802.1d – expedited traffic
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Sept 23, 2004 CS573: Network Protocols and Standards
1
802.1D – Expedited Traffic
Network Protocols and Standards
Autumn 2004-2005
Sept 23, 2004 CS573: Network Protocols and Standards 2
Expedited Traffic Preview Traffic types
Network Control Voice Video Controlled Load Excellent Effort or CEO Effort Best Effort Background
Sept 23, 2004 CS573: Network Protocols and Standards 3
Traffic Types Problem: Different applications with
varying data communication requirements Solutions:
Design a network according to given requirements
Differentiate between traffic classes For different applications, IEEE enumerated
traffic types in a typical LAN environment
Sept 23, 2004 CS573: Network Protocols and Standards 4
Traffic Types: Network Control Network Control
Characterized by “must get there” requirement
Maintain and support the network infrastructure
Placed above “voice” Meaningless to require that the [voice]
traffic be delivered with a maximum delay when the correct [network] infrastructure is absent …
Sept 23, 2004 CS573: Network Protocols and Standards 5
Traffic Types: Voice Interactivity is the desired feature End-to-end delay of 100ms to
150ms What about the delay on a single
LAN? 10ms is specified
Data Rates are several kb/s to few tens kb/s
Sept 23, 2004 CS573: Network Protocols and Standards 6
Traffic Types: Video Interactivity may not be the
required feature Specifications for Interactive video
such as Video Conferencing aren’t too different from the voice specifications
For non-interactive video High data rates (1Mb/s to 8Mb/s)
Achieving 10ms delay is difficult LAN delay of 100ms is specified
Sept 23, 2004 CS573: Network Protocols and Standards 7
Traffic Types: Controlled Load Important business applications subject
to some form of “admission control” Critical but no delay requirements Some biz applications might be more
appealing if the response is better As if a user is using the network alone!!!
Load on the network is fairly controlled More control on the “other” traffic Idea came from IntServ
Sept 23, 2004 CS573: Network Protocols and Standards 8
Traffic Types: Excellent Effort Excellent Effort or CEO best-effort Applicable to data traffic
Requirements are traditionally not very stringent
File transfer will happen… when? Some important people in a
company might need faster data transfers without having to wait for long
Sept 23, 2004 CS573: Network Protocols and Standards 9
Traffic Types: Best Effort LAN traffic as we know today The default traffic class
Sept 23, 2004 CS573: Network Protocols and Standards 10
Traffic Types: Background Bulk transfers Other activities permitted on the
network but should not impact the use of network by other applications
Example: backups
Sept 23, 2004 CS573: Network Protocols and Standards 11
How Many Types? Every switch is not able to handle all
types of traffic How many traffic types should be used?
Initial answer: 2 High and Low People came up with other applications and
scenarios Finally 8 levels were specified
Only 7 traffic classes have been uniquely identified so far
Sept 23, 2004 CS573: Network Protocols and Standards 12
Traffic Type to User Priority Mapping
User Priority
Acronym Traffic Type
1 BK Background
2 -- Spare
0 (default) BE Best Effort
3 EE Excellent Effort
4 CL Controlled Load
5 VI Video
6 VO Voice
7 NC Network ControlAll manufacturers should agree to this mapping…
Sept 23, 2004 CS573: Network Protocols and Standards 13
User Priority Regeneration On an incoming port of a bridge, you
would like to maintain the priority Not all MAC layer frame formats include
priority field in their headers IEEE 802.5 token ring defines 8 priority levels Ethernet, IEEE 802.3 do not include a priority
field For maximum flexibility, user priority for
frames received on a given port may be regenerated according to information that is preset by management procedures
Sept 23, 2004 CS573: Network Protocols and Standards 14
Traffic Type to User Priority Mapping
User Priority
Default Regenerated
Priority
Range
0 0 0-7
1 1 0-7
2 2 0-7
3 3 0-7
4 4 0-7
5 5 0-7
6 6 0-7
7 7 0-7User priority value for the outgoing frame should be either thevalue received in the frame itself (by default!) or mappedto some value in the range 0—7 (preset for that port!).
Sept 23, 2004 CS573: Network Protocols and Standards 15
Example
H1 sends voice to D1H2 sends controlled load to D2H3 sends best effort to D2
What should Bridge B1 do?
Sept 23, 2004 CS573: Network Protocols and Standards 16
Example
Sept 23, 2004 CS573: Network Protocols and Standards 17
Example
- Bridge B1 sets priority of incoming frames on port 2(traffic type to user priority mapping)
- Bridge B1 places all the frames in the outgoing queues (user priority to traffic class mapping)
Sept 23, 2004 CS573: Network Protocols and Standards 18
User Priority to Traffic Class Mapping
For a given bridge, there may be more than one traffic class specified, thus one transmission queue for each traffic class
Frames are assigned to the transmission queues on the basis of their user priority, using the traffic class table that is part of the state information associated with that port
Sept 23, 2004 CS573: Network Protocols and Standards 19
RecommendedTraffic Type to Traffic Class
Mapping#Queu
esDefining Traffic Type
1 BE
2 BE VO
3 BE CL VO
4 BK BE CL VO
5 BK BE CL VI VO
6 BK BE EE CL VI VO
7 BK BE EE CL VI VO NC
8 BK -- BE EE CL VI VO NC
Sept 23, 2004 CS573: Network Protocols and Standards 20
RecommendedUser Priority to Traffic Class
MappingNumber of Available Traffic Classes (Queues)
1 2 3 4 5 6 7 8
User
PRIORITY
0 0 0 1 1 1 1 1 2
1 0 0 0 0 0 0 0 0
2 0 0 0 0 0 0 0 1
3 0 0 1 1 1 2 2 3
4 0 1 1 2 2 3 3 4
5 0 1 1 2 3 4 4 5
6 0 1 2 3 4 5 5 6
7 0 1 2 3 4 5 6 7
Sept 23, 2004 CS573: Network Protocols and Standards 21
ExampleUser Priority to Traffic Class
Mapping
The number next to the queues represents the priorityclass for that queue; higher values represent higherpriority. The next step is to determine the frameselection and the outgoing priority of the frame
Consider the previous example:
Sept 23, 2004 CS573: Network Protocols and Standards 22
Selection of Frames for Transmission According to IEEE 802.1D (portion of new
802.1D that was previously 802.1p), selection of frames for transmission is based on highest priority first Frames are selected from a given transmission
queue if all the queues corresponding to numerically higher values of traffic supported by that port are empty at the time of selection
Other algorithms as selected by the management may also be supported
Sept 23, 2004 CS573: Network Protocols and Standards 23
Outbound Access PrioritiesUser
PriorityOutbound Access Priority for different MAC methods
8802-3 8802-4 8802-5(usual)
8802-5(alter)
8802-6 802.9a 8802-12
FDDI
0 0 0 0 4 0 0 0 2
1 0 1 1 4 1 0 0 0
2 0 2 2 4 2 0 0 1
3 0 3 3 4 3 0 0 3
4 0 4 4 4 4 0 4 4
5 0 5 5 5 5 0 4 5
6 0 6 6 5 6 0 4 6
7 0 7 6 6 7 0 4 6
Sept 23, 2004 CS573: Network Protocols and Standards 24
ExampleFrame Selection and outbound Priority
Mapping
Sept 23, 2004 CS573: Network Protocols and Standards 25
Conclusions Expedited Traffic Capabilities
Not intended to provide guaranteed quality of service
Allows the transmission of time critical data to be expedited when it is in competition with other non time critical data
Sept 23, 2004 CS573: Network Protocols and Standards 26
Selective Multicast: Preview Part of IEEE 802.1D standard Reasons of Selective Multicast
Broadcasting of multicast traffic overloads slower links
Even for high speed links, transmitting something that no one will use is not a good idea
Solution Allow users to explicitly indicate their interest in
receiving traffic on given multicast addresses
Sept 23, 2004 CS573: Network Protocols and Standards 27
Use of FDBs Bridges maintain filtering databases for
unicast addrresses Static Entries
Explicitly configured by management Dynamic Entries
Automatically entered into the FDB by the normal operation of the bridge
Each entry (static or dynamic) consist of: A MAC address specification A port map specifying the filtering state for
that MAC address
Sept 23, 2004 CS573: Network Protocols and Standards 28
Basic Filtering Services A bridge must support these
services Allow the specification of:
For individual MAC addresses Static entries Dynamic entries
For a specific group MAC address Static entries No static entry Broadcast
Sept 23, 2004 CS573: Network Protocols and Standards 29
Extended Filtering Services Add the following capabilities
For individual addresses Static entries may contain a value which indicates
that the dynamic filtering information should be used For a specific group MAC address
Static entries may contain a value which indicates that the dynamic filtering information should be used
Group registration entries that are created and maintained through the use of GMRP protocol
Entries corresponding to all group addresses which may not have a specific group MAC address entry OR unregistered group addresses
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