modest networking henning schulzrinne columbia university mind workshop – london, oct. 7, 2002...
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Modest networkingModest networking
Henning SchulzrinneColumbia University
MIND Workshop – London, Oct. 7, 2002Keynote Address
Joint work withMaria PapadopouliHannes Tschofenig
Xiaoming FuJochen Eisl
Robert Hancock*
(Opinions are the speaker’s and may not be shared by the co-authors…)
OverviewOverview
New Realism in networking Multimodal networking Some thoughts on QoS CASP – another attempt at QoS
signaling
New realismNew realism Old notion: build it and they will pay
“Don’t want to be just dumb bit carriers’’ Value add charge exorbitant fees for
shipping special bits Convergence all bits are similar
Cheapest bits win (unless monopolies or regulation interfere)
Almost all of networking is/will be a commodity – we should be proud of it!
Cost of networkingCost of networkingModality mod
espeed $/MB (= 1 minute of 64
kb/s videoconferencing or 1/3 MP3)
OC-3 P 155 Mb/s $0.0013
Australian DSL(512/128 kb/s)
P 512/128 kb/s
$0.018
GSM voice C 8 kb/s $0.66-$1.70
HSCSD C 20 kb/s $2.06
GPRS P 25 kb/s $4-$10
Iridium C 10 kb/s $20
SMS (160 chars/message) P ? $62.50
Motient (BlackBerry) P 8 kb/s $133
Spectrum cost for 3GSpectrum cost for 3G
Location what costUK 3G $590/person
Germany 3G $558/person
Italy 3G $200/person
New York Verizon(20MHz)
$220/customer
Generally, license limited to 10-15 years
Multimodal networkingMultimodal networking = use multiple types of networks, with
transparent movement of information technical integration (IP) access/business
integration (roaming) variables: ubiquity, access speed, cost/bit,
… 2G/3G: rely on value of ubiquity immediacy
but: demise of Iridium and other satellite efforts similar to early wired Internet or some
international locations e.g., Australia
Multimodal networkingMultimodal networking expand reach by leveraging mobility locality of data references
mobile Internet not for general research Zipf distribution for multimedia content
short movies, MP3s, news, … newspapers local information (maps, schedules, traffic
radio, weather, tourist information)
Multimedia data access Multimedia data access modalitiesmodalities
high low
high 7DS 802.11hotspots
low satelliteSMS?
voice (2G, 2.5G)
band
wid
th(p
eak)
delay
A family of access pointsA family of access points
Infostation
2G/3G
access sharing
7DS
hotspot + cache
WLAN
7DS options7DS options
Many degrees of cooperation server to client
only server shares data no cooperation among clients fixed and mobile information servers
peer-to-peer data sharing and query forwarding
among peers
7DS options7DS optionsQuery Forwarding
Host A Host B
query
FWquery
Host C
time
Querying
active (periodic)
passive
Power conservation
on
off time
communication enabled
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
Density of hosts (#hosts/km )
Da
tah
old
ers
(%
) P2P data sharing(power cons.)
P2P data sharing
P2P data sharing & FW(power cons.)
Fixed Info Server
Mobile Info Server
high transmission power
2
Fixed Info Server
Mobile Info Server
P2P
Dataholders (%) after 25 Dataholders (%) after 25 minmin
Host B
Messagerelaying
Host A
messages
Gateway
WAN
Host AWLAN
WLAN
Message relaying with 7DSMessage relaying with 7DS
Quality of Service
Why QoS hasn’t happenedWhy QoS hasn’t happened need to admit failure – “bandwidth too cheap to meter” undemocratic: some traffic is more equal than other dishonest: we only talk about the beneficiaries reminds you of your mom: no, you can’t have that 10
Mb/s now socialist: administer scarcity - we like SUVs (or to drive
100 mph)! “risky scheme”: security exposure – reserve your whole
network niche only: displacement applications (such as
telephony) need QoS touchy-feely: requires cooperation edge-ISP, transit
ISPs, end systems snake oil: add QoS, lose half your router interface
bandwidth
What makes QoS hardWhat makes QoS hard No, it’s not RSVP scaling network has become harder to evolve:
network address translation firewalls high packetization overhead (VPNs, IPv6) nobody can be trusted
to be useful, has to be nearly universally supported (“no, you can’t make calls to AS 123”)
network QoS vs. business class model: “coach is empty, please refund fare”
almost all the time, reserved traffic gets same delay as best effort
applications will switch QoS classes
What makes QoS hardWhat makes QoS hard currently, the ISP interface is IP and BGP
– adding a third one is a big deal trust model ISP or cash model payment model completely unclear for
peering new Internet service model: TCP client
(inside) – server (outside) exception: peer-to-peer on college
campuses network to host: you first, no, you first
What is QoS, really?What is QoS, really? Network transparency
no loss (< 1%) very few delay spikes (< 1%) close to propagation delay
anything else is too hard to explain to users! QoS is just a facet of network reliability
consistent 5% packet loss is much better than 5% probability that network is unavailable for seconds
users are willing to pay for availability traditional QoS may help availability during outage
periods e.g., MCI/UUnet breakdown 10/3/02 DOS attacks failure of load distribution links
CASP = Cross-Application CASP = Cross-Application Signaling ProtocolSignaling Protocol RSVP is being used for lots of things beyond
flow setup: RSVP TE, midcom, … Complex and monolithic
multicast support multiple reservation styles killer reservations and error handling receiver-orientation only non-RSVP region handling interface complexity (LIH)
fairly closely ties QoS to RSVP hard to extract generic signaling protocols
CASP as modular signaling protocol currently a proposal for IETF NSIS group
What is CASP?What is CASP? Generic signaling service
establishes state along path of data one sender, typically one receiver
can be multiple receivers multicast can be used for QoS per-flow or per-class reservation also: firewall setup, TE, programmable networks,
configuration, topology exploration, … avoid restricting users of protocol (and religious
arguments): sender vs. receiver orientation more or less closely tied to data path
router-by-routernetwork (AS)
CASP network model – on-CASP network model – on-pathpath
CASP nodes form CASP chain not every node processes all client protocols:
non-CASP node: regular router omnivorous: processes all CASP messages selective: bypassed by CASP messages with unknown client
protocols
QoS
midcom
QoS QoS
selective
omnivorous
CASP chain
CASP network model – out-CASP network model – out-of-pathof-path
Also route network-by-network can combine router-by-router with
out-of-path messaging
AS 1249 AS15465 AS17
Bandwidth broker
NAC CASP
data
CASP protocol structureCASP protocol structure
client layer does the real work: reserve resources open firewall ports …
messaging layer: establishes and tears down state negotiates features and capabilities
transport layer: reliable transport
client layer
(C)
messaging layer
(M)
transport layer
(T)
scout protocol
UDP
IP router alert
messaging layer
(M)
CASP
Next-hop discoveryNext-hop discovery Next-in-path service
enhanced routing protocols distribute information about node capabilities in OSPF
routing protocol with probing service discovery, e.g., SLP first hop, e.g., router advertisements DHCP scout protocol
Next AS service touch down once per autonomous system (AS) new DNS name space: ASN.as.arpa, e.g., 17.as.arpa use new DNS NAPTR and SRV for lookup
similar to SIP approach
Mobility and route Mobility and route changeschanges
avoids session identification by end point addresses avoid use of traffic selector as session identifier remove dead branch
discovers new route
on refresh
ADD
B=2
DEL (B=2)
B=1
ConclusionConclusion
Until wireless bits are too cheap to meter, try hiding lack of universal high bit density from user
QoS is a reliability mechanism CASP as a new signaling platform