10-10-2012, 11:21 AM
Requirements for Edge-to-Edge Emulation of TDM Circuits over Packet Switched Networks
Requirements for Edge.ppt (Size: 52 KB / Downloads: 39)
Edition History
Initial Edition: draft-riegel-pwe3-tdm-requirements-00.txt
presented on IETF-54 in Yokohama
covered only pseudo-wire-emulation of signals belonging to the PDH hierarchy (T1, E1, T3, E3)
Towards a generic TDM emulation requirements document
Intensive discussions of a TDM design team during IETF-55 in Atlanta
Sasha Vainshtein Axerra Networks
Yaakov Stein RAD Data Communication
Prayson Pate Overture Networks, Inc.
Tom Johnson Litchfield Communication, Inc.
Ron Cohen Lycium Networks
Tim Frost Zarlink Semiconductor
Max Riegel Siemens (Editor)
Inclusion of requirements for SDH/SONET emulation
Clarification of emulated service types
Discussion of synchronization issues
Issues raised: Packet size and delay
There was an intensive discussion about packet size
The current I-D states:
7.5 PSN bandwidth utilization
1. The encapsulation layer SHOULD allow for an effective trade-off between the following requirements:
1. Effective PSN bandwidth utilization. Assuming that the size of encapsulation layer header does not depend on the size of its payload, increase in the packet payload size results in increased efficiency.
2. Low edge-to-edge latency. Low end-to-end latency is the common requirement for Voice applications over TDM services. Packetization latency is one of the components comprising edge- to-edge latency and decreases with the packet payload size.
It seems we might add here:
edge-to-edge delay should be independent of the service rate for NxDS0
has special importance for NxDS0 because the service rate may vary from 64 kbit/s to 1920 kbit/s
Issues raised: Congestion control
The current I-D states:7.8 Congestion Control
Edge-to-edge emulation of TDM circuits may result in constant bit rate flows in the PSN. When transferred over the Internet congestion control MUST be provided by appropriate means. It MUST be avoided that all pseudo wires in the congested network are switched down simultaneously or are reestablished again simultaneously to avoid unstable behavior of the network.
Very general statement; should be more specific.Probably adopt ideas mentioned on the list, e.g.:
A suitable strategy might be:1) Notify the NSP that the PW is experiencing congestion2) Wait whilst the NSP takes some action to reduce the offered load3) If congestion still experienced, shut down the PW
How to become TCP-friendly?
Relation to <draft-ietf-pwe3-requirements-05.txt>?Congestion control is only mentioned in <draft-ietf-pwe3-arch-02.txt>