IP Transmission Technologies

1
IP Transmission Technologies
2
Hourglass of TCP/IP Protocols
3
Transmission Technologies

• Ethernet (LAN)
• Copper
• Fiber
• Wireless
• Satellite DVB-RCS
• Point-to-point Leased Line
• E1, SDH, DSL,...
• Packet-switched
• X.25, Frame Relay
• ATM
• MPLS
• QoS

4
Types of Point to Point Protocols

• SLIP over async
• Very simple
• IP only
• Unreliable - no checksum
• HDLC over sync
• various proprietary versions
• frames have checksum
• PPP

5
Leased Line
V.35
V.35
6
PPP

• SLIP done right
• Used for synchronous and asynchronous
  transmission
• Extended negotiation mechanism
• Multiple protocol support

7
PPP and OSI model
Network Layer
IPCP IPXCP others
PPP
Network Control Protocol
Data Link Layer
LCP - Link Control Protocol
Synchronous or Asynchronous Physical Media
Physical Layer
8
LCP Configuration Options
9
PAP/CHAP

• PAP
• Password required
• Unencrypted password sent via the link
• Allows storage of encrypted passwords
• CHAP
• Challenge handshake
• No passwords sent via the link
• Need for storing unencrypted secrets

10
Selecting a PPP Authentication Protocol
PAP 2-Way Handshake
Remote Router (SantaCruz)
Central-Site Router (HQ)
"santacruz, boardwalk"
Accept/Reject
Hostname santacruz Password boardwalk
username santacruz password boardwalk

• Passwords sent in cleartext
• Peer in control of attempts

11
Selecting a PPP Authentication Protocol
CHAP 3-Way Handshake
Remote Router (SantaCruz)
Central-Site Router (HQ)
Challenge
Response
Accept/Reject
Hostname santacruz Password boardwalk
username santacruz password boardwalk

• Use secret known only to authenticator and peer

12
Multilink PPP

• Combining physical links into one logical bundle
• Result higher speed and lower latency
• MPPP / Bonding
• MPPP assembles/disassembles frames on the Data
  Link Layer
• MPPP used for synchronous and asynchronous
  physical links
• Bonding assembles/disassembles on the bit level

13
Show ppp multilink
14
X.25
15
X.25

• 1970s
• Data Terminal Equipment (DTE)
• Data Circuit-terminating Equipment (DCE)
• Packet Switching Exchange (PSE)
• DCE provides clock

16
X.25 topology
17
Packet Assembler/Disassembler
18
X.25 Stack
19
LAPB Frame
20
X.25 Data Link Control

• Point to point full duplex data links
• Correction of errors and congestion control
• Encapsulation of data in variable length frames
  delimited by flags
• Redundant error correction bits
• Sliding window (8 or 128 frames)

21
X.121 address
22
X.121 address

• Data Network Identification Code (DNIC)
• National Terminal Number (NTN)

23
Packet Level Protocol

• Several circuits multiplexed
• Sliding window error and congestion control for
  every VC
• Call restriction, charging, QoS, ...

24
VC Setup

• PVC permanent entry in routing table (static),
  substitute to leased lines
• SVC dynamic entry in routing table triggered
  by an open packet and torn down by close
  packet

25
Frame Relay
26
Characteristics

• Introduced in 1984 but only (significantly)
  deployed in the late 1980s
• L1 and 2
• Packet Switched technology PVCs and SVCs
• Connection-oriented data link layer communication
• X.25 lite

27
Differences with X.25

• Less robust
• Assumes more reliable medium gt
• No retransmission of lost data
• No windowing
• Error control handled by higher layers
• Higher performance and transmission efficiency

28
Frame Relay Topology
29
DLCI

• Data Link Connection Identifier
• Uniquely identify circuits
• Assigned by service provider
• Local significance only (except with LMI)

30
DLCI
31
Frame Format
32
CIR

• What you buy with a FR connection
• Committed Information Rate
• CIR Committed Burst/Committed Time
• Also Maximum Rate

33
Frame Relay
s0.1-DLCI110
s0.2-DLCI110
s0.3-DLCI130
RTR1
s0.3-DLCI120
s0.2-DLCI130
s0.1-DLCI120
34
ATM

• Asynchronous Transfer Mode

35
Characteristics

• Originally designed to transmit voice, video and
  data over the same network
• Cell switching
• Each communication is assigned a timeslot
• Timeslots are assigned on a demand-basis gt
  asynchronous (as opposed to TDM)

36
Cells

• 53 bytes 5 byte header 48 byte payload
• Tradeoff between voice world and data world
• Voice needs small payloads and low delay
• Data needs big payload and less overhead

37
ATM
38
ATM Adaptation Layer (AAL)

• Together with ATM layer, equivalent to Data Link
  layer in OSI model
• AAL1 Connection Oriented gt Voice and Video
• AAL 3,4 Connection Oriented and Connectionless
  (similar to SMDS)
• AAL 5 Connection Oriented and Connectionless for
  CLIP and LANE

39
ATM AAL5
40
ATM Sources
41
ATM Addresses

• ITU-T Standard E.164 (Telephone )
• ATM Forum defined 20-byte NSAP Addresses for use
  in private networks
• E.164 address used as prefix on NSAP
• Mapped to IP addresses by ATM ARP (in CLIP)

42
ATM QoS

• Traffic Contract peak bandwidth, average
  sustained bandwidth, burst size , Similar to FR
• Traffic Shaping (end device) Queuing, Buffering
• Traffic Policing (switches) Enforces contract

43
Path Establishment
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
MPLS Terminology

• LDP Label Distribution Protocol
• LSP Label Switched Path
• FEC Forwarding Equivalence Class
• LSR Label Switching Router
• LER Label Edge Router

49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53
MPLS HOW DOES IT WORK ?
TIME
54
MPLS BUILT ON STANDARD IP
47.1
1
2
1
3
2
1
47.2
3
47.3
2

• Destination based forwarding tables as built by
  OSPF, RIP, etc.

55
MPLS Label Distribution
1
47.1
3
2
3
1
1
2
47.3
3
47.2
2
56
MPLS VPNs
Layer 3 VPNs BGP/MPLS VPNs (RFC 2547 bis)
Layer 2 VPNs AToM (Any Transport over MPLS)
57
Layer 2 Vs. Layer 3 VPNs

• Depending on the type of customer payload, a VPN
  can be classified as L2 or L3 VPNs
• Examples of L2VPN
• ATM LAN Emulation (LANE),
• Ethernet over MPLS (Idraft-Martini,
  Idraft-KKompella, VPLS Idraft-Lasserre-VKompella,
  IPLS Idraft-Shah)
• Examples of L3VPN
• RFC 1577 Classical IP over ATM
• IPSec Tunneling mode
• RFC 2547 BGP/MPLS-based VPNs
• Idraft-Declercq BGP/IPSec VPNs
• Idraft-Knight Virtual Router Based VPNs

58
Encapsulation of Customer Ethernet Frames in a L2
PPVPN
Untagged or Tagged ?? Ethernet ?? Untagged
or TaggedCustomer Ethernet over MPLS
Customer Ethernet Frames
over Ethernet Frames
User Enet
User Enet
User Enet
User Enet
User Enet
User Enet
VLAN
VLAN
VLAN
VLAN
VLAN
VLAN
MPLS
MPLS
OR
Enet
Enet
User Enet
User Enet
User Enet
User Enet
User Enet
User Enet
MPLS
MPLS
VC Label
Enet
Enet
Tunnel Label
Provider Network Supporting L2PPVPN
Customer or Other Ethernet Access Network
Customer or Other Ethernet Access Network
MPLS-Domain
Single Customer VLAN Domain
59
Example of a L2 PPVPN (VPLS)
802.1q VLANs
802.1q VLANs
Provider Network
Customer LAN switch
Customer A L2 Network, e.g. Ethernet
Customer B L2 Network, e.g. Ethernet
MPLS LSP MESH
2 MPLS LABELS per frame Tunnel Label Outer
Label for delivery to dest. PE VC Label Inner
Label to identify L2VPN end-pts
Customer A L2 Network, e.g. Ethernet
Customer B L2 Network, e.g. Ethernet
Ethernet Frames with or without VLAN tags
60
Example of a L3 PPVPN (RFC2547bis)
Provider Network
Customer Edge Router
Customer A Network
Customer B Network
MPLS LSP MESH
2 MPLS LABELS per frame Tunnel Label Outer
Label for delivery to dest. PE VC Label Inner
Label to identify L2VPN end-pts
Customer A Network
Customer B Network
Customer IP packets carrying possibly Private IP
addresses
61
Ethernet over MPLS
Point to Point, Metro Ethernet Service
ISP C
MPLS Network
ISP A
Enterprise LAN
ISP B
PE
PE
ISP 2
PE
PE
ISP 1
PE
PE
Enterprise LAN
ISP 3
Distributed NAP
Based on draft-martini VCs to VLANs gt VCid maps
to VLAN id
62
Ethernet 802.1q VLAN Transport
Interface GigabitEthernet0/0.2 encapsulation
dot1q 41 mpls l2transport route 1.0.0.8 312
ltsequencinggt ! Interface GigabitEthernet1/0.2
encapsulation dot1q 56 mpls l2transport route
1.0.0.8 313 ltsequencinggt
VLAN 56
MPLS
Customer Site
PE1 1.0.0.8
PE1 1.0.0.4
VLAN 41
VLAN 41
VLAN 56
Customer Site
Customer Site
Customer Site
802.1q to 802.1q VLAN Transport
63
AToM - MTU Considerations
Ingress PE checks Egress PE outbound interface
MTU AND egress interface into MPLS backbone
Customer Site
Customer Site
Egress MTU Signalled using LDP
PE1
PE2
PDU
NO mechanism to check backbone MTU
Incoming PDU dropped if MTU exceeded
Provider MUST dictate MTU or direct traffic away
from low MTU links
64
(No Transcript)
65
(No Transcript)
66
(No Transcript)
67
IETF DiffServ Architecture (RFC-2475)

• The idea different service levels for packets
• The service some significant characteristics of
  packet transmission in one direction across the
  network
• Examples bandwidth and latency

68
Type-of-Service (RFC791)
Precedence
Unused
D
T
R
Version
Length
Total Length
ToS Field

8
0
15
31
0 1
D Normal Delay Low Delay
T Normal Throughput High Throughput
R Normal Reliability High Reliability
69
IP Precedence Values
111 Network Control
110 Internetwork Control
101 Critical
100 Flash Override
011 Flash
010 Immediate
001 Priority
000 Routine
70
Network-Layer BWM

• Bandwidth Management functions
• classification, shaping
• discarding, queuing

71
Queuing Disciplines

• First-In-First-Out (FIFO)
• no classes
• fast, easy to implement
• Priority Queuing
• all traffic in a high-priority class is sent
  before any in a lower priority one
• Class-based Queuing (CBQ)
• a number of bytes is sent from each class before
  going to the next class

72
Priority Queuing
73
Class-Based Queuing
74
Queuing Disciplines (cont.)

• Weighted Fair Queuing
• traffic is divided into a number of flows
• each flow is given a share of the traffic (based
  on its weight)
• small packets are given priority over large ones
  (interactive and control traffic gets more
  priority)

75
Weighted Fair Queuing
76
Token Bucket Model
Token Bucket characterizes traffic source

• Token Bucket main parameters
• Token Arrival Rate - v
• Bucket Depth - Bc
• Time Interval tc
• Link Capacity - C

tc Bc/v
77
Excess Burst (Be)Cisco Implementation

• CAR
• allows RED like behavior
• traffic fitting into Bc always conforms
• traffic fitting into Be conforms with probability
  proportional to amount of tokens left in the
  bucket
• traffic not fitting into Be always exceedsCAR
  uses the following parameters
• ?t time period since the last packet arrival
• Current Debt (Dcur) Amount of debt during
  current time interval
• Compound Debt (Dcomp) Sum of all Dcur since the
  last drop
• Actual Debt (Dact) Amount of tokens currently
  borrowed

78
Excess Burst (Be)Cisco Implementation
Packet of lengthL arrived
CAR Algorithm
ConformAction
Y
Bccur L gt 0
Bccur Bccur L
N
Dcur L - Bccur Bccur 0 Dcomp Dcomp
Dcur Dact Dact Dcur v?t
Y
ExceedAction
Dact gt Be
N
Y
Dcomp 0
Dcomp gt Be
N
79
Policing Configuration Sample
CAR Based
ip cef interface serial 2/1 ip unnumbered
loopback 0 rate-limit output access-group 100
64000 8000 16000 conform-action transmit
excess-action drop ! interface serial 2/2 ip
unnumbered loopback 0 rate-limit input 128000
16000 32000 conform-action transmit
excess-action drop ! access-list 100 permit tcp
host 10.0.0.1 any eq http
80
Random Early Detection (RED)
Developed by Van Jacobson in 1993

• Starts randomly dropping packets before actual
  congestion occurs
• Keeps average queue depth low
• Increases average throughput

81
Cisco AutoQoS Framework MLPPP Link
Fragmentation Interleaving
Problem large packets freeze out voice
Voice Packet 60 bytes Every 20 ms
Voice Packet 60 bytes Every gt214 ms
Voice Packet 60 bytes Every gt214 ms
214ms Serialization Delay
Voice
1500 Data Bytes
Voice
Voice
1500 Data Bytes
Voice
Voice
1500 Data Bytes
Voice
10mbps Ethernet
10mbps Ethernet

• Implemented via Multilink PPP (MLP) over FR, ATM,
  and leased lines
• Fragments are interleaved with the real-time
  packets, reducing the Serialization delay
  experienced by Voice packets

Benefit reduce the jitter in voice calls
82
Link Fragmentation and Interleaving (LFI)
For links lt 128kbps
83
Link Fragmentation and Interleaving (LFI)

• Supported interfaces
• Multilink PPP
• Frame Relay DLCI
• ATM VC

84
LFI Configuration Sample
MLP version
interface virtual-template 1 ip unnumbered
loopback 0 ppp multilink ppp multilink
interleave ppp multilink fragment-delay 30 ip
rtp interleave 16384 1024 512
85
FR Fragmentation and Prioritization
interface Serial0/0 mtu 1600 encapsulation
frame-relay frame-relay fragment 160 end-to-end
frame-relay interface-queue priority ! interface
Serial0/0.116 point-to-point ip unnumbered
Loopback0 frame-relay interface-dlci 116
class HI ! map-class frame-relay HI frame-relay
interface-queue priority high ! map-class
frame-relay LO frame-relay interface-queue
priority low