STPP Slide 1

UDP IssuesUDP Issues

PWE3 – 61th IETF

11 - 11 - 2004

Yaakov (J) Stein

STPP Slide 2

Service Provider ModelService Provider Model

in the standard PWE3 model emulation is PE to PE IWF located at PE AC is native service

PEnativeservice

PSN

PW nativeservice CEPE IWFIWFCE

attachmentcircuit

attachmentcircuit

STPP Slide 3

Enterprise ModelEnterprise Model

PEPSN

PW CEPE IWFIWFCEattachmentcircuit

attachmentcircuit

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 ?

STPP Slide 4

AC possibilitiesAC 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 5

List discussionList 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 6

UDP PW advantagesUDP 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 7

UDP PW disadvantagesUDP 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 stagewhen we already have MPLS and L2TP? (Eric, Richard)

potential security problems (Stewart)

potential congestion control problems (Stewart)

STPP Slide 8

Misc commentsMisc 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 applicationbut for adapting a layer network (Ben)

some comments seem to rule out MPLS PWs too (Yaakov)

STPP Slide 9

Disadvantage rebuttalDisadvantage rebuttal 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 10

ProposalProposal

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