Dynamic Parameter Signaling
draft-shah-pwe3-control-protocol-extension-01.txt
Himanshu Shah – Ciena Corp
Hamid Ould-Brahim – Nortel Networks
Agenda
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Overview
Capability learning
Dynamic Signaling
PW Status signaling
Other attribute exchanges
Conclusion
IETF - June 2003
Himanshu Shah
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Overview
• Draft proposes a mechanism and optional extensions to
PWE3 Control signaling to exchange dynamic attributes
of the PW.
• Dynamic attribute exchange is needed for PW status, IP
address for ARP-Mediation and IP+MAC for IPLS.
• Optional parameters field of the label mapping message
used as a generic mechanisms to signal additional
attributes of a PW without requiring to extend the PWid
or Generalized ID FEC.
• The mechanism includes a flexible and simple capability
signaling and update notification.
• The proposal is backward compatible with existing PW
behavior and adapts as well to layer-2 VPN services.
IETF - June 2003
Himanshu Shah
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Capability Exchange
• Need a backward compatible mechanism to
learn about PE device’s capability of exchanging
PW attributes dynamically
• Suggest that a PE device includes all TLVs that it
is capable of exchanging dynamically in the
optional parameter field of initial Label Mapping
Message
• Receiving PE learns exchange-capability-set of
the Sender by noting the presence of TLVs and
adjusting its own capabilities to least common
denominator set with respect to the sender PE
IETF - June 2003
Himanshu Shah
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Dynamic Signaling
• Two methods to signal updates to PW
attributes without withdrawing the FEC
– Re-issue Label Mapping Message with updated TLVs
in Optional Parameter Field
– Issue LDP Notification with VC-FEC and updated
TLVs
• Both method works but draft recommends
LDP Notification message
– Would like to get feedback from WG
IETF - June 2003
Himanshu Shah
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PW status signaling
• Status TLV defined with the value field
indicating forwarding status as up or down
• Only Status of forwarding traffic from AC to PW
is conveyed
• Rules of exchange are defined
– Receiver does not reciprocate when its own status is changed
through actions resulted from processing of received remote
status – important for avoiding deadlock.
– Since Status TLV is included as part of capability signaling in the
first Label Mapping, a remote PE can learn as well the actual
Status of various components of PW and may take appropriate
actions before packets are forwarded.
IETF - June 2003
Himanshu Shah
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Other Attributes Exchanges
• IP Address TLV – Used in ARP Mediation
• IP+MAC Address TLV – Used in IPLS
• QOS TLV – Can be used to request specific
QOS for traffic from remote PE to local PE
• More TLVs can be defined as long as the
methods described in the draft are
followed for capability learning and
signaling
IETF - June 2003
Himanshu Shah
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Conclusion
• Need a generic mechanism to extend signaling in
backward compatible fashion to include
capability signaling and update notification for
Pseudowires.
• Future extensions follow these steps
– Define new TLVs and their processing rules
– Review by PWE3 WG
– If accepted, incurs no changes to the base signaling draft
• Request the methods described in the draft be
adopted as WG item
IETF - June 2003
Himanshu Shah
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