ATM Signaling Support for IP over ATM

1
ATM Signaling Support for IP over ATM
Internet Draft draft-ietf-ion-sig-uni4.0-05 Mark
Hieber CS590w April 16, 1998

• Overview
• Protocol Procedures
• Call Establishment
• Information Elements
• Traffic Management Issues
• Conclusion

2
Overview

• Follow up to UNI 3.1 Signaling
• ABR Signaling for Point-to-point Calls
• Traffic Parameter Negotiation
• Frame Discard Support
• Leaf Initiated Join
• ATM Anycast Capability
• Switched Virtual Path (SVP) Service

Not Yet Defined
3
Protocol Procedures

• Section 3 in RFC 1755 requires VC management to
  prevent
• VC Thrashing
• Excessive VC Consumption
• other related problems.

4
Call Establishment

• Signaling messages contain optional and mandatory
  variable length Information Elements

5
Call Establishment (Setup)

• Setup Message - Required Part
• AAL Parameters
• ATM Traffic Descriptor
• Broadband Bearer Capability
• Broadband Low Layer Information
• QoS Parameter
• Called Party Number
• Calling Part Number

6
Call Establishment (Setup)

• Setup Message - Optional Part (not new)
• Calling Party Subaddress
• Called Party Subaddress
• Transit Network Selection

7
Call Establishment (Setup)

• Setup Message - Optional Part (new in 4.0)
• Min Acceptable ATM Traffic Descriptor
• Alt ATM Traffic Descriptor
• ABR Setup Parameters
• ABR Additional Parameters
• Connection Scope Selection
• Extended QoS Parameters
• End-to-end Transit Delay

8
Sample Setup Message
SETUP Information Elements/
Fields Value/(Meaning)
--------------------
--------------- aal_parameters
aal_type 5 (AAL
5) fwd_max_sdu_size_ident 140
fwd_max_sdu_size (xmit IP
MTU value) bkw_max_sdu_size_ident
129 bkw_max_sdu_size (recv
IP MTU, 0 for disallowing return traffic)
sscs_type identifier 132
sscs_type 0 (null
SSCS) traffic_descriptor
fwd_peak_cell_rate_0_1_ident 132
fwd_peak_cell_rate_0_1 (link rate)
bkw_peak_cell_rate_0_1_ident 133
bkw_peak_cell_rate_0_1 (link rate)
traff_mngt_options_ident 191
fwd_frame_discard 1 (on)

9
Information Elements (IE)AAL Parameters

• AAL Parameters
• AAL_Type 5
• fwd_max_sdu_size_identifier 140
• fwd_max_sdu_size 65,535
• bkw_max_sdu_size_identifier 129
• bkw_max_sdu_size 65,535
• sscs_type_identifier 132
• sscs_type 0

Service Data Unit
10
Information Elements (IE)B-LLI Parameters

• Bb_low_layer_information
• layer_2_id 2
• user_information_layer 12

Broadband Low Layer Information
11
Traffic Management Issues(ABR Based)

• ABR uses a rate-based flow control mechanism to
  ensure bandwidth and delay
• We are only concerned with IP over ATM systems
  that do not support IIS
• IP over ATM can support
• CBR CBR with CLR
• ABR, UBR
• VBR (real and non-real time)

12
Traffic Management Issues(ABR Based)

• The ATM Signaling is defined by
• ATM Traffic Descriptor
• BB Bearer Capability IE
• QoS Parameter IE
• Optionally
• Extended QoS IE
• End-to-end Transit Delay IE

13
ATM Traffic Descriptor

• ABR is considered the most natural ASC for best
  effort IP traffic.
• Tagging vs Dropping
• Traffic Parameter Negotiation

14
Tagging vs Dropping

• The Traffic Descriptor IE has a tagging subfield
  to indicate if the network is allowed to tag a
  sources cells.
• Tagging would occur
• if the network is congested
• if the source exceeds the traffic contract rate
• Tagging defines the priority of a cell
• If no tagging, then cells are randomly dropped

15
Traffic Parameter Negotiation

• Negotiation can only occur during setup
• Two IEs are used
• Minimum Acceptable ATM Traffic Descriptor
• PCR (Peak Cell Rate) parameters
• Alternative ATM Traffic Descriptor
• Other Traffic Parameters

16
Broadband Bearer Capability

• A new field has been added to UNI 4.0 called the
  ATM Transfer Capability in the BBC IE that allows
  for specifying the ATM Service Category

17
QoS Parameter

• The use of the QoS parameter is optional if and
  only if the extended QoS IE is included.
• The generic QoS parameter are
• qos_class_fwd
• qos_class_bkw

18
Conclusion

• UNI 4.0 adds the capability for ATM networks
  without IIS to do Signaling for IP
• All ATM Service Classes are supported
• Various levels of support are provided by the
  different Information Elements
• There is ongoing work for support of Leaf
  Initiated Joins, ATM Anycast, and SVP service.