ETSI ES 201 803-7 V1.1.1 (2002-05)

Dynamic synchronous Transfer Mode (DTM); Part 7: Ethernet over DTM Mapping

DES/SPAN-130007

Dinamični sinhroni prenosni način (DTM) – 7. del: Preslikava Etherneta preko preslikave načina DTM

General Information

• Status: Published
• Publication Date: 05-May-2002
• Technical Committee: SPAN 13 - SPAN Peer-to-Peer Control Protocol (PTPCP)
• Current Stage: 12 - Completion
• Due Date: 10-May-2002
• Completion Date: 06-May-2002
• Ref Project: SIST ES 201 803-7 V1.1.1:2005 - Dynamic synchronous Transfer Mode (DTM); Part 7: Ethernet over DTM Mapping

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2005
'LQDPLþQLVLQKURQLSUHQRVQLQDþLQ'70±GHO3UHVOLNDYD(WKHUQHWDSUHNR
SUHVOLNDYHQDþLQD'70
Dynamic synchronous Transfer Mode (DTM); Part 7: Ethernet over DTM Mapping
Ta slovenski standard je istoveten z: ES 201 803-7 Version 1.1.1
ICS:
33.040.40 Podatkovna komunikacijska Data communication
omrežja networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

ETSI Standard
Dynamic synchronous Transfer Mode (DTM);
Part 7: Ethernet over DTM Mapping

2 ETSI ES 201 803-7 V1.1.1 (2002-05)
Reference
DES/SPAN-130007
Keywords
DTM, Ethernet, LAN, transmission
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ETSI
3 ETSI ES 201 803-7 V1.1.1 (2002-05)
Contents
Intellectual Property Rights.5
Foreword.5
Introduction .6
1 Scope .7
2 References .7
3 Definitions and abbreviations.7
3.1 Definitions.7
3.2 Abbreviations .8
4 Service overview.8
4.1 DLT service overview.9
4.2 DLE service overview.10
5 System overview .10
5.1 DLT system overview .10
5.1.1 Channels in DLT.11
5.1.2 DLT client traffic forwarding .11
5.2 DLE system overview .11
5.2.1 Channels in DLE.12
5.2.2 Packet forwarding in the DLE Client.12
5.2.3 Address learning in the DLE Client.12
5.2.4 Redundant DLE Servers .13
5.3 VLAN Support .13
6 Service Interfaces .14
6.1 Transport view.14
6.2 Control view.15
7 Detailed Protocol Description .16
7.1 DCMI interaction of DLE and DLT.16
7.2 DCAI interaction of DLE and DLT.17
7.3 DLT operation.17
7.3.1 Startup.18
7.3.2 Normal operation.18
7.3.3 Shutdown .18
7.3.4 Restart.18
7.3.5 Peer disconnect .18
7.3.6 Unknown Message Types and extensions .19
7.4 DLE operation.19
7.4.1 Server startup .19
7.4.2 Server shutdown .19
7.4.3 Server restart.20
7.4.4 New server connected to the DLE segment .20
7.4.5 Server disconnection.20
7.4.5.1 Removal of server to server channel .20
7.4.5.2 Server removal of channel between server and client .20
7.4.6 Client start up.21
7.4.7 Client restart.21
7.4.8 Client disconnect .22
7.4.9 Address resolution .22
7.4.9.1 Forwarding Ethernet frames with unknown destination .23
7.4.9.2 Fast address announce.23
7.4.10 Flush mechanism .23
7.4.11 Normal server operation .25
7.4.12 SCC Filtering .25
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4 ETSI ES 201 803-7 V1.1.1 (2002-05)
7.4.13 Unknown message types.25
8 Messages .26
8.1 General Message Format.26
8.1.1 Representing Ethernet addresses.26
8.2 DLT messages .27
8.2.1 DLT_REGISTER .27
8.2.1.1 Message format .27
8.3 DLE messages .28
8.3.1 DLE_REGISTER .28
8.3.1.1 Message format .29
8.3.2 DLE_REGISTER_RESPONSE.29
8.3.2.1 Message format .29
8.3.3 DLE_AR_REQUEST .29
8.3.3.1 Message format .30
8.3.4 DLE_AR_ANNOUNCE.30
8.3.4.1 Message format .30
8.3.5 DLE_WAIT_FOR_FLUSH.31
8.3.5.1 Message format .31
8.3.6 DLE_FLUSH.31
8.3.6.1 Message format .32
8.3.7 DLE_AUTHENTICATE.32
8.3.8 DLE_SERVER_REGISTER .32
8.3.8.1 Message format .32
8.3.9 DLE_CLIENT_DISCONNECTED.33
8.3.9.1 Message format .33
9 Ethernet encapsulation .33
9.1 Ethernet packets with an 802.1Q tag.34
9.2 Ethernet packets without 802.1Q tag.35
9.3 Valid and invalid VLAN information .35
10 Appendices.36
10.1 Constants .36
10.2 Configuration Parameters DLT .37
10.2.1 DLT Client Configuration .37
10.3 Configuration parameters DLE .37
10.3.1 DLEC configuration .37
10.3.2 DLES configuration.40
Annex A (informative): Bibliography.41
History .42
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5 ETSI ES 201 803-7 V1.1.1 (2002-05)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Services and Protocols for Advanced
Networks (SPAN).
The present document is part 7 of a multi-part deliverable covering the Dynamic synchronous Transfer Mode (DTM),
as identified below:
Part 1: "System description";
Part 2: "System characteristics";
Part 3: "Physical Protocol";
Part 4: "Mapping of DTM frames into SDH containers";
Part 5: "Mapping of PDH over DTM";
Part 6: "Mapping of SDH over DTM";
Part 7: "Ethernet over DTM Mapping";
Part 8: "Mapping of Frame relay over DTM";
Part 9: "Mapping of ATM over DTM";
Part 10: "Routeing and switching of IP flows over DTM";
Part 11: "Mapping of video streams over DTM";
Part 12: "Mapping of MPLS over DTM";
Part 13: "System description of sub-rate DTM".
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6 ETSI ES 201 803-7 V1.1.1 (2002-05)
Introduction
Dynamic synchronous Transfer Mode (DTM) is a time division multiplex and a circuit-switched network technique that
combines switching and transport. The present document specifying the DTM system and protocols is divided into
13 parts.
The present document (part 7) describes the method by which Ethernet [1] packets are carried over DTM.
The topics of the other parts are as follows:
- Part 1 introduces DTM and describes the service over a unidirectional data channel;
- Part 2 includes system aspects that are mandatory or optional for nodes from different vendors to interoperate.
These system aspects are addressing, routing, synchronization and channel management. The interworking
granularity should be at node level, such that nodes from different vendors can interoperate with regard to
well-defined functions;
- Part 3 specifies the physical layer protocol for 8b/10b encoding based physical links;
- Part 4 specifies the physical layer protocol for SDH/SONET VC4 container based physical links;
- The transport of various tributary signals is specified for PDH (part 5), SDH (part 6), Ethernet (part 7), Frame
Relay (part 8), ATM (part 9), IP (part 10), Mapping of MPLS over DTM (part 11), and video streaming
(part 12). Note that DTM can either run over SDH or carry it as a tributary.
- Finally, management aspects are standardized in part 13.
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7 ETSI ES 201 803-7 V1.1.1 (2002-05)
1 Scope
The present document specifies how Ethernet protocol is transported over DTM. The specification encapsulation of
PDUs includes address resolution (mapping the Ethernet source and destination address to the correct DTM
destination), DTM channel set-up, channel capacity modification, and Ethernet VLAN handling.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication and/or edition number or version number) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
[1] IEEE 802.3 (1996): "IEEE Standard for Information technology; Telecommunications and
information exchange between systems; Local and metropolitan area networks; Specific
requirement; Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access
Method and Physical Layer Specifications".
[2] IEEE 802 (1990): "IEEE Standard for Local and Metropolitan Area Networks: Overview and
Architecture".
[3] IEEE 802.1D (1998): "IEEE Standard for Information technology; Telecommunications and
information exchange between systems; IEEE standard for local and metropolitan area networks;
Common specifications; Media access control (MAC) Bridges".
[4] IEEE 802.1Q (1998): "IEEE Standards for Local and Metropolitan Area Networks: Virtual
Bridged Local Area Networks".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
access node: node that supports an external network interface, contains an interworking function for an external
network and uses the DTM service
channel: set of slots allocated from one source access node to one or more destination access nodes in a network
NOTE: The source and destination nodes can be the same, where the channel is internal to the node.
control channel: channel used for channel signalling and management
data channel: channel used for transport of user data
domain: DTM network or part of a network that is managed by a particular commercial or administrative entity
(carrier/operator)
DTM network: set of connected DTM nodes
NOTE: A DTM network may be single-domain, or multi-domain.
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8 ETSI ES 201 803-7 V1.1.1 (2002-05)
frame: set of slots forming an entity that is transmitted on a physical medium repeatedly every 125µs (nominally),
i.e. 8 000 frames/second
node: network element that contains DTM functions
node address: DTM network layer address of a node
slot: time slot within the frame being able to transport 64 bit of data or a number of special codes
switching: process of moving the data of a slot in both time and space, i.e. switching between different ports and
changing slot numbers while maintaining the bandwidth and avoiding slot reordering within each channel
switch node: node that contains a switching function
3.2 Abbreviations
For the purposes of the present document the following abbreviations apply:
ATM Asynchronous Transfer Mode
ARR Address Resolution Request
CCC Client-to-Client Channel
CMI Channel Multiplexing Identifier
CSC Client-to-Server Channel
DCAI DTM Channel Adaptation Interface
DCCI DTM Channel Control Interface
DCAP-1 DTM Channel Adaptation Protocol 1
DCMI DTM Channel Management Interface
DCP DTM Channel Protocol
DLE DTM LAN Emulation
DLEC DLE Client
DLES DLE Server
DLT DTM Ethernet LAN Transport
DST DTM Service Type
DSTI DTM Service Type Instance
DTM Dynamic synchronous Transfer Mode
IP Internet Protocol
MAC Medium Access Control
MIB Management Information Base
PDU Protocol Data Unit
RFC Request For Comment (IETF document)
SCC Server-to-Client Channel
SDH Synchronous Digital Hierarchy
SSC Server-to-Server Channel
TDM Time Division Multiplexing
VLAN Virtual Local Area Network
4 Service overview
There are two different ways of transporting Ethernet traffic across a DTM network specified in the present document:
• DTM LAN Transport (DLT) is a very simple service where the DTM network is used to set up a tunnel between
two DLT clients. Each DLT client is in its turn connected to a logical Ethernet switch. The logical Ethernet
switch forwards packets between the DLT client and one or several Ethernet ports and/or other DLT clients.
• DTM LAN Emulation (DLE) provides the additional service of a distributed Ethernet switch function, allowing
VLAN switching where two or more DLE Clients can be interconnected via the DTM network.
The characteristics of the Ethernet transport utilize the characteristics of the DTM transport service providing traffic
isolation and very low delay variation. The DTM network allows the distance limitation of connected Ethernets to be
removed.
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9 ETSI ES 201 803-7 V1.1.1 (2002-05)
Ethernet is a connectionless technology, meaning that data is transported in packets that are handled independently of
each other. The packets carry sufficient information to identify the Ethernet destination of the packet. DTM, on the
other hand, is connection-oriented; meaning that data is transported using an established connection. During the
establishment of the connection sufficient state information is stored in the switches along the path from source to
destination. In order to forward the data, each data item does not need to carry information specifying the destination.
4.1 DLT service overview
This clause specifies how point-to-point Ethernet transport through a DTM network is done. The system consists of two
DLT clients that are connected via a DTM network. This forms a point-to-point Ethernet link between two logical
Ethernet nodes or switches. Each logical Ethernet switch connects several logical Ethernet interfaces to each other. A
logical Ethernet interface can be either a physical Ethernet interface or a DLT client.
Legend
Node X
Physical node with
DTM address X
Logical DLT
client
Physical Ethernet
port
Logical Ethernet
switch
Figure 1: A DLT tunnel between two DLT clients. Each DLT client is connected
to one logical Ethernet switch
During normal operation, the logical Ethernet switches forward packets between their Ethernet ports and DLT clients.
The logical Ethernet switch can either operate as a bridge or as a learning bridge, in which case it can only interconnect
two logical Ethernet interfaces, or as a hub or an Ethernet switch in which case it can interconnect two or more logical
Ethernet interfaces to each other.
A DLT client can belong to one or several VLANs. The DLT client should perform ingress filtering and discard all
packets with a VLAN tag outside of the set of VLANs that the client belongs to. The DLT client should also be
associated with a default VLAN. All packets that arrive to the DLT client on its incoming channel without VLAN
information (i.e. VLAN = 0) should be classified as belonging to the default VLAN. This is consistent with the way
ingress filtering works in the 802.1Q Ethernet standard [4].
The operation of the logical Ethernet switch is beyond the scope of the present document.
A DLT client can also be connected as an interface to a regular protocol stack, e.g. an IP routing process. The DLT
client should then behave as a normal Ethernet interface.
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10 ETSI ES 201 803-7 V1.1.1 (2002-05)
4.2 DLE service overview
DTM LAN Emulation allows DTM to be used as a bridge between different segments of an Ethernet network. PDUs
are forwarded through the DTM network based on the destination address of the Ethernet frame. This allows forming
emulated LANs where a number of nodes can behave as if they were connected to the same Ethernet LAN. The
emulated LANs are independent of the DTM topology and are separated from each other by the DTM channelization.
DLE is completely transparent to all connected nodes and the nodes will not know if the node they are sending to or
receiving from is connected to the same Ethernet segment or if the Ethernet frames are sent via DTM. This makes it
possible to connect standard Ethernet equipment to the Ethernet segments.
Each DLE segment consists of one (or more, when using redundant DLE Servers) DLE Server (DLES) and several
DLE Clients (DLECs).
Y
DLE Client
X
Ethernet
B
C Ethernet
DLE Server
DLE Client
D
DLE Client
Figure 2: Example of a DLE network
In figure 2, B and C are DLE Clients in DTM to Ethernet Gateways. D is a DLE Client in a node with direct DTM
connectivity. X and Y are two Ethernet attached nodes. All the Ethernet nodes in the picture have connectivity on the
Ethernet level without passing through any router.
5Systemoverview
5.1 DLT system overview
The DTM LAN Transport (DLT) is a very simple protocol using a single protocol message (DLT_REGISTER) that the
clients use to register with each other and perform an optional authentication. When the clients have registered, they can
send Ethernet PDUs encapsulated in DCAP-1 between them.
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11 ETSI ES 201 803-7 V1.1.1 (2002-05)
5.1.1 Channels in DLT
To connect two DLT clients to each other, one (or several) DTM channels are established in each direction. Each
channel should be established by the sender for that channel. The bit rate of the channel is configured at the source.
The Channel Multiplexing Identifier (CMI) in the DCAP-1 header is used to multiplex traffic on the channels. There are
three different values defined for DLT. One is used for DLT control messages, one for Ethernet packets without a
VLAN tag and one for Ethernet packets with a VLAN tag. The reason for having two different CMI values for Ethernet
packets is that the packet format can then be optimized to make sure that the Ethernet data in the packet is always 64-bit
aligned. The use of untagged transport format is limited to point-to-point Ethernet transport where the external interface
does not use VLAN tagged format.
The Ethernet broadcast and multicast traffic is bound to a DTM channel (unicast or multicast). This implies that the
broadcast or multicast traffic only reach the connected clients.
5.1.2 DLT client traffic forwarding
The DLT client should forward all PDUs (unicast, multicast and broadcast) that it receives from the logical Ethernet
switch on its outgoing channel. All PDUs that it receives on the incoming DTM channel should be forwarded to the
logical Ethernet switch.
All Ethernet PDUs forwarded between the DLT client and the logical Ethernet switch should have a VLAN associated
with it. If no VLAN tag is present on the incoming Ethernet frame a default VLAN is attached to the frame.
5.2 DLE system overview
A DLE segment connects a number of DLE Clients on Ethernet MAC layer, i.e. to the participating nodes it looks as if
they are all connected to the same Ethernet LAN. In each DLE segment, there are one or several DLE Servers and one
or several DLE Clients.
The DLE Server provides the following functions:
1) Address resolution between Ethernet and DTM egresses;
2) Forwards multicast and broadcast traffic to all DLE Clients;
3) Forwards unicast traffic from a DLEC when a direct channel to the destination DLEC has not been established. It
also forwards packets for which an addresses resolution in the ingress DLEC has not been performed.
If more than one DLE Server is used in a DLE segment, they act as backups for each other. The DLE Server can be
located anywhere in the DTM network as long as the node where the DLES is running has DTM connectivity to each of
the other nodes.
The DLE Client forwards Ethernet frames to other DLE Clients in the DLE segment based on address information
distributed from the DLE Server. The information is retrieved from the DLE Server by an address resolution process. If
no relevant address resolution is present in the DLE Client or if there is not a direct channel established to the
destination DLE Client, the Ethernet frames are forwarded to the DLE Server. As soon as the address is resolved and/or
the channel is established, the Ethernet frames should be directly sent to the destination DLE Client.
The DLE Client can be an interface towards higher layer protocols, such as IP, or in an interworking function (bridging)
between DTM and Ethernet.
A DLEC operates on the Ethernet MAC layer and forwards Ethernet frames between one or several Ethernet interfaces
and other DLECs. Such DLEC can serve several Ethernet attached nodes simultaneously.
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12 ETSI ES 201 803-7 V1.1.1 (2002-05)
5.2.1 Channels in DLE
In a DLE segment with a single DLE Server, there are three different types of channel: Client-to-Client Channel (CCC),
Client-to-Server Channel (CSC) and a Server-to-Clients Channel (SCC). Note that there is no channel from the DLE
Server to a specific DLE Client. This means that all traffic from the DLES to a specific DLEC is sent on the broadcast
SCC. Consequently, the DLECs filters messages received on the SCC that are not destined to the specific DLEC.
For redundant DLE Servers, there is also a Server-to-Server Channels (SSC). Each DLE Server in a DLE segment
establishes one SSC to all other DLE Server in the segment. These channels are used to forward messages between the
peer DLE Servers. The SSC is a DTM multicast channel.
To establish a channel to a DLEC or a DLES, the DTM address, DSTI number of the client and a well-known DST
value as specified in ES 201 803-2-2 (see Bibliography) is used.
Each channel used in a DLE segment is used only for a single DLE segment, thus DTM separates the traffic between
the DLE segments.
5.2.2 Packet forwarding in the DLE Client
The DLE Client forwards all packets that it receives from the logical Ethernet switch to exactly one of its outgoing
channels. The channel is selected based on the VLAN and destination MAC address of the packet. If the destination
MAC address is a multicast MAC address, then the packet should be sent on the CSC.
If the destination MAC address is a unicast address, the VLAN and destination MAC address should be looked up in the
address table of the DLE Client. This lookup can yield three different results:
1) There is an entry in the table with a reference to an open CCC. The packet should be sent on this CCC.
2) There is an entry in the table but there is no open CCC to that DLE Client. Send the packet on the CSC. A new
channel should be opened to the DLE Client that the packet should have been sent to.
3) There is no entry in the table. Send the packet on the CSC. Initiate an address resolution request.
All Ethernet packets that the DLE Client receives on one of its incoming DTM channels should be sent to the logical
Ethernet switch unless they have been received on the SCC and they have a source MAC address and VLAN that can be
found in the Local MAC-Address table.
5.2.3 Address learning in the DLE Client
The DLE Client learns about MAC addresses that can be reached via the other DLE Clients connected to the same DLE
segment by issuing Address Resolution Requests to the DLE Server and listening for Address Resolution
Announcements sent from the DLE Server.
The DLE Client learns about MAC addresses that can be reached via other interfaces on the logical Ethernet switch that
it is connected to either by explicitly asking the Ethernet switch for that information or by looking at the source MAC
address of all packets delivered to the DLE Client from the logical Ethernet switch. This information is stored in a local
MAC-Address table.
All address information should be associated with a VLAN, meaning that all address lookups and learning should be
made on a combination of MAC address and VLAN.
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13 ETSI ES 201 803-7 V1.1.1 (2002-05)
5.2.4 Redundant DLE Servers
The redundant DLE Server mechanism makes it possible to run a number of DLE Servers for a single DLE segment
without introducing inconsistency between the servers and allows for a simple implementation.
The basic idea is to have two or more DLE Servers that are equivalent. Protocol wise, it does not matter which DLE
Server the clients connect to, or even whether all clients connect to the same server. In reality, it is probably easier to
manage the network if all clients are configured in the same way, with one DLE Server as primary server and another as
secondary. But in the case of partial connectivity losses in the network, it might happen that some clients connect to one
DLE Server and some to another anyway.
All DLE Servers that serve the same DLE segment are connected to each other via Server to Server channels (SSCs).
All traffic that a DLE Server receives from a DLE Client must be forwarded to the other DLE Servers using the SSCs.
Redundant DLE Servers are used to increase the availability of the server functionality and not to load balance between
the servers. All DLE Servers process all Ethernet broadcasts in a DLE segment and all address resolution requests that
can not be answered from the server's cache.
5.3 VLAN Support
VLANs are used to restrict which Ethernet data frame can be forwarded on a DLT-tunnel/DLE-segment. DLT and DLE
Clients should have a set of allowed VLANs associated with it. This means that the DLT/DLE Client should only send
packets with VLANs in this set out on DTM channels and only accept Ethernet data frames to receive belonging to a
VLAN in this set from DTM channels. The DLT client may also send out Ethernet data frames without VLAN
information (i.e. with VLAN=0) on DTM channels. These Ethernet data frames should be classified to belong to a
default VLAN as configured in the receiving DLE/DLT client. All Ethernet data frames received by a DLT/DLE Client
with a VLAN that is not in the set of allowed VLANs should be discarded.
VLAN information is encoded in the Ethernet data frame as described in IEEE 802.1Q [4], i.e. as four bytes after the
MAC source address of the Ethernet data frame. Additionally, VLAN information is always transmitted before the
Ethernet data frame (see clause 9). The extra VLAN information before the Ethernet data frame is added to optimize the
transfer of untagged packets with VLAN information across a DLE/DLT channel. Instead of adding a VLAN tag per the
IEEE 802.1Q [4] standard by modifying the Ethernet data frame, the sending client can simply add the VLAN
information before the PDU and transmit it unmodified. The receiving client should interpret the Ethernet data frame as
if it had been tagged with the VLAN tag supplied before the Ethernet data frame.
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14 ETSI ES 201 803-7 V1.1.1 (2002-05)
6 Service Interfaces
6.1 Transport view
Ethernet
Bridge/Switch
function
M_UNITDATA.indication
M_UNITDATA.request
Ethernet /DTM
Interworking
function
DCAI
DCAP-1
Figure 3: Transport view of Ethernet Interworking function
For the transport of Ethernet over DTM the Ethernet/DTM Interworking function utilizes the internal bridging interface
for Ethernet bridges [3]. The internal bridging interface does not have a specific name but the primitives used are
M_UNITDATA.request for Ethernet data towards the Ethernet/DTM Interworking function and
M_UNITDATA.indication from the Ethernet/DTM Interworking function.
To transport the Ethernet packets over DTM, the Ethernet/DTM Interworking function uses the DCAI service interface
of DCAP-1 (see ES 201 803-2-2, Bibliography).
NOTE: Within the Ethernet specification a procedural pseudo-code form is used form the formal modelling
where as DTM otherwise uses the G.805/G.806 style formal modelling for transport. For the DTM
management, a G.805/G.806 style TNRM will be used. The interface towards the MAC layer is done in
the style of the Ethernet specification.
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15 ETSI ES 201 803-7 V1.1.1 (2002-05)
6.2 Control view
Network
MIB
management
Ethernet /DTM
Interworking
function
DCMI
MIB
Channel
Management
module
DCCI
DCP
Figure 4: Control view of Ethernet Interworking function
For the control of the Ethernet/DTM Interworking function there are interaction with the Network Management System
and the Channel Management module. The Channel Management module handles the set up, removal and capacity
modifications of channels. Furthermore, the Channel Management module handles retries for channel establishment and
provides network management functions for alarm and status information concerning the channels. The interface where
the Ethernet/DTM interworking function instructs channel operations are called DTM Channel Management Interface
(DCMI) (see ES 201 803-2-1, Bibliography). The network management interface towards the Ethernet/DTM
Interworking function is used to provision and configure the transport services apart from the normal management
functions such as status gathering and configuration.
The DLE Server and DLE Clients provide a management interface to the upper layers. The details of this interface are
not part of the present document.
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16 ETSI ES 201 803-7 V1.1.1 (2002-05)
7 Detailed Protocol Description
7.1 DCMI interaction of DLE and DLT
Both DLT and DLE use DTM channels to exchange protocol messages between the different entities. Before the
message exchange can start, the channels need to be established to obtain the desired connectivity. The establishment of
channels is performed by the DLT client, DLE Client or DLE Server interacting with the Channel Management module
through the DTM Channel Management Interface (DCMI).
DLT/DLE Source DCMI DCMI Destination DLT/DLE
DCMI_CONNECTION_ESTABLISH
DCMI_ICHANNEL_RECEIVE
DCMI_ICHANNEL_ACCEPT
DCMI_OCHANNEL_ESTABLISHED
Figure 5: Channel establishment using DCMI
The establishment of a channel between two protocol entities operates according to the following principles. The
originating entity starts the establishment of channels by issuing a DCMI_CONNECTION_ESTABLISH to the channel
manager. This results in that the channel manager tries to set up a channel to the remote node of the DLT connection. At
the remote node, the request arrives to the remote DLT client as a DCMI_ICHANNEL_RECEIVE from the channel
manager. The remote DLT client replies with a DCMI_ICHANNEL_ACCEPT to the channel manager that in turn
replies to the originating node. The originating DLT client receives a DCMI_OCHANNEL_ESTABLISHED when the
channel is established. The interaction with DCMI results in DCP signalling between the nodes as described in
ES 201 803-2-2 (see Bibliography).
If a channel fails to be established, the channel manager module will retry to establish the channel with a certain
interval. The reestablishment interval between retries will increase exponentially up to a certain maximum level. This is
done to prevent excessive signalling in the network and is handled by the channel management module. When the
algorithm has reached the max interval, there will be an alarm generated for each unsuccessful retry. The details of the
reestablishment of channels are specified in ES 201 803-2-2 (see Bibliography).
DLT/DLE Source DCMI DCMI Destination DLT/DLE
DCMI_CONNECTION_TEARDOWN
DCMI_ICHANNEL_DOWN
DCMI_CONNECTION_DOWN
Figure 6: Channel removal using DCMI
ETSI
17 ETSI ES 201 803-7 V1.1.1 (2002-05)
When a channel is torn down, this can be a result of the originating entity or the destination entity removes the channel,
or that there is a network fault resulting in that a DTM node removes the channel. An originating node that initiates the
removal of the channel does so by issuing a DCMI_CONNECTION_TEARDOWN to the channel manager that in its
turn issues a DCMI_CONNECTION_DOWN to the protocol entity.
When a channel is removed the remote node (being originating or destination) will experience the same sequence of
events regardless if the remote node or a DTM node removes the channel. For a destination node (of the channel), a
DCMI_ICHANNEL_DOWN is issued by the channel manager to the protocol entity. For an originating node, the
channel manager issues a DCM
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