The document discusses the inadequacies of legacy network protocols, particularly TCP/IP, in meeting the demands of emerging technologies like ultra-reliable low-latency communications (URLLC) in 5G networks. It highlights issues such as security vulnerabilities, inefficiencies in handling mobility and multihoming, and performance limitations that lead to increased latency and overhead costs. The document advocates for the adoption of next-generation protocols to better support the future requirements of wireless communication.

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Kevin Smith, Vodafone, ETSI NGP Chair
URLLC, London, November 2017
We need to talk about TCP/IP…
I demand URLLC!

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Ethernet

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Networking protocols have great responsibility!
• Any flaws in protocol design
increase network processing
• Workarounds increase processing and transmission:
and hence latency and cost
• Design parameters must reflect current scenarios

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• Wired access
• No mobility
• Fixed, limited bandwidth
• Not secure
• Application congestion control
• Wireless access
• Frequent mobility
• Volatile high bandwidth
• Security essential
• Network resource contention
2010s

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What are the key problems?

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AMPS

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Addressing
Mobility/Multihoming
Performance
Security
Interface-centric, not application
centric
Slow acceleration,
Huge headers,
End-to-end congestion avoidance,
Wasteful retransmission
Etc.
Mobility signalling storm,
Broadcast of new routes
None =
Expensive/vulnerable overlays;
Well-known ports
And these are NOT solved by IPv6

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TCP/IP report card
 Low application bits per Hz/s
 No native mobility/multihoming
 No native security
 E2E congestion controls
Reduced spectral efficiency
Mobility overlay required
Security overlay required
Radio volatility not considered
Network issue: Network workaround:
ROHC
Mobility anchors, IP porting
IPsec, DDoS controls
Retransmissions, TCP
optimisers
= costly overheads, reduced performance
 No intrinsic QoS/context Best effort delivery DPI/traffic detection

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Hang on…
We’ve pretty much coped with this so far….
Hooray!
(for Moore’s law)

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8K video!
A gazillion new connections!
Ultra low latency VR services!
Frequent mobility/multihoming!
Coming to a network
near you
Timeline 2025-ish

12. Just increasing capacity
does not deliver these goals.

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Number of connections (100x)
Data volume (1000x)
Data throughput (up to 100x) ,
Mobility speed (10x),
Battery lives (up to ten years)
Extreme URLLC requirements!

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• To achieve 5G load scaling, we can throw capacity, NFV, SDN and Network
Slicing at the problem..
• This does not solve URLLC – the network protocols themselves need to
upgraded
IF WE DO
NOTHING:

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So in summary: legacy network protocols
• …struggle today, and are not fit for tomorrow
• …reduce the value of next generation networking
• …will not be able to deliver URLLC

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Alternatives are live now

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Next Generation Protocols
• Academia, operators, vendors: stimulating the discussion across SDOs
• Analysing and testing alternative internetworking protocols
• Manageable, discrete steps (no ocean boiling)
• Work is public, all feedback welcome!
http://www.etsi.org/technologies-clusters/technologies/next-generation-protocols

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Further reading
www.pouzinsociety.org
www.geddes.com
irati.eu
Vodafone Quality of
bandwidth report 2017

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It’s a wrap
kevin.smith@vodafone.com

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The following slides present further
details on the AMPS problems
introduced by TCP/IP…

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AMPS: ADDRESSING
An IP address names the network interface
(aka point of attachment)…
What should be named: the node
that processes the protocol headers
What is wrongly named: the
network interface
1.2.3.4 5.6.7.8
…which is how you get to the target of
the communication – and not the target
itself
This causes problems…

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AMPS: Mobility & Multihoming
This means that to deliver IP packets to the same node
over different interfaces requires routing to different
addresses…
For both multihoming and mobility, the addresses of
the interfaces need to change.
This means:
 IP needs workarounds for mobility and multihoming
 Router tables grow rapidly
 ‘Layer 2.5’ needed for buffer handovers
1.2.3.4 5.6.7.8
Detach
Attach

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Performance: Big headers, Slow Handshakes
• Most fields seldom/never change
in a flow – but sent in every packet
• Big headers = big problem for low-
power IoT devices
• Header compression considered
prohibitively expensive
• Connection Synchronisation based
on handshakes, not timers
• This incurs roundtrips to open and
close
• Adds unnecessary latency

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Performance: acceleration and capacity usage
• Time taken to utilise capacity –adding
capacity does not accelerate this!
• Means short flows never get up to
speed
• TCP limits the amount of data that can be
in flight – historically set for 64K fixed lines
• TCP window scaling workaround has
ceiling of 1.07 GB… meaning another
workaround likely needed soon.

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Performance: Latency and jitter
• Handshakes result in latency
e.g. Google/Microsoft experiments on delay impact, est.
$75M revenue loss.
https://www.thetrainline.com/ reduced the latency of
their website by 300ms their revenue increased by
£8m/yr.
Latency impact on revenue
• Jitter as sending rate varies suddenly
Jitter impact on customer experience
Client-side buffering, VoIP
issues, online gaming

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Performance of TCP in the mobile network
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Noise and retransmissions here reduce throughput, which…
…is typically interpreted as
congestion by TCP endpoints
Either: network proxies TCP to account for these
Meanwhile radio retransmissions are
not in synch with TCP retransmission
1
2
3
4
Or: TCP wastefully retransmits packets…

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Performance: endpoint congestion controls
• Don’t overrun the application – not network!
• End-to-end theory: “endpoints should control
congestion – and play fair…”
• But these are the farthest points from network
congestion!
Network
workaround: TCP
optimisers, rate
limiters

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Performance: fragmentation, retransmission
• IP does not do retransmissions.
• TCP will retransmit a fragment –
but with a different IP packet ID
• = risk of multiple copies of same
fragment
• MTU discovery patch is a security
risk…
• No TCP ACK? Does that mean
delayed? Or lost?
• Retransmission timers don’t account
for queuing or changing routes
• Head of line blocking
RetransmissionFragmentation

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Security: none by default
• Minimal/no authentication in routing protocol, congestion control, flow
control, ICMP messages, etc.
• TCP handshake presents an unnecessary attack vector
• Well-known ports mean attackers know where to target
• Spoofing due to “Fan-in”: multiple connections to same port means server
must rely on values it did not create to distinguish connections
• Lack of native IP security means costly overlay of IPsec

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5G is not one-size fits all
• Just increasing capacity is not the answer
• Consumer and Enterprise services will require a blend of: Latency,
Reliability, Throughput, Pacing, Coverage, Mobility, Durability, Security,
Efficiency
• …for which the network needs context-aware and performant protocols