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TRANSCRIPT
MPLS: The Magic Behind the Myths
Grenville Armitage
Lucent Technologies
Introduction
Reviews key differences (and similarities) between IP routing and emerging MPLS approach
Article highlights MPLS does not offer much as once portrayed – e.g. gigabit forwarding
Fails to point out flaws in vision Contribution related to traffic engineering
Scalability Issues
MPLS provides traffic engineering capabilities – agreed
Benefits of MPLS extend only as far as its deployment
End-to-end solution possible only if entire network MPLS enabled
MPLS is domain specific!
Scalability Issues (contd.)
VoIP packet
Supports MPLS
No MPLS
No QoS guarantee
MPLS is domain specific!!
Stateful Routers
LSR (label-switching routers) keep info about different labels
Labels correspond to states stored in router Routers that keep information are bad Does not mention how to deal with failures
Stateful Routers
12
4
3
PP
??
Lose label information
Loss of Label makes packet Unroutable!
Control and Management
Unclear how QoS characteristics of each LSP managed
Unclear how non-shortest paths for traffic engineering obtained
Human intervention required for router configuration
Complex and error-prone
MPLS not for QoS
Domain specificity and scalability issues in deployment
No standards to designate Type of Service (TOS) bits
MPLS has no end-to-end solution MPLS suffers from static routing problems
Static Routing Problem
1
2
34P
P
P
P
MPLS offers static routing only!
MPLS not for QoS (contd.)
Internet is a significant and rapidly growing carrier of voice traffic
Ineffective and impractical for fluctuating demands of VoIP
MPLS nothing but domain-specific circuit switching
MPLS for VPNs
No automatic encryption of data Susceptible to data leak if a connection is
disrupted Potential for administrator doing wrong
provisioning causing loss of privacy Not clear how MPLS will make use of
encryption for security ISPs must manage routing table for each VPN
Where does MPLS fit ??
Aims to perform a useful function at the wrong layer – not universally useful
LSR, according to IETF specs, expects to speak IP
No strategy for evolving an existing ATM network into MPLS network
No Application-level Routing Intelligence
Need to distinguish different packets on the network
QoS requirements statically determined in MPLS
Can’t make use of application specific knowledge and requirements
MPLS unfit for VoIP
MPLS unaware of application requirements No alternate routing to prevent latency, delay,
packet loss, jitter Static and domain-specificity hurts in long run
Conclusions
MPLS static and non-application aware Suited to core of major networks Can be deployed only in single-domain
environment where all routers are MPLS enabled
No end-to-end solution Guaranteed QoS still elusive
MPLS – No Magic, All Myth!!