MPLS: The Magic Behind the Myths

1
MPLS The Magic Behind the Myths

• Grenville Armitage
• Lucent Technologies

2
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

3
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!

4
Scalability Issues (contd.)
VoIP packet
No MPLS
Supports MPLS
No QoS guarantee
MPLS is domain specific!!
5
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

6
Stateful Routers
P
1
4
P
2
??
3
Loss of Label makes packet Unroutable!
7
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

8
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

9
Static Routing Problem
P
4
1
P
3
P
P
2
MPLS offers static routing only!
10
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

11
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

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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

13
No Application-level Routing Intelligence

• Need to distinguish different packets on the
  network
• QoS requirements statically determined in MPLS
• Cant make use of application specific knowledge
  and requirements

14
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

15
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!!