Transcript ppt - dspcsp

UDP Issues
PWE3 – 61th IETF
11 - 11 - 2004
Yaakov (J) Stein
STPP
Slide 1
Service Provider Model
in the standard PWE3 model
 emulation is PE to PE
 IWF located at PE
 AC is native service
CE
native
service
IWF
PE
PW
attachment
circuit
PE
IWF
native
service
CE
attachment
circuit
PSN
STPP
Slide 2
Enterprise Model
there is an alternative model (CE2E)
 emulation is CE to CE (see draft-stein-pwce2e-00)
 IWF located at CE
 what runs over the AC ?
CE
IWF
PE
attachment
circuit
PW
PSN
IWF
PE
CE
attachment
circuit
STPP
Slide 3
AC possibilities
MPLS AC



extend MPLS towards the customer
set up PWs from CEs to PEs
splice (stitch/switch) the access PWs and core PW
UDP/IP AC
 leave MPLS in the core network
 use UDP/IP from CEs to Pes
 terminate UDP/IP at the PE and send over MPLS PW
other AC possibilities




L2TP
MPLS over IP
native service over IP using GRE (when defined)
MPLS over IP using GRE
STPP
Slide 4
List discussion

there was a lively discussion of this issue on the list

over 50 emails from 16 participants

the following 3 slides summarize what was said
STPP
Slide 5
UDP PW advantages

UDP/IP is familiar to enterprise customer base (Stewart)

PW label as UDP Port number reduces overhead (Yaakov)

already extensively deployed for TDM PWs (Yaakov,Stewart)

reuse of AVT protocols (Sasha, Ron, Amnon, Andy)

simplify NAT traversal (Yaakov, Mark)
STPP
Slide 6
UDP PW disadvantages

hard to provide QoS assurances w/o co p2p trail (Neil)
– there should be no layer networks above UDP
– no operator has spoken out

large number of UDP ports - doesn’t scale (Mark)
– less than 64K port numbers altogether
– increases state maintained in NAT/Firewall

need protocol for UDP port signaling (Yaakov)

UDP checksum introduces processing overhead (Mark)

why introduce new PW type at such a late stage
when we already have MPLS and L2TP? (Eric, Richard)

potential security problems (Stewart)

potential congestion control problems (Stewart)
STPP
Slide 7
Misc comments

need to reply to ITU liaison (Stewart)

PWE charter aimed at operators/SPs not customers (Ben, Mark)

wrong, but hard to stop customers from using it (Neil)

no consensus here (Eric)

discussion should be diverted to AVT (Ron, Andy)
– but CE-CE PWs not in AVT charter (Sasha)

UDP OK for VoIP since adapts an application
but for adapting a layer network (Ben)

some comments seem to rule out MPLS PWs too (Yaakov)
STPP
Slide 8
Disadvantage rebuttal






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hard to provide QoS assurances w/o co p2p trail
– QoS similar to LDP based MPLS or L2TP
large number of UDP ports - doesn’t scale
– enterprises do not need many PW labels
– scales better than VoIP presently being deployed
need protocol for UDP port signaling
– can limit to manual provisioning
– several simple alternatives (draft-stein-pwe3-udp-00.txt)
UDP checksum introduces processing overhead (Mark)
– checksum also useful / may be set to zero
why introduce a new PW type at such a late stage
– has been in charter from the beginning
potential security problems
– LDP and L2TP protocols are similarly unsafe
potential congestion control problems
– similar to L2TP
STPP
Slide 9
Proposal

explicitly limit UDP/IP to enterprise (CE-CE) PWs
– if present charter is only for SPs then need to update

only allow manual provisioning

enterprise responsible for
– security (firewall)
– congestion avoidance (admission control)

if the enterprise requires a large number of PWs
then MPLS access PWs should be used
STPP
Slide 10