1. Características y
evolución de las redes
LAN y WAN para ofrecer
servicios de
Comunicación Unificada
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2. Buenos Días a todos…!
Systems Engineer
Public Sector
arprieto@cisco.com
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3. The Elements of Unified
Communications
Voice Mail/ Web /Audio/ XML LDAP
Unified
Messaging
Video Phone
Services
Directory Applications
Conferencing
UC UC PSTN/IP
Media
Endpoints Resources
Processing Gateway UC Infrastructure
Agents
Gateway/ Comms
MTP Survivable Endpoints
GK
Remote
Xcode PSTN
Conf
Si
IP WAN
Si Branch Access
WAN Router Switch Branch
Access Distribution/
Aggregation
Campus
Switch Core Switch Router Network Infrastructure
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4. Network Infrastructure Agenda
 Building a Campus Network
 QoS in the Campus
 QoS in the WAN
 Qos in the Wireless LANs
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5. Systems Architecture
Bay Bridge: Golden Gate Bridge:
 Original cost in 1936: $1.1 billion  Original cost to in 1937:
(adjusted for today’s $) $446 million (adjusted for today’s $)
 Estimated cost to expand: $6.2
billion… and climbing
A Poorly Planned Architecture A Well Planned Architecture
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6. Building a Campus Network
Hierarchical Network Design
Without a Rock Solid Foundation the Rest Doesn’t Matter
• Offers hierarchy – each layer has specific
Access role
• Modular topology - building blocks
• Easy to grow, understand, and
Distribution troubleshoot Si Si
• Creates small fault domains – Clear
demarcations and isolation
• Promotes load balancing and redundancy
Core
• Promotes deterministic traffic patterns Si
Si
• Incorporates balance of both Layer 2 and
Layer 3 technology, leveraging the
strength of both
Distribution
• Utilizes Layer 3 Routing for load Si Si
balancing, fast convergence, scalability,
and control
Access • Sub second convergence possible
Building Block
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7. Building a Campus Network—The
Access Layer
Feature Rich Environment—Not Just About Connectivity
To Core
Si Si Distribution
Access
VLANS do not span access switches
 Aggregates network end-points  Catalyst® integrated security features
 Layer 2/Layer 3 feature rich environment; 802.1x, Port security, DHCP snooping,
convergence, HA, security, QoS, IP Dynamic ARP Insp, IP Source Guard, etc.
multicast, etc  Automatic phone discovery, conditional trust
 Intelligent network services: QoS, trust boundary, Power Over Ethernet, auxiliary
boundary, broadcast suppression, IGMP VLAN, etc.
snooping  Spanning tree toolkit: Portfast, UplinkFast,
 Intelligent network services: Rapid BackboneFast, LoopGuard, BPDUGuard,
PVST+, EIGRP, OSPF, DTP, PAgP, UDLD, BPDUFilter, RootGuard, etc.
Session ID etc.
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8. Campus Network—Access Layer
Voice and Data VLANs
Phone VLAN = 110 PC VLAN = 10
(VVID) (PVID)
802.1Q encapsulation Native VLAN (PVID) No
with 802.1p Layer 2 Configuration Changes
CoS Needed on PC
 During initial CDP exchange phone is configured with a Voice
VLAN ID (VVID)
 Phone also supplied with QoS configuration via CDP TLV fields
 Quality—Separation of broadcast domains i.e. phones and PCs
are on separate subnets
 Security—Different network policies for different subnets; WORM
attacks can be contained to the PC VLANs.
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9. Building a Campus Network—The
Distribution Layer
Policy, Convergence, QoS, and High Availability
Distribution
Si Si Si Si
Access
 Availability, load balancing, QoS and  EIGRP/ OSPF - Route summarization,
provisioning are the important passive interfaces to access layer, sub
considerations at this layer second convergence possible with timer
 Aggregates wiring closets (access adjustment, redundant path load sharing
layer) and uplinks to core  HSRP or GLBP to provide first hop
 Use Layer 3 switching in the redundancy, sub second convergence
distribution layer possible with timer adjustment
 Protects core from high density  Spanning tree features ( Only if needed ):
peering and problems in access layer Setting STP Root, Root Guard, Rapid
PVST+—Per VLAN 802.1w
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10. Building a Campus Network—The
Core Layer
Scalability, High Availability, and Fast Convergence
Core
Distribution
Access
 Backbone for the network—connects network building blocks
 Performance and stability vs. complexity—less is more in the core
 Aggregation point for distribution layer
 Tune routing protocol timers for sub second convergence
 Separate core layer helps in scalability during future growth
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 Use hardware accelerated services only to maintain performance
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11. Campus Design Best Practices
First Hop Redundancy
 Used to provide a resilient
default gateway/first hop 1st Hop Redundancy
address to end stations
 HSRP, VRRP, and GLBP Si Si Si Si Si Si
alternatives
 VRRP, HSRP and GLBP
provide millisecond timers Layer 3 Equal Layer 3 Equal
and excellent sub second Cost Link’s
Si Si
Cost Link’s
convergence performance
 VRRP if you need multi-
vendor interoperability Si Si Si Si
Si Si
 GLBP facilitates uplink load
balancing
 Preempt timers need to
WAN Data Center Internet
be tuned to avoid black-
holed traffic
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12. Campus Design—Routed Access Layer
 Tune CEF load balancing
 Match CatOS/IOS Ether-channel
settings and tune load balancing Si Si
Core
 Summarize routes
towards core
 Filter routes towards the access Distribution
 Disable Ether-channel Si
Layer 3
Si
unless needed P-t-P Link
 ―Set port host‖ on access
layer ports:
Disable Trunking
Disable Etherchannel Access
VLAN 20 Data VLAN 40 Data
Enable PortFast 10.1.20.0/24 10.1.40.0/24
VLAN 120 Voice VLAN 140 Voice
 RootGuard or BPDU-Guard 10.1.120.0/24 10.1.140.0/24
 Use security features
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13. Building a Campus Network
Summary
 Access layer Access
Rapid Per-VLAN Layer 2
spanning-tree
( PSVT +)
Rootguard
Portfast Distribution
Layer 3
UplinkFast
Server Farm
Layer 3 to the edge ?
Core
 Distribution Layer Layer 3
HSRP/GLBP with load
balancing
OSPF/EIGRP Distribution
configured for fast Layer 3
convergence
 Core Layer
Access
OSPF/EIGRP
configured for fast
Layer 2
convergence WAN Internet PSTN
http://www.cisco.com/en/US/netsol/ns656/networking_solutions_design_guidances_list.html#anchor2
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14. Network Infrastructure Agenda
 Building a Campus Network
 QoS in the Campus
 QoS in the WAN
 QoS in the Wireless LANs
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15. Enabling QoS in the Campus
Traffic Profiles and Requirements
Voice Video-Conf Data
 Smooth  Bursty  Smooth/bursty
 Benign  Greedy  Benign/greedy
 Drop sensitive  Drop sensitive  Drop insensitive
 Delay sensitive  Delay sensitive  Delay insensitive
 UDP priority  UDP priority  TCP retransmits
Bandwidth per Call IP/VC has the Same Traffic patterns for
Depends on Codec, Requirements as VoIP, Data Vary Among
Sampling-Rate, but Has Radically Applications
and Layer 2 Media Different Traffic Patterns
(BW Varies Greatly)
 Latency ≤ 150 ms  Latency ≤ 150 ms Data Classes:
 Jitter ≤ 30 ms  Jitter ≤ 30 ms Mission-Critical Apps
 Loss ≤ 1%  Loss ≤ 1% Transactional/Interactive Apps
One-Way Requirements One-Way Requirements Bulk Data Apps
Best Effort Apps (Default)
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16. Why QoS in the Campus
Protect the Good and Punish the Bad
 QoS does more than just protect Voice and Video
 For "best-effort" traffic an implied "good faith" commitment that
there are at least some network resources available is assumed
 Need to identify and potentially punish out of profile traffic
(potential worms, DDOS, etc.)
 Scavenger class is an Internet-2 Draft Specification => CS1/CoS1
Access Distribution Core
Voice Voice
Data Data
Scavenger Scavenger
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17. Enabling QoS in the Campus
Layer 2 Classification: 802.1p, CoS
TAG
Pream. SFD DA SA Type 4 Bytes PT Data FCS
Ethernet Frame
Three Bits Used for CoS
(802.1p User Priority)
PRI CFI VLAN ID 802.1Q/p
Header
CoS Application
 802.1p user priority field also 7 Reserved
called Class of Service (CoS) 6 Reserved
 Different types of traffic are 5 Voice Bearer
assigned different CoS values 4 Video Conferencing*
 CoS six and seven are 3 Call Signaling
reserved for network use
2 High Priority Data
1 Medium Priority Data
* Including Audio and Video
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0 Best Effort Data
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18. Enabling QoS in the Campus
Layer 3 Classification: IP Precedence, DSCP
Version ToS
Length Byte Len ID Offset TTL Proto FCS IP SA IP DA Data
IPv4 Packet
7 6 5 4 3 2 1 0
IP Precedence Unused Standard IPv4
DiffServ Code Point (DSCP) Flow Ctrl DiffServ Extensions
 IPv4: three most significant bits of ToS byte are called IP precedence—
other bits unused by IP precedence
 DiffServ: six most significant bits of ToS byte are called Diff Serv Code
Point (DSCP)—remaining two bits used for flow control
 DSCP is backward-compatible with IP precedence
 DSCP values correspond to Per Hop Behavior (PHB) designations
 RFC 2474 provides more information on DSCP; also, see appendix in this
presentation
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19. IP Precedence and DSCP Compatibility
Compatibility with current IP precedence usage (RFC 1812)
Differentiates probability of timely forwarding:
(xyz000) >= (abc000) if xyz > abc
(that is, if a packet has DSCP value of 011000, it has a greater
probability of timely forwarding than a packet with DSCP value of
001000)
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20. Per-Hop Behaviors
 DSCP selects PHB throughout the network:
Default PHB (FIFO, tail drop)
EF PHB
AF PHB
Class-selector PHB (IP precedence)
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21. EF PHB
EF PHB:
Ensures a minimum departure rate
Guarantees bandwidth—class guaranteed an amount of bandwidth
with prioritized forwarding
Polices bandwidth—class not allowed to exceed the guaranteed
amount (excess traffic is dropped)
DSCP value of 101110: Looks like IP precedence 5 to non-DiffServ-
compliant devices:
Bits 5 to 7: 101 = 5 (same 3 bits are used for IP precedence)
Bits 3 and 4: 11 = No drop probability
Bit 2: Just 0
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22. AF PHB
AF PHB:
Guarantees bandwidth
Allows access to extra bandwidth, if available
Four standard classes: AF1, AF2, AF3, and AF4
DSCP value range of aaadd0:
aaa is a binary value of the class
dd is drop probability
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23. AF PHB (Cont.)
Each AF class uses three DSCP values.
Each AF class is independently forwarded with its guaranteed
bandwidth.
Congestion avoidance is used within each class to prevent
congestion within the class.
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24. AF PHB (Cont.)
Each AF class uses three DSCP values.
Each AF class is independently forwarded with its guaranteed
bandwidth.
Congestion avoidance is used within each class to prevent
congestion within the class.
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25. DSCP Summary
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26. Enabling QoS in the Campus
Classification and Marking Cisco Marking
Recommendations
L3 Classification L2
Application
IPP PHB DSCP CoS
Routing 6 CS6 48 6
Voice 5 EF 46 5
Video Conferencing 4 AF41 34 4
Streaming Video 4 CS4 32 4
Mission-Critical Data 3 AF31* 26 3
Call Signaling 3 CS3* 24 3
Transactional Data 2 AF21 18 2
Network Management 2 CS2 16 2
Bulk Data 1 AF11 10 1
Scavenger 1 CS1 8 1
Session ID Best Effort 0 0 0 0
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27. Enabling QoS in the Campus
Congestion Scenario: TCP Traffic Burst + VoIP
Core Instantaneous
Typical 4:1
Si Si Interface
Data Over- Congestion
Subscription
Distribution
Si Si
Typical 20:1
Data Over-
Subscription Access
= Data
= Voice
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28. Enabling QoS in the Campus
Congestion Scenario: Data + VoIP
IP Phone
Enclosure Phone
Voice Integrated
Max. 80 Kbps 3-Port Switch
P0
P P2 P1
Access
Switch Data
PC
Max. 100 Mbps
Potential
Congestion Points
During Data Traffic Bursts, Buffers Can Become
Congested, Causing Voice Packets to Be Dropped
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29. Enabling QoS in the Campus
Scheduling in IP Phones
IP Phone Enclosure P1 Untrusted:
P Trusted: Phone Switch
Phone Rewrites CoS = 0
Switch Accepts
incoming CoS Voice
CoS = 5 CoS = 5
P0
P P2 P1
Access Data
CoS = 0
Switch Priority Q
PC
Data Qs
 Voice media traffic is marked with CoS 5/ DSCP EF (high priority)
 Data traffic from the PC is remarked with CoS 0 (low priority) by
the IP phone switch; this occurs if PC tags frames as 802.1p/Q;
phone switch transparent if PC frames untagged
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30. Campus QoS Considerations
Establishing Trust Boundaries
Endpoints Access Distribution Core WAN Aggregators
1 Si Si
2
Si
3 Si
Trust Boundary
For scalability, classification should be done as close to the edge as possible
The outermost trusted devices represent the trust boundary
1 Optimal Trust Boundary: Trusted Endpoint
A device is trusted if it correctly classifies packets
2 Optimal Trust Boundary: Untrusted Endpoint
3 Suboptimal Trust Boundary
Only use if access switch cannot perform classification
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31. Network Infrastructure Agenda
 Building a Campus Network
 QoS in the Campus
 QoS in the WAN
 Qos in the Wireless LANs
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32. Enabling QoS in the WAN
Factors That Negatively Affect Packet-Based
Voice/Video
Delay
Loss Delay Variation
(Jitter)
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33. Types of Delay
Processing Delay: The time it takes for a router to take the packet from an input interface, examine it,
and put it into the output queue of the output interface
Queuing Delay: The time a packet resides in the output queue of a router
Serialization Delay: The time it takes to place the ―bits on the wire‖
Propagation Delay: The time it takes to transmit a packet
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34. Processing and Queuing Delay
Processing Delay: The time it takes for a router to take the packet from an input interface, examine it,
and put it into the output queue of the output interface
Queuing Delay: The time a packets resides in the output queue of a router
Serialization Delay: The time it takes to place the ―bits on the wire‖
Propagation Delay: The time it takes to transmit a packet
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35. Ways to Reduce Delay
Upgrade the link; the best solution but also the most expensive.
Forward the important packets first.
Compress the payload of Layer 2 frames (it takes time).
Compress IP packet headers.
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36. Packet Loss
Tail drops occur when the output queue is full. These are common drops, which
happen when a link is congested.
Many other types of drops exist, usually the result of router congestion, that are
uncommon and may require a hardware upgrade (input drop, ignore, overrun,
frame errors).
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37. Ways to Prevent Packet Loss
Upgrade the link; the best solution but also the most expensive.
Guarantee enough bandwidth to sensitive packets.
Prevent congestion by randomly dropping less important packets before
congestion occurs.
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38. Traffic Policing and Shaping Overview
These mechanisms must classify packets before policing or shaping the
traffic rate.
Traffic policing typically drops or marks excess traffic to stay within a
traffic rate limit.
Traffic shaping queues excess packets to stay within the desired traffic
rate.
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39. Traffic Policing and Shaping Overview
These mechanisms must classify packets before policing or shaping the
traffic rate.
Traffic policing typically drops or marks excess traffic to stay within a
traffic rate limit.
Traffic shaping queues excess packets to stay within the desired traffic
rate.
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40. Policing vs. Shaping
• Incoming and outgoing directions. • Outgoing direction only.
• Out-of-profile packets are dropped. • Out-of-profile packets are queued until
• Dropping causes TCP retransmits. a buffer gets full.
• Policing supports packet marking or • Buffering minimizes TCP retransmits.
re-marking. • Marking or re-marking not supported.
• Shaping supports interaction with
Frame Relay congestion indication.
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41. Enabling QoS in the WAN
Link Fragmentation and Interleaving (LFI)
Fragment-Size Recommendations
Fragmentation
Size Matrix
Serialization Delay Matrix (Based on 10-msec Delay)
64 128 256 512 1024 1500 PVC Frag
Bytes Bytes Bytes Bytes Bytes Bytes Speed Size
56 kbps 9 ms 18 ms 36 ms 72 ms 144 ms 214 ms 56 kbps 70 Bytes
64 kbps 8 ms 16 ms 32 ms 64 ms 128 ms 187 ms 64 kbps 80 Bytes
128 kbps 4 ms 8 ms 16 ms 32 ms 64 ms 93 ms 128 kbps 160 Bytes
256 kbps 2 ms 4 ms 8 ms 16 ms 32 ms 46 ms 256 kbps 320 Bytes
512 kbps 1 ms 2 ms 4 ms 8 ms 16 ms 23 ms 512 kbps 640 Bytes
640 768 kbps 1000 Bytes
X
768 kbps 1.2 ms 2.6 ms 5 ms 10 ms 15 ms
Used 1536 kbps 2000 Bytes
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42. Enabling QoS in the WAN
Scheduling in the WAN
PQ Packets Do not Go Through Fragmentation:
on Low-Link Speeds, You Cannot put Large
(i.e., Video) Packets in the PQ with Voice Packets
Therefore video traffic not recommended for link
speeds <768kbps
Low Latency Queuing Link Fragmentation
Police and Interleave
Voice
Video PQ
TX
Interleave Ring
Signaling
Packets Packets
In Out
Critical Data CBWFQ Fragment
WFQ Best Effort
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Layer 3 Queuing Subsystem
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Layer 2 Queuing Subsystem 42

43. How Many Classes of Service Do I Need?
Expanding the Number of Classes of Service over Time
4/5 Class Model 8 Class Model 11 Class Model
Voice Voice
Realtime Interactive-Video
Video Streaming Video
Call Signaling Call Signaling Call Signaling
IP Routing
Network Control
Network Management
Critical Data Mission-Critical Data
Critical Data
Transactional Data
Bulk Data Bulk Data
Best Effort Best Effort Best Effort
Scavenger Scavenger Scavenger
Time
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44. Enabling QoS in the WAN
Provisioning Bandwidth with Compressed RTP (cRTP)
VoIP Packet
Voice RTP UDP Link
IP Header
Payload Header Header Header
X Bytes 12 Bytes 8 Bytes 20 Bytes X Bytes
 Compresses RTP + UDP + IP
headers (40 bytes) down to cRTP
2–4 bytes Header
~2-4 Bytes
 Enabled on a per-link basis
ATM
PPP Frame-Relay
Codec 53 Bytes Cells with
6 Bytes of Header 4 Bytes of Header
a 48-Byte Payload
G.711 at 50 pps 68 kbps 85 kbps 67 kbps
G.711 at 33 pps 66 kbps 84 kbps 65.5 kbps
G.729A at 50 pps 12 kbps 21.2 kbps 11.2 kbps
G.729A at 33 pps 10.5 kbps 14 kbps 10 kbps
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45. Enabling QoS in the WAN
A Day in the Life of a VoIP Packet: Without cRTP
Assumption:
G.729, 20-ms Sample Payload
(20)
Payload = 20 Bytes
Frame
Relay
Packet 78 78
Size (Bytes)
64
60 Enet (14) Enet (14) 60
802.1Q (4) F/R (4) 802.1Q (4)
IP (20) IP (20) IP (20) IP (20) IP (20)
20 UDP (8) UDP (8) UDP (8) UDP (8) UDP (8) 20
RTP (12) RTP (12) RTP (12) RTP (12) RTP (12)
Payload Payload Payload Payload Payload Payload Payload
(20) (20) (20) (20) (20) (20) (20)
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46. Enabling QoS in the WAN
A Day in the Life of a VoIP Packet: With cRTP
Assumption:
Payload cRTP Is not Free!
G.729, 20-ms Sample Watch for CPU on
(20)
Payload = 20 Bytes WAN Edge Routers!!!
Frame
Relay
Packet 78 cRTP Is 78
Size (Bytes) Point to
Enet (14) Point Enet (14) 60
60
802.1Q (4) 28 802.1Q (4)
IP (20) IP (20) IP (20) IP (20)
20 UDP (8) UDP (8) UDP (8) UDP (8) 20
F/R (4)
RTP (12) RTP (12) cRTP (4)
RTP (12) RTP (12)
Payload Payload Payload Payload Payload Payload Payload
(20) (20) (20) (20) (20) (20) (20)
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47. Network Infrastructure Agenda
 Building a Campus Network
 QoS in the Campus
 QoS in the WAN
 Qos in the Wireless LANs
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48. WLAN and LAN
 Wireless LAN (WLAN) as an extension to wired LAN
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49. WLAN QoS Queuing Overview
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50. WLAN QoS RF Backoff Timing
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51. WLAN QoS Queuing Overview
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52. What We Have Built So Far
Si
IP WAN
Si Branch Access
WAN Router Switch Branch
Access Distribution/
Aggregation
Campus
Switch Core Switch Router Network Infrastructure
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53. Session ID
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