist on an LSP.

The transit mainly searches in the label forwarding table. Then, it swaps

the labels to complete the forwarding of MPLS packets.

Egress

Indicates the end node of an LSP, only one egress exists on an LSP.

The egress mainly pops labels out of MPLS packets and forwards the

packets that restore the original encapsulation.

The ingress and egress serve as LSRs and LERs. The transit serves as the LSR.



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A label is a short identifier of fixed length with only local significance. It is used to

uniquely identify an FEC to which a packet belongs. In some cases like load

balancing, different labels are assigned to an FEC, but one label only represents

one FEC on a router. The label is a connection identifier, similar to the ATM

VPI/VCI and the Frame Relay DLCI.

A label is 4 bytes long. The above figure shows the encapsulation structure of the

label.

A label contains the following fields:

Label: indicates the value field of a label. The length is 20 bits. Label

space means the range of label values. Generally, the label space is

classified as follows:

015: indicates special labels.

161023: indicates the label space shared by static LSPs and CR-

LSPs.

1024 or above: indicates the label space for dynamic signaling

protocols, such as LDP, RSVP-TE, and MP-BGP.

Exp: indicates the bits used for extension. The length is 3 bits. Generally,

this field is used for the Class of Service (CoS) that serves similarly to

Ethernet 802.1p.

S: identifies the bottom of a label stack. The length is 1 bit. MPLS

supports multiple labels, namely, the label nesting. When the S field is 1,

it means that the label is at the bottom of the label stack.

TTL: indicates Time To Live. The length is 8 bits. This field is the same to

the TTL in IP packets.

Labels are encapsulated between the data link layer and the network layer. Thus,

labels can be supported by any protocol of the data link layer.



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A label stack is a set of arranged labels. An MPLS packet carries multiple

labels at the same time. The label next to the Layer 2 header is called the

top label or the outer label. The label next to the Layer 3 header is called

the bottom label or inner label. Theoretically, MPLS labels can be nested

limitlessly.

The label stack organizes labels according to the rule of Last-in, First-Out

and processes labels from the top of the stack.



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The Forwarding Equivalence Class (FEC) is a set of data flows with the same

attributes. These data flows are processed in the same way by LSRs during

transmission.

FECs are identified by the address, service type, and QoS. For example, during IP

forwarding through the longest match algorithm, packets with the same

destination belong to an FEC.



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Push

When an IP packet enters an MPLS domain, the ingress adds a new label to

the packet between the Layer 2 header and the IP header; or, a transit

adds a new label to the top of the label stack, namely, the label nesting.

Swap

When a packet is transferred within an MPLS domain, a label is deleted

from the top of the label stack and a new label of the next hop is added

according to the label forwarding table.

Pop

When a packet leaves an MPLS domain, the label is popped out of the

MPLS packet; or, the top label of the label stack is popped out at the

penultimate hop on an MPLS network to decrease the labels in the stack.

Penultimate Hop Popping

In fact, the label is useless at the last hop of an MPLS domain. In this case,

the feature of penultimate hop popping (PHP) is applied. On the

penultimate node, the label is popped out of the packet to reduce the size

of the packet that is forwarded to the last hop. Then, the last hop directly

forwards the IP packet or the VPN packet.



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The availability of a static LSP makes sense only for the local node that cannot

sense the entire LSP.

On the ingress: A static LSP is set up, and the outgoing interface of the

ingress is enabled with MPLS. If the route is reachable, the static LSP is Up

regardless of the existence of the transit or egress. A reachable route

means that a route entry exists whose destination address and the next

hop address match those in the local routing table.

On the transit: A static LSP is set up, and the incoming and outgoing

interfaces of the transit are enabled with MPLS. If the incoming and

outgoing interfaces are Up on the physical layer and protocol layer, the

static LSP is Up, regardless the existence of the ingress, egress, or other

transits.

On the egress: A static LSP is configured, the incoming interface of the

egress is enabled with MPLS. If the incoming interface is Up on the physical

layer and protocol layer, the static LSP is Up, regardless the existence of

the ingress or the transit.

A static LSP is set up without label distribution protocols or exchanging control

packets. Thus, the static LSP costs little and it is applicable to small-scale

networks with simple and stable topology. The static LSP cannot vary with the

network topology dynamically. The administrator needs to configure the static

LSP.



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Dynamic LSPs are set up automatically by the signaling protocol. The following

label distribution protocols are applicable to an MPLS network.

LDP

The Label Distribution Protocol (LDP) is specially defined for distributing

labels. When LDP sets up an LSP in hop-by-hop mode, LDP identifies the

next hop along the LSP according to the routing and forwarding table on

each LSR. Information contained in the routing and forwarding table is

collected by IGP and BGP. LDP indirectly uses routing information rather

than is directly associated with the routing protocols.

RSVP-TE

The Resource Reservation Protocol (RSVP) is designed for the integrated

service module and is used to reserve resources on nodes along a path.

RSVP works on the transport layer and does transmit application data.

RSVP is a network control protocol, similar to the Internet Control Message

Protocol (ICMP).

RSVP is extended to support the setting up of a Constraint-based Routed

LSP (CR-LSP). The extended RSVP is called the RSVP-TE signaling protocol.

It is used to set up TE tunnels.



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An MPLS tunnel is shown above. The MPLS label 100, 200 and 300 are assigned

by the operator.



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An MPLS label has a TTL field in the length of 8 bits. The TTL field is the same as

that in an IP packet header. MPLS processes the TTL to prevent loops and

implement traceroute.

RFC 3443 defines two modes in which MPLS processes the TTL, that is, uniform

mode and pipe mode. By default, MPLS processes the TTL in Pipe mode.

Uniform Mode

When IP packets enter an MPLS network, on the ingress, the IP TTL

decreases by one and is mapped to an MPLS TTL field. Then, the TTL field

in MPLS packets is processed in the standard mode. As shown in the figure,

on the egress, the MPLS TTL decreases by one and is mapped to the IP TTL

field.



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Pipe Mode

As shown in the figure, on the ingress, the IP TTL decreases by one and the

MPLS TTL is constant. Then, MPLS TTL is processed in the standard mode.

On the egress, IP TTL decreases by one. That is, when IP packets enter an

MPLS network, the IP TTL decreases by one only on the ingress and egress.



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The OptiX Hybrid MSTP products support the MPLS tunnels over the following

Layer 2 links:

FE

GE

10GE

Note: Currently OptiX Hybrid MSTP products only support static Tunnel (LSP).



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Penultimate Hop Popping (PHP) is a function performed by certain routers in

an MPLS enabled network. It refers to the process whereby the outermost label of

an MPLS tagged packet is removed by a Label Switch Router (LSR) before the

packet is passed to an adjacent Label Edge Router(LER).

Equal Cost Multi Path (ECMP) is a routing strategy where next-hop packet

forwarding to a single destination can occur over multiple "best paths" which tie

for top place in routing metric calculations. It potentially offers substantial

increases in bandwidth by load-balancing traffic over multiple paths; however,

there can be significant problems in its deployment in practice.


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MPLS-TP started as Transport-MPLS at the ITU-T (see G.81xx series of ITU-T

Recommendations), which was renamed to MPLS-TP based on the agreement that

was reached between the ITU-T and the IETF to produce a converged set of

standards for MPLS-TP.

Transport-MPLS (T-MPLS) was a standardization effort that was undertaken by

the ITU-T. ITU-T approved the first version of its packet transport

recommendation called Transport MPLS (T-MPLS) Architecture in 2006. By 2008,

the technology had reached the stage where some vendors started supporting T-

MPLS in their optical transport products. At the same time, the IETF was working

on a new mechanism called Pseudo Wire Emulation Edge-to-Edge (PWE3) that

emulates the essential attributes of a service such as ATM, TDM, Frame Relay or

Ethernet over a Packet Switched Network (PSN), which can be an MPLS network

[RFC3916].

A Joint Working Group (JWT) was formed between the IETF and the ITU-T to

achieve mutual alignment of requirements and protocols. On the basis of the JWT

activity, it was agreed that future standardization work will focus on defining

MPLS-Transport Profile (MPLS-TP) within the IETF using the same functional

requirements that drove the development of T-MPLS.


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For the MPLS-TP, the function of Data Plane as the IP/MPLS can be static

configured by NMS, including the OAM.

IP/MPLS:

OSPF protocal complete the routing table creation.

LDP (Label Distribution Protocol):is a protocol in which routers capable

of Multiprotocol Label Switching (MPLS) exchange label mapping

information. LDP can be used to distribute the inner label (VC/VPN/service

label) and outer label (path label) in MPLS.

MPLS-TP:

NMS Configuration: The label is generated by the NMS, then forwarding to

the equipment to create the LFIB (Label Forwarding Information Base).

Control Plane: GMPLS, Equipment can without the IP protocal.


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The MPLS-TP control plane is based on a combination of the MPLS control plane

for PW and the GMPLS control plane for MPLS-TP LSPs,


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QinQ technology is a VLAN stacking technology, which conforms to the

recommendation for S-VLAN in IEEE 802.1ad and is an expansion of VLAN

technology.

The default Tag Protocol Identifier (TPID) value is 0x8100. It can be modified in

OptiX Hybrid MSTP.

Advantages of QinQ technology:

Expands VLAN and alleviates VLAN resource insufficiency. For example, a

VLAN providing 4096 VLAN IDs can provide 4096 x 4096 VLANs after

VLAN stacking;

Extends LAN service to WAN, connecting the client network to the carrier

network and supporting transparent transmission.

The default Tag Protocol Identifier (TPID) value is 0x8100

The TPID can be modified in OptiX PTN product



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The feature of this service is that the services are isolated by using the QinQ

technology. The advantage is that the network-side link is shared. When the

number of user VLANs is large, and multiple users use the same VLAN, this

networking type can be used.

In this case, the packets of different companies accessed on the user side are

added to different S-VLANs, and then are carried by the same link on the network

side.



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Concept of PW

The Mechanism that bears the simulated layer 2 services between clients to the packet switch network (PSN).

AC: attachment circuit.

It is the physical or virtual circuit that connects a CE to a PE.

Forwarder

A PE sub-system that selects a PW to transmit the payload received on the AC.

PW signaling

The basis on which PWE3 is implemented. It is used for creating and maintaining PWs. Currently, the primary PW signaling is LDP.

PW: pseudo wire.

It is a mechanism that carries the essential elements of an emulated circuit between PEs over a PSN.

CE: Customer Edge.

It is a device that originates or terminates a service. The CE cannot be aware whether an emulated service or a local service is in use.

PE: Provider Edge.

It is a device that provides PWE3 to a CE. It is usually the edge router that is connected to a CE on a backbone network. A PE is responsible for processing the VPN service. A PE performs the mapping and forwarding of the packets from the private network to the public-network tunnels and that in the reverse order.

CW: control word.

A control word is a 4-byte encapsulated packet header. It is used to transmit packets in an MPLS PSN.



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Normally, the Ethernet service need not be transmitted according to strict

sequence. In ITU-T G. 802.3, however, it is required that frames from the same

session should be transmitted according to the sequence. It cannot be assumed

that the PSN can realize the frame sorting. If strict sorting is required, the serial

number need be used.

The following describes the meaning of each field in the CW:

The first four bits must be 0, which indicates that the data is the PW data.

The packet must be ignored by the PE that receives the packet.

Reserved: It is of 12 bits. It is the reserved field and is often set to 0.

Sequence Number: It is of 16 bits. It is used to guarantee the packet order.

This field is optional. If the Sequence Number is 0, it means the packet

order check is disabled.



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OptiX Hybrid MSTP equipment support TDM E1 PWE3, also we named it as CES

(Circuit Emulation Service) E1

Between BTS and BSC, the CES service is transported through the Hybrid MSTP

equipment.

BTS use E1 connection connected to PE. BSC use one channelized STM-1

connection connected to PE.



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Unframed E1

Using all the time slots as a whole to transmit user data.

So, the total bandwidth for one unframed E1 connection is 2.048Mbps,

just like the bandwidth provided by a serial interface.

Framed E1

Time slot 0 used for signaling or other purpose.

Time slot 1-31 can be used for transmit service data for different users.

For example: Time slot 1 can be used for user1 to provide 64 Kbps

bandwidth, and time slot 11 to 12 can be used for user 2 to provide 128

Kbps bandwidth.

To use a PW to emulate the transmission of TDM service over a PSN, the

following elements must be carried to the other end of the PW.

TDM data

Frame format of TDM data

TDM alarm and signaling at the AC side

Synchronous timing information of TDM



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In the SAToP mode:

The equipment regards TDM signals as constant rate bit flows, instead of

sensing structures in the TDM signals. The entire bandwidth of TDM

signals is emulated.

The overhead and payload in the TDM signal are transparently transmitted.

In the CESoPSN mode:

The Hybrid MSTP equipment senses frame structures, frame alignment

modes and timeslots in the TDM circuit.

The Hybrid MSTP equipment processes the overhead and extracts the

payload in TDM frames. Then, the equipment delivers the timeslot of each

channel to the packet payload according to certain sequence. As a result,

the service in each channel in the packet is fixed and visible.



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Tunnel label: MPLS label, manually configured in OptiX Hybrid MSTP equipment.

PW label: manually configured.

Control Word: must use, to identify the sequences of the frames.

RTP (Real Time Protocol) Header/ Time Stamp/ SSRC Identifier: if RTP is required,

these encapsulations are required; if not, not required.

To improve the efficiency of the bandwidth, several E1 frames can be cascaded as

one unit, it means several E1 frame use one PWE3, Tunnel and Ethernet

encapsulation. The size of the unit is based on the configuration of buffering time.

By default the buffering time is 1ms. The larger value of buffering time the higher

bandwidth efficiency and also larger service delay.



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Differences of CESoPSN and SAToP:

The CESoPSN protocol can identify frame structure of TDM service. It may

not transmit idle timeslot channels, but it only extracts useful timeslots of

CE devices from the E1 traffic stream and then encapsulates them into PW

packets for transmission.

For example: only time slot 1-5 have data, all the other time slots are idle,

CESoPSN can choose only transmit time slot 1-5s data to another PE, the

opposite PE can reconstruct the original E1 frame, and then send it to

appropriate CE.



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(4)optix hybrid mstp technology introduction

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