Download fibernet-peering - Columbia University

VoIP peering – a snapshot
Henning Schulzrinne
w/Charles Shen
Dept. of Computer Science
Columbia University
http://www.cs.columbia.edu/~hgs
May 22, 2006
Overview
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•
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•
•
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Review: What is VoIP peering?
Why VoIP peering?
Scaling peering to millions of users
Challenges for VoIP peering
Beyond PSTN replacement
Resources
May 22, 2006
What is VoIP peering?
• Definitions from IETF SPEERMINT Working Group:
– “Peering … refers to the negotiation of reciprocal interconnection
arrangements, settlement-free or otherwise, between operationally
independent service providers.” (draft-ietf-speermint-res-and-terminology-01)
– Layer 5 peering refers to interconnection of two service providers for the
purposes of exchanging SIP signaling. Note that in the layer 5 peering case,
there is no requirement for any intervening "Layer 5 Transit Network". Each
service provider is expected to interconnect directly with other service providers,
although a service provider is allowed to interconnect through another domain
(ex: a federation) to act on its behalf. (SPEERMINT, IETF 65)
• Cable Labs
– “The notion of IP Service Peering (and VoIP Peering) … extends the relationship
between network operators above the IP layer, by handling the IP-based services
and applications that can be exchanged.”
May 22, 2006
Why VoIP peering?
• Near-term motivations
– avoid PSTN hops between VoIP service providers
– codify provider trust relationships
– bridge wait until global ENUM
• Longer term motivations
– no PSTN in the middle 
•
•
•
•
advanced signaling services
no transcoding  better audio quality
wideband audio codecs
video, IM, …
– possibly increase in trust
• smaller number of players  spam, spit 
May 22, 2006
Why is VoIP peering needed?
• Non-reasons
– SIP: providers can talk directly to each other if SIP URIs are
available
• sip:[email protected]  look up SIP server for example.com
(NAPTR, SRV) and connect
• email-like  no email peering
– L3: probably best to avoid triangle routing
• Reasons
– E.164 numbering: who serves the customer with +1 212 555
1234?
• absence of global ENUM 
– interoperability
– billing
May 22, 2006
Session interconnect
E.164
number
peer discovery
ENUM lookup of NAPTR in DNS
SIP
URI
aka call routing data (CRD)  derived from ENUM record
service location (lookup of NAPTR and SRV) in DNS
host name
addressing and session establishment
lookup of A and AAAA in DNS
IP
address
routing protocols, ARP, …
MAC
address
May 22, 2006
Peering evolution
VoIP Service Providers interconnect via PSTN
using E.164 numbers for addressing
VSP
VSP
VSP
+4315056416
PSTN Plane
Otmar Lendl, March 2006 (SPEERMINT)
May 22, 2006
VSP
VSP
Messy reality
Private Interconnection Network
Private Interconnection Network
sip:[email protected]
VSP
VSP
Public Internet
PSTN Plane
Otmar Lendl, March 2006 (SPEERMINT)
May 22, 2006
VSP
VSP
VSP
Closed SIP federation
Example: Cable operators
• MSOs want to avoid PSTN traversal
• Call Management Server Signaling (CMSS) = SIP
Administrative Domain 2
Administrative Domain 1
`
`
SIP
MSO A
Zone 1
CMS
CMSS
CMS
MSO B
Zone 3
PSTN
Gateway
SIP
Managed
IP Backbone
CMSS
`
MSO A
Zone 2
PSTN
SIP
SIP
CMS
Servers
CMS
CMSS
`
PSTN
Gateway
PSTN
MSO C
Zone 4
`
PSTN
Gateway
PSTN
Administrative Domain 3
May 22, 2006
Jean-François Mulé, IETF 63
Peering: decomposed model
domain A
May 22, 2006
domain B
draft-penno-message-flows-02
Peering: collapsed model
~~~~

~~~~
~~~~

~~~~
B2BUA
domain A
May 22, 2006
domain B
draft-penno-message-flows-02
Peering authorization
P1
• On-demand
INVITE
– “email model”
– as needed when exchanging
SIP messages
– usually, mutual TLS
authentication
– proposed
SUBSCRIBE/NOTIFY key
exchange
• Static
– established ahead of
signaling
– e.g., TLS or IPsec
– proposed
SUBSCRIBE/NOTIFY key
exchange
May 22, 2006
P2
draft-penno-message-flows-02
100 Trying
SUBSCRIBE w/PeerAuth
401 Unauthorized
SUBSCRIBE w/auth
202 Accepted
NOTIFY w/P2key
INVITE
401 Unauthorized
INVITE + P2Key
INVITE
100 Trying
Role of ENUM in peering
• Core service: look up provider for E.164 number
• ENUM models
– Public ENUM: e164.arpa
– Private ENUM: limited access to DNS records (e.g., by VPN)
– Carrier ENUM:
• Options:
– resolve to subscriber SIP URI
• +1 212 555 1234  sip:[email protected];user=phone
– resolve to neutral peering provider
• +1 212 555 1234  sip:[email protected];user=phone
• peering.com proxy translates to actual provider
– resolve to carrier ENUM DNS server
• +1 212 555 1234  enum.vsp.com  NAPTR query on enum.vsp.com
– service provider identifier (SPID)
• +1 212 555 1234  NXXX
May 22, 2006
ENUM in a Nutshell
•
Take an E.164 number
•
Convert it to FQDN
•
Query DNS for NAPTRs
•
Apply resulting regexs
to get list of URIs:
+1-734-913-4257
7.5.2.4.3.1.9.4.3.7.1.e164.arpa.
e164.arpa.
1.e164.arpa.
4.3.7.1e164.arpa.
x.x.x.1.e164.arpa.
sip:[email protected]
mailto:[email protected]
sip:[email protected]
May 22, 2006
Ben Teitelbaum, John Todd, Dennis Baron:
“ISN Numbers: Fast, Free, and Forever Yours” March 16, 2006 Spring VON, San Jose, CA
Who serves an E.164 number?
• Find “point of interconnection” (PoI) for given E.164
number
• Peering provider can answer question locally
• Likely to have dozens of such peering exchanges and
federations
– each provider will be a member of some subset of these
• Kludge: originating provider asks all its peering providers
in parallel
– via DNS ENUM lookup
• Possibly federate peering providers
– flood number information, pointing to peering ENUM
– multiple resolutions  can’t be DNS
May 22, 2006
Carrier (infrastructure) ENUM
• User ENUM
– “entity or person having the right-to-use of an E.164 number has
the sole discretion about the content of the associated domain
and thus the zone content” (draft-haberler-carrier-enum-02)
– end user as registrant
• Carrier (now, infrastructure) ENUM
– "carrier of record" (COR) as registrant
• Proposal: branch under e164.arpa:
– 4.9.7.1.carrier.e164.arpa or
– 4.9.7.carrier.1.e164.arpa
May 22, 2006
Carrier ENUM
• COR = registrant
– block holder allocated by National Regulatory Authority (NRA)
– "International Networks" (+882) or "Universal Personal
Telecommunications (UPT)" (+878) allocated by ITU
– recipient of a port (service provider)
– has been contracted by a user to route a number assigned to a
user directly (without COR being in the number assignment path)
• corporate network numbers
• 800/900 type numbers in many countries
• Include all E.164 numbers in block
– avoid ability to detect listed vs. unlisted numbers
May 22, 2006
Provider hiding
• Some providers worry about exposing their identity to
competitors
– competitors could target customers for marketing efforts
– unclear if more than theoretical issue
• Solution:
– send calls to peering provider SIP proxy, not directly to VSP
proxy
• ENUM: [email protected]
– peering provider does database (or internal ENUM) lookup
May 22, 2006
Challenge: provisioning ENUM
entries
• Dynamic DNS not suitable: security, scaling
• Options:
– bulk upload via ftp, HTTP, …
– EPP (Extensible Provisioning Protocol) – RFC 3730
• XML-based protocol designed originally for domain number
management
May 22, 2006
SPEERMINT discussion:
federations
• A federation is a group of VoIP service providers / enterprises which
– agree to receive calls from each other via SIP
– agree on a set of administrative rules for such calls (settlement, abusehandling, ...), and
– agree on specific rules for the technical details of the interconnection
• Federations have a unique identifier
• TLS-based
– Public Internet, SIP over TLS, federation acts as X.509 Certification
Authority.
• Private network
– Federation builds its own network; members connect directly over this
network.
• SIP hubs / transit networks
– Calls are routed via a central SIP proxy
May 22, 2006
Otmar Lendl, “The Domain Policy DDDS Application”, IETF 65, March 2006
Domain Policy DDDS basics
• The domain is the key to the destination policy
– Use the DNS as rule store
– No special translation rules necessary
– Infrastructure is in place
• Example:
example.com. IN NAPTR 10 50 "U" "D2P+SIP:fed"
"!^.*$!http://sipxconnect.example.org/!" .
“Regarding SIP, example.com is a member of the federation identified by
this URI.”
• Non-terminal NAPTR for customer domains referring to provider
domains
• Protocol agnostic
– SIP is just a special case
May 22, 2006
Otmar Lendl, “The Domain Policy DDDS Application”, IETF 65, March 2006
Longer-term opportunities for
peering
• Enterprise trunk backup management
– PSTN as primary, VoIP as backup (or vice versa)
• Spam/SPIT prevention
– accountable carriers
– trustable user identification (“caller ID”)
– exchange of abuse information
• Billing and settlements
– if per-call billing
May 22, 2006
ENUM performance
•
Busy hour traffic estimate:
– 0.1 Erlang  2 calls/hour/user
– 100 mio users  roughly 55,000 calls/second  lookup rate
•
Post-dial delay bounds: few seconds
– includes signaling latency
– DNS unlikely to be a significant contributor (except if packet loss)
•
DNS server platform:
– OS: Linux version 2.6.11
– 1 or 2 Intel Pentium 4 CPU 3.00GHz, 1 GB memory
•
DNS servers:
– BIND
– PowerDNS (PDNS)
•
•
•
•
Open Source Authoritative Nameserver
Used by 50% of .de and 20% rest of the world, including e164.org.
Runs on Linux, FreeBSD, NetBSD, OpenBSD, Solaris
Serves data from MySQL, PostgreSQL, LDAP, BIND zone files, …
– Nominum ANS
May 22, 2006
Preliminary Black Box Test
ENUM server
Client 5
Client 1
May 22, 2006
Client 2
Client 3
Client 4
Black-box Comparison Results
IRT
BIND
9.3.2
Nominum
BIND
9.3.0
IRT
PDNS
+ BIND
Nominum
PDNS
+BIND
IRT
PDNS
+MySQL
Nominum
PDNS
+MySQL
Nominum
ANS *
10 M
Records
Load
Pass
Pass
Pass
Fail
Pass
Not Tested
Pass
Queries per
Second
521
143
9,208
N/A
2,051
Not Tested
43,135
Average
Latency (s)
0.190
0.618
0.011
N/A
0.048
Not Tested
0.0016
•All columns denoted as Nominum are from the Nominum white paper
“ENUM Scalability and Performance Testing”.
•The last column, Nominum ANS is tested with 200M records, all the rest are
tested with 10M records.
•PDNS test uses its default settings.
May 22, 2006
PDNS response time – record exists
May 22, 2006
PDNS: Throughput – record exists
May 22, 2006
Throughput: PDNS and caching
May 22, 2006
Throughput – BIND
May 22, 2006
Throughput - ANS
May 22, 2006
ITAD Subscriber Numbers (ISN)
• 4257*260
locally
assigned
Internet Telephony Administrative Domain
(ITAD)
• ITADs
–
–
–
–
Defined by Telephony Routing over IP (TRIP) [RFC3219]
Globally unique
Lots of them (256 through 232-1)
IANA is already set up to allocate
• ISN resolution works just like ENUM
May 22, 2006
Ben Teitelbaum et al, March 2006
ISN in a Nutshell
•
Take an ISN
•
Convert it to FQDN
•
Query DNS for NAPTRs
•
Apply resulting regexs
to get list of URIs:
4257*260
7.5.2.4.260.freenum.org.
freenum.org.
260.freenum.org.
sip:[email protected]
mailto:[email protected]
sip:[email protected]
May 22, 2006
Note: We are working to
ensure that the ISN root
zone will be administered
on behalf of the ISN user
community by a neutral,
non-profit organization.
Following the trial, the root
may or may not be
“freenum.org”.
Ben Teitelbaum, John Todd, Dennis Baron:
“ISN Numbers: Fast, Free, and Forever Yours” March 16, 2006 Spring VON, San Jose, CA
ISN vs ENUM vs SIP AOR
Example
ISN
7031*260
ENUM
+1-734-352-7031
SIP AOR
[email protected]
Familiarity
Huh?
Phone numbers
Email address
Delegating
Authority
IANA
ITU, national government, ICANN, TLD registrars
…
Address Structure local*domain
Hierarchical / geographical local@domain
Portability
With domain owner’s
cooperation
Varies by country
???
With domain owner’s
cooperation
Fragmentation
One space
Public ENUM + multiple
private ENUMs
One space
May 22, 2006
Ben Teitelbaum, John Todd, Dennis Baron:
“ISN Numbers: Fast, Free, and Forever Yours” March 16, 2006 Spring VON, San Jose, CA
Conclusion
• Peering as crucial next step for large-scale VoIP
– weaning off the PSTN…
– needed to get beyond black-phone service
• ENUM as core peering service
– needed as long as phone numbers are in use
– slow transition from private to public ENUM
• Peering is ENUM +
– security associations
– privacy protections (for carrier and users)
– billing and settlements?
• Peering issues
– provisioning of E.164 records
– which peer?
• Need for high-performance service architecture
May 22, 2006
Resources
• ENUM: RFC 3761
– carrier ENUM: draft-haberler-carrier-enum-02
• tel URIs: RFC 3966
• IETF SPEERMINT working group
– definitions and terminology: draft-ietfs-speermint-reqs-and-terminology01
– message flows: draft-penno-message-flows-02
• CableLabs VoIP Peering RFI
• GSMA GRX/IPX Requirements
• ECMA/TISPAN Next-Gen Corporate-Core Interconnection
Requirements
• SIP Forum IP PBX / Service Provider Interoperability
• ISNs: http://www.internet2.edu/sip.edu/isn/
May 22, 2006